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±10 V Reference AD688 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 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 ri ghts of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 © 2005 Analog Devices, Inc. All rights reserved.

FEATURES

±10 V tracking outputs Kelvin connections Low tracking error: 1.5 mV Low initial error: 2.0 mV Low drift: 1.5 ppm/°C Low noise: 6 μV p-p Flexible output force and sense terminals High impedance ground sense Wide body SOIC and CERDIP packages GENERAL DESCRIPTION The AD688 is a high precision ±10 V tracking reference. Low tracking error, low initial error, and low temperature drift give the AD688 reference absolute ±10 V accuracy performance previously unavailable in monolithic form. The AD688 uses a proprietary ion-implanted buried Zener diode, and laser wafer drift trimming of high stability thin-film resistors to provide outstanding performance. The AD688 includes the basic reference cell and three additional amplifiers. The amplifiers are laser-trimmed for low offset and low drift and maintain the accuracy of the reference. The amplifiers are configured to allow Kelvin connections to the load and/or boosters for driving long lines or high current loads, delivering the full accuracy of the AD688 where it is required in the application circuit. The low initial error allows the AD688 to be used as a system reference in precision measurement applications requiring 12-bit absolute accuracy. In such systems, the AD688 can provide a known voltage for system calibration; the cost of periodic recalibration can therefore be eliminated. Furthermore, the mechanical instability of a trimming potentiometer and the potential for improper calibration can be eliminated by using the AD688 and calibration software. The AD688 is available in commercial version. Specified over the −40 oC to +85oC temperature range, the AD688 is offered in wide body 16-lead SOIC and 16-lead CERDIP packages, FUNCTIONAL BLOCK DIAGRAM RB GAIN ADJ GND SENSE +IN NC VLOW BAL ADJ NC A4 IN –VS +VS –10V OUT FORCE –10V OUT SENSE +10V OUT FORCE +10V OUT SENSEA3 INV HIGH NOISE REDUCTION AD688 7 6 4 3 5 9 10 8 12 11 13 00815-001NC = NO CONNECT Figure 1. PRODUCT HIGHLIGHTS 1. Precision Tracking. The AD688 offers precision tracking ±10 V Kelvin output connections with no external components. Tracking error is less than 1.5 mV and fine- trim is available for applications requiring exact symmetry between the +10 V and −10 V outputs. 2. Accuracy. The AD688 offers 12-bit absolute accuracy without any user adjustments. Optional fine-trim connections are provided for applications requiring higher precision. The fine-trimming does not alter the operating conditions of the Zener or the buffer amplifiers and thus does not increase the temperature drift. 3. Low output noise. Output noise of the AD688 is low— typically 6 μV p-p. A pin is provided for broadband noise filtering using an external capacitor.

Rev. B | Page 2 of 16 TABLE OF CONTENTS

REVISION HISTORY

3/05—Rev. A to Rev. B

Rev. B | Page 3 of 16 SPECIFICATIONS Typical @ 25°C, +10 V output, VS = ±15 V unless otherwise noted.1 Specifications shown in boldface are tested on all production units at final electrical test. Results from those tests are used to calculate outgoing quality levels. All min and max specifications are guaranteed. Table 1. AD688AQ AD688BQ AD688ARWZ Min Typ Max Min Typ Max Min Typ Max Unit OUTPUT VOLTAGE ERROR +10 V, −10 V Outputs −5 +5 −2 +2 −4 +4 mV ±10 V TRACKING ERROR −3 +3 −1.5 +1.5 −1.5 +1.5 mV OUTPUT VOLTAGE DRIFT +10 V, −10 V Outputs 0°C to +70°C (A, B) ±2 –1.5 +1.5 ppm/°C GAIN ADJ AND BAL ADJ2 Trim Range ± 5 ±5 ±5 mV Input Resistance 150 150 150 kΩ LINE REGULATION TMIN to TMAX 3 –200 +200 –200 +200 –200 +200 µV/V LOAD REGULATION TMIN to TMAX +10 V Output, 0<IOUT<10 mA ±50 ±50 ±50 µV/mA −10 V Output, −10<IOUT<0 mA ±50 ±50 ±50 µV/mA SUPPLY CURRENT TMIN to TMAX 9 12 9 12 12 mA Power Dissipation 270 360 270 360 360 mW OUTPUT NOISE (ANY OUTPUT)

0.1 Hz to 10 Hz 6 6 6 µV p-p

Spectral Density, 100 Hz 140 140 140 nV√Hz LONG-TERM STABILITY (@ 25°C) 15 15 15 ppm/1000 hours BUFFER AMPLIFIERS Offset Voltage 100 100 100 µV Offset Voltage Drift 1 1 1 µV/°C Bias Current 20 20 20 nA Open-Loop Gain 110 110 110 dB Output Current A3, A4 −10 +10 −10 +10 −10 +10 mA Common-Mode Rejection (A3, A4) VCM = 1 V p-p 100 100 100 dB Short-Circuit Current 50 50 50 mA TEMPERATURE RANGE Specified Performance A, B Grades −40 +85 −40 +85 −40 +85 °C 1 See for outp ut configuration. Figure 4 2 Gain and balance adjustments guaranteed capable of trimming output voltage error and symmetry error to zero. 3 Test Conditions: +VS = +18 V, −VS = –18 V; +VS = +13.5 V, −VS = −13.5 V.

Rev. B | Page 4 of 16 ABSOLUTE MAXIMUM RATINGS Table 2. Parameter Rating +VS to −VS 36 V Power Dissipation (25°C) Q Package 600 mW Storage Temperature −65°C to +150°C Lead Temperature (Soldering, 10 s) +300°C Package Thermal Resistance Q (θJA/θJC) 120/35°C/W Output Protection: All outputs safe if shorted to ground Stresses above those listed under “ Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability. ESD CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as hi gh 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 degrada- tion or loss of functionality.

Figure 2. Pin Configuration Table 3. Pin Function Descriptions 1 +10 V OUT FORCE +10 V Output with Kelvin Force. Connect to Pin 3. 2 +V S Positive Power Supply. 3 +10 V OUT SENSE +10 V Output with Kelvin Sense. Connect to Pin 1. 4 A3 IN + Input to A3. Connect to VHIGH, Pin 6. 5 GAIN ADJ Reference Gain Adjustment for Calibration. See the Calibration section. 6 V HIGH Unbuffered Reference High Output. Noise Performance and Reduction section. May be left open. 8 V LOW Unbuffered Reference Low Output. 9 GND SENSE +IN Gound with Kelvin Sense. 10 NC No Connection. Leave floating. 11 NC No Connection. Leave floating. 12 BAL ADJ Reference Centering Adjustment for Calibration. See the Calibration section. 13 A4 IN + Input to A4. Connect to VLOW, Pin 8. 14 −10 V OUT SENSE −10 V Output with Kelvin Sense. Connect to Pin 15. 15 −10 V OUT FORCE −10 V Output with Kelvin Force. Connect to Pin 14. 16 −V S Negative Power Supply.

outputs determine the performance grade of the device. Figure 11. Typical AD688AQ Temperature Drift temperature range is shown in Figure 12. Figure 12. Maximum + 10 V or −10 V Output Change accuracy and stable temperature control in a test system. methods and equipment utilized. the forcing loop of the amplifier and sensing the load voltage.

10 V + V

Figure 13. Advantage of Kelvin Connection and A4 are free for other force-sense chores. should be connected to ground.

Rev. B | Page 14 of 16 NOTES

Rev. B | Page 15 of 16 NOTES

Rev. B | Page 16 of 16 NOTES © 2005 Analog Devices, Inc. All ri ghts reserved. Trademarks and registered trademarks are the prop erty of their respective owners. C00815-0-3/05(B)