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10-bit, 125/105 msps, 1.8 v dual analog-to-digital converter (adc) ad9608 rev. 0 information furnished by analog devices is believed to be accurate and reliable. however, no responsibility is assumed by analog devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. specifications subject to change without notice. no license is granted by implication or otherwise under any patent or patent rights of analog devices. trademarks and registered trademarks are the property of their respective owners. one technology way, p.o. box 9106, norwood, ma 02062-9106, u.s.a. tel: 781.329.4700 www.analog.com fax: 781.461.3113 ?2011 analog devices, inc. all rights reserved. features 1.8 v analog supply operation 1.8 v cmos or 1.8 v lvds output snr = 61.7 dbfs at 70 mhz sfdr = 85 dbc at 70 mhz low power: 71 mw/channel adc core at 125 msps differential analog input with 650 mhz bandwidth if sampling frequencies to 200 mhz on-chip voltage reference and sample-and-hold circuit 2 v p-p differential analog input dnl = 0.13 lsb serial port control options offset binary, gray code, or twos complement data format optional clock duty cycle stabilizer integer 1-to-8 input clock divider data output multiplex option built-in selectable digital test pattern generation energy-saving power-down modes data clock out with programmable clock and data alignment applications communications diversity radio systems i/q demodulation systems broadband data applications battery-powered instruments handheld scope meters portable medical imaging ultrasound functional block diagram vin+a vin?a vref sense vcm rbias vin?b vin+b ora d0a d9a dcoa drvdd orb d9b d0b dcob sdio a gnd a v dd sclk spi programming data mux option pdwn dfs clk+ clk? mode controls dcs duty cycle stabilizer sync divide 1to 8 oeb csb ref select adc cmos/lvds output buffer adc cmos/lvds output buffer ad9608 notes 1. pin names are for the cmos pin configuration only; see figure 7 for lvds pin names. 09977-001 figure 1. product highlights 1. operates from a single 1.8 v analog power supply and features a separate digital output driver supply to accom- modate 1.8 v cmos or 1.8 v lvds logic families. 2. provides a patented sample-and-hold circuit that maintains excellent performance for input frequencies up to 200 mhz and is designed for low cost, low power, and ease of use. 1 3. includes a standard serial port interface that supports various product features and functions, such as data output format- ting, internal clock divider, power-down, dco/data timing, and offset adjustments. 4. packaged in a 64-lead, rohs-compliant lfcsp that is pin compatible with the ad9650, ad9269 , and ad9268 16-bit adcs, the ad9258 and ad9648 14-bit adcs, the ad9628 and ad9231 12-bit adcs, and the ad9204 10-bit adc, enabling a simple migration path between 10-bit and 16-bit converters sampling from 20 msps to 125 msps. 1 this product is protected by a u.s. patent.
ad9608 rev. 0 | page 2 of 40 table of contents features .............................................................................................. 1 ? applications....................................................................................... 1 ? functional block diagram .............................................................. 1 ? product highlights ........................................................................... 1 ? revision history ............................................................................... 2 ? general description ......................................................................... 3 ? specifications..................................................................................... 4 ? dc specifications........................................................................... 4 ? ac specifications ........................................................................... 5 ? digital specifications ................................................................... 6 ? switching specifications ................................................................ 7 ? timing specifications .................................................................. 8 ? absolute maximum ratings.......................................................... 10 ? thermal characteristics ............................................................ 10 ? esd caution................................................................................ 10 ? pin configurations and function descriptions ......................... 11 ? typical performance characteristics ........................................... 17 ? ad9608-125 ................................................................................ 17 ? ad9608-105 ................................................................................ 20 ? equivalent circuits ......................................................................... 22 ? theory of operation ...................................................................... 23 ? adc architecture ...................................................................... 23 ? analog input considerations.................................................... 23 ? voltage reference ....................................................................... 25 ? clock input considerations...................................................... 26 ? channel/chip synchronization................................................ 28 ? power dissipation and standby mode .................................... 28 ? digital outputs ........................................................................... 29 ? timing ......................................................................................... 29 ? built-in self-test (bist) and output test .................................. 30 ? built-in self-test (bist)............................................................ 30 ? output test modes..................................................................... 30 ? serial port interface (spi).............................................................. 31 ? configuration using the spi..................................................... 31 ? hardware interface..................................................................... 32 ? configuration without the spi ................................................ 32 ? spi accessible features.............................................................. 32 ? memory map .................................................................................. 33 ? reading the memory map register table............................... 33 ? memory map register table..................................................... 34 ? memory map register descriptions........................................ 37 ? applications information .............................................................. 39 ? design guidelines ...................................................................... 39 ? outline dimensions ....................................................................... 40 ? ordering guide .......................................................................... 40 ? revision history 7/11revision 0: initial version
ad9608 rev. 0 | page 3 of 40 general description the ad9608 is a monolithic, dual-channel, 1.8 v supply, 10-bit, 105 msps/125 msps analog-to-digital converter (adc) that features a high performance sample-and-hold circuit and an on-chip voltage reference. the product uses multistage differential pipeline architecture with output error correction logic to provide 10-bit accuracy at 125 msps data rates and to guarantee no missing codes over the full operating temperature range. the adc contains several features designed to maximize flexibility and minimize system cost, such as programmable clock and data alignment and programmable digital test pattern generation. the available digital test patterns include built-in deterministic and pseudorandom patterns, along with custom user-defined test patterns entered via the serial port interface (spi). a differential clock input controls all internal conversion cycles. an optional duty cycle stabilizer (dcs) compensates for wide variations in the clock duty cycle while maintaining excellent overall adc performance. the digital output data is presented in offset binary, gray code, or twos complement format. a data output clock (dco) is provided for each adc channel to ensure proper latch timing with receiving logic. logic levels of 1.8 v cmos and 1.8 v lvds are supported. output data can also be multiplexed onto a single output bus. the ad9608 is available in a 64-lead rohs-compliant lfcsp and is specified over the industrial temperature range (?40c to +85c). this product is protected by a u.s. patent.
ad9608 rev. 0 | page 4 of 40 specifications dc specifications avdd = 1.8 v, drvdd = 1.8 v, maximum sample rate, vin = ?1.0 dbfs differential input, 1.0 v internal reference, dcs enabled, un less otherwise noted. table 1. ad9608-105 ad9608-125 parameter temp min typ max min typ max unit resolution full 10 10 bits accuracy no missing codes full guaranteed guaranteed offset error full ?1.0 ?0.3 +0.4 ?1.0 ?0.3 +0.4 % fsr gain error full ?2.8 1.5 +9 .0 ?2.8 1.5 +9.0 % fsr differential nonlinearity (dnl) 1 full 0.35 0.35 lsb 25c 0.12 0.13 lsb integral nonlinearity (inl) 1 full 0.40 0.40 lsb 25c 0.14 0.14 lsb matching characteristic offset error full 0.1 1.0 0.1 1.0 % fsr gain error full 0.5 6.5 0.5 6.5 % fsr temperature drift offset error full 2 2 ppm/c gain error full 50 50 ppm/c internal voltage reference output voltage (1 v mode) fu ll 0.98 1.00 1.02 0.98 1.00 1.02 v load regulation error at 1.0 ma full 2 2 mv input referred noise vref = 1.0 v 25c 0.08 0.08 lsb rms analog input input span, vref = 1.0 v full 2 2 v p-p input capacitance 2 full 5 5 pf input resistance (differential) full 7.5 7.5 k input common-mode voltage full 0.9 0.9 v input common-mode range full 0.5 1.3 0.5 1.3 v power supplies supply voltage avdd full 1.7 1.8 1.9 1.7 1.8 1.9 v drvdd full 1.7 1.8 1.9 1.7 1.8 1.9 v supply current i avdd 1 full 76.8 82.0 87.7 93.0 ma i drvdd 1 (1.8 v cmos) full 14.7 17.4 ma i drvdd 1 (1.8 v lvds) full 48.5 49.7 ma power consumption dc input full 125 141 mw sine wave input 1 (drvdd = 1.8 v cmos output mode) full 165 174 189 199 mw sine wave input 1 (drvdd = 1.8 v lvds output mode) full 226 247 mw standby power 3 full 108 120 mw power-down power full 2.0 2.0 mw 1 measured with a low input frequency, full-scale sine wa ve, with approximately 5 pf load ing on each output bit. 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 with the clk pins active (1.8 v cmos mode).
ad9608 rev. 0 | page 5 of 40 ac specifications avdd = 1.8 v, drvdd = 1.8 v, maximum sample rate, vin = ?1.0 dbfs differential input, 1.0 v internal reference, dcs enabled, un less otherwise noted. table 2. ad9608-105 ad9608-125 parameter 1 temp min typ max min typ max unit signal-to-noise-ratio (snr) f in = 9.7 mhz 25c 61.7 61.7 dbfs f in = 30.5 mhz 25c 61.7 61.7 dbfs f in = 70 mhz 25c 61.7 61.7 dbfs full 61.3 61.3 dbfs f in = 100 mhz 25c 61.6 61.6 dbfs f in = 200 mhz 25c 61.4 61.4 dbfs signal-to-noise and distortion (sinad) f in = 9.7 mhz 25c 61.6 61.6 dbfs f in = 30.5 mhz 25c 61.6 61.6 dbfs f in = 70 mhz 25c 61.6 61.6 dbfs full 61.1 61.1 dbfs f in = 100 mhz 25c 61.5 61.5 dbfs f in = 200 mhz 25c 61.3 61.3 dbfs effective number of bits (enob) f in = 9.7 mhz 25c 9.9 9.9 bits f in = 30.5 mhz 25c 9.9 9.9 bits f in = 70 mhz 25c 9.9 9.9 bits f in = 100 mhz 25c 9.9 9.9 bits f in = 200 mhz 25c 9.9 9.9 bits worst second or third harmonic f in = 9.7 mhz 25c ?90 ?90 dbc f in = 30.5 mhz 25c ?89 ?89 dbc f in = 70 mhz 25c ?89 ?89 dbc full ?75 ?75 dbc f in = 100 mhz 25c ?89 ?89 dbc f in = 200 mhz 25c ?84 ?84 dbc spurious-free dynamic range (sfdr) f in = 9.7 mhz 25c 85 85 dbc f in = 30.5 mhz 25c 85 85 dbc f in = 70 mhz 25c 85 85 dbc full 75 75 dbc f in = 100 mhz 25c 85 85 dbc f in = 200 mhz 25c 84 84 dbc worst other (harmonic or spur) f in = 9.7 mhz 25c ?85 ?85 dbc f in = 30.5 mhz 25c ?85 ?85 dbc f in = 70 mhz 25c ?85 ?85 dbc full ?75 ?75 dbc f in = 100 mhz 25c ?85 ?85 dbc f in = 200 mhz 25c ?85 ?85 dbc two-tone sfdr f in = 29 mhz (?7 dbfs ), 32 mhz (?7 dbfs ) 25c 82 82 dbc crosstalk 2 full ?95 ?95 db analog input bandwidth 25c 650 650 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 100 mhz with ?1.0 dbfs on one channel an d no input on the alternate channel.
ad9608 rev. 0 | page 6 of 40 digital specifications avdd = 1.8 v, drvdd = 1.8 v, maximum sample rate, vin = ?1.0 dbfs differential input, 1.0 v internal reference, and dcs enabled , unless otherwise noted. table 3. parameter temp 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 0.3 3.6 v p-p input voltage range full agnd ? 0.3 avdd + 0.2 v input common-mode range full 0.9 1.4 v high level input current full ?10 +10 a low level input current full ?10 +10 a input capacitance full 4 pf input resistance full 8 10 12 k logic input (csb) 1 high level input voltage full 1.22 drvdd + 0.2 v low level input voltage full 0 0.6 v high level input current full ?10 +10 a low level input current full 40 132 a input resistance full 26 k input capacitance full 2 pf logic input (sclk/dfs/sync) 2 high level input voltage full 1.22 drvdd + 0.2 v low level input voltage full 0 0.6 v high level input current (vin = 1.8 v) full ?92 ?135 a low level input current full ?10 +10 a input resistance full 26 k input capacitance full 2 pf logic input/output (sdio/dcs) 1 high level input voltage full 1.22 drvdd + 0.2 v low level input voltage full 0 0.6 v high level input current full ?10 +10 a low level input current full 38 128 a input resistance full 26 k input capacitance full 5 pf logic inputs (oeb, pdwn) 2 high level input voltage full 1.22 drvdd + 0.2 v low level input voltage full 0 0.6 v high level input current (vin = 1.8 v) full ?90 ?134 a low level input current full ?10 +10 a input resistance full 26 k input capacitance full 5 pf digital outputs cmos modedrvdd = 1.8 v high level output voltage i oh = 50 a full 1.79 v i oh = 0.5 ma full 1.75 v low level output voltage i ol = 1.6 ma full 0.2 v i ol = 50 a full 0.05 v
ad9608 rev. 0 | page 7 of 40 parameter temp min typ max unit lvds modedrvdd = 1.8 v differential output voltage (v od ), ansi mode full 290 345 400 mv output offset voltage (v os ), ansi mode full 1.15 1.25 1.35 v differential output voltage (v od ), reduced swing mode full 160 200 230 mv output offset voltage (v os ), reduced swing mode full 1.15 1.25 1.35 v 1 pull up. 2 pull down. switching specifications avdd = 1.8 v, drvdd = 1.8 v, maximum sample rate, vin = ?1.0 dbfs differential input, 1.0 v internal reference, and dcs enabled , unless otherwise noted. table 4. ad9608-105 ad9608-125 parameter temp min typ max min typ max unit clock input parameters input clock rate full 1000 1000 mhz conversion rate 1 dcs enabled full 20 105 20 125 msps dcs disabled full 10 105 10 125 msps clk perioddivide-by-1 mode (t clk ) full 9.52 8 ns clk pulse width high (t ch ) full 4.76 4 ns aperture delay (t a ) full 1.0 1.0 ns aperture uncertainty (jitter, t j ) full 0.07 0.07 ps rms data output parameters cmos mode cmos mode (drvdd = 1.8 v) data propagation delay (t pd ) full 1.8 2.9 4.4 1.8 2.9 4.4 ns dco propagation delay (t dco ) 2 full 2.0 3.1 4.4 2.0 3.1 4.4 ns dco to data skew (t skew ) full ?1.2 ?0.1 +1.0 ?1.2 ?0.1 +1.0 ns lvds mode (drvdd = 1.8 v) data propagation delay (t pd ) full 2.4 2.4 ns dco propagation delay (t dco ) 2 full 4.4 4.4 ns dco to data skew (t skew ) full ?0.1 +0.2 +0.5 ?0.1 +0.2 +0.5 ns cmos mode pipeline delay (latency) full 16 16 cycles lvds mode pipeline delay (latency) channel a/channel b full 16/16.5 16/16.5 cycles wake-up time (power-down) 3 full 350 350 s wake-up time (standby) full 250 250 ns out-of-range recovery time full 2 2 cycles 1 conversion rate is the clock rate after the divider. 2 additional dco delay can be added by writing to bits[2:0] in spi register 0x17 (see ta ). ble 18 3 wake-up time is defined as the time required to return to normal operation from power-down mode.
ad9608 rev. 0 | page 8 of 40 timing specifications table 5. parameter descriptions limit sync timing requirements t ssync sync to rising edge of clk+ setup time 0.24 ns typ t hsync sync to rising edge of clk+ hold time 0.40 ns typ spi timing requirements t ds setup time between the data and th e rising edge of sclk 2 ns min t dh hold time between the data and th e rising edge of sclk 40 ns min t clk period of the sclk 2 ns min t s setup time between csb and sclk 2 ns min t h hold time between csb and sclk 10 ns min t high sclk pulse width high 10 ns min t low sclk pulse width low 10 ns min t en_sdio time required for the sdio pin to switch from an input to an output relative to the sclk falling edge 10 ns min t dis_sdio time required for the sdio pin to switch from an output to an input relative to the sclk rising edge 2 ns min timing diagrams t pd t skew t ch t dco t clk n ? 16 n ? 17 n ? 1 n + 1 n + 2 n + 3 n + 5 n + 4 n n ? 15 n ? 14 n ? 13 n ? 12 vin clk+ clk? ch a/ch b data dcoa/dcob t a 09977-002 figure 2. cmos default output mode data output timing t pd t skew t ch t dco t clk ch a n ? 16 ch b n ? 15 ch a n ? 14 ch b n ? 13 ch a n ? 12 ch b n ? 11 ch a n ? 10 ch b n ? 9 ch a n ? 8 n ? 1 n + 1 n + 2 n + 3 n + 5 n + 4 n vin clk+ clk? ch a data dcoa/dcob t a ch b data ch b n ? 16 ch a n ? 15 ch b n ? 14 ch a n ? 13 ch b n ? 12 ch a n ? 11 ch b n ? 10 ch a n ? 9 ch b n ? 8 09977-003 figure 3. cmos interleaved outp ut mode data output timing
ad9608 rev. 0 | page 9 of 40 t pd t skew t ch t dco t clk ch a n ? 16 ch b n ? 16 ch a n ? 15 ch b n ? 15 ch a n ? 14 ch b n ? 14 ch a n ? 13 ch b n ? 13 ch a n ? 12 n ? 1 n + 1 n + 2 n + 3 n + 5 n + 4 n vin clk+ clk? dco? dco+ d0+ (lsb) parallel interleaved mode d0? (lsb) d9+ (msb) d9? (msb) t a ch a n ? 16 ch b n ? 16 ch a n ? 15 ch b n ? 15 ch a n ? 14 ch b n ? 14 ch a n ? 13 ch b n ? 13 ch a n ? 12 ch a0 n ? 16 ch a1 n ? 16 ch a0 n ? 15 ch a1 n ? 15 ch a0 n ? 14 ch a1 n ? 14 ch a0 n ? 13 ch a1 n ? 13 ch a0 n ? 12 d1+/d0+ (lsb) channel multiplexed mode channel a d1?/d0? (lsb) d9+/d8+ (msb) d9?/d8? (msb) ch a8 n ? 16 ch a9 n ? 16 ch a8 n ? 15 ch a9 n ? 15 ch a8 n ? 14 ch a9 n ? 14 ch a8 n ? 13 ch a9 n ? 13 ch a8 n ? 12 ch b0 n ? 16 ch b1 n ? 16 ch b0 n ? 15 ch b1 n ? 15 ch b0 n ? 14 ch b1 n ? 14 ch b0 n ? 13 ch b1 n ? 13 ch b0 n ? 12 d1+/d0+ (lsb) channel multiplexed mode channel b d1?/d0? (lsb) d9+/d8+ (msb) d9?/d8? (msb) ch b8 n ? 16 ch b9 n ? 16 ch b8 n ? 15 ch b9 n ? 15 ch b8 n ? 14 ch b9 n ? 14 ch b8 n ? 13 ch b9 n ? 13 ch b8 n ? 12 09977-004 figure 4. lvds modes for data output timing sync clk+ t hsync t ssync 09977-005 figure 5. sync input timing requirements
ad9608 rev. 0 | page 10 of 40 absolute maximum ratings table 6. parameter rating electrical 1 avdd to agnd ?0.3 v to +2.0 v drvdd to agnd ?0.3 v to +2.0 v vin+a/vin+b, vin?a/vin?b to agnd ?0.3 v to avdd + 0.2 v clk+, clk? to agnd ?0.3 v to avdd + 0.2 v sync to agnd ?0.3 v to avdd + 0.2 v vcm to agnd ?0.3 v to avdd + 0.2 v rbias to agnd ?0.3 v to avdd + 0.2 v csb to agnd ?0.3 v to drvdd + 0.2 v sclk/dfs to agnd ?0.3 v to drvdd + 0.2 v sdio/dcs to agnd ?0.3 v to drvdd + 0.2 v oeb ?0.3 v to drvdd + 0.2 v pdwn ?0.3 v to drvdd + 0.2 v d0a, d0b through d9a, d9b to agnd ?0.3 v to drvdd + 0.2 v dcoa , dcob to agnd ?0.3 v to drvdd + 0.2 v environmental operating temperature range (ambient) ?40c to +85c maximum junction temperature under bias 150c storage temperature range (ambient) ?65c to +150c thermal characteristics the exposed paddle must be soldered to the ground plane for the lfcsp package. soldering the exposed paddle to the pcb increases the reliability of the solder joints and maximizes the thermal capability of the package. table 7. thermal resistance package type airflow velocity (m/sec) ja 1, 2 jc 1, 3 jb 1, 4 jt 1, 2 unit 0 22.3 1.4 n/a 0.1 c/w 1.0 19.5 n/a 11.8 0.2 c/w 64-lead lfcsp 9 mm 9 mm (cp-64-4) 2.5 17.5 n/a n/a 0.2 c/w 1 per jedec 51-7, plus jede c 25-5 2s2p test board. 2 per jedec jesd51-2 (still air) or jedec jesd51-6 (moving air). 3 per mil-std 883, method 1012.1. 4 per jedec jesd51-8 (still air). typical ja is specified for a 4-layer pcb with a solid ground plane. as shown table 7 , airflow improves heat dissipation, which reduces ja . in addition, metal in direct contact with the package leads from metal traces, through holes, ground, and power planes reduces ja . esd caution 1 the inputs and outputs are rated to the supply voltage (avdd or drvdd) + 0.2 v but should not exceed 2.1 v. stresses above those listed under absolute maximum ratings may cause permanent damage to the device. this is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ad9608 rev. 0 | page 11 of 40 pin configurations and function descriptions pin 1 indicator 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 drvdd d8b d9b (msb) orb dcob dcoa nc nc nc drvdd nc nc nc d0a (lsb) d1a d2a 64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 avdd avdd vin+b vin?b avdd avdd rbias vcm sense vref avdd avdd vin?a vin+a avdd avdd 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 clk+ clk? sync nc nc nc nc nc nc d0b (lsb) d1b drvdd d2b d3b d4b d5b d6b d7b pdwn oeb csb sclk/dfs sdio/dcs ora d9a (msb) d8a d7a drvdd d6a d5a d4a d3a 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 ad9608 parallel cmos top view (not to scale) notes 1. nc = no connect. do not connect to this pin. 2. the exposed thermal pad on the bottom of the package provides the analog ground for the part. this exposed pad must be connected to ground for proper operation. 09977-006 figure 6. parallel cmos pin configuration (top view) table 8. pin function descriptions (parallel cmos mode) pin no. mnemonic type description adc power supplies 10, 19, 28, 37 drvdd supply digital o utput driver supply (1.8 v nominal). 49, 50, 53, 54, 59, 60, 63, 64 avdd supply analog power supply (1.8 v nominal). 4, 5, 6, 7, 8, 9, 25, 26, 27, 29, 30, 31 nc no connect. do not connect to this pin. 0 agnd, exposed pad ground the exposed thermal pad on the bottom of the package provides the analog ground for the part. this exposed pad must be connected to ground for proper operation. adc analog 51 vin+a input differential analog input pin (+) for channel a. 52 vin?a input differential analog input pin (?) for channel a. 62 vin+b input differential analog input pin (+) for channel b. 61 vin?b input differential analog input pin (?) for channel b. 55 vref input/output voltage reference input/output. 56 sense input reference mode selection. 58 rbias input/output external reference bias resistor. 57 vcm output common-mode level bi as output for analog inputs. 1 clk+ input adc clock inputtrue. 2 clk? input adc clock inputcomplement.
ad9608 rev. 0 | page 12 of 40 pin no. mnemonic type description digital input 3 sync input digital synchronization pin. slave mode only. digital outputs 32 d0a (lsb) output channel a cmos output data. 33 d1a output channel a cmos output data. 34 d2a output channel a cmos output data. 35 d3a output channel a cmos output data. 36 d4a output channel a cmos output data. 38 d5a output channel a cmos output data. 39 d6a output channel a cmos output data. 40 d7a output channel a cmos output data. 41 d8a output channel a cmos output data. 42 d9a (msb) output channel a cmos output data. 43 ora output channel a overrange output. 11 d0b (lsb) output channel b cmos output data. 12 d1b output channel b cmos output data. 13 d2b output channel b cmos output data. 14 d3b output channel b cmos output data. 15 d4b output channel b cmos output data. 16 d5b output channel b cmos output data. 17 d6b output channel b cmos output data. 18 d7b output channel b cmos output data. 20 d8b output channel b cmos output data. 21 d9b (msb) output channel b cmos output data. 22 orb output channel b overrange output 24 dcoa output channel a data clock output. 23 dcob output channel b data clock output. spi control 45 sclk/dfs input spi serial clock/data fo rmat select pin in external pin mode. 44 sdio/dcs input/output spi serial data i/o/duty cycle stabilizer pin in external pin mode. 46 csb input spi chip select (active low). adc configuration 47 oeb input output enable input (activ e low). pin must be enabled via spi. 48 pdwn input power-down input in external pin mode. in spi mode, this input can be configured as power-down or standby.
ad9608 rev. 0 | page 13 of 40 pin 1 indicator 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 d2? d2+ drvdd d3? d3+ d4? d4+ dco? dco+ d5? d5+ drvdd d6+ d6? d7+ d7? 64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 avdd avdd vin+b vin?b avdd avdd rbias vcm sense vref avdd avdd vin?a vin+a avdd avdd 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 clk+ clk? sync nc nc nc nc nc nc nc nc nc nc drvdd nc nc d0? (lsb) d0+ (lsb) d1? d1+ pdwn oeb csb sclk/dfs sdio/dcs or+ or? drvdd d9+ (msb) d9? (msb) d8+ d8? 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 ad9608 interleaved parallel lvds top view (not to scale) notes 1. nc = no connect. do not connect to this pin. 2 . the exposed thermal pad on the bottom of the package provides the analog ground for the part. this exposed pad must b e connected to ground for proper operation. 09977-007 figure 7. interleaved parallel lvds pin configuration (top view) table 9. pin function descriptions (interleaved parallel lvds mode) pin no. mnemonic type description adc power supplies 10, 19, 28, 37 drvdd supply digital o utput driver supply (1.8 v nominal). 49, 50, 53, 54, 59, 60, 63, 64 avdd supply analog power supply (1.8 v nominal). 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16 nc no connect. do not connect to this pin. 0 agnd, exposed pad ground the exposed thermal pad on the bottom of th e package provides the analog ground for the part. this exposed pad must be conne cted to ground for proper operation. adc analog 51 vin+a input differential analog input pin (+) for channel a. 52 vin?a input differential analog input pin (?) for channel a. 62 vin+b input differential analog input pin (+) for channel b. 61 vin?b input differential analog input pin (?) for channel b. 55 vref input/output voltage reference input/output. 56 sense input reference mode selection. 58 rbias input/output external reference bias resistor. 57 vcm output common-mode level bi as output for analog inputs. 1 clk+ input adc clock inputtrue. 2 clk? input adc clock inputcomplement. digital input 3 sync input digital synchronization pin. slave mode only.
ad9608 rev. 0 | page 14 of 40 pin no. mnemonic type description digital outputs 18 d0+ (lsb) output channel a/channel b lvds output data 0true. 17 d0? (lsb) output channel a/channel b lvds output data 0complement. 21 d1+ output channel a/channel b lvds output data 1true. 20 d1? output channel a/channel b lvds output data 1complement. 23 d2+ output channel a/channel b lvds output data 2 true. 22 d2? output channel a/channel b lvds output data 2complement. 27 d3+ output channel a/channel b lvds output data 3true. 26 d3? output channel a/channel b lvds output data 3complement. 30 d4+ output channel a/channel b lvds output data 4true. 29 d4? output channel a/channel b lvds output data 4complement. 32 d5+ output channel a/channel b lvds output data 5true. 31 d5? output channel a/channel b lvds output data 5complement. 34 d6+ output channel a/channel b lvds output data 6true. 33 d6? output channel a/channel b lvds output data 6complement. 36 d7+ output channel a/channel b lvds output data 7true. 35 d7? output channel a/channel b lvds output data 7complement. 39 d8+ output channel a/channel b lvds output data 8true. 38 d8? output channel a/channel b lvds output data 8complement. 41 d9+ (msb) output channel a/channel b lvds output data 9true. 40 d9? (msb) output channel a/channel b lvds output data 9complement. 43 or+ output channel a/channel b lvds overrange outputtrue. 42 or? output channel a/channel b lvds overrange outputcomplement. 25 dco+ output channel a/channel b lvds data clock outputtrue. 24 dco? output channel a/channel b lv ds data clock outputcomplement. spi control 45 sclk/dfs input spi serial clock/data fo rmat select pin in external pin mode. 44 sdio/dcs input/output spi serial data i/o/duty cycle stabilizer pin in external pin mode. 46 csb input spi chip select (active low). adc configuration 47 oeb input output enable input (activ e low). pin must be enabled via spi. 48 pdwn input power-down input in external pin mode. in spi mode, this input can be configured as power-down or standby.
ad9608 rev. 0 | page 15 of 40 pin 1 indicator 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 b d7?/d6? b d7+/d6+ drvdd b d9?/d8? (msb) b d9+/d8+ (msb) dco? dco+ nc nc drvdd nc nc a d1?/d0? (lsb) a d1+/d0+ (lsb) a d3+/d2+ a d3?/d2? 64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 avdd avdd vin+b vin?b avdd avdd rbias vcm sense vref avdd avdd vin?a vin+a avdd avdd 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 clk+ clk? sync nc nc nc nc nc nc nc nc drvdd b d1?/d0? (lsb) b d1+/d0+ (lsb) b d3?/d2? b d3+/d2+ b d5?/d4? b d5+/d4+ pdwn oeb csb sclk/dfs sdio/dcs or+ or? a d9+/d8+ (msb) a d9?/d8? (msb) drvdd a d7+/d6+ a d7?/d6? a d5+/d4+ a d5?/d4? 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 ad9608 channel multipl exed lvds top view (not to scale) notes 1. nc = no connect. do not connect to this pin. 2. the exposed thermal pad on the bottom of the package provides the analog ground for the part. this exposed pad must be connected to ground for proper operation. 09977-008 figure 8. channel multiplexed lv ds pin configuration (top view) table 10 pin function descriptions (c hannel multiplexed parallel lvds mode) pin no. mnemonic type description adc power supplies 10, 19, 28, 37 drvdd supply digital o utput driver supply (1.8 v nominal). 49, 50, 53, 54, 59, 60, 63, 64 avdd supply analog power supply (1.8 v nominal). 4, 5, 6, 7, 8, 9, 11, 12, 26, 27, 29, 30 nc no connect. do not connect to this pin. 0 agnd, exposed pad ground the exposed thermal pad on the bottom of the package provides the analog ground for the part. this expo sed pad must be connected to ground for proper operation. adc analog 51 vin+a input differential analog input pin (+) for channel a. 52 vin?a input differential analog input pin (?) for channel a. 62 vin+b input differential analog input pin (+) for channel b. 61 vin?b input differential analog input pin (?) for channel b. 55 vref input/output voltage reference input/output. 56 sense input reference mode selection. 58 rbias input/output external reference bias resistor. 57 vcm output common-mode level bi as output for analog inputs. 1 clk+ input adc clock inputtrue. 2 clk? input adc clock inputcomplement. digital input 3 sync input digital synchronization pin. slave mode only.
ad9608 rev. 0 | page 16 of 40 pin no. mnemonic type description digital outputs 14 b d1+/d0+ (lsb) output channel b lvds output data 1/ data 0true. 13 b d1?/d0? (lsb) output channel b lvds output data 1/ data 0complement. 16 b d3+/d2+ output channel b lvds output data 3/ data 2true. 15 b d3?/d2? output channel b lvds output data 3/ data 2complement. 18 b d5+/d4+ output channel b lvds output data 5/ data 4true. 17 b d5?/d4? output channel b lvds output data 5/ data 4complement. 21 b d7+/d6+ output channel b lvds output data 7/ data 6true. 20 b d7?/d6? output channel b lvds output data 7/ data 6complement. 23 b d9+/d8+ (msb) output channel b lvds output data 9/ data 8true. 22 b d9?/d8? (msb) output channel b lvds output data 9/ data 8complement. 32 a d1+/d0+ (lsb) output channel a lvds output data 1/ data 0true. 31 a d1?/d0? (lsb) 34 a d3+/d2+ output channel a lvds output data 3/ data 2true. 33 a d3?/d2? output channel a lvds output data 3/ data 2complement. 36 a d5+/d4+ output channel a lvds output data 5/ data 4true. 35 a d5?/d4? output channel a lvds output data 5/ data 4complement. 39 a d7+/d6+ output channel a lvds output data 7/ data 6true. 38 a d7?/d6? output channel a lvds output data 7/ data 6complement. 41 a d9+/d8+ (msb) output channel a lvds output data 9/ data 8true. 40 a d9?/d8? (msb) output channel a lvds output data 9/ data 8complement. 43 or+ output channel a/channel b lvds overrange outputtrue. 42 or? output channel a/channel b lvds overrange outputcomplement. 25 dco+ output channel a/channel b lvds data clock outputtrue. 24 dco? output channel a/channel b lv ds data clock outputcomplement. spi control 45 sclk/dfs input spi serial clock/data fo rmat select pin in external pin mode. 44 sdio/dcs input/output spi serial data i/o/duty cycle stabilizer pin in external pin mode. 46 csb input spi chip select (active low). adc configuration 47 oeb input output enable input (activ e low). pin must be enabled via spi. 48 pdwn input power-down input in external pin mo de. in spi mode, this input can be configured as power-down or standby.
ad9608 rev. 0 | page 17 of 40 typical performance characteristics ad9608-125 avdd = 1.8 v, drvdd = 1.8 v, maximum sample rate, vin = ?1.0 dbfs differential input, 1.0 v internal reference, and dcs enabled , unless otherwise noted. 0 ?20 ?40 ?60 ?80 ?100 ?120 06 0 10 20 30 40 50 amplitude (dbfs) frequency (mhz) 125msps 9.7mhz at ?1dbfs snr = 60.6db (61.6dbfs) sfdr = 85.4dbc 09977-009 figure 9. single-tone fft with f in = 9.7 mhz 0 ?20 ?40 ?60 ?80 ?100 ?120 06 10 20 30 40 50 amplitude (dbfs) frequency (mhz) 0 125msps 30.5mhz at ?1dbfs snr = 60.7db (61.7dbfs) sfdr = 86.3dbc 09977-010 figure 10. single-tone fft with f in = 30.5 mhz 0 ?20 ?40 ?60 ?80 ?100 ?120 06 10 20 30 40 50 amplitude (dbfs) frequency (mhz) 0 125msps 70.1mhz at ?1dbfs snr = 60.7db (61.7dbfs) sfdr = 86.5dbc 09977-011 figure 11. single-tone fft with f in = 70.1 mhz 0 ?20 ?40 ?60 ?80 ?100 ?120 06 10 20 30 40 50 amplitude (dbfs) frequency (mhz) 0 125msps 100.5mhz at ?1dbfs snr = 60.6db (61.6dbfs) sfdr = 85.2dbc 09977-012 figure 12. single-tone fft with f in = 100.5 mhz 0 ?20 ?40 ?60 ?80 ?100 ?120 06 10 20 30 40 50 amplitude (dbfs) frequency (mhz) 0 125msps 200.5mhz at ?1dbfs snr = 60.3db (61.3dbfs) sfdr = 83.0dbc 09977-013 figure 13. single-tone fft with f in = 200.5 mhz
ad9608 rev. 0 | page 18 of 40 avdd = 1.8 v, drvdd = 1.8 v, maximum sample rate, vin = ?1.0 dbfs differential input, 1.0 v internal reference, and dcs enabled , unless otherwise noted. 0 ?15 ?30 ?45 ?60 ?75 ?90 ?105 ?120 ?135 6 121824303642485460 frequency (mhz) amplitude (hz) 2f1?f2 2f2?f1 2f1 + f2 + 09977-067 figure 14. two-tone fft with f in1 = 29 mhz and f in2 = 32 mhz 50 55 60 65 70 75 80 85 90 95 100 0 50 100 150 200 250 snr/sfdr (dbfs/dbc) analog input frequency (mhz) snrfs sfdr 09977-035 figure 15. snr/sfdr vs. input freque ncy (ain) with 2 v p-p full scale 0 20 40 60 80 100 120 5 25 45 65 85 105 125 snr/sfdr (dbfs/dbc) sample rate (msps) sfdr (dbc) snr (dbfs) 09977-031 figure 16. snr/sfdr vs. sample rate with ain = 9.7 mhz ?92 ?82 ?72 ?62 ?52 ?42 ?32 ?22 ?12 ? 2 ?70 ?60 ?50 ?40 ?30 ?20 ?10 input amplitude (dbfs) imd3 (dbc) sfdr(dbc) sfdr(dbfs) imd3 (dbfs) 09977-022 figure 17. two-tone sfdr/imd3 vs. input amplitude (ain) with f in1 = 29 mhz and f in2 = 32 mhz 0 10 20 30 40 50 60 70 80 90 ?60 ?50 ?40 ?30 ?20 ?10 0 snr/sfdr (dbc and dbfs) input amplitude (dbfs) snrfs sfdr snr sfdrfs 09977-033 figure 18. snr/sfdr vs. input amplitude (ain) with f in = 9.7 mhz 0 20 40 60 80 100 120 5 25 45 65 85 105 125 snr/sfdr (dbfs/dbc) sample rate (msps) sfdr (dbc) snr (dbfs) 09977-032 figure 19. snr/sfdr vs. sample rate with ain = 70 mhz
ad9608 rev. 0 | page 19 of 40 avdd = 1.8 v, drvdd = 1.8 v, maximum sample rate, vin = ?1.0 dbfs differential input, 1.0 v internal reference, and dcs enabled , unless otherwise noted. ?1.0 ?0.5 0 0.5 1.0 0 500 1000 dnl error (lsb) output code 09977-021 figure 20. dnl error with f in = 9.7 mhz 0 200 400 600 800 1,000 1,200 n ? 3 n ? 2 n ? 1 n n + 1 n + 2 n + 3 number of hits (thousands) output code 09977-034 figure 21. shorted input histogram ?2.0 ?1.5 ?1.0 ?0.5 0 0.5 1.0 1.5 2.0 0 200 400 600 800 1000 inl error (lsb) output code 09977-020 figure 22. inl error with f in = 9.7 mhz
ad9608 rev. 0 | page 20 of 40 ad9608-105 avdd = 1.8 v, drvdd = 1.8 v, maximum sample rate, vin = ?1.0 dbfs differential input, 1.0 v internal reference, and dcs enabled , unless otherwise noted. 0 ?20 ?40 ?60 ?80 ?100 ?120 05 10 20 30 40 amplitude (dbfs) frequency (mhz) 0 105msps 9.7mhz at ?1dbfs snr = 60.7db (61.7dbfs) sfdr = 84.9dbc 09977-014 figure 23. single-tone fft with f in = 9.7 mhz 0 ?20 ?40 ?60 ?80 ?100 ?120 05 10 20 30 40 amplitude (dbfs) frequency (mhz) 0 105msps 30.5mhz at ?1dbfs snr = 60.6db (61.6dbfs) sfdr = 84.5dbc 09977-015 figure 24. single-tone fft with f in = 30.5 mhz 0 ?20 ?40 ?60 ?80 ?100 ?120 05 10 20 30 40 amplitude (dbfs) frequency (mhz) 0 105msps 70.1mhz at ?1dbfs snr = 60.7db (61.7dbfs) sfdr = 86.8dbc 09977-016 figure 25. single-tone fft with f in = 70.1 mhz 0 ?20 ?40 ?60 ?80 ?100 ?120 05 10 20 30 40 amplitude (dbfs) frequency (mhz) 0 105msps 100.5mhz at ?1dbfs snr = 60.7db (61.7dbfs) sfdr = 85.9dbc 09977-017 figure 26. single-tone fft with f in = 100.5 mhz 0 ?20 ?40 ?60 ?80 ?100 ?120 05 10 20 30 40 amplitude (dbfs) frequency (mhz) 0 105msps 200.5mhz at ?1dbfs snr = 60.3db (61.3dbfs) sfdr = 85.9dbc 09977-018 figure 27. single-tone fft with f in = 200.5 mhz
ad9608 rev. 0 | page 21 of 40 avdd = 1.8 v, drvdd = 1.8 v, maximum sample rate, vin = ?1.0 dbfs dierential input, 1.0 v internal reference, and dcs enabled, unless otherwise noted. 50 55 60 65 70 75 80 85 90 95 100 050 100 150 200 250 snr/sfdr (dbfs/dbc) analog input frequency (mhz) snrfs sfdr 09977-029 figure 28. snr/sfdr vs. input freque ncy (ain) with 2 v p-p full scale 0 20 40 60 80 100 120 5 152535455565758595105 snr/sfdr (dbfs/dbc) sample rate (msps) sfdr (dbc) snr (dbfs) 09977-026 figure 29. snr/sfdr vs. sample rate with ain = 9.7 mhz ?1.0 ?0.5 0 0.5 1.0 0 dnlerror (lsb) output code 1000 500 09977-019 figure 30. dnl error with f in = 9.7 mhz 0 10 20 30 40 50 60 70 80 90 ?60 ?50 ?40 ?30 ?20 ?10 0 snr/sfdr (dbc and dbfs) input amplitude (dbfs) snrfs sfdr snr sfdrfs 09977-028 figure 31. snr/sfdr vs. input amplitude (ain) with f in = 9.7 mhz 0 20 40 60 80 100 120 5 152535455565758595105 snr/sfdr (dbfs/dbc) sample rate (msps) sfdr (dbc) snr (dbfs) 09977-027 figure 32. snr/sfdr vs. sample rate with ain = 70 mhz ?1.0 ?0.5 0 0.5 1.0 0 200 400 600 800 1000 inl error (lsb) output code 09977-025 figure 33. inl error with f in = 9.7 mhz
ad9608 rev. 0 | page 22 of 40 equivalent circuits a v dd vinx 09977-039 figure 34. equivalent analog input circuit clk+ clk? 0.9v 15k? 5 ? 5 ? 15k? 09977-040 figure 35. equivalent clock input circuit drvdd pad 09977-047 figure 36. equivalent digital output circuit 30k? 30k? s dio/dcs 350? a v dd drvdd 09977-042 figure 37. equivalent sdio/dcs input circuit 350? dr v dd 30k? sclk/dfs, sync, oeb, and pdwn 09977-045 figure 38. equivalent sclk/dfs, sy nc, oeb, and pdwn input circuit s ense 375? a v dd 09977-043 figure 39. equivalent sense circuit 30k? csb 350? avdd dr v dd 09977-044 figure 40. equivalent csb input circuit 7.5k ? v ref 375? a v dd 09977-048 figure 41. equivalent vref circuit
ad9608 rev. 0 | page 23 of 40 theory of operation the ad9608 dual adc design can be used for diversity reception of signals, where the adcs are operating identically on the same carrier but from two separate antennae. the adcs can also be operated with independent analog inputs. the user can sample any f s /2 frequency segment from dc to 200 mhz, using appropriate low-pass or band-pass filtering at the adc inputs with little loss in adc performance. operation to 300 mhz analog input is permitted but occurs at the expense of increased adc noise and distortion. in nondiversity applications, the ad9608 can be used as a base- band or direct downconversion receiver, where one adc is used for i input data and the other is used for q input data. synchronization capability is provided to allow synchronized timing between multiple channels or multiple devices. programming and control of the ad9608 is accomplished using a 3-bit spi-compatible serial interface. adc architecture the ad9608 architecture consists of a multistage, pipelined adc. each stage provides sufficient overlap to correct for flash errors in the preceding stage. the quantized outputs from each stage are combined into a final 10-bit result in the digital correction logic. the pipelined architecture permits the first stage to operate with a new input sample while the remaining stages operate with preceding samples. sampling occurs on the rising edge of the clock. each stage of the pipeline, excluding the last, consists of a low resolution flash adc connected to a switched-capacitor dac and an interstage residue amplifier (for example, a multiplying digital-to-analog converter (mdac)). the residue amplifier magnifies the difference between the reconstructed dac output and the flash input for the next stage in the pipeline. one bit of redundancy is used in each stage to facilitate digital correction of flash errors. the last stage consists of a flash adc. the output staging block aligns the data, corrects errors, and passes the data to the cmos/lvds output buffers. the output buffers are powered from a separate (drvdd) supply, allowing digital output noise to be separated from the analog core. during power-down, the output buffers go into a high impedance state. analog input considerations the analog input to the ad9608 is a differential switched- capacitor circuit designed for processing differential input signals. this circuit can support a wide common-mode range while maintaining excellent performance. by using an input common-mode voltage of midsupply, users can minimize signal-dependent errors and achieve optimum performance. ss c par c sample c sample c par vin?x h ss h h vin+x h 09977-049 figure 42. switched-cap acitor input circuit the clock signal alternately switches the input circuit between sample-and-hold mode (see figure 42 ). when the input circuit is switched to sample mode, the signal source must be capable of charging the sample capacitors and settling within one-half of a clock cycle. a small resistor in series with each input can help reduce the peak transient current injected from the output stage of the driving source. in addition, low q inductors or ferrite beads can be placed on each leg of the input to reduce high differential capacitance at the analog inputs and, therefore, achieve the maximum bandwidth of the adc. such use of low q inductors or ferrite beads is required when driving the converter front end at high if frequencies. either a shunt capacitor or two single-ended capacitors can be placed on the inputs to provide a matching passive network. this ultimately creates a low-pass filter at the input to limit unwanted broadband noise. see the an-742 application note, the an-827 application note, and the analog dialogue article transformer-coupled front-end for wideband a/d converters (volume 39, april 2005) for more information. in general, the precise values depend on the application.
ad9608 rev. 0 | page 24 of 40 input common mode the analog inputs of the ad9608 are not internally dc-biased. therefore, in ac-coupled applications, the user must provide a dc bias externally. setting the device so that vcm = avdd/2 is recommended for optimum performance, but the device can function over a wider range with reasonable performance, as shown in figure 43 . an on-board, common-mode voltage reference is included in the design and is available from the vcm pin. the vcm pin must be decoupled to ground by a 0.1 f capacitor, as described in the applications information section. 0 10 20 30 40 50 60 70 80 90 100 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 snr/sfdr (dbfs/dbc) input common-mode voltage (v) sfdr (dbc) snr (dbfs) 09977-056 figure 43. snr/sfdr vs. input common-mode voltage, f in = 70 mhz, f s = 125 msps differential input configurations optimum performance is achieved while driving the ad9608 in a differential input configuration. for baseband applications, the ad8138, ada4937-2 , and ada4938-2 differential drivers provide excellent performance and a flexible interface to the adc. the output common-mode voltage of the ada4938-2 is easily set with the vcm pin of the ad9608 (see figure 44 ), and the driver can be configured in a sallen-key filter topology to provide band limiting of the input signal. avdd vin 76.8 ? 120 ? 0.1f 33 ? 33 ? 10pf 200 ? 200 ? 90 ? ada4938 adc vin?x vin+x vcm 09977-050 figure 44. differential input configuration using the ada4938-2 for baseband applications below ~10 mhz where snr is a key parameter, differential transformer coupling is the recommended input configuration (see figure 45 ). to bias the analog input, the vcm voltage can be connected to the center tap of the secondary winding of the transformer. 2v p-p 49.9 ? 0.1f r r c adc vcm vin+x vin?x 09977-051 figure 45. differential transformer-coupled configuration the signal characteristics must be considered when selecting a transformer. most rf transformers saturate at frequencies that are below a few megahertz (mhz). excessive signal power can also cause core saturation, which leads to distortion. at input frequencies in the second nyquist zone and above, the noise performance of most amplifiers is not adequate to achieve the true snr performance of the ad9608 . for applications above ~10 mhz where snr is a key parameter, differential double balun coupling is the recommended input configuration (see figure 46 ). an alternative to using a transformer-coupled input at frequencies in the second nyquist zone is to use the ad8352 differential driver (see figure 47 ). see the ad8352 data sheet for more information. adc r 0.1f 0.1f 2v p-p vcm c r 0.1f s 0.1f 25 ? 25 ? s p a p vin+x vin?x 09977-053 figure 46. differential double balun input configuration ad8352 0 ? 0 ? c d r d r g 0.1f 0.1f 0.1f 0.1f 16 1 2 3 4 5 11 0.1f 0.1f 10 14 0.1f 8, 13 v cc 200 ? 200 ? analog input analog input r r c adc vcm vin+x vin?x 09977-054 figure 47. differential input configuration using the ad8352
ad9608 rev. 0 | page 25 of 40 in any configuration, the value of shunt capacitor c is dependent on the input frequency and source impedance and may need to be reduced or removed. tabl e 11 displays the suggested values to set the rc network. however, these values are dependent on the input signal and should be used only as a starting guide. table 11. example rc network frequency range (mhz) r series ( each) c differential (pf) 0 to 70 33 22 70 to 200 125 open single-ended input configuration a single-ended input can provide adequate performance in cost-sensitive applications. in this configuration, sfdr and distortion performance degrade due to the large input common- mode swing. if the source impedances on each input are matched, there should be little effect on snr performance. figure 48 shows a typical single-ended input configuration. 1v p-p r r c 49.9 ? 0.1f 10f 10f 0.1f avdd 1k ? 1k ? 1k ? 1k ? adc a v dd vin+x vin?x 09977-052 figure 48. single-ended input configuration voltage reference a stable and accurate 1.0 v voltage reference is built into the ad9608 . the vref pin can be configured using either the internal 1.0 v reference or an externally applied 1.0 v reference voltage. the various reference modes are summarized in the sections that follow. the reference decoupling section describes the best practices pcb layout of the reference. internal reference connection a comparator within the ad9608 detects the potential at the sense pin and configures the reference into two possible modes, which are summarized in table 12 . if sense is grounded, the reference amplifier switch is connected to the internal resistor divider (see figure 49 ), setting vref to 1.0 v. vref sense 0.5v adc select logic 0.1f 1.0f vin?a/vin?b vin+a/vin+b adc core 09977-055 figure 49. internal reference configuration if the internal reference of the ad9608 is used to drive multiple converters to improve gain matching, the loading of the reference by the other converters must be considered. figure 50 shows how the internal reference voltage is affected by loading. 0 ?3.0 02 load current (ma) reference voltage error (%) . 0 ?0.5 ?1.0 ?1.5 ?2.0 ?2.5 0.2 0.4 0.6 0.8 1.0 1.4 1.6 1.8 1.2 internal v ref = 1.00v 09977-057 figure 50. v ref accuracy vs. load current table 12. reference configuration summary selected mode sense voltage (v) resulting vref (v) resulting differential span (v p-p) fixed internal reference agnd to 0.2 1.0 internal 2.0 fixed external reference avdd 1.0 applied to external vref pin 2.0
ad9608 rev. 0 | page 26 of 40 external reference operation the use of an external reference may be necessary to enhance the gain accuracy of the adc or improve thermal drift charac- teristics. figure 51 shows the typical drift characteristics of the internal reference in 1.0 v mode. 4 3 2 1 0 ?1 ?2 ?3 ?4 ?5 ?6 ?40 ?20 0 20 40 60 80 temperature (c) v ref error (mv) v ref error (mv) 09977-066 figure 51. typical v ref drift when the sense pin is tied to avdd, the internal reference is disabled, allowing the use of an external reference. an internal reference buffer loads the external reference with an equivalent 7.5 k load (see figure 41 ). the internal buffer generates the positive and negative full-scale references for the adc core. therefore, the external reference must be limited to a maximum of 1.0 v. clock input considerations for optimum performance, clock the ad9608 sample clock inputs, clk+ and clk?, with a differential signal. the signal is typically ac-coupled into the clk+ and clk? pins via a transformer or capacitors. these pins are biased internally (see figure 52 ) and require no external bias. 0.9v a v dd 2pf 2pf clk? clk+ 09977-058 figure 52. equivalent clock input circuit clock input options the ad9608 has a very flexible clock input structure. the clock input can be a cmos, lvds, lvpecl, or sine wave signal. regardless of the type of signal being used, clock source jitter is of the most concern, as described in the jitter considerations section. figure 53 and figure 54 show two preferred methods for clock- ing the ad9608 (at clock rates up to 1 ghz prior to internal clk divider). a low jitter clock source is converted from a single- ended signal to a differential signal using either an rf transformer or an rf balun. the rf balun configuration is recommended for clock frequencies between 125 mhz and 1 ghz, and the rf transformer is recom- mended for clock frequencies from 10 mhz to 200 mhz. the back-to-back schottky diodes across the transformer/balun secondary limit clock excursions into the ad9608 to approxi- mately 0.8 v p-p differential. this limit helps prevent the large voltage swings of the clock from feeding through to other portions of the ad9608 while preserving the fast rise and fall times of the signal that are critical to a low jitter performance. 0.1f 0.1f 0.1f 0.1f schottky diodes: hsms2822 clock input 50 ? 100? clk? clk+ adc mini-circuits ? adt1-1wt, 1:1 z xfmr 09977-059 figure 53. transformer-coupled differential clock (up to 200 mhz) 0.1f 0.1f 1nf c lock input 1nf 50? clk? clk+ schottky diodes: hsms2822 adc 09977-060 figure 54. balun-coupled differential clock (up to 1 ghz)
ad9608 rev. 0 | page 27 of 40 if a low jitter clock source is not available, another option is to ac couple a differential pecl signal to the sample clock input pins, as shown in figure 55 . the ad9510/ ad9511 / ad9512 / ad9513/ ad9514 / ad9515 / ad9516/ ad9517 clock drivers offer excellent jitter performance. 100 ? 0.1f 0.1f 0.1f 0.1f 240 ? 240 ? 50k ? 50k ? clk? clk+ clock input clock input adc ad951x pecl driver 09977-061 figure 55. differential pecl sample clock (up to 1 ghz) a third option is to ac couple a differential lvds signal to the sample clock input pins, as shown in figure 56 . the ad9510 / ad9511/ ad9512 / ad9513 / ad9514/ ad9515 / ad9516/ ad9517 clock drivers offer excellent jitter performance. 100 ? 0.1f 0.1f 0.1f 0.1f 50k ? 50k ? clk? clk+ adc c lock input clock input ad951x lvds driver 09977-062 figure 56. differential lvds sample clock (up to 1 ghz) in some applications, it may be acceptable to drive the sample clock inputs with a single-ended 1.8 v cmos signal. in such applications, drive the clk+ pin directly from a cmos gate, and bypass the clk? pin to ground with a 0.1 f capacitor (see figure 57 ). optional 100? 0.1f 0.1f 0.1f 50? 1 1 50? resistor is optional. clk? clk+ adc v cc 1k? 1k? clock input ad951x cmos driver 09977-063 figure 57. single-ended 1.8 v cm os input clock (up to 200 mhz) input clock divider the ad9608 contains an input clock divider with the ability to divide the input clock by integer values between 1 and 8. the ad9608 clock divider can be synchronized using the external sync input. bit 1 and bit 2 of register 0x3a allow the clock divider to be resynchronized on every sync signal or only on the first sync signal after the register is written. a valid sync causes the clock divider to reset to its initial state. this synchronization feature allows multiple parts to have their clock dividers aligned to guarantee simultaneous input sampling. clock duty cycle typical high speed adcs use both clock edges to generate a variety of internal timing signals and, as a result, may be sensitive to clock duty cycle. a 5% tolerance is commonly required on the clock duty cycle to maintain dynamic performance characteristics. the ad9608 contains a duty cycle stabilizer (dcs) that retimes the nonsampling (falling) edge, providing an internal clock signal with a nominal 50% duty cycle. this allows the user to provide a wide range of clock input duty cycles without affecting the performance of the ad9608 . noise and distortion perform- ance are nearly flat for a wide range of duty cycles with the dcs on, as shown in figure 58 . jitter in the rising edge of the input is still of concern and is not easily reduced by the internal stabilization circuit. the duty cycle control loop does not function for clock rates less than 20 mhz, nominally. the loop has a time constant associated with it that must be considered in applications in which the clock rate can change dynamically. a wait time of 1.5 s to 5 s is required after a dynamic clock frequency increase or decrease before the dcs loop is relocked to the input signal. 40 45 50 55 60 65 70 35 40 45 50 55 60 65 snr (dbfs) positive duty cycle (%) dcs on dcs off 09977-036 figure 58. snr vs. dcs on/off
ad9608 rev. 0 | page 28 of 40 jitter considerations high speed, high resolution adcs are sensitive to the quality of the clock input. the degradation in snr from the low fre- quency snr (snr lf ) at a given input frequency (f input ) due to jitter (t jrms ) can be calculated by snr hf = ?10 log[(2 f input t jrms ) 2 + 10 ] )10/( lf snr ? in the previous equation, the rms aperture jitter represents the clock input jitter specification. if undersampling applications are particularly sensitive to jitter, as illustrated in figure 59 . 80 75 70 65 60 55 50 45 1 10 100 1k frequency (mhz) snr (dbfs) 0.5ps 0.2ps 0.05ps 1.0ps 1.5ps 2.0ps 2.5ps 3.0ps 09977-065 figure 59. snr vs. input frequency and jitter the clock input should be treated as an analog signal in cases where aperture jitter may affect the dynamic range of the ad9608. to avoid modulating the clock signal with digital noise, keep power supplies for clock drivers separate from the adc output driver supplies. low jitter, crystal-controlled oscillators make the best clock sources. if the clock is generated from another type of source (by gating, dividing, or another method), it should be retimed by the original clock at the last step. for more information, see the an-501 application note and the an-756 application note, available on www.analog.com . channel/chip synchroniation the ad9608 has a sync input that offers the user flexible synchronization options for synchronizing sample clocks across multiple adcs. the input clock divider can be enabled to synchronize on a single occurrence of the sync signal or on every occurrence. the sync input is internally synchronized to the sample clock; however, to ensure that there is no timing uncertainty between multiple parts, the sync input signal should be externally synchronized to the input clock signal, meeting the setup and hold times shown in table 5 . drive the sync input using a single-ended cmos-type signal. power dissipation and standby mode as shown in figure 60 , the analog core power dissipated by the ad9608 is proportional to its sample rate. the digital power dissipation of the cmos outputs are determined primarily by the strength of the digital drivers and the load on each output bit. the maximum drvdd current (i drvdd ) can be calculated as i drvdd = v drvdd c load f clk n where n is the number of output bits (22, in the case of the ad9608). this maximum current occurs when every output bit switches on every clock cycle, that is, a full-scale square wave at the nyquist frequency of f clk /2. in practice, the drvdd current is estab- lished by the average number of output bits switching, which is determined by the sample rate and the characteristics of the analog input signal. reducing the capacitive load presented to the output drivers can minimize digital power consumption. the data in figure 60 was taken in cmos mode using the same operating conditions as those used for the power supplies and power consumption parameters in table 1 , with a 5 pf load on each output driver. 40 90 140 190 240 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 5 25456585105125 power (mw) supply current (ma) encode rate (msps) i avdd i drvdd total power 09977-030 figure 60. ad9608 -125 power and current vs. clock rate (1.8 v cmos output mode) 40 90 140 190 240 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 5 152535455565758595105 power (mw) supply current (ma) encode rate (msps) i avdd i drvdd total power 09977-023 figure 61. ad9608 -105 power and current vs. clock rate (1.8 v cmos output mode)
ad9608 rev. 0 | page 29 of 40 the ad9608 is placed in power-down mode either by the spi port or by asserting the pdwn pin high. in this state, the adc typically dissipates <2 mw. during power-down, the output drivers are placed in a high impedance state. asserting the pdwn pin low returns the ad9608 to its normal operating mode. note that pdwn is referenced to the digital output driver supply (drvdd) and should not exceed that supply voltage. low power dissipation in power-down mode is achieved by shutting down the reference, reference buffer, biasing networks, and clock. internal capacitors are discharged when entering power- down mode and then must be recharged when returning to normal operation. as a result, wake-up time is related to the time spent in power-down mode, and shorter power-down cycles result in proportionally shorter wake-up times. when using the spi port interface, the user can place the adc in power-down mode or standby mode. standby mode allows the user to keep the internal reference circuitry powered when faster wake-up times are required. see the memory map section for more details. digital outputs the ad9608 output drivers can be configured to interface with either 1.8 v cmos or 1.8 v lvds logic families. the default output mode is cmos, with each channel output on separate busses as shown in figure 2 . in cmos output mode, the cmos output drivers are sized to provide sufficient output current to drive a wide variety of logic families. however, large drive currents tend to cause current glitches on the supplies and may affect converter performance. applications requiring the adc to drive large capacitive loads or large fanouts may require external buffers or latches. the cmos output can also be configured for interleaved cmos output mode via the spi port. in interleaved cmos mode, the data for both channels is output onto a single output bus to reduce the total number of traces required. the timing diagram for interleaved cmos output mode is shown in figure 3 . the interleaved cmos output mode is enabled globally onto both output channels via bit 5 in register 0x14. the unused channel output can be disabled by selecting the appropriate bit (bit 1 or bit 0) in register 0x05 and then writing a 1 to the local (channel- specific) output port disable bit (bit 4) in register 0x14. the output data format can be selected to be either offset binary or twos complement by setting the sclk/dfs pin when operating in the external pin mode (see table 13 ). as detailed in the an-877 application note, interfacing to high speed adcs via spi , the data format can be selected for offset binary, twos complement, or gray code when using the spi control. table 13. sclk/dfs mode selection (external pin mode) voltage at pin sclk/dfs sdio/dcs agnd offset binary (default) dcs disabled drvdd twos complement dcs enabled (default) digital output enable function (oeb) the ad9608 has a flexible three-state ability for the digital output pins. the three-state mode is enabled through the spi interface and can subsequently be controlled using the oeb pin or through the spi. once enabled via the spi (bit 7) in register 0x101 and the oeb pin is low, the output data drivers and dcos are enabled. if the oeb pin is high, the output data drivers and dcos are placed in a high impedance state. this oeb function is not intended for rapid access to the data bus. note that oeb is referenced to the digital output driver supply (drvdd) and should not exceed that supply voltage. when using the spi interface, the data outputs and dco of each channel can be independently three-stated by using the output port disable bit (bit 4) in register 0x14. timing the ad9608 provides latched data with a pipeline delay of 16 clock cycles. data outputs are available one propagation delay (t pd ) after the rising edge of the clock signal. minimize the length of the output data lines and loads placed on them to reduce transients within the ad9608 . these transients can degrade converter dynamic performance. the lowest typical conversion rate of the ad9608 is 10 msps. at clock rates below 10 msps, dynamic performance can degrade. data clock output (dco) the ad9608 provides two data clock output (dco) signals intended for capturing the data in an external register. in cmos output mode, the data outputs are valid on the rising edge of dco, unless the dco clock polarity has been changed via the spi. in lvds output mode, the dco and data output switching edges are closely aligned. additional delay can be added to the dco output using spi register 0x17 to increase the data setup time. in this case, the channel a output data is valid on the rising edge of dco, and the channel b output data is valid on the falling edge of dco. see figure 2 , figure 3 , and figure 4 for a graphical timing description of the output modes. table 14. output data format input (v) condition (v) offset binary output mode twos complement mode or vin+ ? vin? < ?vref ? 0.5 lsb 00 0000 0000 10 0000 0000 1 vin+ ? vin? = ?vref 00 0000 0000 10 0000 0000 0 vin+ ? vin? = 0 10 0000 0000 00 0000 0000 0 vin+ ? vin? = +vref ? 1.0 lsb 11 1111 1111 01 1111 1111 0 vin+ ? vin? > +vref ? 0.5 lsb 11 1111 1111 01 1111 1111 1
ad9608 rev. 0 | page 30 of 40 built-in self-test (bist) and output test the ad9608 includes a built-in test feature designed to enable verification of the integrity of each channel, as well as to facilitate board level debugging. a built-in self-test (bist) feature that verifies the integrity of the digital datapath of the ad9608 is included. various output test options are also provided to place predictable values on the outputs of the ad9608 . built-in self-test (bist) the bist is a thorough test of the digital portion of the selected ad9608 signal path. perform the bist test after a reset to ensure that the part is in a known state. during bist, data from an internal pseudorandom noise (pn) source is driven through the digital datapath of both channels, starting at the adc block output. at the datapath output, crc logic calculates a signature from the data. the bist sequence runs for 512 cycles and then stops. once completed, the bist compares the signature results with a predetermined value. if the signatures match, the bist sets bit 0 of register 0x24, signifying that the test passed. if the bist test fails, bit 0 of register 0x24 is cleared. the outputs are connected during this test, so the pn sequence can be observed as it runs. writing the value 0x05 to register 0x0e runs the bist. this enables bit 0 (bist enable) of register 0x0e and resets the pn sequence generator, bit 2 (initialize bist sequence) of register 0x0e. at the completion of the bist, bit 0 of register 0x24 is automatically cleared. the pn sequence can be continued from its last value by writing a 0 in bit 2 of register 0x0e. however, if the pn sequence is not reset, the signature calculation does not equal the predetermined value at the end of the test. at that point, the user needs to rely on verifying the output data. output test modes the output test options are described in table 18 at address 0x0d. when an output test mode is enabled, the analog section of the adc is disconnected from the digital back-end blocks and the test pattern is run through the output formatting block. some of the test patterns are subject to output formatting, and some are not. the pn generators from the pn sequence tests can be reset by setting bit 4 or bit 5 of register 0x0d. these tests can be performed with or without an analog signal (if present, the analog signal is ignored), but they do require an encode clock. for more information, see the an-877 application note, interfacing to high speed adcs via spi .
ad9608 rev. 0 | page 31 of 40 serial port interface (spi) the ad9608 serial port interface (spi) allows the user to configure the converter for specific functions or operations through a structured register space provided inside the adc. the spi gives the user added flexibility and customization, depending on the application. addresses are accessed via the serial port and can be written to or read from via the port. memory is organized into bytes that can be further divided into fields, which are docu- mented in the memory map section. for detailed operational information, see the an-877 application note, interfacing to high speed adcs via spi . configuration using the spi three pins define the spi of this adc: the sclk/dfs pin, the sdio/dcs pin, and the csb pin (see table 15 ). the sclk/dfs (a serial clock) is used to synchronize the read and write data presented from and to the adc. the sdio/dcs (serial data input/output) is a dual-purpose pin that allows data to be sent to and read from the internal adc memory map registers. the csb (chip select bar) is an active low control that enables or disables the read and write cycles. table 15. serial port interface pins pin function sclk serial clock. the serial shift clock input, which is used to synchronize serial interface reads and writes. sdio serial data input/output. a dual-purpose pin that typically serves as an input or an output, depending on the instruction being sent and the relative position in the timing frame. csb chip select bar. an active low control that gates the read and write cycles. the falling edge of the csb, in conjunction with the rising edge of the sclk, determines the start of the framing. an example of the serial timing and its definitions can be found in figure 62 and table 5 . other modes involving the csb are available. the csb can be held low indefinitely, which permanently enables the device; this is called streaming. the csb can stall high between bytes to allow for additional external timing. when csb is tied high, spi functions are placed in high impedance mode. this mode turns on any spi pin secondary functions. during an instruction phase, a 16-bit instruction is transmitted. data follows the instruction phase, and its length is determined by the w0 and w1 bits. in addition to word length, the instruction phase determines whether the serial frame is a read or write operation, allowing the serial port to be used both to program the chip and to read the contents of the on-chip memory. the first bit of the first byte in a multibyte serial data transfer frame indicates whether a read command or a write command is issued. if the instruction is a readback operation, performing a readback causes the serial data input/output (sdio) pin to change direction from an input to an output at the appropriate point in the serial frame. all data is composed of 8-bit words. data can be sent in msb- first mode or in lsb-first mode. msb first is the default on power-up and can be changed via the spi port configuration register. for more information about this and other features, see the an-877 application note, interfacing to high speed adcs via spi . don?t care don?t care don?t care don?t care sdio sclk csb t s t dh t clk t ds t h r/w w1 w0 a12 a11 a10 a9 a8 a7 d5 d4 d3 d2 d1 d0 t low t high 09977-046 figure 62. serial port interface timing diagram
ad9608 rev. 0 | page 32 of 40 hardware interface the pins described in table 15 comprise the physical interface between the user programming device and the serial port of the ad9608 . the sclk pin and the csb pin function as inputs when using the spi interface. the sdio pin is bidirectional, functioning as an input during write phases and as an output during readback. the spi interface is flexible enough to be controlled by either fpgas or microcontrollers. one method for spi configuration is described in detail in the an-812 application note, micro- controller-based serial port interface (spi) boot circuit . the spi port should not be active during periods when the full dynamic performance of the converter is required. because the sclk signal, the csb signal, and the sdio signal are typically asynchronous to the adc clock, noise from these signals can degrade converter performance. if the on-board spi bus is used for other devices, it may be necessary to provide buffers between this bus and the ad9608 to prevent these signals from transi- tioning at the converter inputs during critical sampling periods. some pins serve a dual function when the spi interface is not being used. when the pins are strapped to drvdd or ground during device power-on, they are associated with a specific function. table 16 describes the strappable functions supported on the ad9608. configuration without the spi in applications that do not interface to the spi control registers, the sdio/dcs pin, the sclk/dfs pin, and the pdwn pin serve as standalone cmos-compatible control pins. when the device is powered up, it is assumed that the user intends to use the pins as static control lines for the duty cycle stabilizer, output data format, and power-down feature control. in this mode, the csb chip select bar should be connected to avdd, which disables the serial port interface. when the device is in spi mode, the pdwn and oeb pins (if enabled) remain active. for spi control of output enable and power-down, the oeb and pdwn pins should be set to their default states. table 16. mode selection pin external voltage configuration sdio/dcs drvdd (default) duty cycle stabilizer enabled agnd duty cycle stabilizer disabled sclk/dfs drvdd twos complement enabled agnd (default) offset binary enabled oeb drvdd outputs in high impedance agnd (default) outputs enabled pdwn drvdd chip in power-down or standby agnd (default) normal operation spi accessible features table 17 provides a brief description of the general features that are accessible via the spi. these features are described in detail in the an-877 application note, interfacing to high speed adcs via spi . the ad9608 part-specific features are described in detail following table 18, the external memory map register table (see the memory map register descriptions section). table 17. features accessible using the spi feature name description mode allows user to set either power-down mode or standby mode clock allows user to access the dcs, set the clock divider, set the clock divider phase, and enable the sync offset allows user to digitally adjust the converter offset test i/o allows user to set test modes to have known data on output bits output mode allows user to set the output mode, including lvds output phase allows user to set the output clock polarity output delay allows user to vary the dco delay
ad9608 rev. 0 | page 33 of 40 memory map reading the memory map register table each row in the memory map register table has eight bit locations. the memory map is roughly divided into three sections: the chip configuration registers (address 0x00 to address 0x02); the channel index and transfer registers (address 0x05 and address 0xff) and the adc functions registers, including setup, control, and test (address 0x08 to address 0x102). the memory map register table (see tabl e 18 ) lists the default hexadecimal value for each hexadecimal address shown. the column with the heading bit 7 (msb) is the start of the default hexadecimal value given. for example, address 0x05, the device index register, has a hexadecimal default value of 0x03. this means that in address 0x05, bits[7:2] = 0, and bits[1:0] = 1. this setting is the default channel index setting. the default value results in both adc channels receiving the next write command. for more information about this function and others, see the an-877 application note, interfacing to high speed adcs via spi. this application note details the functions controlled by register 0x00 to register 0xff. the remaining registers are documented in the memory map register descriptions section. open locations all address and bit locations that are not included in table 18 are not currently supported for this device. unused bits of a valid address location should be written with 0s. writing to these locations is required only when part of an address location is open (for example, address 0x05). if the entire address location is open (for example, address 0x13), this address location should not be written to. default values after the ad9608 is reset, critical registers are loaded with default values. the default values for the registers are given in the memory map register table, table 18 . logic levels an explanation of logic level terminology follows: ? bit is set is synonymous with bit is set to logic 1 or writing logic 1 for the bit. ? clear a bit is synonymous with bit is set to logic 0 or writing logic 0 for the bit. channel-specific registers some channel setup functions, such as the signal monitor thresholds, can be programmed differently for each channel. in these cases, channel address locations are internally duplicated for each channel. these registers and bits are designated in table 1 8 as local. these local registers and bits can be accessed by setting the appropriate channel a or channel b bits in register 0x05. if both bits are set, the subsequent write affects the registers of both channels. in a read cycle, only channel a or channel b should be set to read one of the two registers. if both bits are set during an spi read cycle, the part returns the value for channel a. registers and bits designated as global in table 18 affect the entire part or the channel features for which independent settings are not allowed between channels.
ad9608 rev. 0 | page 34 of 40 memory map register table all address and bit locations that are not included in table 18 are not currently supported for this device. table 18. memory map registers addr (hex) register name bit 7 (msb) bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 (lsb) default value (hex) comments chip configurati on registers 0x00 spi port config (global) open lsb first soft reset 1 1 soft reset lsb first open 0x18 nibbles are mirrored so lsb-first mode or msb-first mode registers correctly, regardless of shift mode 0x01 chip id (global) 8-bit chip id, bits[7:0] ad9608 = 0x9c read only unique chip id used to differentiate devices; read only 0x02 chip grade (global) open speed grade id 100 = 105 msps 101 = 125 msps open open open open read only unique speed grade id used to differentiate devices; read only channel index and transfer registers 0x05 device index (global) open open open open open open channel b channel a 0x03 bits are set to determine which device on the chip receives the next write command; applies to local registers only 0xff transfer (global) open open open open open open open transfer 0x00 synchronous transfer of data from the master shift register to the slave adc functions 0x08 power modes (local) open open external power- down pin function 0 = pdwn 1 = standby open open open internal power-down mode 00 = normal operation 01 = full power-down 10 = standby 11 = digital reset 0x00 determines various generic modes of chip operation 0x09 global clock (global) open open open ope n open open open duty cycle stabilizer 0 = disabled 1 = enabled 0x01
ad9608 rev. 0 | page 35 of 40 addr (hex) register name bit 7 (msb) bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 (lsb) default value (hex) comments 0x0b clock divide (global) open open open open open clock divide ratio 000 = divide by 1 001 = divide by 2 010 = divide by 3 011 = divide by 4 100 = divide by 5 101 = divide by 6 110 = divide by 7 111 = divide by 8 0x00 the divide ratio is value plus 1 0x0c enhance- ment control (global) open open open open open chop mode 0 = disabled 1 = enabled open open 0x00 chop mode enabled if bit 2 = 1 0x0d test mode (local) user test mode control 00 = single pattern mode 01 = alternate continuous/repeat pattern mode 10 = single once pattern mode 11 = alternate once pattern mode reset pn long gen reset pn short gen output test mode 0000 = off (default) 0001 = midscale short 0010 = positive fs 0011 = negative fs 0100 = alternating checkerboard 0101 = pn long sequence 0110 = pn short sequence 0111 = one/zero word toggle 1000 = user test mode 1111 = ramp output 0x00 when this register is set, the test data is placed on the output pins in place of normal data 0x0e bist enable (global) open open open open open initialize bist sequence open bist enable 0x00 0x10 customer offset adjust (local) offset adjust in lsbs from +127 to ?128 (twos complement format) 0x00 0x14 output mode output port logic type (global) 00 = cmos, 1.8 v 10 = lvds, ansi 11 = lvds, reduced range output interleave enable (global) output port disable (local) open (global) output invert (local) output format 00 = offset binary 01 = twos complement 10 = gray code 0x00 configures the outputs and the format of the data 0x15 output adjust open open cmos 1.8 v dco drive strength 00 = 1 01 = 2 10 = 3 11 = 4 open open cmos 1.8 v data drive strength 00 = 1 01 = 2 10 = 3 11 = 4 0x00 determines cmos output drive strength properties 0x16 clock phase control (global) invert dco clock 0 = not inverted 1 = inverted open open open open input clock divider phase adjust relative to the encode clock 000 = no delay 001 = 1 input clock cycle 010 = 2 input clock cycles 011 = 3 input clock cycles 100 = 4 input clock cycles 101 = 5 input clock cycles 110 = 6 input clock cycles 111 = 7 input clock cycles 0x00 allows selection of clock delays into the input clock divider 0x17 output delay (global) dco clock delay 0 = disabled 1 = enabled open data delay 0 = disabled 1 = enabled open open delay selection 000 = 0.56 ns 001 = 1.12 ns 010 = 1.68 ns 011 = 2.24 ns 100 = 2.80 ns 101 = 3.36 ns 110 = 3.92 ns 111 = 4.48 ns 0x00 this sets the fine output delay of the output clock but does not change internal timing
ad9608 rev. 0 | page 36 of 40 addr (hex) register name bit 7 (msb) bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 (lsb) default value (hex) comments 0x18 vref select (global) open open open open open internal v ref digital adjustment 000 = 1.0 v p-p 001 = 1.14 v p-p 010 = 1.33 v p-p 011 = 1.6 v p-p 100 = 2.0 v p-p 0x04 select and/or adjust v ref 0x19 user pattern 1, lsb (global) b7 b6 b5 b4 b3 b2 b1 b0 0x00 user- defined pattern 1, lsb 0x1a user pattern 1, msb (global) b15 b14 b13 b12 b11 b10 b9 b8 0x00 user- defined pattern 1, msb 0x1b user pattern 2, lsb (global) b7 b6 b5 b4 b3 b2 b1 b0 0x00 user- defined pattern 2, lsb 0x1c user pattern 2, msb b15 b14 b13 b12 b11 b10 b9 b8 0x00 user- defined pattern 2, msbs 0x24 misr lsb misr lsb, bits[7:0] 0xff read only 0x25 misr msb misr msb, bits[15:8] 0xff read only 0x2a overrange control (global) open open open ope n open open open overrange output 0 = disabled 1 = enabled 0x01 overrange control settings 0x2e output assign (local) open open open ope n open open open 0 = adc a 1 = adc b (local) 0x00 = adc a 0x01 = adc b assign an adc to an output channel 0x3a sync control (global) open open open open open clock divider next sync only clock divider sync enable open 0x00 sets the global sync options 0x100 sample rate override open sample rate override enable open open open sample rate 011 = 80 msps 100 = 105 msps 101 = 125 msps 0x00 0x101 user i/o control register 2 output enable bar (oeb) pin enable open open open open open open disable sdio pull-down 0x00 oeb and sdio pin controls 0x102 user i/o control register 3 open open open open vcm power-down open 0x00
ad9608 rev. 0 | page 37 of 40 memory map register descriptions for additional information about functions controlled in register 0x00 to register 0xff, see the an-877 application note, interfacing to high speed adcs via spi . power modes (register 0x08) bitsopen bit external power-down pin function if set, the external pdwn pin initiates power-down mode. if clear, the external pdwn pin initiates standby mode. bits[4:2]open bits[1:0]internal power-down mode in normal operation (bits[1:0] = 00), both adc channels are active. in power-down mode (bits[1:0] = 01), the digital data path clocks are disabled while the digital data path is reset. outputs are disabled. in standby mode (bits[1:0] = 10), the digital data path clocks and the outputs are disabled. during a digital reset (bits[1:0] = 11), the digital data path clocks are disabled while the digital data path is held in reset. the outputs are enabled in this state. for optimum performance, it is recom- mended that both adc channels be reset simultaneously. this is accomplished by ensuring that both channels are selected via register 0x05 prior to issuing the digital reset instruction. enhancement control (register 0x0c) bits3open bit 2chop mode for applications that are sensitive to offset voltages and other low frequency noise, such as homodyne or direct-conversion receivers, chopping in the first stage of the ad9628 is a feature that can be enabled by setting bit 2. in the frequency domain, chopping translates offsets and other low frequency noise to f clk /2 where it can be filtered. bits[1:0]open output mode (register 0x14) bitsoutput port logic type 00 = cmos, 1.8 v 10 = lvds, ansi 11 = lvds, reduced range bit 5output interleave enable for lvds outputs, setting bit 5 enables interleaving. channel a is sent coincident with a high dco clock, and channel b is coincident with a low dco clock. clearing bit 5 disables the interleaving feature. channel a is sent on least significant bits (lsbs), and channel b is sent on most significant bits (msbs). the even bits are sent coincident with a high dco clock, and the odd bits are sent coincident with a low dco clock. for cmos outputs, setting bit 5 enables interleaving in cmos ddr mode. on adc output port a, channel a is sent coincident with a low dco clock, and channel b is coincident with a high dco clock. on adc output port b, channel b is sent coincident with a low dco clock, and channel a is coincident with a high dco clock. clearing bit 5 disables the interleaving feature, and data is output in cmos sdr mode. channel a is sent to port a, and channel b is sent to port b. bit 4output port disable setting bit 4 high disables the output port for the channels selected in bits[1:0] of the device index register (register 0x05). bit 3open bit 2output invert setting bit 2 high inverts the output port data for the channels selected in bits[1:0] of the device index register (register 0x05). bits[1:0]output format 00 = offset binary 01 = twos complement 10 = gray code sync control (register 0x3a) bits3open bit 2clock divider ext sync only if the clock divider sync enable bit (address 0x3a, bit 1) is high, bit 2 allows the clock divider to sync to the first sync pulse it receives and to ignore the rest. the clock divider sync enable bit resets after it syncs. bit 1clock divider sync enable bit 1 gates the sync pulse to the clock divider. the sync signal is enabled when bit 1 is high. this is continuous sync mode. bit 0open transfer (register 0xff) all registers except register 0x100 are updated the moment they are written. setting bit 0 of this transfer register high initializes the settings in the adc sample rate override register (address 0x100). sample rate overri de (register 0x100) this register is designed to allow the user to downgrade the device. any attempt to upgrade the default speed grade results in a chip power-down. settings in this register are not initialized until bit 0 of the transfer register (register 0xff) is written high.
ad9608 rev. 0 | page 38 of 40 user i/o control 2 (register 0x101) bit 7oeb pin enable if the oeb pin enable bit (bit 7) is set, the oeb pin is enabled. if bit 7 is clear, the oeb pin is disabled (default). bits[6:1]open bit 0sdio pull-down bit 0 can be set to disable the internal 30 k pull-down on the sdio pin, which can be used to limit the loading when many devices are connected to the spi bus. user i/o control 3 (register 0x102) bits[7:4]open bit 3vcm power-down bit 3 can be set high to power down the internal vcm generator. this feature is used when applying an external reference. bits[2:0]open
ad9608 rev. 0 | page 39 of 40 applications information design guidelines before starting design and layout of the ad9608 as a system, it is recommended that the designer become familiar with these guidelines, which discuss the special circuit connections and layout requirements that are needed for certain pins. power and ground recommendations when connecting power to the ad9608 , it is recommended that two separate 1.8 v supplies be used. use one supply for analog (avdd); use a separate supply for the digital outputs (drvdd). for both avdd and drvdd, several different decoupling capa- citors should be used to cover both high and low frequencies. place these capacitors 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 ad9608 . with proper decoupling and smart partitioning of the pcb analog, digital, and clock sections, optimum performance is easily achieved. lvds operation the ad9608 defaults to cmos output mode on power-up. if lvds operation is desired, this mode must be programmed, using the spi configuration registers after power-up. when the ad9608 powers up in cmos mode with lvds termination resistors (100 ) on the outputs, the drvdd current can be higher than the typical value until the part is placed in lvds mode. this additional drvdd current does not cause damage to the ad9608 , but it should be taken into account when consid- ering the maximum drvdd current for the part. to avoid this additional drvdd current, the ad9608 outputs can be disabled at power-up by taking the pdwn pin high. after the part is placed into lvds mode via the spi port, the pdwn pin can be taken low to enable the outputs. exposed paddle thermal heat slug recommendations it is mandatory that the exposed paddle on the underside of the adc be connected to analog ground (agnd) to achieve the best electrical and thermal performance. a continuous, exposed (no solder mask) copper plane on the pcb should mate to the ad9608 exposed paddle, pin 0. the copper plane should have several vias to achieve the lowest possible resistive thermal path for heat dissipation to flow through the bottom of the pcb. these vias should be filled or plugged to prevent solder wicking through the vias, which can compromise the connection. to maximize the coverage and adhesion between the adc and the pcb, a silkscreen should be overlaid to partition the continuous plane on the pcb into several uniform sections. this provides several tie points between the adc and the pcb during the reflow process. using one continuous plane with no partitions guarantees only one tie point between the adc and the pcb. for detailed information about packaging and pcb layout of chip scale packages, see the an-772 application note, a design and manufacturing guide for the lead frame chip scale package (lfcsp) , at www.analog.com . vcm the vcm pin should be decoupled to ground with a 0.1 f capacitor. reference decoupling the vref pin should be externally decoupled to ground with a low esr, 1.0 f capacitor in parallel with a low esr, 0.1 f ceramic capacitor. spi port the spi port should not be active during periods when the full dynamic performance of the converter is required. because the sclk, csb, and sdio signals are typically asynchronous to the adc clock, noise from these signals can degrade converter performance. if the on-board spi bus is used for other devices, it may be necessary to provide buffers between this bus and the ad9608 to keep these signals from transitioning at the converter inputs during critical sampling periods.
ad9608 rev. 0 | page 40 of 40 outline dimensions compliant to jedec standards mo-220-vmmd-4 091707-c 6.35 6.20 sq 6.05 0.25 min top view 8.75 bsc sq 9.00 bsc sq 1 64 16 17 49 48 32 33 0.50 0.40 0.30 0.50 bsc 0.20 ref 12 max 0.80 max 0.65 typ 1.00 0.85 0.80 7.50 ref 0.05 max 0.02 nom 0.60 max 0.60 max exposed pad (bottom view) seating plane pin 1 indicator pin 1 indicator 0.30 0.23 0.18 for proper connection of the exposed pad, refer to the pin configuration and function descriptions section of this data sheet. figure 63. 64-lead lead frame chip scale package [lfcsp_vq] 9 mm 9 mm body, very thin quad (cp-64-4) dimensions shown in millimeters ordering guide model 1 temperature range package description package option ad9608bcpz-105 ?40c to +85c 64-lead lead frame chip scale package [lfcsp_vq] cp-64-4 AD9608BCPZ-125 ?40c to +85c 64-lead lead frame chip scale package [lfcsp_vq] cp-64-4 ad9608bcpzrl7-105 ?40c to +85c 64-lead lead fr ame chip scale package [lfcsp_vq] cp-64-4 ad9608bcpzrl7-125 ?40c to +85c 64-lead lead fr ame chip scale package [lfcsp_vq] cp-64-4 ad9608-125ebz evaluation board 1 z = rohs compliant part. ?2011 analog devices, inc. all rights reserved. trademarks and registered trademarks are the property of their respective owners. d09977-0-7/11(0)

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