REV. A
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a
High Speed, Precision
Sample-and-Hold Amplifier
AD585
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700 Fax: 617/326-8703
FEATURES
3.0 ms Acquisition Time to 60.01% max
Low Droop Rate: 1.0 mV/ms max
Sample/Hold Offset Step: 3 mV max
Aperture Jitter: 0.5 ns
Extended Temperature Range: –558C to +1258C
Internal Hold Capacitor
Internal Application Resistors
612 V or 615 V Operation
Available in Surface Mount
APPLICATIONS
Data Acquisition Systems
Data Distribution Systems
Analog Delay & Storage
Peak Amplitude Measurements
MIL-STD-883 Compliant Versions Available
PRODUCT DESCRIPTION
The AD585 is a complete monolithic sample-and-hold circuit
consisting of a high performance operational amplifier in series
with an ultralow leakage analog switch and a FET input inte-
grating amplifier. An internal holding capacitor and matched
applications resistors have been provided for high precision and
applications flexibility.
The performance of the AD585 makes it ideal for high speed
10- and 12-bit data acquisition systems, where fast acquisition
time, low sample-to-hold offset, and low droop are critical. The
AD585 can acquire a signal to ±0.01% in 3 µs maximum, and
then hold that signal with a maximum sample-to-hold offset of
3 mV and less than 1 mV/ms droop, using the on-chip hold
capacitor. If lower droop is required, it is possible to add a
larger external hold capacitor.
The high speed analog switch used in the AD585 exhibits
aperture jitter of 0.5 ns, enabling the device to sample full scale
(20 V peak-to-peak) signals at frequencies up to 78 kHz with
12-bit precision.
The AD585 can be used with any user-defined feedback net-
work to provide any desired gain in the sample mode. On-chip
precision thin-film resistors can be used to provide gains of +1,
–1, or +2. Output impedance in the hold mode is sufficiently
low to maintain an accurate output signal even when driving the
dynamic load presented by a successive-approximation A/D
converter. However, the output is protected against damage
from accidental short circuits.
The control signal for the HOLD command can be either active
high or active low. The differential HOLD signal is compatible
with all logic families, if a suitable reference level is provided. An
on-chip TTL reference level is provided for TTL compatibility.
The AD585 is available in three performance grades. The JP
grade is specified for the 0°C to +70°C commercial temperature
range and packaged in a 20-pin PLCC. The AQ grade is speci-
fied for the –25°C to +85°C industrial temperature range and is
packaged in a 14-pin cerdip. The SQ and SE grades are speci-
fied for the –55°C to +125°C military temperature range and
are packaged in a 14-pin cerdip and 20-pin LCC.
PRODUCT HIGHLIGHTS
1. The fast acquisition time (3 µs) and low aperture jitter
(0.5 ns) make it the first choice for very high speed data
acquisition systems.
2. The droop rate is only 1.0 mV/ms so that it may be used in
slower high accuracy systems without the loss of accuracy.
3. The low charge transfer of the analog switch keeps sample-to
hold offset below 3 mV with the on-chip 100 pF hold capaci-
tor, eliminating the trade-off between acquisition time and
S/H offset required with other SHAs.
4. The AD585 has internal pretrimmed application resistors for
applications versatility.
5. The AD585 is complete with an internal hold capacitor for
ease of use. Capacitance can be added externally to reduce
the droop rate when long hold times and high accuracy are
required.
6. The AD585 is recommended for use with 10- and 12-bit
successive-approximation A/D converters such as AD573,
AD574A, AD674A, AD7572 and AD7672.
7. The AD585 is available in versions compliant with MIL-STD-
883. Refer to the Analog Devices Military Products Databook
or current AD585/883B data sheet for detailed specifications.
FUNCTIONAL BLOCK DIAGRAM
DIP LCC/PLCC Package
