ANALOG DEVICES AD6657

Quad IF Receiver Data Sheet AD6657 FEATURES FUNCTIONAL BLOCK DIAGRAM AVDD AGND DRVDD DRGND 11-bit, 200 MSPS output data rate per channel Integrated noise shaping requantizer (NSR) AD6657 Performance with NSR enabled DC0±AB 14 11 VIN+A SNR: 75.5 dBFS in 40 MHz band to 70 MHz @ 185 MSPS PIPELINE NOISE SHAPING D0±AB ADC REQUANTIZER VIN–A SNR: 73.7 dBFS in 60 MHz band to 70 MHz @ 185 MSPS PORT A VCMA Performance with NSR disabled 14 11 VIN+B NOISE SHAPING PIPELINE D10±AB SNR: 66.5 dBFS to 70 MHz @ 185 MSPS REQUANTIZER ADC VIN–B SFDR: 83 dBc to 70 MHz @ 185 MSPS VCMB DC0±CD Low power: 1.2 W @ 185 MSPS 14 11 VIN+C NOISE SHAPING PIPELINE D0±CD REQUANTIZER 1.8 V analog supply operation ADC VIN–C PORT B 1.8 V LVDS (ANSI-644 levels) output VCMC 14 11 1-to-8 integer clock divider VIN+D NOISE SHAPING PIPELINE D10±CD REQUANTIZER ADC VIN–D Internal ADC voltage reference VCMD 1.75 V p-p analog input range (programmable to 2.0 V p-p) MODE REFERENCE Differential analog inputs with 800 MHz bandwidth CLOCK SYNC DIVIDER 95 dB channel isolation/crosstalk PDWN Serial port control SERIAL PORT User-configurable built-in self-test (BIST) capability Energy-saving power-down modes SCLK SDIO CSB CLK+ CLK– Figure 1. APPLICATIONS Communications PRODUCT HIGHLIGHTS Diversity radio and smart antenna (MIMO) systems 1. Four ADCs are contained in a small, space-saving, Multimode digital receivers (3G) 10 mm × 10 mm × 1.4 mm, 144-ball CSP_BGA package. WCDMA, LTE, CDMA2000 2. Pin selectable noise shaping requantizer (NSR) function WiMAX, TD-SCDMA that allows for improved SNR within a reduced bandwidth I/Q demodulation systems of up to 60 MHz at 185 MSPS. General-purpose software radios 3. LVDS digital output interface configured for low cost FPGA families. 4. 230 mW per ADC core power consumption. 5. Operation from a single 1.8 V supply. 6. Standard serial port interface (SPI) that supports various product features and functions, such as data formatting (offset binary or twos complement), NSR, power-down, test modes, and voltage reference mode. 7. On-chip integer 1-to-8 input clock divider and multichip sync function to support a wide range of clocking schemes and multichannel subsystems. Rev. B Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 www.analog.com license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Fax: 781.461.3113 ©2009–2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. DATA MULTIPLEXER AND LVDS DRIVERS 08557-001 AD6657 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1  Power Dissipation and Standby Mode .................................... 20  Applications....................................................................................... 1  Channel/Chip Synchronization................................................ 20  Functional Block Diagram .............................................................. 1  Digital Outputs ........................................................................... 21  Product Highlights ........................................................................... 1  Timing ......................................................................................... 21  Revision History ............................................................................... 2  Noise Shaping Requantizer (NSR) ............................................... 22  General Description ......................................................................... 3  22% BW Mode (>40 MHz @ 184.32 MSPS)........................... 22  Specifications..................................................................................... 4  33% BW Mode (>60 MHz @ 184.32 MSPS)........................... 22  DC Specifications ......................................................................... 4  MODE Pin................................................................................... 23  AC Specifications.......................................................................... 5  Built-In Self-Test (BIST) and Output Test .................................. 24  Digital Specifications ................................................................... 6  Built-In Self-Test (BIST)............................................................ 24  Switching Specifications .............................................................. 7  Output Test Modes..................................................................... 24  Timing Specifications .................................................................. 8  Serial Port Interface (SPI).............................................................. 25  Absolute Maximum Ratings............................................................ 9  Configuration Using the SPI..................................................... 25  Thermal Characteristics .............................................................. 9  Hardware Interface..................................................................... 25  ESD Caution.................................................................................. 9  Memory Map .................................................................................. 26  Pin Configuration and Function Descriptions........................... 10  Reading the Memory Map Register Table............................... 26  Typical Performance Characteristics ........................................... 12  Memory Map Register Table..................................................... 27  Equivalent Circuits ......................................................................... 15  Memory Map Register Descriptions........................................ 29  Theory of Operation ...................................................................... 16  Applications Information .............................................................. 30  ADC Architecture ...................................................................... 16  Design Guidelines ...................................................................... 30  Analog Input Considerations.................................................... 16  Outline Dimensions....................................................................... 31  Clock Input Considerations...................................................... 18  Ordering Guide .......................................................................... 31  REVISION HISTORY 8/11—Rev. A to Rev. B 7/10—Rev. 0 to Rev. A Changes to Logic Input/Output (SDIO) Parameter Note, Changes to ADC Architecture Section........................................ 16 Table 3 ................................................................................................ 6 Changes to Figure 34 and Figure 35............................................. 18 Added Wake-Up Time (from Standby) Parameter, Table 4 and Changes to Timing Section and Data Clock Output (DCO) Section.............................................................................................. 21 Wake-Up Time (from Power Down) Parameter, Table 4............ 7 Changes to Figure 2.......................................................................... 8 Changes to 22% BW Mode (>40 MHz @ 184.32 MSPS) Section Changes to Table 11........................................................................ 21 and 33% BW Mode (>60 MHz @ 184.32 MSPS) Section ......... 22 Updated Outline Dimensions ....................................................... 31 Changed 0x0C to 0x79, Address 0x01, Table 13......................... 27 Changed DCO Output Delay (Global) to DCO Output Delay (Local), Address 0x17, Table 13.................................................... 28 Changes to Design Guidelines Section........................................ 30 10/09—Revision 0: Initial Version Rev. B | Page 2 of 32 Data Sheet AD6657 GENERAL DESCRIPTION The AD6657 is an 11-bit, 200 MSPS, quad-channel intermediate With the NSR block disabled, the ADC data is provided directly to frequency (IF) receiver specifically designed to support multi- the output with a resolution of 11 bits. The AD6657 can achieve antenna systems in telecommunication applications where high up to 66.5 dBFS SNR for the entire Nyquist bandwidth when dynamic range performance, low power, and small size are desired. operated in this mode. This allows the AD6657 to be used in telecommunication applications such as a digital predistortion The device consists of four high performance analog-to-digital observation path where wider bandwidths are desired. converters (ADCs) and noise shaping requantizer (NSR) digital blocks. Each ADC consists of a multistage, differential pipelined After digital signal processing, multiplexed output data is architecture with integrated output error correction logic. The routed into two 11-bit output ports such that the maximum ADC features a wide bandwidth switched-capacitor sampling data rate is 400 Mbps (DDR). These outputs are set at 1.8 V network within the first stage of the differential pipeline. An LVDS and support ANSI-644 levels. integrated voltage reference eases design considerations. A duty The AD6657 receiver digitizes a wide spectrum of IF frequencies. cycle stabilizer (DCS) compensates for variations in the ADC Each receiver is designed for simultaneous reception of a separate clock duty cycle, allowing the converters to maintain excellent antenna. This IF sampling architecture greatly reduces compo- performance. nent cost and complexity compared with traditional analog Each ADC output is connected internally to an NSR block. The techniques or less integrated digital methods. integrated NSR circuitry allows for improved SNR performance Flexible power-down options allow significant power savings. in a smaller frequency band within the Nyquist bandwidth. The Programming for device setup and control is accomplished device supports two different output modes selectable via the using a 3-wire SPI-compatible serial interface with numerous external MODE pin or the SPI. modes to support board-level system testing. With the NSR feature enabled, the outputs of the ADCs are The AD6657 is available in a Pb-free/RoHS compliant, 144-ball, processed such that the AD6657 supports enhanced SNR 10 mm × 10 mm chip scale package ball grid array (CSP_BGA) performance within a limited portion of the Nyquist bandwidth and is specified over the industrial temperature range of −40°C while maintaining an 11-bit output resolution. The NSR block to +85°C. can be programmed to provide a bandwidth of either 22% or 33% of the sample clock. For example, with a sample clock rate of 185 MSPS, the AD6657 can achieve up to 75.5 dBFS SNR for a 40 MHz bandwidth in the 22% mode and up to 73.7 dBFS SNR for a 60 MHz bandwidth in the 33% mode. Rev. B | Page 3 of 32 AD6657 Data Sheet SPECIFICATIONS DC SPECIFICATIONS AVDD = 1.8 V, DRVDD = 1.8 V, f = 185 MSPS, 1.75 V p-p differential input, VIN = −1.0 dBFS differential input, and default SPI, unless S otherwise noted. Table 1. Parameter Temperature Min Typ Max Unit RESOLUTION Full 11 Bits ACCURACY No Missing Codes Full Guaranteed Offset Error Full −4.5 2 7.4 mV Gain Error Full ±3 ±7 % FSR 1 Differential Nonlinearity (DNL) Full ±0.1 ±0.5 LSB 1 Integral Nonlinearity (INL) Full ±0.2 ±0.5 LSB MATCHING CHARACTERISTIC Offset Error Full −2.4 2.5 8.3 mV Gain Error Full ±1 ±3 % FSR TEMPERATURE DRIFT Offset Error Full 2 ppm/°C Gain Error Full 40 ppm/°C ANALOG INPUT Input Range Full 1.4 1.75 2.0 V p-p Input Common-Mode Voltage Full 0.9 V Input Resistance (Differential) Full 20 kΩ 2 Input Capacitance Full 5 pF POWER SUPPLIES Supply Voltage AVDD Full 1.7 1.8 1.9 V DRVDD Full 1.7 1.8 1.9 V Supply Current 1 IAVDD Full 510 548 mA 1 IDRVDD (1.8 V LVDS) Full 155 169 mA POWER CONSUMPTION 1 Sine Wave Input Full 1195 1290 mW 3 Standby Power Full 130 mW Power-Down Power Full 4.5 18 mW 1 Measured with a 10 MHz, 0 dBFS sine wave, with 100 Ω termination on each LVDS output pair. 2 Input capacitance refers to the effective capacitance between one differential input pin and AGND. 3 Standby power is measured with a dc input and the CLKx pins inactive (set to AVDD or AGND). Rev. B | Page 4 of 32 Data Sheet AD6657 AC SPECIFICATIONS AVDD = 1.8 V, DRVDD = 1.8 V, fS = 185 MSPS, 1.75 V p-p differential input, VIN = −1.0 dBFS differential input, and default SPI, unless otherwise noted. Table 2. 1 Parameter Temperature Min Typ Max Unit SIGNAL-TO-NOISE-RATIO (SNR)—NSR DISABLED fIN = 30 MHz 25°C 66.5 dBFS fIN = 70 MHz 25°C 66.5 dBFS f = 170 MHz Full 65.7 66.1 dBFS IN f = 250 MHz 25°C 65.5 dBFS IN SIGNAL-TO-NOISE-RATIO (SNR)—NSR ENABLED 22% BW Mode f = 70 MHz 25°C 75.5 dBFS IN fIN = 170 MHz Full 72.8 74.4 dBFS fIN = 230 MHz 25°C 72.8 dBFS 33% BW Mode f = 70 MHz 25°C 73.7 dBFS IN f = 170 MHz Full 71.0 72.6 dBFS IN f = 230 MHz 25°C 71.0 dBFS IN SIGNAL-TO-NOISE-AND DISTORTION (SINAD) f = 30 MHz 25°C 65.5 dBFS IN f = 70 MHz 25°C 66.3 dBFS IN fIN = 170 MHz Full 64.1 65.6 dBFS fIN = 250 MHz 25°C 64.3 dBFS EFFECTIVE NUMBER OF BITS (ENOB) fIN = 30 MHz 25°C 10.6 Bits fIN = 70 MHz 25°C 10.7 Bits fIN = 170 MHz Full 10.3 10.6 Bits f = 250 MHz 25°C 10.3 Bits IN WORST SECOND OR THIRD HARMONIC f = 30 MHz 25°C −90 dBc IN f = 70 MHz 25°C −83 dBc IN f = 170 MHz Full −72 −78 dBc IN fIN = 250 MHz 25°C −80 dBc SPURIOUS-FREE DYNAMIC RANGE (SFDR) f = 30 MHz 25°C 90 dBc IN fIN = 70 MHz 25°C 83 dBc fIN = 170 MHz Full 72 78 dBc fIN = 250 MHz 25°C 80 dBc WORST OTHER HARMONIC (FOURTH THROUGH EIGHTH) fIN = 30 MHz 25°C −100 dBc f = 70 MHz 25°C −96 dBc IN f = 170 MHz Full −82 −90 dBc IN f = 250 MHz 25°C −95 dBc IN TWO-TONE SFDR (−7 dBFS) f = 169 MHz, f = 172 MHz 25°C 82 dBc IN1 IN2 2 CROSSTALK Full 95 dB ANALOG INPUT BANDWIDTH 25°C 800 MHz 1 See the AN-835 Application Note, Understanding High Speed ADC Testing and Evaluation, for a complete set of definitions. 2 Crosstalk is measured at 155 MHz with −1 dBFS on one channel and no input on the alternate channel. Rev. B | Page 5 of 32 AD6657 Data Sheet DIGITAL SPECIFICATIONS AVDD = 1.8 V, DRVDD = 1.8 V, fS = 185 MSPS, 1.75 V p-p differential input, VIN = −1.0 dBFS differential input, and default SPI, unless otherwise noted. Table 3. Parameter Temperature Min Typ Max Unit DIFFERENTIAL CLOCK INPUTS (CLK+, CLK−) Logic Compliance CMOS/LVDS/LVPECL Internal Common-Mode Bias Full 0.9 V Differential Input Voltage Full 0.2 3.6 V p-p Input Voltage Range Full AGND − 0.3 AVDD + 0.2 V High Level Input Voltage Full 1.2 2.0 V Low Level Input Voltage Full 0 0.8 V High Level Input Current Full −10 +10 μA Low Level Input Current Full −10 +10 μA Input Resistance Full 8 10 12 kΩ Input Capacitance Full 4 pF SYNC INPUT Logic Compliance CMOS Internal Bias Full 0.9 V Input Voltage Range Full AGND AVDD V High Level Input Voltage Full 1.2 AVDD V Low Level Input Voltage Full AGND 0.6 V High Level Input Current Full −100 +100 μA Low Level Input Current Full −100 +100 μA Input Resistance Full 12 16 20 kΩ Input Capacitance Full 1 pF 1 LOGIC INPUT (CSB) High Level Input Voltage Full 1.22 2.1 V Low Level Input Voltage Full 0 0.6 V High Level Input Current Full −10 +10 μA Low Level Input Current Full 40 132 μA Input Resistance Full 26 kΩ Input Capacitance Full 2 pF 2 LOGIC INPUT (SCLK) High Level Input Voltage Full 1.22 2.1 V Low Level Input Voltage Full 0 0.6 V High Level Input Current Full −92 −135 μA Low Level Input Current Full −10 +10 μA Input Resistance Full 26 kΩ Input Capacitance Full 2 pF 1 LOGIC INPUT/OUTPUT (SDIO) High Level Input Voltage Full 1.22 2.1 V Low Level Input Voltage Full 0 0.6 V High Level Input Current Full −10 +10 μA Low Level Input Current Full 38 128 μA Input Resistance Full 26 kΩ Input Capacitance Full 5 pF Rev. B | Page 6 of 32 Data Sheet AD6657 Parameter Temperature Min Typ Max Unit 1 LOGIC INPUT (MODE) High Level Input Voltage Full 1.22 2.1 V Low Level Input Voltage Full 0 0.6 V High Level Input Current Full −10 +10 μA Low Level Input Current Full 40 132 μA Input Resistance Full 26 kΩ Input Capacitance Full 2 pF 2 LOGIC INPUT (PDWN) High Level Input Voltage Full 1.22 2.1 V Low Level Input Voltage Full 0 0.6 V High Level Input Current Full −90 −134 μA Low Level Input Current Full −10 +10 μA Input Resistance Full 26 kΩ Input Capacitance Full 5 pF DIGITAL OUTPUTS (LVDS) Differential Output Voltage (V) Full 247 454 mV OD Output Offset Voltage (V) Full 1.125 1.375 V OS 1 Pull up. 2 Pull down. SWITCHING SPECIFICATIONS AVDD = 1.8 V, DRVDD = 1.8 V, f = 185 MSPS, 1.75 V p-p differential input, VIN = −1.0 dBFS differential input, and default SPI, unless S otherwise noted. Table 4. Parameter Temperature Min Typ Max Unit CLOCK INPUT PARAMETERS Input Clock Rate Full 625 MHz 1 Conversion Rate Full 40 185 200 MSPS CLK Pulse Width High (tCH) Full 2.7 ns Aperture Delay (tA) Full 1.3 ns Aperture Uncertainty (Jitter, tJ) Full 0.13 ps rms DATA OUTPUT PARAMETERS 4.35 Data Propagation Delay (tPD) Full 3.0 5.7 ns DCO Propagation Delay (tDCO) Full 3.2 4.55 5.9 ns DCO to Data Skew (t) Full −0.4 −0.2 0 ns SKEW Pipeline Delay (Latency) Full 9 Cycles With NSR Enabled Full 12 Cycles 2 Wake-Up Time (from Standby) Full 0.5 μs 2 Wake-Up Time (from Power Down) Full 350 μs OUT-OF-RANGE RECOVERY TIME Full 2 Cycles 1 Conversion rate is the clock rate after the divider. 2 Wake-up time is dependent on the value of the decoupling capacitors. Rev. B | Page 7 of 32 AD6657 Data Sheet TIMING SPECIFICATIONS AVDD = 1.8 V, DRVDD = 1.8 V, fS = 185 MSPS, 1.75 V p-p differential input, VIN = −1.0 dBFS differential input, and default SPI, unless otherwise noted. Table 5. Parameter Description Min Typ Max Unit SYNC TIMING REQUIREMENTS See Figure 3 t SYNC to rising edge of CLK setup time 0.24 ns SSYNC t SYNC to rising edge of CLK hold time 0.40 ns HSYNC SPI TIMING REQUIREMENTS See Figure 2 t Setup time between the data and the rising edge of SCLK 2 ns DS t Hold time between the data and the rising edge of SCLK 2 ns DH t Period of the SCLK 40 ns CLK tS Setup time between CSB and SCLK 2 ns tH Hold time between CSB and SCLK 2 ns t SCLK pulse width high 10 ns HIGH t SCLK pulse width low 10 ns LOW t Time required for the SDIO pin to switch from an input to 10 ns EN_SDIO an output relative to the SCLK falling edge tDIS_SDIO Time required for the SDIO pin to switch from an output to 10 ns an input relative to the SCLK rising edge Timing Diagrams N – 1 t A N + 4 N + 5 N N + 3 VIN N + 1 N + 2 t CH t 1/f CL S CLK– CLK+ t DCO DCO+ DCO– t SKEW t PD D10(MSB)+AB D10A D10B D10A D10B D10A D10B D10A D10B D10A D10B D10A D10B D10A D10B D10(MSB)–AB D0(LSB)+AB D0A D0B D0A D0B D0A D0B D0A D0B D0A D0B D0A D0B D0A D0B D0(LSB)–AB Figure 2. Data Output Timing (Timing for Channel C and Channel D Is Identical to Timing for Channel A and Channel B) CLK+ t t SSYNC HSYNC SYNC Figure 3. SYNC Input Timing Requirements Rev. B | Page 8 of 32 08557-003 08557-002 Data Sheet AD6657 ABSOLUTE MAXIMUM RATINGS THERMAL CHARACTERISTICS Table 6. The values in Table 7 are per JEDEC JESD51-7 plus JEDEC Parameter Rating JESD25-5 for a 2S2P test board. Typical θ is specified for a JA AVDD to AGND −0.3 V to +2.0 V 4-layer PCB with a solid ground plane. As shown in Table 7, DRVDD to AGND −0.3 V to +2.0 V airflow improves heat dissipation, which reduces θJA. In addi- VIN+x, VIN−x to AGND −0.3 V to AVDD + 0.2 V tion, metal in direct contact with the package leads from metal CLK+, CLK− to AGND −0.3 V to AVDD + 0.2 V traces, through holes, ground, and power planes reduces θJA. SYNC to AGND −0.3 V to AVDD + 0.2 V VCMx to AGND −0.3 V to AVDD + 0.2 V Table 7. CSB to AGND −0.3 V to DRVDD + 0.2 V Airflow SCLK to AGND −0.3 V to DRVDD + 0.2 V 1 2 3 Package Type Velocity θ θ θ Unit JA JC JB SDIO to AGND −0.3 V to DRVDD + 0.2 V 144-Ball CSP_BGA, 0 m/s 26.9 8.9 6.6 °C/W PDWN to AGND −0.3 V to DRVDD + 0.2 V 10 mm × 10 mm 1 m/s 24.2 MODE to AGND −0.3 V to DRVDD + 0.2 V (BC-144-1) 2.5 m/s 23.0 Digital Outputs to AGND −0.3 V to DRVDD + 0.2 V 1 Per JEDEC JESD51-2 (still air) or JEDEC JESD51-6 (moving air). DCO+AB, DCO−AB, DCO+CD, −0.3 V to DRVDD + 0.2 V 2 Per MIL-STD 883, Method 1012.1. DCO−CD to AGND 3 Per JEDEC JESD51-8 (still air). Operating Temperature Range −40°C to +85°C (Ambient) The values in Table 8 are from simulations. The PCB is a JEDEC 150°C Maximum Junction Temperature multilayer board. Thermal performance for actual applications Under Bias requires careful inspection of the conditions in the application Storage Temperature Range −65°C to +150°C to determine whether they are similar to those assumed in these (Ambient) calculations. Stresses above those listed under Absolute Maximum Ratings Table 8. may cause permanent damage to the device. This is a stress Airflow rating only; functional operation of the device at these or any Package Type Velocity ΨJB ΨJT Unit other conditions above those indicated in the operational 144-Ball CSP_BGA, 0 m/s 14.4 0.23 °C/W 10 mm × 10 mm section of this specification is not implied. Exposure to absolute 1 m/s 14.0 0.50 (BC-144-1) maximum rating conditions for extended periods may affect 2.5 m/s 13.9 0.53 device reliability. ESD CAUTION Rev. B | Page 9 of 32 AD6657 Data Sheet PIN CONFIGURATION AND FUNCTION DESCRIPTIONS 123 45 6 7 8 9 10 11 12 A AGND VIN+C VIN–C AGND AVDD CLK– CLK+ AVDD AGND VIN–B VIN+B AGND B AGND AGND VCMC AGND AVDD AVDD AVDD AVDD AGND VCMB AGND AGND C VIN+D AGND AGND CSB SDIO SCLK PDWN SYNC MODE AGND AGND VIN+A D VIN–D VCMD AGND AVDD AVDD AVDD AVDD AVDD AVDD AGND VCMA VIN–A E AGND AVDD AVDD AVDD AVDD AVDD AVDD AVDD AVDD AVDD AVDD AGND F AGND AGND AGND AGND AGND AGND AGND AGND AGND AGND AGND AGND G DRGND DRGND DRGND DRGND DRGND DRGND DRGND DRGND DRGND DRGND DRGND DRGND H DRVDD DRVDD DRVDD DRVDD DRVDD DRVDD DRVDD DRVDD DRVDD DRVDD DRVDD DRVDD J D0–CD D2–CD D4–CD D6–CD D8–CD D10–CD D0–AB D2–AB D4–AB D6–AB D8–AB D10–AB K D0+CD D2+CD D4+CD D6+CD D8+CD D10+CD D0+AB D2+AB D4+AB D6+AB D8+AB D10+AB L D1–CD D3–CD D5–CD D7–CD D9–CD DCO–CD D1–AB D3–AB D5–AB D7–AB D9–AB DCO–AB M D1+CD D3+CD D5+CD D7+CD D9+CD DCO+CD D1+AB D3+AB D5+AB D7+AB D9+AB DCO+AB Figure 4. Pin Configuration (Top View) Table 9. Pin Function Descriptions Pin No. Mnemonic Type Description A5, A8, B5, B6, B7, B8, AVDD Supply Analog Power Supply (1.8 V Nominal) D4, D5, D6, D7, D8, D9, E2, E3, E4, E5, E6, E7, E8, E9, E10, E11 A1, A4, A9, A12, B1, AGND Ground Analog Ground B2, B4, B9, B11, B12, C2, C3, C10, C11, D3, D10, E1, E12, F1, F2, F3, F4, F5, F6, F7, F8, F9, F10, F11, F12 H1, H2, H3, H4, H5, DRVDD Supply Digital Output Driver Supply (1.8 V Nominal) H6, H7, H8, H9, H10, H11, H12 G1, G2, G3, G4, G5, DRGND Ground Digital Output Driver Ground G6, G7, G8, G9, G10, G11, G12 A7 CLK+ Input ADC Clock Input—True A6 CLK− Input ADC Clock Input—Complement C12 VIN+A Input Differential Analog Input Pin (+) for Channel A D12 VIN−A Input Differential Analog Input Pin (−) for Channel A D11 VCMA Output Common-Mode Level Bias Output for Analog Input Channel A A11 VIN+B Input Differential Analog Input Pin (+) for Channel B A10 VIN−B Input Differential Analog Input Pin (−) for Channel B B10 VCMB Output Common-Mode Level Bias Output for Analog Input Channel B A2 VIN+C Input Differential Analog Input Pin (+) for Channel C A3 VIN−C Input Differential Analog Input Pin (−) for Channel C B3 VCMC Output Common-Mode Level Bias Output for Analog Input Channel C C1 VIN+D Input Differential Analog Input Pin (+) for Channel D D1 VIN−D Input Differential Analog Input Pin (−) for Channel D D2 VCMD Output Common-Mode Level Bias Output for Analog Input Channel D K7 D0+AB Output Channel A and Channel B LVDS Output Data 0—True J7 D0−AB Output Channel A and Channel B LVDS Output Data 0—Complement Rev. B | Page 10 of 32 05887-004 Data Sheet AD6657 Pin No. Mnemonic Type Description M7 D1+AB Output Channel A and Channel B LVDS Output Data 1—True L7 D1−AB Output Channel A and Channel B LVDS Output Data 1—Complement K8 D2+AB Output Channel A and Channel B LVDS Output Data 2—True J8 D2−AB Output Channel A and Channel B LVDS Output Data 2—Complement M8 D3+AB Output Channel A and Channel B LVDS Output Data 3—True L8 D3−AB Output Channel A and Channel B LVDS Output Data 3—Complement K9 D4+AB Output Channel A and Channel B LVDS Output Data 4—True J9 D4−AB Output Channel A and Channel B LVDS Output Data 4—Complement M9 D5+AB Output Channel A and Channel B LVDS Output Data 5—True L9 D5−AB Output Channel A and Channel B LVDS Output Data 5—Complement K10 D6+AB Output Channel A and Channel B LVDS Output Data 6—True J10 D6−AB Output Channel A and Channel B LVDS Output Data 6—Complement M10 D7+AB Output Channel A and Channel B LVDS Output Data 7—True L10 D7−AB Output Channel A and Channel B LVDS Output Data 7—Complement K11 D8+AB Output Channel A and Channel B LVDS Output Data 8—True J11 D8−AB Output Channel A and Channel B LVDS Output Data 8—Complement M11 D9+AB Output Channel A and Channel B LVDS Output Data 9—True L11 D9−AB Output Channel A and Channel B LVDS Output Data 9—Complement K12 D10+AB Output Channel A and Channel B LVDS Output Data 10—True J12 D10−AB Output Channel A and Channel B LVDS Output Data 10—Complement M12 DCO+AB Output Data Clock LVDS Output for Channel A and Channel B—True L12 DCO−AB Output Data Clock LVDS Output for Channel A and Channel B—Complement K1 D0+CD Output Channel C and Channel D LVDS Output Data 0—True J1 D0−CD Output Channel C and Channel D LVDS Output Data 0—Complement M1 D1+CD Output Channel C and Channel D LVDS Output Data 1—True L1 D1−CD Output Channel C and Channel D LVDS Output Data 1—Complement K2 D2+CD Output Channel C and Channel D LVDS Output Data 2—True J2 D2−CD Output Channel C and Channel D LVDS Output Data 2—Complement M2 D3+CD Output Channel C and Channel D LVDS Output Data 3—True L2 D3−CD Output Channel C and Channel D LVDS Output Data 3—Complement K3 D4+CD Output Channel C and Channel D LVDS Output Data 4—True J3 D4−CD Output Channel C and Channel D LVDS Output Data 4—Complement M3 D5+CD Output Channel C and Channel D LVDS Output Data 5—True L3 D5−CD Output Channel C and Channel D LVDS Output Data 5—Complement K4 D6+CD Output Channel C and Channel D LVDS Output Data 6—True J4 D6−CD Output Channel C and Channel D LVDS Output Data 6—Complement M4 D7+CD Output Channel C and Channel D LVDS Output Data 7—True L4 D7−CD Output Channel C and Channel D LVDS Output Data 7—Complement K5 D8+CD Output Channel C and Channel D LVDS Output Data 8—True J5 D8−CD Output Channel C and Channel D LVDS Output Data 8—Complement M5 D9+CD Output Channel C and Channel D LVDS Output Data 9—True L5 D9−CD Output Channel C and Channel D LVDS Output Data 9—Complement K6 D10+CD Output Channel C and Channel D LVDS Output Data 10—True J6 D10−CD Output Channel C and Channel D LVDS Output Data 10—Complement M6 DCO+CD Output Data Clock LVDS Output for Channel C and Channel D—True L6 DCO−CD Output Data Clock LVDS Output for Channel C and Channel D—Complement C9 MODE Input Mode Select Pin (Logic Low Enables NSR; Logic High Disables NSR) C8 SYNC Input Digital Synchronization Pin C7 PDWN Input Power-Down Input (Active High) C6 SCLK Input SPI Clock C5 SDIO Input/output SPI Data C4 CSB Input SPI Chip Select (Active Low) Rev. B | Page 11 of 32 AD6657 Data Sheet TYPICAL PERFORMANCE CHARACTERISTICS AVDD = 1.8 V, DRVDD = 1.8 V, sample rate = 185 MSPS, 1.75 V p-p differential input, VIN = −1.0 dBFS, 32k sample, TA = 25°C, unless otherwise noted. 0 0 f = 185MSPS f = 185MSPS S S f = 30.3MHz @ –1dBFS f = 200.3MHz @ –1dBFS IN IN –20 SNR = 65.7dB (66.7dBFS) –20 SNR = 64.8dB (65.8dBFS) SFDR = 89.7dBc SFDR = 80dBc –40 –40 –60 –60 SECOND HARMONIC THIRD SECOND HARMONIC –80 –80 HARMONIC THIRD HARMONIC –100 –100 –120 –120 0 10 2030 405060 708090 0 10 2030 405060 708090 FREQUENCY (MHz) FREQUENCY (MHz) Figure 5. Single-Tone FFT with f = 30.3 MHz Figure 8. Single-Tone FFT with f = 200.3 MHz IN IN 0 0 f = 185MSPS f = 185MSPS S S f = 70.3MHz @ –1dBFS f = 230.3MHz @ –1dBFS IN IN –20 SNR = 65.4dB (66.4dBFS) –20 SNR = 64.6dB (65.6dBFS) SFDR = 86dBc SFDR = 86.1dBc –40 –40 –60 –60 THIRD SECOND HARMONIC THIRD HARMONIC SECOND HARMONIC –80 –80 HARMONIC –100 –100 –120 –120 0 10 20 3040 5060708090 0 10 2030 405060 708090 FREQUENCY (MHz) FREQUENCY (MHz) Figure 6. Single-Tone FFT with f = 70.3 MHz Figure 9. Single-Tone FFT with f = 230.3 MHz IN IN 0 0 f = 185MSPS f = 185MSPS S S f = 140.1MHz @ –1.6dBFS IN f = 140.1MHz @ –1dBFS IN NSR 22% BW MODE, TW = 28 –20 –20 SNR = 65.3dB (66.3dBFS) SNR = 73dB (74.6dBFS) (IN-BAND) SFDR = 88dBc SFDR = 89.7dBc (IN-BAND) –40 –40 SECOND –60 HARMONIC –60 THIRD –80 HARMONIC SECOND THIRD –80 HARMONIC HARMONIC –100 –100 –120 –120 –140 0 10 2030 405060 708090 0 10 2030 405060 708090 FREQUENCY (MHz) FREQUENCY (MHz) Figure 7. Single-Tone FFT with f = 140.1 MHz Figure 10. Single-Tone FFT with f = 140.1 MHz, NSR Enabled IN IN in 22% BW Mode with Tuning Word = 28 Rev. B | Page 12 of 32 AMPLITUDE (dBFS) AMPLITUDE (dBFS) AMPLITUDE (dBFS) 08557-007 08557-005 08557-006 AMPLITUDE (dBFS) AMPLITUDE (dBFS) AMPLITUDE (dBFS) 08557-110 08557-109 08557-108 Data Sheet AD6657 0 95 f = 185MSPS S f = 230.3MHz @ –1.6dBFS IN –20 NSR 33% BW MODE, TW = 17 90 SNR = 69.3dB (71dBFS) (IN-BAND) SFDR = 85.4dBc (IN-BAND) –40 85 SFDR (dBc) SECOND HARMONIC –60 80 THIRD –80 75 HARMONIC –100 70 SNR (dBFS) –120 65 –140 60 0 10 20 3040506070 8090 60 110 160 210 260 300 FREQUENCY (MHz) INPUT FREQUENCY (MHz) Figure 11. Single-Tone FFT with f = 230.3 MHz, NSR Enabled Figure 14. Single-Tone SNR/SFDR vs. Input Frequency (f ) IN IN in 33% BW Mode with Tuning Word = 17 with 2.0 V p-p Full Scale 100 95 SFDR (dBc) 90 90 80 85 70 80 60 75 SNR (dBc) 50 SFDR (dBc) 70 SNR (dBFS) 40 SNR (dBFS) SFDR (dBFS) 65 30 60 20 55 10 0 50 30 50 70 90 110 130 150 170 190 210 230 250 SAMPLE RATE (MSPS) INPUT AMPLITUDE (dBFS) Figure 12. Single-Tone SNR/SFDR vs. Input Amplitude (AIN) Figure 15. Single-Tone SNR/SFDR vs. Sample Rate (fS) with fIN = 70.3 MHz with fIN = 70.1 MHz 95 0 f = 185MSPS S f = 169.1MHz @ –7dBFS IN1 90 f = 172.1MHz @ –7dBFS –20 IN2 SFDR = 81.8dBc 85 –40 SFDR (dBc) 80 –60 75 –80 70 SNR (dBFS) –100 65 60 –120 60 110 160 210 260 300 0 10 2030 405060 708090 INPUT FREQUENCY (MHz) FREQUENCY (MHz) Figure 13. Single-Tone SNR/SFDR vs. Input Frequency (fIN) Figure 16. Two-Tone FFT with fIN1 = 169.1 MHz and fIN2 = 172.1 MHz with 1.75 V p-p Full Scale Rev. B | Page 13 of 32 AMPLITUDE (dBFS) SNR/SFDR (dBc AND dBFS) SNR/SFDR (dBFS/dBc) –90 –85 –80 –75 –70 –65 –60 –55 –50 –45 –40 –35 –30 –25 –20 –15 –10 –5 08557-111 0 08557-013 08557-112 SNR/SFDR (dBFS/dBc) SNR/SFDR (dBFS/dBc) AMPLITUDE (dBFS) 08557-015 08557-016 08557-114 AD6657 Data Sheet 0 0.20 0.15 –20 0.10 SFDR (dBc) –40 0.05 IMD3 (dBc) –60 0 –0.05 –80 SFDR (dBFS) –0.10 –100 –0.15 IMD3 (dBFS) –120 –0.20 –90 –78 –66 –54 –42 –30 –18 –6 0 500 1000 1500 2000 INPUT AMPLITUDE (dBFS) OUTPUT CODE Figure 17. Two-Tone SFDR/IMD3 vs. Input Amplitude (A ) Figure 20. DNL with f = 30.3 MHz IN IN with f = 169.1 MHz and f = 172.1 MHz IN1 IN2 1,200,000 69 68 1,000,000 67 800,000 66 65 600,000 64 400,000 63 62 200,000 61 60 0 N – 3 N – 2 N – 1 N N + 1 N + 2 N + 3 30 35 40 45 50 55 60 65 70 OUTPUT CODE DUTY CYCLE (%) Figure 18. Grounded Input Histogram Figure 21. SNR vs. Duty Cycle with fIN = 10.3 MHz 1.0 0.8 0.6 0.4 0.2 0 –0.2 –0.4 –0.6 –0.8 –1.0 0 500 1000 1500 2000 OUTPUT CODE Figure 19. INL with f = 30.3 MHz IN Rev. B | Page 14 of 32 NUMBER OF HITS INL ERROR (LSB) SFDR/IMD3 (dBc AND dBFS) 08557-019 08557-017 08557-018 DNL ERROR (LSB) SNR (dBFS) 08557-021 08557-020 Data Sheet AD6657 EQUIVALENT CIRCUITS AVDD 350Ω SCLK OR 30kΩ PDWN VIN Figure 22. Equivalent Analog Input Circuit Figure 26. Equivalent SCLK and PDWN Input Circuit AVDD AVDD 30kΩ AVDD AVDD 350Ω 0.9V CSB OR 15kΩ 15kΩ MODE CLK+ CLK– Figure 23. Equivalent Clock Input Circuit Figure 27. Equivalent CSB and MODE Input Circuit DRVDD DRVDD V+ V– DATAOUT– DATAOUT+ 350Ω SDIO V– V+ 30kΩ Figure 24. Equivalent LVDS Output Circuit Figure 28. Equivalent SDIO Circuit AVDD AVDD SYNC 0.9V 16kΩ 0.9V Figure 25. Equivalent SYNC Input Circuit Rev. B | Page 15 of 32 08557-008 08557-025 08557-010 08557-009 08557-011 08557-014 08557-012 AD6657 Data Sheet THEORY OF OPERATION A small resistor in series with each input can help reduce the ADC ARCHITECTURE peak transient current required from the output stage of the The AD6657 architecture consists of quad front-end sample- driving source. A shunt capacitor can be placed across the and-hold circuits, followed by pipelined, switched-capacitor inputs to provide dynamic charging currents. This passive ADCs. The quantized outputs from each stage are combined network creates a low-pass filter at the ADC input; therefore, into a final 14-bit result in the digital correction logic. Alter- the precise values are dependent on the application. nately, the 14-bit result can be processed through the noise In intermediate frequency (IF) undersampling applications, shaping requantizer (NSR) block before it is sent to the digital any shunt capacitors should be reduced. In combination with correction logic. the driving source impedance, the shunt capacitors limit the The pipelined architecture permits the first stage to operate on input bandwidth. For more information on this subject, see a new input sample and the remaining stages to operate on the Application Note AN-742, Frequency Domain Response of preceding samples. Sampling occurs on the rising edge of the clock. Switched-Capacitor ADCs; Application Note AN-827, A Resonant Each stage of the pipeline, excluding the last, consists of a low Approach to Interfacing Amplifiers to Switched-Capacitor ADCs; resolution flash ADC connected to a switched-capacitor digital- and the Analog Dialogue article, “Transformer-Coupled Front-End to-analog converter (DAC) and an interstage residue amplifier for Wideband A/D Converters” (see www.analog.com). (MDAC). The residue amplifier magnifies the difference between BIAS the reconstructed DAC output and the flash input for the next S S stage in the pipeline. One bit of redundancy is used in each stage C C S FB to facilitate digital correction of flash errors. The last stage VIN+ C C simply consists of a flash ADC. PAR1 PAR2 The input stage of each channel contains a differential sampling H S S circuit that can be ac- or dc-coupled in differential or single- C S ended modes. The output staging block aligns the data, corrects VIN– errors, and passes the data to the output buffers. The output C C C FB PAR1 PAR2 S buffers are powered from a separate supply, allowing adjust- S BIAS ment of the output drive current. During power-down, the Figure 29. Switched-Capacitor Input output buffers go into a high impedance state. For best dynamic performance, the source impedances driving The AD6657 quad IF receiver can simultaneously digitize four the VIN+ and VIN− pins should be matched. channels, making it ideal for diversity reception and digital pre- distortion (DPD) observation paths in telecommunication An internal differential reference buffer creates positive and systems. negative reference voltages that define the input span of the ADC core. The span of the ADC core is set by this buffer to 2 × VREF. Synchronization capability is provided to allow synchronized timing between multiple channels or multiple devices. Input Common Mode Programming and control of the AD6657 are accomplished The analog inputs of the AD6657 are not internally dc biased. using a 3-wire SPI-compatible serial interface. In ac-coupled applications, the user must provide this bias externally. An on-board common-mode voltage reference is ANALOG INPUT CONSIDERATIONS included in the design and is available from the VCMx pins. The analog input to the AD6657 is a differential switched- Optimum performance is achieved when the common-mode capacitor circuit that has been designed for optimum voltage of the analog input is set by the VCMx pin voltage performance while processing a differential input signal. (typically 0.5 × AVDD). The VCMx pins must be decoupled The clock signal alternatively switches the input between sample to ground by a 0.1 μF capacitor. mode and hold mode (see Figure 29). When the input is switched to sample mode, the signal source must be capable of charging the sample capacitors and settling within 1/2 of a clock cycle. Rev. B | Page 16 of 32 08557-037 Data Sheet AD6657 Differential Input Configurations The signal characteristics must be considered when selecting a transformer. Most RF transformers saturate at frequencies Optimum performance is achieved when driving the AD6657 below a few megahertz (MHz). Excessive signal power can also in a differential input configuration. For baseband applications, cause core saturation, which leads to distortion. the AD8138, ADA4937-2, and ADA4938-2 differential drivers provide excellent performance and a flexible interface to the ADC. At input frequencies in the second Nyquist zone and above, the noise performance of most amplifiers is not adequate to achieve The output common-mode voltage of the ADA4938-2 is easily the true SNR performance of the AD6657. For applications in set with the VCMx pin of the AD6657 (see Figure 30), and the which SNR is a key parameter, differential double balun coupling driver can be configured in a Sallen-Key filter topology to is the recommended input configuration (see Figure 32). In this provide band limiting of the input signal. configuration, the input is ac-coupled and the CML is provided to 15pF each input through a 33 Ω resistor. These resistors compensate 200Ω for losses in the input baluns to provide a 50 Ω impedance to 33Ω 15Ω 90Ω VIN– AVDD 76.8Ω the driver. VIN 5pF ADC In the double balun and transformer configurations, the value ADA4938-2 0.1µF of the input capacitors and resistors is dependent on the input 33Ω 15Ω VCM VIN+ 120Ω frequency and source impedance and may need to be reduced 15pF or removed. Table 10 lists recommended values to set the RC 200Ω network. At higher input frequencies, good performance can be Figure 30. Differential Input Configuration Using the ADA4938-2 achieved by using a ferrite bead in series with a resistor and For baseband applications where SNR is a key parameter, removing the capacitors. However, these values are dependent differential transformer coupling is the recommended input on the input signal and should be used only as a starting guide. configuration. An example is shown in Figure 31. To bias the Table 10. Example RC Network analog input, the VCM voltage can be connected to the center Frequency tap of the secondary winding of the transformer. Range R1 Series R2 Series C2 Shunt C2 (MHz) (Each) C1 Differential (Each) (Each) R2 0 to 100 33 Ω 5 pF 15 Ω 15 pF VIN+ R1 100 to 200 10 Ω 5 pF 10 Ω 10 pF 2V p-p 49.9Ω 1 C1 ADC 100 to 300 10 Ω Remove 66 Ω Remove R1 R2 1 In this configuration, R1 is a ferrite bead with a value of 10 Ω @ 100 MHz. VCM VIN– An alternative to using a transformer-coupled input at frequencies 0.1µF C2 in the second Nyquist zone is to use the AD8352 differential driver (see Figure 33). For more information, see the AD8352 data sheet. Figure 31. Differential Transformer-Coupled Configuration C2 0.1µF 0.1µF R1 R2 VIN+ 2V p-p 33Ω P S S P C1 ADC A 0.1µF 33Ω 0.1µF R1 R2 VCM VIN– C2 Figure 32. Differential Double Balun Input Configuration V CC 0.1µF 0.1µF 0Ω 16 8, 13 ANALOG INPUT 0.1µF R 11 VIN+ 1 200Ω 2 C C R R ADC D D G AD8352 3 200Ω 0.1µF 10 4 R VIN– VCM 5 14 ANALOG INPUT 0Ω 0.1µF 0.1µF 0.1µF Figure 33. Differential Input Configuration Using the AD8352 Rev. B | Page 17 of 32 08557-040 08557-039 08557-041 08557-042 AD6657 Data Sheet ANALOG XFMR 1:4 Z INPUT ETC4-1T-7 33Ω 0.1µF 0.1µF 121Ω 431nH 0.1µF INPUT 3.0kΩ 3.0pF 121Ω ADC Z = 50Ω 0.1µF INTERNAL INPUT Z AIN– 0.1µF 33Ω VCM Figure 34. 1:4 Transformer Passive Configuration 1000pF 180nH 220nH 1µH 165Ω VPOS 15pF AD8376 5.1pF 3.9pF 301Ω VCM 3.0kΩ║3.0pF 165Ω 1nF 1µH 1nF 68nH AD6657 180nH 220nH 1000pF NOTES 1. ALL INDUCTORS ARE COILCRAFT 0603CS COMPONENTS WITH THE EXCEPTION OF THE 1µH CHOKE INDUCTORS (0603LS). Figure 35. Active Front-End Configuration Using the AD8376 Figure 37 and Figure 38 show two preferred methods for clock- For the popular IF band of 140 MHz, Figure 34 shows an ing the AD6657 (at clock rates up to 625 MHz). A low jitter clock example of a 1:4 transformer passive configuration where a source is converted from a single-ended signal to a differential differential inductor is used to resonate with the internal input signal using either an RF balun or an RF transformer. capacitance of the AD6657. This configuration realizes excellent noise and distortion performance. Figure 35 shows an example The RF balun configuration is recommended for clock frequencies of an active front-end configuration using the AD8376 dual between 125 MHz and 625 MHz, and the RF transformer config- VGA. This configuration is recommended when signal gain uration is recommended for clock frequencies from 10 MHz to is required. 200 MHz. The back-to-back Schottky diodes across the trans- former/balun secondary limit clock excursions into the AD6657 CLOCK INPUT CONSIDERATIONS to approximately 0.8 V p-p differential. For optimum performance, the AD6657 sample clock inputs, This limit helps to prevent the large voltage swings of the clock CLK+ and CLK−, should be clocked with a differential signal. from feeding through to other portions of the AD6657 while The signal is typically ac-coupled into the CLK+ and CLK− pins preserving the fast rise and fall times of the signal that are via a transformer or capacitors. These pins are biased internally critical to a low jitter performance. (see Figure 36) and require no external bias. AVDD ADT1-1WT, 1:1Z 0.1µF 0.1µF XFMR 1.2V CLOCK CLK+ INPUT 100Ω 50Ω ADC CLK+ CLK– 0.1µF CLK– SCHOTTKY 2pF 2pF 0.1µF DIODES: HSMS2822 Figure 37. Transformer-Coupled Differential Clock (Up to 200 MHz) Figure 36. Equivalent Clock Input Circuit Clock Input Options 1nF 0.1µF CLOCK The AD6657 has a very flexible clock input structure. The clock CLK+ INPUT 50Ω ADC input can be a CMOS, LVDS, LVPECL, or sine wave signal. 0.1µF 1nF CLK– Regardless of the type of signal being used, clock source jitter is SCHOTTKY of the most concern (see the Jitter Considerations section). DIODES: HSMS2822 Figure 38. Balun-Coupled Differential Clock (Up to 625 MHz) Rev. B | Page 18 of 32 08557-055 08557-115 08557-116 08557-057 08557-056 Data Sheet AD6657 If a low jitter clock source is not available, another option is to V CC ac-couple a differential PECL signal to the sample clock input OPTIONAL 0.1µF 0.1µF 1kΩ AD951x 100Ω pins, as shown in Figure 39. The AD9510/AD9511/AD9512/ CLOCK CLK+ CMOS DRIVER INPUT 1 50Ω 1kΩ AD9513/AD9514/AD9515/AD9516 clock drivers offer excellent ADC jitter performance. 0.1µF CLK– 1 50Ω RESISTOR IS OPTIONAL. 0.1µF 0.1µF CLOCK Figure 42. Single-Ended 3.3 V CMOS Input Clock (Up to 200 MHz) CLK+ INPUT AD951x 100Ω ADC Input Clock Divider PECL DRIVER 0.1µF 0.1µF CLOCK CLK– The AD6657 contains an input clock divider with the ability to INPUT 240Ω 240Ω 50kΩ 50kΩ divide the input clock by integer values from 1 to 8. The AD6657 clock divider can be synchronized using the Figure 39. Differential PECL Sample Clock (Up to 625 MHz) external SYNC input. Bit 1 of Register 0x3A enables the clock A third option is to ac-couple a differential LVDS signal to the divider to be resynchronized on every SYNC signal. A valid sample clock input pins, as shown in Figure 40. The AD9510/ SYNC causes the clock divider to reset to its initial state. This AD9511/AD9512/AD9513/AD9514/AD9515/AD9516 clock synchronization feature allows multiple parts to have their clock drivers offer excellent jitter performance. dividers aligned to guarantee simultaneous input sampling. Clock Duty Cycle 0.1µF 0.1µF Typical high speed ADCs use both clock edges to generate CLOCK CLK+ INPUT a variety of internal timing signals and, as a result, may be AD951x 100Ω ADC LVDS DRIVER sensitive to clock duty cycle. Commonly, a ±5% tolerance is 0.1µF 0.1µF CLOCK CLK– required on the clock duty cycle to maintain dynamic INPUT 50kΩ 50kΩ performance characteristics. The AD6657 contains a duty cycle stabilizer (DCS) that retimes Figure 40. Differential LVDS Sample Clock (Up to 625 MHz) the nonsampling (falling) edge, providing an internal clock signal In some applications, it may be acceptable to drive the sample with a nominal 50% duty cycle. This allows the user to provide a clock inputs with a single-ended CMOS signal. In such applica- wide range of clock input duty cycles without affecting the per- tions, the CLK+ pin should be driven directly from a CMOS formance of the AD6657. Noise and distortion performance are gate, and the CLK− pin should be bypassed to ground with a nearly flat for a wide range of duty cycles with the DCS enabled. 0.1 μF capacitor in parallel with a 39 kΩ resistor (see Figure 41). Jitter in the rising edge of the input is still of paramount concern and is not easily reduced by the internal stabilization circuit. The V CC OPTIONAL 0.1µF duty cycle control loop does not function for clock rates less 0.1µF 1kΩ AD951x 100Ω CLOCK CLK+ CMOS DRIVER than 40 MHz nominally. The loop has a time constant asso- INPUT 1 1kΩ 50Ω ADC ciated with it that must be considered in applications in which the clock rate can change dynamically. A wait time of 1.5 μs to CLK– 5 μs is required after a dynamic clock frequency increase or 0.1µF 39kΩ decrease before the DCS loop is relocked to the input signal. 1 50Ω RESISTOR IS OPTIONAL. During the time period that the loop is not locked, the DCS Figure 41. Single-Ended 1.8 V CMOS Input Clock (Up to 200 MHz) loop is bypassed, and internal device timing is dependent on the duty cycle of the input clock signal. CLK+ can be driven directly from a CMOS gate. Although the CLK+ input circuit supply is AVDD (1.8 V), this input is designed to withstand input voltages of up to 3.6 V, making the selection of the drive logic voltage very flexible (see Figure 42). Rev. B | Page 19 of 32 08557-060 08557-059 08557-058 08557-061 AD6657 Data Sheet 1.5 0.60 Jitter Considerations 1.4 0.55 1.3 High speed, high resolution ADCs are sensitive to the quality of I 0.50 AVDD 1.2 the clock input. The degradation in SNR from the low frequency 0.45 1.1 SNR (SNRLF) at a given input frequency (fIN) due to jitter (tJRMS) 1.0 0.40 TOTAL POWER can be calculated by 0.9 0.35 0.8 2 (−SNR /10) LF SNR = −10log[(2π × f × t ) + 10 ] 0.30 HF IN JRMS 0.7 0.25 0.6 In the equation, the rms aperture jitter represents the clock 0.5 0.20 input jitter specification. IF undersampling applications are 0.4 0.15 I DRVDD particularly sensitive to jitter, as illustrated in Figure 43. 0.3 0.10 0.2 80 0.05 0.1 0 0 0.05ps 75 SAMPLING FREQUENCY (MSPS) 70 Figure 44. Power and Current vs. Sampling Frequency 0.20ps By asserting PDWN (either through the SPI port or by asserting 65 the PDWN pin high), the AD6657 is placed in power-down mode. In this state, the ADC typically dissipates 4.5 mW. 0.50ps 60 During power-down, the output drivers are placed in a high impedance state. Asserting the PDWN pin low returns the 55 1.00ps AD6657 to its normal operating mode. Note that PDWN is 1.50ps referenced to the digital output driver supply (DRVDD) and 50 1 10 100 1k should not exceed that supply voltage. INPUT FREQUENCY (MHz) Low power dissipation in power-down mode is achieved by Figure 43. SNR vs. Input Frequency and Jitter shutting down the reference, reference buffer, biasing networks, The clock input should be treated as an analog signal in cases and clock. Internal capacitors are discharged when entering in which aperture jitter may affect the dynamic range of the power-down mode and must be recharged when returning to AD6657. Power supplies for clock drivers should be separated normal operation. As a result, wake-up time is related to the from the ADC output driver supplies to avoid modulating the time spent in power-down mode; shorter power-down cycles clock signal with digital noise. Low jitter, crystal-controlled result in proportionally shorter wake-up times. oscillators make the best clock sources. If the clock is generated When using the SPI port interface, the user can place the ADC from another type of source (by gating, dividing, or another in power-down mode or standby mode. Standby mode allows method), it should be retimed by the original clock at the last the user to keep the internal reference circuitry powered when step. Refer to Application Note AN-501 and Application Note faster wake-up times are required. See the Memory Map AN-756 for more information about jitter performance as it Register Descriptions section for more details. relates to ADCs (see www.analog.com). CHANNEL/CHIP SYNCHRONIZATION POWER DISSIPATION AND STANDBY MODE The AD6657 has a SYNC input that offers the user flexible syn- The power dissipated by the AD6657 is proportional to its clock chronization options for synchronizing the clock divider. The rate (see Figure 44). The digital power dissipation does not vary clock divider sync feature is useful for guaranteeing synchronized significantly because it is determined primarily by the DRVDD sample clocks across multiple ADCs. supply and the bias current of the LVDS drivers. The SYNC input is internally synchronized to the sample clock; Reducing the capacitive load presented to the output drivers can however, to ensure that there is no timing uncertainty between minimize digital power consumption. The data in Figure 44 was multiple parts, the SYNC input signal should be externally syn- taken using the same operating conditions as those used in the chronized to the input clock signal, meeting the setup and hold Typical Performance Characteristics section, with a 5 pF load times shown in Table 5. The SYNC input should be driven using on each output driver. a single-ended CMOS-type signal. Rev. B | Page 20 of 32 SNR (dBc) 08557-053 TOTAL POWER (W) 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 CURRENT (A) 08557-142 Data Sheet AD6657 The length of the output data lines and the loads placed on DIGITAL OUTPUTS them should be minimized to reduce transients within the The AD6657 output drivers are configured to interface with AD6657. These transients can degrade converter dynamic LVDS outputs using a DRVDD supply voltage of 1.8 V. The performance. output bits are DDR LVDS as shown in Figure 2. Applications that require the ADC to drive large capacitive loads or large The lowest typical conversion rate of the AD6657 is 40 MSPS. fanouts may require external buffers or latches. At clock rates below 40 MSPS, dynamic performance can degrade. As described in Application Note AN-877, Interfacing to High Data Clock Output (DCO) Speed ADCs via SPI, the data format can be selected for offset The AD6657 provides a data clock output (DCO) signal intended binary or twos complement when using the SPI control. for capturing the data in an external register. The output data for Channel A and Channel C is valid when DCO is high; the TIMING output data for Channel B and Channel D is valid when DCO is The AD6657 provides latched data with a latency of nine clock low. See Figure 2 for a graphical timing description. cycles. Data outputs are available one propagation delay (tPD) after the rising edge of the clock signal. Table 11. Output Data Format Input (V) Condition (V) Offset Binary Output Mode Twos Complement Mode VIN+ − VIN− < −V − 0.5 LSB 000 0000 0000 100 0000 0000 REF VIN+ − VIN− = −VREF 000 0000 0000 100 0000 0000 VIN+ − VIN− = 0 100 0000 0000 000 0000 0000 VIN+ − VIN− = +VREF − 1.0 LSB 111 1111 1111 011 1111 1111 VIN+ − VIN− > +V − 0.5 LSB 111 1111 1111 011 1111 1111 REF Rev. B | Page 21 of 32 AD6657 Data Sheet NOISE SHAPING REQUANTIZER (NSR) 0 The AD6657 features a noise shaping requantizer (NSR) to f = 184.32MSPS S f = 140MHz @ –1.6dBFS IN allow higher than 11-bit SNR to be maintained in a subset of NSR 22% BW MODE, TW = 28 –20 SNR = 73.4dB (75dBFS) (IN-BAND) the Nyquist band. The harmonic performance of the receiver SFDR = 93dBc (IN-BAND) is unaffected by the NSR feature. When enabled, the NSR –40 contributes an additional 0.6 dB of loss to the input signal, such that a 0 dBFS input is reduced to −0.6 dBFS at the output pins. –60 The NSR feature can be independently controlled per channel via the SPI or the MODE pin. –80 Two different bandwidth modes are provided; the mode can be –100 selected from the SPI port. In each of the two modes, the center frequency of the band can be tuned such that IFs can be placed –120 anywhere in the Nyquist band. 02 100 3040 5060 70 8090 FREQUENCY (MHz) 22% BW MODE (>40 MHZ @ 184.32 MSPS) Figure 46. 22% BW Mode, Tuning Word = 28 (f /4 Tuning) S The first bandwidth mode offers excellent noise performance 0 over 22% of the ADC sample rate (44% of the Nyquist band) f = 184.32MSPS S f = 140MHz @ –1.6dBFS IN and can be centered by setting the NSR mode bits in the NSR NSR 22% BW MODE, TW = 41 –20 SNR = 73.4dB (75dBFS) (IN-BAND) control register (Address 0x3C) to 000. In this mode, the useful SFDR = 94dBc (IN-BAND) frequency range can be set using the 6-bit tuning word in the –40 NSR tuning register (Address 0x3E). There are 57 possible tuning words (TW); each step is 0.5% of the ADC sample rate. –60 The following three equations describe the left band edge (f0), the channel center (fCENTER), and the right band edge (f1), –80 respectively. f = f × .005 × TW 0 ADC –100 f = f + 0.11 × f CENTER 0 ADC –120 02 100 3040 5060 70 8090 f = f + 0.22 × f 1 0 ADC FREQUENCY (MHz) Figure 45 to Figure 47 show the typical spectrum that can be Figure 47. 22% BW Mode, Tuning Word = 41 expected from the AD6657 in the 22% BW mode for three 33% BW MODE (>60 MHZ @ 184.32 MSPS) different tuning words. 0 The second bandwidth mode offers excellent noise performance f = 184.32MSPS S over 33% of the ADC sample rate (66% of the Nyquist band) f = 140MHz @ –1.6dBFS IN NSR 22% BW MODE, TW = 13 –20 and can be centered by setting the NSR mode bits in the NSR SNR = 73.4dB (75dBFS) (IN-BAND) SFDR = 92.6dBc (IN-BAND) control register (Address 0x3C) to 001. In this mode, the useful –40 frequency range can be set using the 6-bit tuning word in the NSR tuning register (Address 0x3E). There are 34 possible –60 tuning words (TW); each step is 0.5% of the ADC sample rate. The following three equations describe the left band edge (f ), 0 –80 the channel center (f ), and the right band edge (f ), CENTER 1 respectively. –100 f = f × .005 × TW 0 ADC fCENTER = f0 + 0.165 × fADC –120 02 100 3040 5060 70 8090 FREQUENCY (MHz) f1 = f0 + 0.33 × fADC Figure 45. 22% BW Mode, Tuning Word = 13 Rev. B | Page 22 of 32 AMPLITUDE (dBFS) 08557-044 AMPLITUDE (dBFS) AMPLITUDE (dBFS) 08557-046 08557-045 Data Sheet AD6657 0 Figure 48 to Figure 50 show the typical spectrum that can be f = 184.32MSPS S expected from the AD6657 in the 33% BW mode for three f = 140MHz @ –1.6dBFS IN NSR 33% BW MODE, TW = 27 –20 different tuning words. SNR = 71dB (72.5dBFS) (IN-BAND) SFDR = 93dBc (IN-BAND) 0 f = 184.32MSPS –40 S f = 140MHz @ –1.6dBFS IN NSR 33% BW MODE, TW = 5 –20 SNR = 71dB (72.5dBFS) (IN-BAND) –60 SFDR = 92.5dBc (IN-BAND) –40 –80 –60 –100 –80 –120 02 100 3040 5060 70 8090 FREQUENCY (MHz) –100 Figure 50. 33% BW Mode, Tuning Word = 27 –120 02 100 3040 5060 70 8090 MODE PIN FREQUENCY (MHz) The MODE pin input allows convenient control of the NSR Figure 48. 33% BW Mode, Tuning Word = 5 feature. A logic low enables NSR mode and a logic high sets the 0 receiver to straight 11-bit mode with NSR disabled. By default, f = 184.32MSPS S f = 140MHz @ –1.6dBFS IN the MODE pin is pulled high internally to disable the NSR. NSR 33% BW MODE, TW = 17 –20 SNR = 71.2dB (72.8dBFS) (IN-BAND) Each channel can be individually configured to ignore the SFDR = 93.7dBc (IN-BAND) MODE pin state by writing to Bit 4 of the NSR control register –40 at Address 0x3C. Use of the NSR control register in conjunction with the MODE pin allows for very flexible control of the NSR –60 feature on a per-channel basis. –80 –100 –120 02 100 3040 5060 70 8090 FREQUENCY (MHz) Figure 49. 33% BW Mode, Tuning Word = 17 (fS/4 Tuning) Rev. B | Page 23 of 32 AMPLITUDE (dBFS) AMPLITUDE (dBFS) 08557-048 08557-047 AMPLITUDE (dBFS) 08557-049 AD6657 Data Sheet BUILT-IN SELF-TEST (BIST) AND OUTPUT TEST The AD6657 includes built-in test features designed to verify The outputs are not disconnected during this test, so the PN the integrity of each channel and to facilitate board-level debug- sequence can be observed as it runs. The PN sequence can be ging. A BIST (built-in self-test) feature is included that verifies continued from its last value or reset from the beginning, based the integrity of the digital datapath of the AD6657. Various on the value programmed in Register 0x0E, Bit 2. The BIST output test options are also provided to place predictable values signature result varies based on the channel configuration. on the outputs of the AD6657. OUTPUT TEST MODES BUILT-IN SELF-TEST (BIST) The output test options are shown in Table 13. When an output The BIST is a thorough test of the digital portion of the selected test mode is enabled, the analog section of the receiver is dis- AD6657 signal path. When enabled, the test runs from an internal connected from the digital back-end blocks, and the test pattern pseudorandom noise (PN) source through the digital datapath is run through the output formatting block. Some of the test starting at the ADC block output. The BIST sequence runs for patterns are subject to output formatting. The seed value for the 512 cycles and stops. The BIST signature value for the selected PN sequence tests can be forced if the PN reset bits are used to channel is written to Register 0x24 and Register 0x25. hold the generator in reset mode by setting Bit 4 or Bit 5 of Register 0x0D. These tests can be performed with or without an If more than one channel is BIST-enabled, the channel that analog signal (if present, the analog signal is ignored), but they is first according to alphabetical order is written to the BIST require an encode clock. For more information, see Application signature registers. For example, if Channel B and Channel C Note AN-877, Interfacing to High Speed ADCs via SPI. are BIST-enabled, the results from Channel B are written to the BIST signature registers. Rev. B | Page 24 of 32 Data Sheet AD6657 SERIAL PORT INTERFACE (SPI) The AD6657 serial port interface (SPI) allows the user to con- During an instruction phase, a 16-bit instruction is transmitted. figure the receiver for specific functions or operations through a The first bit of the first byte in a serial data transfer frame indicates structured internal register space. The SPI provides added flexibility whether a read command or a write command is issued. Data and customization, depending on the application. Addresses are follows the instruction phase, and its length is determined by accessed via the serial port and can be written to or read from the W0 and W1 bits. All data is composed of 8-bit words. via the port. Memory is organized into bytes that can be further The instruction phase determines whether the serial frame is a divided into fields, which are documented in the Memory Map read or write operation, allowing the serial port to be used both section. For detailed operational information, see Application to program the chip and to read the contents of the on-chip Note AN-877, Interfacing to High Speed ADCs via SPI. memory. If the instruction is a read operation, the serial data input/output (SDIO) pin changes direction from an input to an CONFIGURATION USING THE SPI output at the appropriate point in the serial frame. Three pins define the SPI of the AD6657: SCLK, SDIO, and CSB Data can be sent in MSB first mode or in LSB first mode. (see Table 12). SCLK (a serial clock) is used to synchronize the MSB first is the default mode on power-up and can be changed read and write data presented from and to the AD6657. SDIO via the SPI port configuration register. For more information (serial data input/output) is a bidirectional pin that allows data about this and other features, see Application Note AN-877, to be sent to and read from the internal memory map registers. Interfacing to High Speed ADCs via SPI. CSB (chip select bar) is an active low control that enables or disables the read and write cycles. HARDWARE INTERFACE Table 12. Serial Port Interface Pins The pins described in Table 12 constitute the physical interface between the user programming device and the serial port of the Pin Function AD6657. The SCLK pin and the CSB pin function as inputs SCLK Serial clock. Serial shift clock input. SCLK is used to synchronize serial interface reads and writes. when using the SPI interface. The SDIO pin is bidirectional, SDIO Serial data input/output. Bidirectional pin that serves functioning as an input during the write phase and as an output as an input or an output, depending on the instruction during readback. being sent and the relative position in the timing frame. The SPI interface is flexible enough to be controlled by either CSB Chip select bar (active low). This control gates the read FPGAs or microcontrollers. One method for SPI configuration and write cycles. is described in detail in Application Note AN-812, Micro- The falling edge of the CSB pin, in conjunction with the rising controller-Based Serial Port Interface (SPI) Boot Circuit. edge of the SCLK pin, determines the start of the framing. An The SPI port should not be active during periods when the full example of the serial timing can be found in Figure 51 (for dynamic performance of the AD6657 is required. Because the symbol definitions, see Table 5). SCLK signal, the CSB signal, and the SDIO signal are typically CSB can be held low indefinitely, which permanently enables asynchronous to the ADC clock, noise from these signals can the device; this is called streaming. CSB can stall high between degrade AD6657 performance. If the on-board SPI bus is used bytes to allow for additional external timing. When CSB is tied for other devices, it may be necessary to provide buffers between high, SPI functions are placed in high impedance mode. this bus and the AD6657 to prevent these signals from transi- tioning at the receiver inputs during critical sampling periods. t t t t DS HIGH CLK H t t S DH t LOW CSB DON’T SCLK DON’T CARE CARE DON’T SDIO R/W W1 W0 A12 A11 A10 A9A8 A7 D5 D4 D3D2D1 D0 DON’T CARE CARE Figure 51. Serial Port Interface Timing Diagram Rev. B | Page 25 of 32 08557-073 AD6657 Data Sheet MEMORY MAP Logic Levels READING THE MEMORY MAP REGISTER TABLE An explanation of logic level terminology follows: Each row in the memory map register table has eight bit loca- tions (see Table 13). The memory map is roughly divided into • “Bit is set” is synonymous with “bit is set to Logic 1” or four sections: the chip configuration registers (Address 0x00 “writing Logic 1 for the bit.” and Address 0x01); the channel index and transfer registers • “Clear a bit” is synonymous with “bit is set to Logic 0” or (Address 0x05 and Address 0xFF); the ADC function registers, “writing Logic 0 for the bit.” including setup, control, and test (Address 0x08 to Address 0x25); Transfer Register Map and the digital feature control registers (Address 0x3A to Address 0x3E). Address 0x08 to Address 0x3E are shadowed. Writes to these addresses do not affect part operation until a transfer command The memory map register table (see Table 13) provides the is issued by writing 0x01 to Address 0xFF, setting the transfer default hexadecimal value for each hexadecimal address shown. bit. This allows these registers to be updated internally and The column with the heading (MSB) Bit 7 is the start of the simultaneously when the transfer bit is set. The transfer bit is default hexadecimal value given. Application Note AN-877, autoclearing. Interfacing to High Speed ADCs via SPI, documents the functions controlled by Register 0x00 to Register 0xFF. The remaining Channel-Specific Registers registers, Register 0x3A to Register 0x3E, are documented in Some channel setup functions, such as the NSR control func- the Memory Map Register Descriptions section. tion, can be programmed differently for each channel. In these Open Locations cases, channel address locations are internally duplicated for each channel. These registers and bits are designated in Table 13 All address and bit locations that are not included in Table 13 are as local. Local registers and bits can be accessed by setting the not currently supported for this device. Unused bits of a valid appropriate channel bits in Register 0x05. address location should be written with 0s. Writing to these locations is required only when part of an address location is If multiple channel bits are set, the subsequent write affects the open (for example, Address 0x18). If the entire address location registers of all selected channels. In a read cycle, only a single is open (for example, Address 0x13), this address location channel should be selected to read one of the registers. If multiple should not be written. channels are selected during a SPI read cycle, the part returns the value for Channel A only. Registers and bits designated as Default Values global in Table 13 affect the entire part or the channel features After the AD6657 is reset, critical registers are loaded with for which there are no independent per-channel settings. The default values. The default values for the registers are given in settings in Register 0x05 do not affect the global registers and bits. the memory map register table (see Table 13). Rev. B | Page 26 of 32 Data Sheet AD6657 MEMORY MAP REGISTER TABLE All address and bit locations that are not included in Table 13 are not currently supported for this device. Table 13. Memory Map Registers Default Addr. Register (MSB) (LSB) Value (Hex) Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 (Hex) Comments Chip Configuration Registers 0x00 SPI port Open LSB first Soft reset 1 Soft reset LSB first Open 0x18 Nibbles are 1 configuration mirrored so (global) that LSB first or MSB first mode is set correctly, regardless of shift mode. To control this register, all channel index bits in Register 0x05 must be set. 0x01 Chip ID 8-bit chip ID, Bits[7:0] 0x79 Read only. AD6657 = 0x79 (default) (global) Channel Index and Transfer Registers 0x05 Channel Enable Enable Open Open Channel Channel Channel Channel 0xCF Bits are set to index output output D enable C enable B enable A enable determine port for port for which Channel C Channel channel and A and on the chip Channel D Channel receives the B next write command; applies to local registers. 0xFF Transfer Open Open Open Open Open Open Open SW 0x00 Synchro- transfer nously 1 = on transfers 0 = off data from (default) the master shift register to the slave. ADC Function Registers 0x08 Power modes Open Open External Open Open Open Internal power-down 0x00 Determines power- mode (local) generic down pin 00 = normal operation modes function (default) of chip (global) 01 = full power-down operation. 0 = full 10 = standby power- down 1 = standby 0x0B Clock divide Open Open Clock divide phase Clock divide ratio 0x00 (global) 000 = divide by 1 000 = 0 input clock cycles delayed 001 = divide by 2 001 = 1 input clock cycle delayed 010 = divide by 3 010 = 2 input clock cycles delayed 011 = divide by 4 100 = divide by 5 101 = divide by 6 110 = divide by 7 111 = divide by 8 0x0C Shuffle mode Open Open Open Open Open Open Shuffle mode enable 0x01 Enables or (local) 00 = shuffle disabled disables 01 = shuffle enabled shuffle mode Rev. B | Page 27 of 32 AD6657 Data Sheet Default Addr. Register (MSB) (LSB) Value (Hex) Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 (Hex) Comments 0x0D Test mode Open Open Reset Reset Open Output test mode 0x00 When set, (local) long PN short PN 000 = off (normal operation) the test data generator generator 001 = midscale short is placed on 0 = on 0 = on 010 = positive FS the output 1 = off 1 = off 011 = negative FS pins in place (default) (default) 100 = alternating checkerboard of normal 101 = PN sequence long data. 110 = PN sequence short 111 = 1/0 word toggle 0x0E BIST enable Open Open Open Open Open BIST reset Open BIST 0x00 When Bit 0 (local) 0 = on enable is set, the 1 = off 1 = on built-in self- (default) 0 = off test function (default) is initiated. 0x10 Offset adjust Open Open Offset adjustment in LSBs from +127 to −128 0x00 Device (local) (twos complement format) offset trim. 011111 = +31 LSB 011110 = +30 LSB 011101 = +29 LSB … 000010 = +2 LSB 000001 = +1 LSB 000000 = 0 LSB … 111111 = −1 LSB 111110 = −2 LSB 111101 = −3 LSB … 100001 = −31 LSB 100000 = −32 LSB 0x14 Output mode Open Open Open Output Open Output Output format (local) 0x00 Configures (local) enable bar invert 00 = offset binary the outputs (local) (local) 01 = twos and the 1 = off 1 = on complement format of 0 = on 0 = off the data. 0x15 Output adjust Open Open Open Open Output port LVDS drive current 0x01 Output (local) 0000 = 3.72 mA current 0001 = 3.5 mA (default) adjustments. 0010 = 3.3 mA 0011 = 2.96 mA 0100 = 2.82 mA 0101 = 2.57 mA 0110 = 2.27 mA 0111 = 2.0 mA 1000 = 2.0 mA 0x16 Clock phase Invert DCO Open Open Open Open Open Open Open 0x00 When Bit 7 control clock is set, clock (local) 0 = off polarity is 1 = on reversed. 0x17 DCO output DCO delay Open Open Output port DCO clock delay 0x00 Enable DCO delay enable 00000 = 100 ps additional delay on the DCO pin delay and (local) 0 = off 00001 = 200 ps additional delay on the DCO pin set the delay 1 = on 00010 = 300 ps additional delay on the DCO pin time. … 11101 = 3.0 ns additional delay on the DCO pin 11110 = 3.1 ns additional delay on the DCO pin 11111 = 3.2 ns additional delay on the DCO pin 0x18 V select Open Open Open Internal V full-scale adjustment 0x00 Select REF REF (global) Main reference full-scale V adjustment adjustments REF 01111: internal 2.087 V p-p for V . REF … 00001: internal 1.772 V p-p 00000: internal 1.75 V p-p … 11111: internal 1.727 V p-p … 10000: internal 1.383 V p-p Rev. B | Page 28 of 32 Data Sheet AD6657 Default Addr. Register (MSB) (LSB) Value (Hex) Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 (Hex) Comments 0x24 BIST signature BIST Signature[7:0] 0x00 Read only. LSB (local) 0x25 BIST signature BIST Signature[15:8] 0x00 Read only. MSB (local) Digital Feature Control Registers 0x3A Sync control Open Open Open Open Open Open Clock Master 0x00 Control (global) divider sync register to sync enable synchronize enable 0 = off the clock 0 = off 1 = on divider. 1 = on 0x3C NSR control Open Open Open MODE NSR mode NSR 0x00 Noise (local) pin disable 000 = 22% BW mode enable shaping 0 = MODE 001 = 33% BW mode 0 = off requantizer pin used 1 = on (NSR) 1 = MODE (used controls. pin dis- only if abled Bit 4 = 1; otherwise ignored) 0x3E NSR tuning Open Open NSR tuning word 0x1C NSR word (local) frequency See the Noise Shaping Requantizer (NSR) section. tuning word. Equations for the tuning word are dependent on the NSR mode. Bits[3:1]— NSR Mode MEMORY MAP REGISTER DESCRIPTIONS For additional information about functions controlled Bits[3:1] determine the bandwidth mode of the NSR. When in Register 0x00 to Register 0xFF, see Application Note Bits[3:1] are set to 000, the NSR is configured for a 22% BW AN-877, Interfacing to High Speed ADCs via SPI. mode that provides enhanced SNR performance over 22% of the sample rate. When Bits[3:1] are set to 001, the NSR is con- Sync Control (Register 0x3A) figured for a 33% BW mode that provides enhanced SNR Bits[7:2]—Reserved performance over 33% of the sample rate. Bit 1—Clock Divider Sync Enable Bit 0—NSR Enable Bit 1 gates the sync pulse to the clock divider. The sync signal is The NSR is enabled when Bit 0 is high and disabled when Bit 0 enabled when Bit 1 is high and Bit 0 is high. This is continuous is low. Bit 0 is ignored unless the MODE pin disable bit (Bit 4) sync mode. is set. Bit 0—Master Sync Enable NSR Tuning Word (Register 0x3E) Bit 0 must be high to enable any of the sync functions. If Bits[7:6]—Reserved the sync capability is not used, this bit should remain low Bits[5:0]— NSR Tuning Word to conserve power. The NSR tuning word sets the band edges of the NSR band. In NSR Control (Register 0x3C) 22% BW mode, there are 57 possible tuning words; in 33% BW Bits[7:5]—Reserved mode, there are 34 possible tuning words. For either mode, each Bit 4—MODE Pin Disable step represents 0.5% of the ADC sample rate. For the equations used to calculate the tuning word based on the BW mode of Bit 4 specifies whether the selected channels will be controlled operation, see the Noise Shaping Requantizer (NSR) section. by the MODE pin. Local registers act on the channels that are selected by the channel index register (Address 0x05). Rev. B | Page 29 of 32 AD6657 Data Sheet APPLICATIONS INFORMATION VCMx Pins DESIGN GUIDELINES The VCMx pins are provided to set the common-mode level Before starting the design and layout of the AD6657 in a system, of the analog inputs. The VCMx pins should be decoupled to it is recommended that the designer become familiar with these ground with a 0.1 μF capacitor, as shown in Figure 31. guidelines, which discuss the special circuit connections and layout requirements needed for certain pins. SPI Port Power and Ground Recommendations The SPI port should not be active during periods when the full dynamic performance of the AD6657 is required. Because the When connecting power to the AD6657, it is recommended SCLK signal, the CSB signal, and the SDIO signal are typically that two separate 1.8 V supplies be used. Use one supply for asynchronous to the ADC clock, noise from these signals can analog (AVDD); use a separate supply for the digital outputs degrade AD6657 performance. If the on-board SPI bus is used (DRVDD). The AVDD and DRVDD supplies should be isolated for other devices, it may be necessary to provide buffers between with separate decoupling capacitors. Several different decoupling this bus and the AD6657 to prevent these signals from transi- capacitors can be used to cover both high and low frequencies. tioning at the receiver inputs during critical sampling periods. These capacitors should be located close to the point of entry at the PCB level and close to the pins of the part, with minimal trace length. A single PCB ground plane should be sufficient when using the AD6657. With proper decoupling and smart partitioning of the PCB analog, digital, and clock sections, optimum performance is easily achieved. Rev. B | Page 30 of 32 Data Sheet AD6657 OUTLINE DIMENSIONS 10.10 A1 BALL 10.00 SQ CORNER A1 BALL 9.90 12 11 10 9 8 764 5 312 CORNER A B C D 8.80 E BSC SQ F G H 0.80 J K L M TOP VIEW 0.60 BOTTOM VIEW REF DETAIL A * 1.40 MAX 0.65 MIN DETAIL A 0.25 MIN 0.50 COPLANARITY SEATING 0.45 0.20 PLANE 0.40 BALL DIAMETER * COMPLIANT WITH JEDEC STANDARDS MO-275-EEAB-1 WITH EXCEPTION TO PACKAGE HEIGHT. Figure 52. 144-Ball Chip Scale Package Ball Grid Array [CSP_BGA] (BC-144-1) Dimensions shown in millimeters ORDERING GUIDE 1 Model Temperature Range Package Description Package Option AD6657BBCZ −40°C to +85°C 144-Ball Chip Scale Package Ball Grid Array [CSP_BGA] BC-144-1 AD6657BBCZRL −40°C to +85°C 144-Ball Chip Scale Package Ball Grid Array [CSP_BGA] BC-144-1 AD6657EBZ Evaluation Board 1 Z = RoHS Compliant Part. Rev. B | Page 31 of 32 10-21-2010-B AD6657 Data Sheet NOTES ©2009–2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D08557-0-8/11(B) Rev. B | Page 32 of 32