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low noise micropower 2.5 v and 4.096 v precision voltage references adr291/adr292 rev. f 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 ?2007C2011 analog devices, inc. all rights reserved. features supply range 2.8 v to 15 v, adr291 4.4 v to 15 v, adr292 supply current: 15 a maximum low noise: 8 v and 12 v p-p (0.1 hz to 10 hz) high output current: 5 ma temperature range: ?40c to +125c pin-compatible with ref02 / ref19x applications portable instrumentation precision reference for 3 v and 5 v systems analog-to-digital and digital-to-analog converter reference solar-powered applications loop-current-powered instruments connection diagrams nc 1 v in 2 nc 3 gnd 4 nc 8 nc 7 v out 6 nc 5 nc = no connect adr291/ adr292 top view (not to scale) 00163-001 figure 1. 8-lead soic (r-8) 1 2 3 4 v in nc gnd nc 8 7 6 5 nc v out nc nc nc = no connect 00163-002 adr291/ adr292 top view (not to scale) figure 2. 8-lead tssop (ru-8) 321 v out gnd v in top view (not to scale) adr291 00163-003 figure 3. 3-lead to-92 (t-3) general description the adr291 and adr292 are low noise, micropower precision voltage references that use an xfet? reference circuit. the new xfet architecture offers significant performance improvements over traditional band gap and buried zener-based references. improvements include one quarter the voltage noise output of band gap references operating at the same current, very low and ultralinear temperature drift, low thermal hysteresis, and excellent long-term stability. the adr291/adr292 family is a series of voltage references providing stable and accurate output voltages from supplies as low as 2.8 v for the adr291. output voltage options are 2.5 v and 4.096 v for the adr291 and adr292, respectively. quiescent current is only 12 a, making these devices ideal for battery-powered instrumentation. three electrical grades are available offering initial output accuracies of 2 mv, 3 mv, and 6 mv maximum for the adr291, and 3 mv, 4 mv, and 6 mv maximum for the adr292. temperature coefficients for the three grades are 8 ppm/c, 15 ppm/c, and 25 ppm/c maximum, respectively. line regulation and load regulation are typically 30 ppm/v and 30 ppm/ma, maintaining the references overall high performance. for a device with 5.0 v output, refer to the adr293 data sheet. the adr291 and adr292 references are specified over the extended industrial temperature range of ?40c to +125c. devices are available in the 8-lead soic, 8-lead tssop, and 3-lead to-92 packages. table 1. adr291/adr292 product part no. output voltage (v) initial accuracy (%) temperature coefficient (ppm/c) max adr291 2.500 0.08, 0.12, 0.24 8, 15, 25 adr292 4.096 0.07, 0.10, 0.15 8, 15, 25
adr291/adr292 rev. f | page 2 of 20 table of contents features .............................................................................................. 1 ? applications ....................................................................................... 1 ? connection diagrams ...................................................................... 1 ? general description ......................................................................... 1 ? revision history ............................................................................... 2 ? specifications ..................................................................................... 3 ? adr291 electrical sp ecifications ............................................... 3 ? adr292 electrical sp ecifications ............................................... 4 ? absolute maximum ratings ............................................................ 6 ? esd caution .................................................................................. 6 ? pin configurations and function descriptions ........................... 7 ? typical performance characteristics ............................................. 8 ? terminology .................................................................................... 12 ? theory of operation ...................................................................... 13 ? device power dissipation considerations .............................. 13 ? basic voltage reference connections ..................................... 13 ? noise performance ..................................................................... 13 ? turn-on time ............................................................................ 13 ? applications information .............................................................. 14 ? high voltage floating current source .................................... 14 ? kelvin connections .................................................................... 14 ? low power, low voltage reference for data converters ..... 14 ? voltage regulator for portable equipment ............................. 15 ? outline dimensions ....................................................................... 16 ? ordering guide .......................................................................... 17 ? revision history 5/11rev. e to rev. f deleted negative precision reference without precision resistors section ............................................................................. 14 deleted figure 33 and figure 34, renumbered sequentially ... 14 changes to ordering guide .......................................................... 17 12/07rev. d to rev. e changes to features .......................................................................... 1 changes to figure 34 ...................................................................... 14 3/06rev. c to rev. d updated format .................................................................. universal change to table 8 ............................................................................. 6 updated outline dimensions ....................................................... 15 changes to ordering guide .......................................................... 16 9/03rev. b to rev. c deleted adr290 ................................................................. universal changes to specifications ................................................................. 2 changes to ordering guide ............................................................. 4 updated outline dimensions ....................................................... 13
adr291/adr292 rev. f | page 3 of 20 specifications adr291 electrical specifications v s = 3.0 v to 15 v, t a = 25c, unless otherwise noted. table 2. parameter symbol conditions min typ max unit e grade output voltage v out i out = 0 ma 2.498 2.500 2.502 v initial accuracy v oerr C2 +2 mv C0.08 +0.08 % f grade output voltage v out i out = 0 ma 2.497 2.500 2.503 v initial accuracy v oerr C3 +3 mv C0.12 +0.12 % g grade output voltage v out i out = 0 ma 2.494 2.500 2.506 v initial accuracy v oerr C6 +6 mv C0.24 +0.24 % line regulation e/f grades ?v out /?v in i out = 0 ma 30 100 ppm/v g grade 40 125 ppm/v load regulation e/f grades ?v out /?i load v s = 5.0 v, i out = 0 ma to 5 ma 30 100 ppm/ma g grade 40 125 ppm/ma long-term stability ?v out after 1000 hours of operation @ 125c 50 ppm noise voltage e n 0.1 hz to 10 hz 8 v p-p wideband noise density e n @ 1 khz 480 nv/hz v s = 3.0 v to 15 v, t a = ?25c to +85c, unless otherwise noted. table 3. parameter symbol conditions min typ max unit temperature coefficient e grade tcv out i out = 0 ma 3 8 ppm/c f grade 5 15 ppm/c g grade 10 25 ppm/c line regulation e/f grades ?v out /?v in i out = 0 ma 35 125 ppm/v g grade 50 150 ppm/v load regulation e/f grades ?v out /?i load v s = 5.0 v, i out = 0 ma to 5 ma 20 125 ppm/ma g grade 30 150 ppm/ma
adr291/adr292 rev. f | page 4 of 20 v s = 3.0 v to 15 v, t a = ?40c to+125c, unless otherwise noted. table 4. parameter symbol conditions min typ max unit temperature coefficient e grade tcv out i out = 0 ma 3 10 ppm/c f grade 5 20 ppm/c g grade 10 30 ppm/c line regulation e/f grades ?v out /?v in i out = 0 ma 40 200 ppm/v g grade 70 250 ppm/v load regulation e/f grades ?v out /?i load v s = 5.0 v, i out = 0 ma to 5 ma 20 200 ppm/ma g grade 30 300 ppm/ma supply current i s t a = 25c 9 12 a ?40c t a +125c 12 15 a thermal hysteresis v out-hys 8-lead soic, 8-lead tssop 50 ppm adr292 electrical specifications v s = 5 v to 15 v, t a = 25c, unless otherwise noted. table 5. parameter symbol conditions min typ max unit e grade output voltage v out i out = 0 ma 4.093 4.096 4.099 v initial accuracy v oerr ?3 +3 mv ?0.07 +0.07 % f grade output voltage v out i out = 0 ma 4.092 4.096 4.1 v initial accuracy v oerr ?4 +4 mv ?0.10 +0.10 % g grade output voltage v out i out = 0 ma 4.090 4.096 4.102 v initial accuracy v oerr ?6 +6 mv ?0.15 +0.15 % line regulation e/f grades ?v out /?v in v s = 4.5 v to 15 v, i out = 0 ma 30 100 ppm/v g grade 40 125 ppm/v load regulation e/f grades ?v out /?i load v s = 5.0 v, i out = 0 ma to 5 ma 30 100 ppm/ma g grade 40 125 ppm/ma long-term stability ?v out after 1000 hours of operation @ 125c 50 ppm noise voltage e n 0.1 hz to 10 hz 12 v p-p wideband noise density e n @ 1 khz 640 nv/hz
adr291/adr292 rev. f | page 5 of 20 v s = 5 v to 15 v, t a = ?25c to +85c, unless otherwise noted. table 6. parameter symbol conditions min typ max unit temperature coefficient e grade tcv out i out = 0 ma 3 8 ppm/c f grade 5 15 ppm/c g grade 10 25 ppm/c line regulation e/f grades ?v out /v in v s = 4.5 v to 15 v, i out = 0 ma 35 125 ppm/v g grade 50 150 ppm/v load regulation e/f grades ?v out /?i load v s = 5.0 v, i out = 0 ma to 5 ma 20 125 ppm/ma g grade 30 150 ppm/ma v s = 5 v to 15 v, t a = ?40c to +125c, unless otherwise noted. table 7. parameter symbol conditions min typ max unit temperature coefficient e grade tcv out i out = 0 ma 3 10 ppm/c f grade 5 20 ppm/c g grade 10 30 ppm/c line regulation e/f grades ?v out /?v in v s = 4.5 v to 15 v, i out = 0 ma 40 200 ppm/v g grade 70 250 ppm/v load regulation e/f grades ?v out /?i load v s = 5.0 v, i out = 0 ma to 5 ma 20 200 ppm/ma g grade 30 300 ppm/ma supply current i s t a = 25c 10 15 a ?40c t a +125c 12 18 a thermal hysteresis v out-hys 8-lead soic, 8-lead tssop 50 ppm
adr291/adr292 rev. f | page 6 of 20 absolute maximum ratings remove power before inserting or removing units from their sockets. table 8. parameter rating supply voltage 18 v output short-circuit duration to gnd indefinite storage temperature range t, r, ru packages ?65c to +150c operating temperature range adr291/adr292 ?40c to +125c junction temperature range t, r, ru packages ?65c to +125c lead temperature (soldering, 60 sec) 300c stresses above those listed under absolute maximum ratings may cause permanent damage to the device. this is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. table 9. package types package type ja 1 jc unit 8-lead soic (r) 158 43 c/w 8-lead tssop (ru) 240 43 c/w 3-lead to-92 (t) 160 C c/w 1 ja is specified for worst-case conditions. for example, ja is specified for a device in socket testing. in practice, ja is specified for a device soldered in the circuit board. table 10. other xfet products part number nominal output voltage (v) package type adr420 2.048 8-lead msop/soic adr421 2.50 8-lead msop/soic adr423 3.0 8-lead msop/soic adr425 5.0 8-lead msop/soic esd caution
adr291/adr292 rev. f | page 7 of 20 pin configurations and function descriptions nc 1 v in 2 nc 3 gnd 4 nc 8 nc 7 v out 6 nc 5 nc = no connect adr291/ adr292 top view (not to scale) 00163-036 figure 4. 8-lead soic (r-8) 1 2 3 4 v in nc gnd nc 8 7 6 5 nc v out nc nc nc = no connect 00163-037 adr291/ adr292 top view (not to scale) figure 5. 8-lead tssop (ru-8) 321 v out gnd v in top view (not to scale) adr291 00163-038 figure 6. 3-lead to-92 (t-3) table 11. pin function descriptions pin no. soic tssop to-92 mnemonic description 1, 3, 5, 7, 8 1, 3, 5, 7, 8 n/a nc no connect 2 2 1 v in input voltage 4 4 2 gnd ground 6 6 3 v out output voltage
adr291/adr292 rev. f | page 8 of 20 typical performance characteristics temperature ( c) 2.506 2.494 ?50 125 ?25 output voltage (v) 0 255075100 2.504 2.502 2.500 2.498 2.496 v s = 5v 3 typical parts 00163-004 figure 7. adr291 v out vs. temperature 4.102 output voltage (v) temperature ( c) 4.100 4.098 4.096 4.094 4.092 3 typical parts 4.090 ?50 125 ?25 0 25 50 75 100 00163-005 v s = 5v figure 8. adr292 v out vs. temperature input voltage (v) 14 0 01 6 2 quiescent current ( a) 64 8 10 12 14 12 8 6 4 2 10 t a = +125 c t a = +25 c t a =?40 c 00163-006 figure 9. adr291 quiescent current vs. input voltage input voltage (v) 14 0 01 2 quiescent current ( a) 64 8 10 12 14 12 8 6 4 2 10 00163-007 t a = +125 c t a = +25 c t a =?40 c 6 figure 10. adr292 quiescent current vs. input voltage 14 12 4 10 8 6 adr291 adr292 temperature (c) ?50 125 ?25 0 25 50 75 100 00163-008 v s = 5v supply current (a) figure 11. adr291/adr292 supply current vs. temperature 100 80 0 60 40 20 temperature ( c) ?50 125 ?25 0 25 50 75 100 00163-009 line regulation (ppm/v) adr291 adr292 adr291: v s = 3.0v to 15v adr292: v s = 4.5v to 15v i out = 0 ma figure 12. adr291/adr292 line regulation vs. temperature
adr291/adr292 rev. f | page 9 of 20 100 80 0 60 40 20 temperature ( c) ?50 125 ?25 0 25 50 75 100 00163-010 adr292 adr291 line regulation (ppm/v) adr291: v s = 3.0v to 15v adr292: v s = 4.5v to 15v i out = 0 ma figure 13. adr291/adr292 line regulation vs. temperature load current (ma) differential voltage (v) 0.7 0 0 5.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 0.6 0.5 0.4 0.3 0.2 0.1 t a = +125 c t a = +25 c t a =?40 c 00163-011 figure 14. adr291 minimum input-output voltage differential vs. load current load current (ma) differential voltage (v) 0.7 0 0 5.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 0.6 0.5 0.4 0.3 0.2 0.1 00163-012 t a = +125 c t a = +25 c t a =?40 c figure 15. adr292 minimum input-output voltage differential vs. load current 200 160 0 120 80 40 temperature ( c) ?50 125 ?25 0 25 50 75 100 00163-013 load regulation (ppm/ma) v s = 5v i out = 1ma i out = 5ma figure 16. adr291 load regulation vs. temperature 200 160 0 120 80 40 temperature ( c) ?50 125 ?25 0 25 50 75 100 00163-014 load regulation (ppm/ma) v s = 5v i out = 1ma i out = 5ma figure 17. adr292 load regulation vs. temperature sourcing load current (ma) 0 ?1250 ?2000 0.1 10 1 ? v out from nomin a l (v) ?1750 ?1500 ?500 ?250 ?1000 ?750 t a = +125c t a = +25c t a = ?40c 00163-015 figure 18. adr291 v out from nominal vs. load current
adr291/adr292 rev. f | page 10 of 20 sourcing load current (ma) 0 ?2500 ?4000 0.1 10 1 ? v out from nomin a l (v) ?3500 ?3000 ?1000 ?500 ?2000 ?1550 00163-016 t a = +125c t a = +25c t a = ?40c figure 19. adr292 v out from nominal vs. load current frequency (hz) 1000 500 0 10 1000 100 voltage noise density (nv/ hz) 100 200 800 900 300 400 600 700 00163-017 adr291 adr292 v in = 15v t a = 25 c figure 20. voltage noise density vs. frequency frequency (hz) 120 60 0 10 1000 100 ripple rejection (db) 20 100 80 40 00163-018 v s = 5v figure 21. adr291/adr292 ripple rejection vs. frequency 10 0% 100 90 1s 2 v p-p 00163-019 figure 22. adr291 0.1 hz to 10 hz noise frequency (hz) 50 40 0 0 10k 10 output impedance ( ) 100 1k 30 20 10 v s = 5v i l = 0 ma 00163-020 figure 23. adr291 output impedance vs. frequency frequency (hz) 50 40 0 0 10k 10 output impedance ( ) 100 1k 30 20 10 v s = 5v i l = 0 ma 00163-021 figure 24. adr292 output impedance vs. frequency
adr291/adr292 rev. f | page 11 of 20 10 0% 100 90 1ms i l = 5ma 1v o ff on 00163-022 figure 25. adr291 load transient 10 0% 100 90 1ms i l = 5ma c l = 1nf 1v o ff on 00163-023 figure 26. adr291 load transient 10 0% 100 90 5ms i l = 5ma c l = 100nf 1v o ff on 00163-024 figure 27. adr291 load transient 10 0% 100 90 500 s i l = 5ma 1v 00163-025 figure 28. adr291 turn-on time 10 0% 100 90 10ms i l = 0ma 1v 00163-026 figure 29. adr291 turn-off time v out deviation (ppm) ? 200 0 frequency 8 6 4 2 10 14 12 16 18 ?180 ?160 ?140 ?120 ?100 ?80 ?60 ?40 ?20 0 20 40 60 80 100 120 140 160 180 200 more temperature +25 c ?40c +85c +25c 00163-027 figure 30. typical hysteresis for the adr291 product
adr291/adr292 rev. f | page 12 of 20 terminology line regulation line regulation refers to the change in output voltage due to a specified change in input voltage. it includes the effects of self- heating. line regulation is expressed as percent-per-volt, parts- per-million-per-volt, or microvolts-per-volt change in input voltage. load regulation the change in output voltage is due to a specified change in load current and includes the effects of self-heating. load regulation is expressed in microvolts-per-milliampere, parts- per-million-per-milliampere, or ohms of dc output resistance. long-term stability long-term stability refers to the typical shift of output voltage at 25c on a sample of parts subjected to a test of 1000 hours at 125c. ( ) ( ) [] () () () 6 10 ppm ? = ? = 0 out 1 out 0 out out 1 out 0 out out tv tvtv v t v t vv where: v out ( t 0 ) = v out at 25c at time 0. v out ( t 1 ) = v out at 25c after 1000 hours of operation at 125c. temperature coefficient temperature coefficient is the change of output voltage over the operating temperature change, normalized by the output voltage at 25c, expressed in ppm/c. the equation follows: [] ( )() () () 6 10 c25 cppm/ ? ? = 12 o 1 o 2 o o tt v tvtv tcv where: v out (25c) = v out at 25c. v out ( t 1 ) = v out at temperature 1. v out ( t 2 ) = v out at temperature 2. nc = no connect. there are internal connections at nc pins that are reserved for manufacturing purposes. users should not connect anything at the nc pins. thermal hysteresis thermal hysteresis is defined as the change of output voltage after the device is cycled through temperatures from +25c to ?40c, then to +85c, and back to +25c. this is a typical value from a sample of parts put through such a cycle. 6 10 c)25( )25( [ppm] c)25( ? = ?= ? ? out out_tc out hysut out_tc out hysout v vcv v v v v where: v out (25c) = v out at 25c. v out _ tc = v out at 25c after temperature cycle from +25c to ?40c, then to +85c, and back to +25c.
adr291/adr292 rev. f | page 13 of 20 theory of operation the adr291/adr292 series of references uses a reference generation technique known as xfet (extra implanted junc- tion fet). this technique yields a reference with low noise, low supply current, and very low thermal hysteresis. the core of the xfet reference consists of two junction field effect transistors, one having an extra channel implant to raise its pinch-off voltage. by running the two jfets at the same drain current, the difference in pinch-off voltage can be amplified and used to form a highly stable voltage reference. the intrinsic reference voltage is around 0.5 v with a negative temperature coefficient of about ?120 ppm/k. this slope is essentially locked to the dielectric constant of silicon and can be closely compensated by adding a correction term generated in the same fashion as the proportional-to-temperature (ptat) term used to compensate band gap references. because most of the noise of a band gap reference comes from the compensation circuitry, the intrinsic temperature coefficient offers a significant advan- tage (being about 30 times lower), and therefore, requiring less correction resulting in much lower noise. the simplified schematic in figure 31 shows the basic topology of the adr291/adr292 series. the temperature correction term is provided by a current source with a value designed to be proportional to absolute temperature. the general equation is ()( 3 1 321 ri r rrr vv ptat p out + ? ? ? ? ? ? ++ = ) where: v p is the difference in pinch-off voltage between the two fets. i ptat is the positive temperature coefficient correction current. the various versions of the adr291/adr292 family are created by on-chip adjustment of r1 and r3 to achieve 2.500 v or 4.096 v at the reference output. the process used for the xfet reference also features vertical npn and pnp transistors, the latter of which are used as output devices to provide a very low dropout voltage. v out v in i ptat gnd r1 r2 r3 i 1 i 1 1 1 extra channel implant v out = v p = i ptat r3 r1 + r2 + r3 r1 v p 00163-028 figure 31. adr291/adr292 simplified schematic device power dissipation considerations the adr291/adr292 family of references is guaranteed to deliver load currents to 5 ma with an input voltage that ranges from 2.7 v to 15 v (minimum supply voltage depends on the output voltage chosen). when these devices are used in applications with large input voltages, care should be exercised to avoid exceeding the published specifications for maximum power dissipation or junction temperature that could result in premature device failure. use the following formula to calculate maximum junction temperature or dissipation of a device: ja a j d tt p ? = where t j and t a are the junction and ambient temperatures, respectively. p d is the device power dissipation. ja is the device package thermal resistance. basic voltage reference connections references, in general, require a bypass capacitor connected from the v out pin to the gnd pin. the circuit in figure 32 illustrates the basic configuration for the adr291/adr292 family of references. note that the decoupling capacitors are not required for circuit stability. nc nc nc nc v out nc 0.1f 0.1f 10f + nc = no connect 1 2 3 4 8 7 6 5 00163-029 adr291/ adr292 figure 32. basic voltage reference configuration noise performance the noise generated by the adr291/adr292 family of refer- ences is typically less than 12 v p-p over the 0.1 hz to 10 hz band. the noise measurement is made with a band-pass filter made of a 2-pole high-pass filter with a corner frequency at 0.1 hz and a 2-pole low-pass filter with a corner frequency at 10 hz. turn-on time upon application of power (cold start), the time required for the output voltage to reach its final value within a specified error band is defined as the turn-on settling time. two com- ponents normally associated with this are the time it takes for the active circuits to settle and for the thermal gradients on the chip to stabilize. figure 28 shows the turn-on settling time for the adr291.
adr291/adr292 rev. f | page 14 of 20 applications information high voltage floating current source the circuit shown in figure 33 can be used to generate a floating current source with minimal self-heating. this particular configuration operates on high supply voltages determined by the breakdown voltage of the n-channel jfet. gnd 2 4 + v s adr291/ adr292 v in e231 siliconix 2n3904 2.10k ? ?v s op90 00163-032 figure 33. high voltage floating current source kelvin connections in many portable instrumentation applications, the pc board area is directly related to cost; therefore, circuit interconnects are reduced to a minimal width. these narrow lines can cause large voltage drops if the voltage reference is required to provide load currents to various functions. in fact, circuit interconnects can exhibit a typical line resistance of 0.45 m/square (1 oz. cu, for example). force and sense connections, also referred to as kelvin connections, offer a convenient method of eliminating the effects of voltage drops in circuit wires. load currents flowing through wiring resistance produce an error (v error = r i l ) at the load. however, the kelvin connection shown in figure 34 overcomes the problem by including the wiring resistance within the forcing loop of the op amp. since the op amp senses the load voltage, the op amp loop control forces the output to compensate for the wiring error producing the correct voltage at the load. a1 1f 100k? +v out sense a1 = 1/2 op295 v in r lw r l r lw +v out force v out gnd v in 2 6 4 00163-033 adr291/ adr292 figure 34. advantage of kelvin connection low power, low voltage reference for data converters the adr291/adr292 family has a number of features that makes it ideally suited for use with analog-to-digital and digital- to-analog converters. because of its low supply voltage, the adr291 can be used with converters that run on 3 v supplies without having to add a higher supply voltage for the reference. the low quiescent current (12 a maximum) and low noise, tight temperature coefficient, combined with the high accuracy of the adr291/adr292, make it ideal for low power applica- tions such as handheld, battery-operated equipment. one such adc for which the adr291 is well suited is the ad7701. figure 35 shows the adr291 used as the reference for this converter. the ad7701 is a 16-bit adc with on-chip digital filtering intended for the measurement of wide dynamic range, low frequency signals such as those representing chemical, physical, or biological processes. it contains a charge balancing (-) adc, calibration microcontroller with on-chip static ram, a clock oscillator, and a serial communications port. this entire circuit runs on 5 v supplies. the power dissipation of the ad7701 is typically 25 mw and, when combined with the power dissipation of the adr291 (60 w), the entire circuit still consumes about 25 mw. bp/up cal v ref a in agnd av ss av dd dv dd sleep mode drdy sclk cs sdata clkin clkout sc1 sc2 dgnd dv ss 0.1f data ready read (transmit) serial clock serial clock 0.1f 10f 0.1f ?5v analog supply +5 v analog supply analog ground analog input calibrate ranges select 0.1f adr291 0.1f gnd v in v out 10f 0.1f ad7701 00163-034 figure 35. low power, low voltage supply reference for the ad7701
adr291/adr292 rev. f | page 15 of 20 voltage regulator for portable equipment the adr291/adr292 family of references is ideal for provid- ing a stable, low cost, and low power reference voltage in portable equipment power supplies. figure 36 shows how the adr291 and adr292 can be used in a voltage regulator that not only has low output noise (as compared to switch mode design) and low power, but also a very fast recovery after current surges. some precautions should be taken in the selection of the output capacitors. too high an esr (effective series resistance) could endanger the stability of the circuit. a solid tantalum capacitor, 16 v or higher, and an aluminum electrolytic capacitor, 10 v or higher, are recommended for c1 and c2, respectively. also, the path from the ground side of c1 and c2 to the ground side of r1 should be kept as short as possible. v out nc gnd v in 0.1f lead-acid battery + 6v charger input r1 402k ? 1% r2 402k ? 1% + c2 1000f elect c1 68f tant + 5v, 100ma irf9530 op20 2 6 2 7 6 4 3 3 4 0 0163-035 adr291/ adr292 r3 510k ? figure 36. voltage regulator for portable equipment
adr291/adr292 rev. f | page 16 of 20 outline dimensions controlling dimensions are in millimeters; inch dimensions (in parentheses) are rounded-off millimeter equivalents for reference only and are not appropriate for use in design. compliant to jedec standards ms-012-a a 012407-a 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157) 0.50 (0.0196) 0.25 (0.0099) 45 8 0 1.75 (0.0688) 1.35 (0.0532) seating plane 0.25 (0.0098) 0.10 (0.0040) 4 1 85 5.00 (0.1968) 4.80 (0.1890) 4.00 (0.1574) 3.80 (0.1497) 1.27 (0.0500) bsc 6.20 (0.2441) 5.80 (0.2284) 0.51 (0.0201) 0.31 (0.0122) coplanarity 0.10 figure 37. 8-lead standard small outline package [soic_n] narrow body (r-8) dimensions shown in millimeters and (inches) 8 5 41 pin 1 0.65 bsc seating plane 0.15 0.05 0.30 0.19 1.20 max 0.20 0.09 8 0 6.40 bsc 4.50 4.40 4.30 3.10 3.00 2.90 coplanarit y 0.10 0.75 0.60 0.45 compliant to jedec standards mo-153-aa figure 38. 8-lead thin shrink small outline package [tssop] (ru-8) dimensions shown in millimeters controlling dimensions are in inches; millimeter dimensions (in parentheses) are rounded-off equivalents for reference only and are not appropriate for use in design. compliant to jedec standards to-226-aa 0.115 (2.92) 0.080 (2.03) 0.115 (2.92) 0.080 (2.03) 0.165 (4.19) 0.125 (3.18) 1 2 3 bottom view sq 0.019 (0.482) 0.016 (0.407) 0.105 (2.66) 0.095 (2.42) 0.055 (1.40) 0.045 (1.15) seating plane 0.500 (12.70) min 0.205 (5.21) 0.175 (4.45) 0.210 (5.33) 0.170 (4.32) 0.135 (3.43) min 0.050 (1.27) max figure 39. 3-lead plastic header-style package [to-92] (t-3) dimensions shown in inches and (millimeters)
adr291/adr292 rev. f | page 17 of 20 ordering guide model 1 output voltage initial accuracy (%) temperature coefficient max (ppm/c) package description package option ordering quantity adr291erz 2.50 0.08 8 8-lead soic_n r-8 98 adr291erz-reel7 2.50 0.08 8 8-lead soic_n r-8 1,000 adr291frz 2.50 0.12 15 8-lead soic_n r-8 98 adr291frz-reel 2.50 0.12 15 8-lead soic_n r-8 2,500 adr291frz-reel7 2.50 0.12 15 8-lead soic_n r-8 1,000 adr291grz 2.50 0.24 25 8-lead soic_n r-8 98 adr291grz-reel 2.50 0.24 25 8-lead soic_n r-8 2,500 adr291grz-reel7 2.50 0.24 25 8-lead soic_n r-8 1,000 adr291gruz 2.50 0.24 25 8-lead tssop ru-8 98 adr291gruz-reel 2.50 0.24 25 8-lead tssop ru-8 1,000 adr291gruz-reel7 2.50 0.24 25 8-lead tssop ru-8 1,000 adr291gt9z 2.50 0.24 25 3-lead to-92 t-3 98 ADR292ERZ 4.096 0.07 8 8-lead soic_n r-8 98 ADR292ERZ-reel 4.096 0.07 8 8-lead soic_n r-8 2,500 adr292frz 4.096 0.10 15 8-lead soic_n r-8 98 adr292frz-reel 4.096 0.10 15 8-lead soic_n r-8 2,500 adr292frz-reel7 4.096 0.10 15 8-lead soic_n r-8 1,000 adr292grz 4.096 0.15 25 8-lead soic_n r-8 98 adr292grz-reel7 4.096 0.15 25 8-lead soic_n r-8 1,000 adr292gruz 4.096 0.24 25 8-lead tssop ru-8 98 adr292gruz-reel7 4.096 0.15 25 8-lead tssop ru-8 1,000 1 z = rohs compliant part.
adr291/adr292 rev. f | page 18 of 20 notes
adr291/adr292 rev. f | page 19 of 20 notes
adr291/adr292 rev. f | page 20 of 20 notes ?2007C2011 analog devices, inc. all rights reserved. trademarks and registered trademarks are the property of their respective owners. d00163-0-5/11(f)

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