Quad IF Receiver AD6657A Data Sheet FEATURES FUNCTIONAL BLOCK DIAGRAM AVDD AGND DRVDD DRGND AD6657A VIN+A PIPELINE ADC VIN–A 14 NOISE SHAPING REQUANTIZER DO±AB VCMA VIN+B PIPELINE ADC VIN–B 14 NOISE SHAPING REQUANTIZER 11 VCMB VIN+C PIPELINE ADC VIN–C 14 NOISE SHAPING REQUANTIZER DCO±AB 11 11 DATA MULTIPLEXER AND LVDS DRIVERS PORT A D10±AB DCO±CD DO±CD PORT B VCMC VIN+D PIPELINE ADC VIN–D 14 NOISE SHAPING REQUANTIZER 11 D10±CD VCMD MODE REFERENCE CLOCK DIVIDER PDWN SERIAL PORT SCLK SDIO SYNC CSB CLK+ CLK– 09684-001 11-bit, 200 MSPS output data rate per channel Integrated noise shaping requantizer Performance with NSR enabled SNR: 76.0 dBFS in 40 MHz band to 70 MHz at 185 MSPS SNR: 73.6 dBFS in 60 MHz band to 70 MHz at 185 MSPS SNR: 72.8 dBFS in 65 MHz band to 70 MHz at 185 MSPS Performance with NSR disabled SNR: 66.5 dBFS to 70 MHz at 185 MSPS SFDR: 88 dBc to 70 MHz at 185 MSPS Low power: 1.2 W at 185 MSPS 1.8 V analog supply operation 1.8 V LVDS (ANSI-644 levels) output 1-to-8 integer clock divider Internal ADC voltage reference 1.75 V p-p analog input range (programmable to 2.0 V p-p) Differential analog inputs with 800 MHz bandwidth 95 dB channel isolation/crosstalk Serial port control User-configurable built-in self test (BIST) capability Energy saving power-down modes Figure 1. APPLICATIONS Communications Diversity radio and smart antenna (MIMO) systems Multimode digital receivers (3G) WCDMA, LTE, CDMA2000 WiMAX, TD-SCDMA I/Q demodulation systems General-purpose software radios GENERAL DESCRIPTION The AD6657A is an 11-bit, 200 MSPS, quad channel intermediate frequency (IF) receiver specifically designed to support multiple antenna systems in telecommunication applications where high dynamic range performance, low power, and small size are desired. The device consists of four high performance ADCs and NSR digital blocks. Each ADC consists of a multistage, differential pipelined architecture with integrated output error correction logic. The ADC features a wide bandwidth switched capacitor sampling network within the first stage of the differential pipeline. An integrated voltage reference eases design considerations. A duty cycle stabilizer (DCS) compensates for variations in the ADC clock duty cycle, allowing the converters to maintain excellent performance. Each ADC output is connected internally to an NSR block. The integrated NSR circuitry allows for improved SNR performance in a smaller frequency band within the Nyquist bandwidth. The device supports two different output modes selectable via the external MODE pin or the serial port interface (SPI). With the NSR feature enabled, the outputs of the ADCs are processed such that the AD6657A supports enhanced SNR performance within a limited portion of the Nyquist bandwidth while maintaining an 11-bit output resolution. The NSR block can be programmed to provide a bandwidth of either 22%, 33%, or 36% of the sample clock. For example, with a sample clock rate of 185 MSPS, the AD6657A can achieve up to 76.0 dBFS SNR for a 40 MHz bandwidth in the 22% mode, up to 73.6 dBFS SNR for a 60 MHz bandwidth in the 33% mode, or up to 72.8 dBFS SNR for a 65 MHz bandwidth in the 36% mode. (General Description continued on Page 3) Rev. 0 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. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 ©2011 Analog Devices, Inc. All rights reserved. AD6657A Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Channel/Chip Synchronization ................................................ 23 Applications ....................................................................................... 1 Digital Outputs ........................................................................... 24 Functional Block Diagram .............................................................. 1 Timing ......................................................................................... 24 General Description ......................................................................... 1 Noise Shaping Requantizer ........................................................... 25 Revision History ............................................................................... 2 22% BW Mode (>40 MHz at 184.32 MSPS) ........................... 25 Product Highlights ........................................................................... 3 33% BW Mode (>60 MHz at 184.32 MSPS) ........................... 26 Specifications..................................................................................... 4 36% BW Mode (>65 MHz at 184.32 MSPS) ........................... 27 DC Specifications ......................................................................... 4 MODE Pin ................................................................................... 27 AC Specifications.......................................................................... 5 Built-In Self Test (BIST) and Output Test ................................... 28 Digital Specifications ................................................................... 7 BIST .............................................................................................. 28 Switching Specifications .............................................................. 9 Output Test Modes ..................................................................... 28 Timing Specifications ................................................................ 10 Serial Port Interface (SPI) .............................................................. 29 Absolute Maximum Ratings ..................................................... 11 Configuration Using the SPI ..................................................... 29 Thermal Characteristics ............................................................ 11 Hardware Interface..................................................................... 29 ESD Caution ................................................................................ 11 Memory Map .................................................................................. 30 Pin Configuration and Function Descriptions ........................... 12 Reading the Memory Map Register Table............................... 30 Typical Performance Characteristics ........................................... 14 Memory Map Register Table ..................................................... 31 Equivalent Circuits ......................................................................... 18 Memory Map Register Descriptions ........................................ 33 Theory of Operation ...................................................................... 19 Applications Information .............................................................. 35 ADC Architecture ...................................................................... 19 Design Guidelines ...................................................................... 35 Analog Input Considerations.................................................... 19 Packaging and Ordering Information ......................................... 36 Clock Input Considerations ...................................................... 21 Outline Dimensions ................................................................... 36 Power Dissipation and Standby Mode ..................................... 23 Ordering Guide .......................................................................... 36 REVISION HISTORY 10/11—Revision 0: Initial Version Rev. 0 | Page 2 of 36 Data Sheet AD6657A With the NSR block disabled, the ADC data is provided directly to the output with a resolution of 11 bits. The AD6657A can achieve up to 66.5 dBFS SNR for the entire Nyquist bandwidth when operated in this mode. This allows the AD6657A to be used in telecommunication applications such as a digital predistortion observation path where wider bandwidths are used. (CSP_BGA) that is specified over the industrial temperature range of −40°C to +85°C. After digital signal processing, multiplexed output data is routed into two 11-bit output ports such that the maximum digital data rate (DDR) is 400 Mbps. These outputs are set at 1.8 V LVDS and support ANSI-644 levels. 2. PRODUCT HIGHLIGHTS 1. 3. The AD6657A receiver digitizes a wide spectrum of IF frequencies. Each receiver is designed for simultaneous reception of a separate antenna. This IF sampling architecture greatly reduces component cost and complexity compared with traditional analog techniques or less integrated digital methods. 4. 5. 6. Flexible power-down options allow significant power savings. Programming for device setup and control is accomplished using a 3-wire SPI-compatible serial interface with numerous modes to support board level system testing. 7. The AD6657A is available in a Pb-free, RoHS compliant, 144-ball, 10 mm × 10 mm chip scale package ball grid array Rev. 0 | Page 3 of 36 Four analog-to-digital converters (ADCs) are contained in a small, space-saving, 10 mm × 10 mm × 1.4 mm, 144-ball CSP_BGA package. Pin selectable noise shaping requantizer (NSR) function that allows for improved SNR within a reduced bandwidth of up to 65 MHz at 185 MSPS. LVDS digital output interface configured for low cost FPGA families. 230 mW per ADC core power consumption. Operation from a single 1.8 V supply. Standard SPI that supports various product features and functions, such as data formatting (offset binary or twos complement), NSR, power-down, test modes, and voltage reference mode. On-chip integer 1-to-8 input clock divider and multichip sync function to support a wide range of clocking schemes and multichannel subsystems. AD6657A Data Sheet SPECIFICATIONS DC SPECIFICATIONS AVDD = 1.8 V, DRVDD = 1.8 V, fS = 185 MSPS, 1.75 V p-p differential input, VIN = −1.0 dBFS differential input, and default SPI, unless otherwise noted. Table 1. Parameter RESOLUTION ACCURACY No Missing Codes Offset Error Gain Error Differential Nonlinearity (DNL) 1 Integral Nonlinearity (INL)1 MATCHING CHARACTERISTIC Offset Error Gain Error TEMPERATURE DRIFT Offset Error Gain Error ANALOG INPUT Input Range Input Common-Mode Voltage Input Resistance (Differential) Input Capacitance 2 POWER SUPPLIES Supply Voltage AVDD DRVDD Supply Current IAVDD1 IDRVDD1 (1.8 V LVDS) POWER CONSUMPTION Sine Wave Input1 Standby Power 3 Power-Down Power 1 2 3 Temperature Full Min 11 Typ Max Unit Bits Full Full Full Full Full −0.9 +4 −0.4 −0.55 Guaranteed +0.1 +11 ±0.1 ±0.17 +0.9 +18 +0.4 +0.55 mV % FSR LSB LSB Full Full −5 0 +3 +2.1 +11 +8 mV % FSR Full Full 2 40 ppm/°C ppm/°C Full Full Full Full 1.4 1.75 0.95 20 5 2.0 V p-p V kΩ pF Full Full 1.7 1.7 1.8 1.8 1.9 1.9 V V Full Full 466 170 510 183 mA mA Full Full Full 1145 129 3.8 1247 mW mW mW Measured with a 10 MHz, 0 dBFS sine wave, with 100 Ω termination on each LVDS output pair. Input capacitance refers to the effective capacitance between one differential input pin and AGND. Standby power is measured with a dc input and the CLKx pins inactive (set to AVDD or AGND). Rev. 0 | Page 4 of 36 10 Data Sheet AD6657A AC SPECIFICATIONS AVDD = 1.8 V, DRVDD = 1.8 V, fS = 185 MSPS, 1.75 V p-p differential input, VIN = −1.0 dBFS differential input, and default SPI, unless otherwise noted. Table 2. Parameter 1 SIGNAL-TO-NOISE-RATIO (SNR)—NSR DISABLED fIN = 10 MHz fIN = 50 MHz fIN = 70 MHz fIN = 170 MHz fIN = 250 MHz SIGNAL-TO-NOISE-RATIO (SNR)—NSR ENABLED 22% BW Mode fIN = 10 MHz fIN = 50 MHz fIN = 70 MHz fIN = 170 MHz fIN = 250 MHz 33% BW Mode fIN = 10 MHz fIN = 50 MHz fIN = 70 MHz fIN = 170 MHz fIN = 230 MHz 36% BW Mode fIN = 10 MHz fIN = 50 MHz fIN = 70 MHz fIN = 170 MHz fIN = 250 MHz SIGNAL-TO-NOISE-AND DISTORTION (SINAD) fIN = 10 MHz fIN = 50 MHz fIN = 70 MHz fIN = 170 MHz fIN = 250 MHz EFFECTIVE NUMBER OF BITS (ENOB) fIN = 10 MHz fIN = 50 MHz fIN = 70 MHz fIN = 170 MHz fIN = 250 MHz Temperature 25°C 25°C 25°C 25°C Full 25°C 25°C 25°C 25°C 25°C Full 25°C 25°C 25°C 25°C 25°C Full 25°C 25°C 25°C 25°C 25°C Full 25°C 25°C 25°C 25°C 25°C Full 25°C 25°C 25°C 25°C 25°C 25°C Rev. 0 | Page 5 of 36 Min Typ 66.6 66.5 66.5 66.3 65.6 65.9 76.0 75.7 75.7 74.3 72.9 72.8 73.6 73.6 73.3 72.5 71.3 71.2 72.8 72.6 72.6 71.8 70.7 70.8 65.5 65.5 65.5 65.3 Max Unit dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS 64.8 dBFS dBFS dBFS dBFS dBFS dBFS 10.6 10.6 10.6 10.6 10.5 Bits Bits Bits Bits Bits 64.6 AD6657A Parameter 1 WORST SECOND OR THIRD HARMONIC fIN = 10 MHz fIN = 50 MHz fIN = 70 MHz fIN = 170 MHz fIN = 250 MHz SPURIOUS-FREE DYNAMIC RANGE (SFDR) fIN = 10 MHz fIN = 50 MHz fIN = 70 MHz fIN = 170 MHz fIN = 250 MHz WORST OTHER HARMONIC (FOURTH THROUGH EIGHTH) fIN = 10 MHz fIN = 50 MHz fIN = 70 MHz fIN = 170 MHz fIN = 250 MHz TWO TONE SFDR (−7 dBFS) fIN1 = 169 MHz, fIN2 = 172 MHz CROSSTALK 2 ANALOG INPUT BANDWIDTH 1 2 Data Sheet Temperature Min Typ 25°C 25°C 25°C 25°C Full 25°C −94 −91 −88 −90 25°C 25°C 25°C 25°C Full 25°C 94 91 88 90 Max −80 −83 Unit dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc 80 83 25°C 25°C 25°C 25°C Full 25°C −94 −95 −94 −94 −90 dBc dBc dBc dBc dBc dBc 25°C Full 25°C 89 95 800 dBc dB MHz −80 See the AN-835 Application Note, Understanding High Speed ADC Testing and Evaluation, for a complete set of definitions. Crosstalk is measured at 155 MHz with −1 dBFS on one channel and no input on the alternate channel. Rev. 0 | Page 6 of 36 Data Sheet AD6657A DIGITAL SPECIFICATIONS AVDD = 1.8 V, DRVDD = 1.8 V, fS = 185 MSPS, 1.75 V p-p differential input, VIN = −1.0 dBFS differential input, and default SPI, unless otherwise noted. Table 3. Parameter DIFFERENTIAL CLOCK INPUTS (CLK+, CLK−) Logic Compliance Internal Common-Mode Bias Differential Input Voltage Input Voltage Range High Level Input Voltage Low Level Input Voltage High Level Input Current Low Level Input Current Input Resistance Input Capacitance SYNC INPUT Logic Compliance Internal Bias Input Voltage Range High Level Input Voltage Low Level Input Voltage High Level Input Current Low Level Input Current Input Resistance Input Capacitance LOGIC INPUT (CSB) 1 High Level Input Voltage Low Level Input Voltage High Level Input Current Low Level Input Current Input Resistance Input Capacitance LOGIC INPUT (SCLK) 2 High Level Input Voltage Low Level Input Voltage High Level Input Current Low Level Input Current Input Resistance Input Capacitance LOGIC INPUT/OUTPUT (SDIO)2 High Level Input Voltage Low Level Input Voltage High Level Input Current Low Level Input Current Input Resistance Input Capacitance Temperature Full Full Full Full Full Full Full Full Full Full Full Full Full Full Full Full Full Min Typ Max Unit 3.6 AVDD + 0.2 2.0 0.8 +10 +10 12 V V p-p V V V µA µA kΩ pF AVDD AVDD 0.6 +100 +100 20 V V V V µA µA kΩ pF CMOS/LVDS/LVPECL 0.9 0.2 AGND − 0.3 1.2 0 −10 −10 8 10 4 CMOS 0.9 AGND 1.2 AGND −100 −100 12 Full Full Full Full Full Full 1.22 0 −10 40 Full Full Full Full Full Full 1.22 0 −92 −10 Full Full Full Full Full Full 1.22 0 −10 38 16 1 2.1 0.6 +10 132 V V µA µA kΩ pF 2.1 0.6 −135 +10 V V µA µA kΩ pF 2.1 0.6 +10 128 V V µA µA kΩ pF 26 2 26 2 26 5 Rev. 0 | Page 7 of 36 AD6657A Parameter LOGIC INPUT (MODE)1 High Level Input Voltage Low Level Input Voltage High Level Input Current Low Level Input Current Input Resistance Input Capacitance LOGIC INPUT (PDWN)2 High Level Input Voltage Low Level Input Voltage High Level Input Current Low Level Input Current Input Resistance Input Capacitance DIGITAL OUTPUTS (LVDS) Differential Output Voltage (VOD) Output Offset Voltage (VOS) 1 2 Data Sheet Temperature Min Full Full Full Full Full Full 1.22 0 −10 40 Full Full Full Full Full Full 1.22 0 −90 −10 Full Full 247 1.125 Typ Max Unit 2.1 0.6 +10 132 V V μA μA kΩ pF 2.1 0.6 −134 +10 V V μA μA kΩ pF 454 1.375 mV V 26 2 26 5 Pull up. Pull down. Rev. 0 | Page 8 of 36 Data Sheet AD6657A SWITCHING SPECIFICATIONS AVDD = 1.8 V, DRVDD = 1.8 V, fS = 185 MSPS, 1.75 V p-p differential input, VIN = −1.0 dBFS differential input, and default SPI, unless otherwise noted. Table 4. Parameter CLOCK INPUT PARAMETERS Input Clock Rate Conversion Rate 1 CLK Pulse Width High (tCH) 2 Aperture Delay (tA)2 Aperture Uncertainty (Jitter, tJ) DATA OUTPUT PARAMETERS Data Propagation Delay (tPD)2 DCO Propagation Delay (tDCO)2 DCO to Data Skew (tSKEW)2 Pipeline Delay (Latency) With NSR Enabled Wake-Up Time (from Standby) 3 Wake-Up Time (from Power Down)3 OUT-OF-RANGE RECOVERY TIME 1 2 3 Temperature Full Full Full Full Full Full Full Full Full Full Full Full Full Min Typ 40 185 2.7 1.3 0.13 3.0 3.1 −41 4.0 4.0 +6.1 9 12 0.5 310 2 Max Unit 625 200 MHz MSPS ns ns ps rms 4.9 4.9 +33 ns ns ns Cycles Cycles µs µs Cycles Conversion rate is the clock rate after the divider. See Figure 2 for details. Wake-up time is dependent on the value of the decoupling capacitors. Data Output Timing Diagram tA N–1 N+4 N+5 N N+3 VIN N+1 tCH tCL N+2 1/fS CLK+ CLK– tDCO DCO+ DCO– tSKEW tPD D10+AB (MSB) D10A D10B D10A D10B D10A D10B D10A D10B D10A D10B D10A D10B D10A D10B D0A D0B D0A D0B D0A D0B D0A D0B D0A D0B D0A D0B D0A D0B D0+AB (LSB) D0–AB (LSB) Figure 2. Data Output Timing (Timing for Channel C and Channel D Is Identical to Timing for Channel A and Channel B) Rev. 0 | Page 9 of 36 09684-002 D10–AB (MSB) AD6657A Data Sheet TIMING SPECIFICATIONS AVDD = 1.8 V, DRVDD = 1.8 V, fS = 185 MSPS, 1.75 V p-p differential input, VIN = −1.0 dBFS differential input, and default SPI, unless otherwise noted. Table 5. Parameter SYNC TIMING REQUIREMENTS tSSYNC tHSYNC SPI TIMING REQUIREMENTS tDS tDH tCLK tS tH tHIGH tLOW tEN_SDIO tDIS_SDIO Description See Figure 3 for details SYNC to rising edge of CLK setup time SYNC to rising edge of CLK hold time See Figure 60 for details, except where noted 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 SCLK pulse width high SCLK pulse width low Time required for the SDIO pin to switch from an input to an output relative to the SCLK falling edge (not pictured in Figure 60) Time required for the SDIO pin to switch from an output to an input relative to the SCLK rising edge (not pictured in Figure 60) Min Typ 0.24 0.40 10 ns 09684-003 tHSYNC Figure 3. SYNC Input Timing Requirements Rev. 0 | Page 10 of 36 ns ns ns ns ns ns ns ns ns ns CLK+ SYNC Unit 2 2 40 2 2 10 10 10 Sync Input Timing Diagram tSSYNC Max Data Sheet AD6657A ABSOLUTE MAXIMUM RATINGS THERMAL CHARACTERISTICS Table 6. Parameter AVDD to AGND DRVDD to AGND VIN+x, VIN−x to AGND CLK+, CLK− to AGND SYNC to AGND VCMx to AGND CSB to AGND SCLK to AGND SDIO to AGND PDWN to AGND MODE to AGND Digital Outputs to AGND DCO+AB, DCO−AB, DCO+CD, DCO−CD to AGND Operating Temperature Range (Ambient) Maximum Junction Temperature Under Bias Storage Temperature Range (Ambient) Rating −0.3 V to +2.0 V −0.3 V to +2.0 V −0.3 V to AVDD + 0.2 V −0.3 V to AVDD + 0.2 V −0.3 V to AVDD + 0.2 V −0.3 V to AVDD + 0.2 V −0.3 V to DRVDD + 0.2 V −0.3 V to DRVDD + 0.2 V −0.3 V to DRVDD + 0.2 V −0.3 V to DRVDD + 0.2 V −0.3 V to DRVDD + 0.2 V −0.3 V to DRVDD + 0.2 V −0.3 V to DRVDD + 0.2 V The values in Table 7 are per JEDEC JESD51-7 and JEDEC JESD25-5 for a 2S2P test board. Typical θJA is specified for a 4-layer printed circuit board (PCB) with a solid ground plane. As shown in Table 7, airflow improves heat dissipation, which reduces θJA. In addition, metal in direct contact with the package leads from metal traces, through holes, ground, and power planes reduces θJA. Table 7. Package Type 144-Ball CSP_BGA Airflow Velocity 0 m/s 1 m/s 2.5 m/s θJA1 26.9 24.2 23.0 θJC2 8.9 θJB3 6.6 Unit °C/W °C/W °C/W 1 Per JEDEC JESD51-2 (still air) or JEDEC JESD51-6 (moving air). Per MIL-STD 883, Method 1012.1. 3 Per JEDEC JESD51-8 (still air). 2 −40°C to +85°C The values in Table 8 are from simulations. The PCB is a JEDEC multilayer board. Thermal performance for actual applications requires careful inspection of the conditions in the application to determine whether they are similar to those assumed in these calculations. 150°C −65°C to +150°C Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Table 8. Package Type 144-Ball CSP_BGA ESD CAUTION Rev. 0 | Page 11 of 36 Airflow Velocity 0 m/s 1 m/s 2.5 m/s JB 14.4 14.0 13.9 JT 0.23 0.50 0.53 Unit °C/W °C/W °C/W AD6657A Data Sheet 1 2 3 4 5 6 7 8 9 10 11 12 A AGND VIN+C VIN–C AGND AVDD CLK– CLK+ AVDD AGND VIN–B VIN+B AGND B AGND AGND VCMC AGND AVDD AVDD AVDD AVDD AGND VCMB AGND AGND C VIN+D AGND AGND CSB SDIO SCLK PDWN SYNC MODE AGND AGND VIN+A D VIN–D VCMD AGND AVDD AVDD AVDD AVDD AVDD AVDD AGND VCMA VIN–A E AGND AVDD AVDD AVDD AVDD AVDD AVDD AVDD AVDD AVDD AVDD AGND F AGND AGND AGND AGND AGND AGND AGND AGND AGND AGND AGND AGND G DRGND DRGND DRGND DRGND DRGND DRGND DRGND DRGND DRGND DRGND DRGND DRGND H DRVDD DRVDD DRVDD DRVDD DRVDD DRVDD DRVDD DRVDD DRVDD DRVDD DRVDD DRVDD J D0–CD D2–CD D4–CD D6–CD D8–CD D10–CD D0–AB D2–AB D4–AB D6–AB D8–AB D10–AB K D0+CD D2+CD D4+CD D6+CD D8+CD D10+CD D0+AB D2+AB D4+AB D6+AB D8+AB D10+AB L D1–CD D3–CD D5–CD D7–CD D9–CD DCO–CD D1–AB D3–AB D5–AB D7–AB D9–AB DCO–AB M D1+CD D3+CD D5+CD D7+CD D9+CD DCO+CD D1+AB D3+AB D5+AB D7+AB D9+AB DCO+AB 09684-004 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS Figure 4. Pin Configuration (Top View) Table 9. Pin Function Descriptions Pin No. A5, A8, B5 to B8, D4 to D9, E2 to E11 A1, A4, A9, A12, B1, B2, B4, B9, B11, B12, C2, C3, C10, C11, D3, D10, E1, E12, F1 to F12 H1 to H12 G1 to G12 A7 A6 C12 D12 D11 A11 A10 B10 A2 A3 B3 C1 D1 D2 K7 J7 M7 L7 K8 J8 M8 L8 K9 J9 Mnemonic AVDD Type Supply Description Analog Power Supply. 1.8 V nominal. AGND Ground Analog Ground. DRVDD DRGND CLK+ CLK− VIN+A VIN−A VCMA VIN+B VIN−B VCMB VIN+C VIN−C VCMC VIN+D VIN−D VCMD D0+AB D0−AB D1+AB D1−AB D2+AB D2−AB D3+AB D3−AB D4+AB D4−AB Supply Ground Input Input Input Input Output Input Input Output Input Input Output Input Input Output Output Output Output Output Output Output Output Output Output Output Digital Output Driver Supply. 1.8 V nominal. Digital Output Driver Ground. ADC Clock Input—True. ADC Clock Input—Complement. Differential Analog Input Pin (+) for Channel A. Differential Analog Input Pin (−) for Channel A. Common-Mode Level Bias Output for Analog Input Channel A. Differential Analog Input Pin (+) for Channel B. Differential Analog Input Pin (−) for Channel B. Common-Mode Level Bias Output for Analog Input Channel B. Differential Analog Input Pin (+) for Channel C. Differential Analog Input Pin (−) for Channel C. Common-Mode Level Bias Output for Analog Input Channel C. Differential Analog Input Pin (+) for Channel D. Differential Analog Input Pin (−) for Channel D. Common-Mode Level Bias Output for Analog Input Channel D. Channel A and Channel B LVDS Output Data 0—True. Channel A and Channel B LVDS Output Data 0—Complement. Channel A and Channel B LVDS Output Data 1—True. Channel A and Channel B LVDS Output Data 1—Complement. Channel A and Channel B LVDS Output Data 2—True. Channel A and Channel B LVDS Output Data 2—Complement. Channel A and Channel B LVDS Output Data 3—True. Channel A and Channel B LVDS Output Data 3—Complement. Channel A and Channel B LVDS Output Data 4—True. Channel A and Channel B LVDS Output Data 4—Complement. Rev. 0 | Page 12 of 36 Data Sheet Pin No. M9 L9 K10 J10 M10 L10 K11 J11 M11 L11 K12 J12 M12 L12 K1 J1 M1 L1 K2 J2 M2 L2 K3 J3 M3 L3 K4 J4 M4 L4 K5 J5 M5 L5 K6 J6 M6 L6 C9 C8 C7 C6 C5 C4 AD6657A Mnemonic D5+AB D5−AB D6+AB D6−AB D7+AB D7−AB D8+AB D8−AB D9+AB D9−AB D10+AB D10−AB DCO+AB DCO−AB D0+CD D0−CD D1+CD D1−CD D2+CD D2−CD D3+CD D3−CD D4+CD D4−CD D5+CD D5−CD D6+CD D6−CD D7+CD D7−CD D8+CD D8−CD D9+CD D9−CD D10+CD D10−CD DCO+CD DCO−CD MODE SYNC PDWN SCLK SDIO CSB Type Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Output Input Input Input Input Input/Output Input Description Channel A and Channel B LVDS Output Data 5—True. Channel A and Channel B LVDS Output Data 5—Complement. Channel A and Channel B LVDS Output Data 6—True. Channel A and Channel B LVDS Output Data 6—Complement. Channel A and Channel B LVDS Output Data 7—True. Channel A and Channel B LVDS Output Data 7—Complement. Channel A and Channel B LVDS Output Data 8—True. Channel A and Channel B LVDS Output Data 8—Complement. Channel A and Channel B LVDS Output Data 9—True. Channel A and Channel B LVDS Output Data 9—Complement. Channel A and Channel B LVDS Output Data 10—True. Channel A and Channel B LVDS Output Data 10—Complement. Data Clock LVDS Output for Channel A and Channel B—True. Data Clock LVDS Output for Channel A and Channel B—Complement. Channel C and Channel D LVDS Output Data 0—True. Channel C and Channel D LVDS Output Data 0—Complement. Channel C and Channel D LVDS Output Data 1—True. Channel C and Channel D LVDS Output Data 1—Complement. Channel C and Channel D LVDS Output Data 2—True. Channel C and Channel D LVDS Output Data 2—Complement. Channel C and Channel D LVDS Output Data 3—True. Channel C and Channel D LVDS Output Data 3—Complement. Channel C and Channel D LVDS Output Data 4—True. Channel C and Channel D LVDS Output Data 4—Complement. Channel C and Channel D LVDS Output Data 5—True. Channel C and Channel D LVDS Output Data 5—Complement. Channel C and Channel D LVDS Output Data 6—True. Channel C and Channel D LVDS Output Data 6—Complement. Channel C and Channel D LVDS Output Data 7—True. Channel C and Channel D LVDS Output Data 7—Complement. Channel C and Channel D LVDS Output Data 8—True. Channel C and Channel D LVDS Output Data 8—Complement. Channel C and Channel D LVDS Output Data 9—True. Channel C and Channel D LVDS Output Data 9—Complement. Channel C and Channel D LVDS Output Data 10—True. Channel C and Channel D LVDS Output Data 10—Complement. Data Clock LVDS Output for Channel C and Channel D—True. Data Clock LVDS Output for Channel C and Channel D—Complement. Mode Select Pin. Logic low enables NSR; logic high disables NSR. Digital Synchronization Pin. Power-Down Input (Active High). SPI Clock. SPI Data. SPI Chip Select (Active Low). Rev. 0 | Page 13 of 36 AD6657A Data Sheet TYPICAL PERFORMANCE CHARACTERISTICS AVDD = 1.8 V, DRVDD = 1.8 V, sample rate = 185 MSPS, 1.75 V p-p differential input, VIN = −1.0 dBFS, 32,000 sample, TA = 25°C, unless otherwise noted. 0 185MSPS 140.3MHz @ –1dBFS SNR = 65.4dB (66.4dBFS) SFDR = 90dBc –20 AMPLITUDE (dBFS) –20 –40 –60 SECOND HARMONIC THIRD HARMONIC –80 –40 –60 THIRD HARMONIC SECOND HARMONIC –80 0 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) –120 09684-005 –120 0 Figure 5. Single Tone FFT, fIN = 10.3 MHz 0 0 –40 –60 THIRD HARMONIC –80 185MSPS 200.3MHz @ –1dBFS SNR = 64.9dB (65.9dBFS) SFDR = 84dBc –20 AMPLITUDE (dBFS) SECOND HARMONIC –100 –40 –60 THIRD HARMONIC SECOND HARMONIC –80 –100 0 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) –120 09684-006 –120 0 Figure 6. Single Tone FFT, fIN = 50.3 MHz Figure 9. Single Tone FFT, fIN = 200.3 MHz 0 0 185MSPS 70.3MHz @ –1dBFS SNR = 65.5dB (66.5dBFS) –20 SFDR = 88dBc 185MSPS 230.3MHz @ –1dBFS SNR = 66.1dB (65.1dBFS) SFDR = 84dBc AMPLITUDE (dBFS) –20 –40 –60 SECOND HARMONIC THIRD HARMONIC –80 –100 –40 –60 SECOND HARMONIC THIRD HARMONIC –80 –100 –120 0 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) 09684-007 AMPLITUDE (dBFS) 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) 09684-009 AMPLITUDE (dBFS) Figure 8. Single Tone FFT, fIN = 140.3 MHz 185MSPS 50.3MHz @ –1dBFS SNR = 65.6dB (66.6dBFS) SFDR = 92.0dBc –20 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) 09684-008 –100 –100 Figure 7. Single Tone FFT, fIN = 70.3 MHz –120 0 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) Figure 10. Single Tone FFT, fIN = 230.3 MHz Rev. 0 | Page 14 of 36 09684-010 AMPLITUDE (dBFS) 0 185MSPS 10.3MHz @ –1dBFS SNR = 65.6dB (66.6dBFS) SFDR = 94.0dBc Data Sheet AD6657A 0 0 185MSPS 247.3MHz @ –1dBFS SNR = 66dB (65dBFS) –20 SFDR = 83dBc 185MSPS 230.3MHz @ –1dBFS NSR 33% BW MODE, TW = 17 SNR = 70.8dB (72.5dBFS) SFDR = 93.7dBc –20 AMPLITUDE (dBFS) SECOND HARMONIC –60 THIRD HARMONIC –80 –100 SECOND HARMONIC –60 THIRD HARMONIC –80 –100 –120 0 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) –140 09684-011 –120 0 Figure 11. Single Tone FFT, fIN = 247.3 MHz 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) 09684-014 AMPLITUDE (dBFS) –40 –40 Figure 14. Single Tone FFT, fIN = 230.3 MHz, NSR Enabled in 33% BW Mode, Tuning Word = 17 0 0 185MSPS 305.3MHz @ –1dBFS SNR = 64.9dB (65.9dBFS) –20 SFDR = 80dBc 185MSPS 230.3MHz @ –1dBFS NSR 36% BW MODE, TW = 14 SNR = 70.3dB (71.3dBFS) SFDR = 93.4dBc –20 AMPLITUDE (dBFS) THIRD HARMONIC –60 SECOND HARMONIC –80 –100 –60 –100 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) –140 0 Figure 12. Single Tone FFT, fIN = 305.3 MHz 0 Figure 15. Single Tone FFT, fIN = 230.3 MHz, NSR Enabled in 36% BW Mode, Tuning Word = 14 100 185MSPS 140.3MHz @ –1dBFS NSR 22% BW MODE, TW = 28 SNR = 73.4dB (74.9dBFS) SFDR = 91dBc 90 SFDR (dBFS) 80 SNR/SFDR (dBc AND dBFS) –20 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) –40 –60 THIRD HARMONIC –80 –100 SNR (dBFS) 70 60 50 SFDR (dBc) 40 30 SNR (dBc) 20 –120 INPUT AMPLITUDE (dBFS) Figure 16. Single Tone SNR/SFDR vs. Input Amplitude (AIN), fIN = 70.3 MHz Figure 13. Single Tone FFT, fIN = 140.3 MHz, NSR Enabled in 22% BW Mode, Tuning Word = 28 Rev. 0 | Page 15 of 36 0 09684-016 –5 –10 –15 –20 –25 –30 –35 –40 –45 –50 –55 –60 –65 –70 0 –75 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) –80 0 –85 –140 09684-013 10 09684-015 0 09684-012 –120 –120 AMPLITUDE (dBFS) THIRD HARMONIC –80 –90 AMPLITUDE (dBFS) –40 –40 AD6657A Data Sheet 100 100 90 95 SFDR (dBFS) SFDR (dBc) 90 SNR/SFDR (dBFS AND dBc) SNR (dBFS) 70 60 50 SFDR (dBc) 40 30 SNR (dBc) 20 10 80 75 70 SNR (dBFS) 65 60 0 INPUT AMPLITUDE (dBFS) 50 30.00 09684-017 –5 –10 –15 –20 –25 –30 –35 –40 –45 –50 –55 –60 –65 –70 –75 –80 55 –85 –90 0 85 Figure 17. Single Tone SNR/SFDR vs. Input Amplitude (AIN), fIN = 140.3 MHz 51.25 72.50 93.75 115.00 136.25 157.50 178.75 200.00 SAMPLE RATE (MSPS) 09684-020 SNR/SFDR (dBc AND dBFS) 80 Figure 20. Single Tone SNR/SFDR vs. Sample Rate (fS), fIN = 70.3 MHz 95 95 SFDR (dBc) 90 SNR/SFDR (dBFS AND dBc) 85 80 75 70 SNR (dBFS) 65 75 70 65 SNR (dBFS) 60 Figure 18. Single Tone SNR/SFDR vs. Input Frequency (fIN), 1.75 V p-p Full Scale 51.25 72.50 93.75 115.00 136.25 157.50 178.75 200.00 SAMPLE RATE (MSPS) 09684-021 50 30.00 09684-018 400 380 360 340 320 300 280 260 240 220 200 180 160 140 120 100 INPUT FREQUENCY (MHz) Figure 21. Single Tone SNR/SFDR vs. Sample Rate (fS), fIN = 140.3 MHz 95 0 90 185MSPS 169.1MHz @ –7dBFS 172.1MHz @ –7dBFS SFDR = 88.5dBc –20 SFDR (dBc) AMPLITUDE (dBFS) 85 80 75 70 –40 –60 –80 SNR (dBFS) 09684-019 INPUT FREQUENCY (MHz) 400 380 360 340 320 300 280 260 240 220 200 180 160 140 –120 120 60 100 –100 80 65 60 SNR/SFDR (dBFS AND dBc) SFDR (dBc) 80 55 80 60 60 85 0 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) Figure 22. Two Tone FFT, fIN1 = 169.1 MHz and fIN2 = 172.1 MHz Figure 19. Single Tone SNR/SFDR vs. Input Frequency (fIN), 2.0 V p-p Full Scale Rev. 0 | Page 16 of 36 09684-122 SNR/SFDR (dBFS AND dBc) 90 Data Sheet AD6657A 0.20 0 0.15 0.10 SFDR (dBc) –40 DNL ERROR (LSB) SFDR/IMD3 (dBc AND dBFS) –20 IMD3 (dBc) –60 –80 0.05 0 –0.05 SFDR (dBFS) –0.10 –100 –0.15 –78 –66 –54 –42 –30 INPUT AMPLITUDE (dBFS) –18 –6 –0.20 09684-123 –120 –90 0 500 Figure 23. Two Tone SFDR/IMD3 vs. Input Amplitude (AIN), fIN1 = 169.1 MHz and fIN2 = 172.1 MHz 1000 OUTPUT CODE 1500 2000 09684-126 IMD3 (dBFS) Figure 26. DNL, fIN = 30.3 MHz 69 2,500,000 68 67 66 1,500,000 SNR (dBFS) NUMBER OF HITS 2,000,000 1,000,000 65 64 63 62 500,000 N–3 N–2 N–1 N N+1 OUTPUT CODE N+2 09684-124 0 N+3 Figure 24. Grounded Input Histogram 0.8 0.6 0.2 0 –0.2 –0.4 –0.6 –0.8 –1.0 1000 OUTPUT CODE 1500 2000 09684-125 INL ERROR (LSB) 0.4 500 35 40 45 50 55 DUTY CYCLE (%) 60 65 Figure 27. SNR vs. Duty Cycle, fIN = 10.3 MHz 1.0 0 60 30 Figure 25. INL, fIN = 30.3 MHz Rev. 0 | Page 17 of 36 70 09684-127 61 AD6657A Data Sheet EQUIVALENT CIRCUITS AVDD 350Ω SCLK OR PDWN 30kΩ 09684-022 09684-026 VIN Figure 28. Equivalent Analog Input Circuit Figure 32. Equivalent SCLK and PDWN Input Circuit AVDD AVDD AVDD 30kΩ AVDD 0.9V 15kΩ CLK– 09684-023 09684-027 15kΩ CLK+ 350Ω CSB OR MODE Figure 33. Equivalent CSB and MODE Input Circuit Figure 29. Equivalent Clock Input Circuit DRVDD DRVDD V+ V– DATAOUT+ V– SDIO V+ 350Ω 09684-024 30kΩ Figure 34. Equivalent SDIO Circuit Figure 30. Equivalent LVDS Output Circuit AVDD AVDD SYNC 0.9V 08557-025 16kΩ 0.9V Figure 31. Equivalent SYNC Input Circuit Rev. 0 | Page 18 of 36 09684-028 DATAOUT– Data Sheet AD6657A THEORY OF OPERATION The AD6657A architecture consists of a quad front-end sampleand-hold circuit, followed by a pipelined, switched capacitor ADC. The quantized outputs from each stage are combined into a final 14-bit result in the digital correction logic. Alternately, the 14-bit result can be processed through the NSR block before it is sent to the digital correction logic. The pipelined architecture permits the first stage to operate on a new input sample and the remaining stages to operate on the preceding samples. Sampling occurs on the rising edge of the clock. Each stage of the pipeline, excluding the last, consists of a low resolution flash ADC connected to a switched-capacitor digitalto-analog converter (DAC) and an interstage residue amplifier (MDAC). The residue amplifier magnifies the difference between the reconstructed DAC output and the flash input for the next stage in the pipeline. One bit of redundancy is used in each stage to facilitate digital correction of flash errors. The last stage simply consists of a flash ADC. The input stage of each channel contains a differential sampling circuit that can be ac- or dc-coupled in differential or single-ended modes. The output staging block aligns the data, corrects errors, and passes the data to the output buffers. The output buffers are powered from a separate supply, allowing adjustment of the output drive current. During power-down, the output buffers go into a high impedance state. A small resistor in series with each input can help reduce the peak transient current required from the output stage of the driving source. A shunt capacitor can be placed across the inputs to provide dynamic charging currents. This passive network creates a low-pass filter at the ADC input; therefore, the precise values are dependent on the application. In intermediate frequency (IF) undersampling applications, any shunt capacitors should be reduced. In combination with the driving source impedance, the shunt capacitors limit the input bandwidth. For more information on this subject, see the AN-742 Application Note, Frequency Domain Response of Switched-Capacitor ADCs; AN-827 Application Note, A Resonant Approach to Interfacing Amplifiers to Switched-Capacitor ADCs; and the Analog Dialogue article, “Transformer-Coupled Front-End for Wideband A/D Converters” (see www.analog.com). BIAS S S CFB CS VIN+ CPAR2 CPAR1 H S S CS VIN– CPAR1 CPAR2 S CFB S BIAS 09684-029 ADC ARCHITECTURE Figure 35. Switched Capacitor Input The AD6657A quad IF receiver can simultaneously digitize four channels, making it ideal for diversity reception and digital predistortion (DPD) observation paths in telecommunication systems. For best dynamic performance, match the source impedances driving the VIN+ and VIN− pins. Synchronization capability is provided to allow synchronized timing between multiple channels or multiple devices. An internal differential reference buffer creates positive and negative reference voltages that define the input span of the ADC core. The span of the ADC core is set by this buffer to 2 × VREF. Programming and control of the AD6657A are accomplished using a 3-wire SPI-compatible serial interface. ANALOG INPUT CONSIDERATIONS The analog input to the AD6657A is a differential switched capacitor circuit that has been designed for optimum performance while processing a differential input signal. The clock signal alternatively switches the input between sample mode and hold mode (see Figure 35). When the input is switched to sample mode, the signal source must be capable of charging the sample capacitors and settling within 1/2 of a clock cycle. Input Common Mode The analog inputs of the AD6657A are not internally dc biased. In ac-coupled applications, the user must provide this bias externally. An on-board common-mode voltage reference is included in the design and is available from the VCMx pins. Optimum performance is achieved when the common-mode voltage of the analog input is set by the VCMx pin voltage (typically 0.5 × AVDD). The VCMx pins must be decoupled to ground by a 0.1 µF capacitor. Rev. 0 | Page 19 of 36 AD6657A Data Sheet Differential Input Configurations The signal characteristics must be considered when selecting a transformer. Most RF transformers saturate at frequencies below a few megahertz (MHz). Excessive signal power can also cause core saturation, which leads to distortion. Optimum performance is achieved when driving the AD6657A in a differential input configuration. For baseband applications, the AD8138, ADA4937-2, and ADA4938-2 differential drivers provide excellent performance and a flexible interface to the ADC. At input frequencies in the second Nyquist zone and above, the noise performance of most amplifiers is not adequate to achieve the true SNR performance of the AD6657A. For applications in which SNR is a key parameter, differential double balun coupling is the recommended input configuration (see Figure 38). In this configuration, the input is ac-coupled and the CML is provided to each input through a 33 Ω resistor. These resistors compensate for losses in the input baluns to provide a 50 Ω impedance to the driver. The output common-mode voltage of the ADA4938-2 is easily set with the VCMx pin of the AD6657A (see Figure 36), and the driver can be configured in a Sallen-Key filter topology to provide band limiting of the input signal. 15pF 200Ω 33Ω 90Ω 15Ω VIN– AVDD 5pF 33Ω 15Ω VCM VIN+ 15pF 200Ω 09684-030 120Ω In the double balun and transformer configurations, the value of the input capacitors and resistors is dependent on the input frequency and source impedance and may need to be reduced or removed. Table 10 lists recommended values to set the RC network. At higher input frequencies, good performance can be achieved by using a ferrite bead in series with a resistor and removing the capacitors. However, these values are dependent on the input signal and should be used as a starting guide only. ADC ADA4938-2 0.1µF Figure 36. Differential Input Configuration Using the ADA4938-2 For baseband applications where SNR is a key parameter, differential transformer coupling is the recommended input configuration. An example is shown in Figure 37. To bias the analog input, the VCM voltage can be connected to the center tap of the secondary winding of the transformer. Table 10. Example RC Network Frequency Range (MHz) 0 to 100 100 to 200 100 to 300 C2 R2 VIN+ R1 ADC C1 R2 R1 0.1µF 1 VCM VIN– C2 C1 Differential 5 pF 5 pF Remove Figure 37. Differential Transformer-Coupled Configuration C2 2V p-p R1 R2 VIN+ 33Ω PA S S P ADC C1 0.1µF 33Ω 0.1µF R1 R2 VIN– VCM C2 Figure 38. Differential Double Balun Input Configuration VCC ANALOG INPUT 0.1µF 0Ω 16 1 8, 13 11 0.1µF 0.1µF RD RG 3 5 0.1µF 0Ω VIN+ C AD8352 10 4 ANALOG INPUT R 200Ω 2 CD C2 Shunt (Each) 15 pF 10 pF Remove In this configuration, R1 is a ferrite bead with a value of 10 Ω @ 100 MHz. 0.1µF 0.1µF R2 Series (Each) 15 Ω 10 Ω 66 Ω An alternative to using a transformer-coupled input at frequencies in the second Nyquist zone is to use the AD8352 differential driver (see Figure 39). For more information, see the AD8352 data sheet. 09684-032 49.9Ω 09684-031 2V p-p R1 Series (Each) 33 Ω 10 Ω 10 Ω1 0.1µF 200Ω R 14 0.1µF 0.1µF Figure 39. Differential Input Configuration Using the AD8352 Rev. 0 | Page 20 of 36 ADC VIN– VCM 09684-033 76.8Ω VIN Data Sheet AD6657A ANALOG INPUT XFMR 1:4 Z ETC4-1T-7 33Ω 0.1µF 121Ω 0.1µF 0.1µF 121Ω 0.1µF 3.0kΩ 33Ω 0.1µF 3.0pF ADC INTERNAL INPUT Z VCM 09684-034 431nH INPUT Z = 50Ω Figure 40. 1:4 Transformer Passive Configuration 1000pF 180nH 220nH 1µH VPOS 301Ω AD8376 5.1pF 1nF 1µH 165Ω 15pF 3.9pF 165Ω VCM 1nF 1000pF AD6657A 3.0kΩ║3.0pF 68nH 180nH 220nH 09684-035 NOTES 1. ALL INDUCTORS ARE COILCRAFT 0603CS COMPONENTS WITH THE EXCEPTION OF THE 1µH CHOKE INDUCTORS (0603LS). Figure 41. Active Front-End Configuration Using the AD8376 For the popular IF band of 140 MHz, Figure 40 shows an example of a 1:4 transformer passive configuration where a differential inductor is used to resonate with the internal input capacitance of the AD6657A. This configuration realizes excellent noise and distortion performance. Figure 41 shows an example of an active front-end configuration using the AD8376 dual variable gain amplifier (VGA). This configuration is recommended when signal gain is required. CLOCK INPUT CONSIDERATIONS For optimum performance, clock the AD6657A sample clock inputs, CLK+ and CLK−, with a differential signal. The signal is typically ac-coupled into the CLK+ and CLK− pins via a transformer or capacitors. These pins are biased internally and require no external bias (see Figure 42). Figure 43 and Figure 44 show two preferred methods for clocking the AD6657A (at clock rates of up to 625 MHz). A low jitter clock source is converted from a single-ended signal to a differential signal using either an RF balun or an RF transformer. The RF balun configuration is recommended for clock frequencies between 125 MHz and 625 MHz, and the RF transformer configuration is recommended for clock frequencies from 10 MHz to 200 MHz. The back-to-back Schottky diodes across the transformer/balun secondary limit clock excursions into the AD6657A to approximately 0.8 V p-p differential. This limit helps to prevent the large voltage swings of the clock from feeding through to other portions of the AD6657A, yet preserves the fast rise and fall times of the signal that are critical to a low jitter performance. AVDD ADT1-1WT, 1:1Z 0.1µF XFMR 0.1µF CLOCK INPUT 1.2V ADC 0.1µF CLK– CLK– SCHOTTKY DIODES: HSMS2822 0.1µF 2pF Figure 43. Transformer-Coupled Differential Clock (Up to 200 MHz) 09684-036 2pF 09684-037 CLK+ CLK+ 100Ω 50Ω Figure 42. Equivalent Clock Input Circuit 1nF CLOCK INPUT The AD6657A has a very flexible clock input structure. The clock input can be a CMOS, LVDS, LVPECL, or sine wave signal. Regardless of the type of signal being used, clock source jitter is of the most concern (see the Jitter Considerations section). Rev. 0 | Page 21 of 36 0.1µF CLK+ 50Ω ADC 0.1µF 1nF CLK– SCHOTTKY DIODES: HSMS2822 Figure 44. Balun-Coupled Differential Clock (Up to 625 MHz) 09684-038 Clock Input Options AD6657A Data Sheet If a low jitter clock source is not available, another option is to ac couple a differential PECL signal to the sample clock input pins, as shown in Figure 45. The AD9510/AD9511/AD9512/ AD9513/AD9514/AD9515/AD9516 clock drivers offer excellent jitter performance. CLK+ can be driven directly from a CMOS gate. Although the CLK+ input circuit supply is AVDD (1.8 V), this input is designed to withstand input voltages of up to 3.6 V, making the selection of the drive logic voltage very flexible (see Figure 48). VCC 0.1µF 0.1µF CLOCK INPUT CLK+ 0.1µF CLOCK INPUT 50kΩ AD951x PECL DRIVER 100Ω 240Ω 0.1µF 100Ω ADC 0.1µF Clock Duty Cycle 09684-040 CLK– 50kΩ In some applications, it may be acceptable to drive the sample clock inputs with a single-ended CMOS signal. In such applications, drive the CLK+ pin directly from a CMOS gate, and bypass the CLK− pin to ground with a 0.1 μF capacitor in parallel with a 39 kΩ resistor (see Figure 47). 50Ω1 AD951x CMOS DRIVER OPTIONAL 0.1µF 100Ω 1kΩ CLK+ ADC 150Ω 39kΩ RESISTOR IS OPTIONAL. Figure 47. Single-Ended 1.8 V CMOS Input Clock (Up to 200 MHz) 09684-041 CLK– 0.1µF Typical high speed ADCs use both clock edges to generate a variety of internal timing signals and, as a result, may be sensitive to clock duty cycle. Commonly, a ±5% tolerance is required on the clock duty cycle to maintain dynamic performance characteristics. The AD6657A contains a DCS that retimes the nonsampling (falling) edge, providing an internal clock signal with a nominal 50% duty cycle. This allows the user to provide a wide range of clock input duty cycles without affecting the performance of the AD6657A. Noise and distortion performance are nearly flat for a wide range of duty cycles with the DCS enabled. VCC 1kΩ RESISTOR IS OPTIONAL. The AD6657A clock divider can be synchronized using the external SYNC input. Bit 1 of Register 0x3A enables the clock divider to be resynchronized on every SYNC signal. A valid SYNC causes the clock divider to reset to its initial state. This synchronization feature allows multiple parts to have their clock dividers aligned to guarantee simultaneous input sampling. 0.1µF AD951x LVDS DRIVER 150Ω Figure 48. Single-Ended 3.3 V CMOS Input Clock (Up to 200 MHz) The AD6657A contains an input clock divider with the ability to divide the input clock by integer values from 1 to 8. Figure 46. Differential LVDS Sample Clock (Up to 625 MHz) CLOCK INPUT ADC Input Clock Divider CLK+ 0.1µF CLK+ CLK– 09684-039 240Ω CLOCK INPUT 50kΩ 1kΩ 0.1µF A third option is to ac couple a differential LVDS signal to the sample clock input pins, as shown in Figure 46. The AD9510/ AD9511/AD9512/AD9513/AD9514/AD9515/AD9516 clock drivers offer excellent jitter performance. 0.1µF OPTIONAL 0.1µF 100Ω 0.1µF Figure 45. Differential PECL Sample Clock (Up to 625 MHz) CLOCK INPUT AD951x CMOS DRIVER ADC CLK– 50kΩ 50Ω1 1kΩ 09684-042 0.1µF CLOCK INPUT Jitter in the rising edge of the input is of paramount concern and is not easily reduced by the internal stabilization circuit. The duty cycle control loop does not function for clock rates at less than 40 MHz nominally. The loop has a time constant associated with it that must be considered in applications in which the clock rate can change dynamically. A wait time of 1.5 µs to 5 µs is required after a dynamic clock frequency increase or decrease before the DCS loop is relocked to the input signal. During the time period that the loop is not locked, the DCS loop is bypassed, and internal device timing is dependent on the duty cycle of the input clock signal. Rev. 0 | Page 22 of 36 Data Sheet AD6657A In the equation, the rms aperture jitter represents the clock input jitter specification. IF undersampling applications are particularly sensitive to jitter, as shown in Figure 49. 0.55 1.2 0.50 IAVDD 1.1 0.45 1.0 0.40 0.9 TOTAL POWER 0.8 0.30 0.7 0.6 0.25 0.5 0.20 0.4 0.3 IDRVDD 0.15 0.10 80 0.2 75 0.05 0.1 0 0 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 0.05ps SAMPLING FREQUENCY (MSPS) Figure 50. Power and Current vs. Sampling Frequency 70 SNR (dBc) 0.35 CURRENT (A) SNRHF = −10log[(2π × fIN × tJRMS)2 + 10(−SNRLF/10) ] 0.60 1.4 1.3 TOTAL POWER (W) High speed, high resolution ADCs are sensitive to the quality of the clock input. The degradation in SNR from the low frequency SNR (SNRLF) at a given input frequency (fIN) due to jitter (tJRMS) can be calculated by 1.5 09684-050 Jitter Considerations By asserting PDWN (either through the SPI port or by asserting the PDWN pin high), the AD6657A is placed in power-down mode. In this state, the ADC typically dissipates 4.5 mW. During power-down, the output drivers are placed in a high impedance state. Asserting the PDWN pin low returns the AD6657A to its normal operating mode. Note that PDWN is referenced to the digital output driver supply (DRVDD) and should not exceed that supply voltage. 0.20ps 65 60 0.50ps 55 1.00ps 1 10 100 INPUT FREQUENCY (MHz) 1k 09684-043 1.50ps 50 Figure 49. SNR vs. Input Frequency and Jitter In cases where aperture jitter may affect the dynamic range of the AD6657A, treat the clock input as an analog signal. Separate power supplies for clock drivers should be separated from the ADC output driver supplies to avoid modulating the clock signal with digital noise. Low jitter, crystal controlled oscillators make the best clock sources. If the clock is generated from another type of source (by gating, dividing, or another method), it should be retimed by the original clock at the last step. Refer to the AN-501 Application Note and AN-756 Application Note for more information about jitter performance as it relates to ADCs (available at www.analog.com). POWER DISSIPATION AND STANDBY MODE The power dissipated by the AD6657A is proportional to its clock rate (see Figure 50). The digital power dissipation does not vary significantly because it is determined primarily by the DRVDD supply and the bias current of the LVDS drivers. Reducing the capacitive load presented to the output drivers can minimize digital power consumption. The data in Figure 50 was obtained using the same operating conditions as those used in the Typical Performance Characteristics section, with a 5 pF load on each output driver. Low power dissipation in power-down mode is achieved by shutting down the reference, reference buffer, biasing networks, and clock. Internal capacitors are discharged when entering power-down mode and must be recharged when returning to normal operation. As a result, wake-up time is related to the time spent in power-down mode; shorter power-down cycles result in proportionally shorter wake-up times. When using the SPI port interface, the user can place the ADC in power-down mode or standby mode. Standby mode allows the user to keep the internal reference circuitry powered when faster wake-up times are required. See the Memory Map Register Descriptions section for more details. CHANNEL/CHIP SYNCHRONIZATION The AD6657A has a SYNC input that offers the user flexible synchronization options for synchronizing the clock divider. The clock divider sync feature is useful for guaranteeing synchronized sample clocks across multiple ADCs. The SYNC input is internally synchronized to the sample clock; however, to ensure that there is no timing uncertainty between multiple parts, externally synchronize the SYNC input signal to the input clock signal, meeting the setup and hold times shown in Table 5. Drive the SYNC input using a single-ended CMOS type signal. Rev. 0 | Page 23 of 36 AD6657A Data Sheet DIGITAL OUTPUTS The AD6657A output drivers are configured to interface with LVDS outputs using a DRVDD supply voltage of 1.8 V. The output bits are DDR LVDS as shown in Figure 2. Applications that require the ADC to drive large capacitive loads or large fanouts may require external buffers or latches. As described in the AN-877 Application Note, Interfacing to High Speed ADCs via SPI, the data format can be selected for offset binary or twos complement when using the SPI control. TIMING The AD6657A provides latched data with a latency of nine clock cycles. Data outputs are available one propagation delay (tPD) after the rising edge of the clock signal. Minimize the length of the output data lines and minimize the loads placed on them to reduce transients within the AD6657A because these transients can degrade converter dynamic performance. The lowest typical conversion rate of the AD6657A is 40 MSPS. At clock rates below 40 MSPS, dynamic performance can degrade. Data Clock Output (DCO) The AD6657A provides a data clock output (DCO) signal intended for capturing the data in an external register. The output data for Channel A and Channel C is valid when DCO is high; the output data for Channel B and Channel D is valid when DCO is low (see Figure 2). Table 11. Output Data Format Input (V) VIN+ − VIN− VIN+ − VIN− VIN+ − VIN− VIN+ − VIN− VIN+ − VIN− Condition (V) < −VREF − 0.5 LSB = −VREF =0 = +VREF − 1.0 LSB > +VREF − 0.5 LSB Offset Binary Output Mode 000 0000 0000 000 0000 0000 100 0000 0000 111 1111 1111 111 1111 1111 Rev. 0 | Page 24 of 36 Twos Complement Mode 100 0000 0000 100 0000 0000 000 0000 0000 011 1111 1111 011 1111 1111 Data Sheet AD6657A NOISE SHAPING REQUANTIZER The NSR feature can be independently controlled per channel via the SPI or via the MODE pin. Two different bandwidth modes are provided; the mode can be selected from the SPI port. In each of the two modes, the center frequency of the band can be tuned such that IFs can be placed anywhere in the Nyquist band. 0 –20 –40 –60 THIRD HARMONIC –80 –100 –120 22% BW MODE (>40 MHZ at 184.32 MSPS) –140 0 The first bandwidth mode offers excellent noise performance over 22% of the ADC sample rate (44% of the Nyquist band) and can be centered by setting the NSR mode bits in the NSR control register (Address 0x3C) to 000. In this mode, the useful frequency range can be set using the 6-bit tuning word in the NSR tuning word register (Address 0x3E). 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) Figure 51. 22% BW Mode, Tuning Word = 13 0 185MSPS 140.3MHz @ –1dBFS NSR 22% BW MODE, TW = 28 SNR = 73.4dB (75.0dBFS) SFDR = 91dBc –20 –40 AMPLITUDE (dBFS) There are 57 possible tuning words (TW); 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 + 0.11 × fADC –60 THIRD HARMONIC –80 –100 –140 0 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) 09684-052 –120 f1 = f0 + 0.22 × fADC Figure 52. 22% BW Mode, Tuning Word = 28 (fS/4 Tuning) 0 185MSPS 140.3MHz @ –1dBFS NSR 22% BW MODE, TW = 41 SNR = 73.4dB (75.0dBFS) SFDR = 91dBc –20 AMPLITUDE (dBFS) –40 –60 THIRD HARMONIC –80 –100 –120 –140 0 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) Figure 53. 22% BW Mode, Tuning Word = 41 Rev. 0 | Page 25 of 36 09684-053 f0 = fADC × .005 × TW 185MSPS 140.3MHz @ –1dBFS NSR 22% BW MODE, TW = 13 SNR = 73.4dB (75.0dBFS) SFDR = 91dBc 09684-051 When enabled, the NSR contributes an additional 0.6 dB of loss to the input signal, such that a 0 dBFS input is reduced to −0.6 dBFS at the output pins. Figure 51 to Figure 53 show the typical spectrum that can be expected from the AD6657A in the 22% BW mode for three different tuning words. AMPLITUDE (dBFS) The AD6657A features a noise shaping requantizer (NSR) to allow higher than an 11-bit SNR to be maintained in a subset of the Nyquist band. The harmonic performance of the receiver is unaffected by the NSR feature. AD6657A Data Sheet 33% BW MODE (>60 MHZ AT 184.32 MSPS) 0 –40 Figure 54 to Figure 56 show the typical spectrum that can be expected from the AD6657A in the 33% BW mode for three different tuning words. 185MSPS 140.3MHz @ –1dBFS NSR 33% BW MODE, TW = 5 SNR = 70.9dB (72.5dBFS) SFDR = 91dBc AMPLITUDE (dBFS) –40 –60 THIRD HARMONIC –80 –100 –140 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) 09684-154 –120 Figure 54. 33% BW Mode, Tuning Word = 5 0 185MSPS 140.3MHz @ –1dBFS NSR 33% BW MODE, TW = 17 SNR = 71.1dB (72.7dBFS) SFDR = 91dBc –20 –60 THIRD HARMONIC –80 –100 –120 –140 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) 09684-055 AMPLITUDE (dBFS) –40 0 –120 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) Figure 56. 33% BW Mode, Tuning Word = 17 f1 = f0 + 0.33 × fADC 0 –100 0 fCENTER = f0 + 0.165 × fADC –20 THIRD HARMONIC –80 –140 f0 = fADC × .005 × TW 0 –60 Figure 55. 33% BW Mode, Tuning Word = 17 (fS/4 Tuning) Rev. 0 | Page 26 of 36 09684-056 There are 34 possible tuning words (TW); 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. –20 AMPLITUDE (dBFS) The second bandwidth mode offers excellent noise performance over 33% of the ADC sample rate (66% of the Nyquist band) and can be centered by setting the NSR mode bits in the NSR control register (Address 0x3C) to 001. In this mode, the useful frequency range can be set using the 6-bit tuning word in the NSR tuning word register (Address 0x3E). 185MSPS 140.3MHz @ –1dBFS NSR 33% BW MODE, TW = 17 SNR = 70.9dB (72.5dBFS) SFDR = 91dBc Data Sheet AD6657A 36% BW MODE (>65 MHZ AT 184.32 MSPS) 0 –40 0 Figure 57 to Figure 59 show the typical spectrum that can be expected from the AD6657A in the 36% BW mode for three different tuning words. 0 185MSPS 140.3MHz @ –1dBFS NSR 36% BW MODE, TW = 0 SNR = 70.4dB (72.0dBFS) SFDR = 91dBc AMPLITUDE (dBFS) MODE PIN The MODE pin input allows convenient control of the NSR feature. A logic low enables NSR mode and a logic high sets the receiver to a straight 11-bit mode with NSR disabled. By default, the MODE pin is pulled high internally to disable the NSR. Each channel can be individually configured to ignore the MODE pin state by writing to Bit 4 of the NSR control register at Address 0x3C. Use of the NSR control register in conjunction with the MODE pin allows for very flexible control of the NSR feature on a per channel basis. –40 –60 THIRD HARMONIC –80 –100 –140 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) 09684-057 –120 Figure 57. 36% BW Mode, Tuning Word = 0 0 185MSPS 140.3MHz @ –1dBFS NSR 36% BW MODE, TW = 14 SNR = 70.4dB (72.0dBFS) SFDR = 91dBc –60 THIRD HARMONIC –80 –100 –120 –140 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) 09684-058 AMPLITUDE (dBFS) –40 0 9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50 FREQUENCY (MHz) Figure 59. 36% BW Mode, Tuning Word = 28 f1 = f0 + 0.36 × fADC –20 –100 –140 fCENTER = f0 + 0.18 × fADC 0 THIRD HARMONIC –80 –120 f0 = fADC × .005 × TW –20 –60 09684-059 There are 28 possible tuning words (TW); 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. –20 AMPLITUDE (dBFS) The third bandwidth mode offers excellent noise performance over 36% of the ADC sample rate (72% of the Nyquist band) and can be centered by setting the NSR mode bits in the NSR control register (Address 0x3C) to 010. In this mode, the useful frequency range can be set using the 6-bit tuning word in the NSR tuning register (Address 0x3E). 185MSPS 140.3MHz @ –1dBFS NSR 36% BW MODE, TW = 28 SNR = 70.4dB (72.0dBFS) SFDR = 91dBc Figure 58. 36% BW Mode, Tuning Word = 14 (fS/4 Tuning) Rev. 0 | Page 27 of 36 AD6657A Data Sheet BUILT-IN SELF TEST (BIST) AND OUTPUT TEST The AD6657A includes built-in test features designed to verify the integrity of each channel and to facilitate board-level debugging. A built-in self test (BIST) feature is included that verifies the integrity of the digital datapath of the AD6657A. Various output test options are also provided to place predictable values on the outputs of the AD6657A. BIST The BIST is a thorough test of the digital portion of the selected AD6657A signal path. When enabled, the test runs from an internal pseudorandom noise (PN) source through the digital datapath starting at the ADC block output. The BIST sequence runs for 512 cycles and stops. The BIST signature value for the selected channel is written to Register 0x24 and Register 0x25. If more than one channel is BIST enabled, the channel that is first according to alphabetical order is written to the BIST signature registers. For example, if Channel B and Channel C are BIST enabled, the results from Channel B are written to the BIST signature registers. The outputs are not disconnected during this test, so the PN sequence can be observed as it runs. The PN sequence can be continued from its last value or reset from the beginning, based on the value programmed in Register 0x0E, Bit 2. The BIST signature result varies based on the channel configuration. OUTPUT TEST MODES The output test options are shown in Table 13. When an output test mode is enabled, the analog section of the receiver 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. The seed value for the PN sequence tests can be forced if the PN reset bits are used to hold the generator in reset mode by setting Bit 4 or Bit 5 of Register 0x0D. These tests can be performed with or without an analog signal (if present, the analog signal is ignored), but they require an encode clock. For more information, see the AN-877 Application Note, Interfacing to High Speed ADCs via SPI. Rev. 0 | Page 28 of 36 Data Sheet AD6657A SERIAL PORT INTERFACE (SPI) During an instruction phase, a 16-bit instruction is transmitted. The first bit of the first byte in a serial data transfer frame indicates whether a read command or a write command is issued. Data follows the instruction phase, and its length is determined by the W0 and W1 bits. All data is composed of 8-bit words. The AD6657A serial port interface (SPI) allows the user to configure the receiver for specific functions or operations through a structured internal register space. The SPI provides 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 port. Memory is organized into bytes that can be further divided into fields, which are documented in the Memory Map section. For detailed operational information, see the AN-877 Application Note, Interfacing to High Speed ADCs via SPI. 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 read operation, the serial data input/output (SDIO) pin changes direction from an input to an output at the appropriate point in the serial frame. CONFIGURATION USING THE SPI Three pins define the SPI of the AD6657A: SCLK, SDIO, and CSB (see Table 12). SCLK (a serial clock) is used to synchronize the read and write data presented from and to the AD6657A. SDIO (serial data input/output) is a bidirectional pin that allows data to be sent to and read from the internal memory map registers. CSB (chip select bar) is an active low control that enables or disables the read and write cycles. Data can be sent in MSB first mode or in LSB first mode. MSB first is the default mode on power-up and can be changed via the SPI port configuration register. For more information about this and other features, see the AN-877 Application Note, Interfacing to High Speed ADCs via SPI. HARDWARE INTERFACE Table 12. Serial Port Interface Pins Pin SCLK The pins described in Table 12 constitute the physical interface between the user’s programming device and the serial port of the AD6657A. The SCLK pin and the CSB pin function as inputs when using the SPI interface. The SDIO pin is bidirectional, functioning as an input during the write phase and as an output during readback. Function Serial clock. Serial shift clock input. SCLK is used to synchronize serial interface reads and writes. Serial data input/output. Bidirectional pin that serves as an input or an output, depending on the instruction being sent and the relative position in the timing frame. Chip select bar (active low). This control gates the read and write cycles. SDIO CSB The SPI interface is flexible enough to be controlled by either FPGAs or microcontrollers. One method for SPI configuration is described in detail in Application Note AN-812, Microcontroller-Based Serial Port Interface (SPI) Boot Circuit. The falling edge of the CSB pin, in conjunction with the rising edge of the SCLK pin, determines the start of the framing. An example of the serial timing can be found in Figure 60 (for symbol definitions, see Table 5). The SPI port should not be active during periods when the full dynamic performance of the AD6657A 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 AD6657A performance. If the on-board SPI bus is used for other devices, it may be necessary to provide buffers between this bus and the AD6657A to prevent these signals from transitioning at the receiver inputs during critical sampling periods. CSB can be held low indefinitely, which permanently enables the device; this is called streaming. CSB can stall high between bytes to allow for additional external timing. When CSB is tied high, SPI functions are placed in high impedance mode. tH tCLK tHIGH tDS tDH tS tLOW CSB SCLK DON’T CARE DON’T CARE R/W W1 W0 A12 A11 A10 A9 A8 A7 D5 Figure 60. Serial Port Interface Timing Diagram Rev. 0 | Page 29 of 36 D4 D3 D2 D1 D0 DON’T CARE 09684-054 SDIO DON’T CARE AD6657A Data Sheet MEMORY MAP READING THE MEMORY MAP REGISTER TABLE Logic Levels Each row in the memory map register table has eight bit locations (see Table 13). The memory map is roughly divided into four sections: the chip configuration registers (Address 0x00 and Address 0x01); the channel index and transfer registers (Address 0x05 and Address 0xFF); the ADC function registers, including setup, control, and test (Address 0x08 to Address 0x25); and the digital feature control registers (Address 0x3A to Address 0x3E). An explanation of logic level terminology follows: The memory map register table (see Table 13) provides the default hexadecimal value for each hexadecimal address shown. The column with the heading (MSB) Bit 7 is the start of the default hexadecimal value given. The AN-877 Application Note, Interfacing to High Speed ADCs via SPI, documents the functions controlled by Register 0x00 to Register 0xFF. The remaining registers, Register 0x3A to Register 0x3E, are documented in the Memory Map Register Descriptions section. Open Locations All address and bit locations that are not included in Table 13 are not currently supported for this device. Unused bits of a valid address location should be written with 0s. Writing to these locations is required only when part of an address location is open (for example, Address 0x18). If the entire address location is open (for example, Address 0x13), this address location should not be written. Default Values After the AD6657A is reset, critical registers are loaded with default values. The default values for the registers are given in the memory map register table (see Table 13). “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.” Transfer Register Map Address 0x08 to Address 0x3E are shadowed. Writes to these addresses do not affect part operation until a transfer command is issued by writing 0x01 to Address 0xFF, thereby setting the transfer bit. This allows these registers to be updated internally and simultaneously when the transfer bit is set. The transfer bit is autoclearing. Channel Specific Registers Some channel setup functions, such as the NSR control function, can be programmed differently for each channel. In these cases, channel address locations are internally duplicated for each channel. These registers and bits are designated in Table 13 as local. Local registers and bits can be accessed by setting the appropriate channel bits in Register 0x05. If multiple channel bits are set, the subsequent write affects the registers of all selected channels. In a read cycle, select a single channel only to read one of the registers. If multiple channels are selected during a SPI read cycle, the device returns the value for Channel A only. Registers and bits designated as global in Table 13 affect the entire device or the channel features for which there are no independent per channel settings. The settings in Register 0x05 do not affect the global registers and bits. Rev. 0 | Page 30 of 36 Data Sheet AD6657A MEMORY MAP REGISTER TABLE All address and bit locations that are not included in Table 13 are not currently supported for this device. Table 13. Memory Map Registers Addr. Register (MSB) (Hex) Name Bit 7 Chip Configuration Registers 0x00 SPI port Open configuration (global) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 (LSB) Bit 0 LSB first Soft reset 1 1 Soft reset LSB first Open 0x01 0x18 Chip ID (global) Channel Index and Transfer Registers 0x05 Channel Enable index output port for Channel C and Channel D Enable output port for Channel A and Channel B Open Open Channel D enable Channel C enable Channel B enable Channel A enable 0xCF 0xFF Open Open Open Open Open Open Open SW transfer 1 = on 0 = off (default) 0x00 ADC Function Registers 0x08 Power modes Open Open Open 0x0B Clock divide (global) Open Open Open Open External powerdown pin function (global) 0 = full powerdown 1= standby Clock divide phase 000 = 0 input clock cycles delayed 001 = 1 input clock cycle delayed 010 = 2 input clock cycles delayed 0x0C Shuffle mode (local) Open Open Open Open Transfer 8-bit chip ID, Bits[7:0] AD6657A = 0x7B (default) Default Value (Hex) Open Open Rev. 0 | Page 31 of 36 0x7B Internal power-down mode (local) 00 = normal operation (default) 01 = full power-down 10 = standby Clock divide ratio 000 = divide by 1 001 = divide by 2 010 = divide by 3 011 = divide by 4 100 = divide by 5 101 = divide by 6 110 = divide by 7 111 = divide by 8 Shuffle mode enable 00 = shuffle disabled 01 = shuffle enabled 0x00 Comments Nibbles are mirrored so that LSB first or MSB first mode is set correctly, regardless of shift mode. To control this register, all channel index bits in Register 0x05 must be set. Read only. Bits are set to determine which channel on the chip receives the next write command; applies to local registers. Synchronously transfers data from the master shift register to the slave. Determines generic modes of chip operation. 0x00 0x01 Enables or disables shuffle mode. AD6657A Data Sheet Addr. (Hex) 0x0D Register Name Test mode (local) (MSB) Bit 7 Open Bit 6 Open Bit 5 Reset long PN generator 0 = on 1 = off (default) 0x0E BIST enable (local) Open Open Open 0x10 Offset adjust (local) Open Open 0x14 Output mode (local) Open Open Open 0x15 Output adjust (local) Open Open Open 0x16 Clock phase control (local) Open Open 0x17 DCO output delay (local) Invert DCO clock 0 = off 1 = on DCO delay enable 0 = off 1 = on Open Open 0x18 VREF select (global) Open Open Open Bit 4 Reset short PN generator 0 = on 1 = off (default) Bit 3 Open Bit 2 (LSB) Bit 0 Bit 1 Output test mode 000 = off (normal operation) 001 = midscale short 010 = positive FS 011 = negative FS 100 = alternating checkerboard 101 = PN sequence long 110 = PN sequence short 111 = 1/0 word toggle Open BIST Open Open BIST reset enable 0 = on 1 = on 1 = off 0 = off (default) (default) Offset adjustment in LSBs from +127 to −128 (twos complement format) 011111 = +31 LSB 011110 = +30 LSB 011101 = +29 LSB … 000010 = +2 LSB 000001 = +1 LSB 000000 = 0 LSB … 111111 = −1 LSB 111110 = −2 LSB 111101 = −3 LSB … 100001 = −31 LSB 100000 = −32 LSB Output format (local) Open Output Output 00 = offset binary invert enable 01 = twos (local) bar complement 1 = on (local) 0 = off 1 = off 0 = on Open Output port LVDS drive current 0000 = 3.72 mA 0001 = 3.5 mA (default) 0010 = 3.3 mA 0011 = 2.96 mA 0100 = 2.82 mA 0101 = 2.57 mA 0110 = 2.27 mA 0111 = 2.0 mA 1000 = 2.0 mA Open Open Open Open Open Output port DCO clock delay 00000 = 100 ps additional delay on the DCO pin 00001 = 200 ps additional delay on the DCO pin 00010 = 300 ps additional delay on the DCO pin … 11101 = 3.0 ns additional delay on the DCO pin 11110 = 3.1 ns additional delay on the DCO pin 11111 = 3.2 ns additional delay on the DCO pin Internal VREF full-scale adjustment Main reference full-scale VREF adjustment 01111: internal 2.087 V p-p … 00001: internal 1.772 V p-p 00000: internal 1.75 V p-p … 11111: internal 1.727 V p-p … 10000: internal 1.383 V p-p Rev. 0 | Page 32 of 36 Default Value (Hex) 0x00 0x00 0x00 Comments When set, the test data is placed on the output pins in place of normal data. When Bit 0 is set, the built-in self test function is initiated. Device offset trim. 0x00 Configures the outputs and the format of the data. 0x01 Output current adjustments. 0x00 When Bit 7 is set, clock polarity is reversed. Enable DCO delay and set the delay time. 0x00 0x00 Select adjustments for VREF. Data Sheet AD6657A Addr. (Hex) 0x24 Register (MSB) Name Bit 7 BIST signature LSB (local) 0x25 BIST signature MSB (local) Digital Feature Control Registers 0x3A Sync control Open (global) Bit 6 Bit 5 Bit 4 Bit 3 BIST Signature[7:0] Bit 2 Bit 1 Default Value (Hex) 0x00 Comments Read only. 0x00 Read only. Master sync enable 0 = off 1 = on 0x00 Control register to synchronize the clock divider. NSR enable 0 = off 1 = on (used only if Bit 4 = 1; otherwise ignored) 0x00 Noise shaping requantizer (NSR) controls. 0x1C NSR frequency tuning word. (LSB) Bit 0 BIST Signature[15:8] Open Open Open Open MODE pin disable 0= MODE pin used 1= MODE pin disabled 0x3C NSR control (local) Open Open 0x3E NSR tuning word (local) Open Open Open Clock Clock divider divider sync mode sync 0 = contienable nuous 0 = off 1 = next sync 1 = on mode, next rising edge of sync resets clock divider NSR mode 000 = 22% BW mode 001 = 33% BW mode 010 = 36% BW mode NSR tuning word See the Noise Shaping Requantizer section. Equations for the tuning word are dependent on the NSR mode. MEMORY MAP REGISTER DESCRIPTIONS For additional information about functions controlled in Register 0x00 to Register 0xFF, see the AN-877 Application Note, Interfacing to High Speed ADCs via SPI. NSR Control (Register 0x3C) Bits[7:5]—Reserved Bit 4—MODE Pin Disable Sync Control (Register 0x3A) Bits[7:3]—Reserved Bit 4 specifies whether the selected channels are to be controlled by the MODE pin. Local registers act on the channels that are selected by the channel index register (Address 0x05). Bit 2—Clock Divider Sync Mode Bits[3:1]—NSR Mode Bit 2 selects the mode of the clock divider sync function. When Bit 2 is low, continuous sync mode is enabled. When Bit 2 is high, the clock divider is reset on the next rising edge of the sync signal. Subsequent rising edges of the sync signal are ignored. Bits[3:1] determine the bandwidth (BW) mode of the NSR. When Bits[3:1] are set to 000, the NSR is configured for a 22% BW mode that provides enhanced SNR performance over 22% of the sample rate. When Bits[3:1] are set to 001, the NSR is configured for a 33% BW mode that provides enhanced SNR performance over 33% of the sample rate. When Bits[3:1] are set to 010, the NSR is configured for a 36% BW mode that provides enhanced SNR performance over 36% of the sample rate. Bit 1—Clock Divider Sync Enable Bit 1 gates the sync pulse to the clock divider. The sync signal is enabled when Bit 1 is high and Bit 0 is high. This is continuous sync mode. Bit 0—Master Sync Enable Bit 0 must be high to enable any of the sync functions. If the sync capability is not used, this bit should remain low to conserve power. Bit 0—NSR Enable The NSR is enabled when Bit 0 is high and disabled when Bit 0 is low. Bit 0 is ignored unless the MODE pin disable bit (Bit 4) is set. Rev. 0 | Page 33 of 36 AD6657A Data Sheet NSR Tuning Word (Register 0x3E) Bits[7:6]—Reserved Bits[5:0]—NSR Tuning Word The NSR tuning word sets the band edges of the NSR band. In 22% BW mode, there are 57 possible tuning words; in 33% BW mode, there are 34 possible tuning words; in 36% BW mode, there are 28 possible tuning words. For either mode, each step represents 0.5% of the ADC sample rate. For the equations used to calculate the tuning word based on the BW mode of operation, see the Noise Shaping Requantizer section. Rev. 0 | Page 34 of 36 Data Sheet AD6657A APPLICATIONS INFORMATION DESIGN GUIDELINES VCMx Pins Before starting the design and layout of the AD6657A in a system, it is recommended that the designer become familiar with these guidelines, which discuss the special circuit connections and layout requirements needed for certain pins. The VCMx pins are provided to set the common-mode level of the analog inputs. Decouple the VCMx pins to ground with a 0.1 μF capacitor, as shown in Figure 37. Power and Ground Recommendations The SPI port should not be active during periods when the full dynamic performance of the AD6657A 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 AD6657A performance. If the on-board SPI bus is used for other devices, it may be necessary to provide buffers between this bus and the AD6657A to prevent these signals from transitioning at the receiver inputs during critical sampling periods. When connecting power to the AD6657A, it is recommended that two separate 1.8 V supplies be used. Use one supply for analog (AVDD); use a separate supply for the digital outputs (DRVDD). The AVDD and DRVDD supplies should be isolated with separate decoupling capacitors. Several different decoupling capacitors can be used to cover both high and low frequencies. Locate these capacitors close to the point of entry at the PCB level and close to the pins of the part, with minimal trace length. SPI Port A single PCB ground plane is sufficient when using the AD6657A. With proper decoupling and smart partitioning of the PCB analog, digital, and clock sections, optimum performance is easily achieved. Rev. 0 | Page 35 of 36 AD6657A Data Sheet PACKAGING AND ORDERING INFORMATION OUTLINE DIMENSIONS A1 BALL CORNER 10.10 10.00 SQ 9.90 A1 BALL CORNER 12 11 10 9 8 7 6 5 4 3 2 1 A B C D 8.80 BSC SQ E F G H 0.80 J K L M 0.60 REF TOP VIEW BOTTOM VIEW DETAIL A *1.40 MAX DETAIL A 0.65 MIN 0.25 MIN 0.50 COPLANARITY 0.45 0.20 0.40 BALL DIAMETER 10-21-2010-B SEATING PLANE *COMPLIANT WITH JEDEC STANDARDS MO-275-EEAB-1 WITH EXCEPTION TO PACKAGE HEIGHT. Figure 61. 144-Ball Chip Scale Package Ball Grid Array [CSP_BGA] (BC-144-1) Dimensions shown in millimeters ORDERING GUIDE Model 1 AD6657ABBCZ AD6657ABBCZRL AD6657AEBZ 1 Temperature Range −40°C to +85°C −40°C to +85°C Package Description 144-Ball Chip Scale Package Ball Grid Array [CSP_BGA] 144-Ball Chip Scale Package Ball Grid Array [CSP_BGA] Evaluation Board Package Option BC-144-1 BC-144-1 Z = RoHS Compliant Part. ©2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D09684-0-10/11(0) www.analog.com/AD6657A Rev. 0 | Page 36 of 36