FUNCTIONAL BLOCK DIAGRAM

REV. A

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a

High Precision

10 V Reference

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 617/329-4700

Fax: 617/326-8703

PRODUCT HIGHLIGHTS

1. The AD688 offers precision tracking

±10 V Kelvin output

connections with no external components. Tracking error is

less than 1.5 mV and a fine-trim is available for applications

requiring exact symmetry between the +10 V and –10 V

outputs.

2. 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. Output noise of the AD688 is low – typically 6

µV p-p. A pin

is provided for broadband noise filtering using an external

capacitor.

4. The AD688 is available in versions compliant with MIL-

STD-883. Refer to the Analog Devices Military Products

Databook or current AD688/883B data sheet for detailed

specifications.

AD688*

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

V p-p

Flexible Output Force and Sense Terminals

High Impedance Ground Sense

Machine Insertable DIP Packaging

MIL-STD-883 Compliant Versions Available

PRODUCT 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 at low cost.

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 and 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 three versions. The AD688AQ and

BQ grades are packaged in 16-pin cerdip (0.3") packages and

are specified for operation from –40

°C to +85°C. The AD688SQ

grade is specified for operation from –55

°C to +125°C.

*Covered by Patent Number 4,644,253.