ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 Dual Channel 11-Bits, 125 MSPS ADC With Parallel CMOS/DDR LVDS Outputs FEATURES 1 • • • • • • • • • Maximum Sample Rate: 125 MSPS 11-Bit Resolution With No Missing Codes 82 dBc SFDR at Fin = 117 MHz 67 dBFS SNR at Fin = 117 MHz 77.5 dBFS SNR at Fin = 117 MHz, 20MHz bandwidth using SNRBoost technology 92 dB Crosstalk Parallel CMOS and DDR LVDS Output Options 3.5 dB Coarse Gain and Programmable Fine Gain up to 6 dB for SNR/SFDR Trade-Off Digital Processing Block With: – Offset Correction – Fine Gain Correction, in Steps of 0.05 dB – Decimation by 2/4/8 – Built-in and Custom Programmable 24-Tap Low/High /Band Pass Filters • • • • Supports Sine, LVPECL, LVDS and LVCMOS Clocks and Amplitude Down to 400 mVPP Clock Duty Cycle Stabilizer Internal Reference; Also Supports External Reference 64-QFN Package (9mm × 9mm) APPLICATIONS • • • • • • • Wireless Communications Infrastructure Software Defined Radio Power Amplifier Linearization 802.16d/e Medical Imaging Radar Systems Test and Measurement Instrumentation DESCRIPTION ADS62C15 is a dual channel 11-bit A/D converter with maximum sample rates up to 125 MSPS. It combines high performance and low power consumption in a compact 64 QFN package. Using an internal sample and hold and low jitter clock buffer, the ADC supports high SNR and high SFDR at high input frequencies. It has coarse and fine gain options that can be used to improve SFDR performance at lower full-scale input ranges. ADS62C15 uses proprietary SNRBoost technology that can be used to overcome SNR limitation due to quantization noise (for bandwidths less than Nyquist, Fs/2). It includes a digital processing block that consists of several useful and commonly used digital functions such as ADC offset correction, fine gain correction (in steps of 0.05 dB), decimation by 2,4,8 and in-built and custom programmable filters. By default, the digital processing block is bypassed, and its functions are disabled. Two output interface options exist – parallel CMOS and DDR LVDS (Double Data Rate). ADS62C15 includes internal references while traditional reference pins and associated decoupling capacitors have been eliminated. The device can also be driven with an external reference. The device is specified over the industrial temperature range (–40°C to 85°C). 1 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 2008, Texas Instruments Incorporated ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. DRGND DRVDD AGND AVDD FUNCTIONAL BLOCK DIAGRAM Digital Processing Block Channel A INA_P SHA INA_M OUTPUT BUFFERS SNRBoost 11 bit CLKP CLKM 11 bit SHA CHANNEL A OUTPUT CLOCK BUFFER CLOCKGEN INB_P INB_M 14 bit 14 BIT ADC ADAC 14 bit 14 BIT ADC ADAC OUTPUT BUFFERS SNRBoost CHANNEL B Digital Processing Block Channel B VCM REFERENCE CONTROL INTERFACE DA0 DA1 DA2 DA3 DA4 DA5 DA6 DA7 DA8 DA9 DA10 CLKOUT DB0 DB1 DB2 DB3 DB4 DB5 DB6 DB7 DB8 DB9 DB10 CMOS INTERFACE 2 CTRL1 CTRL2 CTRL3 RESET SCLK SEN SDAATA SDOUT Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 CLIPPER 14 bits To output buffers LVDS or CMOS From ADC output Fine Gain (0 to 6 dB 0.5 dB steps) 24 TAP FILTER Gain Correction (0.05 dB steps) - LOW PASS - HIGH PASS - BAND PASS DECIMATION BY 2/4/8 11 bits 11 bits Filter Select 0 OFFSET ESTIMATION BLOCK 11 bits Disable offset correction Freeze offset correction OFFSET CORRECTION Bypass filter SNRBoost GAIN CORRECTION FINE GAIN DIGITAL FILTER & DECIMATION DIGITAL PROCESSING BLOCK Figure 1. Digital Processing Block Diagram PACKAGE/ORDERING INFORMATION (1) PRODUCT ADS62C15 (1) (2) PACKAGELEAD QFN-64 PACKAGE DESIGNATOR RGC SPECIFIED TEMPERATURE RANGE –40°C to 85°C LEAD/BALL FINISH Cu NiPdAu PACKAGE MARKING AZ62C15 ORDERING (2) NUMBER TRANSPORT MEDIA, QUANTITY ADS62C15IRGCT Tape and reel, 250 ADS62C15IRGCR Tape and reel, 2000 For thermal pad size on the package, see the mechanical drawings at the end of this data sheet. θJA = 23.17 °C/W (0 LFM airflow), θJC = 22.1 °C/W when used with 2 oz. copper trace and pad soldered directly to a JEDEC standard four layer 3 in. x 3 in. PCB. For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI website at www.ti.com. ABSOLUTE MAXIMUM RATINGS (1) VALUE UNIT –0.3 V to 3.9 V –0.3 V to 3.9 V Voltage between AGND and DRGND –0.3 to 0.3 V Voltage between AVDD to DRVDD –0.3 to 3.3 V –0.3 to 2 V –0.3 V to minimum ( 3.6, AVDD + 0.3 V ) V –0.3 V to AVDD + 0.3 V V Supply voltage range, AVDD, DRVDD VSS Voltage applied to external pin, CM (in external reference mode) Voltage applied to analog input pins, INA_P, INA_M, INB_P, INB_M Voltage applied to clock input pins, CLKP, CLKM TA Operating free-air temperature range –40 to 85 °C TJ Operating junction temperature range 125 °C Tstg Storage temperature range –65 to 150 °C (1) Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or any other conditions beyond those indicated under recommended operating conditions is not implied. Exposure to absolute maximum rated conditions for extended periods may affect device reliability. Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 3 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com RECOMMENDED OPERATING CONDITIONS over operating free-air temperature range (unless otherwise noted) MIN NOM MAX 3 3.3 3.6 CMOS interface 1.65 1.8 to 3.3 3.6 LVDS interface 3.0 3.3 3.6 UNIT SUPPLIES Analog supply voltage, AVDD VSS Digital supply voltage, DRVDD V V ANALOG INPUTS Differential input voltage range 2 VPP Input common-mode voltage 1.5 ± 0.1 V Voltage applied on CM in external reference mode 1.5 ±0.05 V CLOCK INPUT Fs Input clock sample rate 1 Sine wave, ac-coupled Input clock amplitude differential (VCLKP–VCLKM) 0.4 125 LVPECL, ac-coupled 1.6 LVDS, ac-coupled 0.7 LVCMOS, single-ended, ac-coupled Input clock duty cycle VPP 3.3 35% MSPS 3 50% V 65% DIGITAL OUTPUTS Output buffer drive strength (1) CLOAD Maximum external load capacitance from each output pin to DRGND For CLOAD ≤ 5 pF and DRVDD ≥ 2.2 V Default strength For CLOAD ≥ 5 pF and DRVDD ≥ 2.2 V Maximum strength For DRVDD < 2.2 V Maximum strength CMOS interface Differential load resistance between the LVDS output pairs (LVDS mode) TA Operating free-air temperature 4 5 LVDS interface, with 100 Ω internal termination RLOAD (1) 5 LVDS interface, without internal termination pF 10 Ω 100 –40 85 °C See the Output buffer strength programmability in application section Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 ELECTRICAL CHARACTERISTICS Typical values at 25°C, min and max values are across the full temperature range TMIN = –40°C to TMAX = 85°C, AVDD = 3.3 V, DRVDD = 1.8 V to 3.3 V, sampling frequency = 125 MSPS, 50% clock duty cycle, –1 dBFS differential analog input, internal reference mode, SNRBoost disabled, applies to CMOS and LVDS interfaces (unless otherwise noted). PARAMETER TEST CONDITIONS MIN TYP MAX Resolution UNIT 11 bits ANALOG INPUTS Differential input voltage range 2 VPP MΩ Differential input resistance (at dc) See Figure 32 >1 Differential input capacitance See Figure 33 7 pF Analog input bandwidth 450 MHz Analog input common mode current (per input pin) 125 µA VCM common mode voltage output 1.5 VCM output current capability V 4 mA POWER SUPPLY Analog supply current (AVDD) ISS Output buffer supply current (DRVDD) CMOS interface 216 DRVDD = 1.8 V, 2.5 MHz input signal no load capacitance (1) mA 17 Total power – CMOS interface 0.74 Total power – CMOS interface DRVDD = 3.3 V, 50 MHz input signal 10 pF load capacitance Total power – LVDS interface DRVDD = 3.3 V W 1.22 5 W 0.94 Global power down 30 W 60 mW DC ACCURACY No missing codes Specif ied DNL Differential Non-Linearity –0.8 ±0.4 0.8 LSB INL Integral Non-Linearity –3.5 ±1 3.5 LSB EO Offset Error –10 ±3 10 Offset error temperature coefficient 0.05 mV mV/°C There are two sources of gain error – internal reference inaccuracy and channel gain error EGREF Gain error due to internal reference inaccuracy alone EGCHAN Gain error of channel alone –1 (2) –1 Channel gain error temperature coefficient (1) (2) ±0.25 1 ±0.3 1 0.005 %FS %FS Δ%/°C In CMOS mode, the DRVDD current scales with the sampling frequency and the load capacitance on output pins (see Figure 29). This is specified by design and characterization; it is not tested in production. Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 5 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com ELECTRICAL CHARACTERISTICS (continued) Typical values at 25°C, min and max values are across the full temperature range TMIN = –40°C to TMAX = 85°C, AVDD = 3.3 V, DRVDD = 1.8 V to 3.3 V, sampling frequency = 125 MSPS, 50% clock duty cycle, –1 dBFS differential analog input, internal reference mode, SNRBoost disabled, applies to CMOS and LVDS interfaces (unless otherwise noted). PARAMETER TEST CONDITIONS MIN Fin= 10 MHz Signal to noise ratio Fin= 170 MHz Fin = 230 MHz 65.5 66.8 3.5 dB gain 66.4 0 dB gain 66.6 3.5 dB gain 66.2 Fin= 170 MHz Fin = 230 MHz ENOB Effective number of bits 65 66.5 3.5 dB gain 66.2 0 dB gain 66.3 3.5 dB gain Fin = 50 MHz Fin= 170 MHz Fin = 230 MHz Fin= 170 MHz Fin = 230 MHz 82 3.5 dB gain 84 0 dB gain 78 3.5 dB gain 80 Fin= 170 MHz Fin = 230 MHz 79 3.5 dB gain 81 0 dB gain 75 3.5 dB gain 77 75 Fin= 170 MHz Fin = 230 MHz Worst Spur IMD 6 93 0 dB gain 85 3.5 dB gain 87 0 dB gain 82 3.5 dB gain 84 dBc 89 Fin = 50 MHz Third harmonic distortion dBc 95 Fin= 10 MHz HD3 77 0 dB gain Fin = 50 MHz Second harmonic distortion dBc 87 72 Fin= 10 MHz HD2 LSB 79 0 dB gain Fin = 50 MHz Total harmonic distortion 10.8 89 75 Fin= 10 MHz THD dBFS 65.9 10.5 Fin = 50 MHz Spurious free dynamic range 66.9 0 dB gain Fin= 10 MHz SFDR dBFS 67.1 Fin = 50 MHz Signal to noise and distortion ratio 67.1 0 dB gain Fin= 10 MHz SINAD UNIT 67.2 Fin = 50 MHz SNR TYP MAX 75 79 0 dB gain 82 3.5 dB gain 84 0 dB gain 78 3.5 dB gain 80 dBc Fin= 10 MHz 94 Fin = 50 MHz 92 Fin= 170 MHz 90 Fin = 230 MHz 88 2-Tone intermodulation distortion F1 = 185 MHz, F2 = 190 MHz each tone at –7 dBFS 88 dBFS Input overload recovery Recovery to within 1% (of final value) for 6-dB overload with sine wave input 1 clock cycles Other than second, third harmonics Submit Documentation Feedback dBc Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 ELECTRICAL CHARACTERISTICS (continued) Typical values at 25°C, min and max values are across the full temperature range TMIN = –40°C to TMAX = 85°C, AVDD = 3.3 V, DRVDD = 1.8 V to 3.3 V, sampling frequency = 125 MSPS, 50% clock duty cycle, –1 dBFS differential analog input, internal reference mode, SNRBoost disabled, applies to CMOS and LVDS interfaces (unless otherwise noted). PARAMETER PSRR TEST CONDITIONS MIN TYP MAX Cross-talk signal frequency up to 100 MHz 95 dB AC Power supply rejection ratio For 100 mVPP signal on AVDD supply, frequency up to 10 MHz 45 dBc Table 1. SNR Improvement with SNRBoost Sampling Frequency at 125 MSPS INPUT FREQUENCY MHz (1) (2) SNR, SIGNAL TO NOISE RATIO (TYP) dBFS BANDWIDTH MHz 117 (1) (2) UNIT Cross-talk SNRBoost disabled, dB SNRBoost enabled, dB MIN TYP MIN TYP 5 77 78.1 81 85.1 10 74 75.1 78 82 15 72 73.3 76 79.6 20 71 72.1 74.5 77.5 The min SNR value with SNRBoost enabled is specified by design and characterization; it is not tested in production. This table shows the SNR improvement over some selected bandwidths. With SNRBoost, SNR improvement can be achieved for any bandwidth less than (Sampling frequency/2). As the bandwidths increase, the amount of improvement reduces. DIGITAL CHARACTERISTICS The DC specifications refer to the condition where the digital outputs are not switching, but are permanently at a valid logic level 0 or 1. AVDD = 3.3 V, DRVDD = 1.8 V to 3.3 V, unless otherwise specified. PARAMETER TEST CONDITIONS MIN TYP MAX UNIT DIGITAL INPUTS High-level input voltage 2.4 V Low-level input voltage 0.8 V High-level input current 33 µA Low-level input current –33 µA 4 Pf High-level output voltage DRVDD V Low-level output voltage 0 V Output capacitance (internal to device) 2 pF High-level output voltage 1375 mV Low-level output voltage 1025 Input capacitance DIGITAL OUTPUTS – CMOS MODE, DRVDD = 1.8 to 3.3 V DIGITAL OUTPUTS – LVDS MODE (1) (2) , DRVDD = 3.3 V |VOD| Output differential voltage VOS Output offset voltage Common-mode voltage of OUTP and OUTM Output Capacitance Output capacitance inside the device, from either output to ground (1) (2) 250 350 mV 500 mV 1200 mV 2 pF LVDS buffer current setting, IO = 3.5 mA. External differential load resistance between the LVDS output pairs, RLOAD = 100 Ω. Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 7 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com TIMING REQUIREMENTS – LVDS AND CMOS MODES (1) Typical values are at 25°C, min and max values are across the full temperature range TMIN = –40°C to TMAX = 85°C, AVDD = 3.3 V, DRVDD = 1.8 V to 3.3 V, sampling frequency = 125 MSPS, sine wave input clock, 3 VPP clock amplitude, CLOAD = 5 pF (2) , Io = 3.5 mA, RLOAD = 100 Ω (3), no internal termination, unless otherwise noted. PARAMETER TEST CONDITIONS ta Aperture delay tj Aperture jitter MIN TYP MAX 0.8 1.8 2.8 130 from global power down Wake-up time to valid output data Latency from channel standby from output buffer disable UNIT ns fs rms 15 50 µs 100 200 ns CMOS 100 200 ns LVDS 200 500 ns default, after reset 14 clock cycles in low latency mode 10 clock cycles with decimation filter enabled 15 clock cycles 0.6 1.5 ns ns DDR LVDS MODE (4) DRVDD = 3.3 V Data setup time (5) tsu (5) Data valid (6) to zero-crossing of CLKOUTP (6) th Data hold time Zero-crossing of CLKOUTP to data becoming invalid 1.0 2.3 tPDI Clock propagation delay Input clock rising edge cross-over to output clock rising edge cross-over 20 MSPS ≤ Sampling frequency ≤ 125 MSPS 3.5 5.5 7.5 LVDS bit clock duty cycle Duty cycle of differential clock, (CLKOUTP-CLKOUTM) 10 MSPS ≤ Sampling frequency ≤ 125 MSPS 46% 49% 52% tRISE Data rise time Rise time measured from –100 mV to 100 mV 1 MSPS ≤ Sampling frequency ≤ 125 MSPS 70 110 170 ps tFALL Data fall time Fall time measured from 100 mV to –100 mV 1 MSPS ≤ Sampling frequency ≤ 125 MSPS 70 110 170 ps tCLKRISE Output clock rise time Rise time measured from –100 mV to 100 mV 1 MSPS ≤ Sampling frequency ≤ 125 MSPS 70 110 170 ps tCLKFALL Output clock fall time Fall time measured from 100 mV to –100 mV 1 MSPS ≤ Sampling frequency ≤ 125 MSPS 70 110 170 ps Data valid (7) to 50% of CLKOUT rising edge 2.0 3.5 ns 50% of CLKOUT rising edge to data becoming invalid (7) 2.0 3.5 ns 5.8 7.3 8.8 45% 53% 60% ns PARALLEL CMOS MODE DRVDD = 2.5 V to 3.3 V Data setup time (5) tsu (5) th Data hold time tPDI Clock propagation delay 50% of input clock rising edge to 50% of CLKOUT rising edge 20 MSPS ≤ Sampling frequency ≤ 125 MSPS Output clock duty cycle Duty cycle of output clock, CLKOUT 10 MSPS ≤ Sampling frequency ≤ 125 MSPS tRISE Data rise time Rise time measured from 20% to 80% of DRVDD 1 MSPS ≤ Sampling frequency ≤ 125 MSPS 0.7 1.5 2.5 ns tFALL Data fall time Fall time measured from 80% to 20% of DRVDD 1 MSPS ≤ Sampling frequency ≤ 125 MSPS 0.7 1.5 2.5 ns tCLKRISE Output clock rise time Rise time measured from 20% to 80% of DRVDD 1 MSPS ≤ Sampling frequency ≤ 125 MSPS 0.7 1.5 2.5 ns tCLKFALL Output clock fall time Fall time measured from 80% to 20% of DRVDD 1 MSPS ≤ Sampling frequency ≤ 125 MSPS 0.7 1.5 2.5 ns (1) (2) (3) (4) (5) (6) (7) 8 ns Timing parameters are ensured by design and characterization and not tested in production. CLOAD is the effective external single-ended load capacitance between each output pin and ground IO refers to the LVDS buffer current setting; RLOAD is the differential load resistance between the LVDS output pair. Measurements are done with a transmission line of 100Ω characteristic impedance between the device and the load. Setup and hold time specifications take into account the effect of jitter on the output data and clock. Data valid refers to LOGIC HIGH of 100 mV and LOGIC LOW of –100 mV. Data valid refers to LOGIC HIGH of 2 V (1.7 V) and LOGIC LOW of 0.8 V (0.7 V) for DRVDD = 3.3 V (2.5 V) Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 Table 2. Timing Characteristics at Lower Sampling Frequencies tsu DATA SETUP TIME, ns Sampling Frequency, MSPS MIN TYP th DATA HOLD TIME, ns MAX MIN TYP MAX CMOS INTERFACE, DRVDD = 2.5 TO 3.3 V 105 2.8 4.3 2.7 4.2 80 4.3 5.8 4.2 5.7 65 5.7 7.2 5.6 7.1 40 10.5 12 10.3 11.8 20 23 24.5 23 24.5 105 1 2.3 80 2.4 3.8 65 3.8 5.2 1.0 2.3 40 8.5 10 20 21 22.5 DDR LVDS INTERFACE, DRVDD = 3.3 V N+4 N+3 N+2 N+1 Sample N N+16 N+15 N+14 Input Signal ta Input Clock CLKP CLKM CLKOUTM CLKOUTP tsu 14 Clock Cycles DDR LVDS Output Data DXP, DXM E E – Even Bits D0,D2,D4,D6,D8,D10 O – Odd Bits D1,D3,D5,D7,D9 O E N–14 O E N–13 O E N–12 O (1) E N–11 tPDI th O E N–10 E O E O N N–1 E O N+1 E O O N+2 tPDI CLKOUT tsu Parallel CMOS 14 Clock Cycles* Output Data D0–D10 N–14 N–13 N–12 N–11 th N–10 N–1 N N+1 N+2 T0105-05 *Latency is 15 clocks when SNRBoost is enabled Figure 2. Latency Diagram Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 9 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com CLKM Input Clock clock CLKP t PDI CLKOUTM Output Clock clock CLKOUTP t su su Output Output Data data Pair pair Dn_Dn+1_P, Dn_Dn+1_M t hh t su su Dn * t hh Dn +1* *Dn - Bits D1, D3, D5, D7, D9 *Dn+1 - Bits D0, D2, D4, D6, D8, D10 Figure 3. LVDS Mode Timing CLKM Input Clock clock CLKP t PDI PDI Output Clock clock CLKOUT t su su Output Data data Dn t hh Dn * *Dn - Bits D0 to D10 Figure 4. CMOS Mode Timing 10 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 DEVICE CONFIGURATION ADS62C15 can be configured independently using either parallel interface control or serial interface programming. USING PARALLEL INTERFACE CONTROL ONLY To control the device using the parallel interface, keep RESET tied to high (AVDD). Pins SEN, SCLK, CTRL1, CTRL2 and CTRL3 can be used to directly control certain modes of the ADC. After power-up, the device will automatically get configured as per the parallel pin voltage settings (Table 4 to Table 6). In this mode, SEN and SCLK function as parallel analog control pins, which can be configured using a simple resistor divider (Figure 5). Table 3 has a brief description of the modes controlled by the parallel pins. Table 3. Parallel Pin Definition PIN SCLK SEN CTRL1 CTRL2 CTRL3 TYPE OF PIN CONTROLS MODES Analog control pins (controlled by analog voltage levels, see ) Coarse Gain and Internal/External reference Digital control pins (controlled by digital logic levels) LVDS/CMOS interface and Output Data Format Together control various power down modes and MUX mode. USING SERIAL INTERFACE PROGRAMMING ONLY To program the device using the serial interface, keep RESET low. Pins SEN, SDATA, and SCLK function as serial interface digital pins and are used to access the internal registers of ADC. The registers must first be reset to their default values either by applying a pulse on RESET pin or by setting bit <RST> = 1. After reset, the RESET pin must be kept low. The serial interface section describes the register programming and register reset in more detail. Since the parallel pins (CTRL1, CTRL2, CTRL3) are not used in this mode, they must be tied to ground. USING BOTH SERIAL INTERFACE and PARALLEL CONTROLS For increased flexibility, a combination of serial interface registers and parallel pin controls (CTRL1 to CTRL3) can also be used to configure the device. To allow this, keep RESET low. The parallel interface control pins CTRL1 to CTRL3 are available. After power-up, the device will automatically get configured as per the voltage settings on these pins (Table 6). SEN, SDATA, and SCLK function as serial interface digital pins and are used to access the internal registers of ADC. The registers must first be reset to their default values either by applying a pulse on RESET pin or by setting bit <RST> = 1. After reset, the RESET pin must be kept low. The serial interface section describes the register programming and register reset in more detail. Since the power down modes can be controlled using both the parallel pins and serial registers, the priority between the two is determined by <OVRD> bit. When <OVRD> bit = 0, pins CTRL1 to CTRL3 control the power down modes. With <OVRD> = 1, register bits <POWER DOWN> control these modes, over-riding the pin settings. Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 11 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com DETAILS OF PARALLEL CONFIGURATION ONLY The functions controlled by each parallel pin are described below. A simple way of configuring the parallel pins is shown in Figure 5. Table 4. SCLK (Analog Control Pin) SCLK DESCRIPTION 0 0 dB gain and Internal reference (3/8)AVDD 0 dB gain and External reference (5/8)2AVDD 3.5 dB Coarse gain and External reference AVDD 3.5 dB Coarse gain and Internal reference Table 5. SEN (Analog Control Pin) SEN DESCRIPTION 0 2s complement format and DDR LVDS output (3/8)AVDD Straight binary and DDR LVDS output (5/8)AVDD Straight binary and parallel CMOS output AVDD 2s complement format and parallel CMOS output Table 6. CTRL1, CTRL2 and CTRL3 (Digital Control Pins) CTRL1 CTRL2 CTRL3 LOW LOW LOW Normal operation DESCRIPTION LOW LOW HIGH Channel A output buffer disabled LOW HIGH LOW Channel B output buffer disabled LOW HIGH HIGH Channel A and B output buffer disabled HIGH LOW LOW Channel A and B powered down HIGH LOW HIGH Channel A standby HIGH HIGH LOW Channel B standby HIGH HIGH HIGH MUX mode of operation (only with CMOS interface Channel A and B data is multiplexed and output on DB10 to DB0 pins. See Multiplexed output mode for detailed description. AVDD (5 /8 )AVDD 3R ( 5 /8 ) AVDD AVDD GND 2R ( 3 /8 )AVDD ( 3 /8 )AVDD 3R To parallel pin GND Figure 5. Simple Scheme to Configure Parallel Pins 12 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 SERIAL INTERFACE The ADC has a set of internal registers, which can be accessed by the serial interface formed by pins SEN (Serial interface Enable), SCLK (Serial Interface Clock) and SDATA (Serial Interface Data). Serial shift of bits into the device is enabled when SEN is low. Serial data SDATA is latched at every falling edge of SCLK when SEN is active (low). The serial data is loaded into the register at every 16th SCLK falling edge when SEN is low. If the word length exceeds a multiple of 16 bits, the excess bits are ignored. Data can be loaded in multiple of 16-bit words within a single active SEN pulse. The first 8 bits form the register address and the remaining 8 bits the register data. The interface can work with SCLK frequency from 20 MHz down to low speeds (few Hertz), and also with a non-50% SCLK duty cycle. Register Initialization After power-up, the internal registers must be initialized to their default values. This is done in one of two ways: 1. Either through hardware reset by applying a high-going pulse on the RESET pin (of width greater than 10 ns) as shown in Figure 6. OR 2. By applying software reset. Using the serial interface, set the <RST> bit to high. This initializes internal registers to their default values, and then self-resets the <RST> bit to low. In this case, the RESET pin is kept low. REGISTER DATA REGISTER ADDRESS SDATA A7 A6 A5 A4 A3 A2 A1 A0 D7 D6 tSCLK D5 D4 D3 D2 D1 D0 tDH tDSU SCLK tSLOADS tSLOADH SEN RESET Figure 6. Serial Interface Timing SERIAL INTERFACE TIMING CHARACTERISTICS Typical values at 25°C, min and max values across the full temperature range TMIN = –40°C to TMAX = 85°C, AVDD = 3.3 V, DRVDD = 1.8 V to 3.3 V, unless otherwise noted. PARAMETER MIN > DC TYP MAX UNIT 20 MHz fSCLK SCLK frequency tSLOADS SEN to SCLK setup time 25 ns tSLOADH SCLK to SEN hold time 25 ns tDS SDATA setup time 25 ns tDH SDATA hold time 25 ns Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 13 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com Serial Register Readout (Only When CMOS Interface is Used) The device includes an option where the contents of the internal registers can be read back. This may be useful as a diagnostic check to verify the serial interface communication between the external controller and the ADC. a. First, set register bit <SERIAL READOUT> = 1. This also disables any further writes into the registers. b. Initiate a serial interface cycle specifying the address of the register (A7-A0) whose content must be read. c. The device outputs the contents (D7-D0) of the selected register on the SDOUT pin. d. The external controller can latch the contents at the falling edge of SCLK. e. To enable register writes, reset register bit <SERIAL READOUT> =0. The serial register readout works only with CMOS interface; with LVDS interface, pin 56 functions as CLKOUTM. A) Enable serial read back (<SERIAL READOUT> = 1) (Serial register writes are disabled) REGISTER DATA (D7:D0) = 0x01 REGISTER ADDRESS (A7:A0) = 0x00 SDATA 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 SCLK SEN SDOUT Pin SDOUT is tri-stated (<SERIAL READOUT> = 0) B) Read contents of register 0x14. This register has been initialized with 0xB0 (over-ride bit set, LVDS interface, 3.5dB coarse gain, internal reference, normal operation) REGISTER DATA (D7:D0) = XX (don’t care) REGISTER ADDRESS (A7:A0) = 0x14 SDATA A7 A6 A5 A4 A3 A2 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0 1 0 1 1 0 0 0 0 SCLK SEN SDOUT Pin SDOUT functions as serial readout (<SERIAL READOUT> = 1) Figure 7. Serial Readout 14 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 RESET TIMING Typical values at 25°C, min and max values across the full temperature range TMIN = –40°C to TMAX = 85°C, unless otherwise noted. PARAMETER CONDITIONS t1 Power-on delay Delay from power-up of AVDD and DRVDD to RESET pulse active t2 Reset pulse width t3 tPO MIN TYP MAX UNIT 5 ms Pulse width of active RESET signal 10 ns Register write delay Delay from RESET disable to SEN active 25 Power-up time Delay from power-up of AVDD and DRVDD to output stable ns 7 ms NOTE: : A high-going pulse on RESET pin is required in serial interface mode in case of initialization through hardware reset. For parallel interface operation, RESET has to be tied permanently HIGH. Figure 8. Reset Timing Diagram Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 15 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com SERIAL REGISTER MAP Table 7. Summary of Functions Supported by Serial Interface REGISTER ADDRESS REGISTER FUNCTIONS A7–A0 IN HEX D7 D6 D5 D4 D3 D2 00 0 0 0 0 0 0 0 0 0 0 <CLKOUT STRENGTH> 10 <CURRENT DOUBLE> LVDS buffer current double D0 <SERIAL <RST> READOUT Software Reset > 0 <LVDS CURRENT> LVDS buffer current programmability 0 0 0 12 0 0 13 0 0 0 <OFFSET FREEZE> 0 14 <OVRD> Over-ride bit 0 <OUTPUT INTERFACE> LVDS or CMOS interface <COARSE GAIN> 3.5 dB gain <REF> Internal/External reference <POWER DOWN MODES> 16 0 0 0 <DATA FORMAT> 2s complement or straight binary Bit/Byte wise (LVDS only) <TEST PATTERNS> 17 0 0 0 0 19 0 1A <LOW LATENCY> 1B <OFFSET EN> Other correction enable 0 0 0 0 0 0 0 <CUSTOM HIGH> Upper 6 bits <FILTER COEFF SELECT> In-built or custom coefficients <DECIMATION Enable> Enable decimation <GAIN CORRECTION> 0 to 0.5 dB, steps of 0.05 dB 0 1E to 2F 0 <DECIMATION RATE> Decimate by 2, 4, 8 <ODD TAP Enable> <SNRBoost Coeff1> 1D 0 <FINE GAIN> 0 to 6 dB gain in 0.5 dB steps <OFFSET TC> Offset correction time constant 0 <DATAOUT STRENGTH> <LVDS TERMINATION> Internal termination programmability <CUSTOM LOW> Lower 8 bits 1C 16 D1 11 18 (1) (1) <SNRBoost Coeff2> 0 0 0 <DECIMATION FILTER FREQ BANDS> <FILTER COEFFICIENTS> 12 coefficients, each 12 bit signed Multiple functions in a register can be programmed in a single write operation. Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 DESCRIPTION OF SERIAL REGISTERS Table 8. A7–A0 (hex) D7 D6 D5 D4 D3 D2 D1 D0 00 0 0 0 0 0 0 <RST> Software Reset <SERIAL READOUT> D1 1 <RST> Software reset applied – resets all internal registers and self-clears to 0. D0 0 1 <SERIAL READOUT> Serial readout disabled Serial readout enabled, SDOUT functions as serial data readout pin. Table 9. A7–A0 (hex) 10 D7–D6 01 00 11 10 D7 D6 <CLKOUT STRENGTH> D5 D4 D3 D2 D1 D0 0 0 0 0 0 0 D2 D1 D0 <CLKOUT STRENGTH> Output clock buffer drive strength control WEAKER than default drive DEFAULT drive strength STRONGER than default drive strength (recommended for load capacitances > 5 pF) MAXIMUM drive strength (recommended for load capacitances > 5 pF) Table 10. A7–A0 (hex) D7 D6 11 0 0 D5 D4 <CURRENT DOUBLE> LVDS buffer current double D3 LVDS CURRENT> LVDS buffer current programmability D1–D0 01 00 11 10 <DATAOUT STRENGTH> Output data buffer drive strength control WEAKER than default drive DEFAULT drive strength STRONGER than default drive strength (recommended for load capacitances > 5 pF) MAXIMUM drive strength (recommended for load capacitances > 5 pF) D3–D2 00 01 10 11 <LVDS CURRENT> LVDS Current programmability 3.5 mA 2.5 mA 4.5 mA 1.75 mA D5–D4 00 01 10 11 CURRENT DOUBLE> LVDS Current double control default current, set by <LVDS CURR> LVDS clock buffer current is doubled, 2x <LVDS CURR> LVDS data and clock buffers current are doubled, 2x <LVDS CURR> unused DATAOUT STRENGTH> Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 17 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com Table 11. A7–A0 (hex) D7 D6 12 0 0 D5 D4 D3 D2 D1 D0 <LVDS TERMINATION> Internal termination programmability D5–D3 000 001 010 011 100 101 110 111 <LVDS DATA TERM> Internal termination control for data outputs No internal termination 300 Ω 180 Ω 110 Ω 150 Ω 100 Ω 81 Ω 60 Ω D2–D0 000 001 010 011 100 101 110 111 <LVDS CLK TERM> Internal termination control for clock output No internal termination 300 Ω 180 Ω 110 Ω 150 Ω 100 Ω 81 Ω 60 Ω Table 12. D4 0 1 18 A7–A0 (hex) D7 D6 D5 D4 D3 D2 D1 D0 13 0 0 0 <OFFSET FREEZE> 0 0 0 0 <OFFSET FREEZE> Offset correction becomes inactive and the last estimated offset value is used to cancel the offset Offset correction active Offset correction inactive Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 Table 13. A7–A0 (hex) D7 14 <OVRD> Over-ride bit D6 D5 D4 D3 0 <OUTPUT INTERFACE> LVDS or CMOS interface <COARSE GAIN> 3.5 dB gain <REF> Internal / External reference D2 D1 D0 <POWER DOWN MODES> D2-D0 000 001 010 011 100 101 110 111 <POWER DOWN MODES> Normal operation Channel A output buffer disabled Channel B output buffer disabled Channel A and B output buffers disabled Global power down Channel A standby Channel B standby Multiplexed mode, MUX– (only with CMOS interface) Channel A and B data is multiplexed and output on DA10 to DA0 pins. D3 0 1 <REF> Reference mode Internal reference enabled External reference enabled D4 0 1 <COARSE GAIN> Coarse gain control 0 dB coarse gain 3.5 dB coarse gain D5 0 1 <OUTPUT INTERFACE> Output interface selection Parallel CMOS data outputs DDR LVDS data outputs D7 <OVRD> Over-ride bit – the LVDS/CMOS selection, power down and MUX modes can also be controlled using parallel pins. By setting <OVRD> = 1, register bits LVDS <CMOS> and <POWER DOWN MODES> will over-ride the settings of the parallel pins. Disable over-ride Enable over-ride 0 1 Table 14. A7–A0 (hex) D7 D6 D5 D4 D3 16 0 0 0 DATA FORMAT> 2s complement or straight binary Bit / Byte wise (LVDS only) D2 D1 D0 <TEST PATTERNS> D2–D0 000 001 010 011 100 101 110 111 <TEST PATTERNS> Test Patterns to verify capture Normal ADC operation Outputs all zeros Outputs all ones Outputs toggle pattern Outputs digital ramp Outputs custom pattern Unused Unused D3 0 1 Bit-wise/Byte-wise selection (DDR LVDS mode ONLY) Bit wise – Odd bits (D1, D3, D5, D7, D9) on CLKOUT rising edge and Even bits (D0, D2, D4, D6, D8, D10) on CLKOUT falling edge Byte wise – Lower 7 bits (D0-D6) at CLKOUT rising edge and Upper 4 bits (D7-D10) at CLKOUT falling edge D4 0 1 <DATA FORMAT> Data format selection 2s complement Straight binary Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 19 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com Table 15. A7–A0 (hex) D7 D6 D5 D4 17 0 0 0 0 D2–D0 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 Others D3 D2 D1 D0 <FINE GAIN> 0 to 6 dB gain in 0.5 dB steps <FINE GAIN> Gain programmability in 0.5 dB steps 0 dB gain, default after reset 0.5 dB gain 1.0 dB gain 1.5 dB gain 2.0 dB gain 2.5 dB gain 3.0 dB gain 3.5 dB gain 4.0 dB gain 4.5 dB gain 5.0 dB gain 5.5 dB gain 6.0 dB gain Unused Table 16. A7–A0 (hex) D7 D6 0 0 18 19 D5 D4 D3 <CUSTOM LOW> Lower 5bits D1 D0 0 0 0 <CUSTOM HIGH> Upper 6 bits D7-D4 <CUSTOM LOW> 5 lower bits of custom pattern available at the output instead of ADC data. D5-D0 <CUSTOM HIGH> 6 upper bits of custom pattern available at the output instead of ADC data. 20 D2 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 Table 17. A7–A0 (hex) D7 1A <LOW LATENCY> D6 D5 D4 D3 <OFFSET TC> Offset correction time constant D2 D1 D0 <GAIN CORRECTION> 0 to 0.5 dB, steps of 0.05 dB D2–D0 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 <GAIN CORRECTION> Enables fine gain correction in steps of 0.05 dB (same correction applies to both channels) 0 dB gain, default after reset +0.5 dB gain +0.10 dB gain +0.15 dB gain +0.20 dB gain +0.25 dB gain +0.30 dB gain +0.35 dB gain +0.40 dB gain +0.45 dB gain +0.5 dB gain D6-D4 000 001 010 011 100 101 110 111 <OFFSET TC> Time constant of offset correction in number of clock cycles (seconds, for sampling frequency = 125MSPS) 227 (1.1 s) 226 (0.55 s) 225 (0.27 s) 224 (0.13 s) 228 (2.15 s) 229 (4.3 s) 227 (1.1 s) 227 (1.1 s) D7 0 1 <LOW LATENCY> Default latency, 13 clock cycles Low latency enabled, 9 clock cycles – Digital Processing Block is bypassed. Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 21 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com Table 18. A7–A0 (hex) D7 D6 D5 D4 D3 1B <OFFSET Enable> Offset correction enable <SNRBoo st Enable> <FILTER COEFF SELECT> In-built or custom coefficients <FILTER Enable> Enable decimation <ODD TAP Enable> D2 D2-D0 000 001 011 100 <DECIMATION RATE> Decimation filters Decimate by 2 (pre-defined or user coefficients can be used) Decimate by 4 (pre-defined or user coefficients can be used) No decimation (Pre-defined coefficients are disabled, only custom coefficients are available) Decimate by 8 (Only custom coefficients are available) D3 0 1 <ODD TAP ENABLE> Even taps enabled (24 coefficients) 0 Odd taps enabled (23 coefficients) D4 0 1 <FILTER ENABLE> Digital Filter Bypass Digital Filter Enabled D5 0 1 <FILTER COEFF SELECT> Pre-defined coefficients are loaded in the filter User-defined coefficients are loaded in the filter (coefficients have to be loaded in registers – to - ) D6 0 1 <SNRBoost Enable> SNRBoost disabled SNRBoost enabled D7 0 1 <OFFSET Enable> Offset correction disabled Offset correction enabled D1 D0 <DECIMATION RATE> Decimate by 2,4,8 Table 19. A7–A0 (hex) D7 D6 1C D5 D4 D3 D2 <SNRBoost Coeff1> D7-D4, D3-D0 D1 D0 <SNRBoost Coeff2> <SNRBoost Coeff1>, <SNRBoost Coeff2> - The two coefficients can be set independently. See SNR enhancement using SNRBoost for details. Table 20. A7–A0 (hex) D7 D6 D5 D4 D3 D2 1D 0 0 0 0 0 0 D1-D0 00 01 10, 11 <DECIMATION FILTER FREQ BAND> Decimation filters With decimate by 2, <DECIMATION RATE> = 000: Low pass filter (–6 dB frequency at Fs/4) High pass filter (–6 dB frequency at Fs/4) Unused 00 01 10 11 With decimate by 4, <DECIMATION RATE> = 001: Low pass filter (-3 dB frequency at Fs/8) Band pass filter (center frequency at 3Fs/16) Band pass filter (center frequency at 5Fs/16) High pass filter (-3 dB frequency at 3Fs/8) 22 Submit Documentation Feedback D1 D0 <DECIMATION FILTER FREQ BANDS> Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 DB1 2 DB2 3 NC DRGND DRVDD CLKOUT SDOUT DA10 DA9 DA8 DA7 DA6 DA5 63 62 61 60 59 58 57 56 55 54 53 52 51 50 PAD (Connected to DRGND ) DRGND NC 64 1 NC DRVDD DB0 DRGND PIN DESCRIPTION (CMOS INTERFACE) 49 48 DRVDD 47 DA4 46 DA3 45 DA2 8 41 NC DB8 9 40 NC DB9 10 39 DRGND DB10 11 38 DRVDD RESET 12 37 CTRL3 SCLK 13 36 CTRL2 SDATA 14 35 CTRL1 SEN 15 34 AVDD AVDD 16 17 18 19 20 21 22 23 24 25 26 27 28 29 INP_A AVDD 30 31 33 32 AGND DB7 AGND NC INM_A 42 AGND 7 AGND DB6 CLKM DA0 CLKP 43 AGND 6 VCM DB5 AGND DA1 AGND 44 INM_B 5 INP_B DB4 AGND 4 AGND DB3 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 23 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com Pin Assignments (CMOS INTERFACE) PIN NAME DESCRIPTION AVDD Analog power supply AGND Analog ground CLKP, CLKM INP_A, INM_A PIN NUMBER NUMBER OF PINS 16, 33, 34 3 17, 18, 21, 22, 24, 27, 28, 31, 32 9 Differential input clock 25, 26 2 Differential input signal – channel A 29, 30 2 INP_B, INM_B Differential input signal – channel B 19, 20 2 VCM Internal reference mode – Common-mode voltage output. External reference mode – Reference input. The voltage forced on this pin sets the ADC internal references. 23 1 RESET Serial interface RESET input. In serial interface mode, the user must initialize internal registers through hardware RESET by applying a high-going pulse on this pin or by using software reset (refer to Serial Interface section). In parallel interface mode, the user has to tie RESET pin permanently high. (SCLK, SDATA and SEN are used as parallel pin controls in this mode) The pin has an internal 100 kΩ pull-down resistor. 12 1 SCLK This pin functions as serial interface clock input when RESET is low. It functions as analog control pin when RESET is tied high & controls coarse gain and internal/external reference selection. See Table 4 for details. The pin has an internal pull-down resistor to ground. 13 1 SDATA This pin functions as serial interface data input when RESET is low. The pin has an internal pull-down resistor to ground. 14 1 SDOUT It functions as serial data readout pin ONLY when <SERIAL READBACK> =1. 56 1 SEN This pin functions as serial interface enable input when RESET is low. It functions as analog control pin when RESET is tied high & controls the output interface (LVDS/CMOS) and data format selection. See Table 5 for details. The pin has an internal pull-up resistor to AVDD. 15 1 35 1 36 1 CTRL1 CTRL2 CTRL3 These are digital logic input pins. Together they control various power down and multiplexed mode. see Table 6 for details DA10 to DA0 37 1 Channel A 11-bit data outputs, CMOS 43–47, 50–55 11 DB10 to DB0 Channel B 11-bit data outputs, CMOS 2–11, 63 11 CLKOUT CMOS Output clock 57 1 DRVDD Digital supply 1, 38, 48, 58 4 DRGND Digital ground 39, 49, 59, 64 and PAD 4 PAD Digital ground. Solder the pad to the digital ground on the board using multiple vias for good electrical and thermal performance. – 1 NC Do not connect 40–42, 60–62 6 24 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 DB2M 2 DB2P 3 DB4M NC DRGND DRVDD CLKOUTP CLKOUTM DA10P DA10M DA8P DA8M DA6P DA6M 63 62 61 60 59 58 57 56 55 54 53 52 51 50 DRGND NC 64 1 DB0M DRVDD DB0P DRGND PIN DESCRIPTION (LVDS INTERFACE) 49 48 DRVDD 47 DA4P 46 DA4M 4 45 DA2P DB4P 5 44 DA2M DB6M 6 43 DA0P DB6P 7 42 DA0M DB8M 8 41 NC DB8P 9 40 NC DB10M 10 39 DRGND DB10P 11 38 DRVDD RESET 12 37 CTRL3 SCLK 13 36 CTRL2 SDATA 14 35 CTRL1 SEN 15 34 AVDD AVDD 26 27 28 29 30 31 33 32 INM_A AGND AGND AGND 25 INP_A INM_B 24 AGND INP_B 23 AGND AGND 22 CLKM 21 CLKP 20 AGND 19 VCM 18 AGND 16 17 AGND AVDD PAD (Connected to DRGND ) Pin Assignments (LVDS INTERFACE) PIN NAME DESCRIPTION AVDD Analog power supply AGND Analog ground CLKP, CLKM INP_A, INM_A PIN NUMBER NUMBER OF PINS 16, 33, 34 3 17, 18, 21, 22, 24, 27, 28, 31,32 9 Differential input clock 25, 26 2 Differential input signal – Channel A 29, 30 2 INP_B, INM_B Differential input signal – Channel B 19, 20 2 VCM Internal reference mode – Common-mode voltage output. External reference mode – Reference input. The voltage forced on this pin sets the ADC internal references. 23 1 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 25 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com Pin Assignments (LVDS INTERFACE) (continued) PIN NAME DESCRIPTION PIN NUMBER NUMBER OF PINS RESET Serial interface RESET input. In serial interface mode, the user must initialize internal registers through hardware RESET by applying a high-going pulse on this pin or by using software reset (refer to Serial Interface section). In parallel interface mode, the user has to tie RESET pin permanently high. (SCLK, SDATA and SEN are used as parallel pin controls in this mode) The pin has an internal 100 kΩ pull-down resistor. 12 1 SCLK This pin functions as serial interface clock input when RESET is low. It functions as analog control pin when RESET is tied high and controls coarse gain and internal/external reference selection. See Table 4 for details. The pin has an internal pull-down resistor to ground. 13 1 SDATA This pin functions as serial interface data input when RESET is low. The pin has an internal pull-down resistor to ground. 14 1 SEN This pin functions as serial interface enable input when RESET is low. It functions as analog control pin when RESET is tied high & controls the output interface (LVDS/CMOS) and data format selection. See Table 5 for details. The pin has an internal pull-up resistor to AVDD. 15 1 35 1 36 1 CTRL1 These are digital logic input pins. Together they control various power down and multiplexed mode. See Table 6 for details. CTRL2 CTRL3 37 1 40, 41, 60, 61 4 Channel A Differential output data 0 and D0 multiplexed, true 43 1 DA0M Channel A Differential output data 0 and D0 multiplexed, complement 42 1 DA2P Channel A Differential output data D1 and D2 multiplexed, true 45 1 DA2M Channel A Differential output data D1 and D2 multiplexed, complement 44 1 DA4P Channel A Differential output data D3 and D4 multiplexed, true 47 1 DA4M Channel A Differential output data D3 and D4 multiplexed, complement 46 1 DA6P Channel A Differential output data D5 and D6 multiplexed, true 51 1 DA6M Channel A Differential output data D5 and D6 multiplexed, complement 50 1 DA8P Channel A Differential output data D7 and D8 multiplexed, true 53 1 DA8M Channel A Differential output data D7 and D8 multiplexed, complement 52 1 DA10P Channel A Differential output data D9 and D10 multiplexed, true 55 1 DA10M Channel A Differential output data D9 and D10 multiplexed, complement 54 1 CLKOUTP Differential output clock, true 57 1 CLKOUTM Differential output clock, complement 56 1 DB0P Channel B Differential output data 0 and D0 multiplexed, true 63 1 DB0M Channel B Differential output data 0 and D0 multiplexed, complement 62 1 DB2P Channel B Differential output data D1 and D2 multiplexed, true 3 1 DB2M Channel B Differential output data D1 and D2 multiplexed, complement 2 1 DB4P Channel B Differential output data D3 and D4 multiplexed, true 5 1 DB4M Channel B Differential output data D3 and D4 multiplexed, complement 4 1 DB6P Channel B Differential output data D5 and D6 multiplexed, true 7 1 DB6M Channel B Differential output data D5 and D6 multiplexed, complement 6 1 DB8P Channel B Differential output data D7 and D8 multiplexed, true 9 1 DB8M Channel B Differential output data D7 and D8 multiplexed, complement 8 1 DB10P Channel B Differential output data D9 and D10 multiplexed, true 11 1 DB10M Channel B Differential output data D9 and D10 multiplexed, complement 10 1 DRVDD Digital supply 1, 38, 48, 58 4 DRGND Digital ground 39, 49, 59, 64 and PAD 4 NC Do not connect DA0P 26 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 Pin Assignments (LVDS INTERFACE) (continued) DESCRIPTION PIN NUMBER NUMBER OF PINS Digital ground. Solder the pad to the digital ground on the board using multiple vias for good electrical and thermal performance. – 1 PIN NAME PAD TYPICAL CHARACTERISTICS All plots are at 25°C, AVDD = 3.3 V, DRVDD = 3.3 V, sampling frequency = 125 MSPS, sine wave clock, 50% clock duty cycle, –1 dBFS differential analog input, internal reference mode, 0 dB gain, applies to CMOS and LVDS interfaces (unless otherwise noted). SPECTRUM FOR 20 MHZ INPUT SIGNAL SPECTRUM FOR 70 MHZ INPUT SIGNAL 0 0 SFDR = 88.8 dBc SINAD = 67 dBFS SNR = 67.1 dBFS THD = 88 dBc −40 −20 Amplitude − dB Amplitude − dB −20 −60 −80 −40 −60 −80 −100 −100 −120 −120 −140 −140 0 10 20 30 40 50 60 f − Frequency − MHz 0 10 20 30 40 50 60 f − Frequency − MHz G001 G002 Figure 9. Figure 10. SPECTRUM FOR 190 MHZ INPUT SIGNAL SPECTRUM FOR 2-TONE INPUT SIGNAL (INTERMODULATION DISTORTION) 0 0 SFDR = 79.1 dBc SINAD = 66.4 dBFS SNR = 66.7 dBFS THD = 77.5 dBc −20 −40 fIN1 = 190.1 MHz, –7 dBFS fIN2 = 185.3 MHz, –7 dBFS 2-Tone IMD = –88.8 dBFS SFDR = –96 dBFS −20 Amplitude − dB Amplitude − dB SFDR = 86.7 dBc SINAD = 67 dBFS SNR = 67 dBFS THD = 85.1 dBc −60 −80 −40 −60 −80 −100 −100 −120 −120 −140 −140 0 10 20 30 40 f − Frequency − MHz 50 60 0 G003 Figure 11. 10 20 30 40 50 f − Frequency − MHz 60 G004 Figure 12. Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 27 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com TYPICAL CHARACTERISTICS (continued) All plots are at 25°C, AVDD = 3.3 V, DRVDD = 3.3 V, sampling frequency = 125 MSPS, sine wave clock, 50% clock duty cycle, –1 dBFS differential analog input, internal reference mode, 0 dB gain, applies to CMOS and LVDS interfaces (unless otherwise noted). SFDR vs INPUT FREQUENCY (CMOS INTERFACE) SNR vs INPUT FREQUENCY (CMOS INTERFACE) 94 70 92 88 SNR − dBFS SFDR − dBc 69 Gain = 3.5 dB 90 86 84 82 68 Gain = 0 dB 67 Gain = 3.5 dB 66 80 Gain = 0 dB 65 78 76 64 0 25 50 75 100 125 150 175 200 fIN − Input Frequency − MHz 0 25 50 75 100 125 150 175 200 fIN − Input Frequency − MHz G005 Figure 13. G006 Figure 14. SFDR vs INPUT FREQUENCY (LVDS INTERFACE) SNR vs INPUT FREQUENCY (LVDS INTERFACE) 95 70 93 69 Gain = 3.5 dB 89 SNR − dBFS SFDR − dBc 91 87 85 83 68 Gain = 0 dB 67 81 Gain = 3.5 dB Gain = 0 dB 79 66 77 75 65 0 25 50 75 100 125 150 175 200 fIN − Input Frequency − MHz 0 25 50 75 100 G007 Figure 15. SFDR vs INPUT FREQUENCY ACROSS GAINS 175 200 G008 SINAD vs INPUT FREQUENCY ACROSS GAINS 72 Input adjusted to get −1dBFS input Input adjusted to get −1dBFS input 70 2 dB 3 dB 0 dB 5 dB 4 dB SINAD − dBFS 95 SFDR − dBc 150 Figure 16. 100 90 85 80 6 dB 1 dB 0 dB 1 dB 68 2 dB 66 64 3 dB 5 dB 4 dB 62 75 6 dB 60 0 25 50 75 100 125 150 fIN − Input Frequency − MHz 175 200 0 25 G009 Figure 17. 28 125 fIN − Input Frequency − MHz 50 75 100 125 150 fIN − Input Frequency − MHz 175 200 G010 Figure 18. Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 TYPICAL CHARACTERISTICS (continued) All plots are at 25°C, AVDD = 3.3 V, DRVDD = 3.3 V, sampling frequency = 125 MSPS, sine wave clock, 50% clock duty cycle, –1 dBFS differential analog input, internal reference mode, 0 dB gain, applies to CMOS and LVDS interfaces (unless otherwise noted). PERFORMANCE vs AVDD SUPPLY PERFORMANCE vs DRVDD SUPPLY 88 88 69.0 87 87 68.5 SFDR 69.0 fIN = 70.1 MHz AVDD = 3.31 V 68.5 85 67.5 SNR 84 3.1 3.2 3.3 3.4 AVDD − Supply Voltage − V 67.5 SNR 84 67.0 83 66.5 82 1.8 66.0 3.6 3.5 85 2.0 2.2 2.4 PERFORMANCE vs TEMPERATURE 87 68.5 85 67.5 SNR 84 67.0 83 SFDR − dBc 68.0 66.5 80 T − Temperature − °C 90 SFDR 80 50 75 SNR 40 65 20 60 10 55 50 −50 −40 0 G014 PERFORMANCE vs INPUT CLOCK DUTY CYCLE fIN = 20.1 MHz 72 SFDR 71 fIN = 20.1 MHz 90 70 88 70 86 69 68 SNR 82 67 80 66 1.5 Input Clock Amplitude − VPP 2.0 65 2.5 SFDR − dBc 71 SNR − dBFS SFDR − dBc −10 92 73 1.0 −20 Figure 22. PERFORMANCE vs INPUT CLOCK AMPLITUDE 0.5 −30 Input Amplitude − dBFS G013 94 78 0.0 70 30 Figure 21. 84 85 60 0 −60 66.0 60 95 fIN = 20.1 MHz 70 SNR − dBFS SFDR − dBc 86 90 G012 80 SFDR 92 66.0 3.6 100 90 40 3.4 PERFORMANCE vs INPUT AMPLITUDE fIN = 70.1 MHz 20 3.2 100 69.0 0 3.0 Figure 20. 88 −20 2.8 DRVDD − Supply Voltage − V G011 Figure 19. 82 −40 2.6 SNR − dBFS 82 3.0 66.5 fIN = 70.1 MHz DRVDD = 3.31 V 68.0 88 69 SFDR 86 68 SNR 84 67 82 66 80 SNR − dBFS 83 67.0 86 SNR − dBFS 68.0 SFDR − dBc 86 SNR − dBFS SFDR − dBc SFDR 65 35 40 G015 Figure 23. 45 50 55 60 65 Input Clock Duty Cycle − % G016 Figure 24. Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 29 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com TYPICAL CHARACTERISTICS (continued) All plots are at 25°C, AVDD = 3.3 V, DRVDD = 3.3 V, sampling frequency = 125 MSPS, sine wave clock, 50% clock duty cycle, –1 dBFS differential analog input, internal reference mode, 0 dB gain, applies to CMOS and LVDS interfaces (unless otherwise noted). OUTPUT NOISE HISTOGRAM (INPUTS TIED TO COMMON-MODE) PERFORMANCE IN EXTERNAL REFERENCE MODE 70 93 75 fIN = 20.1 MHz External Reference Mode 60 73 40 30 SFDR 89 SNR − dBFS SFDR − dBc Occurence − % 91 50 71 87 69 20 SNR 85 67 10 0 83 1.30 1018 1019 1020 1021 1022 1023 1024 1025 Output Code 1.40 1.45 1.50 1.55 1.60 1.65 65 1.70 VVCM − VCM Voltage − V G017 G018 Figure 26. COMMON-MODE REJECTION RATIO vs FREQUENCY POWER DISSIPATION vs SAMPLING FREQUENCY (DDR LVDS AND CMOS) 0 1.0 −10 0.9 PD − Power Dissipation − W Figure 25. −20 −30 CMRR − dBc 1.35 −40 −50 −60 −70 −80 fIN = 2.5 MHz CL = 5 pF 0.8 LVDS 0.7 0.6 0.5 CMOS 0.4 0.3 0.2 0.1 −90 0.0 −100 0 25 50 75 100 125 150 175 0 200 f − Frequency − MHz 25 50 75 100 fS − Sampling Frequency − MSPS G019 Figure 27. 125 G020 Figure 28. DRVDD CURRENT vs SAMPLING FREQUENCY ACROSS LOAD CAPACITANCE (CMOS) 70 3.3 V, No Load DRVDD Current − mA 60 1.8 V, 5 pF 50 1.8 V, 10 pF 3.3 V, 5 pF 40 3.3 V, 10 pF 30 20 10 1.8 V, No Load 0 0 25 50 75 100 fS − Sampling Frequency − MSPS 125 G021 Figure 29. 30 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 APPLICATION INFORMATION THEORY OF OPERATION ADS62C15 is a low power 11-bit dual channel pipeline ADC family fabricated in a CMOS process using switched capacitor techniques. The conversion process is initiated by a rising edge of the external input clock. Once the signal is captured by the input sample and hold, the input sample is sequentially converted by a series of small resolution stages, with the outputs combined in a digital correction logic block. At every clock edge the sample propagates through the pipeline resulting in a data latency of 14 clock cycles. The output is available as 11-bit data, in DDR LVDS or CMOS and coded in either straight offset binary or binary 2s complement format. ANALOG INPUT The analog input consists of a switched-capacitor based differential sample and hold architecture. This differential topology results in very good AC performance even for high input frequencies at high sampling rates. The INP and INM pins have to be externally biased around a common-mode voltage of 1.5 V, available on VCM pin. For a full-scale differential input, each input pin INP, INM has to swing symmetrically between VCM + 0.5 V and VCM – 0.5 V, resulting in a 2 VPP differential input swing. The maximum swing is determined by the internal reference voltages REFP (2.5 V nominal) and REFM (0.5 V, nominal). Sampling switch Lpkg~ 2 nH Sampling capacitor RCR Filter INP 25 E Cbond ~ 1 pF Cpar2 1 pF 50 E Resr 100 E 3.2 pF INM Resr 100 E Ron 10 E Csamp 4.0 pF Ron 15 E 25 E Cbond ~ 1 pF Csamp 4.0 pF Cpar1 0.8 pF 50 E Lpkg~ 2 nH Ron 15 E Sampling capacitor Cpar2 1 pF Sampling switch Figure 30. Analog Input Equivalent Circuit The input sampling circuit has a high 3-dB bandwidth that extends up to 450 MHz (measured from the input pins to the sampled voltage). Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 31 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com 1 0 Magnitude − dB −1 −2 −3 −4 −5 −6 −7 0 100 200 300 400 500 fI − Input Frequency − MHz 600 G022 Figure 31. ADC Analog Bandwidth Drive Circuit Requirements For optimum performance, the analog inputs must be driven differentially. This improves the common-mode noise immunity and even order harmonic rejection. A <5 Ω resistor in series with each input pin is recommended to damp out ringing caused by the package parasitics. It is also necessary to present low impedance (50 Ω) for the common mode switching currents. This can be achieved by using two resistors from each input terminated to the common mode voltage (VCM). In addition, the drive circuit may have to be designed to provide a low insertion loss over the desired frequency range and matched impedance to the source. While doing this, the ADC input impedance must be considered. Figure 32 and Figure 33 show the impedance (Zin = Rin || Cin) looking into the ADC input pins. R − Resistance − kΩ 100 10 1 0.1 0.01 0 100 200 300 400 f − Frequency − MHz 500 600 G023 Figure 32. ADC Analog Input Resistance (Rin) Across Frequency 32 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 9 C − Capacitance − pF 8 7 6 5 4 3 2 1 0 0 100 200 300 400 500 f − Frequency − MHz 600 G024 Figure 33. ADC Analog Input Capacitance (Cin) Across Frequency Using RF-Transformer Based Drive Circuits Figure 34 shows a configuration using a single 1:1 turns ratio transformer (for example, Coilcraft WBC1-1) that can be used for low input frequencies (about 100 MHz). The single-ended signal is fed to the primary winding of the RF transformer. The transformer is terminated on the secondary side. Putting the termination on the secondary side helps to shield the kickbacks caused by the sampling circuit from the RF transformer’s leakage inductances. The termination is accomplished by two resistors connected in series, with the center point connected to the 1.5 V common mode (VCM pin). The value of the termination resistors (connected to common mode) has to be low ( <100 Ω) to provide a low-impedance path for the ADC common-mode switching currents. 0.1 mF INP 0.1mF 25E 25E INM 1:1 VCM Figure 34. Drive Circuit at Low Input Frequencies At high input frequencies, the mismatch in the transformer parasitic capacitance (between the windings) results in degraded even-order harmonic performance. Connecting two identical RF transformers back-to-back helps minimize this mismatch, and good performance is obtained for high frequency input signals. Figure 35 shows an example using two transformers (Coilcraft WBC1-1). An additional termination resistor pair (enclosed within the shaded box) may be required between the two transformers to improve the balance between the P and M sides. The center point of this termination must be connected to ground. Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 33 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com 0.1 mF INP 50 E 0.1 mF 50E 50E 50 E INM 1 :1 1:1 VCM Figure 35. Drive Circuit at High Input Frequencies Using Differential Amplifier Drive Circuits Figure 36 shows a drive circuit using a differential amplifier (TI's THS4509) to convert a single-ended input to differential output that can be interface to the ADC analog input pins. In addition to the single-ended to differential conversion, the amplifier also provides gain (10 dB). RFIL helps to isolate the amplifier outputs from the switching input of the ADC. Together with CFIL it also forms a low-pass filter that band-limits the noise (and signal) at the ADC input. As the amplifier output is ac-coupled, the common-mode voltage of the ADC input pins is set using two 200 Ω resistors connected to VCM. The amplifier output can also be dc-coupled. Using the output common-mode control of the THS4509, the ADC input pins can be biased to 1.5 V. In this case, use +4 V and –1 V supplies for the THS4509 so that its output common-mode voltage (1.5 V) is at mid-supply. RF +VS 500 W 0.1 mF 0.1 mF 10 mF RFIL 0.1 mF 5W INP RG RS CFIL 0.1 mF RT CFIL 200 W 200 W 5W INM RG RS || RT RFIL 500 W 0.1 mF -VS 0.1 mF VCM 0.1 mF 0.1 mF 10 mF RF Figure 36. Drive Circuit Using the THS4509 34 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 Input Common-Mode To ensure a low-noise common-mode reference, the VCM pin is filtered with a 0.1µF low-inductance capacitor connected to ground. The VCM pin is designed to directly drive the ADC inputs. The input stage of the ADC sinks a common-mode current in the order of 165 µA (at 125 MSPS). Equation 1 describes the dependency of the common-mode current and the sampling frequency. 165 mA Fs 125 MSPS (1) This equation helps to design the output capability and impedance of the CM driving circuit accordingly. REFERENCE ADS62C15 has built-in internal references REFP and REFM, requiring no external components. Design schemes are used to linearize the converter load seen by the references; this and the on-chip integration of the requisite reference capacitors eliminates the need for external decoupling. The full-scale input range of the converter can be controlled in the external reference mode as explained below. The internal or external reference modes can be selected by programming the serial interface register bit (REF). INTREF INTERNAL REFERENCE VCM 1 kW 4 kW INTREF EXTREF REFM REFP Figure 37. Reference Section Internal Reference When the device is in internal reference mode, the REFP and REFM voltages are generated internally. Common-mode voltage (1.5 V nominal) is output on VCM pin, which can be used to externally bias the analog input pins. External Reference When the device is in external reference mode, the VCM acts as a reference input pin. The voltage forced on the VCM pin is buffered and gained by 1.33 internally, generating the REFP and REFM voltages. The differential input voltage corresponding to full-scale is given in Equation 2. Full-scale differential input pp = (Voltage forced on VCM) × 1.33 In this mode, the 1.5 V common-mode voltage to bias the input pins has to be generated externally. Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 35 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com SNR Enhancement Using SNRBoost SNRBoost technology makes it possible to overcome SNR limitations due to quantization noise. With SNRBoost, enhanced SNR can be obtained for any bandwidth (less than Nyquist, Fs/2Table 1). The SNR improvement is achieved without affecting the default harmonic performance. The mode is disabled by default after reset and can be enabled using register bit <SNRBoost Enable>. The mode is disabled by default after reset and can be enabled using register bit <SNRBoost Enable>. When it is enabled, the noise floor in the spectrum acquires a typical bath-tub shape as shown in Figure 38. The bath-tub is centered around a specific frequency (called “center frequency”). The center frequency is located mid-way between two corner frequencies, which are specified by the SNRBoost coefficients (Register bits <SNRBoost Coeff1> and SNRBoost Coeff2>). Table 21 shows the relation between each coefficient and its corner frequency. By choosing appropriate coefficients, the bath-tub can be positioned over the frequency range 0 to Fs/2 (Table 22 shows some examples). By positioning the bath-tub within the desired signal band, SNR improvement can be achieved (see Table 1). Note that as the bandwidth is increased, the amount of SNR improvement reduces. 0 fS =125 MSPS, fIN = 117 MHz -20 Amplitude - dB -40 -60 -80 -100 -120 -140 0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 Normalized frequency, (f/fs) 0.40 0.45 0.50 Figure 38. Spectrum with SNRBoost enabled Table 21. Setting The Corner Frequency 36 SNRBoost Coefficient value Normalized Corner Frequency (f/fs) SNRBoost Coefficient value Normalized Corner Frequency (f/fs) 7 0.08 F 0.27 6 0.12 E 0.29 5 0.14 D 0.31 4 0.17 C 0.33 3 0.19 B 0.36 2 0.21 A 0.38 1 0.23 9 0.42 0 0.25 8 0.50 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 Table 22. Positioning The Center Frequency SNRBoost Coefficient1 <SNRBoost Coeff1> Normalized Corner Frequency1 (f/fs) SNRBoost Coefficient2 <SNRBoost Coeff2> Normalized Corner Frequency2 (f/fs) Center Frequency (1) Fsx0.25 (1) 0 0.25 0 0.25 F 0.27 1 0.23 Fsx0.25 6 0.12 2 0.21 Fsx0.165 D 0.31 B 0.36 Fsx0.335 9 0.42 7 0.08 Fsx0.25 Center frequency = Fs × (Normalized corner freq1 + Normalized corner freq2)/2) SNRBoost does not introduce any group delay in the input signal path. The ADC latency increases by one clock cycle to 15 compared to 14 clock cycles with the mode disabled. When it is enabled using the serial interface, the mode becomes fully active 4 input clock cycles after the 16th SCLK falling edge. When it is disabled, normal data (without SNRBoost) resumes after one clock cycle. Serial register write to enable SNRBoost Register address = 0x1B SDATA A7 A6 A1 Register data = 0x40 A0 D7 D6 D1 D0 th 4 clock cycles after the 16 SCLK falling edge, the device starts giving out valid SNRBoost data SCLK SEN clock cycle 1 clock cycle 2 clock cycle 3 clock cycle 4 CLKM CLKP N Analog Input Signal Output Data N+1 N-1 N - 15 N - 14 Figure 39. SNRBoost Active Delay COARSE GAIN AND PROGRAMMABLE FINE GAIN ADS62C15 includes gain settings that can be used to get improved SFDR performance (over 0dB gain mode). For each gain setting, the analog input full-scale range scales proportionally, as shown in Table 23. The coarse gain is a fixed setting of 3.5 dB and is designed to improve SFDR with little degradation in SNR. The fine gain is programmable in 0.5 dB steps from 0 to 6 dB; however the SFDR improvement is achieved at the expense of SNR. So, the programmable fine gain makes it possible to trade-off between SFDR and SNR. The coarse gain makes it possible to get best SFDR but without losing SNR significantly. The gains can be programmed using the serial interface (bits COARSE GAIN and FINE GAIN). Note that the default gain after reset is 0dB. Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 37 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com Table 23. Full-Scale Range Across Gains GAIN, dB TYPE 0 Default after reset FULL-SCALE, VPP 2V 3.5 Coarse (fixed) 1.34 0.5 1.89 1.0 1.78 1.5 1.68 2.0 1.59 2.5 1.50 3.0 Fine (programmable) 3.5 1.42 1.34 4.0 1.26 4.5 1.19 5.0 1.12 5.5 1.06 6.0 1.00 CLOCK INPUT The clock inputs can be driven differentially (SINE, LVPECL or LVDS) or single-ended (LVCMOS), with little or no difference in performance between them. The common-mode voltage of the clock inputs is set to VCM using internal 5 kΩ resistors as shown in Figure 40. This allows using transformer-coupled drive circuits for sine wave clock or ac-coupling for LVPECL, LVDS clock sources (Figure 42 and Figure 43). Clock buffer Lpkg ~2 nH 10 W CLKP Cbond ~ 1 pF Ceq Ceq 5 kW Resr ~100 W VCM 6 pF 5 kW Lpkg ~2 nH 10 W CLKM Cbond ~ 1 pF Resr ~100 W Ceq ~ 1 to 3 pF, equivalent input capacitance of clock buffer Figure 40. Internal Clock Buffer 38 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 100k Impedance − Ω 10k 1k 100 10 5 25 45 65 85 105 fS − Sampling Frequency − MSPS 125 G028 Figure 41. Clock Input Impedance 0.1 mF CLKP Differential Sine-Wave or PECL or LVDS Clock Input CLKM 0.1 mF Figure 42. Differential Clock Driving Circuit Single-ended CMOS clock can be ac-coupled to the CLKP input, with CLKM connected to ground with a 0.1-µF capacitor, as shown in Figure 43. 0.1 mF CLKP CMOS Clock Input CLKM 0.1 mF Figure 43. Single-Ended Clock Driving Circuit For best performance, the clock inputs have to be driven differentially, reducing susceptibility to common-mode noise. For high input frequency sampling, it is recommended to use a clock source with very low jitter. Bandpass filtering of the clock source can help reduce the effect of jitter. There is no change in performance with a non-50% duty cycle clock input. Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 39 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com POWER DOWN ADS62C15 has three power down modes – power down global, individual channel standby and individual channel output buffer disable. These can be set using either the serial register bits or using the control pins CTRL1 to CTRL3. Table 24. Power Down Modes CONFIGURE USING POWER DOWN MODES SERIAL INTERFACE <POWER DOWN MODES> PARALLEL CONTROL PINS CTRL1 CTRL2 WAKE-UP TIME CTRL3 Normal operation 000 low low low — Channel A output buffer disabled 001 low low high Fast (100 ns) Channel B output buffer disabled 010 low high low Fast (100 ns) Channel A and B output buffer disabled 011 low high high Fast (100 ns) Channel A and B powered down 100 high low low Slow (15 µS) Channel A standby 101 high low high Fast (100 ns) Channel B standby 110 high high low Fast (100 ns) Multiplexed (MUX) mode – Output data of channel A and B is multiplexed and available on DA13 to DA0 pins. 111 high high high — Power Down Global In this mode, the entire chip including both the A/D converters, internal reference and the output buffers are powered down resulting in reduced total power dissipation of about 50 mW. The output buffers are in high impedance state. The wake-up time from the global power down to data becoming valid in normal mode is typically 15 µs. Channel Standby (Individual or Both Channels) This mode allows the individual ADCs to be powered down. The internal references are active & this results in fast wake-up time, about 100 ns. The total power dissipation in standby is about 482 mW. Output Buffer Disable (Individual or Both Channels) Each channel’s output buffer can be disabled and put in high impedance state -- wakeup time from this mode is fast, about 100 ns. Input Clock Stop In addition to the above, the converter enters a low-power mode when the input clock frequency falls below 1 MSPS. The power dissipation is about 140 mW. POWER SUPPLY SEQUENCE During power-up, the AVDD and DRVDD supplies can come up in any sequence. The two supplies are separated in the device. Externally, they can be driven from separate supplies or derived from a single supply. 40 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 DIGITAL OUTPUT INFORMATION ADS62C15 provides 11 bit data per channel and a common output clock synchronized with the data. The output interface can be either parallel CMOS or DDR LVDS voltage levels and can be selected using serial register bit <OUTPUT INTERFACE> or parallel pin SEN. Parallel CMOS Interface In the CMOS mode, the output buffer supply (DRVDD) can be operated over a wide range from 1.8 V to 3.3 V (typical). Each data bit is output on separate pin as CMOS voltage level, every clock cycle (see Figure 44). For DRVDD > 2.2 V, it is recommended to use the CMOS output clock (CLKOUT) to latch data in the receiving chip. The rising edge of CLKOUT can be used to latch data in the receiver, even at the highest sampling speed. It is recommended to minimize the load capacitance seen by data and clock output pins by using short traces to the receiver. Also, match the output data and clock traces to minimize the skew between them. For DRVDD < 2.2 V, it is recommended to use external clock (for example, input clock delayed to get desired setup/hold times). CMOS Output Buffers DA0 DA1 DA2 11 Bit Channel A Data DA3 DA9 DA10 CLKOUT DB0 DB1 DB2 11 Bit Channel B Data DB3 DB9 DB10 Figure 44. CMOS Output Interface Output Buffer Strength Programmability Switching noise (caused by CMOS output data transitions) can couple into the analog inputs during the instant of sampling and degrade the SNR. The coupling and SNR degradation increases as the output buffer drive is made stronger. To minimize this, ADS62C15 CMOS output buffers are designed with controlled drive strength to get best SNR. The default drive strength also ensures wide data stable window for load capacitances up to 5 pF and DRVDD supply voltage >2.2 V. To ensure wide data stable window for load capacitance > 5 pF, there exists option to increase the output data and clock drive strengths using the serial interface ( DATAOUT STRENGTH and CLKOUT STRENGTH). Note that for DRVDD supply voltage <2.2 V, it is recommended to use maximum drive strength (for any value of load capacitance). Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 41 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com CMOS Mode Power Dissipation With CMOS outputs, the DRVDD current scales with the sampling frequency and the load capacitance on every output pin. The maximum DRVDD current occurs when each output bit toggles between 0 and 1 every clock cycle. In actual applications, this condition is unlikely to occur. The actual DRVDD current would be determined by the average number of output bits switching, which is a function of the sampling frequency and the nature of the analog input signal. Digital current due to CMOS output switching = CL × DRVDD × (N × FAVG), where CL = load capacitance, N × FAVG = average number of output bits switching. Figure 29 shows the current with various load capacitances across sampling frequencies at 2 MHz analog input frequency. DDR LVDS Interface The LVDS interface works only with 3.3 V DRVDD supply. In this mode, the 11 data bits of each channel and a common output clock are available as LVDS (Low Voltage Differential Signal) levels. Two successive data bits are multiplexed and output on each LVDS differential pair every clock cycle (DDR – Double Data Rate, Figure 46). LVDS Buffers 11 Bit Channel A Data Pins DA0P DA0M Data bits D0, D1 DA2P DA2M Data bits D2, D3 DA10P DA10M Data bits D9, D10 CLKOUTP CLKOUTM 11 Bit Channel B Data Output Clock DB0P DB0M Data bits D0, D1 DB2P DB2M Data bits D2, D3 DB10P DB10M Data bits D9, D10 Figure 45. DDR LVDS Outputs Odd data bits D1, D3, D5, D7, D9 are output at the rising edge of CLKOUTP and even data bits D0, D2, D4, D6, D8, D10 are output at the falling edge of CLKOUTP. Both the rising and falling edges of CLKOUTP have to be used to capture all the data bits. 42 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 CLKOUTM CLKOUTP DA0 (DB0) 0 D0 0 D0 DA2 (DB2) D1 D2 D1 D2 DA4 (DB4) D3 D4 D3 D4 DA6 (DB6) D5 D6 D5 D6 DA8 (DB8) D7 D8 D7 D8 DA10 (DB10) D9 D10 D9 D10 Sample N Sample N + 1 Figure 46. DDR LVDS Interface LVDS Buffer Current Programmability The default LVDS buffer output current is 3.5 mA. When terminated by 100 Ω, this results in a 350-mV single-ended voltage swing (700-mVPP differential swing). The LVDS buffer currents can also be programmed to 2.5 mA, 4.5 mA, and 1.75 mA (LVDS CURRENT). In addition, there exists a current double mode, where this current is doubled for the data and output clock buffers (register bits CURRENT DOUBLE). LVDS Buffer Internal Termination An internal termination option is available (using the serial interface), by which the LVDS buffers are differentially terminated inside the device. The termination resistances available are –300 Ω, 185 Ω, and 150 Ω (nominal with ±20% variation). Any combination of these three terminations can be programmed; the effective termination is the parallel combination of the selected resistances. This results in eight effective terminations from open (no termination) to 60Ω. The internal termination helps to absorb any reflections coming from the receiver end, improving the signal integrity. With 100 Ω internal and 100 Ω external termination, the voltage swing at the receiver end is halved (compared to no internal termination). The voltage swing can be restored by using the LVDS current double mode. Figure 47 and Figure 48 compare the LVDS eye diagrams without and with 100 Ω internal termination. With internal termination, the eye looks clean even with 10 pF load capacitance (from each output pin to ground). The terminations can be programmed using register bits (LVDS TERMINATION). Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 43 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com Figure 47. LVDS Eye Diagram – No Internal Termination, External Termination = 100 Ω Figure 48. LVDS Eye Diagram – With 100Ω Internal Termination, External termination = 100 Ω and LVDS current double mode enabled 44 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 Output Data Format Two output data formats are supported – 2s complement and straight binary. They can be selected using the serial interface register bit <DATA FORMAT> or controlling the SEN pin in parallel configuration mode. In the event of an input voltage overdrive, the digital outputs go to the appropriate full scale level. For a positive overdrive, the output code is 0x7FF in offset binary output format, and 0x3FF in 2s complement output format. For a negative input overdrive, the output code is 0x000 in offset binary output format and 0x400 in 2s complement output format. Multiplexed Output mode This mode is available only with CMOS interface. In this mode, the digital outputs of both the channels are multiplexed and output on a single bus (DB0-DB10 pins), as per the timing diagram shown in Figure 49. The channel A output pins (DA0-DA10) are tri-stated. Since the output data rate on the DB bus is effectively doubled, this mode is recommended only for low sampling frequencies (<65 MSPS). This mode can be enabled using register bits <POWER DOWN MODES> or using the parallel pins CTRL1 -3 (). CLKOUT DB0 DA0 DB0 DA0 DB0 DB1 DA1 DB1 DA1 DB1 DB2 DA2 DB2 DA2 DB2 DB10 DA10 DB10 DA10 DB10 Sample N Sample N + 1 Figure 49. Multiplexed mode – Output Timing Low Latency Mode The default latency of ADS62C15 is 14 clock cycles. For applications, which cannot tolerate large latency, ADS62C15 includes a special mode with 10 clock cycles latency. In the low latency condition, the Digital Processing block is bypassed and its features (offset correction, fine gain, decimation filters) are not available. Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 45 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com DETAILS OF DIGITAL PROCESSING BLOCK CLIPPER 14 bits To output buffers LVDS or CMOS From ADC output Fine Gain (0 to 6 dB 0.5 dB steps) 24 TAP FILTER Gain Correction (0.05 dB steps) - LOW PASS - HIGH PASS - BAND PASS DECIMATION BY 2/4/8 11 bits 11 bits Filter Select 0 OFFSET ESTIMATION BLOCK 11 bits Disable offset correction Freeze offset correction OFFSET CORRECTION Bypass filter SNRBoost FINE GAIN GAIN CORRECTION DIGITAL FILTER & DECIMATION DIGITAL PROCESSING BLOCK NOTE: The digital filter block is bypassed when the SNRBoost mode is enabled. Figure 50. Digital Processing Block Diagram Offset Correction ADS62C15 has an internal offset correction algorithm that estimates and corrects dc offset up to ±10mV. The correction can be enabled using the serial register bit (OFFSET LOOP EN). Once enabled, the algorithm estimates the channel offset and applies the correction every clock cycle. The time constant of the correction loop is a function of the sampling clock frequency. The time constant can be controlled using register bits (OFFSET LOOP TC) as described in Table 25. Table 25. Time Constant of Offset Correction Algorithm (1) 46 <OFFSET LOOP TC> D6-D5-D4 Time constant (TCCLK), number of clock cycles Time constant, sec (=TCCLK × 1/Fs) (1) 000 227 1.1 001 26 2 0.55 010 225 0.27 011 224 0.13 100 228 2.15 101 29 2 4.3 110 227 1.1 111 227 1.1 Sampling frequency, Fs = 125 MSPS Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 It is also possible to freeze the offset correction using the serial interface (<OFFSET LOOP FREEZE>). Once frozen, the offset estimation becomes inactive and the last estimated value is used for correction every clock cycle. Note that the offset correction is disabled by default after reset. Figure 51 shows the time response of the offset correction algorithm, after it is enabled. 1032 1030 Code − LSB 1028 Device With Offset Cancelled 1026 1024 1022 Offset Loop Enabled Here 1020 Device With Initial Offset 1018 1016 0 2 4 6 8 10 12 t − Time − s 14 G029 Figure 51. Time Response of Offset Correction Gain Correction ADS62C15 has ability to make fine corrections to the ADC channel gain. The corrections can be done in steps of 0.05 dB, up to a maximum of 0.5 dB, using the register bits (GAIN CORRECTION). Only positive corrections are supported and the same correction applies to both the channels. Table 26. Gain Correction Values <GAIN CORRECTION> D3-D2-D1-D0 Amount of correction, dB 0000 0 0001 +0.05 0010 +0.1 0011 +0.15 0100 +0.20 0101 +0.25 0110 +0.30 0111 +0.35 1000 +0.40 1001 +0.45 1010 +0.5 Other combinations Unused Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 47 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com Decimation Filters(1) ADS62C15 includes option to decimate the ADC output data with in-built low pass, high pass or band pass filters. The decimation rate and type of filter can be selected using register bits (DECIMATION RATE) and (DECIMATION FILTER TYPE). Decimation rates of 2, 4 or 8 are available and either low pass, high pass or band pass filters can be selected (see Table 27). By default, the decimation filter is disabled – use register bit <DECIMATION ENABLE> to enable it. Table 27. Decimation Filter Modes COMBINATION OF DECIMATION RATES AND FILTER TYPES <DECIMATION FILTER FREQ BAND> <FILTER COEFF SELECT> <DECIMATION ENABLE> 0 0 1 1 0 1 0 0 0 1 1 0 1 0 1 0 1 1 0 0 1 0 0 1 1 1 0 1 Custom filter (user programmable coefficients) 0 0 0 X X 1 1 Custom filter (user programmable coefficients) 0 0 1 X X 1 1 Decimate by 8 Custom filter (user programmable coefficients) 1 0 0 X X 1 1 No decimation Custom filter (user programmable coefficients) 0 1 1 X X 1 0 DECIMATION TYPE OF FILTER <DECIMATION RATE> Decimate by 2 In-built low pass filter (pass band = 0 to Fs/4) 0 0 0 0 In-built high pass filter (pass band = Fs/4 to Fs/2) 0 0 0 0 In-built low pass filter (pass band = 0 to Fs/8) 0 0 1 In-built 2nd band pass filter (pass band = Fs/8 to Fs/4) 0 0 In-built 3 band pass filter (pass band = Fs/4 to 3Fs/8) 0 In-built last band pass filter (pass band = 3Fs/8 to Fs/2) Decimate by 2 Decimate by 4 Decimate by 4 rd Decimation Filter Equation The decimation filter is implemented as 24-tap FIR with symmetrical coefficients (each coefficient is 12-bit signed). The filter equation is: y(n) + ǒ21 Ǔ [h0 11 x(n) ) h1 x(n * 1) ) h2 x(n * 2) ) AAA ) h11 x(n * 11) ) h11 x(n * 12) ) AAA ) h1 x(n * 22) ) h0 x(n * 23)] (3) By setting the register bit <ODD TAP ENABLE> = 1, a 23-tap FIR is implemented: y(n) + ǒ21 Ǔx[h0 11 x(n) ) h1 x(n * 1) ) h2 x(n * 2) ) AAA ) h10 x(n * 10) ) h11 x(n * 11) ) h10 x(n * 12) ) AAA ) h1 x(n * 21) ) h0 x(n * 22)] (4) In the above equations, h0, h1 …h11 are 12-bit signed representation of the coefficients, x(n) is the input data sequence to the filter y(n) is the filter output sequence Pre-defined Coefficients The in-built filter types (low pass, high pass and band pass) use pre-defined coefficients. The frequency response of the in-built filters is shown in Figure 52 and Figure 53. (1) 48 The digital filter block is bypassed when the SNRBoost mode is enabled. Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 5 0 Magnitude − dB −5 −10 Low Pass High Pass −15 −20 −25 −30 −35 −40 −45 0.0 0.1 0.2 0.3 0.4 0.5 Normalized Frequency − f/fS G025 Figure 52. Decimate by 2 Filter Response 5 0 Magnitude − dB −5 −10 Low Pass High Pass −15 −20 −25 −30 −35 −40 −45 0.0 0.1 0.2 0.3 0.4 0.5 Normalized Frequency − f/fS G026 Figure 53. Decimate by 4 Filter Response 5 0 Magnitude − dB −5 −10 −15 −20 −25 −30 −35 −40 −45 0.0 1st Bandpass 2nd Bandpass 0.1 0.2 0.3 0.4 Normalized Frequency − f/fS 0.5 G027 Figure 54. Decimate by 4 Bandpass Response Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 49 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com Table 28. Predefined Coefficients for Decimation by 2 Filters COEFFICIENTS DECIMATE BY 2 LOW PASS FILTER HIGH PASS FILTER h0 23 -22 h1 -37 -65 h2 -6 -52 h3 68 30 h4 -36 66 h5 -61 -35 h6 35 -107 h7 118 38 h8 -100 202 h9 -197 -41 h10 273 -644 h11 943 1061 Table 29. Predefined Coefficients for Decimation by 4 Filters COEFFICIENTS DECIMATE BY 4 LOW PASS FILTER 1st BAND PASS FILTER 2ND BAND PASS FILTER h0 -17 -7 -34 HIGH PASS FILTER 32 h1 -50 19 -34 -15 h2 71 -47 -101 -95 h3 46 127 43 22 h4 24 73 58 -8 h5 -42 0 -28 -81 h6 -100 86 -5 106 h7 -97 117 -179 -62 h8 8 -190 294 -97 h9 202 -464 86 310 h10 414 -113 -563 -501 h11 554 526 352 575 Custom Filter Coefficients with Decimation The filter coefficients can also be programmed by the user (custom). For custom coefficients, set the register bit (FILTER COEFF SELECT)and load the coefficients (h0 to h11) in registers 1E to 2F using the serial interface (Table 30) as: Register content = 12 bit signed representation of [real coefficient value × 211] 50 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 Custom Filter Coefficients without Decimation The filter with custom coefficients can also be used with the decimation mode disabled. In this mode, the filter implementation is 12-tap FIR: y(n) + ǒ21 Ǔx[h6 11 x(n) ) h7 x(n * 1) ) h8 x(n * 2) ) AAA ) h11 x(n * 5) ) h11 x(n * 6) ) AAA ) h7 x(n * 10) ) h6 x(n * 11)] (5) Table 30. Register Map of Custom Coefficients A7–A0 (hex) D7 D6 D5 1E 1F Coefficient h2 <7:0> Coefficient h2 <11:8> Coefficient h3 <11:4> Coefficient h4 <7:0> Coefficient h5 <3:0> 26 Coefficient h4 <11:8> Coefficient h5 <11:4> 27 Coefficient h6 <7:0> Coefficient h7 <3:0> 29 Coefficient h6 <11:8> Coefficient h7 <11:4> 2A Coefficient h8 <7:0> Coefficient h9 <3:0> 2C Coefficient h8 <11:8> Coefficient h9 <11:4> 2D 2E D0 Coefficient h0 <11:8> Coefficient h3 <3:0> 24 2B D1 Coefficient h1 <11:4> 23 28 D2 Coefficient h0 <7:0> 21 25 D3 Coefficient h1 <3:0> 20 22 D4 Coefficient h10 <7:0> Coefficient h11 <3:0> 2F Coefficient h10 <11:8> Coefficient h11 <11:4> Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 51 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com BOARD DESIGN CONSIDERATIONS Grounding A single ground plane is sufficient to give good performance, provided the analog, digital, and clock sections of the board are cleanly partitioned. See the EVM User Guide (SLAU237) for details on layout and grounding. Supply Decoupling As the ADS62C15 already includes internal decoupling, minimal external decoupling can be used without loss in performance. Note that decoupling capacitors can help filter external power supply noise, so the optimum number of capacitors would depend on the actual application. The decoupling capacitors should be placed very close to the converter supply pins. It is recommended to use separate supplies for the analog and digital supply pins to isolate digital switching noise from sensitive analog circuitry. In case only a single 3.3-V supply is available, it should be routed first to AVDD. It can then be tapped and isolated with a ferrite bead (or inductor) with decoupling capacitor, before being routed to DRVDD. Exposed Thermal Pad It is necessary to solder the exposed pad at the bottom of the package to a ground plane for best thermal performance. For detailed information, see application notes QFN Layout Guidelines (SLOA122) and QFN/SON PCB Attachment (SLUA271). 52 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 DEFINITION OF SPECIFICATIONS Analog Bandwidth – The analog input frequency at which the power of the fundamental is reduced by 3 dB with respect to the low frequency value. Aperture Delay – The delay in time between the rising edge of the input sampling clock and the actual time at which the sampling occurs. This delay will be different across channels. The maximum variation is specified as aperture delay variation (channel-channel). Aperture Uncertainty (Jitter) – The sample-to-sample variation in aperture delay. Clock Pulse Width/Duty Cycle – The duty cycle of a clock signal is the ratio of the time the clock signal remains at a logic high (clock pulse width) to the period of the clock signal. Duty cycle is typically expressed as a percentage. A perfect differential sine-wave clock results in a 50% duty cycle. Maximum Conversion Rate – The maximum sampling rate at which certified operation is given. All parametric testing is performed at this sampling rate unless otherwise noted. Minimum Conversion Rate – The minimum sampling rate at which the ADC functions. Differential Nonlinearity (DNL) – An ideal ADC exhibits code transitions at analog input values spaced exactly 1 LSB apart. The DNL is the deviation of any single step from this ideal value, measured in units of LSBs. Integral Nonlinearity (INL) – The INL is the deviation of the ADC's transfer function from a best fit line determined by a least squares curve fit of that transfer function, measured in units of LSBs. Gain Error – The gain error is the deviation of the ADC's actual input full-scale range from its ideal value. The gain error is given as a percentage of the ideal input full-scale range. The gain error does not include the error caused by the internal reference deviation from ideal value. This is specified separately as internal reference error. The maximum variation of the gain error across devices and across channels within a device is specified separately. Offset Error – The offset error is the difference, given in number of LSBs, between the ADC's actual average idle channel output code and the ideal average idle channel output code. This quantity is often mapped into mV. Temperature Drift – The temperature drift coefficient (with respect to gain error and offset error) specifies the change per degree Celsius of the parameter from TMIN to TMAX. It is calculated by dividing the maximum deviation of the parameter across the TMIN to TMAX range by the difference TMAX–TMIN. Signal-to-Noise Ratio – SNR is the ratio of the power of the fundamental (PS) to the noise floor power (PN), excluding the power at DC and the first nine harmonics. P SNR + 10Log10 S PN (6) SNR is either given in units of dBc (dB to carrier) when the absolute power of the fundamental is used as the reference, or dBFS (dB to full scale) when the power of the fundamental is extrapolated to the converter’s full-scale range. Signal-to-Noise and Distortion (SINAD) – SINAD is the ratio of the power of the fundamental (PS) to the power of all the other spectral components including noise (PN) and distortion (PD), but excluding dc. PS SINAD + 10Log10 PN ) PD (7) SINAD is either given in units of dBc (dB to carrier) when the absolute power of the fundamental is used as the reference, or dBFS (dB to full scale) when the power of the fundamental is extrapolated to the converter's full-scale range. Effective Number of Bits (ENOB) – The ENOB is a measure of a converter’s performance as compared to the theoretical limit based on quantization noise. ENOB + SINAD * 1.76 6.02 (8) Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 53 ADS62C15 SLAS577B – JANUARY 2008 – REVISED MAY 2008 ........................................................................................................................................................ www.ti.com Total Harmonic Distortion (THD) – THD is the ratio of the power of the fundamental (PS) to the power of the first nine harmonics (PD). P THD + 10Log10 S PD (9) THD is typically given in units of dBc (dB to carrier). Spurious-Free Dynamic Range (SFDR) – The ratio of the power of the fundamental to the highest other spectral component (either spur or harmonic). SFDR is typically given in units of dBc (dB to carrier). Two-Tone Intermodulation Distortion – IMD3 is the ratio of the power of the fundamental (at frequencies f1 and f2) to the power of the worst spectral component at either frequency 2f1–f2 or 2f2–f1. IMD3 is either given in units of dBc (dB to carrier) when the absolute power of the fundamental is used as the reference, or dBFS (dB to full scale) when the power of the fundamental is extrapolated to the converter’s full-scale range. DC Power Supply Rejection Ratio (DC PSRR) – The DC PSSR is the ratio of the change in offset error to a change in analog supply voltage. The DC PSRR is typically given in units of mV/V. AC Power Supply Rejection Ratio (AC PSRR) – AC PSRR is the measure of rejection of variations in the supply voltage by the ADC. If ΔVsup is the change in supply voltage and ΔVout is the resultant change of the ADC output code (referred to the input), then PSRR + 20Log10 DVout , expressed in dBc DVsup (10) Voltage Overload Recovery – The number of clock cycles taken to recover to less than 1% error after an overload on the analog inputs. This is tested by separately applying a sine wave signal with 6 dB positive and negative overload. The deviation of the first few samples after the overload (from their expected values) is noted. Common Mode Rejection Ratio (CMRR) – CMRR is the measure of rejection of variation in the analog input common-mode by the ADC. If ΔVcm_in is the change in the common-mode voltage of the input pins and ΔVout is the resultant change of the ADC output code (referred to the input), then CMRR + 20Log10 DVout , expressed in dBc DVcm_in (11) Cross-Talk (Only for Multi-Channel ADC)– This is a measure of the internal coupling of a signal from adjacent channel into the channel of interest. It is specified separately for coupling from the immediate neighboring channel (near-channel) and for coupling from channel across the package (far-channel). It is usually measured by applying a full-scale signal in the adjacent channel. Cross-talk is the ratio of the power of the coupling signal (as measured at the output of the channel of interest) to the power of the signal applied at the adjacent channel input. It is typically expressed in dBc. 54 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 ADS62C15 www.ti.com ........................................................................................................................................................ SLAS577B – JANUARY 2008 – REVISED MAY 2008 Revision History Changes from Original (January 2008) to Revision A .................................................................................................... Page • Changed Figure 3, LVDS Mode Timing............................................................................................................................... 10 Changes from Revision A (February 2008) to Revision B ............................................................................................. Page • • • • • • • • Changed the Functional Block Diagram ................................................................................................................................ 2 Changed Figure 1, Digital Processing Block Diagram........................................................................................................... 3 Changed SNRBoost disabled min values.............................................................................................................................. 7 Added section: Serial Register Readout (only when CMOS interface is used)................................................................... 14 Changed Table 7 ................................................................................................................................................................ 16 Changed DO in Table 8. ...................................................................................................................................................... 17 Changed CMOS Interface, pin 56 From: NC To: SDOUT ................................................................................................... 23 Changed Figure 50, Digital Processing Block Diagram....................................................................................................... 46 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated Product Folder Link(s): ADS62C15 55 PACKAGE OPTION ADDENDUM www.ti.com 21-Apr-2008 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty ADS62C15IRGCR ACTIVE VQFN RGC 64 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-3-260C-168 HR ADS62C15IRGCRG4 ACTIVE VQFN RGC 64 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-3-260C-168 HR ADS62C15IRGCT ACTIVE VQFN RGC 64 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-3-260C-168 HR ADS62C15IRGCTG4 ACTIVE VQFN RGC 64 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-3-260C-168 HR Lead/Ball Finish MSL Peak Temp (3) (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. 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Addendum-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 21-Apr-2008 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel Diameter Width (mm) W1 (mm) A0 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant ADS62C15IRGCR VQFN RGC 64 2500 330.0 16.4 9.3 9.3 1.5 12.0 16.0 Q2 ADS62C15IRGCT VQFN RGC 64 250 330.0 16.4 9.3 9.3 1.5 12.0 16.0 Q2 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 21-Apr-2008 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) ADS62C15IRGCR VQFN RGC 64 2500 333.2 345.9 28.6 ADS62C15IRGCT VQFN RGC 64 250 333.2 345.9 28.6 Pack Materials-Page 2 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. 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