FUNCTIONAL BLOCK DIAGRAM
REV. A
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a
High Precision
610 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
610 V Tracking Outputs
Kelvin Connections
Low Tracking Error – 1.5 mV
Low Initial Error – 2.0 mV
Low Drift – 1.5 ppm/8C
Low Noise – 6 mV 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.
