135 MHz BW IF Diversity Receiver AD6679 Data Sheet FEATURES APPLICATIONS Parallel LVDS (DDR) outputs In-band SFDR = 82 dBFS at 340 MHz (500 MSPS) In-band SNR = 67.8 dBFS at 340 MHz (500 MSPS) 1.1 W total power per channel at 500 MSPS (default settings) Noise density = −153 dBFS/Hz at 500 MSPS 1.25 V, 2.50 V, and 3.3 V dc supply operation Flexible input range 1.46 V p-p to 2.06 V p-p (2.06 V p-p nominal) 95 dB channel isolation/crosstalk Amplitude detect bits for efficient automatic gain control (AGC) implementation Noise shaping requantizer (NSR) option for main receiver function Variable dynamic range (VDR) option for digital predistortion (DPD) function 2 integrated wideband digital processors per channel 12-bit numerically controlled oscillator (NCO), up to 4 cascaded half-band filters Differential clock inputs Integer clock divide by 1, 2, 4, or 8 Energy saving power-down modes Small signal dither Diversity multiband, multimode digital receivers 3G/4G, TD-SCDMA, W-CDMA, GSM, LTE, LTE-A DOCSIS 3.0 CMTS upstream receive paths HFC digital reverse path receivers GENERAL DESCRIPTION The AD6679 is a 135 MHz bandwidth mixed-signal intermediate frequency (IF) receiver. It consists of two, 14-bit, 500 MSPS analog-to-digital converters (ADCs) and various digital signal processing blocks consisting of four wideband DDCs, an NSR, and VDR monitoring. It has an on-chip buffer and a sample-andhold circuit designed for low power, small size, and ease of use. This product is designed to support communications applications capable of sampling wide bandwidth analog signals of up to 2 GHz. The AD6679 is optimized for wide input bandwidth, high sampling rates, excellent linearity, and low power in a small package. The dual ADC cores feature a multistage, differential pipelined architecture with integrated output error correction logic. Each ADC features wide bandwidth inputs supporting a variety of user-selectable input ranges. An integrated voltage reference eases design considerations. FUNCTIONAL BLOCK DIAGRAM AVDD1 (1.25V) AVDD2 (2.50V) AVDD3 (3.3V) DVDD (1.25V) DRVDD (1.25V) SPIVDD (1.22V TO 3.4V) BUFFER VIN+A SIGNAL PROCESSING ADC VIN–A DIGITAL DOWNCONVERSION (×4) FD_A SIGNAL MONITOR FAST DETECT FD_B DATA ROUTER MUX 16 LVDS OUTPUT STAGING NOISE SHAPING REQUANTIZER (×2) LVDS OUTPUTS V_1P0 BUFFER VARIABLE DYNAMIC RANGE (×2) VIN+B ADC D0± D1± D2± D3± D4± D5± D6± D7± D8± D9± D10± D11± D12± D13± DCO± STATUS± VIN–B CLK– FAST DETECT CLOCK GENERATION AND ADJUST CLK+ AD6679 ÷2 SPI CONTROL ÷4 SIGNAL MONITOR PDWN/STBY AGND SYNC± SDIO SCLK CSB DGND DRGND 13059-001 ÷8 Figure 1. Rev. B Document Feedback Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. 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Technical Support www.analog.com AD6679 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 General Description ................................................................... 46 Applications ....................................................................................... 1 DDC NCO Plus Mixer Loss and SFDR ................................... 47 General Description ......................................................................... 1 Numerically Controlled Oscillator .......................................... 47 Functional Block Diagram .............................................................. 1 FIR Filters ........................................................................................ 49 Revision History ............................................................................... 3 Overview ..................................................................................... 49 Product Highlights ........................................................................... 4 Half-Band Filters ........................................................................ 49 Specifications..................................................................................... 5 DDC Gain Stage ......................................................................... 51 DC Specifications ......................................................................... 5 DDC Complex to Real Conversion ......................................... 51 AC Specifications.......................................................................... 6 DDC Example Configurations ................................................. 52 Digital Specifications ................................................................... 7 Noise Shaping Requantizer (NSR) ............................................... 56 Switching Specifications .............................................................. 8 Decimating Half-Band Filter .................................................... 56 Timing Specifications .................................................................. 9 NSR Overview ............................................................................ 56 Absolute Maximum Ratings .......................................................... 18 Variable Dynamic Range (VDR) .................................................. 59 Thermal Characteristics ............................................................ 18 VDR Real Mode.......................................................................... 60 ESD Caution ................................................................................ 18 VDR Complex Mode ................................................................. 60 Pin Configurations and Function Descriptions ......................... 19 Digital Outputs ............................................................................... 62 Typical Performance Characteristics ........................................... 25 Timing.......................................................................................... 62 Equivalent Circuits ......................................................................... 28 Data Clock Output ..................................................................... 62 Theory of Operation ...................................................................... 30 ADC Overrange .......................................................................... 62 ADC Architecture ...................................................................... 30 Multichip Synchronization............................................................ 64 Analog Input Considerations.................................................... 30 SYNC± Setup and Hold Window Monitor ............................. 65 Voltage Reference ....................................................................... 32 Test Modes ....................................................................................... 67 Clock Input Considerations ...................................................... 33 ADC Test Modes ........................................................................ 67 Power-Down/Standby Mode..................................................... 35 Serial Port Interface (SPI) .............................................................. 68 Temperature Diode .................................................................... 35 Configuration Using the SPI ..................................................... 68 Virtual Converter Mapping ........................................................... 36 Hardware Interface ..................................................................... 68 ADC Overrange and Fast Detect .................................................. 38 SPI Accessible Features .............................................................. 68 ADC Overrange (OR) ................................................................ 38 Memory Map .................................................................................. 69 Fast Threshold Detection (FD_A and FD_B) ........................ 38 Reading the Memory Map Register Table............................... 69 Signal Monitor ................................................................................ 39 Memory Map Register Table ..................................................... 70 Digital Downconverter (DDC) ..................................................... 40 Applications Information .............................................................. 80 DDC I/Q Input Selection .......................................................... 40 Power Supply Recommendations............................................. 80 DDC I/Q Output Selection ....................................................... 40 Outline Dimensions ....................................................................... 81 DDC General Description ........................................................ 40 Ordering Guide .......................................................................... 81 Frequency Translation ................................................................... 46 Rev. B | Page 2 of 81 Data Sheet AD6679 REVISION HISTORY 4/16—Rev. A to Rev. B Changes to Table 4 ............................................................................ 8 Changes to Table 5 and Figure 3 ..................................................... 9 Changes to Figure 4 Caption .........................................................10 Changes to Figure 5 Caption .........................................................11 Changes to Figure 6 Caption .........................................................12 Changes to Figure 7 Caption .........................................................13 Changes to Figure 8 Caption .........................................................14 Changes to Figure 10 ......................................................................16 Changes to Table 6 ..........................................................................18 Changes to Input Clock Divider Section .....................................34 Added Virtual Converter Mapping Section and Table 12; Renumbered Sequentially ..............................................................36 Added Figure 60; Renumbered Sequentially ...............................37 Changes to Table 35 ........................................................................62 Changes to Datapath Soft Reset Section ......................................69 Changes to Table 41 ........................................................................70 9/15—Rev. 0 to Rev. A Changes to General Description Section ....................................... 3 Changes to Figure 12 ...................................................................... 18 Changes to Figure 13 ...................................................................... 20 Changes to Figure 14 ...................................................................... 22 Changes to ADC Test Modes......................................................... 63 5/15—Revision 0: Initial Version Rev. B | Page 3 of 81 AD6679 Data Sheet The analog input and clock signals are differential inputs. The ADC data outputs are internally connected to four DDCs through a crossbar mux. Each DDC consists of up to five cascaded signal processing stages: a 12-bit frequency translator (NCO) and up to four half-band decimation filters. Each ADC output is connected internally to an NSR block. The integrated NSR circuitry allows improved SNR performance in a smaller frequency band within the Nyquist bandwidth. The device supports two different output modes, selectable via the serial port interface (SPI). With the NSR feature enabled, the outputs of the ADCs are processed such that the AD6679 supports enhanced SNR performance within a limited portion of the Nyquist bandwidth while maintaining a 9-bit output resolution. incoming signal power using the fast detect control bits in Register 0x245 of the ADC. If the input signal level exceeds the programmable threshold, the fast detect indicator goes high. Because this threshold indicator has low latency, the user can quickly reduce the system gain to avoid an overrange condition at the ADC input. In addition to the fast detect outputs, the AD6679 also offers signal monitoring capability. The signal monitoring block provides additional information about the signal that the ADC digitized. The output data is routed directly to the one external 14-bit LVDS output port, supporting double data rate (DDR) formatting. An external data clock and a clock status bit are offered for data capture flexibility. Each ADC output is also connected internally to a VDR block. This optional mode allows full dynamic range for defined input signals. Inputs that are within a defined mask (based on DPD applications) pass unaltered. Inputs that violate this defined mask result in the reduction of the output resolution. The AD6679 has flexible power-down options that allow significant power savings when desired. All of these features can be programmed using a 1.8 V capable 3-wire SPI. With VDR, the dynamic range of the observation receiver is determined by a defined input frequency mask. For signals falling within the mask, the outputs are presented at the maximum resolution allowed. For signals exceeding defined power levels within this frequency mask, the output resolution is truncated. This mask is based on DPD applications and supports tunable real IF sampling, and zero IF or complex IF receive architectures. PRODUCT HIGHLIGHTS Operation of the AD6679 between the DDC, NSR, and VDR modes is selectable via SPI-programmable profiles. The AD6679 is available in a Pb-free, 196-ball BGA_ED, and is specified over the −40°C to +85°C industrial temperature range. 1. 2. 3. 4. 5. In addition to the DDC blocks, the AD6679 has several functions that simplify the AGC function in a communications receiver. The programmable threshold detector allows monitoring of the 6. 7. Rev. B | Page 4 of 81 Wide full power bandwidth IF sampling of signals up to 2 GHz. Buffered inputs with programmable input termination eases filter design and implementation. Four integrated wideband decimation filters and NCO blocks support multiband receivers. Flexible SPI controls various product features and functions to meet specific system requirements. Programmable fast overrange detection and signal monitoring. Programmable fast overrange detection. 12 mm × 12 mm, 196-ball BGA_ED. Data Sheet AD6679 SPECIFICATIONS DC SPECIFICATIONS AVDD1 = 1.25 V, AVDD2 = 2.50 V, AVDD3 = 3.3 V, DVDD = 1.25 V, DRVDD = 1.25 V, SPIVDD = 1.8 V, specified maximum sampling rate, 1.0 V internal reference (VREF), AIN = −1.0 dBFS, clock divider = 2, default SPI settings, unless otherwise noted. Table 1. Parameter RESOLUTION ACCURACY No Missing Codes Offset Error Offset Matching Gain Error Gain Matching Differential Nonlinearity (DNL) Integral Nonlinearity (INL) TEMPERATURE DRIFT Offset Error Gain Error INTERNAL VOLTAGE REFERENCE Voltage INPUT REFERRED NOISE VREF = 1.0 V ANALOG INPUTS Differential Input Voltage Range (Internal VREF = 1.0 V) Common-Mode Voltage (VCM) Differential Input Capacitance1 Analog Full Power Bandwidth POWER SUPPLY AVDD1 AVDD2 AVDD3 DVDD DRVDD SPIVDD IAVDD1 IAVDD2 IAVDD32 IDVDD (Default SPI—NSR Mode) IDVDD (VDR Mode) IDRVDD3 ISPIVDD POWER CONSUMPTION Total Power Dissipation Default SPI—NSR Mode3 VDR Mode3 Power-Down Dissipation Standby4 Temperature Full Full Full Full Full Full Full Min 14 −0.3 −6.5 −0.6 −4.5 Typ Max Guaranteed 0 +0.3 0 0.3 0 +6.5 0 5.0 ±0.5 +0.7 ±2.5 +5.0 Unit Bits % FSR % FSR % FSR % FSR LSB LSB Full Full ±3 −39 ppm/°C ppm/°C Full 1.0 V 25°C 2.04 LSB rms Full Full Full Full 1.46 2.06 2.05 1.5 2 2.06 V p-p V pF GHz Full Full Full Full Full Full Full Full Full Full Full Full Full 1.22 2.44 3.2 1.22 1.22 1.22 1.25 2.50 3.3 1.25 1.25 1.8 464 396 89 141 117 110 5 1.28 2.56 3.4 1.28 1.28 3.4 503 455 100 164 138 123 6 V V V V V V mA mA mA mA mA mA mA 2.2 2.16 0.71 1.4 2.37 2.34 W W W W Full Full Full Full 1 Differential capacitance is measured between the VIN+x and VIN−x pins (x = A, B). AVDD3 current changes based on the Buffer Control 1 setting (see Figure 46). Parallel interleaved LVDS mode. The power dissipation on DRVDD changes with the output data mode used. 4 Standby can be controlled by the SPI. 2 3 Rev. B | Page 5 of 81 AD6679 Data Sheet AC SPECIFICATIONS AVDD1 = 1.25 V, AVDD2 = 2.50 V, AVDD3 = 3.3 V, DVDD = 1.25 V, DRVDD = 1.25 V, SPIVDD = 1.8 V, specified maximum sampling rate, 1.0 V internal reference, AIN = −1.0 dBFS, clock divider = 2, default SPI settings, unless otherwise noted. Table 2. Parameter 1 ANALOG INPUT FULL SCALE NOISE DENSITY 2 SIGNAL-TO-NOISE RATIO (SNR) 3 VDR Mode (Input Mask Not Triggered) fIN = 10 MHz fIN = 170 MHz fIN = 340 MHz fIN = 450 MHz fIN = 765 MHz fIN = 985 MHz fIN = 1950 MHz NSR Enabled (21% Bandwidth (BW) Mode) fIN = 10 MHz fIN = 170 MHz fIN = 340 MHz fIN = 450 MHz fIN = 765 MHz fIN = 985 MHz fIN = 1950 MHz NSR Enabled (28% BW Mode) fIN = 10 MHz fIN = 170 MHz fIN = 340 MHz fIN = 450 MHz fIN = 765 MHz fIN = 985 MHz fIN = 1950 MHz SIGNAL-TO-NOISE-AND-DISTORTION RATIO (SINAD)3 VDR Mode (Input Mask Not Triggered) fIN = 10 MHz fIN = 170 MHz fIN = 340 MHz fIN = 450 MHz fIN = 765 MHz fIN = 985 MHz fIN = 1950 MHz EFFECTIVE NUMBER OF BITS (ENOB)3 VDR Mode (Input Mask Not Triggered) fIN = 10 MHz fIN = 170 MHz fIN = 340 MHz fIN = 450 MHz fIN = 765 MHz fIN = 985 MHz fIN = 1950 MHz Temperature Full Full 2.06 −153 Unit V p-p dBFS/Hz 68.9 68.6 67.8 67.3 63.9 62.8 59.0 dBFS dBFS dBFS dBFS dBFS dBFS dBFS 25°C 25°C 25°C 25°C 25°C 25°C 25°C 75.0 74.8 74.0 73.1 69.7 68.1 64.6 dBFS dBFS dBFS dBFS dBFS dBFS dBFS 25°C 25°C 25°C 25°C 25°C 25°C 25°C 72.4 72.3 71.6 71.0 67.7 66.8 63.1 dBFS dBFS dBFS dBFS dBFS dBFS dBFS 68.7 68.5 67.6 67.2 63.8 62.5 58.3 dBFS dBFS dBFS dBFS dBFS dBFS dBFS 11.1 10.9 10.8 10.8 10.3 10.1 9.5 Bits Bits Bits Bits Bits Bits Bits 25°C Full 25°C 25°C 25°C 25°C 25°C 25°C Full 25°C 25°C 25°C 25°C 25°C 25°C Full 25°C 25°C 25°C 25°C 25°C Rev. B | Page 6 of 81 Min 67.5 67 10.8 Typ Max Data Sheet AD6679 Parameter 1 SPURIOUS FREE DYNAMIC RANGE (SFDR), SECOND OR THIRD HARMONIC3 VDR Mode (Input Mask Not Triggered) fIN = 10 MHz fIN = 170 MHz fIN = 340 MHz fIN = 450 MHz fIN = 765 MHz fIN = 985 MHz fIN = 1950 MHz WORST OTHER (EXCLUDING SECOND OR THIRD HARMONIC)3 VDR Mode (Input Mask Not Triggered) fIN = 10 MHz fIN = 170 MHz fIN = 340 MHz fIN = 450 MHz fIN = 765 MHz fIN = 985 MHz fIN = 1950 MHz TWO-TONE INTERMODULATION DISTORTION (IMD)3, AIN1 AND AIN2 = −7.0 dBFS fIN1 = 185 MHz, fIN2 = 188 MHz fIN1 = 338 MHz, fIN2 = 341 MHz CROSSTALK 4 FULL POWER BANDWIDTH Temperature 25°C Full 25°C 25°C 25°C 25°C 25°C Min Typ Unit Max 83 85 82 86 81 76 69 dBFS dBFS dBFS dBFS dBFS dBFS dBFS 25°C Full 25°C 25°C 25°C 25°C 25°C −93 −94 −90 −92 −89 −89 −85 dBFS dBFS dBFS dBFS dBFS dBFS dBFS 25°C 25°C 25°C 25°C −88 −87 95 2 dBFS dBFS dB GHz 76 See the AN-835 Application Note, Understanding High Speed ADC Testing and Evaluation, for definitions and for details on how these tests were completed. Noise density is measured at a low analog input frequency (30 MHz). 3 See Table 11 for the recommended settings for full-scale voltage and buffer control settings. 4 Crosstalk is measured at 185 MHz with a −1.0 dBFS analog input on one channel and no input on the adjacent channel. 1 2 DIGITAL SPECIFICATIONS AVDD1 = 1.25 V, AVDD2 = 2.50 V, AVDD3 = 3.3 V, DVDD = 1.25 V, DRVDD = 1.25 V, SPIVDD = 1.8 V, specified maximum sampling rate, 1.0 V internal reference, AIN = −1.0 dBFS, clock divider = 2, default SPI settings, unless otherwise noted. Table 3. Parameter CLOCK INPUTS (CLK+, CLK−) Logic Compliance Differential Input Voltage Input Common-Mode Voltage Input Resistance (Differential) Input Capacitance SYSTEM REFERENCE INPUTS (SYNC+, SYNC−) Logic Compliance Differential Input Voltage Input Common-Mode Voltage Input Resistance (Differential) Input Capacitance (Differential) LOGIC INPUTS (SDIO, SCLK, CSB, PDWN/STBY) Logic Compliance Logic 1 Voltage Logic 0 Voltage Input Resistance Temperature Full Full Full Full Full Full Full Full Full Full Full Full Full Full Rev. B | Page 7 of 81 Min 600 Typ LVDS/LVPECL 1200 0.85 35 Max Unit 1800 mV p-p V kΩ pF 2.5 400 0.6 LVDS/LVPECL 1200 0.85 35 1800 2.0 2.5 0 CMOS 0.8 × SPIVDD 0.2 × SPIVDD 30 mV p-p V kΩ pF V V kΩ AD6679 Parameter LOGIC OUTPUT (SDIO) Logic Compliance Logic 1 Voltage (IOH = 800 µA) Logic 0 Voltage (IOL = 50 µA) LOGIC OUTPUTS (FD_A, FD_B) Logic Compliance Logic 1 Voltage Logic 0 Voltage Input Resistance DIGITAL OUTPUTS (D0± to D13±, A Dx/Dy± and B Dx/Dy±, DATA0± to DATA7±, DCO±, OVR±, FCO±, and STATUS±) Logic Compliance ANSI Mode Differential Output Voltage (VOD) Output Offset Voltage (VOS) Reduced Swing Mode Differential Output Voltage (VOD) Output Offset Voltage (VOS) Data Sheet Temperature Min Full Full Full Full Full Full Full 0.8 0 Typ Max Unit CMOS 0.8 × SPIVDD 0.2 × SPIVDD V V CMOS SPIVDD 0 30 V V kΩ Full LVDS Full Full 230 0.58 350 0.70 430 0.85 mV V Full Full 120 0.59 200 0.70 235 0.83 mV V SWITCHING SPECIFICATIONS AVDD1 = 1.25 V, AVDD2 = 2.50 V, AVDD3 = 3.3 V, DVDD = 1.25 V, DRVDD = 1.25 V, SPIVDD = 1.8 V, specified maximum sampling rate, 1.0 V internal reference, AIN = −1.0 dBFS, clock divider = 2, default SPI settings, unless otherwise noted. Table 4. Parameter CLOCK Clock Rate (at CLK+/CLK− Pins) Sample Rate Maximum 1 Minimum 2 Clock Pulse Width High Low LVDS DATA OUTPUT Data Propagation Delay (tPD) 3 DCO± Propagation Delay (tDCO)3 DCO± to Data Skew—Rising Edge Data (tSKEWR)3 DCO± to Data Skew—Falling Edge Data (tSKEWF)3 DCO± and Data Duty Cycle FCO± Propagation Delay (tFCO) 4 DCO± to FCO± Skew (tFRAME)4 DCO Output Frequency Output Date Rate LATENCY Pipeline Latency NSR Latency 5 NSR HB Filter Latency5 VDR Latency5 HB1 Filter Latency5 HB1 + HB2 Filter Latency5 HB1 + HB2 + HB3 Filter Latency5 HB1 + HB2 + HB3 + HB4 Filter Latency5 Fast Detect Latency Temperature Min Full 0.3 Full Full 500 250 MSPS MSPS Full Full 1000 1000 ps ps Full Full Full Full Full Full Full Full Full Full Full Full Full Full Full Full Full Full Rev. B | Page 8 of 81 −150 −150 44 −150 Typ 2.225 2.2 −25 −25 50 2.2 −25 33 8 24 8 50 101 217 433 28 Max Unit 4 GHz +100 +100 56 +100 500 1000 ns ns ps ps % ns ps MHz Mbps Clock cycles Clock cycles Clock cycles Clock cycles Clock cycles Clock cycles Clock cycles Clock cycles Clock cycles Data Sheet AD6679 Parameter Wake-Up Time 6 Standby Power-Down6 APERTURE Aperture Delay (tA) Aperture Uncertainty (Jitter, tJ) Out of Range Recovery Time Temperature Min Typ 25°C 25°C 1 Full Full Full 530 55 1 Max Unit 4 ms ms ps fs rms Clock cycles The maximum sample rate is the clock rate after the divider. The minimum sample rate operates at 300 MSPS with L = 2 or L = 1. This specification is valid for parallel interleaved, channel multiplexed, and byte mode output modes. 4 This specification is valid for byte mode output mode only. 5 Add this value to the pipeline latency specification to achieve total latency through the AD6679. 6 Wake-up time is defined as the time required to return to normal operation from power-down mode or standby mode. 1 2 3 TIMING SPECIFICATIONS Table 5. Parameter CLK± to SYNC± TIMING REQUIREMENTS tSU_SR tH_SR SPI TIMING REQUIREMENTS tDS tDH tCLK tS tH tHIGH tLOW tACCESS Test Conditions/Comments Min Device clock to SYNC± setup time Device clock to SYNC± hold time See Figure 3 Setup time between the data and the rising edge of SCLK Hold time between the data and the rising edge of SCLK Period of the SCLK Setup time between CSB and SCLK Hold time between CSB and SCLK Minimum period that SCLK is in a logic high state Minimum period that SCLK is in a logic low state Maximum time delay between falling edge of SCLK and output data valid for a read operation Time required for the SDIO pin to switch from an output to an input relative to the SCLK rising edge (not shown in Figure 3) tDIS_SDIO Typ Max Unit 117 −96 ps ps 6 ns ns ns ns ns ns ns ns 2 2 40 2 2 10 10 10 10 ns Timing Diagrams CLK– CLK+ tSU_SR tH_SR 13059-002 SYNC– SYNC+ Figure 2. SYNC± Setup and Hold Timing tHIGH tDS tS tCLK tDH tACCESS tH tLOW CSB SDIO DON’T CARE DON’T CARE R/W A14 A13 A12 A11 A10 A9 A8 A7 D7 Figure 3. Serial Port Interface Timing Diagram Rev. B | Page 9 of 81 D6 D3 D2 D1 D0 DON’T CARE 13059-003 SCLK DON’T CARE AD6679 Data Sheet APERTURE DELAY N + 33 N VIN±x N + 37 N + 34 N + 38 N–1 N+x N + 35 N+y N + 36 N + 39 SYNCHRONOUS LOW TO HIGH TRANSITION OF THE SYNC SIGNAL CAPTURED ON THE RISING EDGE OF THE CLK SIGNAL CAUSES THE DCO INTERNAL DIVIDER TO BE RESET SYNC+ SYNC– CLK+ CLK– tCLK tCH FIXED DELAY FROM SYNC EVENT TO DCO KNOWN PHASE tDCO tPD 2 × tCLK DCO± (DATA CLOCK OUTPUT) 0° PHASE ADJUST DCO± ((DATA CLOCK OUTPUT) 90° PHASE ADJUST 1 DCO± (DATA CLOCK OUTPUT) 180° PHASE ADJUST DCO± (DATA CLOCK OUTPUT) 270° PHASE ADJUST 2 STATUS BIT SELECTED BY OUTPUT MODE CONTROL 1 BITS, REGISTER 0x559[2:0] IN THE REGISTER MAP tSKEWF tSKEWR OVR+ (OVERRANGE/STATUS BIT) CONVERTER 0 CONVERTER 0 CONVERTER 0 CONVERTER 0 CONVERTER 0 SAMPLE SAMPLE SAMPLE SAMPLE SAMPLE [N + 4] [N + 3] [N + 2] [N + 1] [N] OVR OVR OVR OVR OVR OVR OVR D13± D13 D13 D13 D13 D13 D13 D13 D0± D0 D0 D0 D0 D0 D0 D0 190° PHASE ADJUST IS GENERATED USING THE FALLING EDGE OF CLK±. 2270° PHASE ADJUST IS GENERATED USING THE FALLING EDGE OF CLK±. Figure 4. Parallel Interleaved Mode—One Virtual Converter (Decimate by 1) Rev. B | Page 10 of 81 13059-004 OVR– Data Sheet AD6679 APERTURE DELAY N + 33 N VIN±x N + 35 N+x N + 34 SYNCHRONOUS LOW TO HIGH TRANSITION OF THE SYNC SIGNAL CAPTURED ON THE RISING EDGE OF THE CLK SIGNAL CAUSES THE DCO INTERNAL DIVIDER TO BE RESET SYNC+ SYNC– CLK+ CLK– tCLK tDCO tPD tCH DCO± (DATA CLOCK OUTPUT) 0° PHASE ADJUST DCO± (DATA CLOCK OUTPUT) 180° PHASE ADJUST STATUS BIT SELECTED BY OUTPUT MODE CONTROL 1 BITS, REGISTER 0x559[2:0] IN THE REGISTER MAP tSKEWR OVR+ (OVERRANGE/STATUS BIT) tSKEWF CONVERTER 0 SAMPLE [N] CONVERTER 1 SAMPLE [N] CONVERTER 0 SAMPLE [N + 1] CONVERTER 1 SAMPLE [N + 1] CONVERTER 0 SAMPLE [N + 2] OVR OVR OVR OVR OVR OVR OVR OVR D13± D13 D13 D13 D13 D13 D13 D13 D13 D0± D0 D0 D0 D0 D0 D0 D0 D0 Figure 5. Parallel Interleaved Mode—Two Virtual Converters (Decimate by 1) Rev. B | Page 11 of 81 13059-005 OVR– AD6679 Data Sheet APERTURE DELAY N + 33 N VIN±x N + 35 N+x N + 34 SYNCHRONOUS LOW TO HIGH TRANSITION OF THE SYSREF SIGNAL CAPTURED ON THE RISING EDGE OF THE CLK SIGNAL CAUSES THE DCO INTERNAL DIVIDER TO BE RESET SYNC+ SYNC– CLK+ CLK– tDCO tPD tCH tCLK DCO± (DATA CLOCK OUTPUT) 0° PHASE ADJUST DCO± (DATA CLOCK OUTPUT) 180° PHASE ADJUST STATUS BIT SELECTED BY OUTPUT MODE CONTROL 1 BITS, REGISTER 0x559[2:0] IN THE REGISTER MAP OVR+ (OVERRANGE/STAUS BIT) OVR OVR S[N – y] (ODD BITS) S[N – x] (EVEN BITS) tSKEWR OVR tSKEWF CONVERTERS SAMPLE [N] CONVERTERS SAMPLE [N] CONVERTERS SAMPLE [N + 1] CONVERTERS SAMPLE [N + 1] CONVERTERS SAMPLE [N + 2] OVR OVR OVR OVR OVR S[N] (ODD BITS) S[N + 1] (EVEN BITS) S[N + 1] (ODD BITS) S[N + 2] (EVEN BITS) OVR– S[N] S[N – 1] (ODD BITS) (EVEN BITS) A D0/D1± Figure 6. Channel Multiplexed (Even/Odd) Mode—One Virtual Converter (Decimate by 1) Rev. B | Page 12 of 81 13059-006 A D12/D13± Data Sheet AD6679 APERTURE DELAY N + 33 N VIN±x N + 35 N+x N + 34 SYNCHRONOUS LOW TO HIGH TRANSITION OF THE SYNC SIGNAL CAPTURED ON THE RISING EDGE OF THE CLK SIGNAL CAUSES THE DCO INTERNAL DIVIDER TO BE RESET SYNC+ SYNC– CLK+ CLK– tDCO tPD tCLK tCH DCO± (DATA CLOCK OUTPUT) 0° PHASE ADJUST DCO± (DATA CLOCK OUTPUT) 180° PHASE ADJUST STATUS BIT SELECTED BY OUTPUT MODE CONTROL 1 BITS, REGISTER 0x559[2:0] IN THE REGISTER MAP tSKEWR OVR+ (OVERRANGE/STATUS BIT) OVR tSKEWF CONVERTERS SAMPLE [N] CONVERTERS SAMPLE [N] CONVERTERS SAMPLE [N + 1] CONVERTERS SAMPLE [N + 1] CONVERTERS SAMPLE [N + 2] OVR OVR OVR OVR OVR OVR OVR S[N – y] (ODD BITS) S[N – x] (EVEN BITS) S[N] S[N – 1] (ODD BITS) (EVEN BITS) S[N] (ODD BITS) S[N + 1] (EVEN BITS) S[N + 1] (ODD BITS) S[N + 2] (EVEN BITS) S[N – y] (ODD BITS) S[N – x] (EVEN BITS) S[N] S[N – 1] (ODD BITS) (EVEN BITS) S[N] (ODD BITS) S[N + 1] (EVEN BITS) S[N + 1] (ODD BITS) S[N + 2] (EVEN BITS) OVR– A D12/D13± B D12/D13± B D0/D1± Figure 7. Channel Multiplexed (Even/Odd) Mode—Two Virtual Converters (Decimate by 1) Rev. B | Page 13 of 81 13059-007 A D0/D1± AD6679 Data Sheet APERTURE DELAY N+z N VIN±x N–1 N + 36 N + 33 N + 37 N + 39 N+x N + 34 N + 35 N+y N + 38 SYNCHRONOUS LOW TO HIGH TRANSITION OF THE SYNC SIGNAL CAPTURED ON THE RISING EDGE OF THE CLK SIGNAL CAUSES THE DCO/FCO DIVIDERS TO BE RESET SYNC+ SYNC– CLK+ CLK– tCLK FIXED DELAY FROM SYNC EVENT TO DCO KNOWN PHASE tCH tDCO tPD tFCO 2 × tCLK DCO± (DATA CLOCK OUTPUT) 0° PHASE ADJUST DCO± (DATA CLOCK OUTPUT) 90° PHASE ADJUST 1 DCO± (DATA CLOCK OUTPUT) 180° PHASE ADJUST DCO± (DATA CLOCK OUTPUT) 270° PHASE ADJUST 2 tFRAME tSKEWF tSKEWR FCO– (FRAME CLOCK OUTPUT)3 FRAME 0 FRAME 1 FRAME 2 FRAME 3 FCO+ STATUS+ (OVERRANGE STATUS BIT) I0[N] EVEN I0[N] ODD I1[N] EVEN I1[N] ODD I2[N + 1] EVEN I2[N + 1] ODD I3[N + 1] EVEN I3[N + 1] ODD PAR4 PAR OVR PAR OVR PAR OVR PAR OVR PAR DATA7± D15 D15 D14 D15 D14 D15 D14 D15 D14 D15 DATA0± D1 D1 D0 D1 D0 D1 D0 D1 D0 D1 STATUS– 1) ENABLED (ALWAYS ON) 2) DISABLED (ALWAYS OFF) 3) GAPPED PERIODIC (CONDITIONALLY ENABLED BASED ON PSEUDORANDOM BIT) 4STATUS BIT SELECTED BY THE OUTPUT MODE CONTROL 1 BITS, REGISTER 0x559[2:0] IN THE REGISTER MAP. Figure 8. LVDS Byte Mode—One Virtual Converter, One DDC (I Only, Decimate by 2) Rev. B | Page 14 of 81 13059-100 190° PHASE ADJUST IS GENERATED USING THE FALLING EDGE OF CLK±. 2270° PHASE ADJUST IS GENERATED USING THE FALLING EDGE OF CLK±. 3FRAME CLOCK OUTPUT SUPPORTS THREE MODES OF OPERATION: Data Sheet AD6679 APERTURE DELAY N+z N VIN±x N–1 N + 36 N + 33 N + 37 N + 39 N+x N + 34 N + 35 N+y N + 38 SYNCHRONOUS LOW TO HIGH TRANSITION OF THE SYNC SIGNAL CAPTURED ON THE RISING EDGE OF THE CLK SIGNAL CAUSES THE DCO/FCO DIVIDERS TO BE RESET SYNC+ SYNC– CLK+ CLK– tCLK FIXED DELAY FROM SYNC EVENT TO DCO KNOWN PHASE tCH tDCO tPD tFCO 2 × tCLK DCO± (DATA CLOCK OUTPUT) 0° PHASE ADJUST DCO± (DATA CLOCK OUTPUT) 90° PHASE ADJUST 1 DCO± (DATA CLOCK OUTPUT) 180° PHASE ADJUST DCO± (DATA CLOCK OUTPUT) 270° PHASE ADJUST 2 tFRAME FCO– (FRAME CLOCK OUTPUT)3 FRAME 0 FCO+ STATUS+ (OVERRANGE STATUS BIT) FRAME 1 tSKEWF tSKEWR I0[N] EVEN I0[N] ODD Q 0[N] EVEN Q 0[N] ODD I0[N + 1] EVEN I0[N + 1] Q 0[N + 1] Q 0[N + 1] ODD EVEN ODD PAR 4 PAR OVR PAR OVR PAR OVR PAR OVR PAR DATA7± D15 D15 D14 D15 D14 D15 D14 D15 D14 D15 DATA0± D1 D1 D0 D1 D0 D1 D0 D1 D0 D1 STATUS– 1) ENABLED (ALWAYS ON) 2) DISABLED (ALWAYS OFF) 3) GAPPED PERIODIC (CONDITIONALLY ENABLED BASED ON PSEUDORANDOM BIT) 4STATUS BIT SELECTED BY THE OUTPUT MODE CONTROL 1 BITS, REGISTER 0x559[2:0] IN THE REGISTER MAP. Figure 9. LVDS Byte Mode—Two Virtual Converters, One DDC (I/Q Decimate by 4) Rev. B | Page 15 of 81 13059-008 190° PHASE ADJUST IS GENERATED USING THE FALLING EDGE OF CLK±. 2270° PHASE ADJUST IS GENERATED USING THE FALLING EDGE OF CLK±. 3FRAME CLOCK OUTPUT SUPPORTS THREE MODES OF OPERATION: Rev. B | Page 16 of 81 Figure 10. LVDS Byte Mode—Four Virtual Converters, Two DDCs (I/Q Decimate by 8) D1 DATA0± N+y N+z N + 33 N + 34 N + 35 N + 36 N + 37 N + 38 N + 39 tCH tDCO tPD tFCO D0 D14 OVR I0[N] EVEN D1 D15 PAR D0 D14 OVR Q0[N] EVEN tSKEWF I0[N] ODD 1) ENABLED (ALWAYS ON) 2) DISABLED (ALWAYS OFF) 3) GAPPED PERIODIC (CONDITIONALLY ENABLED BASED ON PSEUDO-RANDOM BIT) 4STATUS BIT SELECTED BY OUTPUT MODE CONTROL 1 BITS, REGISTER 0x559[2:0] IN THE REGISTER MAP. D1 D15 PAR tSKEWR tFRAME 2 × tCLK D1 D15 PAR Q0[N] ODD D0 D14 OVR I1[N] EVEN FRAME 0 FRAME 0 D1 D15 PAR I1[N] ODD D0 D14 OVR Q1[N] EVEN FIXED DELAY FROM SYNC EVENT TO DCO KNOWN PHASE D1 D15 PAR Q1[N] ODD D0 D14 OVR I0[N+1] EVEN D1 D15 PAR I0[N+1] ODD D0 D14 OVR Q0[N+1] EVEN D1 D15 PAR Q0[N+1] ODD D0 D14 OVR I1[N + 1] EVEN D1 D15 PAR I1[N+1] ODD FRAME 1 FRAME 1 SYNCHRONOUS LOW TO HIGH TRANSITION OF THE SYNC SIGNAL CAPTURED ON THE RISING EDGE OF THE CLK SIGNAL CAUSES THE DCO/FCO DIVIDERS TO BE RESET N+x APERTURE DELAY 190° PHASE ADJUST IS GENERATED USING THE FALLING EDGE OF CLK±. 2270° PHASE ADJUST IS GENERATED USING THE FALLING EDGE OF CLK±. 3FRAME CLOCK OUTPUT SUPPORTS THREE MODES OF OPERATION: D15 PAR4 tCLK N–1 DATA7± STATUS– STATUS+ (OVERRANGE STATUS BIT) FCO+ FCO– (FRAME CLOCK OUTPUT)3 DCO± (DATA CLOCK OUTPUT) 270° PHASE ADJUST 2 DCO± (DATA CLOCK OUTPUT) 180° PHASE ADJUST DCO± (DATA CLOCK OUTPUT) 90° PHASE ADJUST 1 DCO± (DATA CLOCK OUTPUT) 0° PHASE ADJUST CLK– CLK+ SYNC– SYNC+ VIN±x N D0 D14 OVR Q1[N+1] EVEN D1 D15 PAR Q1[N+1] ODD AD6679 Data Sheet 13059-009 tCLK Rev. B | Page 17 of 81 D1 DATA0± N+x N+y APERTURE DELAY N+z Figure 11. LVDS Byte Mode—Eight Virtual Converters, Four DDCs (I/Q Decimate by 16) N + 34 N + 35 tDCO tPD tFCO N + 36 N + 37 N + 38 N + 39 D14 D0 D1 OVR I0[N] EVEN D15 PAR tSKEWR tFRAME D1 D15 PAR I0[N] ODD D0 D14 OVR Q0[N] EVEN tSKEWF 2 × tCLK D1 D15 PAR Q0[N] ODD D0 D14 OVR I1[N] EVEN FRAME 0 D1 D15 PAR I1[N] ODD D0 D14 OVR Q1[N] EVEN FIXED DELAY FROM SYSNC EVENT TO DCO KNOWN PHASE CLOCK OUTPUT SUPPORTS THREE MODES OF OPERATION: 1) ENABLED (ALWAYS ON) 2) DISABLED (ALWAYS OFF) 3) GAPPED PERIODIC (CONDITIONALLY ENABLED BASED ON PSEUDORANDOM BIT) 4STATUS BIT SELECTED BY OUTPUT MODE CONTROL 1 BITS, REGISTER 0x559[2:0] IN THE REGISTER MAP. 3FRAME N + 33 D1 D15 PAR Q1[N] ODD D0 D14 OVR I2[N] EVEN FRAME 0 D1 D15 PAR I2[N] ODD D0 D14 OVR Q2[N] EVEN D1 D15 PAR Q2[N] ODD D0 D14 OVR I3[N] EVEN D1 D15 PAR I3[N] ODD SYNCHRONOUS LOW TO HIGH TRANSITION OF THE SYNC SIGNAL CAPTURED ON THE RISING EDGE OF THE CLK SIGNAL CAUSES THE DCO/FCO DIVIDERS TO BE RESET tCH N 190° PHASE ADJUST IS GENERATED USING THE FALLING EDGE OF CLK±. 2270° PHASE ADJUST IS GENERATED USING THE FALLING EDGE OF CLK±. D15 PAR 4 N–1 DATA7± STATUS– STATUS+ (OVERRANGE STATUS BIT) FCO+ FCO– (FRAME CLOCK OUTPUT) 3 DCO± (DATA CLOCK OUTPUT) 270° PHASE ADJUST 2 DCO± (DATA CLOCK OUTPUT) 180° PHASE ADJUST DCO± (DATA CLOCK OUTPUT) 90° PHASE ADJUST 1 DCO± (DATA CLOCK OUTPUT) 0° PHASE ADJUST CLK– CLK+ SYNC– SYNC+ VIN±x D0 D14 OVR Q3[N] EVEN D1 D15 PAR Q3[N] ODD Data Sheet AD6679 13059-010 AD6679 Data Sheet ABSOLUTE MAXIMUM RATINGS Table 6. Parameter Electrical AVDD1 to AGND AVDD2 to AGND AVDD3 to AGND DVDD to DGND DRVDD to DRGND SPIVDD to AGND AGND to DRGND VIN±x to AGND SCLK, SDIO, CSB to AGND PDWN/STBY to AGND Environmental Operating Temperature Range Maximum Junction Temperature Storage Temperature Range (Ambient) THERMAL CHARACTERISTICS Rating 1.32 V 2.75 V 3.63 V 1.32 V 1.32 V 3.63 V −0.3 V to +0.3 V 3.2 V −0.3 V to SPIVDD + 0.3 V −0.3 V to SPIVDD + 0.3 V −40°C to +85°C +125°C −65°C to +150°C Typical θJA, ΨJB, and ΨJT are specified vs. the number of printed circuit board (PCB) layers in different airflow velocities (in m/sec). Airflow increases heat dissipation, effectively reducing θJA and ΨJB. In addition, metal in direct contact with the package leads from metal traces, through holes, ground, and power planes reduces the θJA. Thermal performance for actual applications requires careful inspection of the conditions in an application. The use of appropriate thermal management techniques is recommended to ensure that the maximum junction temperature does not exceed the limits shown in Table 6. Table 7. Thermal Resistance PCB Type JEDEC 2s2p Board Stresses at or above those listed under Absolute Maximum Ratings may cause permanent damage to the product. This is a stress rating only; functional operation of the product at these or any other conditions above those indicated in the operational section of this specification is not implied. Operation beyond the maximum operating conditions for extended periods may affect product reliability. 1 2 3 Airflow Velocity (m/sec) 0.0 θJA 27.01, 2 ΨJT 0.71, 3 Per JEDEC 51-7, plus JEDEC 51-5 2s2p test board. Per JEDEC JESD51-2 (still air) or JEDEC JESD51-6 (moving air). Per JEDEC JESD51-8 (still air). ESD CAUTION Rev. B | Page 18 of 81 ΨJB 7.31, 3 Unit °C/W Data Sheet AD6679 1 2 3 4 5 6 7 8 9 10 11 12 13 14 A AGND AGND AGND AVDD2 AVDD1 AGND CLK+ CLK– AGND AVDD1 AVDD2 AGND AGND AGND A B AVDD3 AGND AGND AVDD2 AVDD1 AGND AGND AGND AGND AVDD1 AVDD2 AGND AGND AVDD3 B C AVDD3 AGND AGND AVDD2 AVDD1 AGND SYNC+ SYNC– AGND AVDD1 AVDD2 AGND AGND AVDD3 C D AGND AGND AGND AVDD2 AVDD1 AGND AVDD1 AGND AGND AVDD1 AVDD2 AGND AGND AGND D E VIN–B AGND AGND AVDD2 AVDD1 AGND AGND AGND AGND AVDD1 AVDD2 AGND AGND VIN–A E F VIN+B AGND AGND AVDD2 AGND AGND AGND AGND AGND AGND AVDD2 AGND AGND VIN+A F G AGND AGND AGND AGND AGND AGND AGND AGND AGND AGND AVDD2 AGND AGND AGND G H AGND AGND AGND CSB AGND AGND AGND AGND AGND V_1P0 AGND AGND AGND AGND H FD_A J J FD_B AGND AGND SCLK SPIVDD AGND AGND AGND AGND AVDD2 SPIVDD AGND PDWN/ STBY K DGND DGND AGND SDIO AGND AGND AGND AGND AGND AGND AGND AGND DCO– DCO+ K L DVDD DVDD DGND DGND AGND AGND AGND AGND AGND AGND AGND AGND OVR– OVR+ L M D1+ D1– DVDD DVDD DRVDD DRVDD DRVDD DRGND DRGND DRGND DRGND DRGND D13– D13+ M N D2– D3– D4– D5– D6– D0– DRVDD DRGND D7– D8– D9– D10– D11– D12– N P D2+ D3+ D4+ D5+ D6+ D0+ DRVDD DRGND D7+ D8+ D9+ D10+ D11+ D12+ P 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1.25V ANALOG SUPPLY 2.50V ANALOG SUPPLY 3.3V ANALOG SUPPLY 1.25V DIGITAL SUPPLY 1.25V LVDS DRIVER SUPPLY 1.22V TO 3.4V SPI SUPPLY ANALOG GROUND DIGITAL GROUND LVDS DRIVER GROUND ADC I/O LVDS INTERFACE SPI INTERFACE Figure 12. Pin Configuration—Parallel Interleaved LVDS Mode (Top View) Table 8. Pin Function Descriptions—Parallel Interleaved LVDS Mode Pin No. Power Supplies A5, A10, B5, B10, C5, C10, D5, D7, D10, E5, E10 A4, A11, B4, B11, C4, C11, D4, D11, E4, E11, F4, F11, G11, J10 B1, B14, C1, C14 L1, L2, M3, M4 M5 to M7, N7, P7 J5, J11 K1, K2, L3, L4 M8 to M12, N8, P8 A1 to A3, A6, A9, A12 to A14, B2, B3, B6 to B9, B12, B13, C2, C3, C6, C9, C12, C13, D1 to D3, D6, D8, D9, D12 to D14, E2, E3, E6 to E9, E12, E13, F2, F3, F5 to F10, F12, F13, G1 to G10, G12 to G14, H1 to H3, H5 to H9, H11 to H14, J2, J3, J6 to J9, J12, K3, K5 to K12, L5 to L12 Analog E14, F14 E1, F1 Mnemonic Type Description AVDD1 AVDD2 Supply Supply Analog Power Supply (1.25 V Nominal). Analog Power Supply (2.50 V Nominal). AVDD3 DVDD DRVDD SPIVDD DGND DRGND AGND Supply Supply Supply Supply Ground Ground Ground Analog Power Supply (3.3 V Nominal) Digital Power Supply (1.25 V Nominal). Digital Driver Power Supply (1.25 V Nominal). Digital Power Supply for SPI (1.22 V to 3.4 V). Ground Reference for DVDD. Ground Reference for DRVDD. Analog Ground. VIN−A, VIN+A VIN−B, VIN+B Input ADC A Analog Input Complement/True. Input ADC B Analog Input Complement/True. Rev. B | Page 19 of 81 13059-011 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS AD6679 Data Sheet Pin No. H10 Mnemonic V_1P0 Type Input/DNC A7, A8 CMOS Outputs J14, J1 Digital Inputs C7, C8 CLK+, CLK− Input Description 1.0 V Reference Voltage Input/Do Not Connect. This pin is configurable through the SPI as a no connect or as an input. Do not connect this pin if using the internal reference. This pin requires a 1.0 V reference voltage input if using an external voltage reference source. Clock Input True/Complement. FD_A, FD_B Output Fast Detect Outputs for Channel A and Channel B. SYNC+, SYNC− Input Active High LVDS Sync Input—True/Complement. D0−, D0+ D1−, D1+ D2−, D2+ D3−, D3+ D4−, D4+ D5−, D5+ D6−, D6+ D7−, D7+ D8−, D8+ D9−, D9+ D10−, D10+ D11−, D11+ D12−, D12+ D13−, D13+ OVR−, OVR+ DCO−, DCO+ Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output LVDS Lane 0 Output Data—Complement/True. LVDS Lane 1 Output Data—Complement/True. LVDS Lane 2 Output Data—Complement/True. LVDS Lane 3 Output Data—Complement/True. LVDS Lane 4 Output Data—Complement/True. LVDS Lane 5 Output Data—Complement/True. LVDS Lane 6 Output Data—Complement/True. LVDS Lane 7 Output Data—Complement/True. LVDS Lane 8 Output Data—Complement/True. LVDS Lane 9 Output Data—Complement/True. LVDS Lane 10 Output Data—Complement/True. LVDS Lane 11 Output Data—Complement/True. LVDS Lane 12 Output Data—Complement/True. LVDS Lane 13 Output Data—Complement/True. LVDS Overrange Output Data—Complement/True. LVDS Digital Clock Output Data—Complement/True. SDIO SCLK CSB PDWN/STBY Input/output Input Input Input SPI Serial Data Input/Output. SPI Serial Clock. SPI Chip Select (Active Low). Power-Down Input (Active High)/Standby. The operation of this pin depends on the SPI mode and can be configured in power-down or standby mode. Data Outputs N6, P6 M2, M1 N1, P1 N2, P2 N3, P3 N4, P4 N5, P5 N9, P9 N10, P10 N11, P11 N12, P12 N13, P13 N14, P14 M13, M14 L13, L14 K13, K14 Device Under Test (DUT) Controls K4 J4 H4 J13 Rev. B | Page 20 of 81 Data Sheet AD6679 1 2 3 4 5 6 7 8 9 10 11 12 13 14 A AGND AGND AGND AVDD2 AVDD1 AGND CLK+ CLK– AGND AVDD1 AVDD2 AGND AGND AGND A B AVDD3 AGND AGND AVDD2 AVDD1 AGND AGND AGND AGND AVDD1 AVDD2 AGND AGND AVDD3 B C AVDD3 AGND AGND AVDD2 AVDD1 AGND SYNC+ SYNC– AGND AVDD1 AVDD2 AGND AGND AVDD3 C D AGND AGND AGND AVDD2 AVDD1 AGND AVDD1 AGND AGND AVDD1 AVDD2 AGND AGND AGND D E VIN–B AGND AGND AVDD2 AVDD1 AGND AGND AGND AGND AVDD1 AVDD2 AGND AGND VIN–A E F VIN+B AGND AGND AVDD2 AGND AGND AGND AGND AGND AGND AVDD2 AGND AGND VIN+A F G AGND AGND AGND AGND AGND AGND AGND AGND AGND AGND AVDD2 AGND AGND AGND G H AGND AGND AGND CSB AGND AGND AGND AGND AGND V_1P0 AGND AGND AGND AGND H J FD_B AGND AGND SCLK SPIVDD AGND AGND AGND AGND AVDD2 SPIVDD AGND PDWN/ STBY FD_A J K DGND DGND AGND SDIO AGND AGND AGND AGND AGND AGND AGND AGND DCO– DCO+ K L DVDD DVDD DGND DGND AGND AGND AGND AGND AGND AGND AGND AGND OVR– OVR+ L M B D2/D3 + B D2/D3 – DVDD DVDD DRVDD DRVDD DRVDD DRGND DRGND DRGND DRGND DRGND N B D4/D5– B D6/D7 – B D8/D9 – B D10/D11 – B D12/D13 – B D0/D1 – DRVDD DRGND A D0/D1 – A D2/D3 – A D4/D5– A D6/D7– A D8/D9– A D10/D11– N P B D4/D5 + B D6/D7+ B D8/D9 + B D10/D11 + B D12/D13 + B D0/D1 + DRVDD DRGND A D0/D1 + A D2/D3 + A D4/D5 + A D6/D7 + A D8/D9 + A D10/D11 + P 1 2 3 6 7 8 9 10 11 12 13 1.25V ANALOG SUPPLY 2.50V ANALOG SUPPLY 3.3V ANALOG SUPPLY 5 1.25V DIGITAL SUPPLY 1.25V LVDS DRIVER SUPPLY 1.22V TO 3.4V SPI SUPPLY ANALOG GROUND DIGITAL GROUND LVDS DRIVER GROUND 14 ADC I/O LVDS INTERFACE SPI INTERFACE 13059-012 4 A D12/D13– A D12/D13+ M Figure 13. Pin Configuration—Channel Multiplexed (Even/Odd) LVDS Mode (Top View) Table 9. Pin Function Descriptions—Channel Multiplexed (Even/Odd) LVDS Mode 1 Pin No. Power Supplies A5, A10, B5, B10, C5, C10, D5, D7, D10, E5, E10 A4, A11, B4, B11, C4, C11, D4, D11, E4, E11, F4, F11, G11, J10 B1, B14, C1, C14 L1, L2, M3, M4 M5 to M7, N7, P7 J5, J11 K1, K2, L3, L4 M8 to M12, N8, P8 A1 to A3, A6, A9, A12 to A14, B2, B3, B6 to B9, B12, B13, C2, C3, C6, C9, C12, C13, D1 to D3, D6, D8, D9, D12 to D14, E2, E3, E6 to E9, E12, E13, F2, F3, F5 to F10, F12, F13, G1 to G10, G12 to G14, H1 to H3, H5 to H9, H11 to H14, J2, J3, J6 to J9, J12, K3, K5 to K12, L5 to L12 Analog E14, F14 E1, F1 H10 A7, A8 Mnemonic Type Description AVDD1 Supply Analog Power Supply (1.25 V Nominal). AVDD2 Supply Analog Power Supply (2.50 V Nominal). AVDD3 DVDD DRVDD SPIVDD DGND DRGND AGND Supply Supply Supply Supply Ground Ground Ground Analog Power Supply (3.3 V Nominal) Digital Power Supply (1.25 V Nominal). Digital Driver Power Supply (1.25 V Nominal). Digital Power Supply for SPI (1.22 V to 3.4 V). Ground Reference for DVDD. Ground Reference for DRVDD. Analog Ground. VIN−A, VIN+A VIN−B, VIN+B V_1P0 Input Input Input/DNC CLK+, CLK− Input ADC A Analog Input Complement/True. ADC B Analog Input Complement/True. 1.0 V Reference Voltage Input/Do Not Connect. This pin is configurable through the SPI as a no connect or as an input. Do not connect this pin if using the internal reference. This pin requires a 1.0 V reference voltage input if using an external voltage reference source. Clock Input True/Complement. Rev. B | Page 21 of 81 AD6679 Pin No. CMOS Outputs J14, J1 Digital Inputs C7, C8 Data Outputs N9, P9 N10, P10 N11, P11 N12, P12 N13, P13 N14, P14 M13, M14 N6, P6 M2, M1 N1, P1 N2, P2 N3, P3 N4, P4 N5, P5 L13, L14 K13, K14 DUT Controls K4 J4 H4 J13 1 Data Sheet Mnemonic Type Description FD_A, FD_B Output Fast Detect Outputs for Channel A and Channel B. SYNC+, SYNC− Input Active High LVDS Sync Input—True/Complement. A D0/D1−, A D0/D1+ A D2/D3−, A D2/D3+ A D4/D5−, A D4/D5+ A D6/D7−, A D6/D7+ A D8/D9−, A D8/D9+ A D10/D11−, A D10/D11+ A D12/D13−, A D12/D13+ B D0/D1−, B D0/D1+ B D2/D3−, B D2/D3+ B D4/D5−, B D4/D5+ B D6/D7−, B D6/D7+ B D8/D9−, B D8/D9+ B D10/D11−, B D10/D11+ B D12/D13−, B D12/D13+ OVR−, OVR+ DCO−, DCO+ Output LVDS Channel A Data 0/Data 1 Output Data— Complement/True. LVDS Channel A Data 2/Data 3 Output Data— Complement/True. LVDS Channel A Data 4/Data 5 Output Data— Complement/True. LVDS Channel A Data 6/Data 7 Output Data— Complement/True. LVDS Channel A Data 8/Data 9 Output Data— Complement/True. LVDS Channel A Data 10/Data 11 Output Data— Complement/True. LVDS Channel A Data 12/Data 13 Output Data— Complement/True. LVDS Channel B Data 0/Data 1 Output Data— Complement/True. LVDS Channel B Data 2/Data 3 Output Data— Complement/True. LVDS Channel B Data 4/Data 5 Output Data— Complement/True. LVDS Channel B Data 6/Data 7 Output Data— Complement/True. LVDS Channel B Data 8/Data 9 Output Data— Complement/True. LVDS Channel B Data 10/Data 11 Output Data— Complement/True. LVDS Channel B Data 12/Data 13 Output Data— Complement/True. LVDS Overrange Output Data—Complement/True. LVDS Digital Clock Output Data—Complement/True. SDIO SCLK CSB PDWN/STBY Input/output Input Input Input Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output SPI Serial Data Input/Output. SPI Serial Clock. SPI Chip Select (Active Low). Power-Down Input (Active High). The operation of this pin depends on the SPI mode and can be configured in power-down or standby mode. When using channel multiplexed (even/odd) LVDS mode for one converter, the Channel B outputs are disabled and can be left unconnected. Rev. B | Page 22 of 81 Data Sheet AD6679 1 2 3 4 5 6 7 8 9 10 11 12 13 14 A AGND AGND AGND AVDD2 AVDD1 AGND CLK+ CLK– AGND AVDD1 AVDD2 AGND AGND AGND A B AVDD3 AGND AGND AVDD2 AVDD1 AGND AGND AGND AGND AVDD1 AVDD2 AGND AGND AVDD3 B C AVDD3 AGND AGND AVDD2 AVDD1 AGND SYNC+ SYNC– AGND AVDD1 AVDD2 AGND AGND AVDD3 C D AGND AGND AGND AVDD2 AVDD1 AGND AVDD1 AGND AGND AVDD1 AVDD2 AGND AGND AGND D E VIN–B AGND AGND AVDD2 AVDD1 AGND AGND AGND AGND AVDD1 AVDD2 AGND AGND VIN–A E F VIN+B AGND AGND AVDD2 AGND AGND AGND AGND AGND AGND AVDD2 AGND AGND VIN+A F G AGND AGND AGND AGND AGND AGND AGND AGND AGND AGND AVDD2 AGND AGND AGND G H AGND AGND AGND CSB AGND AGND AGND AGND AGND V_1P0 AGND AGND AGND AGND H FD_A J J FD_B AGND AGND SCLK SPIVDD AGND AGND AGND AGND AVDD2 SPIVDD AGND PDWN/ STBY K DGND DGND AGND SDIO AGND AGND AGND AGND AGND AGND AGND AGND DCO– DCO+ K L DVDD DVDD DGND DGND AGND AGND AGND AGND AGND AGND AGND AGND FCO– FCO+ L M DNC DNC DVDD DVDD DRVDD DRVDD DRVDD DRGND DRGND DRGND DRGND DRGND STATUS– STATUS+ M N DNC DNC DNC DATA0 – DATA1 – DNC DRVDD DRGND DATA2– DATA3 – DATA4– DATA5– DATA 6– DATA7 – N P DNC DNC DNC DATA0 + DATA1 + DNC DRVDD DRGND DATA2+ DATA3 + DATA4 + DATA5 + DATA6 + DATA7 + P 1 2 3 4 5 6 7 8 9 10 11 12 13 1.25V DIGITAL SUPPLY 1.25V LVDS DRIVER SUPPLY 1.22V TO 3.4V SPI SUPPLY ANALOG GROUND DIGITAL GROUND LVDS DRIVER GROUND ADC I/O LVDS INTERFACE SPI INTERFACE 14 DO NOT CONNECT 13059-013 1.25V ANALOG SUPPLY 2.50V ANALOG SUPPLY 3.3V ANALOG SUPPLY Figure 14. Pin Configuration—LVDS Byte Mode (Top View) Table 10. Pin Function Descriptions—LVDS Byte Mode Pin No. Power Supplies A5, A10, B5, B10, C5, C10, D5, D7, D10, E5, E10 A4, A11, B4, B11, C4, C11, D4, D11, E4, E11, F4, F11, G11, J10 B1, B14, C1, C14 L1, L2, M3, M4 M5 to M7, N7, P7 J5, J11 K1, K2, L3, L4 M8 to M12, N8, P8 A1 to A3, A6, A9, A12 to A14, B2, B3, B6 to B9, B12, B13, C2, C3, C6, C9, C12, C13, D1 to D3, D6, D8, D9, D12 to D14, E2, E3, E6 to E9, E12, E13, F2, F3, F5 to F10, F12, F13, G1 to G10, G12 to G14, H1 to H3, H5 to H9, H11 to H14, J2, J3, J6 to J9, J12, K3, K5 to K12, L5 to L12 Analog E14, F14 Mnemonic Type Description AVDD1 AVDD2 Supply Supply Analog Power Supply (1.25 V Nominal). Analog Power Supply (2.50 V Nominal). AVDD3 DVDD DRVDD SPIVDD DGND DRGND AGND Supply Supply Supply Supply Ground Ground Ground Analog Power Supply (3.3 V Nominal) Digital Power Supply (1.25 V Nominal). Digital Driver Power Supply (1.25 V Nominal). Digital Power Supply for SPI (1.22 V to 3.4 V). Ground Reference for DVDD. Ground Reference for DRVDD. Analog Ground. Input ADC A Analog Input Complement/True. Input ADC B Analog Input Complement/True. H10 VIN−A, VIN+A VIN−B, VIN+B V_1P0 Input/DNC A7, A8 CLK+, CLK− Input 1.0 V Reference Voltage Input/Do Not Connect. This pin is configurable through the SPI as a no connect or an input. Do not connect this pin if using the internal reference. This pin requires a 1.0 V reference voltage input if using an external voltage reference source. Clock Input True/Complement. E1, F1 Rev. B | Page 23 of 81 AD6679 Pin No. CMOS Outputs J14, J1 Digital Inputs C7, C8 Data Sheet Mnemonic Type Description FD_A, FD_B Output Fast Detect Outputs for Channel A and Channel B. SYNC+, SYNC− Input Active High LVDS Sync Input—True/Complement. DATA0−, DATA0+ DATA1−, DATA1+ DATA2−, DATA2+ DATA3−, DATA3+ DATA4−, DATA4+ DATA5−, DATA5+ DATA6−, DATA6+ DATA7−, DATA7+ STATUS−, STATUS+ FCO−, FCO+ DCO−, DCO+ Output LVDS Byte Data 0—Complement/True. Output LVDS Byte Data 1—Complement/True. Output LVDS Byte Data 2—Complement/True. Output LVDS Byte Data 3—Complement/True. Output LVDS Byte Data 4—Complement/True. Output LVDS Byte Data 5—Complement/True. Output LVDS Byte Data 6—Complement/True. Output LVDS Byte Data 7—Complement/True. Output LVDS Status Output Data—Complement/True. Output Output LVDS Frame Clock Output Data—Complement/True. LVDS Digital Clock Output Data—Complement/True. DUT Controls K4 J4 H4 J13 SDIO SCLK CSB PDWN/STBY Input/output Input Input Input SPI Serial Data Input/Output. SPI Serial Clock. SPI Chip Select (Active Low). Power-Down Input (Active High). The operation of this pin depends on the SPI mode and can be configured in power-down or standby mode. No Connects M1, M2, N1 to N3, N6, P1 to P3, P6 DNC DNC Do Not Connect. Do not connect to these pins. Data Outputs N4, P4 N5, P5 N9, P9 N10, P10 N11, P11 N12, P12 N13, P13 N14, P14 M13, M14 L13, L14 K13, K14 Rev. B | Page 24 of 81 Data Sheet AD6679 TYPICAL PERFORMANCE CHARACTERISTICS AVDD1 = 1.25 V, AVDD2 = 2.50 V, AVDD3 = 3.3 V, DVDD = 1.25 V, DRVDD = 1.25 V, SPIVDD = 1.8 V, AIN = −1.0 dBFS, VDR mode (no violation of VDR mask), clock divider = 2, otherwise default SPI settings, TA = 25°C, 128k FFT sample, unless otherwise noted. 0 0 AIN = −1dBFS SNR = 68.9dBFS ENOB = 10.9 BITS SFDR = 83dBFS BUFFER CONTROL 1 = 2.0× –20 –40 AMPLITUDE (dBFS) –40 –60 –80 –100 –80 –100 –120 0 25 50 75 100 125 150 175 200 225 250 FREQUENCY (MHz) –140 13059-014 –140 0 75 100 125 150 175 200 225 250 225 250 225 250 Figure 18. Single-Tone FFT with fIN = 450.3 MHz 0 0 AIN = −1dBFS SNR = 68.7dBFS ENOB = 10.9 BITS SFDR = 84dBFS BUFFER CONTROL 1 = 2.0× –20 AIN = −1dBFS SNR = 63.9dBFS ENOB = 10.3 BITS SFDR = 81dBFS BUFFER CONTROL 1 = 5.0× –20 –40 AMPLITUDE (dBFS) –40 –60 –80 –100 –120 –60 –80 –100 –120 0 25 50 75 100 125 150 175 200 225 250 FREQUENCY (MHz) –140 13059-015 –140 0 25 50 75 100 125 150 175 200 FREQUENCY (MHz) Figure 16. Single-Tone FFT with fIN = 170.3 MHz 13059-018 AMPLITUDE (dBFS) 50 FREQUENCY (MHz) Figure 15. Single Tone FFT with fIN = 10.3 MHz Figure 19. Single-Tone FFT with fIN = 765.3 MHz 0 0 AIN = −1dBFS SNR = 67.8dBFS ENOB = 10.8 BITS SFDR = 82dBFS BUFFER CONTROL 1 = 4.5× –20 AIN = −1dBFS SNR = 62.8dBFS ENOB = 10.1 BITS SFDR = 76dBFS BUFFER CONTROL 1 = 5.0× –20 –40 AMPLITUDE (dBFS) –40 –60 –80 –100 –60 –80 –100 –120 –120 –140 0 25 50 75 100 125 150 175 200 FREQUENCY (MHz) 225 250 13059-016 AMPLITUDE (dBFS) 25 13059-017 –120 –60 Figure 17. Single-Tone FFT with fIN = 340.3 MHz –140 0 25 50 75 100 125 150 175 200 FREQUENCY (MHz) Figure 20. Single-Tone FFT with fIN = 985.3 MHz Rev. B | Page 25 of 81 13059-019 AMPLITUDE (dBFS) AIN = −1dBFS SNR = 67.3dBFS ENOB = 10.8 BITS SFDR = 86dBFS BUFFER CONTROL 1 = 4.5× –20 AD6679 Data Sheet 95 0 AIN = −1dBFS SNR = 61.7dBFS ENOB = 9.9 BITS SFDR = 70dBFS BUFFER CONTROL 1 = 8.0× –20 90 SFDR SNR/SFDR (dBFS) –60 –80 85 80 75 –100 70 0 25 50 75 100 125 150 175 200 225 250 FREQUENCY (MHz) 65 200 13059-020 –140 Figure 21. Single-Tone FFT with fIN = 1205.3 MHz SFDR, 2.0× SNRFS, 2.0× SFDR, 3.0× SNRFS, 3.0× SFDR, 4.0× SNRFS, 4.0× 90 85 SNR/SFDR (dBFS) –60 –80 –100 80 75 70 –120 –140 0 25 50 75 100 125 150 175 200 225 250 FREQUENCY (MHz) 13059-021 65 60 50 150 200 250 300 350 400 450 500 ANALOG INPUT FREQUENCY (MHz) Figure 22. Single-Tone FFT with fIN = 1630.3 MHz Figure 25. SNR/SFDR vs. Analog Input Frequency (fIN); fIN < 500 MHz; Buffer Control 1 Setting = 2.0×, 3.0×, and 4.0× 0 0 AIN = −1dBFS SNR = 59.0dBFS ENOB = 9.5 BITS SFDR = 69dBFS BUFFER CONTROL 1 = 8.0× –20 100 13059-024 AMPLITUDE (dBFS) 500 450 95 AIN = −1dBFS SNR = 60.1dBFS ENOB = 9.7 BITS SFDR = 71dBFS BUFFER CONTROL 1 = 8.0× –40 AIN1 AND AIN2 = –7dBFS SFDR = 88dBFS IMD2 = 95dBFS IMD3 = 88dBFS BUFFER CONTROL 1 = 2.0× –20 AMPLITUDE (dBFS) –40 –60 –80 –100 –40 –60 –80 –100 –120 –140 0 25 50 75 100 125 150 175 200 225 FREQUENCY (MHz) 250 13059-022 AMPLITUDE (dBFS) 400 300 350 SAMPLE RATE (MHz) 250 Figure 24. SNR/SFDR vs. Sample Rate (fS); fIN = 170.3 MHz; 0 –20 SNR 13059-023 –120 Figure 23. Single-Tone FFT with fIN = 1950.3 MHz –120 0 50 100 150 200 FREQUENCY (MHz) Figure 26. Two-Tone FFT; fIN1 = 184 MHz, fIN2 = 187 MHz Rev. B | Page 26 of 81 250 13059-025 AMPLITUDE (dBFS) –40 Data Sheet AD6679 100 0 80 SNR (dBc) SNR/SFDR (dBc AND dBFS) –20 –40 –60 –80 –100 60 SFDR (dBFS) 40 SNR (dBc) 20 0 0 –6 –12 –18 –24 –30 –36 –42 –48 FREQUENCY (MHz) –40 –60 250 –54 200 –66 150 –72 100 –78 50 –90 0 13059-026 –120 INPUT AMPLITUDE (dBFS) 13059-029 –20 –84 AMPLITUDE (dBFS) SFDR (dBc) AIN1 AND AIN2 = –7dBFS SFDR = 87dBFS IMD2 = 94dBFS IMD3 = 87dBFS BUFFER CONTROL 1 = 2.0× Figure 30. SNR/SFDR vs. Input Amplitude, fIN = 170.3 MHz Figure 27. Two-Tone FFT; fIN1 = 338 MHz, fIN2 = 341 MHz 90 0 SFDR –20 85 SNR/SFDR (dBFS) –40 IMD3 (dBc) –60 –80 SFDR (dBFS) 80 75 –100 70 IMD3 (dBFS) –140 –90 –84 –78 –72 –66 –60 –54 –48 –42 –36 –30 –24 –18 –12 –6 INPUT AMPLITUDE (dBFS) SNR 65 –40 –25 –10 0 15 25 TEMPERATURE (°C) 40 55 70 85 13059-030 –120 13059-027 SFDR/IMD3 (dBc AND dBFS) SFDR (dBc) Figure 31. SNR/SFDR vs. Temperature, fIN = 170.3 MHz Figure 28. Two-Tone SFDR/IMD3 vs. Input Amplitude (AIN) with fIN1 = 184 MHz and fIN2 = 187 MHz 2.30 0 2.25 –20 2.20 2.15 –40 IMD3 (dBc) POWER (W) SFDR/IMD3 (dBc AND dBFS) SFDR (dBc) –60 –80 SFDR (dBFS) 2.10 2.05 2.00 1.95 –100 1.90 –120 1.85 IMD3 (dBFS) Figure 29. Two-Tone SFDR/IMD3 vs. Input Amplitude (AIN) with fIN1 = 338 MHz and fIN2 = 341 MHz Rev. B | Page 27 of 81 500 480 460 440 420 400 380 360 340 320 300 SAMPLE RATE (MSPS) Figure 32. Power Dissipation vs. Sample Rate (fS), Default SPI 13059-031 INPUT AMPLITUDE (dBFS) 13059-028 1.80 –140 –90 –84 –78 –72 –66 –60 –54 –48 –42 –36 –30 –24 –18 –12 –6 AD6679 Data Sheet EQUIVALENT CIRCUITS AVDD3 AVDD3 AVDD3 3pF 1.5pF 200Ω SWING CONTROL (SPI) VCM BUFFER 200Ω 67Ω 28Ω 10pF 200Ω 400Ω DRVDD AVDD3 D0+ TO D13+; A Dx/Dy+ AND B Dx/Dy+; DATA0+ TO DATA7+ DATA+ AVDD3 OUTPUT DRIVER VIN–x D0– TO D13–; A Dx/Dy– AND B Dx/Dy–; DATA0– TO DATA7– DATA– 13059-032 AIN CONTROL (SPI) 3pF 1.5pF DRGND Figure 36. Digital Outputs Figure 33. Analog Inputs SPIVDD AVDD1 25Ω ESD PROTECTED SCLK 30kΩ AVDD1 ESD PROTECTED 20kΩ 20kΩ VCM = 0.85V 13059-033 25Ω CLK– SPIVDD 1kΩ 13059-036 CLK+ DRGND DRVDD Figure 34. Clock Inputs Figure 37. SCLK Inputs AVDD1 1kΩ ESD PROTECTED 20kΩ LEVEL TRANSLATOR AVDD1 VCM = 0.85V ESD PROTECTED 20kΩ 1kΩ 13059-034 SYNC– CSB 30kΩ 1kΩ 13059-037 SYNC+ SPIVDD Figure 35. SYNC± Inputs Figure 38. CSB Input Rev. B | Page 28 of 81 13059-035 67Ω 200Ω 28Ω VIN+x Data Sheet AD6679 SPIVDD SPIVDD ESD PROTECTED SDO 1kΩ SDIO ESD PROTECTED SPIVDD SDI 30kΩ 1kΩ PDWN/ STBY 30kΩ ESD PROTECTED Figure 39. SDIO PDWN CONTROL (SPI) Figure 41. PDWN/STBY Input AVDD2 SPIVDD ESD PROTECTED FD V_1P0 FD_A/FD_B TEMPERATURE DIODE (FD_A ONLY) FD_x PIN CONTROL (SPI) ESD PROTECTED 13059-039 ESD PROTECTED V_1P0 PIN CONTROL (SPI) Figure 42. V_1P0 Input/Output Figure 40. FD_A/FD_B Outputs Rev. B | Page 29 of 81 13059-041 ESD PROTECTED 13059-040 13059-038 ESD PROTECTED AD6679 Data Sheet THEORY OF OPERATION The AD6679 has several functions that simplify the AGC function in a communications receiver. The programmable threshold detector allows monitoring of the incoming signal power using the fast detect bits of the ADC output data stream, which are enabled and programmed via Register 0x245 through Register 0x24C. If the input signal level exceeds the programmable threshold, the fast detect indicator goes high. Because this threshold indicator has low latency, the user can quickly reduce the system gain to avoid an overrange condition at the ADC input. The LVDS outputs can be configured depending on the decimation ratio. Multiple device synchronization is supported through the SYNC± input pins. ADC ARCHITECTURE The architecture consists of an input buffered pipelined ADC. The input buffer provides a termination impedance to the analog input signal. This termination impedance can be changed using the SPI to meet the termination needs of the driver/amplifier. The default termination value is set to 400 Ω. The equivalent circuit diagram of the analog input termination is shown in Figure 33. The input buffer is optimized for high linearity, low noise, and low power. The input buffer provides a linear high input impedance (for ease of drive) and reduces the kickback from the ADC. The quantized outputs from each stage are combined into a final 16-bit result in the digital correction logic. The pipelined architecture permits the first stage to operate with a new input sample while the remaining stages operate with the preceding samples. Sampling occurs on the rising edge of the clock. For best dynamic performance, match the source impedances driving VIN+x and VIN−x such that common-mode settling errors are symmetrical. These errors are reduced by the commonmode rejection of the ADC. An internal reference buffer creates a differential reference that defines the span of the ADC core. Maximum SNR performance is achieved by setting the ADC to the largest span in a differential configuration. In the case of the AD6679, the available span is programmable through the SPI port from 1.46 V p-p to 2.06 V p-p differential with 2.06 V p-p differential being the default. Differential Input Configurations There are several ways to drive the AD6679, either actively or passively. However, optimum performance is achieved by driving the analog input differentially. For applications in which SNR and SFDR are key parameters, differential transformer coupling is the recommended input configuration (see Figure 43 and Figure 44) because the noise performance of most amplifiers is not adequate to achieve the true performance of the AD6679. For low to midrange frequencies, it is recommended to use a double balun or double transformer network (see Figure 43) for optimum performance from the AD6679. For higher frequencies in the second or third Nyquist zone, it is better to remove some of the front-end passive components to ensure wideband operation (see Figure 44). ETC1-11-13/ MABA007159 1:1Z 10Ω 10Ω 0.1µF 25Ω ANALOG INPUT CONSIDERATIONS The analog input to the AD6679 is a differential buffer. The internal common-mode voltage of the buffer is 2.05 V. The clock signal alternately switches the input circuit between sample mode and hold mode. When the input circuit is switched into sample mode, the signal source must be capable of charging the sample capacitors and settling within one-half of a clock cycle. A small resistor, in series with each input, can help reduce the peak transient current inserted from the output stage of the driving source. In addition, low Q inductors or ferrite beads can be placed on each section of the input to reduce high differential capacitance at the analog inputs and, thus, achieve the 4pF 2pF 0.1µF 25Ω 10Ω ADC 10Ω 0.1µF 13059-042 The dual ADC cores feature a multistage, differential pipelined architecture with integrated output error correction logic. Each ADC features wide bandwidth inputs supporting a variety of user-selectable input ranges. An integrated voltage reference eases design considerations. maximum bandwidth of the ADC. Such use of low Q inductors or ferrite beads is required when driving the converter front end at high IF frequencies. Place either a differential capacitor or two single-ended capacitors on the inputs to provide a matching passive network. This ultimately creates a low-pass filter (LPF) at the input, which limits unwanted broadband noise. For more information, refer to the AN-742 Application Note, the AN-827 Application Note, and the Analog Dialogue article “TransformerCoupled Front-End for Wideband A/D Converters” (Volume 39, April 2005) at www.analog.com. In general, the precise values depend on the application. 4pF Figure 43. Differential Transformer Coupled Configuration for First and Second Nyquist Frequencies 25Ω MARKI BAL-0006 OR BAL-0006SMG 25Ω 25Ω 0.1µF 0.1µF 25Ω 0.1µF ADC 13059-043 The AD6679 has two analog input channels and 14 LVDS output lane pairs. The AD6679 is designed to sample wide bandwidth analog signals of up to 2 GHz. The AD6679 is optimized for wide input bandwidth, high sampling rates, excellent linearity, and low power in a small package. Figure 44. Differential Transformer Coupled Configuration for Second and Third Nyquist Frequencies Rev. B | Page 30 of 81 Data Sheet AD6679 Input Common Mode 250 The analog inputs of the AD6679 are internally biased to the common mode, as shown in Figure 45. The common-mode buffer has a limited range in that the performance suffers greatly if the common-mode voltage drops by more than 100 mV. Therefore, in dc-coupled applications, set the common-mode voltage to 2.05 V ± 100 mV to ensure proper ADC operation. 230 210 IAVDD3 (mA) 190 170 150 130 110 Analog Input Controls and SFDR Optimization 90 The AD6679 offers flexible controls for the analog inputs such as input termination, buffer current, and input full-scale adjustment. All of the available controls are shown in Figure 45. 50 1.5× AVDD3 2.5× 3.5× 4.5× 5.5× 6.5× 7.5× 8.5× BUFFER CURRENT SETTING 13059-045 70 Figure 46. Typical IAVDD3 vs. Buffer Current Setting in Register 0x018 VIN+x Register 0x019, Register 0x01A, Register 0x11A, and Register 0x935 offer secondary bias controls for the input buffer for frequencies >500 MHz. Use Register 0x934 to reduce input capacitance to achieve wider signal bandwidth but doing so may result in slightly lower linearity and noise performance. These register settings do not affect the AVDD3 power as much as Register 0x018 does. For frequencies <500 MHz, it is recommended to use the default settings for these registers. Table 11 shows the recommended values for the buffer current control registers for various speed grades. VCM BUFFER AVDD3 VIN–x AIN CONTROL (SPI) REGISTERS (REG 0x008, REG 0x015, REG 0x016, REG 0x018, REG 0x025) 13059-044 3pF Figure 45. Analog Input Controls Use Register 0x018, Register 0x019, Register 0x01A, Register 0x11A, Register 0x934, and Register 0x935 to adjust the buffer behavior on each channel to optimize the SFDR over various input frequencies and bandwidths of interest. Input Buffer Control Registers (Register 0x018, Register 0x019, Register 0x01A, Register 0x11A, Register 0x934, Register 0x935) The input buffer has many registers that set the bias currents and other settings for operation at different frequencies. These bias currents and settings can be changed to suit the input frequency range of operation. Register 0x018 controls the buffer bias current to reduce the effects of charge kickback from the ADC core. This setting can be scaled from a low setting of 1.0× to a high setting of 8.5×. The default setting in Register 0x018 is 2.0×. These settings are sufficient for operation in the first Nyquist zone. As the input buffer currents are set, the amount of current required by the AVDD3 supply changes. This relationship is shown in Figure 46. For a complete list of buffer current settings, see Table 41. Register 0x11A can be used when sampling in higher Nyquist zones (>1000 MHz) but is not necessary. Using Register 0x11A can help the ADC sampling network to optimize the sampling and settling times internal to the ADC for high frequency operation. For frequencies greater than 500 MHz, it is recommended to operate the ADC core at a 1.46 V full-scale setting. This setting offers better SFDR without any significant decrease in SNR. Figure 47, Figure 48, and Figure 49 show the SFDR vs. input frequency for various buffer settings for the AD6679. The recommended settings shown in Table 11 were used to collect the data while changing the contents of register 0x018 only. 95 4.5× 85 3.0× 75 2.0× 65 1.5× 55 1.0× 45 35 50 100 150 200 250 300 350 INPUT FREQUENCY (MHz) 400 450 500 13059-046 200Ω 67Ω 28Ω 10pF 200Ω 400Ω SFDR (dBFS) AVDD3 200Ω 67Ω 200Ω 28Ω 3pF Figure 47. Buffer Current Sweeps (SFDR vs. Input Frequency and IBUFF); 10 MHz < fIN < 500 MHz; Front-End Network Shown in Figure 43 Rev. B | Page 31 of 81 AD6679 Data Sheet Absolute Maximum Input Swing 90 VOLTAGE REFERENCE 80 75 65 500 550 600 650 700 750 800 850 900 950 1000 INPUT FREQUENCY (MHz) 13059-047 70 Figure 48. Buffer Current Sweeps (SFDR vs. Input Frequency and IBUFF); 500 MHz < fIN < 1000 MHz; Front-End Network Shown in Figure 44 A stable and accurate 1.0 V voltage reference is built into the AD6679. This internal 1.0 V reference sets the full-scale input range of the ADC. The full-scale input range can be adjusted via Register 0x025. For more information on adjusting the input swing, see Table 41. Figure 50 shows the block diagram of the internal 1.0 V reference controls. VIN+A/ VIN+B VIN–A/ VIN–B 80 INTERNAL V_1P0 GENERATOR 75 FULL-SCALE VOLTAGE ADJUST INPUT FULL-SCALE RANGE ADJUST SPI REGISTER (REG 0x025 AND REG 0x024) 70 V_1P0 65 V_1P0 PIN CONTROL SPI REGISTER (REG 0x025 AND REG 0x024) 60 55 50 4.5× 5.0× 6.0× 7.0× 8.0× 8.0× Figure 50. Internal Reference Configuration and Controls 45 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 INPUT FREQUENCY (MHz) 13059-048 SFDR (dBFS) ADC CORE 13059-049 SFDR (dBFS) The absolute maximum input swing allowed at the inputs of the AD6679 is 4.3 V p-p differential. Signals operating near or at this level can cause permanent damage to the ADC. 4.5× 5.0× 6.0× 7.0× 8.0× 85 Figure 49. Buffer Current Sweeps (SFDR vs. Input Frequency and IBUFF); 1 GHz < fIN < 2 GHz; Front-End Network Shown in Figure 44 Table 11. SFDR Optimization for Input Frequencies Frequency DC to 250 MHz 250 MHz to 500 MHz 500 MHz to 1 GHz 1 GHz to 2 GHz 1 2 Buffer Control 1 (Register 0x018) 0x20 (2.0×) 0x70 (4.5×) 0x80 (5.0×) 0xF0 (8.5×) Buffer Control 2 (Register 0x019) 0x60 (Setting 3) 0x60 (Setting 3) 0x40 (Setting 1) 0x40 (Setting 1) Buffer Control 3 (Register 0x01A) 0x0A (Setting 3) 0x0A (Setting 3) 0x08 (Setting 1) 0x08 (Setting 1) Buffer Control 4 (Register 0x11A) 0x00 (off) Buffer Control 5 (Register 0x935) 0x04 (on) 0x00 (off) 0x04 (on) 0x00 (off) 0x00 (off) 0x00 (off) 0x00 (off) Input FullScale Range (Register 0x025) 0x0C (2.06 V p-p) 0x0C (2.06 V p-p) 0x08 (1.46 V p-p) 0x08 (1.46 V p-p) Input FullScale Control (Register 0x030) 0x04 Input Capacitance (Register 0x934) 0x1F Input Termination (Register 0x016) 1 0x0C/0x1C/0x6C 0x04 0x1F 0x0C/0x1C/0x6C 0x18 0x1F/0x00 2 0x0C/0x1C/0x6C 0x18 0x1F/0x002 0x0C/0x1C/0x6C The input termination can be changed to accommodate the application with little or no impact to ac performance. The input capacitance can be set to 1.5 pF to achieve wider input bandwidth but doing so results in slightly lower ac performance. Rev. B | Page 32 of 81 Data Sheet AD6679 The use of an external reference may be necessary, in some applications, to enhance the gain accuracy of the ADC or improve thermal drift characteristics. Figure 51 shows the typical drift characteristics of the internal 1.0 V reference. 0.1µF CLOCK INPUT 1:1Z CLK+ 100Ω 50Ω 0.1µF Figure 52. Transformer Coupled Differential Clock Another option is to ac couple a differential CML or LVDS signal to the sample clock input pins as shown in Figure 53 and Figure 54. 3.3V 71Ω 1.0010 1.0009 10pF 33Ω Z0 = 50Ω 1.0008 33Ω 0.1µF ADC 1.0006 CLK– Z0 = 50Ω 1.0005 0.1µF 13059-052 CLK+ 1.0007 Figure 53. Differential CML Sample Clock 1.0004 1.0003 1.0002 0.1µF 0.1µF CLK+ CLOCK INPUT 1.0000 0.1µF 0.9999 0 25 90 TEMPERATURE (°C) 13059-050 –50 Figure 51. Typical V_1P0 Drift CLOCK INPUT CONSIDERATIONS For optimum performance, drive the AD6679 sample clock inputs (CLK+ and CLK−) with a differential signal. This signal is typically ac-coupled to the CLK+ and CLK− pins via a transformer or clock drivers. These pins are biased internally and require no additional biasing. Figure 52 shows one preferred method for clocking the AD6679. The low jitter clock source is converted from a singleended signal to a differential signal using an RF transformer. 1 NC 2 GND SET 5 3 VIN CLK– 0.1µF 50Ω1 Clock Duty Cycle Considerations Typical high speed ADCs use both clock edges to generate a variety of internal timing signals. As a result, these ADCs may be sensitive to the clock duty cycle. Commonly, a 5% tolerance is required on the clock duty cycle to maintain dynamic performance characteristics. In applications where the clock duty cycle cannot be guaranteed to be 50%, a higher multiple frequency clock can be supplied to the AD6679. For example, the AD6679 can be clocked at 2 GHz with the internal clock divider set to 4. This ensures a 50% duty cycle, high slew rate internal clock for the ADC. See the Memory Map section for more details on using this feature. FULL-SCALE VOLTAGE ADJUST NC 6 VOUT 4 ADC Figure 54. Differential LVDS Sample Clock INTERNAL V_1P0 GENERATOR ADR130 0.1µF 50Ω1 150Ω RESISTORS ARE OPTIONAL. The external reference must be a stable 1.0 V reference. The ADR130 is a good option for providing the 1.0 V reference. Figure 55 shows how the ADR130 can be used to provide the external 1.0 V reference to the AD6679. The gray areas show unused blocks within the AD6679 while the ADR130 provides the external reference. INPUT 100Ω CLK– CLOCK INPUT 0.9998 CLK+ LVDS DRIVER 13059-053 1.0001 V_1P0 0.1µF FULL-SCALE CONTROL Figure 55. External Reference Using the ADR130 Rev. B | Page 33 of 81 13059-054 V_1P0 VOLTAGE (V) ADC CLK– 13059-051 Register 0x024 enables the user to use either this internal 1.0 V reference, or to provide an external 1.0 V reference. When using an external voltage reference, provide a 1.0 V reference. The full-scale adjustment is made using the SPI, irrespective of the reference voltage. For more information on adjusting the fullscale level of the AD6679, refer to the Memory Map Register Table section. AD6679 Data Sheet Input Clock Divider Clock Jitter Considerations The AD6679 contains an input clock divider with the ability to divide the Nyquist input clock by 1, 2, 4, or 8. The divide ratio can be selected using Register 0x10B. This is shown in Figure 56. The maximum frequency at the output of the divider is 500 MHz. High speed, high resolution ADCs are sensitive to the quality of the clock input. The degradation in SNR at a given input frequency (fA) due only to aperture jitter (tJ) is calculated by The maximum frequency at the CLK± inputs is 4 GHz. This is the limit of the divider. In applications where the clock input is a multiple of the sample clock, take care to program the appropriate divider ratio into the clock divider before applying the clock signal. This ensures that the current transients during device startup are controlled. In this equation, the rms aperture jitter represents the root mean square of all jitter sources, including the clock input, analog input signal, and ADC aperture jitter specifications. IF undersampling applications are particularly sensitive to jitter (see Figure 57). SNR = 20 × log10(2 × π × fA × tJ) 130 RMS CLOCK JITTER REQUIREMENT 120 CLK+ 110 ÷2 100 16 BITS ÷4 90 14 BITS SNR (dB) REG 0x10B 13059-055 ÷8 80 12 BITS 70 10 BITS 60 Figure 56. Clock Divider Circuit 8 BITS 50 The AD6679 clock divider can be synchronized using the external SYNC± input. A valid SYNC± input causes the clock divider to reset to a programmable state. This feature is enabled by setting Bit 7 of Register 0x10D. This synchronization feature allows multiple devices to have their clock dividers aligned to guarantee simultaneous input sampling. After programming the desired clock divider settings, changing the input clock frequency or glitching the input clock a datapath soft reset is recommended by writing 0x02 to Register 0x001. This reset function restarts all the datapath and clock generation circuitry in the device. The reset occurs on the first clock cycle after the register is programmed, and the device requires 5 ms to recover. This reset does not affect the contents of the memory map registers. Input Clock Divider ½ Period Delay Adjustment The input clock divider inside the AD6679 provides phase delay in increments of ½ the input clock cycle. Program Register 0x10C to enable this delay independently for each channel. 40 0.125ps 0.25ps 0.5ps 1.0ps 2.0ps 30 1 10 100 ANALOG INPUT FREQUENCY (MHz) 1000 13059-056 CLK– Figure 57. Ideal SNR vs. Analog Input Frequency and Jitter Treat the clock input as an analog signal when aperture jitter may affect the dynamic range of the AD6679. Separate the power supplies for the clock drivers from the ADC output driver supplies to avoid modulating the clock signal with digital noise. If the clock is generated from another type of source (by gating, dividing, or other methods), retime it using the original clock at the last step. See the AN-501 Application Note and the AN-756 Application Note for more in-depth information about jitter performance as it relates to ADCs. Figure 58 shows the estimated SNR of the AD6679 across input frequency for different clock induced jitter values. Estimate the SNR by using the following equation: Clock Fine Delay Adjustment To adjust the AD6679 sampling edge instant, write to Register 0x117 and Register 0x118. Setting Bit 0 of Register 0x117 enables the fine delay feature, and Register 0x118, Bits[7:0], set the value of the delay. This value can be programmed individually for each channel. The clock delay can be adjusted from −151.7 ps to +150 ps in ~1.7 ps increments. The clock delay adjustment takes effect immediately when it is enabled via SPI writes. Enabling the clock fine delay adjustment in Register 0x117 causes a datapath reset. Rev. B | Page 34 of 81 − SNR JITTER − SNR ADC 10 SNR(dBFS) = 10log 10 + 10 10 Data Sheet AD6679 The temperature diode voltage can be output to the FD_A pin using the SPI. Use Register 0x028, Bit 0, to enable or disable the diode. Register 0x028 is a local register. Channel A must be selected in the device index register (Register 0x008) to enable the temperature diode readout. Configure the FD_A pin to output the diode voltage by programming Register 0x040, Bits[2:0]. See Table 41 for more information. 75 70 25fs 50fs 75fs 100fs 125fs 150fs 175fs 200fs 60 55 The voltage response of the temperature diode (with SPIVDD = 1.8 V) is shown in Figure 59. 0.90 100M 10M 1G 10G INPUT FREQUENCY (Hz) Figure 58. Estimated SNR Degradation for the AD6679 vs. Input Frequency and Jitter POWER-DOWN/STANDBY MODE The AD6679 has a PDWN/STBY pin that configures the device in power-down or standby mode. The default operation is the power-down function. The PDWN/STBY pin is a logic high pin. The power-down option can also be set via Register 0x03F and Register 0x040. TEMPERATURE DIODE VOLTAGE (V) 45 1M 13059-057 50 TEMPERATURE DIODE 0.85 0.80 0.75 0.70 0.65 0.60 –55 –45 –35 –25 –15 –5 5 15 25 35 45 55 65 75 85 95 105 115 125 TEMPERATURE (°C) The AD6679 contains a diode-based temperature sensor for measuring the temperature of the die. This diode can output a voltage and serve as a coarse temperature sensor to monitor the internal die temperature. Rev. B | Page 35 of 81 Figure 59. Temperature Diode Voltage vs. Temperature 13059-058 SNR (dBFS) 65 AD6679 Data Sheet VIRTUAL CONVERTER MAPPING To support the different application layer modes, the AD6679 treats each sample stream (real or I or Q) as originating from separate virtual converters. Table 12 shows the number of virtual converters required for each chip mode. The AD6679 contains a configurable signal path that allows different features to be enabled for different applications. These features are controlled through the chip application mode register (0x200). The chip operating mode is controlled by Bits[3:0] and the Chip Q ignore is controlled by Bit 5. The AD6679 supports up to four digital DDC blocks. Each DDC block outputs either two sample streams (I/Q) for the complex data components (real + imaginary) or one sample stream for real (I) data. The AD6679 can be configured to use up to eight virtual converters depending on the DDC configuration. Figure 60 shows the virtual converters and their relationship to DDC outputs when complex outputs are used. The AD6679 contains the following digital features: • • • • Two analog-to-digital converter (ADC) cores Four digital downconverter (DDC) channels Two noise shaped requantizer (NSR) blocks with optional decimate by two blocks Two variable dynamic range (VDR) blocks Table 12 shows the virtual converter mapping for each chip operating mode when channel swapping is disabled. After the chip application mode has been selected, the output decimation ratio is set using the chip decimation ratio in Register 0x201, Bits[2:0]. The output sample rate is the ADC sample rate divided by the chip decimation ratio. Table 12. Virtual Converter Mapping No. of Virtual Converters Supported 1 Chip Operating Mode (Register 0x200[3:0]) One DDC mode (0x1) 2 One DDC mode (0x1) 2 Two DDC mode (0x2) 4 Two DDC mode (0x2) 4 Four DDC mode (0x3) 8 Four DDC mode (0x3) 1 to 2 NSR mode (0x7) 1 to 2 VDR mode (0x8) 1 Chip Q Ignore (Register 0x200[5]) Real (I only) (0x1) Complex (I/Q) (0x0) Real (I only) (0x1) Complex (I/Q) (0x0) Real (I only) (0x1) Complex (I/Q) (0x0) Real or complex (0x0) Real or complex (0x0) Virtual Converter Mapping1 0 DDC 0 I samples 1 N/A 2 N/A 3 N/A 4 N/A 5 N/A 6 N/A 7 N/A DDC 0 I samples DDC 0 Q samples N/A N/A N/A N/A N/A N/A DDC 0 I samples DDC 1 I samples N/A N/A N/A N/A N/A N/A DDC 0 I samples DDC 0 Q samples DDC 1 I samples DDC 1 Q samples N/A N/A N/A N/A DDC 0 I samples DDC 1 I samples DDC 2 I samples DDC 3 I samples N/A N/A N/A N/A DDC 0 I samples DDC 0 Q samples DDC 1 I samples DDC 1 Q samples DDC 2 I samples DDC 2 Q samples DDC 3 I samples DDC 3 Q samples ADC A samples ADC B samples N/A N/A N/A N/A N/A N/A ADC A samples ADC B samples N/A N/A N/A N/A N/A N/A N/A means not applicable. Rev. B | Page 36 of 81 Data Sheet AD6679 ADC A SAMPLING AT fS REAL/I REAL/Q REAL/I REAL/Q I/Q CROSSBAR MUX REAL/I REAL/Q REAL/Q ADC B SAMPLING AT fS REAL/I REAL/Q DDC 0 I I Q Q DDC 1 I I Q Q DDC 2 I I Q Q DDC 3 I I Q Q REAL/I CONVERTER 0 Q CONVERTER 1 REAL/I CONVERTER 2 Q CONVERTER 3 REAL/I CONVERTER 4 Q CONVERTER 5 REAL/I CONVERTER 6 Q CONVERTER 7 Figure 60. DDCs and Virtual Converter Mapping Rev. B | Page 37 of 81 OUTPUT INTERFACE 13059-159 REAL/I AD6679 Data Sheet ADC OVERRANGE AND FAST DETECT The operation of the upper threshold and lower threshold registers, along with the dwell time registers, is shown in Figure 61. In receiver applications, it is desirable to have a mechanism to reliably determine when the converter is about to be clipped. The standard overrange bit, available via the STATUS±/OVR± pins, provides information on the state of the analog input that is of limited usefulness. Therefore, it is helpful to have a programmable threshold below full scale that allows time to reduce the gain before the clip actually occurs. In addition, because input signals can have significant slew rates, the latency of this function is of major concern. Highly pipelined converters can have significant latency. The AD6679 contains fast detect circuitry for individual channels to monitor the threshold and assert the FD_A and FD_B pins. The FD_x indicator is asserted if the input magnitude exceeds the value programmed in the fast detect upper threshold registers, located in Register 0x247 and Register 0x248. The selected threshold register is compared with the signal magnitude at the output of the ADC. The fast upper threshold detection has a latency of 28 clock cycles. The approximate upper threshold magnitude is defined by Upper Threshold Magnitude (dBFS) = 20log(Threshold Magnitude/213) The FD_x indicators are not cleared until the signal drops below the lower threshold for the programmed dwell time. The lower threshold is programmed in the fast detect lower threshold registers, located in Register 0x249 and Register 0x24A. The fast detect lower threshold register is a 13-bit register that is compared with the signal magnitude at the output of the ADC. This comparison is subject to the ADC pipeline latency but is accurate in terms of converter resolution. The lower threshold magnitude is defined by ADC OVERRANGE (OR) The ADC overrange indicator is asserted when an overrange is detected on the input of the ADC. The overrange indicator can be output via the STATUS± pins. The latency of this overrange indicator matches the sample latency. The AD6679 constantly monitors the analog input level and records any overrange condition in any of the eight virtual converters. For more information on the virtual converters, refer to Figure 63. The overrange status of each virtual converter is registered as a sticky bit (that is, it is set until cleared) in Register 0x563. The contents of Register 0x563 can be cleared using Register 0x562 by toggling the bits corresponding to the virtual converter to set and reset the position. Lower Threshold Magnitude (dBFS) = 20log(Threshold Magnitude/213) For example, to set an upper threshold of −6 dBFS, write 0x0FFF to Register 0x247 and Register 0x248; and to set a lower threshold of −10 dBFS, write 0x0A1D to Register 0x249 and Register 0x24A. FAST THRESHOLD DETECTION (FD_A AND FD_B) The fast detect (FD) bit (enabled in the control bits via Register 0x559) is set whenever the absolute value of the input signal exceeds the programmable upper threshold level. The FD bit is cleared only when the absolute value of the input signal drops below the lower threshold level for greater than the programmable dwell time. This feature provides hysteresis and prevents the FD bit from excessively toggling. The dwell time can be programmed from 1 to 65,535 sample clock cycles by placing the desired value in the fast detect dwell time registers, located in Register 0x24B and Register 0x24C. See the Memory Map section (Register 0x245 to Register 0x24C in Table 41) for more details. UPPER THRESHOLD DWELL TIME TIMER RESET BY RISE ABOVE LOWER THRESHOLD DWELL TIME FD_A OR FD_B Figure 61. Threshold Settings for FD_A and FD_B Signals Rev. B | Page 38 of 81 TIMER COMPLETES BEFORE SIGNAL RISES ABOVE LOWER THRESHOLD 13059-059 MIDSCALE LOWER THRESHOLD Data Sheet AD6679 SIGNAL MONITOR The signal monitor block provides additional information about the signal being digitized by the ADC. The signal monitor computes the peak magnitude of the digitized signal. This information can be used to drive an AGC loop to optimize the range of the ADC in the presence of real-world signals. The results of the signal monitor block can be obtained by reading back the internal values from the SPI port. A global, 24bit programmable period controls the duration of the measurement. Figure 62 shows the simplified block diagram of the signal monitor block. The peak detector captures the largest signal within the observation period. This period observes only the magnitude of the signal. The resolution of the peak detector is a 13-bit value and the observation period is 24 bits and represents converter output samples. The peak magnitude is derived by using the following equation: Peak Magnitude (dBFS) = 20 log(Peak Detector Value/213) The magnitude of the input port signal is monitored over a programmable time period that is determined by the signal monitor period registers (SMPRs). Only even values of the SIGNAL MONITOR PERIOD REGISTER (SMPR) REG 0x271, REG 0x272, REG 0x273 After enabling this mode, the value in the SMPR is loaded into a monitor period timer that decrements at the decimated clock rate. The magnitude of the input signal is compared with the value in the internal magnitude storage register (not accessible to the user), and the greater of the two is updated as the current peak level. The initial value of the magnitude storage register is set to the current ADC input signal magnitude. This comparison continues until the monitor period timer reaches a count of 1. When the monitor period timer reaches a count of 1, the 13-bit peak level value is transferred to the signal monitor holding register, which can be read through the memory map. The monitor period timer is reloaded with the value in the SMPR, and the countdown is restarted. In addition, the magnitude of the first input sample is updated in the internal magnitude storage register, and the comparison and update procedure, as explained previously, continues. DOWN COUNTER IS COUNT = 1? LOAD CLEAR FROM INPUT MAGNITUDE STORAGE REGISTER LOAD LOAD SIGNAL MONITOR HOLDING REGISTER COMPARE A>B Figure 62. Signal Monitor Block Rev. B | Page 39 of 81 TO STATUS± PINS AND MEMORY MAP 13059-060 FROM MEMORY MAP SMPR are supported. The peak detector function is enabled by setting Bit 1 of Register 0x270 in the signal monitor control register. The 24-bit SMPR must be programmed before activating this mode. AD6679 Data Sheet DIGITAL DOWNCONVERTER (DDC) The AD6679 includes four digital downconverters (DDCs) that provide filtering and reduce the output data rate. This digital processing section includes an NCO, up to four half-band decimating filter, a finite impulse response (FIR) filter, a gain stage, and a complex to real conversion stage. Each of these processing blocks has control lines that allow it to be independently enabled and disabled to provide the desired processing function. The DDC can be configured to output either real data or complex output data. DDC I/Q INPUT SELECTION The AD6679 has two ADC channels and four DDC channels. Each DDC channel has two input ports that can be paired to support both real and complex inputs through the I/Q crossbar mux. For real signals, both DDC input ports must select the same ADC channel (that is, DDC Input Port I = ADC Channel A and DDC Input Port Q = ADC Channel A). For complex signals, each DDC input port must select different ADC channels (that is, DDC Input Port I = ADC Channel A and DDC Input Port Q = ADC Channel B). The inputs to each DDC are controlled by the DDC input selection registers (Register 0x311, Register 0x331, Register 0x351, and Register 0x371). See Table 41 for information on how to configure the DDCs. DDC I/Q OUTPUT SELECTION Each DDC channel has two output ports that can be paired to support both real and complex outputs. For real output signals, only the DDC Output Port I is used (the DDC Output Port Q is invalid). For complex I/Q output signals, both DDC Output Port I and DDC Output Port Q are used. The I/Q outputs to each DDC channel are controlled by the DDC complex to real enable bit, Bit 3, in the DDC control registers (Register 0x310, Register 0x330, Register 0x350, and Register 0x370). The Chip Q ignore bit in the chip mode register (Register 0x200, Bit 5) controls the chip output muxing of all the DDC channels. When all DDC channels use real outputs, set this bit high to ignore all DDC Q output ports. When any of the DDC channels are set to use complex I/Q outputs, the user must clear this bit to use both DDC Output Port I and DDC Output Port Q. For more information, see Figure 71. DDC GENERAL DESCRIPTION The four DDC blocks extract a portion of the full digital spectrum captured by the ADC(s). They are intended for IF sampling or oversampled baseband radios requiring wide bandwidth input signals. Each DDC block contains the following signal processing stages: Frequency translation stage (optional) Filtering stage Gain stage (optional) Complex to real conversion stage (optional) Frequency Translation Stage (Optional) This stage consists of a 12-bit complex NCO and quadrature mixers that can be used for frequency translation of both real and complex input signals. This stage shifts a portion of the available digital spectrum down to baseband. Filtering Stage After shifting down to baseband, this stage decimates the frequency spectrum using a chain of up to four half-band lowpass filters for rate conversion. The decimation process lowers the output data rate, which, in turn, reduces the output interface rate. Gain Stage (Optional) Due to losses associated with mixing a real input signal down to baseband, this stage compensates by adding an additional 0 dB or 6 dB of gain. Complex to Real Conversion Stage (Optional) When real outputs are necessary, this stage converts the complex outputs back to real outputs by performing an fS/4 mixing operation together with a filter to remove the complex component of the signal. Figure 63 shows the detailed block diagram of the DDCs implemented in the AD6679. Rev. B | Page 40 of 81 Data Sheet AD6679 GAIN = 0dB OR 6dB COMPLEX TO REAL CONVERSION (OPTIONAL) COMPLEX TO REAL CONVERSION (OPTIONAL) COMPLEX TO REAL CONVERSION (OPTIONAL) COMPLEX TO REAL CONVERSION (OPTIONAL) HB1 FIR DCM = 2 GAIN = 0dB OR 6dB ADC SAMPLING AT fS GAIN = 0dB OR 6dB REAL/I GAIN = 0dB OR 6dB REAL/Q Q HB2 FIR DCM = BYPASS OR 2 NCO + MIXER (OPTIONAL) HB3 FIR DCM = BYPASS OR 2 I HB4 FIR DCM = BYPASS OR 2 DDC 0 REAL/I REAL/I CONVERTER 0 Q CONVERTER 1 SYNC± Q CONVERTER 3 HB1 FIR DCM = 2 SYNC± REAL/Q Q ADC SAMPLING AT fS HB1 FIR DCM = 2 HB2 FIR DCM = BYPASS OR 2 I HB3 FIR DCM = BYPASS OR 2 DDC 2 REAL/I NCO + MIXER (OPTIONAL) REAL/I REAL/I CONVERTER 2 REAL/I CONVERTER 4 OUTPUT INTERFACE REAL/Q Q HB2 FIR DCM = BYPASS OR 2 NCO + MIXER (OPTIONAL) HB3 FIR DCM = BYPASS OR 2 I HB4 FIR DCM = BYPASS OR 2 I/Q CROSSBAR MUX REAL/I HB4 FIR DCM = BYPASS OR 2 DDC 1 Q CONVERTER 5 SYNC± SYNC± SYNCHRONIZATION CONTROL CIRCUITS HB1 FIR DCM = 2 REAL/I CONVERTER 6 Q CONVERTER 7 13059-061 REAL/Q Q HB2 FIR DCM = BYPASS OR 2 NCO + MIXER (OPTIONAL) HB3 FIR DCM = BYPASS OR 2 I HB4 FIR DCM = BYPASS OR 2 DDC 3 REAL/I SYNC Figure 63. DDC Detailed Block Diagram Figure 64 shows an example usage of one of the four DDC blocks with a real input signal and four half-band filters (HB4 + HB3 + HB2 + HB1). It shows both complex (decimate by 16) and real (decimate by 8) output options. When DDCs have different decimation ratios, the chip decimation ratio (Register 0x201) must be set to the lowest decimation ratio of all the DDC blocks. In this scenario, samples of higher decimation ratio DDCs are repeated to match the chip decimation ratio sample rate. Whenever the NCO frequency is set or changed, the DDC soft reset must be issued. If the DDC soft reset is not issued, the output may potentially show amplitude variations. Table 13 through Table 17 show the DDC samples when the chip decimation ratio is set to 1, 2, 4, 8, or 16, respectively. When DDCs have different decimation ratios, the chip decimation ratio must be set to the lowest decimation ratio of all the DDC channels. In this scenario, samples of higher decimation ratio DDCs are repeated to match the chip decimation ratio sample rate. Rev. B | Page 41 of 81 AD6679 Data Sheet ADC ADC SAMPLING AT fS REAL REAL INPUT—SAMPLED AT fS BANDWIDTH OF INTEREST IMAGE –fS/2 –fS/3 –fS/4 REAL BANDWIDTH OF INTEREST –fS/32 fS/32 DC fS/16 –fS/16 –fS/8 FREQUENCY TRANSLATION STAGE (OPTIONAL) DIGITAL MIXER + NCO FOR fS/3 TUNING, THE FREQUENCY TUNING WORD = ROUND ((fS/3)/fS × 4096) = +1365 (0x555) fS/8 fS/4 fS/3 fS/2 I NCO TUNES CENTER OF BANDWIDTH OF INTEREST TO BASEBAND cos(wt) REAL 12-BIT NCO 90° 0° –sin(wt) Q DIGITAL FILTER RESPONSE –fS/2 –fS/3 –fS/4 –fS/32 fS/32 DC fS/16 –fS/16 –fS/8 BANDWIDTH OF INTEREST IMAGE (–6dB LOSS DUE TO NCO + MIXER) BANDWIDTH OF INTEREST (–6dB LOSS DUE TO NCO + MIXER) fS/8 fS/4 fS/3 fS/2 FILTERING STAGE HB4 FIR 4 DIGITAL HALF-BAND FILTERS (HB4 + HB3 + HB2 + HB1) I HALFBAND FILTER Q HALFBAND FILTER HB3 FIR 2 HALFBAND FILTER 2 HALFBAND FILTER HB4 FIR HB2 FIR 2 HALFBAND FILTER 2 HALFBAND FILTER HB3 FIR HB1 FIR 2 HB2 FIR HALFBAND FILTER I HB1 FIR 2 HALFBAND FILTER Q 6dB GAIN TO COMPENSATE FOR NCO + MIXER LOSS COMPLEX (I/Q) OUTPUTS GAIN STAGE (OPTIONAL) DIGITAL FILTER RESPONSE I GAIN STAGE (OPTIONAL) Q 0dB OR 6dB GAIN COMPLEX TO REAL CONVERSION STAGE (OPTIONAL) fS/4 MIXING + COMPLEX FILTER TO REMOVE Q –fS/32 fS/32 DC fS/16 –fS/16 –fS/8 I REAL (I) OUTPUTS +6dB +6dB fS/8 2 +6dB 2 +6dB I Q –fS/32 fS/32 DC –fS/16 fS/16 DOWNSAMPLE BY 2 I DECIMATE BY 8 Q DECIMATE BY 16 0dB OR 6dB GAIN Q COMPLEX REAL/I TO REAL –fS/8 –fS/32 fS/32 DC –fS/16 fS/16 fS/8 Figure 64. DDC Theory of Operation Example (Real Input, Decimate by 16) Rev. B | Page 42 of 81 13059-062 6dB GAIN TO COMPENSATE FOR NCO + MIXER LOSS Data Sheet AD6679 Table 13. DDC Samples When Chip Decimation Ratio = 1 HB1 FIR (DCM 1 = 1) N N+1 N+2 N+3 N+4 N+5 N+6 N+7 N+8 N+9 N + 10 N + 11 N + 12 N + 13 N + 14 N + 15 N + 16 N + 17 N + 18 N + 19 N + 20 N + 21 N + 22 N + 23 N + 24 N + 25 N + 26 N + 27 N + 28 N + 29 N + 30 N + 31 1 Real (I) Output (Complex to Real Enabled) HB3 FIR + HB2 HB4 FIR + HB3 FIR + HB2 FIR + FIR + HB1 FIR HB2 FIR + HB1 FIR HB1 FIR (DCM1 = 4) (DCM1 = 8) (DCM1 = 2) N N N N+1 N+1 N+1 N N N N+1 N+1 N+1 N+2 N N N+3 N+1 N+1 N+2 N N N+3 N+1 N+1 N+4 N+2 N N+5 N+3 N+1 N+4 N+2 N N+5 N+3 N+1 N+6 N+2 N N+7 N+3 N+1 N+6 N+2 N N+7 N+3 N+1 N+8 N+4 N+2 N+9 N+5 N+3 N+8 N+4 N+2 N+9 N+5 N+3 N + 10 N+4 N+2 N + 11 N+5 N+3 N + 10 N+4 N+2 N + 11 N+5 N+3 N + 12 N+6 N+2 N + 13 N+7 N+3 N + 12 N+6 N+2 N + 13 N+7 N+3 N + 14 N+6 N+2 N + 15 N+7 N+3 N + 14 N+6 N+2 N + 15 N+7 N+3 Complex (I/Q) Outputs (Complex to Real Disabled) HB2 FIR + HB3 FIR + HB2 HB4 FIR + HB3 FIR + HB1 FIR HB1 FIR FIR + HB1 FIR HB2 FIR + HB1 FIR (DCM1 = 2) (DCM1 = 4) (DCM1 = 8) (DCM1 = 16) N N N N N+1 N+1 N+1 N+1 N N N N N+1 N+1 N+1 N+1 N+2 N N N N+3 N+1 N+1 N+1 N+2 N N N N+3 N+1 N+1 N+1 N+4 N+2 N N N+5 N+3 N+1 N+1 N+4 N+2 N N N+5 N+3 N+1 N+1 N+6 N+2 N N N+7 N+3 N+1 N+1 N+6 N+2 N N N+7 N+3 N+1 N+1 N+8 N+4 N+2 N N+9 N+5 N+3 N+1 N+8 N+4 N+2 N N+9 N+5 N+3 N+1 N + 10 N+4 N+2 N N + 11 N+5 N+3 N+1 N + 10 N+4 N+2 N N + 11 N+5 N+3 N+1 N + 12 N+6 N+2 N N + 13 N+7 N+3 N+1 N + 12 N+6 N+2 N N + 13 N+7 N+3 N+1 N + 14 N+6 N+2 N N + 15 N+7 N+3 N+1 N + 14 N+6 N+2 N N + 15 N+7 N+3 N+1 DCM means decimation. Table 14. DDC Samples When Chip Decimation Ratio = 2 Real (I) Output (Complex to Real Enabled) HB4 FIR + HB3 FIR + HB3 FIR + HB2 FIR + HB2 FIR + HB2 FIR + HB1 FIR HB1 FIR HB1 FIR (DCM 1 = 2) (DCM1 = 4) (DCM1 = 8) N N N N+1 N+1 N+1 N+2 N N N+3 N+1 N+1 N+4 N+2 N N+5 N+3 N+1 N+6 N+2 N N+7 N+3 N+1 N+8 N+4 N+2 N+9 N+5 N+3 Complex (I/Q) Outputs (Complex to Real Disabled) HB4 FIR + HB3 FIR + HB3 FIR + HB2 FIR + HB2 FIR + HB2 FIR + HB1 FIR HB1 FIR HB1 FIR HB1 FIR (DCM1 = 2) (DCM1 = 4) (DCM1 = 8) (DCM1 = 16) N N N N N+1 N+1 N+1 N+1 N+2 N N N N+3 N+1 N+1 N+1 N+4 N+2 N N N+5 N+3 N+1 N+1 N+6 N+2 N N N+7 N+3 N+1 N+1 N+8 N+4 N+2 N N+9 N+5 N+3 N+1 Rev. B | Page 43 of 81 AD6679 Data Sheet Real (I) Output (Complex to Real Enabled) HB4 FIR + HB3 FIR + HB3 FIR + HB2 FIR + HB2 FIR + HB2 FIR + HB1 FIR HB1 FIR HB1 FIR (DCM 1 = 2) (DCM1 = 4) (DCM1 = 8) N + 10 N+4 N+2 N + 11 N+5 N+3 N + 12 N+6 N+2 N + 13 N+7 N+3 N + 14 N+6 N+2 N + 15 N+7 N+3 1 Complex (I/Q) Outputs (Complex to Real Disabled) HB4 FIR + HB3 FIR + HB3 FIR + HB2 FIR + HB2 FIR + HB2 FIR + HB1 FIR HB1 FIR HB1 FIR HB1 FIR (DCM1 = 2) (DCM1 = 4) (DCM1 = 8) (DCM1 = 16) N + 10 N+4 N+2 N N + 11 N+5 N+3 N+1 N + 12 N+6 N+2 N N + 13 N+7 N+3 N+1 N + 14 N+6 N+2 N N + 15 N+7 N+3 N+1 DCM means decimation. Table 15. DDC Samples When Chip Decimation Ratio = 4 Real (I) Output (Complex to Real Enabled) HB4 FIR + HB3 FIR + HB3 FIR + HB2 FIR + HB2 FIR + HB1 FIR (DCM1 = 8) HB1 FIR (DCM 1 = 4) N N N+1 N+1 N+2 N N+3 N+1 N+4 N+2 N+5 N+3 N+6 N+2 N+7 N+3 1 Complex (I/Q) Outputs (Complex to Real Disabled) HB4 FIR + HB3 FIR + HB2 FIR + HB1 FIR HB3 FIR + HB2 FIR + HB2 FIR + HB1 FIR (DCM1 = 4) HB1 FIR (DCM1 = 8) (DCM1 = 16) N N N N+1 N+1 N+1 N+2 N N N+3 N+1 N+1 N+4 N+2 N N+5 N+3 N+1 N+6 N+2 N N+7 N+3 N+1 DCM means decimation. Table 16. DDC Samples When Chip Decimation Ratio = 8 Real (I) Output (Complex to Real Enabled) Complex (I/Q) Outputs (Complex to Real Disabled) HB3 FIR + HB2 FIR + HB1 FIR HB4 FIR + HB3 FIR + HB2 FIR + (DCM1 = 8) HB1 FIR (DCM1 = 16) N N N+1 N+1 N+2 N N+3 N+1 N+4 N+2 N+5 N+3 N+6 N+2 N+7 N+3 HB4 FIR + HB3 FIR + HB2 FIR + HB1 FIR (DCM 1 = 8) N N+1 N+2 N+3 N+4 N+5 N+6 N+7 1 DCM means decimation. Table 17. DDC Samples When Chip Decimation Ratio = 16 Real (I) Output (Complex to Real Enabled) HB4 FIR + HB3 FIR + HB2 FIR + HB1 FIR (DCM 1 = 16) Not applicable Not applicable Not applicable Not applicable 1 Complex (I/Q) Outputs (Complex to Real Disabled) HB4 FIR + HB3 FIR + HB2 FIR + HB1 FIR (DCM1 = 16) N N+1 N+2 N+3 DCM means decimation. Rev. B | Page 44 of 81 Data Sheet AD6679 For example, if the chip decimation ratio is set to decimate by 4, DDC 0 is set to use HB2 + HB1 filters (complex outputs, decimate by 4) and DDC 1 is set to use HB4 + HB3 + HB2 + HB1 filters (real outputs, decimate by 8). DDC 1 repeats its output data two times for every one DDC 0 output. The resulting output samples are shown in Table 18. Table 18. DDC Output Samples When Chip DCM 1 = 4, DDC 0 DCM1 = 4 (Complex), and DDC 1 DCM1 = 8 (Real) DDC Input Samples N N+1 N+2 N+3 N+4 N+5 N+6 N+7 N+8 N+9 N + 10 N + 11 N + 12 N + 13 N + 14 N + 15 1 Output Port I I0 (N) DDC 0 Output Port Q Q0 (N) I0 (N + 1) Q0 (N + 1) I0 (N + 2) Q0 (N + 2) I0 (N + 3) Q0 (N + 3) DCM means decimation. Rev. B | Page 45 of 81 Output Port I I1 (N) I1 (N + 1) DDC 1 Output Port Q Not applicable Not applicable AD6679 Data Sheet FREQUENCY TRANSLATION GENERAL DESCRIPTION Variable IF Mode Frequency translation is accomplished by using a 12-bit complex NCO with a digital quadrature mixer. This stage translates either a real or complex input signal from an IF to a baseband complex digital output (carrier frequency = 0 Hz). The NCO and the mixers are enabled. The NCO output frequency can be used to digitally tune the IF frequency. 0 Hz IF (ZIF) Mode The mixers are bypassed, and the NCO is disabled. The frequency translation stage of each DDC can be controlled individually and supports four different IF modes using Bits[5:4] of the DDC control registers (Register 0x310, Register 0x330, Register 0x350, and Register 0x370). These IF modes are The mixers and the NCO are enabled in a special downmixing by fS/4 mode to save power. Test Mode Variable IF mode 0 Hz IF, or zero IF (ZIF), mode fS/4 Hz IF mode Test mode The input samples are forced to 0.999 to positive full scale. The NCO is enabled. This test mode allows the NCOs to drive the decimation filters directly. Figure 65 and Figure 66 show examples of the frequency translation stage for both real and complex inputs. NCO FREQUENCY TUNING WORD (FTW) SELECTION 12-BIT NCO FTW = MIXING FREQUENCY/ADC SAMPLE RATE × 4096 I ADC + DIGITAL MIXER + NCO REAL INPUT—SAMPLED AT fS REAL cos(wt) ADC SAMPLING AT fS REAL 12-BIT NCO 90° 0° COMPLEX –sin(wt) Q BANDWIDTH OF INTEREST BANDWIDTH OF INTEREST IMAGE –fS/2 –fS/3 –fS/4 –fS/8 fS/32 –fS/32 DC –fS/16 fS/16 fS/8 fS/4 fS/3 fS/2 –6dB LOSS DUE TO NCO + MIXER 12-BIT NCO FTW = ROUND ((fS/3)/fS × 4096) = +1365 (0x555) POSITIVE FTW VALUES –fS/32 DC fS/32 12-BIT NCO FTW = ROUND ((fS/3)/fS × 4096) = –1365 (0xAAB) –fS/32 NEGATIVE FTW VALUES DC fS/32 Figure 65. DDC NCO Frequency Tuning Word Selection—Real Inputs Rev. B | Page 46 of 81 13059-063 fS/4 Hz IF Mode Data Sheet AD6679 NCO FREQUENCY TUNING WORD (FTW) SELECTION 12-BIT NCO FTW = MIXING FREQUENCY/ADC SAMPLE RATE × 4096 QUADRATURE ANALOG MIXER + 2 ADCs + QUADRATURE DIGITAL REAL MIXER + NCO COMPLEX INPUT—SAMPLED AT fS QUADRATURE MIXER ADC SAMPLING AT fS I + I I Q Q 90° PHASE 12-BIT NCO 90° 0° Q Q ADC SAMPLING AT fS Q Q I I – –sin(wt) I I + COMPLEX Q + BANDWIDTH OF INTEREST IMAGE DUE TO ANALOG I/Q MISMATCH –fS/3 –fS/4 –fS/32 fS/32 –fS/16 fS/16 DC –fS/8 fS/8 fS/4 fS/3 fS/2 12-BIT NCO FTW = ROUND ((fS/3)/fS × 4096) = +1365 (0x555) POSITIVE FTW VALUES –fS/32 fS/32 13059-064 –fS/2 DC Figure 66. DDC NCO Frequency Tuning Word Selection—Complex Inputs DDC NCO PLUS MIXER LOSS AND SFDR Setting Up the NCO FTW and POW When mixing a real input signal down to baseband, 6 dB of loss is introduced in the signal due to filtering of the negative image. The NCO introduces an additional 0.05 dB of loss. The total loss of a real input signal mixed down to baseband is 6.05 dB. For this reason, it is recommended to compensate for this loss by enabling the 6 dB of gain in the gain stage of the DDC to recenter the dynamic range of the signal within the full scale of the output bits. The NCO frequency value is given by the 12-bit, twos complement number entered in the NCO FTW. Frequencies between −fS/2 and +fS/2 (fS/2 excluded) are represented using the following frequency words: When mixing a complex input signal down to baseband, the maximum value each I/Q sample can reach is 1.414 × full scale after it passes through the complex mixer. To avoid an overrange of the I/Q samples and to keep the data bit-widths aligned with real mixing, 3.06 dB of loss is introduced in the mixer for complex signals. The NCO introduces an additional 0.05 dB of loss. The total loss of a complex input signal mixed down to baseband is −3.11 dB. The worst case spurious signal from the NCO is greater than 102 dBc SFDR for all output frequencies. NUMERICALLY CONTROLLED OSCILLATOR The AD6679 has a 12-bit NCO for each DDC that enables the frequency translation process. The NCO allows the input spectrum to be tuned to dc, where it can be effectively filtered by the subsequent filter blocks to prevent aliasing. The NCO can be set up by providing a frequency tuning word (FTW) and a phase offset word (POW). 0x800 represents a frequency of −fS/2. 0x000 represents dc (frequency is 0 Hz). 0x7FF represents a frequency of +fS/2 − fS/212. Calculate the NCO frequency tuning word using the following equation: mod f C , f S NCO _ FTW round 2 12 fS where: NCO_FTW is a 12-bit, twos complement number representing the NCO FTW. fC is the desired carrier frequency in Hz. fS is the AD6679 sampling frequency (clock rate) in Hz. mod( ) is a remainder function. For example, mod(110,100) = 10 and for negative numbers, mod(−32,10) = −2. round( ) is a rounding function. For example, round(3.6) = 4 and for negative numbers, round(−3.4) = −3. Note that this equation applies to the aliasing of signals in the digital domain (that is, aliasing introduced when digitizing analog signals). Rev. B | Page 47 of 81 AD6679 Data Sheet For example, if the ADC sampling frequency (fS) is 500 MSPS and the carrier frequency (fC) is 140.312 MHz, then Use the following two methods to synchronize multiple PAWs within the chip: mod140.312,500 NCO _ FTW round 212 1149 MHz 500 This, in turn, converts to 0x47D in the 12-bit twos complement representation for NCO_FTW. Calculate the actual carrier frequency, fC_ACTUAL, based on the following equation: fC _ ACTUAL NCO_ FTW f S 140.26 MHz 212 A 12-bit POW is available for each NCO to create a known phase relationship between multiple AD6679 chips or individual DDC channels inside one AD6679 chip. The following procedure must be followed to update the FTW and/or POW registers to ensure proper operation of the NCO: 1. 2. 3. Write to the FTW registers for all the DDCs. Write to the POW registers for all the DDCs. Synchronize the NCOs either through the DDC NCO soft reset bit (Register 0x300, Bit 4), accessible through the SPI or through the assertion of the SYNC± pin. It is important to note that the NCOs must be synchronized either through the SPI or through the SYNC± pin after all writes to the FTW or POW registers are complete. This synchronization is necessary to ensure the proper operation of the NCO. NCO Synchronization Each NCO contains a separate phase accumulator word (PAW) that determines the instantaneous phase of the NCO. The initial reset value of each PAW is determined by the POW. The phase increment value of each PAW is determined by the FTW. See the Setting Up the NCO FTW and POW section for more information. Using the SPI. Use the DDC NCO soft reset bit in the DDC synchronization control register (Register 0x300, Bit 4) to reset all the PAWs in the chip. This is accomplished by setting the DDC NCO soft reset bit high and then setting this bit low. Note that this method synchronizes DDC channels within the same AD6679 chip only. Using the SYNC± pins. When the SYNC± pins are enabled in the SYNC± control registers (Register 0x120 and Register 0x121) and the DDC synchronization is enabled in the DDC synchronization control register (Register 0x300, Bits[1:0]), any subsequent SYNC± event resets all the PAWs in the chip. Note that this method synchronizes DDC channels within the same AD6679 chip or DDC channels within separate AD6679 chips. Mixer The NCO is accompanied by a mixer. Its operation is similar to an analog quadrature mixer. It performs the downconversion of input signals (real or complex) by using the NCO frequency as a local oscillator. For real input signals, this mixer performs a real mixer operation (with two multipliers). For complex input signals, the mixer performs a complex mixer operation (with four multipliers and two adders). The mixer adjusts its operation based on the input signal (real or complex) provided to each individual channel. The selection of real or complex inputs can be controlled individually for each DDC block using Bit 7 of the DDC control registers (Register 0x310, Register 0x330, Register 0x350, and Register 0x370). Rev. B | Page 48 of 81 Data Sheet AD6679 FIR FILTERS There are four sets of decimate by 2, low-pass, half-band, FIR filters (labeled HB1 FIR, HB2 FIR, HB3 FIR, and HB4 FIR in Figure 63) following the frequency translation stage. After the carrier of interest is tuned down to dc (carrier frequency = 0 Hz), these filters efficiently lower the sample rate, while providing sufficient alias rejection from unwanted adjacent carriers around the bandwidth of interest. HB1 FIR is always enabled and cannot be bypassed. The HB2, HB3, and HB4 FIR filters are optional and can be bypassed for higher output sample rates. Table 20 shows the different bandwidths selectable by including different half-band filters. In all cases, the DDC filtering stage on the AD6679 provides <−0.001 dB of pass-band ripple and >100 dB of stop band alias rejection. Table 21 shows the amount of stop-band alias rejection for multiple pass-band ripple/cutoff points. The decimation ratio of the filtering stage of each DDC can be controlled individually through Bits[1:0] of the DDC control registers (Register 0x310, Register 0x330, Register 0x350, and Register 0x370). HALF-BAND FILTERS tion that is optimized for low power consumption. The HB4 filter is used only when complex outputs (decimate by 16) or real outputs (decimate by 8) are enabled; otherwise, it is bypassed. Table 19 and Figure 67 show the coefficients and response of the HB4 filter. Table 19. HB4 Filter Coefficients HB4 Coefficient Number C1, C11 C2, C10 C3, C9 C4, C8 C5, C7 C6 Normalized Coefficient 0.006042 0 −0.049316 0 0.293273 0.500000 Decimal Coefficient (15-Bit) 99 0 −808 0 4805 8192 0 –20 MAGNITUDE (dB) OVERVIEW The AD6679 offers four half-band filters to enable digital signal processing of the ADC converted data. These half-band filters are bypassable and can be individually selected. –40 –60 –80 –100 0 0.1 The first decimate by 2, half-band, low-pass, FIR filter (HB4) uses an 11-tap, symmetrical, fixed coefficient filter implementa- 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 NORMALIZED FREQUENCY (× π RAD/SAMPLE) 13059-065 –120 HB4 Filter Figure 67. HB4 Filter Response Table 20. DDC Filter Characteristics ADC Sample Rate (MSPS) 500 1 Half Band Filter Selection HB1 HB1 + HB2 HB1 + HB2 + HB3 HB1 + HB2 + HB3 + HB4 Real Output Output DecimaSample Rate (MSPS) tion Ratio 1 500 2 250 4 125 8 62.5 Complex (I/Q) Output DecimaOutput Sample tion Ratio Rate (MSPS) 2 250 (I) + 250 (Q) 4 125 (I) + 125 (Q) 8 62.5 (I) + 62.5 (Q) 16 31.25 (I) + 31.25 (Q) Alias Protected Bandwidth (MHz) 192.5 96.3 48.1 24.1 Ideal SNR Improvement 1 (dB) 1 4 7 10 PassBand Ripple (dB) <−0.001 Alias Rejection (dB) >100 Ideal SNR improvement due to oversampling and filtering = 10log(bandwidth/(fS/2)). Table 21. DDC Filter Alias Rejection Alias Rejection (dB) >100 90 85 63.3 25 19.3 10.7 1 Pass-Band Ripple/Cutoff Point (dB) <−0.001 <−0.001 <−0.001 <−0.006 −0.5 −1.0 −3.0 Alias Protected Bandwidth for Real (I) Outputs 1 <38.5% × fOUT <38.7% × fOUT <38.9% × fOUT <40% × fOUT 44.4% × fOUT 45.6% × fOUT 48% × fOUT fOUT = ADC input sample rate ÷ DDC decimation. Rev. B | Page 49 of 81 Alias Protected Bandwidth for Complex (I/Q) Outputs <77% × fOUT <77.4% × fOUT <77.8% × fOUT <80% × fOUT 88.8% × fOUT 91.2% × fOUT 96% × fOUT AD6679 Data Sheet HB3 Filter 0 –20 MAGNITUDE (dB) The second decimate by 2, half-band, low-pass, FIR filter (HB3) uses an 11-tap, symmetrical, fixed coefficient filter implementation that is optimized for low power consumption. The HB3 filter is only used when complex outputs (decimate by 8 or 16) or real outputs (decimate by 4 or 8) are enabled; otherwise, it is bypassed. Table 22 and Figure 68 show the coefficients and response of the HB3 filter. Table 22. HB3 Filter Coefficients –80 –100 Normalized Coefficient 0.006554 0 −0.050819 0 0.294266 0.500000 Decimal Coefficient (18-Bit) 859 0 −6661 0 38,570 65,536 0 –20 MAGNITUDE (dB) –60 –40 –120 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 NORMALIZED FREQUENCY (× π RAD/SAMPLE) 13059-067 HB3 Coefficient Number C1, C11 C2, C10 C3, C9 C4, C8 C5, C7 C6 –40 Figure 69. HB2 Filter Response HB1 Filter The fourth and final decimate by 2, half-band, low-pass, FIR filter (HB1) uses a 55-tap, symmetrical, fixed coefficient filter implementation that is optimized for low power consumption. The HB1 filter is always enabled and cannot be bypassed. Table 24 and Figure 70 show the coefficients and response of the HB1 filter. Table 24. HB1 Filter Coefficients –60 –80 –100 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 NORMALIZED FREQUENCY (× π RAD/SAMPLE) 13059-066 –120 Figure 68. HB3 Filter Response HB2 Filter The third decimate by 2, half-band, low-pass, FIR filter (HB2) uses a 19-tap, symmetrical, fixed coefficient filter implementation that is optimized for low power consumption. The HB2 filter is only used when complex or real outputs (decimate by 4, 8, or 16) are enabled; otherwise, it is bypassed. Table 23 and Figure 69 show the coefficients and response of the HB2 filter. Table 23. HB2 Filter Coefficients HB2 Coefficient Number C1, C19 C2, C18 C3, C17 C4, C16 C5, C15 C6, C14 C7, C13 C8, C12 C9, C11 C10 Normalized Coefficient 0.000614 0 −0.005066 0 0.022179 0 −0.073517 0 0.305786 0.500000 Decimal Coefficient (19-Bit) 161 0 −1328 0 5814 0 −19,272 0 80,160 131,072 HB1 Coefficient Number C1, C55 C2, C54 C3, C53 C4, C52 C5, C51 C6, C50 C7, C49 C8, C48 C9, C47 C10, C46 C11, C45 C12, C44 C13, C43 C14, C42 C15, C41 C16, C40 C17, C39 C18, C38 C19, C37 C20, C36 C21, C35 C22, C34 C23, C33 C24, C32 C25, C31 C26, C30 C27, C29 C28 Rev. B | Page 50 of 81 Normalized Coefficient −0.000023 0 0.000097 0 −0.000288 0 0.000696 0 −0.0014725 0 0.002827 0 −0.005039 0 0.008491 0 −0.013717 0 0.021591 0 −0.033833 0 0.054806 0 −0.100557 0 0.316421 0.500000 Decimal Coefficient (21-Bit) −24 0 102 0 −302 0 730 0 −1544 0 2964 0 −5284 0 8903 0 −14,383 0 22,640 0 −35,476 0 57,468 0 −105,442 0 331,792 524,288 Data Sheet AD6679 DDC GAIN STAGE 0 Each DDC contains an independently controlled gain stage. The gain is selectable as either 0 dB or 6 dB. When mixing a real input signal down to baseband, it is recommended that the user enable the 6 dB of gain to recenter the dynamic range of the signal within the full scale of the output bits. –40 –60 When mixing a complex input signal down to baseband, the mixer has already recentered the dynamic range of the signal within the full scale of the output bits, and no additional gain is necessary. However, the optional 6 dB gain compensates for low signal strengths. The downsample by 2 portion of the HB1 FIR filter is bypassed when using the complex to real conversion stage. –80 –100 –120 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 NORMALIZED FREQUENCY (× π RAD/SAMPLE) DDC COMPLEX TO REAL CONVERSION Figure 70. HB1 Filter Response Each DDC contains an independently controlled complex to real conversion block. The complex to real conversion block reuses the last filter (HB1 FIR) in the filtering stage along with an fS/4 complex mixer to upconvert the signal. After upconverting the signal, the Q portion of the complex mixer is no longer needed and is dropped. Figure 71 shows a simplified block diagram of the complex to real conversion. GAIN STAGE HB1 FIR COMPLEX TO REAL ENABLE LOW-PASS FILTER I 2 0dB OR 6dB I 0 I/REAL 1 COMPLEX TO REAL CONVERSION 0dB OR 6dB I cos(wt) + REAL 90° fS/4 0° – sin(wt) Q LOW-PASS FILTER 2 0dB OR 6dB Q 0dB OR 6dB Q Q 13059-069 0 13059-068 MAGNITUDE (dB) –20 HB1 FIR Figure 71. Complex to Real Conversion Block Rev. B | Page 51 of 81 AD6679 Data Sheet DDC EXAMPLE CONFIGURATIONS Table 25 describes the register settings for multiple DDC example configurations. Table 25. DDC Example Configurations Chip Application Layer One DDC Chip Decimation Ratio 2 DDC Input Type Complex DDC Output Type Complex Bandwidth Per DDC 1 38.5% × fS No. of Virtual Converters Required 2 One DDC 4 Complex Complex 19.25% × fS 2 Two DDCs 2 Real Real 19.25%× fS 2 Two DDCs 2 Complex Complex 38.5%× fS 4 Rev. B | Page 52 of 81 Register Settings 2 Register 0x200 = 0x01 (one DDC; I/Q selected) Register 0x201 = 0x01 (chip decimate by 2) Register 0x310 = 0x83 (complex mixer, 0 dB gain, variable IF, complex outputs, HB1 filter) Register 0x311 = 0x04 (DDC I input = ADC Channel A, DDC Q input = ADC Channel B) Register 0x314, Register 0x315, Register 0x320, Register 0x321 = FTW and POW set as required by application for DDC 0 Register 0x200 = 0x01 (one DDC, I/Q selected) Register 0x201 = 0x02 (chip decimate by 4) Register 0x310= 0x80 (complex mixer, 0 dB gain, variable IF, complex outputs, HB2 + HB1 filters) Register 0x311 = 0x04 (DDC I input = ADC Channel A, DDC Q input = ADC Channel B) Register 0x314, Register 0x315= FTW and POW set as required by application for DDC 0 Register 0x200 = 0x22 (two DDCs, I only selected) Register 0x201 = 0x01 (chip decimate by 2) Register 0x310, Register 0x330 = 0x48 (real mixer, 6 dB gain, variable IF, real output, HB2 + HB1 filters) Register 0x311 = 0x00 (DDC 0 I input = ADC Channel A, DDC 0 Q input = ADC Channel A) Register 0x331 = 0x05 (DDC 1 I input = ADC Channel B, DDC 1 Q input = ADC Channel B) Register 0x314, Register 0x315, Register 0x320, Register 0x321 = FTW and POW set as required by application for DDC 0 Register 0x334, Register 0x335, Register 0x340, Register 0x341 = FTW and POW set as required by application for DDC 1 Register 0x200 = 0x22 (two DDCs, I only selected) Register 0x201 = 0x01 (chip decimate by 2) Register 0x310, Register 0x330 = 0x4B (complex mixer, 6 dB gain, variable IF, complex output, HB1 filter) Register 0x311, Register 0x331 = 0x04 (DDC 0 I input = ADC Channel A, DDC 0 Q input = ADC Channel B) Register 0x314, Register 0x315, Register 0x320, Register 0x321 = FTW and POW set as required by application for DDC 0 Register 0x334, Register 0x335, Register 0x340, Register 0x341 = FTW and POW set as required by application for DDC 1 Data Sheet AD6679 Chip Application Layer Two DDCs Chip Decimation Ratio 4 DDC Input Type Complex DDC Output Type Complex Bandwidth Per DDC 1 19.25% × fS No. of Virtual Converters Required 4 Two DDCs 4 Complex Real 9.63% × fS 2 Two DDCs 4 Real Real 9.63% × fS 2 Two DDCs 4 Real Complex 19.25% × fS 4 Rev. B | Page 53 of 81 Register Settings 2 Register 0x200 = 0x02 (two DDCs, I/Q selected) Register 0x201 = 0x02 (chip decimate by 4) Register 0x310, Register 0x330 = 0x80 (complex mixer, 0 dB gain, variable IF, complex outputs, HB2 + HB1 filters) Register 0x311, Register 0x331 = 0x04 (DDC I input = ADC Channel A, DDC Q input = ADC Channel B) Register 0x314, Register 0x315, Register 0x320, Register 0x321 = FTW and POW set as required by application for DDC 0 Register 0x334, Register 0x335, Register 0x340, Register 0x341 = FTW and POW set as required by application for DDC 1 Register 0x200 = 0x22 (two DDCs, I only selected) Register 0x201 = 0x02 (chip decimate by 4) Register 0x310, Register 0x330 = 0x89 (complex mixer, 0 dB gain, variable IF, real output, HB3 + HB2 + HB1 filters) Register 0x311, Register 0x331 = 0x04 (DDC I input = ADC Channel A, DDC Q input = ADC Channel B) Register 0x314, Register 0x315, Register 0x320, Register 0x321 = FTW and POW set as required by application for DDC 0 Register 0x334, Register 0x335, Register 0x340, Register 0x341 = FTW and POW set as required by application for DDC 1 Register 0x200 = 0x22 (two DDCs, I only selected) Register 0x201 = 0x02 (chip decimate by 4) Register 0x310, Register 0x330 = 0x49 (real mixer, 6 dB gain, variable IF, real output, HB3 + HB2 + HB1 filters) Register 0x311 = 0x00 (DDC 0 I input = ADC Channel A, DDC 0 Q input = ADC Channel A) Register 0x331 = 0x05 (DDC 1 I input = ADC Channel B, DDC 1 Q input = ADC Channel B) Register 0x314, Register 0x315, Register 0x320, Register 0x321 = FTW and POW set as required by application for DDC 0 Register 0x334, Register 0x335, Register 0x340, Register 0x341 = FTW and POW set as required by application for DDC 1 Register 0x200 = 0x02 (two DDCs, I/Q selected) Register 0x201 = 0x02 (chip decimate by 4) Register 0x310, Register 0x330 = 0x40 (real mixer, 6 dB gain, variable IF, complex output, HB2 + HB1 filters) Register 0x311 = 0x00 (DDC 0 I input = ADC Channel A, DDC 0 Q input = ADC Channel A) Register 0x331 = 0x05 (DDC 1 I input = ADC Channel B, DDC 1 Q input = ADC Channel B) Register 0x314, Register 0x315, Register 0x320, Register 0x321 = FTW and POW set as required by application for DDC 0 Register 0x334, Register 0x335, Register 0x340, Register 0x341 = FTW and POW set as required by application for DDC 1 AD6679 Data Sheet Chip Application Layer Two DDCs Chip Decimation Ratio 8 DDC Input Type Real DDC Output Type Real Bandwidth Per DDC 1 4.81% × fS No. of Virtual Converters Required 2 Four DDCs 8 Real Complex 9.63% × fS 8 Four DDCs 8 Real Real 4.81% × fS 4 Rev. B | Page 54 of 81 Register Settings 2 Register 0x200 = 0x22 (two DDCs, I only selected) Register 0x201 = 0x03 (chip decimate by 8) Register 0x310, Register 0x330 = 0x4A (real mixer, 6 dB gain, variable IF, real output, HB4 + HB3 + HB2 + HB1 filters) Register 0x311 = 0x00 (DDC 0 I input = ADC Channel A, DDC 0 Q input = ADC Channel A) Register 0x331 = 0x05 (DDC 1 I input = ADC Channel B, DDC 1 Q input = ADC Channel B) Register 0x314, Register 0x315, Register 0x320, Register 0x321 = FTW and POW set as required by application for DDC 0 Register 0x334, Register 0x335, Register 0x340, Register 0x341 = FTW and POW set as required by application for DDC 1 Register 0x200 = 0x03 (four DDCs, I/Q selected) Register 0x201 = 0x03 (chip decimate by 8) Register 0x310, Register 0x330, Register 0x350, Register 0x370 = 0x41 (real mixer, 6 dB gain, variable IF, complex output, HB3 + HB2 + HB1 filters) Register 0x311 = 0x00 (DDC 0 I input = ADC Channel A, DDC 0 Q input = ADC Channel A) Register 0x331 = 0x00 (DDC 1 I input = ADC Channel A, DDC 1 Q input = ADC Channel A) Register 0x351 = 0x05 (DDC 2 I input = ADC Channel B, DDC 2 Q input = ADC Channel B) Register 0x371 = 0x05 (DDC 3 I input = ADC Channel B, DDC 3 Q input = ADC Channel B) Register 0x314, Register 0x315, Register 0x320, Register 0x321 = FTW and POW set as required by application for DDC 0 Register 0x334, Register 0x335, Register 0x340, Register 0x341 = FTW and POW set as required by application for DDC 1 Register 0x354, Register 0x355, Register 0x360, Register 0x361 = FTW and POW set as required by application for DDC 2 Register 0x374, Register 0x375, Register 0x380, Register 0x381 = FTW and POW set as required by application for DDC 3 Register 0x200 = 0x23 (four DDCs, I only selected) Register 0x201 = 0x03 (chip decimate by 8) Register 0x310, Register 0x330, Register 0x350, Register 0x370 = 0x4A (real mixer, 6 dB gain, variable IF, real output, HB4 + HB3 + HB2 + HB1 filters) Register 0x311 = 0x00 (DDC 0 I input = ADC Channel A, DDC 0 Q input = ADC Channel A) Register 0x331 = 0x00 (DDC 1 I input = ADC Channel A, DDC 1 Q input = ADC Channel A) Register 0x351 = 0x05 (DDC 2 I input = ADC Channel B, DDC 2 Q input = ADC Channel B) Register 0x371 = 0x05 (DDC 3 I input = ADC Channel B, DDC 3 Q input = ADC Channel B) Data Sheet AD6679 Chip Application Layer Chip Decimation Ratio DDC Input Type DDC Output Type Bandwidth Per DDC 1 No. of Virtual Converters Required Four DDCs 16 Real Complex 4.81% × fS 8 1 2 Register Settings 2 Register 0x314, Register 0x315, Register 0x320, Register 0x321 = FTW and POW set as required by application for DDC 0 Register 0x334, Register 0x335, Register 0x340, Register 0x341 = FTW and POW set as required by application for DDC 1 Register 0x354, Register 0x355, Register 0x360, Register 0x361 = FTW and POW set as required by application for DDC 2 Register 0x374, Register 0x375, Register 0x380, Register 0x381 = FTW and POW set as required by application for DDC 3 Register 0x200 = 0x03 (four DDCs, I/Q selected) Register 0x201 = 0x04 (chip decimate by 16) Register 0x310, Register 0x330, Register 0x350, Register 0x370 = 0x42 (real mixer, 6 dB gain, variable IF, complex output, HB4 + HB3 + HB2 + HB1 filters) Register 0x311 = 0x00 (DDC 0 I input = ADC Channel A, DDC 0 Q input = ADC Channel A) Register 0x331 = 0x00 (DDC 1 I input = ADC Channel A, DDC 1 Q input = ADC Channel A) Register 0x351 = 0x05 (DDC 2 I input = ADC Channel B, DDC 2 Q input = ADC Channel B) Register 0x371 = 0x05 (DDC 3 I input = ADC Channel B, DDC 3 Q input = ADC Channel B) Register 0x314, Register 0x315, Register 0x320, Register 0x321 = FTW and POW set as required by application for DDC 0 Register 0x334, Register 0x335, Register 0x040, Register 0x341 = FTW and POW set as required by application for DDC 1 Register 0x354, Register 0x355, Register 0x360, Register 0x361 = FTW and POW set as required by application for DDC 2 Register 0x374, Register 0x375, Register 0x380, Register 0x381 = FTW and POW set as required by application for DDC 3 fS is the ADC sample rate. Bandwidths listed are <−0.001 dB of pass-band ripple and >100 dB of stop band alias rejection. The NCOs must be synchronized either through the SPI or through the SYNC± pins after all writes to the FTW or POW registers are complete. This is necessary to ensure the proper operation of the NCO. See the NCO Synchronization section for more information. Rev. B | Page 55 of 81 AD6679 Data Sheet NOISE SHAPING REQUANTIZER (NSR) 10 0 –10 MAGNITUDE (dB) –40 –50 The 19-tap, symmetrical, fixed-coefficient half-band filter has low power consumption due to its polyphase implementation. Table 26 lists the coefficients of the half-band filter in low-pass mode. In high-pass mode, Coefficient C9 is multiplied by −1. The normalized coefficients used in the implementation and the decimal equivalent values of the coefficients are listed. Coefficients not listed in Table 26 are 0s. Table 26. Fixed Coefficients for Half-Band Filter Decimal Coefficient (12-Bit) 25 −47 93 −194 644 1024 0.05 0.10 0.150 0.20 0.25 0.30 0.35 0.40 0.45 NORMALIZED FREQUENCY (× RAD/SAMPLE) 0.50 Figure 72. Low-Pass Half-Band Filter Response The half-band filter can also be utilized in high-pass mode. The usable bandwidth remains at 39.5% of the output sample rate (19.75% of the input sample clock), which is the same as in lowpass mode). Figure 73 shows the normalized response of the half-band filter in high-pass mode. In high-pass mode, operation is allowed in the second and third Nyquist zones, which includes frequencies from fS/2 to 3fS/2, where fS is the decimated sample rate. For example, with an input clock of 500 MHz, the output sample rate is 250 MSPS, fS/2 = 125 MHz, and 3fS/2 = 375 MHz. 10 0 –10 MAGNITUDE (dB) Half-Band Filter Coefficients 0 13059-070 –70 –80 The AD6679 optional decimating half-band filter reduces the input sample rate by a factor of 2 while rejecting aliases that fall into the band of interest. For an input sample clock of 500 MHz, this reduces the output sample rate to 250 MSPS. This filter is designed to provide >40 dB of alias protection for 39.5% of the output sample rate (79% of the Nyquist band). For an ADC sample rate of 500 MSPS, the filter provides a maximum usable bandwidth of 98.75 MHz. Normalized Coefficient 0.012207 −0.022949 0.045410 −0.094726 0.314453 0.500000 –30 –60 DECIMATING HALF-BAND FILTER Coefficient Number 0 C2, C16 C4, C14 C6, C12 C8, C10 C9 –20 –20 –30 –40 –50 –60 –70 –80 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 NORMALIZED FREQUENCY (× π RAD/SAMPLE) 1.0 13059-071 When operating the AD6679 with the NSR enabled, a decimating half-band filter that is optimized at certain input frequency bands can also be enabled. This filter offers the user the flexibility in signal bandwidth process and image rejection. Careful frequency planning can offer advantages in analog filtering preceding the ADC. The filter can function either in high-pass or low-pass mode. The filter can be optionally enabled on the AD6679 when the NSR is enabled. When operating with NSR enabled, the decimating half-band filter mode (low pass or high pass) is selected by setting Bit 7 in Register 0x41E. Figure 73. High-Pass Half-Band Filter Response Half-Band Filter Features NSR OVERVIEW The half-band decimating filter provides approximately 39.5% of the output sample rate in usable bandwidth (19.75% of the input sample clock). The filter provides >40 dB of rejection. The normalized response of the half-band filter in low-pass mode is shown in Figure 72. In low-pass mode, operation is allowed in the first Nyquist zone, which includes frequencies of up to fS/2, where fS is the decimated sample rate. For example, with an input clock of 500 MHz, the output sample rate is 250 MSPS and fS/2 = 125 MHz. The AD6679 features an NSR to allow higher than 9-bit SNR to be maintained in a subset of the Nyquist band. The harmonic performance of the receiver is unaffected by the NSR feature. When enabled, the NSR contributes an additional 3.0 dB of loss to the input signal, such that a 0 dBFS input is reduced to −3.0 dBFS at the output pins. This loss does not degrade the SNR performance of the AD6679. The NSR feature can be independently controlled per channel via the SPI. Two different bandwidth modes are provided; select the mode from the SPI port. In each of the two modes, the center frequency Rev. B | Page 56 of 81 Data Sheet AD6679 –40 The first NSR mode offers excellent noise performance across a bandwidth that is 21% of the ADC output sample rate (42% of the Nyquist band) and can be centered by setting the NSR mode bits in the NSR mode register (Address 0x420) to 000. In this mode, the useful frequency range can be set using the 6-bit tuning word in the NSR tuning register (Address 0x422). There are 59 possible tuning words (TW), from 0 to 58; each step is 0.5% of the ADC sample rate. The following three equations describe the left band edge (f0), the channel center (fCENTER), and the right band edge (f1), respectively: fCENTER = f0 + 0.105 × fADC f1 = f0 + 0.21 × fADC Figure 74 to Figure 76 show the typical spectrum that can be expected from the AD6679 in the 21% BW mode for three different tuning words. –60 –80 –100 –120 –140 0 25 50 75 100 125 150 175 200 225 250 FREQUENCY (MHz) Figure 75. 21% BW Mode, Tuning Word = 26 (fS/4 Tuning) 0 AIN = −1dBFS SNR = 74.9dBFS ENOB = 11.6 BITS SFDR = 90dBFS BUFFER CONTROL 1 = 2.0× –20 –40 AMPLITUDE (dBFS) f0 = fADC × 0.005 × TW AIN = −1dBFS SNR = 75.0dBFS ENOB = 11.6 BITS SFDR = 85dBFS BUFFER CONTROL 1 = 2.0× –20 13059-073 21% BW Mode (>100 MHz at 491.52 MSPS) 0 AMPLITUDE (dBFS) of the band can be tuned such that IFs can be placed anywhere in the Nyquist band. The NSR feature is enabled by default on the AD6679. The bandwidth and mode of the NSR operation are selected by setting the appropriate bits in Register 0x420 and Register 0x422. By selecting the appropriate profile and mode bits in these two registers, the NSR feature can be enabled for the desired mode of operation. –60 –80 –100 –120 AIN = −1dBFS SNR = 75.2dBFS ENOB = 11.6 BITS SFDR = 87dBFS BUFFER CONTROL 1 = 2.0× –20 –140 0 50 75 100 125 150 175 200 FREQUENCY (MHz) 225 250 Figure 76. 21% BW Mode, Tuning Word = 58 –40 28% BW Mode (>130 MHz at 491.52 MSPS) –60 –80 –100 –120 –140 0 25 50 75 100 125 150 175 200 FREQUENCY (MHz) Figure 74. 21% BW Mode, Tuning Word = 0 225 250 13059-072 AMPLITUDE (dBFS) 25 13059-074 0 The second NSR mode offers excellent noise performance across a bandwidth that is 28% of the ADC output sample rate (56% of the Nyquist band) and can be centered by setting the NSR mode bits in the NSR mode register (Address 0x420) to 001. In this mode, the useful frequency range can be set using the 6-bit tuning word in the NSR tuning register (Address 0x422). There are 44 possible tuning words (TW, from 0 to 43); each step is 0.5% of the ADC sample rate. The following three equations describe the left band edge (f0), the channel center (fCENTER), and the right band edge (f1), respectively: f0 = fADC × 0.005 × TW fCENTER = f0 + 0.14 × fADC f1 = f0 + 0.28 × fADC Figure 77 to Figure 79 show the typical spectrum that can be expected from the AD6679 in the 28% BW mode for three different tuning words. Rev. B | Page 57 of 81 AD6679 Data Sheet 0 0 AIN = −1dBFS SNR = 72.5dBFS ENOB = 11.2 BITS SFDR = 86dBFS BUFFER CONTROL 1 = 2.0× –20 –40 AMPLITUDE (dBFS) –60 –80 –100 –80 –100 –120 –140 0 25 50 75 100 125 150 175 200 225 250 FREQUENCY (MHz) 13059-075 –120 –60 Figure 77. 28% BW Mode, Tuning Word = 0 AIN = −1dBFS SNR = 71.7dBFS ENOB = 11.1 BITS SFDR = 85dBFS BUFFER CONTROL 1 = 2.0× –40 –60 –80 –100 –140 25 50 75 100 125 150 175 200 225 FREQUENCY (MHz) 250 13059-076 –120 0 0 25 50 75 100 125 150 175 200 FREQUENCY (MHz) Figure 79. 28% BW Mode, Tuning Word = 43 0 –20 –140 Figure 78. 28% BW Mode, Tuning Word = 19 (fS/4 Tuning) Rev. B | Page 58 of 81 225 250 13059-077 AMPLITUDE (dBFS) –40 AMPLITUDE (dBFS) AIN = −1dBFS SNR = 71.6dBFS ENOB = 11.1 BITS SFDR = 90dBFS BUFFER CONTROL 1 = 2.0× –20 Data Sheet AD6679 VARIABLE DYNAMIC RANGE (VDR) The AD6679 features a variable dynamic range (VDR) digital processing block to allow up to 14-bit dynamic range to be maintained in a subset of the Nyquist band. Across the full Nyquist band, a minimum of a 9-bit dynamic range is available at all times. This operation is suitable for applications such as digital predistortion processing (DPD). The harmonic performance of the receiver is unaffected by this feature. When enabled, VDR does not contribute loss to the input signal but operates by effectively changing the output resolution at the output pins. This feature can be independently controlled per channel via the SPI. Table 27. VDR Reduced Output Resolution Values VDR Punish Bit 0 1 Not applicable Not applicable The VDR block operates in either complex or real mode. In complex mode, VDR has selectable bandwidths of 25% and 43% of the output sample rate. In real mode, the bandwidth of operation is limited to 25% of the output sample rate. The bandwidth and mode of the VDR operation are selected by setting the appropriate bits in Register 0x430. When the VDR block is enabled, input signals that violate a defined mask (signified by gray shaded areas in Figure 80) result in the reduction of the output resolution of the AD6679. The VDR block analyzes the peak value of the aggregate signal level in the disallowed zones to determine the reduction of the output resolution. To indicate that the AD6679 is reducing output, the VDR punish bit or a VDR high/low resolution bit can optionally be on the STATUS±/OVR± pins by programming the appropriate value into Register 0x559. The VDR high/low resolution bit can alternatively be programmed to output on the STATUS± pins and simply indicates if VDR is reducing output resolution (bit value is a 1), or if full resolution is available (bit value is a 0). These VDR high/low resolution and VDR punish bits can be decoded by using Table 27. Note that only one can be output at a given time. VDR High/Low Resolution Bit Not applicable Not applicable 0 1 Output Resolution (Bits) 14 or 13 ≤12 14 ≤13 The frequency zones of the mask are defined by the bandwidth mode selected in Register 0x430. The upper amplitude limit for input signals located in these frequency zones is −30 dBFS. If the input signal level in the disallowed frequency zones goes above an amplitude level of −30 dBFS (into the gray shaded areas), the VDR block triggers a reduction in the output resolution, as shown in Figure 80. The VDR block engages and begins limiting output resolution gradually as the signal amplitudes increase in the mask regions. As the signal amplitude level increases into the mask regions, the output resolution is gradually lowered. For every 6 dB increase in signal level above −30 dBFS, one bit of output resolution is discarded from the output data by the VDR block, as shown in Table 28. These zones can be tuned within the Nyquist band by setting Bits[3:0] in Register 0x434 to determine the VDR center frequency (fVDR). The VDR center frequency in complex mode can be adjusted from 1/16 fS to 15/16 fS in 1/16 fS steps. In real mode, fVDR can be adjusted from 1/8 fS to 3/8 fS in 1/16 fS steps. Table 28. VDR Reduced Output Resolution Values Signal Amplitude Violating Defined VDR Mask Amplitude ≤ −30 dBFS −30 dBFS < amplitude ≤ −24 dBFS −24 dBFS < amplitude ≤ −18 dBFS −18 dBFS < amplitude ≤ −12 dBFS −12 dBFS < amplitude ≤ −6 dBFS −6 dBFS < amplitude ≤ 0 dBFS Output Resolution (Bits) 14 13 12 11 10 9 dBFS 0 fS 0 INTERMODULATION PRODUCTS < –30dBFS fS INTERMODULATION PRODUCTS > –30dBFS Figure 80. VDR Operation—Reduction in Output Resolution Rev. B | Page 59 of 81 13059-078 –30 AD6679 Data Sheet VDR REAL MODE VDR COMPLEX MODE The real mode of VDR works over a bandwidth of 25% of the sample rate (50% of the Nyquist band). The output bandwidth of the AD6679 can be 25% only when operating in real mode. Figure 81 shows the frequency zones for the 25% bandwidth real output VDR mode tuned to a center frequency (fVDR) of fS/4 (tuning word = 0x04). The frequency zones where the amplitude may not exceed −30 dBFS are the upper and lower portions of the Nyquist band signified by the red shaded areas. The complex mode of VDR works with selectable bandwidths of 25% of the sample rate (50% of the Nyquist band) and 43% of the sample rate (86% of the Nyquist band). Figure 82 and Figure 83 show the frequency zones for VDR in the complex mode. When operating VDR in complex mode, place in-phase (I) input signal data in Channel A and place quadrature (Q) signal data in Channel B. dBFS Figure 82 shows the frequency zones for the 25% bandwidth VDR mode with a center frequency of fS/4 (tuning word = 0x04). The frequency zones where the amplitude may not exceed −30 dBFS are the upper and lower portions of the Nyquist band extending into the complex domain. dBFS –30 0 0 1/8 fS 3/8 fS 1/2 fS 13059-079 –1/2 fS The center frequency (fVDR) of the VDR function can be tuned within the Nyquist band from 1/8 fS to 3/8 fS in 1/16 fS steps. In real mode, Tuning Word 2 (0x02) through Tuning Word 6 (0x06) are valid. Table 29 shows the relative frequency values, and Table 30 shows the absolute frequency values based on a sample rate of 491.52 MSPS. Center Frequency 1/8 fS 3/16 fS 1/4 fS 5/16 fS 3/8 fS Upper Band Edge 1/4 fS 5/16 fS 3/8 fS 7/16 fS 1/2 fS Table 30. VDR Tuning Words and Absolute Frequency Values, 25% BW, Real Mode with fS = 491.52 MSPS Tuning Word 2 (0x02) 3 (0x03) 4 (0x04) 5 (0x05) 6 (0x06) Lower Band Edge (MHz) 0 30.72 61.44 92.16 122.88 Center Frequency (MHz) 61.44 92.16 122.88 153.6 184.32 1/2 fS The center frequency (fVDR) of the VDR function can be tuned within the Nyquist band from 0 to 15/16fS in 1/16 fS steps. In complex mode, Tuning Word 0 (0x00) through Tuning Word 15 (0x0F) are valid. Table 31 and Table 32 show the tuning words and frequency values for the 25% complex mode. Table 31 shows the relative frequency values, and Table 32 shows the absolute frequency values based on a sample rate of 491.52 MSPS. Table 31. VDR Tuning Words and Relative Frequency Values, 25% BW, Complex Mode Table 29. VDR Tuning Words and Relative Frequency Values, 25% BW, Real Mode Lower Band Edge 0 1/16 fS 1/8 fS 3/16 fS 1/4 fS 3/8 fS Figure 82. 25% VDR Bandwidth, Complex Mode Figure 81. 25% VDR Bandwidth, Real Mode Tuning Word 2 (0x02) 3 (0x03) 4 (0x04) 5 (0x05) 6 (0x06) 1/8 fS 13059-080 –30 Upper Band Edge (MHz) 122.88 153.6 184.32 215.04 245.76 Tuning Word 0 (0x00) 1 (0x01) 2 (0x02) 3 (0x03) 4 (0x04) 5 (0x05) 6 (0x06) 7 (0x07) 8 (0x08) 9 (0x09) 10 (0x0A) 11 (0x0B) 12 (0x0C) 13 (0x0D) 14 (0x0E) 15 (0x0F) Rev. B | Page 60 of 81 Lower Band Edge −1/8 fS −1/16 fS 0 1/16 fS 1/8 fS 3/16 fS 1/4 fS 5/16 fS 3/8 fS 7/16 fS 1/2 fS 9/16 fS 5/8 fS 11/16 fS 3/4 fS 13/16 fS Center Frequency 0 1/16 fS 1/8 fS 3/16 fS 1/4 fS 5/16 fS 3/8 fS 7/16 fS 1/2 fS 9/16 fS 5/8 fS 11/16 fS 3/4 fS 13/16 fS 7/8 fS 15/16 fS Upper Band Edge 1/8 fS 3/16 fS 1/4 fS 5/16 fS 3/8 fS 7/16 fS 1/2 fS 9/16 fS 5/8 fS 11/16 fS 3/4 fS 13/16 fS 7/8 fS 15/16 fS fS 17/16 fS Data Sheet AD6679 Table 33. VDR Tuning Words and Relative Frequency Values, 43% BW, Complex Mode Table 32. VDR Tuning Words and Absolute Frequency Values, 25% BW, Complex Mode (fS = 491.52 MSPS) Lower Band Edge (MHz) −61.44 −30.72 0.00 30.72 61.44 92.16 122.88 153.6 184.32 215.04 245.76 276.48 307.2 337.92 368.64 399.36 Tuning Word 0 (0x00) 1 (0x01) 2 (0x02) 3 (0x03) 4 (0x04) 5 (0x05) 6 (0x06) 7 (0x07) 8 (0x08) 9 (0x09) 10 (0x0A) 11 (0x0B) 12 (0x0C) 13 (0x0D) 14 (0x0E) 15 (0x0F) Center Frequency (MHz) 0.00 30.72 61.44 92.16 122.88 153.6 184.32 215.04 245.76 276.48 307.2 337.92 368.64 399.36 430.08 460.8 Upper Band Edge (MHz) 61.44 92.16 122.88 153.6 184.32 215.04 245.76 276.48 307.2 337.92 368.64 399.36 430.08 460.8 491.52 522.24 Tuning Word 0 (0x00) 1 (0x01) 2 (0x02) 3 (0x03) 4 (0x04) 5 (0x05) 6 (0x06) 7 (0x07) 8 (0x08) 9 (0x09) 10 (0x0A) 11 (0x0B) 12 (0x0C) 13 (0x0D) 14 (0x0E) 15 (0x0F) Table 33 and Table 34 show the tuning words and frequency values for the 43% complex mode. Table 33 shows the relative frequency values, and Table 34 shows the absolute frequency values based on a sample rate of 491.52 MSPS. Figure 83 shows the frequency zones for the 43% BW VDR mode with a center frequency (fVDR) of fS/4 (tuning word = 0x04). The frequency zones where the amplitude may not exceed −30 dBFS are the upper and lower portions of the Nyquist band extending into the complex domain. dBFS –1/2 fS 0 1/29 fS 1/4 fS 1/2 fS 20/43 fS Figure 83. 43% VDR Bandwidth, Complex Mode 13059-081 –30 Lower Band Edge (MHz) −14/65 fS −11/72 fS −1/11 fS −1/36 fS 1/29 fS 7/72 fS 4/25 fS 2/9 fS 2/7 fS 25/72 fS 34/83 fS 17/36 fS 23/43 fS 43/72 fS 31/47 fS 13/18 fS Center Frequency (MHz) 0 1/16 fS 1/8 fS 3/16 fS 1/4 fS 5/16 fS 3/8 fS 7/16 fS 1/2 fS 9/16 fS 5/8 fS 11/16 fS 3/4 fS 13/16 fS 7/8 fS 15/16 fS Upper Band Edge (MHz) 14/65 fS 5/18 fS 16/47 fS 29/72 fS 20/43 fS 19/36 fS 49/83 fS 47/72 fS 5/7 fS 7/9 fS 21/25 fS 65/72 fS 28/29 fS 37/36 fS 12/11 fS 83/72 fS Table 34. VDR Tuning Words and Absolute Frequency Values, 43% BW, Complex Mode (fS = 491.52 MSPS) Tuning Word 0 (0x00) 1 (0x01) 2 (0x02) 3 (0x03) 4 (0x04) 5 (0x05) 6 (0x06) 7 (0x07) 8 (0x08) 9 (0x09) 10 (0x0A) 11 (0x0B) 12 (0x0C) 13 (0x0D) 14 (0x0E) 15 (0x0F) Rev. B | Page 61 of 81 Lower Band Edge (MHz) −105.37 −75.09 −44.68 −13.65 16.95 47.79 78.64 109.23 140.43 170.67 201.35 232.11 262.91 293.55 324.19 354.99 Center Frequency (MHz) 0.00 30.72 61.44 92.16 122.88 153.6 184.32 215.04 245.76 276.48 307.2 337.92 368.64 399.36 430.08 460.8 Upper Band Edge (MHz) 105.87 136.53 167.33 197.97 228.61 259.41 290.17 320.85 351.09 382.29 412.88 443.73 474.57 505.17 536.2 566.61 AD6679 Data Sheet DIGITAL OUTPUTS The minimum conversion rate of the AD6679 is 300 MSPS. At clock rates below 300 MSPS, dynamic performance may degrade. The AD6679 output drivers are for standard ANSI LVDS, but optionally the drive current can be reduced using Register 0x56A. The reduced drive current for the LVDS outputs potentially reduces the digitally induced noise. DATA CLOCK OUTPUT The AD6679 also provides a data clock output (DCO) intended for capturing the data in an external register. Figure 4 through Figure 11 show the timing diagrams of the AD6679 output modes. The DCO relative to the data output can be adjusted using Register 0x569. There are delay settings with approximately 90° per step ranging from 0° to 270°. Data is output in a DDR format and is aligned to the rising and falling edges of the clock derived from the DCO. As detailed in the AN-877 Application Note, Interfacing to High Speed ADCs via SPI, the data format can be selected for offset binary, twos complement, or gray code when using the SPI control. The AD6679 has a flexible three-state ability for the digital output pins. The three-state mode is enabled when the device is set for power-down mode. TIMING ADC OVERRANGE The AD6679 provides latched data with a pipeline delay of 33 input sample clock cycles. Data outputs are available one propagation delay (tPD) after the rising edge of the clock signal. The ADC overrange (OR) indicator is asserted when an overrange is detected on the input of the ADC. The overrange condition is determined at the output of the ADC pipeline and, therefore, is subject to a latency of 33 ADC clocks. An overrange at the input is indicated by the OR bit, 33 clock cycles after it occurs. Minimize the length of the output data lines and the corresponding loads to reduce transients within the AD6679. These transients can degrade converter dynamic performance. Table 35. LVDS Output Configurations 1 Parallel Output Mode Parallel Interleaved, One Virtual Converter (Register 0x568 = 0x0) Parallel Interleaved, Two Virtual Converters (Register 0x568 = 0x1) Channel Multiplexed, One Virtual Converter (Register 0x568 = 0x2) Channel Multiplexed, Two Virtual Converters (Register 0x568 = 0x3) Byte Mode, One Virtual Converter (Register 0x568 = 0x4) Byte Mode, Two Virtual Converters (Register 0x568 = 0x5) Byte Mode, Four Virtual Converters (Register 0x568 = 0x6) Byte Mode, Eight Virtual Converters (Register 0x568 = 0x7) No. of Virtual Converters Supported 1 Maximum Virtual Converter Resolution (Bits) 14 Output Line Rate 2, 3 1 × fOUT 2 14 1 DDC Decimation Rates Supported VDR Supported Yes NSR Decimation Rates Supported 1, 2 Real Output 1, 2, 4, 8 Complex Output N/A 2 × fOUT Yes 1, 2 1, 2, 4, 8 2, 4, 8, 16 DCO±, OVR±, and D0± to D13± 14 2 × fOUT Yes 1, 2 1, 2, 4, 8 N/A DCO±, OVR±, A Dx/Dy± 2 14 2 × fOUT Yes 1, 2 1, 2, 4, 8 2, 4, 8, 16 DCO±, OVR±, A Dx/ Dy±, and B Dx/Dy± 1 16 2 × fOUT No 1, 2 1, 2, 4, 8 N/A DCO±, STATUS±, and DATA0± to DATA7± 2 16 4 × fOUT No 2 2, 4, 8 2, 4, 8, 16 DCO±, STATUS±, and DATA0± to DATA7± 4 16 8 × fOUT No N/A 2 4, 4, 8 24, 4, 8, 16 DCO±, STATUS±, and DATA0± to DATA7± 8 16 16 × fOUT No N/A N/A 44, 8, 16 DCO±, STATUS±, and DATA0± to DATA7± N/A means not applicable. fOUT = ADC Sample Rate ÷ chip decimation ratio, where fOUT is the output sample rate. Maximum output line rate is 1000 Mbps. 4 fOUT ≤ 125 MSPS. 1 2 3 Rev. B | Page 62 of 81 Outputs Required DCO±, OVR±, and D0± to D13± Data Sheet AD6679 Table 36. Pin Mapping Comparison Between Parallel Interleaved, Channel Multiplexed, and Byte Modes Pin No. K13, K14 L13, L14 M13, M14 N14, P14 N13, P13 N12, P12 N11, P11 N10, P10 N9, P9 N5, P5 N4, P4 N3, P3 N2, P2 N1, P1 M2, M1 N6, P6 Parallel Interleaved Output DCO−, DCO+ OVR−, OVR+ D13−, D13+ D12−, D12+ D11−, D11+ D10−, D10+ D9−, D9+ D8−, D8+ D7−, D7+ D6−, D6+ D5−, D5+ D4−, D4+ D3−, D3+ D2−, D2+ D1−, D1+ D0−, D0+ Channel Multiplexed (Even/Odd) Output DCO−, DCO+ OVR−, OVR+ A D12/D13−, A D12/D13+ A D10/D11−, A D10/D11+ A D8/D9−, A D8/D9+ A D6/D7−, A D6/D7+ A D4/D5−, A D4/D5+ A D2/D3−, A D2/D3+ A D0/D1−, A D0/D1+ B D12/D13−, B D12/D13+ B D10/D11−, B D10/D11+ B D8/D9−, B D8/D9+ B D6/D7−, B D6/D7+ B D4/D5−, B D4/D5+ B D2/D3−, B D2/D3+ B D0/D1−, B D0/D1+ Rev. B | Page 63 of 81 Byte Output DCO−, DCO+ FCO−, FCO+ STATUS−, STATUS+ DATA7−, DATA7+ DATA6−, DATA6+ DATA5−, DATA5+ DATA4−, DATA4+ DATA3−, DATA3+ DATA2−, DATA2+ DATA1−, DATA1+ DATA0−, DATA0+ Not applicable Not applicable Not applicable Not applicable Not applicable AD6679 Data Sheet MULTICHIP SYNCHRONIZATION The AD6679 supports several features that aid users in meeting the requirements for capturing a SYNC± signal. The SYNC± sample event is defined as either a synchronous low to high transition or a synchronous high to low transition. Additionally, the AD6679 allows the SYNC± signal to be sampled using either the rising edge or falling edge of the CLK± input. The AD6679 also can ignore a programmable number (up to 16) of SYNC± events. The SYNC± control options can be selected using Register 0x120 and Register 0x121. The AD6679 has a SYNC± input that allows the user flexible options for synchronizing the internal blocks. The SYNC± input is a source synchronous system reference signal that enables multichip synchronization. The input clock divider, DDCs, and signal monitor block can be synchronized using the SYNC± input. For the highest level of timing accuracy, SYNC± must meet the setup and hold requirements relative to the CLK± input. The flowchart in Figure 84 shows the internal mechanism by which multichip synchronization can be achieved in the AD6679. START INCREMENT SYNC± IGNORE COUNTER NO NO RESET SYNC± IGNORE COUNTER NO SYNC± ENABLED? (REG 0x120) NO SYNC± ASSERTED? YES YES UPDATE SETUP/HOLD DETECTOR STATUS (REG 0x128) SYNC± IGNORE COUNTER EXPIRED? (REG 0x121) YES ALIGN CLOCK DIVIDER PHASE TO SYNC INPUT CLOCK DIVIDER ALIGNMENT REQUIRED? YES CLOCK DIVIDER AUTO ADJUST ENABLED? (REG 0x10D) YES NO CLOCK ALIGNMENT REQUIRED? YES NO YES ALIGN PHASE OF ALL INTERNAL CLOCKS TO SYNC± YES ALIGN SIGNAL MONITOR COUNTERS INCREMENT SYNC± COUNTER (REG 0x12A) CLOCK DIVIDER > 1? (REG 0x10B) NO NO NO DDC NCO ALIGNMENT ENABLED? (REG 0x300) YES NO Figure 84. Multichip Synchronization Rev. B | Page 64 of 81 ALIGN DDC NCO PHASE ACCUMULATOR BACK TO START 13059-082 SIGNAL MONITOR SYNC ENABLED? (REG 0x26F) Data Sheet AD6679 SYNC± SETUP AND HOLD WINDOW MONITOR To assist in ensuring a valid SYNC± capture, the AD6679 has a SYNC± setup and hold window monitor. This feature allows the system designer to determine the location of the SYNC± signals relative to the CLK± signals by reading back the amount of setup and hold margin on the interface through the memory map. Figure 85 and Figure 86 show both the setup and hold status values, respectively, for different phases of SYNC±. The setup detector returns the status of the SYNC± signal before the CLK± edge and the hold detector returns the status of the SYNC± signal after the CLK± edge. Register 0x128 stores the status of SYNC± and indicates whether the SYNC± signal was captured by the ADC. –1 –2 –3 –4 –5 –6 –7 REG 0x128[3:0] –8 7 6 5 4 3 2 1 0 CLK± INPUT VALID SYNC± INPUT FLIP FLOP HOLD (MIN) FLIP FLOP HOLD (MIN) Figure 85. SYNC ± Setup Detector Rev. B | Page 65 of 81 13059-083 FLIP FLOP SETUP (MIN) AD6679 Data Sheet REG 0x128[7:4] –1 –2 –3 –4 –5 –6 –7 –8 7 6 5 4 3 2 1 0 CLK± INPUT SYNC± INPUT FLIP FLOP SETUP (MIN) FLIP FLOP HOLD (MIN) FLIP FLOP HOLD (MIN) 13059-084 VALID Figure 86. SYNC± Hold Detector Table 37 shows the description of the contents of Register 0x128 and how to interpret them. Table 37. SYNC± Setup and Hold Monitor, Register 0x128 Register 0x128, Bits[7:4] Hold Status 0x0 Register 0x128, Bits[3:0] Setup Status 0x0 to 0x7 0x0 to 0x8 0x8 0x8 0x9 to 0xF 0x8 0x9 to 0xF 0x0 0x0 0x0 0x0 Description Possible setup error; the smaller this number, the smaller the setup margin No setup or hold error (best hold margin) No setup or hold error (best setup and hold margin) No setup or hold error (best setup margin) Possible hold error; the larger this number, the smaller the hold margin Possible setup or hold error Rev. B | Page 66 of 81 Data Sheet AD6679 TEST MODES ADC TEST MODES The AD6679 has various test options that aid in the system level implementation. The AD6679 has ADC test modes that are available in Register 0x550. These test modes are described in Table 38. When an output test mode is enabled, the analog section of the ADC is disconnected from the digital back-end blocks and the test pattern is run through the output formatting block. Some of the test patterns are subject to output formatting, and some are not. The PN generators from the PN sequence tests can be reset by setting Bit 4 or Bit 5 of Register 0x550. These tests can be performed with or without an analog signal (if present, the analog signal is ignored); however, they do require an encode clock. If the application mode has been set to select a DDC mode of operation, the test modes must be enabled for each DDC enabled. The test patterns can be enabled via Bit 2 and Bit 0 of Register 0x327, Register 0x347, Register 0x367, and Register 0x387, depending on which DDC(s) have been selected. The (I) output data uses the test patterns selected for Channel A and the (Q) output data uses the test patterns selected for Channel B. For more information, see the AN-877 Application Note, Interfacing to High Speed ADCs via SPI. Table 38. ADC Test Modes Output Test Mode Bit Sequence 0000 0001 0010 1000 Pattern Name Off (default) Midscale short Positive Full-scale short Negative Full-scale short Checkerboard PN sequence, long PN sequence, short One-/zero-word toggle User input 1111 Ramp output 0011 0100 0101 0110 0111 Expression Not applicable 00 0000 0000 0000 01 1111 1111 1111 Default/Seed Value Not applicable Not applicable Not applicable Sample (N, N + 1, N + 2, …) Not applicable Not applicable Not applicable 10 0000 0000 0000 Not applicable Not applicable 10 1010 1010 1010 x23 + x18 + 1 x9 + x5 + 1 11 1111 1111 1111 Not applicable 0x3AFF 0x0092 Not applicable 0x1555, 0x2AAA, 0x1555, 0x2AAA, 0x1555 0x3FD7, 0x0002, 0x26E0, 0x0A3D, 0x1CA6 0x125B, 0x3C9A, 0x2660, 0x0c65, 0x0697 0x0000, 0x3FFF, 0x0000, 0x3FFF, 0x0000 Register 0x551 to Register 0x558 Not applicable (x) % 214 Not applicable For repeat mode: User Pattern 1[15:2], User Pattern 2[15:2], User Pattern 3[15:2], User Pattern 4[15:2], User Pattern 1[15:2]… For single mode: User Pattern 1[15:2], User Pattern 2[15:2], User Pattern 3[15:2], User Pattern 4[15:2], 0x0000… (x) % 214, (x + 1) % 214, (x + 2) % 214, (x + 3) % 214 Rev. B | Page 67 of 81 AD6679 Data Sheet SERIAL PORT INTERFACE (SPI) The AD6679 SPI allows the user to configure the converter for specific functions or operations through a structured register space provided inside the ADC. The SPI gives the user added flexibility and customization, depending on the application. Addresses are accessed via the serial port and can be written to or read from via the serial port. Memory is organized into bytes that can be further divided into fields. These fields are documented in the Memory Map section. For detailed operational information, see the Serial Control Interface Standard. command is issued. This bit allows the SDIO pin to change direction from an input to an output. CONFIGURATION USING THE SPI Data can be sent in MSB first mode or in LSB first mode. MSB first is the default configuration on power-up and can be changed via the SPI port configuration register. For more information about this and other features, see the Serial Control Interface Standard. Three pins define the SPI of this ADC: the SCLK pin, the SDIO pin, and the CSB pin (see Table 39). The SCLK (serial clock) pin is used to synchronize the read and write data presented from/to the ADC. The SDIO (serial data input/output) pin is a dual-purpose pin that allows data to be sent to and read from the internal ADC memory map registers. The CSB (chip select bar) pin is an active low control that enables or disables the read and write cycles. Table 39. Serial Port Interface Pins Pin SCLK SDIO CSB Function Serial clock. The serial shift clock input, which synchronizes serial interface reads and writes. Serial data input/output. A dual-purpose pin that typically serves as an input or an output, depending on the instruction being sent and the relative position in the timing frame. Chip select bar. An active low control that gates the read and write cycles. The falling edge of CSB, in conjunction with the rising edge of SCLK, determines the start of the framing. See Figure 3 and Table 5 for an example of the serial timing and its definitions. Other modes involving the CSB pin are available. The CSB pin can be held low indefinitely, which permanently enables the device; this is called streaming. The CSB pin can stall high between bytes to allow additional external timing. When CSB is tied high, SPI functions are placed in a high impedance mode. This mode turns on any SPI pin secondary functions. All data is composed of 8-bit words. The first bit of each individual byte of serial data indicates whether a read or write In addition to word length, the instruction phase determines whether the serial frame is a read or write operation, allowing the serial port to be used both to program the chip and to read the contents of the on-chip memory. If the instruction is a readback operation, performing a readback causes the SDIO pin to change direction from an input to an output at the appropriate point in the serial frame. HARDWARE INTERFACE The pins described in Table 39 compose the physical interface between the user programming device and the serial port of the AD6679. The SCLK pin and the CSB pin function as inputs when using the SPI. The SDIO pin is bidirectional, functioning as an input during write phases and as an output during readback. The SPI is flexible enough to be controlled by either FPGAs or microcontrollers. One method for SPI configuration is described in detail in the AN-812 Application Note, MicrocontrollerBased Serial Port Interface (SPI) Boot Circuit. Do not activate the SPI port during periods when the full dynamic performance of the converter is required. Because the SCLK signal, the CSB signal, and the SDIO signal are typically asynchronous to the ADC clock, noise from these signals can degrade converter performance. If the on-board SPI bus is used for other devices, it may be necessary to provide buffers between this bus and the AD6679 to prevent these signals from transitioning at the converter inputs during critical sampling periods. SPI ACCESSIBLE FEATURES Table 40 provides a brief description of the general features that are accessible via the SPI. These features are described in detail in the Serial Control Interface Standard. The AD6679 device specific features are described in the Memory Map section. Table 40. Features Accessible Using the SPI Feature Name Mode Clock Test Input/Output Output Mode Serializer/Deserializer (SERDES) Output Setup Description Allows the user to set either power-down mode or standby mode Allows the user to access the clock divider via the SPI Allows the user to set test modes to have known data on output bits Allows the user to set up outputs Allows the user to vary SERDES settings, including swing and emphasis Rev. B | Page 68 of 81 Data Sheet AD6679 MEMORY MAP READING THE MEMORY MAP REGISTER TABLE Channel Specific Registers Each row in the memory map register table has eight bit locations. The memory map is roughly divided into seven sections: the Analog Devices, Inc., SPI registers, the analog input buffer control registers, ADC function registers, the DDC function registers, NSR decimate by 2 and noise shaping requantizer registers, variable dynamic range registers, and the digital outputs and test modes registers. Some channel setup functions such as analog input differential termination (Register 0x016) can be programmed to a different value for each channel. In these cases, channel address locations are internally duplicated for each channel. These registers and bits are designated in Table 41 as local. These local registers and bits can be accessed by setting the appropriate Channel A or Channel B bits in Register 0x008. If both bits are set, the subsequent write affects the registers of both channels. In a read cycle, set only Channel A or Channel B to read one of the two registers. If both bits are set during an SPI read cycle, the device returns the value for Channel A. Registers and bits designated as global in Table 41 affect the entire device and the channel features for which independent settings are not allowed between channels. The settings in Register 0x008 do not affect the global registers and bits. Table 41 (see the Memory Map Register Table section) documents the default hexadecimal value for each hexadecimal address shown. The column with the heading Bit 7 (MSB) is the start of the default hexadecimal value given. For example, Address 0x561, the output format register, has a hexadecimal default value of 0x01. This means that Bit 0 = 1, and the remaining bits are 0s. This setting is the default output format value, which is twos complement. For more information on this function and others, see Table 41. Open and Reserved Locations All address and bit locations that are not included in Table 41 are not currently supported for this device. Write unused bits of a valid address location with 0s unless the default value is set otherwise. Writing to these locations is required only when part of an address location is open (for example, Address 0x561). If the entire address location is open (for example, Address 0x013), do not write to this address location. Default Values After the AD6679 is reset, critical registers are loaded with default values. The default values for the registers are given in the memory map register table, Table 41. Logic Levels SPI Soft Reset After issuing a soft reset by programming 0x81 to Register 0x000, the AD6679 requires 5 ms to recover. Therefore, when programming the AD6679 for application setup, ensure that an adequate delay is programmed into the firmware after asserting the soft reset and before starting the device setup. Datapath Soft Reset After programming the desired clock divider settings, changing the input clock frequency, or glitching the input clock, a datapath soft reset is recommended by writing 0x02 to Register 0x001. This reset function restarts all the datapath and clock generation circuitry in the device. The reset occurs on the first clock cycle after the register is programmed and the device requires 5 ms to recover. This reset does not affect the contents of the memory map registers. An explanation of logic level terminology follows: • • • “Bit is set” is synonymous with “bit is set to Logic 1” or “writing Logic 1 for the bit.” “Clear a bit” is synonymous with “bit is set to Logic 0” or “writing Logic 0 for the bit.” “X” denotes “don’t care”. Rev. B | Page 69 of 81 AD6679 Data Sheet MEMORY MAP REGISTER TABLE All address and bit locations that are not included in Table 41 are not currently supported for this device. Table 41. Memory Map Registers Reg. Addr. (Hex) Register Name Analog Devices SPI Registers 0x000 INTERFACE_CONFIG_ A Bit 7 (MSB) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Soft reset (self clearing): clears memory map registers Single instruction LSB first 0 = MSB 1 = LSB Address ascension 0 0 Address ascension LSB first 0 = MSB 1 = LSB 0 0 0 0 0 0 0 0 0 0 0x001 INTERFACE_CONFIG_B 0x002 DEVICE_CONFIG (local) 0x003 CHIP_TYPE 0x004 CHIP_ID (low byte) 0x005 CHIP_ID (high byte) 0x006 CHIP_GRADE 0x008 Device index 0 0 0x00A 0x00B 0x00C Scratch pad SPI revision Vendor ID (low byte) 0 0 0 0 0 1 0x00D Vendor ID (high byte) 0 Input termination (local) 0x934 Input capacitance Soft reset (self clearing): clears memory map registers Datapath 0 soft reset (self clearing): does not clear memory map registers 00 = normal 0 operation 10 = standby 11 = power-down 011 = high speed ADC Default 0 0 0 0 0x00 0x00 0x03 0 0 0 0 0x00 0 1 0 X X 0 0 0 0 0 1 0 0 0 0 0 1 Channel A 0 1 0 0x03 0 0 0 Channel B 0 0 1 0x00 0x01 0x56 0 0 0 0 1 0 0 0x04 0 0 0 0 0 0 0x00 1 1 0 Input disable 0= normal operation 1 = input disabled 0 Chip speed grade 0101 = 500 MSPS 0 0 Analog input differential termination 0000 = 400 Ω (default) 0001 = 200 Ω 0010 = 100 Ω 0110 = 50 Ω 0 0 Rev. B | Page 70 of 81 0x1F = 3 pF to GND (default) 0x00 = 1.5 pF to GND Notes 0x00 0xD3 Analog Input Buffer Control Registers 0x015 Analog Input (local) 0 0x016 Bit 0 (LSB) 0x0C 0x1F Read only Read only Read only Read only Read only Read only Data Sheet Reg. Addr. (Hex) 0x018 Register Name Buffer Control 1 (local) AD6679 Bit 7 (MSB) 0x019 Buffer Control 2 (local) 0x01A Buffer Control 3 (local) Bit 6 Bit 5 Bit 4 0000 = 1.0× buffer current 0001 = 1.5× buffer current 0010 = 2.0× buffer current (default) 0011 = 2.5× buffer current 0100 = 3.0× buffer current 0101 = 3.5× buffer current … 1111 = 8.5× buffer current 0100 = Setting 1 0101 = Setting 2 0110 = Setting 3 (default) 0111 = Setting 4 (see Table 11 for setting per frequency range) 0 0 0 0 0x11A Buffer Control 4 (local) 0 0 0x935 Buffer Control 5 (local) 0 0x025 Input full-scale range (local) 0x030 Input full-scale control (local) ADC Function Registers 0x024 V_1P0 control Bit 3 0 Bit 2 0 Bit 1 0 Bit 0 (LSB) 0 Default 0x20 0 0 0 0 0x60 0 0 High frequency setting 0 = off (default) 1 = on 0 1000 = Setting 1 1001 = Setting 2 1010 = Setting 3 (default) (see Table 11 for setting per frequency range) 0 0 0 0 0 0 0 0 0 0 0 0 0 Full-scale control See Table 11 for recommended settings for different frequency bands; default values: Full scale range ≥ 1.82 V = 001 Full scale range < 1.82 V = 110 0 0 0x04 0 0 0 0 0 0 0 1.0 V reference select 0= internal 1= external Diode selection 0 = no diode selected 1= temperature diode selected 0 0x00 Low 0 0 frequency operation 0 = off 1 = on (default) Full-scale adjust 0000 = 1.94 V p-p 1000 = 1.46 V p-p 1001 = 1.58 V p-p 1010 = 1.70 V p-p 1011 = 1.82 V p-p 1100 = 2.06 V p-p (default) 0x028 Temperature diode (local) 0 0 0 0 0 0 0 0x03F PDWN/STBY pin control (local) 0= PDWN/ STBY enabled 1= disabled 0 0 0 0 0 0 Rev. B | Page 71 of 81 Notes 0x0A 0x00 0x04 0x0C Differential; use in conjunction with Reg. 0x030 Used in conjunction with Reg. 0x025 0x00 0x00 Used in conjunction with Reg. 0x040 AD6679 Reg. Addr. (Hex) 0x040 Register Name Chip pin control 0x10B Clock divider 0x10C Data Sheet Bit 7 (MSB) Bit 6 PDWN/STBY function 00 = power down 01 = standby 10 = disabled 0 0 0 0 Clock divider phase (local) 0 0 0 0 0x10D Clock divider and SYNC± control Clock divider autophase adjust 0= disabled 1= enabled 0 0 0 0x117 Clock delay control 0 0 0 0 0x118 Clock fine delay 0x11C Clock status 0 0x120 SYNC± Control 1 0 0x121 SYNC± Control 2 0 Bit 5 Bit 0 (LSB) Bit 1 Fast Detect A (FD_A) 000 = Fast Detect A output 011 = temperature diode 111 = disabled 000 = divide by 1 0 001 = divide by 2 011 = divide by 4 111 = divide by 8 Independently controls Channel A and Channel B clock divider phase offset 0000 = 0 input clock cycles delayed 0001 = ½ input clock cycles delayed 0010 = 1 input clock cycles delayed 0011 = 1½ input clock cycles delayed 0100 = 2 input clock cycles delayed 0101 = 2½ input clock cycles delayed … 1111 = 7½ input clock cycles delayed Clock divider positive Clock divider skew window negative skew 00 = no positive skew window 01 = 1 device clock of 00 = no negative positive skew skew 10 = 2 device clocks 01 = 1 device clock of of positive skew negative skew 11 = 3 device clocks 10 = 2 device clocks of positive skew of negative skew 11 = 3 device clocks of negative skew Clock fine 0 0 0 delay adjust enable 0= disabled 1= enabled Bit 4 Bit 3 Fast Detect B (FD_B) 000 = Fast Detect B output 111 = disabled Bit 2 Clock Fine Delay Adjust[7:0] Twos complement coded control to adjust the fine sample clock skew in ~1.7 ps steps ≤−88 = −151.7 ps skew −87 = −150.0 ps skew … 0 = 0 ps skew … ≥ +87 = +150 ps skew 0 = no 0 0 0 0 0 0 input clock detected 1 = input clock detected SYNC± mode select CLK± SYNC± 0 0 0 00 = disabled edge transition 01 = continuous select select 10 = N shot 0= 0 = low to rising high 1= 1 = high to falling low SYNC± N-shot ignore counter select 0 0 0 0000 = next SYNC± only 0001 = ignore the first SYNC± transitions 0010 = ignore the first two SYNC± transitions … 1111 = ignore the first 16 SYNC± transitions Rev. B | Page 72 of 81 Default 0x3F Notes 0x00 0x00 0x00 Clock divider must be >1 0x00 Enabling the clock fine delay adjust causes a datapath soft reset Used in conjunction with Reg. 0x117 0x00 0x00 Read only 0x00 0x00 Mode select (Reg. 0x120, Bits[2:1]) must be N-shot Data Sheet Reg. Addr. (Hex) 0x128 Register Name SYNC± Status 1 AD6679 Bit 7 (MSB) Bit 0 (LSB) Bit 2 Bit 1 SYNC± setup status See Table 37 Clock divider phase when SYNC± is captured 0 0000 = in phase 0001 = SYNC ± is ½ cycle delayed from clock 0010 = SYNC ± is 1 cycle delayed from clock 0011 = 1½ input clock cycles delayed 0100 = 2 input clock cycles delayed 0101 = 2½ input clock cycles delayed … 1111 = 7½ input clock cycles delayed SYNC± counter, Bits[7:0] increment when a SYNC± signal is captured Bit 6 Bit 5 SYNC± hold status See Table 37 0 0 0x129 SYNC± and clock divider status 0x12A SYNC± counter 0x200 Chip application mode 0 0 0x201 Chip decimation ratio 0 0 0x228 0x245 Customer offset Fast detect (FD) control (local) 0 0 0x247 FD upper threshold LSB (local) FD upper threshold MSB (local) FD lower threshold LSB (local) FD lower threshold MSB (local) FD dwell time LSB (local) FD dwell time MSB (local) Signal monitor synchronization control 0x248 0x249 0x24A 0x24B 0x24C 0x26F 0x270 Signal monitor control (local) 0 0 Chip Q ignore 0= normal (I/Q) 1= ignore (I only) 0 Bit 4 Bit 3 Chip operating mode 0001 = DDC 0 on 0010 = DDC 0 and DDC 1 on 0011 = DDC 0, DDC 1, DDC 2, and DDC 3 on 0111 = NSR enabled (default) 1000 = VDR enabled 0 Chip decimation ratio select 000 = decimate by 1 001 = decimate by 2 010 = decimate by 4 011 = decimate by 8 100 = decimate by 16 Offset adjust in LSBs from +127 to −128 (twos complement format) Enable Force Force 0 0 0 fast value of FD_A/ detect FD_A/ FD_B output FD_B pins pins; if 0= force pins normal is true, functhis value tion is output 1= on FD_x force to pins value Fast Detect Upper Threshold[7:0] 0 0 0 0 Fast Detect Upper Threshold[12:8] Fast Detect Lower Threshold[7:0] 0 0 0 Default Read only 0x07 0x00 0x00 0x00 0x00 0x00 0x00 Fast Detect Lower Threshold[12:8] 0x00 Fast Detect Dwell Time[7:0] 0x00 Fast Detect Dwell Time[15:8] 0x00 0 0 0 0 0 0 0 0 0 0 0 0 Rev. B | Page 73 of 81 Notes Read only Read only Synchronization mode 00 = disabled 01 = continuous 11 = one-shot Peak 0 detector 0= disabled 1= enabled 0x00 0x00 See the Signal Monitor section AD6679 Reg. Addr. (Hex) 0x271 Register Name Signal Monitor Period Register 0 (local) Data Sheet Bit 7 (MSB) Bit 6 Bit 5 Bit 4 Bit 3 Signal Monitor Period[7:1] Bit 2 Bit 1 Bit 0 (LSB) 0 Default 0x80 0x272 Signal Monitor Period Register 1 (local) Signal Monitor Period[15:8] 0x00 0x273 Signal Monitor Period Register 2 (local) Signal Monitor Period[23:16] 0x00 0x274 Signal monitor result control (local) 0x275 Signal Monitor Result Register 0 (local) Signal Monitor Result[7:0] When Register 0x0274, Bit 0 = 1, Result Bits[19:7] = Peak Detector Absolute Value[12:0]; Result Bits[6:0] = 0 0x276 Signal Monitor Result Register 1 (local) Signal Monitor Result[15:8] 0x277 Signal Monitor Result Register 1 (local) 0x278 Signal monitor period counter result (local) 0 0 0 0 0 0 Result update 1 = update results (self clear) 0 0 0 0 Result selection 0= Reserved 1 = peak detector 0x01 Read only, updated based on Reg. 0x274, Bit 4 Read only, updated based on Reg. 0x274, Bit 4 Read only, updated based on Reg. 0x274, Bit 4 Read only, updated based on Reg 0x274, Bit 4 Signal Monitor Result[19:16] Period Count Result[7:0] Digital Downconverter (DDC) Function Registers—See the Digital Downconverter (DDC) Section DDC NCO 0 0 0x300 DDC synchronization 0 0 0 control soft reset 0 = normal operation 1 = reset Rev. B | Page 74 of 81 Synchronization mode 00 = disabled 01 = continuous 11 = one shot Notes In decimated output clock cycles In decimated output clock cycles In decimated output clock cycles 0x00 Data Sheet Reg. Addr. (Hex) 0x310 Register Name DDC 0 control 0x311 DDC 0 input selection 0x314 0x315 0x320 0x321 0x327 DDC 0 frequency LSB DDC 0 frequency MSB DDC 0 phase LSB DDC 0 phase MSB DDC 0 output test mode selection 0x330 AD6679 Bit 7 (MSB) Mixer select 0 = real mixer 1= complex mixer Bit 6 Gain select 0 = 0 dB gain 1 = 6 dB gain Bit 5 0 0 0 X X X 0 X 0 DDC 1 control Mixer select 0 = real mixer 1= complex mixer Gain select 0 = 0 dB gain 1 = 6 dB gain 0x331 DDC 1 input selection 0 0 0x334 0x335 0x340 0x341 0x347 DDC 1 frequency LSB DDC 1 frequency MSB DDC 1 phase LSB DDC 1 phase MSB DDC 1 output test mode selection X X X 0 X 0 Bit 4 IF mode 00 = variable IF mode (mixers and NCO enabled) 01 = 0 Hz IF mode (mixer bypassed, NCO disabled) 10 = fADC/4 Hz IF mode (fADC/4 downmixing mode) 11 = test mode (mixer inputs forced to +FS, NCO enabled) Bit 3 Complex to real enable 0= disabled 1= enabled Bit 2 0 Bit 0 (LSB) Bit 1 Decimation rate select (complex to real disabled) 11 = decimate by 2 00 = decimate by 4 01 = decimate by 8 10 = decimate by 16 (complex to real enabled) 11 = decimate by 1 00 = decimate by 2 01 = decimate by 4 10 = decimate by 8 I input 0 select 0 = Ch. A 1 = Ch. B Q input select 0 = Ch. A 1 = Ch. B DDC 0 NCO FTW[7:0], twos complement X X DDC 0 NCO FTW[11:8], twos complement DDC 0 NCO POW[7:0], twos complement X X DDC 0 NCO POW[11:8], twos complement I output Q output 0 0 0 0 test test mode mode enable enable 0= 0= disabled disabled 1= 1= enabled enabled from from Ch. A Ch. B IF mode Decimation rate Complex 0 00 = variable IF mode select to real (mixers and NCO (complex to real enable enabled) disabled) 0= 01 = 0 Hz IF mode 11 = decimate by 2 disabled (mixer bypassed, NCO 00 = decimate by 4 1= disabled) 01 = decimate by 8 enabled 10 = fADC/4 Hz IF mode 10 = decimate by 16 (complex to real (fADC/4 downmixing enabled) mode) 11 = decimate by 1 11 = test mode (mixer 00 = decimate by 2 inputs forced to +FS, 01 = decimate by 4 NCO enabled) 10 = decimate by 8 I input Q input 0 0 0 0 select select 0 = Ch. A 0 = Ch. A 1 = Ch. B 1 = Ch. B DDC 1 NCO FTW[7:0], twos complement X X DDC1 NCO FTW[11:8], twos complement DDC 1 NCO POW[7:0], twos complement X X DDC1 NCO POW[11:8], twos complement Q output I output 0 0 0 0 test test mode mode enable enable 0= 0= disabled disabled 1= 1= enabled enabled from from Ch. B Ch. A 0 0 Rev. B | Page 75 of 81 Default 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x05 0x00 0x00 0x00 0x00 0x00 Notes AD6679 Reg. Addr. (Hex) 0x350 Register Name DDC 2 control 0x351 DDC 2 input selection 0x354 0x355 0x360 0x361 0x367 DDC 2 frequency LSB DDC 2 frequency MSB DDC 2 phase LSB DDC 2 phase MSB DDC 2 output test mode selection 0x370 Data Sheet Bit 7 (MSB) Mixer select 0 = real mixer 1= complex mixer Bit 6 Gain select 0 = 0 dB gain 1 = 6 dB gain Bit 5 0 0 0 X X X 0 X 0 DDC 3 control Mixer select 0 = real mixer 1= complex mixer Gain select 0 = 0 dB gain 1 = 6 dB gain 0x371 DDC 3 input selection 0 0 0x374 0x375 0x380 0x381 0x387 DDC 3 frequency LSB DDC 3 frequency MSB DDC 3 phase LSB DDC 3 phase MSB DDC 3 output test mode selection X X X 0 X 0 Bit 4 IF mode 00 = variable IF mode (mixers and NCO enabled) 01 = 0 Hz IF mode (mixer bypassed, NCO disabled) 10 = fADC/4 Hz IF mode (fADC/4 downmixing mode) 11 = test mode (mixer inputs forced to +FS, NCO enabled) Bit 3 Complex to real enable 0= disabled 1= enabled Bit 2 0 Bit 0 (LSB) Bit 1 Decimation rate select (complex to real disabled) 11 = decimate by 2 00 = decimate by 4 01 = decimate by 8 10 = decimate by 16 (complex to real enabled) 11 = decimate by 1 00 = decimate by 2 01 = decimate by 4 10 = decimate by 8 I input 0 select 0 = Ch. A 1 = Ch. B Q input select 0 = Ch. A 1 = Ch. B DDC 2 NCO FTW[7:0], twos complement X X DDC 2 NCO FTW[11:8], twos complement DDC 2 NCO POW[7:0], twos complement X X DDC 2 NCO POW[11:8], twos complement I output Q output 0 0 0 0 test test mode mode enable enable 0= 0= disabled disabled 1= 1= enabled enabled from from Ch. A Ch. B IF mode Decimation rate Complex 0 00 = variable IF mode select to real (mixers and NCO (complex to real enable enabled) disabled) 0= 01 = 0 Hz IF mode 11 = decimate by 2 disabled (mixer bypassed, NCO 00 = decimate by 4 1= disabled) 01 = decimate by 8 enabled 10 = fADC/4 Hz IF mode 10 = decimate by 16 (complex to real (fADC/4 downmixing enabled) mode) 11 = decimate by 1 11 = test mode (mixer 00 = decimate by 2 inputs forced to +FS, 01 = decimate by 4 NCO enabled) 10 = decimate by 8 I input Q input 0 0 0 0 select select 0 = Ch. A 0 = Ch. A 1 = Ch. B 1 = Ch. B DDC 3 NCO FTW[7:0], twos complement X X DDC 3 NCO FTW[11:8], twos complement DDC 3 NCO POW[7:0], twos complement X X DDC 3 NCO POW[11:8], twos complement Q output I output 0 0 0 0 test test mode mode enable enable 0= 0= disabled disabled 1= 1= enabled enabled from from Ch. B Ch. A 0 0 NSR Decimate by 2 and Noise Shaping Requantizer (NSR) Rev. B | Page 76 of 81 Default 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x05 0x00 0x00 0x00 0x00 0x00 Notes Data Sheet Reg. Addr. (Hex) 0x41E Register Name NSR decimate by 2 0x420 0x422 AD6679 Bit 6 X Bit 5 0 NSR mode Bit 7 (MSB) Highpass filter (HPF)/ low-pass filter mode 0= enable LPF 1= enable HPF X X X NSR tuning X X Variable Dynamic Range (VDR) 0x430 VDR control X X X 0 0x434 X X X X User pattern selection 0= continuous repeat 1= single pattern 0 Reset PN long gen 0 = long PN enable 1 = long PN reset Reset PN short gen 0 = short PN enable 1 = short PN reset VDR tuning Digital Outputs and Test Modes 0x550 ADC test modes (local) Bit 4 0 Bit 3 X Bit 2 X Bit 1 X Bit 0 (LSB) NSR decimate by 2 enable 0= disabled 1= enabled NSR mode X 000 = 21% BW mode 001 = 28% BW mode NSR tuning word; see the Noise Shaping Requantizer (NSR) section; equations for the tuning word are dependent on the NSR mode X Default 0x00 0x00 0x00 0 = dual VDR BW real mode mode 0 = 25% 1 = dual BW complex mode mode 1 = 43% (Channel BW A = I, mode Channel (only B = Q) available for dual complex mode) VDR center frequency; see the Variable Dynamic Range (VDR) section for more details on the center frequency, which is dependent on the VDR mode 0x01 0x00 0x00 X X 0x00 0x551 User Pattern 1 LSB 0 0 0 0 Test mode selection 0000 = off (normal operation) 0001 = midscale short 0010 = positive full scale 0011 = negative full scale 0100 = alternating checkerboard 0101 = PN sequence, long 0110 = PN sequence, short 0111 = 1/0 word toggle 1000 = user pattern test mode (used with Register 0x550, Bit 7, and User Pattern 1 to User Pattern 4 registers) 1111 = ramp output 0 0 0 0 0x552 User Pattern 1 MSB 0 0 0 0 0 0 0 0 0x00 0x553 User Pattern 2 LSB 0 0 0 0 0 0 0 0 0x00 0x554 User Pattern 2 MSB 0 0 0 0 0 0 0 0 0x00 Rev. B | Page 77 of 81 Notes Used with Reg. 0x550 Used with Reg. 0x550 Used with Reg. 0x550 Used with Reg. 0x550 AD6679 Data Sheet Reg. Addr. (Hex) 0x555 Register Name User Pattern 3 LSB Bit 7 (MSB) 0 Bit 6 0 Bit 5 0 Bit 4 0 Bit 3 0 Bit 2 0 Bit 1 0 Bit 0 (LSB) 0 Default 0x00 0x556 User Pattern 3 MSB 0 0 0 0 0 0 0 0 0x00 0x557 User Pattern 4 LSB 0 0 0 0 0 0 0 0 0x00 0x558 User Pattern 4 MSB 0 0 0 0 0 0 0 0 0x00 0x559 Output Mode Control 1 0 0 0 0 0 0x561 Output format 0 0 0 0 0 0x562 Output overrange (OR) clear Output overrange status 0x564 Output channel select Virtual Converter 6 OR 0 = OR bit enabled 1 = OR bit cleared Virtual Converter 6 OR 0 = no OR 1 = OR occurred 0 Virtual Converter 5 OR 0 = OR bit enabled 1 = OR bit cleared Virtual Converter 5 OR 0 = no OR 1 = OR occurred 0 Virtual Converter 4 OR 0 = OR bit enabled 1 = OR bit cleared 0x563 Virtual Converter 7 OR 0 = OR bit enabled 1 = OR bit cleared Virtual Converter 7 OR 0 = no OR 1 = OR occurred 0 Virtual Converter 3 OR 0 = OR bit enabled 1 = OR bit cleared Virtual Converter 3 OR 0 = no OR 1 = OR occurred 0 Status bit selection 000 = tie low (1’b0) 001 = overrange bit 010 = signal monitor bit 011 = fast detect (FD) bit or VDR punish bit 100 = VDR high/low resolution bit 101 = system reference Sample Data format select invert 00 = offset binary 0= 01 = twos normal complement (default) 1= sample invert Virtual Virtual Virtual ConConConverter 2 verter 1 verter 0 OR OR OR 0 = OR bit 0 = OR 0 = OR bit enabled bit enabled 1 = OR bit enabled 1 = OR bit cleared 1 = OR cleared bit cleared Virtual Virtual Virtual ConConConverter 0 verter 1 verter 2 OR OR OR 0 = no OR 0 = no OR 0 = no 1 = OR OR 1 = OR occurred 1 = OR occurred occurred Converter 0 0 channel swap 0= normal channel ordering 1= channel swap enabled Virtual Converter 4 OR 0 = no OR 1 = OR occurred 0 Rev. B | Page 78 of 81 Notes Used with Reg. 0x550 Used with Reg. 0x550 Used with Reg. 0x550 Used with Reg. 0x550 0x00 0x01 0x00 0x00 0x00 Read only Data Sheet AD6679 Reg. Addr. (Hex) 0x568 Register Name Output mode Bit 7 (MSB) 0 Bit 6 0 Bit 5 Bit 4 Frame clock mode (only used when in output data mode is in byte mode) 00 = frame clock always off 01 = frame clock always on 10 = reserved 11 = frame clock conditionally on based on PN23 sequence 0x569 DCO output delay 0 0 0 0 0x56A Output adjust 0 1 0 0 0x56B Output slew rate adjust 0 0 0 0 Bit 0 (LSB) Bit 1 Output data mode 000 = parallel interleaved mode (one virtual converter) 001 = parallel interleaved mode (two virtual converters) 010 = channel multiplexed (even/odd) mode (one virtual converter) 011 = channel multiplexed (even/odd) mode (two virtual converters) 100 = byte mode (one virtual converter) 101 = byte mode (two virtual converters) 110 = byte mode (four virtual converters) 111 = byte mode (eight virtual converters) DCO clock delay 0 0 00 = 0° 01 = 90° (available when DCO rate is less than sample clock rate) 10 = 180° 11 = 270° (available when DCO rate is less than sample clock rate) LVDS output drive current adjust 0 000 = 2 mA 001 = 2.25 mA 010 = 2.5 mA 011 = 2.75 mA 100 = 3.0 mA 101 = 3.25 mA 110 = 3.5 mA (default) 111 = 3.75 mA Output slew rate 0 0 control 00 = 80 ps 01 = 150 ps 10 = 200 ps 11 = 250 ps Bit 3 0 Rev. B | Page 79 of 81 Bit 2 Default 0x01 0x4C 0x00 Notes AD6679 Data Sheet APPLICATIONS INFORMATION POWER SUPPLY RECOMMENDATIONS 1.8V AVDD1 1.25V ADP1741 DVDD 1.25V DRVDD 1.25V SPIVDD (1.8V OR 3.3V) 3.6V ADP125 AVDD3 3.3V 3.3V ADM7172 OR ADP1741 AVDD2 2.5V 13059-085 The AD6679 must be powered by the following six supplies: AVDD1 = 1.25 V, AVDD2 = 2.5 V, AVDD3 = 3.3 V, DVDD = 1.25 V, DRVDD = 1.25 V, SPIVDD = 1.8 V. For applications requiring an optimal high power efficiency and low noise performance, it is recommended that the ADP2164 and ADP2370 switching regulators be used to convert the 3.3 V, 5.0 V, or 12 V input rails to an intermediate rail (1.8 V and 3.8 V). These intermediate rails are then postregulated by very low noise, low dropout (LDO) regulators (ADP1741, ADM7172, and ADP125). Figure 87 shows the recommended method. For more detailed information on the recommended power solution, see the AD6679 evaluation board wiki, Evaluating the AD6679 IF Diversity Receiver. ADP1741 Figure 87. High Efficiency, Low Noise Power Solution for the AD6679 It is not necessary to split all of these power domains in all cases. The recommended solution shown in Figure 87 provides the lowest noise, highest efficiency power delivery system for the AD6679. If only one 1.25 V supply is available, it must be routed to AVDD1 first and then tapped off and isolated with a ferrite bead or a filter choke preceded by decoupling capacitors for SPIVDD, DVDD, and DRVDD, in that order. The user can use several different decoupling capacitors to cover both high and low frequencies. These capacitors must be located close to the point of entry at the PCB level and close to the devices, with minimal trace lengths. Rev. B | Page 80 of 81 Data Sheet AD6679 OUTLINE DIMENSIONS A1 BALL PAD CORNER 14 13 12 11 10 9 8 7 6 5 4 3 2 1 8.20 SQ 11.20 SQ TOP VIEW 1.49 1.38 1.27 A B C D E F G H J K L M N P 10.40 REF SQ 0.80 BOTTOM VIEW 0.80 REF DETAIL A 0.75 REF DETAIL A 1.15 1.05 0.95 0.38 0.33 0.28 0.30 REF PKG-004472 SEATING PLANE 0.50 0.45 0.40 BALL DIAMETER COPLANARITY 0.12 COMPLIANT TO JEDEC STANDARDS MO-275-GGAB-1. 04-24-2015-A A1 BALL PAD CORNER 12.10 12.00 SQ 11.90 Figure 88. 196-Ball Ball Grid Array, Thermally Enhanced [BGA_ED] (BP-196-3) Dimensions shown in millimeters ORDERING GUIDE Model1 AD6679BBPZ-500 AD6679BBPZRL7-500 AD6679-500EBZ 1 Temperature Range −40°C to +85°C −40°C to +85°C Package Description 196-Ball Ball Grid Array, Thermally Enhanced [BGA_ED] 196-Ball Ball Grid Array, Thermally Enhanced [BGA_ED] Evaluation Board for AD6679-500 Z = RoHS Compliant Part. ©2015–2016 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D13059-0-4/16(B) Rev. B | Page 81 of 81 Package Option BP-196-3 BP-196-3