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ANALOG DEVICES ADR290/ADR291/ADR292 Low Noise Micropower 2.048 V 2.5 V 4.096 V Precision Voltage References handbook

1. 125 C unless otherwise noted Parameter Symbol Conditions Min Typ Max Unit TEMPERATURE COEFFICIENT E Grade TCVo Ilour 0 mA 3 10 ppm C F Grade 5 20 ppm C G Grade 10 30 ppm C LINE REGULATION E F Grades AVo AVin 4 5 V to 15 V Ioyr 0 mA 40 200 ppm V G Grade 70 250 ppm V LOAD REGULATION E F Grades AVo Al ioap Vg 5 0 V 0 mA to 5 mA 20 200 ppm mA G Grade 30 300 ppm mA SUPPLY CURRENT Is Ta 25 C 10 15 uA 40 C Ta 125 C 12 18 UA THERMAL HYSTERESIS Vo Hys SO 8 TSSOP 8 50 ppm Specifications subject to change without notice 4 REV B ADR290 ADR291 ADR292 ABSOLUTE MAXIMUM RATINGS Package Type 0 at Dic Unit Supply Voltage 4s ve rre ee NR d 18V Output Short Circuit Duration to GND Indefinite 8 Lead SOIC SO 158 43 C W Storage Tempeidrure Runge 8 Lead TSSOP RU 240 43 C W SO RU Package 65 C to 150 C fra is specified for worst case conditions i e Di is specified for device in socket Operating Temperature Range testing In practice Dr is specified for a device soldered in the circuit board ADR290 ADR291 ADR292 40 C to 125 C Junction Temperature Range SO RU Package 65 C to 125 C Lead Temperature Soldering 60 sec 300 C NOTES 1 Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device This is a stress rating only functional operation at or
2. gt j je SEATING cone eao 0 0079 0 20 0 028 0 70 PLANE 0 0 19 0 0035 0 090 0 020 0 50 REV B 15 C00163 0 3 01 B PRINTED IN U S A
3. NC NO CONNECT current is only 12 uA 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 max for the ADR290 and ADR291 and 3 mV 4 mV and t6 mV max for the ADR292 Temperature coefficients for the three grades are 8 ppm C 15 ppm C and 25 ppm C max respectively Line regulation and load regulation are typically 30 ppm V and 30 ppm mA maintaining the reference s overall high performance For a device with 5 0 V output refer to the ADR293 data sheet The ADR290 ADR291 and ADR292 references are specified over the extended industrial temperature range of 40 C to 125 C Devices are available in the 8 lead SOIC and 8 lead TSSOP packages ADR29x Product Output Voltage Initial Accuracy Temperature Coefficient Part Number V 9o ppm C Max ADR290 2 048 0 10 0 15 0 29 8 15 25 ADR291 2 500 0 08 0 12 0 24 8 15 25 ADR292 4 096 0 07 0 10 0 15 8 15 25 ADR293 5 000 See ADR293 Data Sheet XFET is a registered trademark of Analog Devices Inc REV B Information furnished by Analog Devices is believed to be accurate and reliable However no responsibility is assumed by Analog Devices for its use nor for any infringements of patents or other rights of third parties which may result from its use No license is granted by implication or otherwise under any patent or patent rights of An
4. 98 1000 2500 FR FR REEL7 FR REEL 4 096 0 10 15 SOIC SO 8 98 1000 2500 GR GR REEL7 GR REEL 4 096 0 15 25 SOIC SO 8 98 1000 2500 GRU REEL7 GRU REEL 4 096 0 15 25 TSSOP RU 8 1000 2500 See ADR293 data sheet for ordering guide OTHER XFET PRODUCTS Part Nominal Output Package Number Voltage V Type ADR420 2 048 8 Lead uSOIC SOIC ADR421 2 50 8 Lead_uwSOIC SOIC REV B b ADR290 ADR291 ADR292 PARAMETER DEFINITION Line Regulation The change in output voltage due to a specified change in input voltage It includes the effects of self heating Line regulation is expressed in either percent per volt parts per million per volt or microvolts per volt change in input voltage Load Regulation The change in output voltage due to a specified change in load current It includes the effects of self heating Load regulation is expressed in either microvolts per milliampere parts per million per milliampere or ohms of dc output resistance Long Term Stability Typical shift of output voltage at 25 C on a sample of parts subjected to high temperature operating life test of 1000 hours at 125 C AVo Vo to Vo t _ Vo to Van x 10 Vo to AVo ppm Where Vo to Vo at 25 C at time 0 Vo t Vo at 25 C after 1000 hours operation at 125 C Temperature Coefficient The change of output voltage over the operating temperature change and normalized by the output voltage at 25 C expressed in ppm C
5. Basic Voltage Reference Connections References in general require a bypass capacitor connected from the Vor pin to the GND pin The circuit in Figure 2 illustrates the basic configuration for the ADR29x family of ref erences Note that the decoupling capacitors are not required for circuit stability NC lt NO CONNECT Figure 2 Basic Voltage Reference Configuration Noise Performance The noise generated by the ADR29x family of references is typi cally less than 12 uV p p over the 0 1 Hz to 10 Hz band TPC 21 shows the 0 1 Hz to 10 Hz noise of the ADR290 which is only 6 uV p p The noise measurement is made with a bandpass 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 components nor mally associated with this are the time for the active circuits to settle and the time for the thermal gradients on the chip to sta bilize TPC 28 shows the turn on settling time for the ADR291 REV B ADR290 ADR291 ADR292 APPLICATIONS SECTION A Negative Precision Reference without Precision Resistors In many current output CMOS DAC applications where the output signal voltage must be of the same polarity as the reference voltage it is often required to rec
6. V Inu r 0 mA 35 125 ppm V G Grade 50 150 ppm V LOAD REGULATION E F Grades AVo Alioap Vs 5 0 V 0 mA to 5 mA 20 125 ppm mA G Grade 30 150 ppm mA ELECTRICAL SPECIFICATIONS w 2 7 v T 40 c lt T 1257 unless otherwise noted Parameter Symbol Conditions Min Typ Max Unit TEMPERATURE COEFFICIENT E Grade TCVo Ionut 0 mA 3 10 ppm C F Grade 5 20 ppm C G Grade 10 30 ppm C LINE REGULATION E F Grades AVo AVin 2 7 V to 15 V Inu r 0 mA 40 200 ppm V G Grade 70 250 ppm V LOAD REGULATION E F Grades AVo Alioap Vg 5 0 V 0 mA to 5 mA 20 200 ppm mA G Grade 30 300 ppm mA SUPPLY CURRENT Is Ta 25 C 8 12 uA 40 C Ta 125 C 12 15 UA THERMAL HYSTERESIS Notes SO 8 TSSOP 8 50 ppm Specifications subject to change without notice 2 REV B ADR291 SPECIFICATIONS ELECTRICAL SPEC IFICATIONS V 3 0 V T 25 C unless otherwise noted ADR290 ADR291 ADR292 Parameter Symbol Conditions Min Typ Max Unit E GRADE Output Voltage Vo Iour 0 mA 2 498 2 500 2 502 V Initial Accuracy VoERR 2 2 mV 0 08 0 08 F GRADE Output Voltage Vo lout 0 mA 2 497 2 500 2 503 V Initial Accuracy VoERR 3 3 mV 0 12 0 12 G GRADE Output Voltage Vo lour 0 mA 2 494 2 500 2 506 V Initial Accuracy VoERR 6 6 mV 0 24 0 24 LINE REGULATION E F Grades AV o AV N 3 0 V to 15
7. 0 25 0 25 50 75 100 125 REV B TEMPERATURE C TPC 3 ADR292 Voyr vs Temperature Ta 125 C QUIESCENT CURRENT pA 0 2 4 6 8 10 12 14 16 INPUT VOLTAGE V TPC 4 ADR290 Quiescent Current vs Input Voltage 125 C QUIESCENT CURRENT pA 0 2 4 6 8 10 12 14 16 INPUT VOLTAGE V TPC 5 ADR291 Quiescent Current vs Input Voltage 16 14 o lt 12 TA 125 C I E 10 Ta 25 C rd 5 E Ta 40 C gt 8 o 5 u 6 o 5 4 o 2 0 0 2 4 6 8 10 12 14 16 INPUT VOLTAGE V TPC 6 ADR292 Quiescent Current vs Input Voltage ADR290 ADR291 ADR292 125 C SUPPLY CURRENT pA DIFFERENTIAL VOLTAGE V 0 05 1 015 20 25 30 35 40 45 5 0 TEMPERATURE C LOAD CURRENT mA TPC 7 ADR290 ADR291 ADR292 Supply Current vs TPC 10 ADR290 Minimum Input Output Voltage Temperature Differential vs Load Current 100 ADR290 Vs 2 7V TO 15V ADR291 Vs 3 0V TO 15V ADR292 Vs 4 5V TO 15V 80 a w S 2 z 60 5 o o F gt 3 d lt 3 40 z c m ul w 5 20 a 0 50 0 0 5 10 15 20 25 30 35 40 45 50 TEMPERATURE C LOAD CURR
8. 92 SPECIFICATIONS ELECTRICAL SPEC IFICATIONS V 5 V T 25 C unless otherwise noted Parameter Symbol Conditions Min Typ Max Unit E GRADE Output Voltage Vo lour 0 mA 4 0903 4 096 4 099 V Initial Accuracy VoERR 3 3 mV 0 07 0 07 F GRADE Output Voltage Vo lout 0 mA 4 092 4 096 4 1 V Initial Accuracy VOERR 4 4 mV 0 10 0 10 G GRADE Output Voltage Vo Iour 0 mA 4 090 4 096 4 102 V Initial Accuracy VoERR 6 6 mV 0 15 0 15 LINE REGULATION E F Grades AVo AVin 4 5 V to 15 V Iour 0 mA 30 100 ppm V G Grade 40 125 ppm V LOAD REGULATION E F Grades AVo lAl ioap Vs 5 0 V 0 mA to 5 mA 30 100 ppm mA G Grade 40 125 ppm mA LONG TERM STABILITY AVo After 1000 hrs of Operation 125 C 50 ppm NOISE VOLTAGE en 0 1 Hz to 10 Hz 12 UN p p WIDEBAND NOISE DENSITY en 1 kHz 640 nV VHz ELECTRICAL SPECIFICATIONS w 5 v T 25 c lt T lt 85 C unless otherwise noted Parameter Symbol Conditions Min Typ Max Unit TEMPERATURE COEFFICIENT E Grade TCVo Iour 0 mA 3 8 ppm C F Grade 5 15 ppm C G Grade 10 25 ppm C LINE REGULATION E F Grades AVo AVim 4 5 V to 15 V Iour 0 mA 35 125 ppm V G Grade 50 150 ppm V LOAD REGULATION E F Grades AVo Al ioap Vs 5 0 V 0 mA to 5 mA 20 125 ppm mA G Grade 30 150 ppm mA ELECTRICAL SPEC IFICATIONS V 5 V Ty 40 C lt T lt
9. C board cost and area go hand in hand circuit interconnects are very often of dimensionally minimum width These narrow lines can cause large voltage drops if the voltage reference is required to provide load currents to various functions In fact a circuit s interconnects can exhibit a typical line resistance of 0 45 mQ 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 Vggnon R X Ij at the load However the Kelvin connection of Figure 6 overcomes the problem by including the wiring resistance within the forcing loop of the op amp Since the op amp senses the load voltage op amp loop control forces the output to compensate for the wiring error and to produce the correct voltage at the load DER ADR290 ADR291 ADR292 ViN Voltage Regulator For Portable Equipment The ADR29x family of references is ideal for providing a stable low cost and low power reference voltage in portable equipment power supplies Figure 8 shows how the ADR290 ADR291 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 out put capacitors Too high an ESR Effective Series Resistan
10. ENT mA TPC 8 ADR290 ADR291 ADR292 Line Regulation vs TPC 11 ADR291 Minimum Input Output Voltage Temperature Differential vs Load Current 100 ADR290 Vg 2 7V TO 7 0V ADR291 Vg 3 0V TO 7 0V ADR292 Vg 4 5V TO 9 0V 80 gt a U S 2 z 60 S o ADR290 o E gt q E 5 y 5 40 z S Z 20 2 0 50 25 0 25 50 75 100 125 0 0 5 10 15 20 25 30 35 40 45 5 0 TEMPERATURE C LOAD CURRENT mA TPC 9 ADR290 ADR291 ADR292 Line Regulation vs TPC 12 ADR292 Minimum Input Output Voltage Temperature Differential vs Load Current 8 REV B ADR290 ADR291 ADR292 LINE REGULATION ppm mA A Vout FROM NOMINAL pV TEMPERATURE C SOURCING LOAD CURRENT mA TPC 13 ADR290 Line Regulation vs Temperature TPC 16 ADR290 AV our from Nominal vs Load Current LOAD REGULATION ppm mA A Vour FROM NOMINAL pV 0 1 1 10 TEMPERATURE C SOURCING LOAD CURRENT mA TPC 14 ADR291 Load Regulation vs Temperature TPC 17 ADR291 AVour from Nominal vs Load Current 200 160 x i 1 E a Ta 40 C I z J 120 o o E z 2 8 SCH g 5 E 2 S 40 4 0 50 25 0 25 50 75 100 125 0 1 1 10 TEMPERATURE C SOURCING LOAD CURRENT mA TPC 15 ADR292 Load Regulation vs Temperature TPC 18 ADR292 AVour from Nominal vs Load Curren
11. TPC 30 Typical Hysteresis for the ADR291 Product ADR290 ADR291 ADR292 THEORY OF OPERATION The ADR29x series of references uses a new reference generation technique known as XFET eXtra implanted junction 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 of which has 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 bandgap references The big advantage over a bandgap reference is that the intrinsic temperature coeffi cient is some thirty times lower therefore less correction is needed and this results in much lower noise since most of the noise of a bandgap reference comes from the temperature com pensation circuitry The simplified schematic below shows the basic topology of the ADR29x series The temperature correction term is provided by a current source with value designed to be proportional to abso
12. The equation follows Vo Voh Vo 25 C x 12 Ti TCVo ppm C x 10 Where Vo 25 C Vo at 25 C Vo Tj Vo at Temperature 1 Vo T3 Vo at Temperature 2 NC No Connect There are in fact internal connections at NC pins which are reserved for manufacturing purposes Users should not connect anything at NC pins Thermal Hysteresis Thermal hysteresis is defined as the change of output voltage af ter the device is cycled through temperature from 25 C to 40 C to 85 C and back to 25 C This is a typical value from a sample of parts put through such a cycle Ho vs Vo 25 C ze Vo ze Vo 25 C Vo mo Vo 25 C x 10 Vo nysl ppm Where Vo 25 C Vo at 25 C Vo_tc Vo at 25 C after temperature cycle at 25 C to 40 C to 85 C and back to 25 C REV B Typical Performance Characteristic ADR290 ADR291 ADR292 2 054 2 052 2 050 2 048 2 046 OUTPUT VOLTAGE V 2 044 2 042 Vs 5V 3 TYPICAL PARTS pe 50 25 0 25 50 75 100 125 2 506 2 504 2 502 2 500 2 498 OUTPUT VOLTAGE V 2 496 TEMPERATURE C TPC 1 ADR290 Voy vs Temperature 3 TYPICAL PARTS 50 25 0 25 50 75 100 125 4 102 4 100 4 098 4 096 4 094 OUTPUT VOLTAGE V 4 092 TEMPERATURE C TPC 2 ADR291 Voy vs Temperature 3 TYPICAL PARTS 5
13. V Iour 0 mA 30 100 ppm V G Grade 40 125 ppm V LOAD REGULATION E F Grades AVo AItoap Vs 5 0 V 0 mA to 5 mA 30 100 ppm mA G Grade 40 125 ppm mA LONG TERM STABILITY AVo After 1000 hrs of Operation 125 C 50 ppm NOISE VOLTAGE en 0 1 Hz to 10 Hz 8 UN p p WIDEBAND NOISE DENSITY en 1 kHz 480 nV VHz ELECTRICAL SPECIFICATIONS v 3 0 V T 25 c lt T lt 85 C unless otherwise noted Parameter Symbol Conditions Min Typ Max Unit TEMPERATURE COEFFICIENT E Grade TCVo lour 0 mA 3 8 ppm C F Grade 5 15 ppm C G Grade 10 25 ppm C LINE REGULATION E F Grades AVo AVin 3 0 V to 15 V Ioyy 0 mA 35 125 ppm V G Grade 50 150 ppm V LOAD REGULATION E F Grades AVo AlLoap Vs 5 0 V 0 mA to 5 mA 20 125 ppm mA G Grade 30 150 ppm mA ELECTRICAL SPEC IFICATIONS V 3 0 V T 40 C lt T lt 125 unless otherwise noted Parameter Symbol Conditions Min Typ Max Unit TEMPERATURE COEFFICIENT E Grade TCVo lour 0 mA 3 10 ppm C F Grade 5 20 ppm C G Grade 10 30 ppm C LINE REGULATION E F Grades AV o AV N 3 0 V to 15 V Ioyy 0 mA 40 200 ppm V G Grade 70 250 ppm V LOAD REGULATION E F Grades AVo Alioap Vs 5 0 V 0 mA to 5 mA 20 200 ppm mA G Grade 30 300 ppm mA SUPPLY CURRENT Is Ta 25 C 9 12 uA 40 C Ta 125 C 12 15 uA THERMAL HYSTERESIS Vo Hys SO 8 TSSOP 8 50 ppm Specifications subject to change without notice REV B 3 ADR290 ADR291 ADR292 ADR2
14. ZIRIAD R290 Nvv RS ANALOG DEVICES Low Noise Micropower 2 048 V 2 5 V and 4 096 V Precision Voltage References ADR290 ADR291 ADR292 FEATURES Supply Range 2 35 V to 15 V ADR290 2 8 V to 15 V ADR291 4 4 V to 15 V ADR292 Supply Current 12 pA Max Low Noise 6 pV 8 pV 12 pV p p 0 1 Hz 10 Hz High Output Current 5 mA Temperature Range 40 C to 125 C Pin Compatible with REF02 REF19x APPLICATIONS Portable Instrumentation Precision Reference for 3 V and 5 V Systems A D and D A Converter Reference Solar Powered Applications Loop Current Powered Instruments GENERAL DESCRIPTION The ADR290 ADR291 and ADR292 are low noise micro power precision voltage references that use an XFET reference circuit The new XFET architecture offers significant perfor mance improvements over traditional bandgap and Buried Zener based references Improvements include one quarter the voltage noise output of bandgap references operating at the same current very low and ultralinear temperature drift low thermal hysteresis and excellent long term stability The ADR29x family are series voltage references providing stable and accurate output voltages from supplies as low as 2 35 V for the ADR290 Output voltage options are 2 048 V 2 5 V and 4 096 V for the ADR290 ADR291 and ADR292 respectively Quiescent PIN CONFIGURATIONS 8 Lead Narrow Body SO SO Suffix NC NO CONNECT 8 Lead TSSOP RU Suffix ADR29x TOP VIEW
15. above this specification is not implied Exposure to the above maximum rating conditions for extended periods may affect device reliability 2 Remove power before inserting or removing units from their sockets CAUTION ESD electrostatic discharge sensitive device Electrostatic charges as high as 4000 V readily WARNING d accumulate on the human body and test equipment and can discharge without detection Although the ADR290 ADR291 ADR292 features proprietary ESD protection circuitry perma Sp 4 nent damage may occur on devices subjected to high energy electrostatic discharges Therefore ESD SENSITIVE DEVICE proper ESD precautions are recommended to avoid performance degradation or loss of functionality ORDERING GUIDE Temperature Number of Output Initial Coefficient Package Package Parts per Model Voltage Accuracy Max ppm C Description Option Package ADR290 ER ER REEL7 ER REEL 2 048 0 10 8 SOIC SO 8 98 1000 2500 FR FR REEL7 FR REEL 2 048 0 15 15 SOIC SO 8 98 1000 2500 GR GR REEL7 GR REEL 2 048 0 29 25 SOIC SO 8 98 1000 2500 GRU REEL7 GRU REEL 2 048 0 29 25 TSSOP RU 8 1000 2500 ADR291 ER ER REEL7 ER REEL 2 50 0 08 8 SOIC SO 8 98 1000 2500 FR FR REEL7 FR REEL 2 50 0 12 15 SOIC SO 8 98 1000 2500 GR GR REEL7 GR REEL 2 50 0 24 25 SOIC SO 8 98 1000 2500 GRU REEL7 GRU REEL 2 50 0 24 25 TSSOP RU 8 1000 2500 ADR292 ER ER REEL7 ER REEL 4 096 0 07 8 SOIC SO 8
16. alog Devices One Technology Way P O Box 9106 Norwood MA 02062 9106 U S A Tel 781 329 4700 World Wide Web Site http www analog com Fax 781 326 8703 Analog Devices Inc 2001 ADR290 ADR291 ADR292 ADR290 SPECIFICATIONS ELECTRICAL SPEC IFICATIONS V 2 1 V T 25 C unless otherwise noted Parameter Symbol Conditions Min Typ Max Unit E GRADE Output Voltage Vo lour 0 mA 2 046 2 048 2 050 V Initial Accuracy VOERR 2 2 mV 0 10 0 10 F GRADE Output Voltage Vo lour 0 mA 2 045 2 048 2 051 V Initial Accuracy VoERR 3 3 mV 0 15 0 15 G GRADE Output Voltage Vo Iour 0 mA 2 042 2 048 2 054 V Initial Accuracy VOERR 6 6 mV 0 29 0 29 LINE REGULATION E F Grades AVo AVin 2 7 V to 15 V Inu r 0 mA 30 100 ppm V G Grade 40 125 ppm V LOAD REGULATION E F Grades AVo Alioap Vg 5 0 V 0 mA to 5 mA 30 100 ppm mA G Grade 40 125 ppm mA LONG TERM STABILITY AVo After 1000 hrs of Operation 125 C 50 ppm NOISE VOLTAGE en 0 1 Hz to 10 Hz 6 UN p p WIDEBAND NOISE DENSITY en 1 kHz 420 nVA Hz ELECTRICAL SPECIFICATIONS w 2 7 v T 25 C lt T lt 85 C unless otherwise noted Parameter Symbol Conditions Min Typ Max Unit TEMPERATURE COEFFICIENT E Grade TCVo Iour 0 mA 3 8 ppm C F Grade 6 15 ppm C G Grade 10 25 ppm C LINE REGULATION E F Grades AVo AVin 2 7 V to 15
17. ce 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 Low Power Low Voltage Reference For Data Converters side of R1 should be kept as short as possible The ADR29x family has a number of features that makes it ideally suited for use with A D and D A converters The low CHARGER supply voltage required makes it possible to use the ADR290 INPUT and ADR291 with today s converters that run on 3 V supplies without having to add a higher supply voltage for the reference The low quiescent current 12 uA max and low noise tight temperature coefficient combined with the high accuracy of Figure 6 Advantage of Kelvin Connection Vin ADR29x BV the ADR29x makes it ideal for low power applications such LEAD ACID as hand held battery operated equipment BATTERY eg One such ADC for which the ADR291 is well suited is the AD7701 Figure 7 shows the ADR291 used as the reference for L Se this converter The AD7701 is a 16 bit A D converter with on chip digital filtering intended for the measurement of wide 196 dynamic range low frequency signals such as those representing chemical physical or biological processes It contains a charge balancing sigma delta ADC calibration microcontroller with on chip static RAM a c
18. lock oscillator and a serial communica tions port Figure 8 Voltage Regulator for Portable Equipment 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 uW the entire circuit still consumes about 25 mW 5V ANALOG O SUPPLY Vin DVpp Vour SLEEP T 0 1uF ADR291 MODE SND DRDY O DATA READY AD7701 cs O READ TRANSMIT SCLK O SERIAL CLOCK RANGES Us eee BP UP SDATA O SERIAL CLOCK CALIBRATE ANALOG CEKIN INPUT CLKOUT ANALOG GROUND 5V ANALOG O SUPPLY 9 4uF Figure 7 Low Power Low Voltage Supply Reference for the AD7701 14 REV B ADR290 ADR291 ADR292 OUTLINE DIMENSIONS Dimensions shown in inches and mm 8 Lead Narrow Body SO SO Suffix 0 1968 5 00 7 0 1890 pa 8 5 0 1574 4 00 d 0 2440 6 20 0 1497 3 80 TT 4 0 2284 5 80 y _ D GR Mk 0 0500 e d 0 0196 0 50 0500 1 27 BSC FF 6 0095 0 25 4 0 0688 1 75 0 0098 0 25 025 AEP 0 0532 1 35 L 0 0040 0 10 gt la EN gt La 0 0192 0 49 0 0 0500 1 27 SEATING 0 0098 0 25 nihii NE 4 PLANE 0 0138 0 35 0 0075 0 19 0 0160 0 41 Lead TSSOP RU Suffix 0 122 3 10 E 2 90 0 177 4 50 0 169 4 30 0 256 6 50 0 246 6 25 PIN 17 be 0 0256 0 65 BSC 0 0433 0 006 0 15 Li 1 10 D 0 002 0 05 gt e MAX 8
19. lute temperature The general equation is Vour av i orar R3 where AV is the difference in pinch off voltage between the two FETs and Irrar is the positive temperature coefficient correc tion current The various versions of the ADR29x family are created by on chip adjustment of R1 and R3 to achieve 2 048 V 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 drop out voltage EXTRA CHANNEL IMPLANT _ R1 R2 R3 Vour Rr AVp Iprar X R3 Figure 1 ADR290 ADR291 ADR292 Simplified Schematic 2 Device Power Dissipation Considerations The ADR29x 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 output voltage option 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 junc tion temperature that could result in premature device failure The following formula should be used to calculate a device s maxi mum junction temperature or dissipation p 35e 074 In this equation 7 and T are the junction and ambient tem peratures respectively Pp is the device power dissipation and 074 is the device package thermal resistance
20. mplifiers require a finite amount mV of headroom when required to provide any load current The choice for the circuit s negative supply should take this issue into account Vin O ADR29x A1 1 2 OP291 1 2 OP295 Figure 3 A Negative Precision Voltage Reference Uses No Precision Resistors A Precision Current Source Many times in low power applications the need arises for a pre cision current source that can operate on low supply voltages As shown in Figure 4 any one of the devices in the ADR29x family of references can be configured as a precision current source The circuit configuration illustrated is a floating current source with a grounded load The reference s output voltage is bootstrapped across Rsgr which sets the output current into the load With this configuration circuit precision is maintained for load currents in the range from the reference s supply current typically 12 uA to approximately 5 mA REV B Beer Figure 4 A Precision Current Source High Voltage Floating Current Source The circuit of Figure 5 can be used to generate a floating current source with minimal self heating This particular con figuration can operate on high supply voltages determined by the breakdown voltage of the N channel JFET Vs it an Vs E231 SILICONIX 2 10kQ Figure 5 High Voltage Floating Current Source Kelvin Connections In many portable instrumentation applications where P
21. onfigure a current switching DAC into a voltage switching DAC through the use of a 1 25 V reference an op amp and a pair of resistors Using a current switching DAC directly requires the need for an additional operational amplifier at the output to reinvert the signal A negative voltage reference is then desirable from the point that an additional operational amplifier is not required for either reinversion current switching mode or amplification voltage switching mode of the DAC output voltage In general any positive voltage reference can be converted into a negative volt age reference through the use of an operational amplifier and a pair of matched resistors in an inverting configuration The dis advantage to that approach is that the largest single source of error in the circuit is the relative matching of the resistors used The circuit illustrated in Figure 3 avoids the need for tightly matched resistors with the use of an active integrator circuit In this circuit the output of the voltage reference provides the input drive for the integrator The integrator to maintain circuit equilibrium adjusts its output to establish the proper relationship between the reference s Nour and GND Thus any negative output voltage desired can be chosen by simply substituting for the appropriate reference IC One caveat with this approach should be mentioned although rail to rail output amplifiers work best in the application these operational a
22. t REV B 9 ADR290 ADR291 ADR292 1000 50 Vg 5V 900 ADR292 IL 0 mA 800 40 z e x 700 1 gt E 600 Z 30 D 500 w F REISER E Ree gege Q 400 5 20 w 2 300 5 200 10 gt 100 0 0 10 100 1000 0 10 100 1k 10k FREQUENCY Hz FREQUENCY Hz TPC 19 Voltage Noise Density vs Frequency TPC 22 ADR290 Output Impedance vs Frequency 120 Vg EN 100 g S 80 ul S 2 5 R 60 M R w a 40 g o 20 0 ad 10 100 1000 100 FREQUENCY Hz FREQUENCY Hz TPC 20 ADR290 ADR291 ADR292 Ripple Rejection vs TPC 23 ADR291 Output Impedance vs Frequency Frequency 50 Vg EM IL 0 mA 40 S 1 w 2 30 X a a E 20 2 5 o 10 0 0 10 100 1k 10k FREQUENCY Hz TPC 21 ADR290 0 1 Hz to 10 Hz Noise TPC 24 ADR292 Output Impedance vs Frequency 10 REV B ADR290 ADR291 ADR292 TPC 25 ADR291 Load Transient LLL LL ELALLI RIVE EE E TPC 28 ADR291 Turn On Time TPC 26 ADR291 Load Transient TPC 27 ADR291 Load Transient REV B 11 TPC 29 ADR291 Turn Off Time TEMPERATURE FREQUENCY 3 eo N R o IN E Vour DEVIATION ppm z

ANALOG DEVICES ADR290/ADR291/ADR292 Low Noise Micropower 2.048 V 2.5 V 4.096 V Precision Voltage References handbook

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