1.2875 v micropower, shunt voltage reference adr1500 rev. 0 information furnished by analog devices is believed to be accurate and reliable. however, no responsibility is assumed by analog devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. specifications subject to change without notice. no license is granted by implication or otherwise under any patent or patent rights of analog devices. trademarks and registered trademarks are the property of their respective owners. one technology way, p.o. box 9106, norwood, ma 02062-9106, u.s.a. tel: 781.329.4700 www.analog.com fax: 781.461.3113 ?2006 analog devices, inc. all rights reserved. features wide operating range: 50 a to 10 ma initial accuracy: 0.2% max output impedance: 1 max wideband noise (10 hz to 10 khz): 20 v rms operating temperature: ?40c to +85c compact, surface-mount sc70 package applications computer servers battery-powered instrumentation portable medical equipment automotive pin configuration 05749-001 v? 1 v + 2 nc (or v?) 3 top view (not to scale) nc = no connect a dr1500 figure 1. 3-lead sc70 (ks suffix) general description the adr1500 is a low cost, 2-terminal (shunt), precision band gap reference. it provides an accurate 1.2875 v output for input currents between 50 a to 10 ma. the low minimum operating current makes the adr1500 ideal for use in battery-powered 3 v or 5 v systems. however, the wide operating current range means the adr1500 is extremely versatile and suitable for use in a wide variety of high current applications. the adr1500 is available in the tiny sc70 package and is specified over the ?40c to +85c operating temperature range.
adr1500 rev. 0 | page 2 of 8 table of contents features .............................................................................................. 1 applications ....................................................................................... 1 pin configuration ............................................................................. 1 general description ......................................................................... 1 revision history ............................................................................... 2 specifications ..................................................................................... 3 electrical characteristics ............................................................. 3 absolute maximum ratings ............................................................ 4 esd caution .................................................................................. 4 typical performance characteristics ..............................................5 theory of operation .........................................................................6 applying the adr1500 ................................................................6 tur n-o n ti me ...............................................................................6 transient response .......................................................................7 outline dimensions ..........................................................................8 ordering guide .............................................................................8 revision history 1/06revision 0: initial version
adr1500 rev. 0 | page 3 of 8 specifications electrical characteristics t a = 25c, i in = 100 a, unless otherwise noted. table 1. parameter min typ max unit reverse voltage output 1.2849 1.2875 1.2901 v reverse voltage temperature drift, ?40c to +85c 170 220 ppm/c minumum operating current, ?40c to +85c 50 a reverse voltage change with reverse current 50 a < i in < 10 ma, ?40c to +85c 3.0 6 mv 50 a < i in < 1 ma, ?40c to +85c 0.7 mv dynamic output impedance (v r /i r ) i in = 1 ma 100 a (f = 120 hz) 0.4 1 output noise rms noise voltage: 10 hz to 10 khz 20 v rms low frequency noise voltage: 0.1 hz to 10 hz 5 v p-p turn-on settling time to 0.1%, no c out 5 s output voltage hysteresis 80 v temperature range specified range ?40 +85 c operating range ?55 +125 c
adr1500 rev. 0 | page 4 of 8 absolute maximum ratings table 2. parameter rating reverse current 25 ma forward current 20 ma sc70 (ks) package dissipation ja 376c/w jc 189c/w storage temperature range ?65c to +150c operating temperature range ?55c to +150c lead temperature, soldering vapor phase (60 sec) 215c infrared (15 sec) 220c 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. esd caution esd (electrostatic discharge) sensitive device. electros tatic charges as high as 4000 v readily accumulate on the human body and test equipment and can discharge wi thout 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 precautions are recommended to avoid performance degradation or loss of functionality.
adr1500 rev. 0 | page 5 of 8 typical performance characteristics 1.310 1.305 1.300 1.295 1.290 1.285 1.280 1.275 1.270 ?50 125 100 75 50 25 0 ?25 05749-002 reverse voltage (v) temperature (c) figure 2. output drift for different temperature characteristics 6 5 4 3 2 1 0 ?1 ?2 0.01 10 1 0.1 05749-003 output voltage error (mv) reverse current (ma) +125c +85c +25c ?40c figure 3. output voltage error vs. reverse current 1000 100 10 1 1 1000000 100 1000 10000 100000 10 05749-004 noise voltage (nv/ hz) frequency (hz) figure 4. noise spectral density 100 80 60 40 20 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 05749-005 reverse current (a) reverse voltage (v) +85c +25c ?40c figure 5. reverse current vs. reverse voltage 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0.01 100 11 0 0.1 05749-006 forward voltage (v) forward current (ma) ?40c +85c +25c figure 6. forward voltage vs. forward current
adr1500 rev. 0 | page 6 of 8 theory of operation the adr1500 uses the band gap concept to produce a stable voltage reference suitable for high accuracy data acquisition components and systems. this device makes use of the underlying physical nature of the silicon transistor base emitter voltage in the forward-biased operating region. all such transistors have an approximate ?2 mv/c temperature coefficient, which is not suitable for use as a low tc reference; however, extrapolation of the temperature characteristic of any one of these devices to absolute zero (with collector current proportional to absolute temperature) reveals that v be goes to approximately the silicon band gap voltage. therefore, if a voltage could be developed with an opposing temperature coefficient to the sum with the v be , than a zero tc reference would result. the adr1500 circuit in figure 7 provides such a compensating voltage, v1, by deriving two transistors at different current densities and amplifying the resultant v be difference (v be , which has a positive tc). the sum of the v be and v1 provides a stable voltage reference. 05749-008 v+ v? + v be v be ? + ? v1 + ? figure 7. sche matic diagram applying the adr1500 the adr1500 is simple to use in virtually all applications. to operate the adr1500 as a conventional shunt reference, see figure 8 . an external series resistor is connected between the supply voltage and the adr1500. for a given supply voltage, the series resistor, r s , determines the reverse current flowing through the adr1500. the value of r s must be chosen to accommodate the expected variations of the supply voltage, v s , load current, i l , and the adr1500 reverse voltage, v r , while maintaining an acceptable reverse current, i r , through the adr1500. the minimum value for r s should be enough to limit i r to 10 ma when v s is at its maximum, and i l and v r are at their minimum. the equation for selecting r s is )( )( lr r s s ii vv r + ? = 05749-009 (a) r s v s v r i r + i l v out i r + ? i l (b) r s +5v (+3v) 10% v r 2.94k ? (1.30k ? ) v ou t + ? figure 8. typical connection diagram figure 8 shows a typical connection of the adr1500 operating at a minimum of 100 a. this connection can provide 1 ma to the load, while accommodating 10% power supply variations. turn-on time the turn-on time is a critical parameter for applications demanding a large amount of processing. figure 9 shows the turn-on characteristics of the adr1500. 05749-010 250mv/div 5s/div 2.4v 0v v in c l = 200pf figure 9. response time upon application of power (cold start), the time required for the output voltage to reach its final value within a specified error is the turn-on settling time. tow components are normally associated with the time for active circuits to settle and the time for the thermal gradients on the chip to stabilize. this characteristic is generated from cold start operation and represents the true turn-on waveform after power up. figure 10 shows both the course and fine turn-on settling characteristics of the device; the total settling time to within 1.0 mv is about 6 s, and there is no long thermal tail when the horizontal scale is expanded to 2 s/div. the output turn-on time is modified when an external noise reduction filter is used. when present, the time constant of the filter dominates the overall settling.
adr1500 rev. 0 | page 7 of 8 05749-011 output error 1mv/div 2s/div output 0.5mv/div 2ms/div 2.4v 0v v in figure 10. turn-on settling time attempts to drive a large capacitive load (in excess of 1000 pf) can result in ringing. this is due to the additional poles formed by the load capacitance and the output impedance of the reference. a recommended method for driving capacitive loads of this magnitude is shown in figure 11 . 05749-012 + ? v r v out c l r s = 11.5k ? v in r l figure 11. turn-on, settling, and transient test circuit transient response many adcs and dacs present transient current loads to the reference. poor reference response can degrade the converters performance. figure 12 displays both the coarse and fine settling characteristics of the device to load transient of 50 a. it shows the settling characteristics of the device for an increased reverse current of 50 a and the response when the reverse current is decreased by 50 a. the transients settle to 1 mv in about 3 s. 05749-013 i r = 100a + 50a step i r = 100a ? 50a step 1s/div 20mv/div 1mv/div 20mv/div 1mv/div figure 12. transient settling time a resistor isolates the capacitive load from the output stage, while the capacitor provides a single-pole, low-pass filter and lowers the output noise.
adr1500 rev. 0 | page 8 of 8 outline dimensions all dimensions compliant with eiaj sc70 0.40 0.25 0.10 max 1.00 0.80 seating plane 1.10 0.80 0.40 0.10 0.26 0.10 0.30 0.20 0.10 2 1 3 pin 1 0.65 bsc 2.20 2.00 1.80 2.40 2.10 1.80 1.35 1.25 1.15 0.10 coplanarity 111505-0 figure 13. 3-lead thin shrink small outline transistor package [sc70] (ks-3) dimensions shown in millimeters ordering guide model initial output error temperature coefficient (typ) temperature range package description package option branding ADR1500BKSZ-REEL 1 2.6 mv 170 ppm/c ?40c to +85c 3-lead sc70 ks-3 r2f 1 z = pb-free part. ?2006 analog devices, inc. all rights reserved. trademarks and registered trademarks are the property of their respective owners. d05749-0-1/06(0)
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