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dual low power cmos analog front end with dsp microcomputer preliminary technical data ad5744 rev. pre 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 ?2006 analog devices, inc. all rights reserved. features complete quad, 14-bit digital-to-analog converters (dacs) programmable output range: 10 v, 10.2564 v, or 10.5263 v 1 lsb max inl error, 1 lsb max dnl error low noise: 60 nv/hz settling time: 10 s max integrated reference buffers output control during power-up/brownout programmable short-circuit protection simultaneous updating via ldac asynchronous clr to zero code digital gain adjust logic output control pins dsp-/microcontroller-compatible serial interface temperature range: ?40c to +85c i cmos? process technology 1 applications industrial automation open-/closed-loop servo control process control data acquisition systems automatic test equipment automotive test and measurement high accuracy instrumentation general description the ad5744 is a quad, 14-bit, serial input, bipolar voltage output digital-to-analog converter that operates from supply voltages of 11.4 v up to 16.5 v. nominal full-scale output range is 10 v. the ad5744 provides integrated output amplifiers, reference buffers and proprietary power-up/power- down control circuitry. the part also features a digital i/o port, which is programmed via the serial interface. the ad5744 incorporates digital gain adjust registers per channel. the ad5744 is a high performance converter that offers guaranteed monotonicity, integral nonlinearity (inl) of 1 lsb, low noise, and 10 s settling time. during power-up (when the supply voltages are changing), vout is clamped to 0 v via a low impedance path. the ad5744 uses a serial interface that operates at clock rates of up to 30 mhz and is compatible with dsp and microcontroller interface standards. double buffering allows the simultaneous updating of all dacs. the input coding is programmable to either twos complement or offset binary formats. the asynchronous clear function clears all dac registers to either bipolar zero or zero scale depending on the coding used. the ad5744 is ideal for both closed-loop servo control and open- loop control applications. the ad5744 is available in a 32-lead tqfp, and offers guaranteed specifications over the ?40c to +85c industrial temperature range. see figure 1 , the functional block diagram. table 1. related devices part no. description ad5744r ad5744 with internal voltage reference ad5764 complete quad, 16-bit, high accuracy, serial input, bipolar voltage output dacs ad5764r ad5764 with internal voltage reference 1 for analog systems designers within industrial/instrumentation equipment oems who need high performance ics at higher voltage levels, i cmos is a technology platform that enables the development of analog ics capable of 30 v and operating at 15 v supplies wh ile allowing dramatic reductions in power consumption and package size, and increased ac and dc performance.
ad5744 preliminary technical data rev. pre | page 2 of 32 table of contents features .............................................................................................. 1 applications ....................................................................................... 1 general description ......................................................................... 1 revision history ............................................................................... 2 functional block diagram .............................................................. 3 specifications ..................................................................................... 4 ac performance characteristic ...................................................... 6 timing characteristics ..................................................................... 7 absolute maximum ratings .......................................................... 10 esd caution ................................................................................ 10 pin configuration and function descriptions ........................... 11 te r m i no l o g y .................................................................................... 13 typical performance characteristics ........................................... 15 theory of operation ...................................................................... 20 dac architecture ....................................................................... 20 reference buffers ........................................................................ 20 serial interface ............................................................................ 20 simultaneous updating via ldac ........................................... 21 transfer function ....................................................................... 22 asynchronous clear ( clr ) ....................................................... 22 function register ....................................................................... 23 data register ............................................................................... 24 coarse gain register ................................................................. 24 fine gain register ...................................................................... 24 ad5744 features ............................................................................ 25 analog output control ............................................................. 25 programmable short-circuit protection ................................ 25 digital i/o port ........................................................................... 25 local ground offset adjust ...................................................... 25 applications information .............................................................. 26 typical operating circuit ......................................................... 26 layout guidelines ........................................................................... 27 galvanically isolated interface ................................................. 27 microprocessor interfacing ....................................................... 27 outline dimensions ....................................................................... 30 ordering guide .......................................................................... 30 revision history 3/06revision pre removed ad5744r, ad5764, and ad5764r .................universal changes to ordering guide .......................................................... 30
preliminary technical data ad5744 rev. pre | page 3 of 32 functional block diagram input reg c gain reg c offset reg c dac reg c 14 dac c input reg d gain reg d offset reg d dac reg d 14 dac d g1 g2 input reg b gain reg b offset reg b dac reg b 14 dac b input reg a gain reg a offset reg a dac reg a 14 14 dac a ldac refcd rstin rstout refab refgnd agndd voutd agndc voutc agndb voutb agnda vouta iscc reference buffers sdin sclk sync sdo d0 d1 bin/2scomp clr pgnd dv cc dgnd g1 g2 g1 g2 g1 g2 av dd av ss av dd input shift register and control logic voltage monitor and control reference buffers av ss ad5744 06063-001 figure 1. functional block diagram
ad5744 preliminary technical data rev. pre | page 4 of 32 specifications av dd = 11.4 v to 16.5 v, av ss = ?11.4 v to ?16.5 v, agnd = dgnd = refgnd = pgnd = 0 v; refab = refcd = 5 v; dv cc = 2.7 v to 5.25 v, r load = 10 k, c l = 200 pf. all specifications t min to t max , unless otherwise noted. table 2. parameter b grade 2 c grade 2 unit test conditions/comments accuracy outputs unloaded resolution 14 14 bits relative accuracy (inl) 2 1 lsb max differential nonlinearity 1 1 lsb max guaranteed monotonic bipolar zero error 2 2 mv max at 25c; error at other temperatures obtained using bipolar zero tc bipolar zero tc 3 2 2 ppm fsr/c max zero-scale error 2 2 mv max at 25c; error at other temperatures obtained using zero scale tc zero-scale tc 3 2 2 ppm fsr/c max gain error 0.02 0.02 % fsr max at 25c; error at other temperatures obtained using gain tc gain tc 3 2 2 ppm fsr/c max dc crosstalk 3 0.125 0.125 lsb max reference input 3 reference input voltage 5 5 v nominal 1% for specified performance dc input impedance 1 1 m min typically 100 m input current 10 10 a max typically 30 na reference range 1/7 1/7 v min/v max output characteristics 3 output voltage range 4 10.5263 10.5263 v min/v max av dd /av ss = 11.4 v, refin = 5v 14 14 v min/v max av dd /av ss = 16.5 v, refin = 7v output voltage drift vs. time 13 13 ppm fsr/500 hours typ 15 15 ppm fsr/1000 hours typ short circuit current 10 10 ma typ ri scc = 6 k, see figure 31 load current 1 1 ma max for specified performance capacitive load stability r l = 200 200 pf max r l = 10 k 1000 1000 pf max dc output impedance 0.3 0.3 max
preliminary technical data ad5744 rev. pre | page 5 of 32 parameter b grade 2 c grade 2 unit test conditions/comments digital inputs 3 dv cc = 2.7 v to 5.25 v, jedec compliant v ih , input high voltage 2 2 v min v il , input low voltage 0.8 0.8 v max input current 1 1 a max per pin pin capacitance 10 10 pf max per pin digital outputs (d0, d1, sdo) 3 output low voltage 0.4 0.4 v max dv cc = 5 v 5%, sinking 200 a output high voltage dv cc ? 1 dv cc ? 1 v min dv cc = 5 v 5%, sourcing 200 a output low voltage 0.4 0.4 v max dv cc = 2.7 v to 3.6 v, sinking 200 a output high voltage dv cc ? 0.5 dv cc ? 0.5 v min dv cc = 2.7 v to 3.6 v, sourcing 200 a high impedance leakage current 1 1 a max sdo only high impedance output capacitance 5 5 pf typ sdo only power requirements av dd /av ss 11.4/16.5 11.4/16.5 v min/v max dv cc 2.7/5.25 2.7/5.25 v min/v max power supply sensitivity 3 ?v out /?v dd ?85 ?85 db typ ai dd 3.5 3.5 ma/channel max outputs unloaded ai ss 2.75 2.75 ma/channel max outputs unloaded di cc 1.2 1.2 ma max v ih = dv cc , v il = dgnd, 750 a typ power dissipation 275 275 mw typ 12 v operation output unloaded 2 temperature range: -40c to +85c; typical at +25c. device functionality is guaranteed to +105c with degraded performance. 3 guaranteed by design and characterization; not production tested. 4 output amplifier headroom requirement is 1.4 v minimum.
ad5744 preliminary technical data rev. pre | page 6 of 32 ac performance characteristic av dd = 11.4 v to 16.5 v, av ss = ?11.4 v to ?16.5 v, agnd = dgnd = refgnd = pgnd = 0 v; refab = refcd = 5 v; dv cc = 2.7 v to 5.25 v, r load = 10 k, c l = 200 pf. all specifications t min to t max , unless otherwise noted. guaranteed by design and characterization, not production tested. table 3. parameter b grade c grade unit test conditions/comments dynamic performance 1 output voltage settling time 8 8 s typ full-scale step to 1 lsb 10 10 s max 2 2 s typ 512 lsb step settling slew rate 5 5 v/s typ digital-to-analog glitch energy 8 8 nv-s typ glitch impulse peak amplitude 25 25 mv max channel-to-channel isolation 80 80 db typ dac-to-dac crosstalk 8 8 nv-s typ digital crosstalk 2 2 nv-s typ digital feedthrough 2 2 nv-s typ effect of input bus activity on dac outputs output noise (0.1 hz to 10 hz) 0.025 0.025 lsb p-p typ output noise (0.1 hz to 100 khz) 45 45 v rms max 1/f corner frequency 1 1 khz typ output noise spectral density 60 60 nv/ hz typ measured at 10 khz complete system output noise spectral density 2 80 80 nv/ hz typ measured at 10 khz 1 guaranteed by design and characterization; not production tested. 2 includes noise contributions from integrated reference buffers, 14-bit dac and output amplifier.
preliminary technical data ad5744 rev. pre | page 7 of 32 timing characteristics av dd = 11.4 v to 16.5 v, av ss = ?11.4 v to ?16.5 v, agnd = dgnd = refgnd = pgnd = 0 v; refab = refcd = 5 v; dv cc = 2.7 v to 5.25 v, r load = 10 k, c l = 200 pf. all specifications t min to t max , unless otherwise noted. table 4. parameter 1 , , 2 3 limit at t min , t max unit description t 1 33 ns min sclk cycle time t 2 13 ns min sclk high time t 3 13 ns min sclk low time t 4 13 ns min sync falling edge to sclk falling edge setup time t 5 4 13 ns min 24 th sclk falling edge to sync rising edge t 6 40 ns min minimum sync high time t 7 2 ns min data setup time t 8 5 ns min data hold time t 9 1.4 s min sync rising edge to ldac falling edge (all dacs updated) 400 ns min sync rising edge to ldac falling edge (single dac updated) t 10 10 ns min ldac pulse width low t 11 500 ns max ldac falling edge to dac output response time t 12 10 s max dac output settling time t 13 10 ns min clr pulse width low t 14 2 s max clr pulse activation time t 15 5 , 6 25 ns max sclk rising edge to sdo valid t 16 20 ns min sync rising edge to sclk rising edge t 17 2 s min sync rising edge to dac output response time (ldac = 0) t 18 170 ns min ldac falling edge to sync rising edge 1 guaranteed by design and characterization; not production tested. 2 all input signals are specified with t r = t f = 5 ns (10% to 90% of dv cc ) and timed from a voltage level of 1.2 v. 3 see figure 2, figure 3, and figure 4. 4 standalone mode only. 5 measured with the load circuit of figure 5. 6 daisy-chain mode only.
ad5744 preliminary technical data rev. pre | page 8 of 32 db23 sclk sync sdin ldac ldac = 0 clr 12 24 db0 t 1 vout vout vout t 4 t 6 t 3 t 2 t 5 t 8 t 7 t 10 t 9 t 10 t 11 t 12 t 12 t 17 t 18 t 13 t 14 06063-002 figure 2. serial interface timing diagram ldac sdo sdin sync sclk 24 48 db23 db0 db23 db0 db23 input word for dac n undefined input word for dac n?1 input word for dac n db0 t 1 t 2 t 3 t 4 t 6 t 7 t 8 t 15 t 16 t 5 t 10 t 9 06063-003 figure 3. daisy chain timing diagram
preliminary technical data ad5744 rev. pre | page 9 of 32 sdo sdin s yn c sclk 24 48 db23 db0 db23 db0 db23 undefined nop condition db0 input word specifies register to be read selected register data clocked out 06063-004 figure 4. readback timing diagram 200a i ol 200a i oh v oh (min) or v ol (max) to output pin c l 50pf 06063-005 figure 5. load circuit for sdo timing diagram
ad5744 preliminary technical data rev. pre | page 10 of 32 absolute maximum ratings t a = 25c unless otherwise noted. transient currents of up to 100 ma do not cause scr latch-up. table 5. parameter rating 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 listed in the operational sections of this specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. av to agnd, dgnd ?0.3 v to +17 v dd av to agnd, dgnd +0.3 v to ?17 v ss dv to dgnd ?0.3 v to +7 v cc digital inputs to dgnd ?0.3 v to dv cc + 0.3 v or 7 v (whichever is less) digital outputs to dgnd ?0.3 v to dv + 0.3 v cc refin to agnd, pgnd ?0.3 v to av + 0.3v dd refout to agnd av to av ss dd temp av to av ss dd av to av vouta, voutb, voutc, voutd to agnd ss dd agnd to dgnd ?0.3 v to +0.3 v operating temperature range industrial ?40c to +85c storage temperature range ?65c to +150c junction temperature (t j max) 150c 32-lead tqfp ja thermal impedance 65c/w jc thermal impedance 12c/w reflow soldering peak temperature 220c time at peak temperature 10 sec to 40 sec esd caution esd (electrostatic discharge) sensitive device. electrosta tic charges as high as 4000 v readily accumulate on the human body and test equipment and can discharge without detection. although this product features proprietary esd protection circuitry, permanent dama ge may occur on devices subjected to high energy electrostatic discharges. therefore, proper esd pr ecautions are recommended to avoid performance degradation or loss of functionality.
preliminary technical data ad5744 rev. pre | page 11 of 32 pin configuration and fu nction descriptions nc = no connect s ync sclk sdin sdo clr ldac d1 d0 agnda vouta voutb agndb agndc voutc voutd agndd rstout rstin dgnd dv cc av dd pgnd iscc av ss bin/2scomp av dd av ss nc refgnd nc refcd refab 1 2 3 4 5 6 7 8 23 22 21 18 19 20 24 17 pin 1 9 10 11 12 13 14 15 16 32 31 30 29 28 27 26 25 ad5744 top view (not to scale) 06063-006 figure 6. pin configuration table 6. pin function descriptions pin no. mnemonic description 1 sync active low input. this is the frame synchronization signal for the serial interface. while sync is low, data is transferred in on the falling edge of sclk. 2 sclk serial clock input. data is clocked into the shift register on the falling edge of sclk. this operates at clock speeds up to 30 mhz. 3 sdin serial data input. data must be valid on the falling edge of sclk. 4 sdo serial data output. used to clock data from the serial register in daisy-chain or readback mode. 5 1 clr 1 negative edge triggered input. asserting th is pin sets the dac registers to 0x0000. 6 ldac load dac. logic input. this is used to update th e dac registers and consequently the analog outputs. when tied permanently low, th e addressed dac register is updated on the rising edge of sync . if ldac is held high during the write cycle, the dac in put register is updated but the output update is held off until the falling edge of ldac . in this mode, all analog outputs can be updated simultaneously on the falling edge of ldac . the ldac pin must not be left unconnected. 7, 8 d0, d1 d0 and d1 form a digital i/o port. the user can se t up these pins as inp uts or outputs that are configurable and readable over the serial interface. when configured as inputs, these pins have weak internal pull-ups to dv . when programmed as outputs, d0 and d1 are referenced by dv cc cc and dgnd. 9 rstout reset logic output. this is the output from the on-c hip voltage monitor used in the reset circuit. if desired, it can be used to control other system components. 10 rstin reset logic input. this input allows external access to the internal reset logic. applying a logic 0 to this input clamps the dac outputs to 0 v. in normal operation, rstin should be tied to logic 1. register values remain unchanged. 11 dgnd digital ground pin. 12 dv cc digital supply pin. voltage ranges from 2.7 v to 5.25 v. 13, 31 av dd positive analog supply pins. voltage ranges from 11.4 v to 16.5 v. 14 pgnd ground reference point for analog circuitry. 15, 30 av ss negative analog supply pins. voltage ranges from C11.4 v to C16.5 v. 16 iscc this pin is used in association with an optional external resistor to agnd to program the short-circuit current of the output amplifiers. refer to the features section for further details. 17 agndd ground reference pin for dac d output amplifier. 18 voutd analog output voltage of dac d. buffered output with a nominal full-scale output range of 10 v. the output amplifier is capable of dire ctly driving a 10 k, 200 pf load. 19 voutc analog output voltage of dac c. buffered output with a nominal full-scale output range of 10 v. the output amplifier is capable of dire ctly driving a 10 k, 200 pf load. 20 agndc ground reference pin for dac c output amplifier.
ad5744 preliminary technical data rev. pre | page 12 of 32 pin no. mnemonic description 21 agndb ground reference pin for dac b output amplifier. 22 voutb analog output voltage of dac b. buffered output with a nominal full-scale output range of 10 v. the output amplifier is capable of dire ctly driving a 10 k, 200 pf load. 23 vouta analog output voltage of dac a. buffered output with a nominal full-scale output range of 10 v. the output amplifier is capable of dire ctly driving a 10 k, 200 pf load. 24 agnda ground reference pin for dac a output amplifier. 25 refab external reference voltage input for channel a and channel b. reference input range is 1 v to 7 v; programs the full-scale output voltage. refin = 5 v for specified performance. 26 refcd external reference voltage input for channel c and channel d. reference input range is 1 v to 7 v; programs the full-scale output voltage. refin = 5 v for specified performance. 27 nc no connect. 28 refgnd reference ground return for the reference generator and buffers. 29 nc no connect. 32 bin/ 2scomp determines the dac coding. this pin should be hardwired to either dv cc or dgnd. when hardwired to dv cc , input coding is offset binary. when hardwired to dgnd, input coding is twos complement (see table 7 ). 1 internal pull-up device on this logic input. therefore, it can be left floating and defaults to a logic high condition.
preliminary technical data ad5744 rev. pre | page 13 of 32 terminology relative accuracy or integral nonlinearity (inl) for the dac, relative accuracy or integral nonlinearity (inl) is a measure of the maximum deviation, in lsbs, from a straight line passing through the endpoints of the dac transfer function. a typical inl vs. code plot can be seen in figure 7 . differential nonlinearity (dnl) differential nonlinearity is the difference between the measured change and the ideal 1 lsb change between any two adjacent codes. a specified differential nonlinearity of 1 lsb maximum ensures monotonicity. this dac is guaranteed monotonic. a typical dnl vs. code plot can be seen in figure 9 . monotonicity a dac is monotonic if the output either increases or remains constant for increasing digital input code. the ad5744 is monotonic over its full operating temperature range. bipolar zero error bipolar zero error is the deviation of the analog output from the ideal half-scale output of 0 v when the dac register is loaded with 0x8000 (offset binary coding) or 0x0000 (twos complement coding). a plot of bipolar zero error vs. temperature can be seen in figure 22 . bipolar zero tc bipolar zero tc is the measure of the change in the bipolar zero error with a change in temperature. it is expressed in ppm fsr/c. full-scale error full-scale error is a measure of the output error when full-scale code is loaded to the dac register. ideally the output voltage should be 2 v ref ? 1 lsb. full-scale error is expressed in percentage of full-scale range. negative full-scale error/zero scale error negative full-scale error is the error in the dac output voltage when 0x0000 (offset binary coding) or 0x8000 (twos complement coding) is loaded to the dac register. ideally, the output voltage should be ?2 v ref . a plot of zero-scale error vs. temperature can be seen in figure 21 . output voltage settling time output voltage settling time is the amount of time it takes for the output to settle to a specified level for a full-scale input change. slew rate the slew rate of a device is a limitation in the rate of change of the output voltage. the output slewing speed of a voltage-output d/a converter is usually limited by the slew rate of the amplifier used at its output. slew rate is measured from 10% to 90% of the output signal and is given in v/s. gain error gain error is a measure of the span error of the dac. it is the deviation in slope of the dac transfer characteristic from the ideal, expressed as a percentage of the full-scale range. a plot of gain error vs. temperature can be seen in figure 23 . tot a l un a dju s te d e r ror total unadjusted error (tue) is a measure of the output error considering all the various errors. a plot of total unadjusted error vs. reference can be seen in figure 19 . zero-scale error tc zero-scale error tc is a measure of the change in zero-scale error with a change in temperature. zero-scale error tc is expressed in ppm fsr/c. gain error tc gain error tc is a measure of the change in gain error with changes in temperature. gain error tc is expressed in (ppm of fsr)/c. digital-to-analog glitch energy digital-to-analog glitch impulse is the impulse injected into the analog output when the input code in the dac register changes state. it is normally specified as the area of the glitch in nv secs and is measured when the digital input code is changed by 1 lsb at the major carry transition (0x7fff to 0x8000) (see figure 28 ). digital feedthrough digital feedthrough is a measure of the impulse injected into the analog output of the dac from the digital inputs of the dac but is measured when the dac output is not updated. it is specified in nv secs and measured with a full-scale code change on the data bus, that is, from all 0s to all 1s and vice versa. power supply sensitivity power supply sensitivity indicates how the output of the dac is affected by changes in the power supply voltage. dc crosstalk dc crosstalk is the dc change in the output level of one dac in response to a change in the output of another dac. it is measured with a full-scale output change on one dac while monitoring another dac, and is expressed in lsbs. dac-to-dac crosstalk dac-to-dac crosstalk is the glitch impulse transferred to the output of one dac due to a digital code change and subsequent output change of another dac. this includes both digital and analog crosstalk. it is measured by loading one of the dacs with a full-scale code change (all 0s to all 1s and vice versa) with ldac low and monitoring the output of another dac. the energy of the glitch is expressed in nv-s.
ad5744 preliminary technical data rev. pre | page 14 of 32 channel-to-channel isolation channel-to-channel isolation is the ratio of the amplitude of the signal at the output of one dac to a sine wave on the reference input of another dac. it is measured in db. digital crosstalk digital crosstalk is a measure of the impulse injected into the analog output of one dac from the digital inputs of another dac but is measured when the dac output is not updated. it is specified in nv secs and measured with a full-scale code change on the data bus, that is, from all 0s to all 1s and vice versa.
preliminary technical data ad5744 rev. pre | page 15 of 32 typical performance characteristics 0.25 ?0.25 ?0.20 ?0.15 ?0.10 ?0.05 0 0.05 0.10 0.15 0.20 0 16000 14000 12000 1000 8000 6000 4000 2000 inl error (lsb) code 06063-009 t a = 25c v dd /v ss = 15v refin = 5v 0.25 ?0.25 ?0.20 ?0.15 ?0.10 ?0.05 0 0.05 0.10 0.15 0.20 0 16000 14000 12000 1000 8000 6000 4000 2000 dnl error (lsb) code 06063-014 t a = 25c v dd /v ss = 12v refin = 5v figure 7. integral nonlinearity error vs. code, v figure 10. differential nonlinearity error vs. code, v dd /v ss = 15 v 0 16000 14000 12000 1000 8000 6000 4000 2000 inl error (lsb) code t a = 25c v dd /v ss = 12v refin = 5v 06063-010 0.25 ?0.25 ?0.20 ?0.15 ?0.10 ?0.05 0 0.05 0.10 0.15 0.20 figure 8. integral nonlinearity error vs. code, v dd /v ss = 12 v 0.25 ?0.25 ?0.20 ?0.15 ?0.10 ?0.05 0 0.05 0.10 0.15 0.20 0 16000 14000 12000 1000 8000 6000 4000 2000 dnl error (lsb) code t a = 25c v dd /v ss = 15v refin = 5v 06063-013 figure 9. differential nonlinearity error vs. code, v dd /v ss = 15 v dd /v ss = 12 v 0.12 ?0.04 ?0.02 0 0.02 0.04 0.06 0.08 0.10 ?40 100 ?20 0 20 40 60 80 inl error (lsb) temperature (c) 06064-015 figure 11. integral nonlinearity error vs. temperature, v dd /v ss = 15 v 0.12 ?0.04 ?0.02 0 0.02 0.04 0.06 0.08 0.10 ?40 100 ?20 0 20 40 60 80 inl error (lsb) temperature (c) 06064-016 figure 12. integral nonlinearity error vs. temperature, v dd /v ss = 12 v
ad5744 preliminary technical data rev. pre | page 16 of 32 0.04 ?0.06 ?0.05 ?0.04 ?0.03 ?0.02 ?0.01 0 0.01 0.02 0.03 ?40 100 ?20 0 20 40 60 80 dnl error (lsb) temperature (c) 06064-019 0.03 ?0.06 ?0.05 ?0.04 ?0.02 ?0.02 ?0.01 0 0.01 0.02 11.4 16.4 15.4 14.4 13.4 12.4 dnl error (lsb) supply voltage (v) 06064-025 figure 13. differential nonlinearity error vs. temperature, v figure 16. differential nonlinearity error vs. supply voltage dd /v ss = 15 v 0.04 ?0.06 ?0.05 ?0.04 ?0.03 ?0.02 ?0.01 0 0.01 0.02 0.03 ?40 100 ?20 0 20 40 60 80 dnl error (lsb) temperature (c) 06064-020 0.20 ?0.25 ?0.20 ?0.15 ?0.10 ?0.05 0 0.05 0.10 0.15 17 56 4 3 2 inl error (lsb) reference voltage (v) 06064-027 figure 14. differential nonlinearity error vs. temperature, v figure 17. integral nonlinearity error vs. reference voltage dd /v ss = 12 v 0.12 ?0.04 ?0.02 0 ?0.02 ?0.04 ?0.06 ?0.08 ?0.10 11.4 16.4 15.4 14.4 13.4 12.4 inl error (lsb) supply voltage (v) 06064-023 0.10 ?0.10 ?0.08 ?0.06 ?0.04 ?0.02 0 0.02 0.04 0.06 0.08 17 56 4 3 2 dnl error (lsb) reference voltage (v) 06064-031 figure 15. integral nonlinearity error vs. supply voltage figure 18. differential nonlinearity error vs. reference voltage
preliminary technical data ad5744 rev. pre | page 17 of 32 0.6 ?1.6 ?1.4 ?1.2 ?1.0 ?0.8 ?0.6 ?0.4 ?0.2 0 0.2 0.4 17 56 4 3 2 tue (mv) reference voltage (v) t a = 25c 06063-035 0.8 0.6 0.4 ?0.4 ?0.2 0 0.2 ?40 100 80 60 40 20 0 ?20 bipolar zero error (mv) temperature (c) refin = 5v v dd /v ss = 15v v dd /v ss = 12v 06063-039 figure 19. total unadjusted error vs. reference voltage, v figure 22. bipolar zero error vs. temperature dd /v ss = 16.5 v 14 13 12 11 10 9 8 11.4 16.4 15.4 14.4 13.4 12.4 current (ma) v dd /v ss (v) t a = 25c refin = 5v |i ss | |i dd | 06063-037 1.4 0.6 0.8 1.0 1.2 0.4 ?0.2 0 0.2 ?40 100 80 60 40 20 0 ?20 gain error (mv) temperature (c) refin = 5v v dd /v ss = 15v v dd /v ss = 12v 06063-040 figure 23. gain error vs. temperature figure 20. i dd /i ss vs. v dd /v ss 0.0014 0.0013 0.0012 0.0011 0.0010 0.0009 0.0008 0.0007 0.0006 05 4.54.03.53.02.5 2.01.51.00.5 di cc (ma) v logic 0.25 ?0.25 ?0.20 ?0.15 ?0.10 ?0.05 0 0.05 0.10 0.15 0.20 ?40 100 80 60 40 20 0 ?20 zero-scale error (mv) temperature (c) refin = 5v v dd /v ss = 15v v dd /v ss = 12v 06063-038 . 0 t a = 25c 5v 3v 06063-041 figure 21. zero-scale error vs. temperature figure 24. di vs. logic input voltage cc
ad5744 preliminary technical data rev. pre | page 18 of 32 7000 3000 4000 5000 6000 2000 ?1000 0 1000 ?10 10 5 0 ?5 output voltage (v) source/sink current (ma) t a = 25c refin = 5v v dd /v ss = 15v v dd /v ss = 12v 06063-042 ? 4 ?6 ?8 ?10 ?12 ?14 ?16 ?18 ?20 ?22 ?24 ?26 ?2.0?1.5?1.0?0.5 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 v out (mv) time (s) v dd /v ss = 12v, refin = 5v, t a = 25c, 0x8000 to 0x7fff, 500ns/div 06063-047 figure 25. source and sink capability of output amplifier with positive full scale loaded figure 28. major code transition glitch energy, v /v 10000 7000 8000 9000 3000 4000 5000 6000 2000 ?1000 0 1000 ?12 8 3 ?2 ?7 output voltage (v) source/sink current (ma) 15v supplies 12v supplies t a = 25c refin = 5v 06063-043 figure 26. source and sink capability of output amplifier with negative full scale loaded ch1 3.00v m1.00s ch1 ?120mv 1 v dd /v ss = 15v t a = 25c refin = 5v 1s/div 06063-044 figure 27. full-scale settling time dd ss = 12 v ch4 50.0v m1.00s ch4 26v 4 v dd /v ss = 15v midscale loaded refin = 0v 50v/div 06063-048 figure 29. peak-to-peak no ise (100 khz bandwidth) ch1 10.0v b w ch3 10.0mv b w t 29.60% ch2 10.0v m100s a ch1 7.80mv 1 2 3 v dd /v ss = 12v, refin = 5v, t a = 25c, ramp time = 100s, load = 200pf||10k ? t 06063-055 figure 30. vout vs. v dd /v ss on power-up
preliminary technical data ad5744 rev. pre | page 19 of 32 10 9 8 7 6 5 4 3 2 1 0 0 120 100 80 60 40 20 short-circuit current (ma) ri scc (k ? ) v dd /v ss = 15v t a = 25c refin = 5v 06063-050 figure 31. short-circuit current vs. ri scc
ad5744 preliminary technical data rev. pre | page 20 of 32 theory of operation serial interface the ad5744 is a quad, 14-bit, serial input, bipolar voltage output dac and operates from supply voltages of 11.4 v to 16.5 v and has a buffered output voltage of up to 10.5263 v. data is written to the ad5744 in a 24-bit word format, via a 3-wire serial interface. the device also offers an sdo pin, which is available for daisy chaining or readback. the ad5744 is controlled over a versatile 3-wire serial interface that operates at clock rates of up to 30 mhz and is compatible with spi?, qspi?, microwire?, and dsp standards. input shift register the input shift register is 24 bits wide. data is loaded into the device msb first as a 24-bit word under the control of a serial clock input, sclk. the input register consists of a read/write bit, three register select bits, three dac address bits and 16 data bits as shown in the ad5744 incorporates a power-on reset circuit, which ensures that the dac registers power up loaded with 0x0000. the ad5744 features a digital i/o port that can be programmed via the serial interface, on-chip reference buffers and per channel digital gain registers. table 8 . the timing diagram for this operation is shown in figure 2 . dac architecture upon power-up, the dac registers are loaded with zero code (0x0000) and the outputs are clamped to 0 v via a low impedance path. the outputs can be updated with the zero code value at this time by asserting either the dac architecture of the ad5744 consists of a 14-bit current mode segmented r-2r dac. the simplified circuit diagram for the dac section is shown in figure 32 . the four msbs of the 14-bit data word are decoded to drive 15 switches, e1 to e15. each of these switches connects one of the 15 matched resistors to either agnd or iout. the remaining 10 bits of the data word drive switches s0 to s9 of the 10-bit r- 2r ladder network. 2r e15 v ref 2r e14 e1 2r s9 rr r 2r s8 2r 10-bit, r-2r ladder 4 msbs decoded into 15 equal segments v out 2r s0 2r agnd r/8 i out 06063-060 figure 32. dac ladder structure reference buffers the ad5744 operates with an external reference. the reference inputs (refab and refcd) have an input range up to 7 v. this input voltage is then used to provide a buffered positive and negative reference for the dac cores. the positive reference is given by + v ref = 2 v ref while the negative reference to the dac cores is given by ?v ref = ?2 v ref these positive and negative reference voltages (along with the gain register values) define the output ranges of the dacs. ldac or clr . the corresponding output voltage depends on the state of the bin/ 2scomp pin. if the bin/ 2scomp pin is tied to dgnd, then the data coding is twos complement and the outputs update to 0 v. if the bin/ 2scomp pin is tied to dv cc , then the data coding is offset binary and the outputs update to negative full scale. to have the outputs power-up with zero code loaded to the outputs, the clr pin should be held low during power- up. standalone operation the serial interface works with both a continuous and noncon- tinuous serial clock. a continuous sclk source can only be used if sync is held low for the correct number of clock cycles. in gated clock mode, a burst clock containing the exact number of clock cycles must be used and sync must be taken high after the final clock to latch the data. the first falling edge of sync starts the write cycle. exactly 24 falling clock edges must be applied to sclk before sync is brought back high again. if sync is brought high before the 24 th falling sclk edge, then the data written is invalid. if more than 24 falling sclk edges are applied before sync is brought high, then the input data is also invalid. the register addressed is updated on the rising edge of sync . in order for another serial transfer to take place, sync must be brought low again. after the end of the serial data transfer, data is automatically transferred from the input shift register to the addressed register. when the data has been transferred into the chosen register of the addressed dac, all dac registers and outputs can be updated by taking ldac low.
preliminary technical data ad5744 rev. pre | page 21 of 32 68hc11 1 miso sync sdin sclk mosi sck pc7 pc6 ldac sdo sync sclk ldac sdo sync sclk ldac sdo sdin sdin 1 additional pins omitted for clarity ad5744 1 ad5744 1 ad5744 1 06063-061 a continuous sclk source can only be used if sync is held low for the correct number of clock cycles. in gated clock mode, a burst clock containing the exact number of clock cycles must be used and sync must be taken high after the final clock to latch the data. readback operation before a readback operation is initiated, the sdo pin must be enabled by writing to the function register and clearing the sdo disable bit; this bit is cleared by default. readback mode is invoked by setting the r/ w bit = 1 in the serial input register write. with r/ w = 1, bit a2 to bit a0, in association with bit reg2, bit reg1, and bit reg0, select the register to be read. the remaining data bits in the write sequence are dont care. during the next spi write, the data appearing on the sdo output contain the data from the previously addressed register. for a read of a single register, the nop command can be used in clocking out the data from the selected register on sdo. the readback diagram in figure 4 shows the readback sequence. for example, to read back the fine gain register of channel a on the ad5744, the following sequence should be implemented: 1. write 0xa0xxxx to the ad5744 input register. this configures the ad5744 for read mode with the fine gain register of channel a selected. note that all the data bits, db15 to db0, are dont care. figure 33. daisy chaining the ad5744 daisy-chain operation 2. follow this with a second write, a nop condition, 0x00xxxx. during this write, the data from the fine gain register is clocked out on the sdo line, that is, data clocked out contains the data from the fine gain register in bit db5 to bit db0. for systems that contain several devices, the sdo pin can be used to daisy chain several devices together. this daisy-chain mode can be useful in system diagnostics and in reducing the number of serial interface lines. the first falling edge of sync starts the write cycle. the sclk is continuously applied to the input shift register when simultaneous updating via ldac sync is low. if more than 24 clock pulses are applied, the data ripples out of the shift register and appears on the sdo line. this data is clocked out on the rising edge of sclk and is valid on the falling edge. by connecting the sdo of the first device to the sdin input of the next device in the chain, a multidevice interface is constructed. each device in the system requires 24 clock pulses. therefore, the total number of clock cycles must equal 24n, where n is the total number of ad5744 devices in the chain. when the serial transfer to all devices is complete, sync is taken high. this latches the input data in each device in the daisy chain and prevents any further data from being clocked into the input shift register. the serial clock can be a continuous or a gated clock. depending on the status of both sync and ldac , and after data has been transferred into the input register of the dacs, there are two ways in which the dac registers and dac outputs can be updated. individual dac updating in this mode, ldac is held low while data is being clocked into the input shift register. the addressed dac output is updated on the rising edge of sync . simultaneous updating of all dacs in this mode, ldac is held high while data is being clocked into the input shift register. all dac outputs are updated by taking ldac low any time after sync has been taken high. the update now occurs on the falling edge of ldac .
ad5744 preliminary technical data rev. pre | page 22 of 32 v out dac register interface logic output i/v amplifier ldac sdo sdin 14-bit dac v refin sync input register sclk 06063-062 the output voltage expression for the ad5744 is given by ? ? ? ? ? ? +?= d v v v refin refin out where: d is the decimal equivalent of the code loaded to the dac. v refin is the reference voltage applied at the refab/refcd pins. asynchronous clear ( clr ) clr is a negative edge triggered clear that allows the outputs to be cleared to either 0 v (twos complement coding) or negative full scale (offset binary coding). it is necessary to maintain figure 34. simplified serial interface of input loading circuitry for one dac channel clr low for a minimum amount of time (see transfer function figure 3 ) for the operation to complete. when the table 7 shows the ideal input code to output voltage relationship for the ad5744 for bo th offset binary and twos complement data coding. clr signal is returned high, the output remains at the cleared value until a new value is programmed. if at power-on clr is at 0 v, then all dac outputs are updated with the clear value. a clear can also be initiated through software by writing the command 0x04xxxx to the ad5744. table 7. ideal output voltage to input code relationship for the ad5744 digital input analog output offset binary data coding msb lsb v out 11 1111 1111 1111 +2 v (8191/8192) ref 10 0000 0000 0001 +2 v (1/8192) ref 10 0000 0000 0000 0 v 01 1111 1111 1111 ?2 v (1/8192) ref 00 0000 0000 0000 ?2 v (8191/8192) ref twos complement data coding msb lsb v out 01 1111 1111 1111 +2 v (8191/8192) ref 00 0000 0000 0001 +2 v (1/8192) ref 00 0000 0000 0000 0 v 11 1111 1111 1111 ?2 v (1/8192) ref 10 0000 0000 0000 ?2 v (8191/8192) ref
preliminary technical data ad5744 rev. pre | page 23 of 32 table 8. ad5744 input register format msb lsb db23 db22 db21 db20 db19 db18 db17 db16 db15 db14 db13 db12 db11 db10 db9 db8 db7 db6 db5 db4 db3 db2 db1 db0 r/ w 0 reg2 reg1 reg0 a2 a1 a0 data table 9. input register bit functions register function r/ w indicates a read from or a write to the addressed register. reg2, reg1, reg0 used in association with the address bits to determine if a read or write operation is to the data register, offset register, gain register, or function register. reg2 reg1 reg0 function 0 0 0 function register 0 1 0 data register 0 1 1 coarse gain register 1 0 0 fine gain register a2, a1, a0 these bits are used to decode the dac channels. a2 a1 a0 channel address 0 0 0 dac a 0 0 1 dac b 0 1 0 dac c 0 1 1 dac d 1 0 0 all dacs d15:d0 data bits. function register the function register is addressed by setting the three reg bits to 000. the values written to the address bits and the data bi ts determine the function addressed. the functions available via the function register are outlined in table 1 0 and table 11 . table 10. function register options reg2 reg1 reg0 a2 a1 a0 db15:db6 db5 db4 db3 db2 db1 db0 0 0 0 0 0 0 nop, data = dont care 0 0 0 0 0 1 dont care local- ground- offset adjust d1 direction d1 value d0 direction d0 value sdo disable 0 0 0 1 0 0 clr, data = dont care 0 0 0 1 0 1 load, data = dont care table 11. explanation of function register options option description nop no operation instruction used in readback operations. local-ground- offset adjust set by the user to enable local-ground-offset adjust function . cleared by the user to disable local-ground-offset adjust function (default). refer to features section for further details. d0/d1 direction set by the user to enable d0/d1 as outputs . cleared by the user to enable d0/d1 as inputs (default). refer to the features section for further details. d0/d1 value i/o port status bits. logic values written to these location s determine the logic outputs on the d0 and d1 pins when configured as outputs. these bits indicate the status of the d0 and d1 pins when th e i/o port is active as an input. when enabled as inputs, these bits are do nt cares during a write operation. sdo disable set by the user to disabl e the sdo output. cleared by the user to enable the sdo output (default). clr addressing this function resets the da c outputs to 0 v in twos complement mode and negative full scale in binary mode. load addressing this function updates the dac registers and consequently the analog outputs.
ad5744 preliminary technical data rev. pre | page 24 of 32 data register the data register is addressed by setting the three reg bits to 010. the dac address bits select with which dac channel the dat a transfer is to take place (see table 9 ). the data bits are in positions db15 to db2 as shown in table 12 . table 12. programming the ad5744 data register reg2 reg1 reg0 a2 a1 a0 db15 db14 db13 db12 db11 db10 db9 db8 db7 db6 db5 db4 db3 db2 db1 db0 0 1 0 dac address 14-bit dac data x x coarse gain register the coarse gain register is addressed by setting the three reg bits to 011. the dac address bits select with which dac channel the data transfer is to take place (see tabl e 9 ). the coarse gain register is a 2-bit register and allows the user to select the output range of each dac as shown in table 13 and table 14 . table 13. programming the ad5744 coarse gain register reg2 reg1 reg0 a2 a1 a0 db15 . db2 db1 db0 0 1 1 dac address dont care cg1 cg0 table 14. output range selection output range cg1 cg0 10 v (default) 0 0 10.2564 v 0 1 10.5263 v 1 0 fine gain register the fine gain register is addressed by setting the three reg bits to 100. the dac address bits select with which dac channel th e data transfer is to take place (see tabl e 9 ). the fine gain register is a 6-bit register and allows the user to adjust the gain of each dac channel by ?8 lsbs to +7.75 lsbs in 0.25 lsb steps as shown in table 1 5 and table 16 . the adjustment is made to both the positive full-scale points and the negative full-scale points simultaneously, each point being adjusted by ? of one step. the fine gain register co ding is twos complement. table 15. programming ad5744 fine gain register reg2 reg1 reg0 a2 a1 a0 db15:db6 db5 db4 db3 db2 db1 db0 1 0 0 dac address dont care fg5 fg4 fg3 fg2 fg1 fg0 table 16. ad5744 fine gain register options gain adjustment fg5 fg4 fg3 fg2 fg1 fg0 +7.75 lsbs 0 1 1 1 1 1 +7.5 lsbs 0 1 1 1 1 0 - - - - - - no adjustment (default) 0 0 0 0 0 0 - - - - - - ?7.75 lsbs 1 0 0 0 0 1 ?8 lsbs 1 0 0 0 0 0
preliminary technical data ad5744 rev. pre | page 25 of 32 ad5744 features analog output control if the iscc pin is left unconnected, the short circuit current limit defaults to 5 ma. it should be noted that limiting the short circuit current to a small value can affect the slew rate of the output when driving into a capacitive load, therefore, the value of short-circuit current programmed should take into account the size of the capacitive load being driven. in many industrial process control applications, it is vital that the output voltage be controlled during power-up and during brownout conditions. when the supply voltages are changing, the vout pins are clamped to 0 v via a low impedance path. to prevent the output amp being shorted to 0 v during this time, transmission gate g1 is also opened (see figure 35 ). these conditions are maintained until the power supplies stabilize and a valid word is written to the dac register. at this time, g2 opens and g1 closes. both transmission gates are also externally controllable via the reset in ( digital i/o port the ad5744 contains a 2-bit digital i/o port (d1 and d0), these bits can be configured as inputs or outputs independently, and can be driven or have their values read back via the serial interface. the i/o port signals are referenced to dv rstin ) control input. for instance, if rstin cc and dgnd. when configured as outputs, they can be used as control signals to multiplexers or can be used to control calibration circuitry elsewhere in the system. when configured as inputs, the logic signals from limit switches, for example can be applied to d0 and d1 and can be read back via the digital interface. is driven from a battery supervisor chip, the rstin input is driven low to open g1 and close g2 on power- off or during a brownout. conversely, the on-chip voltage detector output ( rstout ) is also available to the user to control other parts of the system. the basic transmission gate functionality is shown in figure 35 . g1 g2 rstout rstin vouta agnda voltage monitor and control 06063-063 local ground offset adjust the ad5744 incorporates a local-ground-offset adjust feature which when enabled in the function register adjusts the dac outputs for voltage differences between the individual dac ground pins and the refgnd pin ensuring that the dac output voltages are always with respect to the local dac ground pin. for instance, if pin agnda is at +5 mv with respect to the refgnd pin and vouta is measured with respect to agnda then a ?5mv error results, enabling the local-ground-offset adjust feature adjusts vouta by +5 mv, eliminating the error. figure 35. analog output control circuitry programmable short-circuit protection the short-circuit current of the output amplifiers can be pro- grammed by inserting an external resistor between the iscc pin and pgnd. the programmable range for the current is 500 a to 10 ma, corresponding to a resistor range of 120 k to 6 k . the resistor value is calculated as follows: isc r 60 =
ad5744 preliminary technical data rev. pre | page 26 of 32 applications information precision voltage reference selection typical operating circuit to achieve the optimum performance from the ad5744 over its full operating temperature range, a precision voltage reference must be used. thought should be given to the selection of a precision voltage reference. the ad5744 has two reference inputs, refab and refcd. the voltages applied to the reference inputs are used to provide a buffered positive and negative reference for the dac cores. therefore, any error in the voltage reference is reflected in the outputs of the device. figure 36 shows the typical operating circuit for the ad5744. the only external components needed for this precision 14-bit dac are a reference voltage source, decoupling capacitors on the supply pins and reference inputs, and an optional short- circuit current setting resistor. because the device incorporates reference buffers, it eliminates the need for an external bipolar reference and associated buffers. this leads to an overall savings in both cost and board space. there are four possible sources of error to consider when choosing a voltage reference for high accuracy applications: initial accuracy, temperature coefficient of the output voltage, long term drift, and output voltage noise. figure 36 , v in dd and v ss are both connected to 15 v, but v dd and v ss can operate with supplies from 11.4 v to 16.5 v. in figure 36 , agnda is connected to refgnd. 1 2 3 4 5 6 7 8 23 22 21 18 19 20 24 17 9 10 11 12 13 14 15 16 32 31 30 29 28 27 26 25 ad5744 sync sclk sdin sdo d0 ldac clr d1 vouta voutb agndb voutd voutc agndc agnda agndd rstout rstin dgnd dv cc av dd pgnd av ss iscc bin/2scomp avdd avss nc refgnd nc refcd refab sync sclk sdin sdo ldac d0 d1 rstout rstin bin/2scomp +5v +5v +15v ?15v nc = no connect +15v ?15v vouta voutb voutc voutd 100nf 100nf 100nf 10f 100nf 100nf 100nf 10f 10f 10f 10f adr02 4 gnd 2 6 vout vin +15v 06063-064 initial accuracy error on the output voltage of an external refer- ence could lead to a full-scale error in the dac. therefore, to minimize these errors, a reference with low initial accuracy error specification is preferred. choosing a reference with an output trim adjustment, such as the adr425, allows a system designer to trim system errors out by setting the reference voltage to a voltage other than the nominal. the trim ad- justment can also be used at temperature to trim out any error. long term drift is a measure of how much the reference output voltage drifts over time. a reference with a tight long-term drift specification ensures that the overall solution remains relatively stable over its entire lifetime. the temperature coefficient of a references output voltage affects inl, dnl, and tue. a reference with a tight temperature coefficient specification should be chosen to reduce the dependence of the dac output voltage on ambient conditions. in high accuracy applications, which have a relatively low noise budget, reference output voltage noise needs to be considered. choosing a reference with as low an output noise voltage as practical for the system resolution required is important. precision voltage references such as the adr435 (xfet design) produce low output noise in the 0.1 hz to 10 hz region. however, as the circuit bandwidth increases, filtering the output of the reference may be required to minimize the output noise. figure 36. typical operating circuit table 17. some precision references recommended for use with the ad5744 part no. initial accuracy(mv max) long-term drift (ppm typ) te mp drift (ppm/c max) 0.1 hz to 10 hz noise (v p-p typ) adr435 6 30 3 3.4 adr425 6 50 3 3.4 adr02 5 50 3 15 adr395 6 50 25 5 ad586 2.5 15 10 4
preliminary technical data ad5744 rev. pre | page 27 of 32 layout guidelines v ia serial clock out to sclk v oa encode decode v ib serial data out to sdin v ob encode decode v ic sync out to sync v oc encode decode v id control out to ldac v od encode decode controller adum1400 1 1 additional pins omitted for clarity 06063-065 in any circuit where accuracy is important, careful consider- ation of the power supply and ground return layout helps to ensure the rated performance. the printed circuit board on which the ad5744 is mounted shou ld be designed so that the analog and digital sections are separated and confined to certain areas of the board. if the ad5744 is in a system where multiple devices require an agnd-to-dgnd connection, the connection should be made at one point only. the star ground point should be established as close as possible to the device. the ad5744 should have ample supply bypassing of 10 f in parallel with 0.1 f on each su pply located as close to the package as possible, ideally right up against the device. the 10 f capacitors are the tantalum bead type. the 0.1 f capacitor should have low effective seri es resistance (esr) and low effective series inductance (esi) such as the common ceramic types, which provide a low impedance path to ground at high frequencies to handle transient currents due to internal logic switching. figure 37. isolated interface microprocessor interfacing microprocessor interfacing to the ad5744 is via a serial bus that uses standard protocol compatible with microcontrollers and dsp processors. the communications channel is a 3-wire (minimum) interface consisting of a clock signal, a data signal, and a synchronization signal. the ad5744 requires a 24-bit data-word with data valid on the falling edge of sclk. the power supply lines of the ad5744 should use as large a trace as possible to provide low impedance paths and reduce the effects of glitches on the power supply line. fast switching signals, such as clocks, should be shielded with digital ground to avoid radiating noise to other parts of the board, and should never be run near the reference inputs. a ground line routed between the sdin and sclk lines helps reduce cross-talk between them (not required on a multilayer board, which has a separate ground plane, however, it is helpful to separate the lines). it is essential to minimize noise on the reference inputs, because it couples through to the dac output. avoid crossover of digital and analog signals. tr aces on opposite sides of the board should run at right angles to each other. this reduces the effects of feed through on the board. a microstrip technique is recommended, but not always possible with a double-sided board. in this technique, the component side of the board is dedicated to ground plane, while si gnal traces are placed on the solder side. for all the interfaces, the dac output update can be done automatically when all the data is clocked in, or it can be done under the control of ldac. the contents of the dac register can be read using the readback function. ad5744 to mc68hc11 interface figure 38 shows an example of a serial interface between the ad5744 and the mc68hc11 microcontroller. the serial peripheral interface (spi) on the mc68hc11 is configured for master mode (mstr = 1), clock polarity bit (cpol = 0), and the clock phase bit (cpha = 1). the spi is configured by writing to the spi control register (spcr) (see the 68hc11user manual) . sck of the mc68hc11 drives the sclk of thead5744, the mosi output drives the serial data line (din) of the ad5744/ ad5744, and the miso input is driven from sdo. the sync is driven from one of the port lines, in this case pc7. galvanically isolated interface in many process control applications, it is necessary to provide an isolation barrier between the controller and the unit being controlled to protect and isolate the controlling circuitry from any hazardous common-mode voltages that might occur. isocouplers provide voltage isolation in excess of 2.5 kv. the serial loading structure of the ad5744 makes it ideal for isolated interfaces, because the number of interface lines is kept to a minimum. figure 37 shows a 4-channel isolated interface to the ad5744 using an adum1400. for more information, go to www.analog.com.
ad5744 preliminary technical data rev. pre | page 28 of 32 when data is being transmitted to the ad5744, the sync line (pc7) is taken low and data is transmitted msb first. data appearing on the mosi output is valid on the falling edge of sck. eight falling clock edges occur in the transmit cycle, so, in order to load the required 24-bit word, pc7 is not brought high until the third 8-bit word has been transferred to the dacs input shift register. the 8xc51 transmits data in 8-bit bytes with only eight falling clock edges occurring in the transmit cycle. because the dac expects a 24-bit word, sync (p3.3) must be left low after the first eight bits are transferred. after the third byte has been transferred, the p3.3 line is taken high. the dac can be updated using ldac via p3.4 of the 8xc51. ad5744 to adsp2101/adsp2103 interface mc68hc11 1 1 additional pins omitted for clarity ad5744 1 sdo miso sdin mosi sclk sck sync pc7 06063-066 an interface between the ad5744 and the adsp2101/ adsp2103 is shown in figure 40 . the adsp2101/ adsp2103 should be set up to operate in the sport transmit alternate framing mode. the adsp2101/adsp2103 are programmed through the sport control register and should be configured as follows: internal clock operation, active low framing, and 24- bit word length. transmission is initiated by writing a word to the tx register after the sport has been enabled. as the data is clocked out of the dsp on the rising edge of sclk, no glue logic is required to interface the dsp to the dac. in the interface shown, the dac output is updated using the ldac pin via the dsp. alterna- tively, the ldac input could be tied permanently low, and then the update takes place automatically when tfs is taken high. figure 38. ad5744 to mc68hc11 interface ldac is controlled by the pc6 port output. the dac can be updated after each 3-byte transfer by bringing ldac low. this example does not show other se rial lines for the dac. for example, if clr were used, it could be controlled by port output pc5. sclk sdin sync dt sclk rfs adsp2101/ adsp2103 1 1 additional pins omitted for clarity sdo dr tfs ldac fo ad5744 1 06063-068 ad5744 to 8xc51 interface the ad5744 requires a clock synchronized to the serial data. for this reason, the 8xc51 must be operated in mode 0. in this mode, serial data enters and exits through rxd, and a shift clock is output on txd. p3.3 and p3.4 are bit programmable pins on the serial port and are used to drive sync ldac and , respectively. the 8cx51 provides the lsb of its sbuf register as the first bit in the data stream. the user must ensure that the data in the sbuf register is arranged correctly, because the dac expects msb first. when data is to be transmitted to the dac, p3.3 is taken low. data on rxd is clocked out of the microcontroller on the rising edge of txd and is valid on the falling edge. as a result, no glue logic is required between this dac and the microcontroller interface. figure 40. ad5744 to adsp2101/adsp2103 interface ad5744 to pic16c6x/7x interface the pic16c6x/7x synchronous serial port (ssp) is configured as an spi master with the clock polarity bit set to 0. this is done by writing to the synchronous serial port control register (sspcon). see the pic16/17 microcontroller user manual . in this example, i/o port ra1 is being used to pulse 8xc51 1 1 additional pins omitted for clarity ad5744 1 sclk txd sdin rxd sync p3.3 ldac p3.4 06063-067 sync and enable the serial port of the ad5744. this microcontroller transfers only eight bits of data during each serial transfer operation; therefore, three consecutive write operations are needed. figure 41 shows the connection diagram. figure 39. ad5744 to 8xc51 interface
preliminary technical data ad5744 rev. pre | page 29 of 32 pic16c6x/7x 1 1 additional pins omitted for clarity ad5744 1 sdo sdi/rc4 sdin sdo/rc5 sclk sclk/rc3 sync ra1 06063-069 figure 41. ad5744 to pic16c6x/7x interface
ad5744 preliminary technical data rev. pre | page 30 of 32 outline dimensions compliant to jedec standards ms-026aba 0.45 0.37 0.30 0.80 bsc lead pitch 7.00 bsc sq 9.00 bsc sq 1 24 25 32 8 9 17 16 1.20 max 0.75 0.60 0.45 1.05 1.00 0.95 0.20 0.09 0.08 max coplanarity seating plane 0 min 7 3.5 0 0.15 0.05 view a rotated 90 ccw view a pin 1 top view (pins down) figure 42. 32-lead thin plastic quad flat package [tqfp] (su-32-2) dimensions shown in millimeters ordering guide 1 model function inl temperature package description package option ad5744bsuz quad 14-bit dac 2 lsb max ?40c to +85c 32-lead tqfp su-32-2 2 ad5744bsuz-reel7 quad 14-bit dac 2 lsb max ?40c to +85c 32-lead tqfp su-32-2 2 ad5744csuz quad 14-bit dac 1 lsb max ?40c to +85c 32-lead tqfp su-32-2 2 ad5744csuz-reel7 quad 14-bit dac 1 lsb max ?40c to +85c 32-lead tqfp su-32-2 2 1 analog devices reserves the right to ship higher grade devices in place of lower grade. 2 z = pb-free part.
preliminary technical data ad5744 rev. pre | page 31 of 32 notes
ad5744 preliminary technical data rev. pre | page 32 of 32 t notes ?2006 analog devices, inc. all rights reserved. trademarks and registered trademarks are the property of their respective owners. pr06063-0-3/06(pre) ttt

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