V/3.0 High Precision Reference AD780 +VIN AD780 VOUT
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FEATURES Pin-Programmable Output Ultralow Drift: ppm/ High Accuracy: Noise: Noise Reduction Capability Quiescent Current: Output Trim Capability Plug-In Upgrade Present References Temperature Output Series Shunt Mode Operation
V/3.0 High Precision Reference AD780
+VIN
AD780
VOUT
TRIM
TEMP
PRODUCT DESCRIPTION
AD780 ultrahigh precision bandgap reference voltage which provides output from inputs between initial error temperature drift combined with output noise ability drive value capacitance make AD780 ideal choice enhancing performance high resolution ADCs DACs general purpose precision reference application. unique headroom design facilitates output from input, providing boost dynamic range ADC, over performance with existing references. AD780 used source sink used series shunt mode, thus allowing positive negative output voltages without external components. This makes suitable virtually high performance reference application. Unlike some competing references, AD780 "region possible instability." part stable under load conditions when bypass capacitor used supply. temperature output provided AD780. This provides output voltage that varies linearly with temperature, allowing AD780 configured temperature transducer while providing stable output. AD780 pin-compatible performance upgrade LT1019(A)-2.5 AD680. latter targeted toward power applications. AD780 available grades plastic DIP, SOIC cerdip packages. AD780AN, AD780AR, AD780BN AD780BR specified operation from -40°C +85°C. AD780SQ AD780SQ/883B specified -55°C +125°C operation.
CONNECT
SELECT 2.5V 3.0V
PRODUCT HIGHLIGHTS
AD780 provides pin-programmable output from input. Laser trimming both initial accuracy temperature coefficients results errors over temperature without external components. AD780BN maximum variation from -40°C +85°C. applications requiring even higher accuracy, optional fine-trim connection provided. AD780 noise extremely low, typically from wideband spectral noise density typically nV/Hz. This further reduced desired, simply using external capacitors. temperature output enables AD780 configured temperature transducer while providing stable output reference voltage.
REV.
Information furnished Analog Devices believed accurate reliable. However, responsibility assumed Analog Devices use, infringements patents other rights third parties which result from use. license granted implication otherwise under patent patent rights Analog Devices.
Technology Way, P.O. 9106, Norwood, 02062-9106, U.S.A. Tel: 617/329-4700 Fax: 617/326-8703
AD780-SPECIFICATIONS
unless otherwise noted)
AD780BN/BR Units
AD780AN/AR/SQ Parameter
OUTPUT VOLTAGE OUTPUT VOLTAGE DRIFT1 -40°C +85°C -55°C +125°C LINE REGULATION Output, +VIN TMIN TMAX Output, +VIN TMIN TMAX LOAD REGULATION, SERIES MODE Sourcing IOUT TMIN TMAX Sinking IOUT -40°C +85°C -55°C +125°C LOAD REGULATION, SHUNT MODE ISHUNT QUIESCENT CURRENT, SERIES MODE -40°C +85°C -55°C +125°C MINIMUM SHUNT CURRENT OUTPUT NOISE Spectral Density, LONG TERM STABILITY3 TRIM RANGE TEMPERATURE Voltage Output 25°C Temperature Sensitivity Output Resistance SHORT CIRCUIT CURRENT GROUND TEMPERATURE RANGE Specified Performance Operating Performance Specified Performance Operating Performance
2.495 2.995
2.505 3.005
2.499 2.999
2.501 3.001
Volts Volts ppm/°C ppm/°C
0.75 +125 +125 +125
µV/V µV/V µV/mA µV/mA µV/mA µV/mA µV/mA µV/mA nV/Hz ppm/1000
mV/°C
NOTES Maximum output voltage drift guaranteed packages. mode typically adds quiescent current. Also, increases µA/V above input voltage long term stability specification noncumulative. drift subsequent 1000 periods significantly lower than first 1000 period. operating temperature range defined temperature extremes which device will still function. Parts deviate from their specified performance outside their specified temperature range. *Same AD780AN/AR/SQ specification. Specifications subject change without notice.
CAUTION (electrostatic discharge) sensitive device. Electrostatic charges high 4000 readily accumulate human body test equipment discharge without detection. Although AD780 features proprietary protection circuitry, permanent damage occur devices subjected high energy electrostatic discharges. Therefore, proper precautions recommended avoid performance degradation loss functionality.
WARNING!
SENSITIVE DEVICE
REV.
AD780
ABSOLUTE MAXIMUM RATINGS* ORDERING GUIDE Initial Temperature Temperature Error Coefficient Range
ppm/°C ppm/°C ppm/°C ppm/°C ppm/°C ppm/°C -40°C +85°C -40°C +85°C -40°C +85°C -40°C +85°C -55°C +125°C -55°C +125°C
Ground Trim Ground Temp Ground Power Dissipation (25°C) Storage Temperature -65°C +150°C Lead Temperature (Soldering, sec) 300°C Output Protection: Output safe indefinite short ground momentary short VIN. Classification Class (1000
*Stresses above those listed under "Absolute Maximum Ratings" cause permanent damage device. This stress rating only functional operation device these conditions above those indicated operational specification implied. Exposure absolute maximum specifications extended periods affect device reliability.
Model
AD780AN AD780AR AD780BN AD780BR AD780SQ AD780SQ/883B
Package
Plastic SOIC Plastic SOIC Cerdip Cerdip
THEORY OPERATION
CONFIGURATION 8-Pin Plastic DIP, SOIC Cerdip Packages
Bandgap references high performance solution supply voltage power voltage reference applications. this technique voltage with positive temperature coefficient combined with negative coefficient transistor's produce constant bandgap voltage. AD780, bandgap cell contains transistors which differ emitter area difference their Vbe's produces PTAT current This turn produces PTAT voltage across which when combined with produces voltage that does vary with temperature. Precision laser trimming resistors other patented circuit techniques used further enhance drift performance.
+VIN
TEMP
CONNECT
2.5/3.0V SELECT GND) VOUT TRIM
AD780
VIEW (Not Scale)
LAYOUT
AD780
VOUT
TRIM
TEMP
SELECT 2.5V 3.0V
NOTES Both VOUT pads should connected output Thickness: standard thickness Analog Devices Bipolar dice mils mils. Dimensions: dimensions given have tolerance mils. Backing: standard backside surface silicon (not plated). Analog Devices does recommend gold-backed dice most applications. Edges: diamond used separate wafers into dice thus providing perpendicular edges half-way through die. contrast scribed dice, this technique provides more uniform shape size. perpendicular edges facilitate handling (such tweezer pick-up) while uniform shape size simplifies substrate design attach. Surface: standard surface covered layer glassivation. areas covered except bonding pads scribe lines. Surface Metalization: metalization Analog Devices bipolar dice aluminum. Minimum thickness Bonding Pads: bonding pads have minimum size mils mils passivation windows have mils mils minimum size.
CONNECT
Figure Schematic Diagram
output voltage AD780 determined configuration resistors R13, amplifier's feedback loop. This sets output either depending whether (Pin grounded connected. unique feature AD780 headroom design high gain amplifier which produces precision output from input voltage from input). amplifier design also allows part work with VOUT when current forced into output terminal. This allows AD780 work terminal shunt regulator providing -2.5 -3.0 reference voltage output without external components.
REV.
AD780
PTAT voltage also used provide user with thermometer output voltage which increases rate approximately mV/°C. AD780's resistor which used solely production test purposes. Users currently using LT1019 self-heater (Pin must take into account different load heater supply.
APPLYING AD780
COMPENSATION CAP,
AD780 used without external components achieve specified performance. power supplied grounded, provides output depending whether left unconnected grounded. bypass capacitor (VIN GND) should used load capacitance application expected greater than AD780 mode typically draws This increases µA/V
LOAD CAPACITOR,
Figure Compensation Load Capacitor Combinations
+VIN
VOUT
also improve settling performance AD780 when subjected load transients. improvement noise performance shown Figures following.
AMPLIFIER GAIN
RNULL
AMPLIFIER
AD780
TRIM TEMP SELECT 2.5V 3.0V
100µV
POT.
20µV
10ms
CONNECT
Figure Optional Fine Trim Circuit
10Hz
10Hz 10kHz
Initial error nulled using single potentiometer connected between VOUT, Trim GND. This coarse trim with adjustment range only included here compatibility purposes with other references. fine trim implemented inserting large value resistor (e.g. series with wiper potentiometer. Figure above. trim range, expressed fraction output, simply greater than equal k/RNULL either mode. external null resistor affects overall temperature coefficient factor equal percentage VOUT nulled. example (.03%) shift output caused trim circuit, with ppm/°C null resistor will less than 0.06 ppm/°C output drift (0.03% ppm/°C, since resistors internal AD780 also have temperature coefficients less than ppm/°C).
NOISE PERFORMANCE
Figure Stand-Alone Noise Performance
+VIN
VOUT
AD780
TRIM TEMP SELECT 2.5V 3.0V
CONNECT
Figure Noise Reduction Circuit
impressive noise performance AD780 further improved desired addition capacitors: load capacitor between output ground, compensation capacitor between TEMP ground. Suitable values shown Figure
REV.
AD780
NOISE COMPARISON
wideband noise performance AD780 also expressed ppm. typical performance with without external capacitors ppm. This performance respectively specified performance LT1019.
AMPLIFIER
voltage VTEMP 25°C, temperature coefficient approximately mV/°C. Figure following shows typical VTEMP characteristic curve over temperature.
4.25 4.00 3.75 CIRCUIT CALIBRATED 25°C
lower than
VOLTAGE VOUT
20µV
10ms
3.50 3.25 10mV 3.00 2.75 2.50
2.25 2.00
10Hz 10kHz
TEMPERATURE
Figure Reduced Noise Performance with
TEMPERATURE PERFORMANCE
Figure Temperature Transfer Characteristic
AD780 provides superior performance over temperature means combination patented circuit design techniques, precision thin film resistors drift trimming. Temperature performance specified terms ppm/°C, because nonlinearity temperature characteristic, Box-Test method used test specify part. nonlinearity takes form characteristic S-shaped curve shown Figure Box-Test method forms rectangular around this curve, enclosing maximum minimum output voltages over specified temperature range. specified drift equal slope diagonal this box.
Since TEMP voltage acquired from bandgap core circuit, current pulled from this will have effect VOUT. Care must taken buffer TEMP output with suitable amp, e.g., OP07, AD820 AD711 (all which would result less than change VOUT). relationship between ITEMP VOUT follows: VOUT mV/µA ITEMP (2.5 range) VOUT mV/µA ITEMP (3.0 range)
TEMPERATURE TRANSDUCER CIRCUIT
circuit shown Figure temperature transducer which amplifies TEMP output voltage gain little over provide wider full scale output range. trimpot used adjust output varies exactly mV/°C. minimize resistance changes with temperature, resistors with temperature coefficients, such metal film resistors should used.
ERROR
-0.4
TEMP
AD780
-0.8 TEMPERATURE
AD820
10mV/°C
1.27k (1%) 6.04k (1%)
Figure Typical AD780BN Temperature Drift
TEMPERATURE OUTPUT
AD780 provides "TEMP" output (Pin that varies linearly with temperature. This output used monitor changes system ambient temperature initiate calibration system desired.
Figure Differential Temperature Transducer
REV.
AD780
SUPPLY CURRENT OVER TEMPERATURE
+VIN
AD780's quiescent current will vary slightly over temperature input supply range. test limit over industrial over military temperature range. Typical performance with input voltage temperature variation shown Figure following.
0.85 -55°C
AD780
VOUT
QUIESCENT CURRENT
0.80 25°C
0.75 125°C 0.70
VOUT
Figure 12a. Transient Resistive Load Test Circuit
0.65
0.60 INPUT VOLTAGE Volts
10mA
OUTPUT CHANGE 50mV/DIV
ILOAD
Figure Typical Supply Current over Temperature
TURN-ON TIME
VOUT 0pF)
time required output voltage reach final value within specified error band defined turn-on settling time. major factors that affect this active circuit settling time time thermal gradients chip stabilize. Typical settling performance shown Figure following. AD780 settles within 0.1% final value within
10µs/DIV
Figure 12b. Settling Under Transient Resistive Load
dynamic load resistive capacitive. example load connected long capacitive cable. Figure following shows performance AD780 driving 1000 load.
+VIN
VOUT 2.500V 2.499V 2.498V
10µs/DIV
AD780
VOUT
Figure Turn-On Settling Time Performance
DYNAMIC PERFORMANCE
1000pF
output stage AD780 been designed provide superior static dynamic load regulation. Figure shows performance AD780 while driving load.
VOUT
Figure 13a. Capacitive Load Transient Response Test Circuit
REV.
AD780
10mA OUTPUT CHANGE 50mV/DIV ILOAD VOUT 1000pF)
VOUT
VREF
AD780
VREF 2.5/3.0V SELECT
AD7884
10µs/DIV
Figure 13b. Settling Under Dynamic Capacitive Load
LINE REGULATION
Figure Precision Reference AD7884 16-Bit, High Speed
Line regulation measure change output voltage specified change input voltage. intended simulate worst case unregulated supply conditions measured µV/V. Figure shows typical performance with 15.0
25°C
AD780 also ideal with higher resolution converters such AD7710/AD7711/AD7712. (See Figure 16.) While these parts specified with internal reference, AD780 mode used improve absolute accuracy, temperature stability dynamic range. shown following with optional noise reduction capacitors.
OUTPUT CHANGE
VOUT
REFIN+
-100
AD780
100nF
INPUT VOLTAGE Volts
100µF 2.5/3.0V SELECT
AD7710
-200
REFIN-
Figure Output Voltage Change Input Voltage
PRECISION REFERENCE HIGH RESOLUTION DATA CONVERTERS
Figure Precision Reference AD7710 High Resolution, Sigma-Delta
+4.5 REFERENCE FROM SUPPLY
AD780 ideally suited reference most high resolution ADCs. AD780 stable under capacitive load, superior dynamic load performance, output provides converter with maximum dynamic range without requiring additional expensive buffer amplifier. many ADCs that AD780 suited AD7884, 16-bit, high speed sampling ADC. (See Figure 15.) This part previously needed precision reference, resistor divider buffer amplifier this function.
Some high resolution ADCs accommodate reference voltages +4.5 AD780 used provide precision +4.5 reference voltage from supply using circuit shown following Figure This circuit will provide regulated +4.5 output from supply voltage +4.7 high quality tantalum capacitor parallel with ceramic capacitor resistor ensure output impedance around MHz.
REV.
AD780
VSUPPLY
OUTLINE DIMENSIONS
Dimensions shown inches (mm).
0.1µF
2N2907
SOIC Package
AD780
VOUT 10µF 0.1µF
0.198 (5.00) 0.188 (4.75)
2.5k
0.1µF
0.158 (4.00) 0.150 (3.80)
0.01%
0.01%
0.244 (6.200) 0.228 (5.80)
Figure +4.5 Reference from Single Supply
NEGATIVE (-2.5 -3.0 REFERENCE
0.050 (1.27)
0.018 (0.46) 0.014 (0.36)
0.205 (5.20) 0.181 (4.60)
AD780 produce negative output voltage shunt mode, simply connecting input output ground connecting AD780's negative supply bias resistor shown Figure
+VIN VOUT
0.010 (0.25) 0.004 (0.10)
0.069 (1.75) 0.053 (1.35)
0.015 (0.38) 0.007 (0.18)
0.045 (1.15) 0.020 (0.50)
Plastic Mini-DIP Package
0.280 (7.11) 0.240 (6.10)
AD780
TEMP VOUT (V-) NOTE: LOAD CURRENT MINIMUM SHUNT CURRENT CONNECT TRIM SELECT 2.5V 3.0V -2.5 VOUT
0.210 (5.33) 0.160 (4.06) 0.115 (2.93) 0.100 (2.54) 0.430 (10.92) 0.348 (8.84) 0.060 (1.52) 0.015 (0.38) 0.325 (8.25) 0.300 (7.62) 0.195 (4.95) 0.115 (2.93)
0.130 (3.30) SEATING PLANE
0.015 (0.381) 0.008 (0.204)
0.022 (0.558) 0.014 (0.356)
0.070 (1.77) 0.045 (1.15)
Cerdip Package
Figure Negative (-2.5 Shunt Mode Reference
precise -2.5 -3.0 reference capable supplying load implemented with AD780 series mode using bootstrap circuit following.
0.005 (0.13)
0.055 (1.4)
0.310 (7.87) 0.220 (5.59)
0.405 (10.29) 0.200 (5.08)
0.070 (1.78) 0.030 (0.76)
AD780
CONNECT OUTPUT DESIRED
0.320 (8.13) 0.290 (7.37)
0.060 (1.52) 0.015 (0.38) 0.150 (3.81)
OP-07
2N3906
-2.5V 100mA)
0.200 (5.08) 0.125 (3.18)
0.015 (0.38) 0.008 (0.20)
0.023 (0.58) 0.014 (0.36)
0°-15° 0.100 (2.54) SEATING PLANE
1000pF
Figure -2.5 High Load Current Reference
REV.
PRINTED U.S.A.
C1758-24-1/93
OP-90
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