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Low Cost, Miniature
Isolation Amplifiers
AD202/AD204
FUNCTIONAL BLOCK DIAGRAM
AD202
SIGNAL
MOD
鹵5V
FS
+7.5V
鈥?.5V
RECT &
FILTER
25kHz
25kHz
POWER
OSCILLATOR
31
+15V DC
32
POWER
DEMOD
鹵5V
F.S.
38
HI
LO
V
OUT
37
IN COM
+V
ISO
OUT
6
鈥揤
ISO
OUT
5
RETURN
ing. For applications requiring a low profile, the DIP package
provides a height of just 0.350".
High Accuracy:
With a maximum nonlinearity of
鹵
0.025%
for the AD202K/AD204K (鹵 0.05% for the AD202J/AD204J)
and low drift over temperature, the AD202 and AD204 provide
high isolation without loss of signal integrity.
Low Power:
Power consumption of 35 mW (AD204) and
75 mW (AD202) over the full signal range makes these isolators
ideal for use in applications with large channel counts or tight
power budgets.
Wide Bandwidth:
The AD204鈥檚 full-power bandwidth of
5 kHz makes it useful for wideband signals. It is also effective in
applications like control loops, where limited bandwidth could
result in instability.
Excellent Common-Mode Performance:
The AD202K/
AD204K provide
鹵
2000 V pk continuous common-mode isola-
tion, while the AD202J/AD204J provide
鹵
1000 V pk continuous
common-mode isolation. All models have a total common-mode
input capacitance of less than 5 pF inclusive of power isolation.
This results in CMR ranging from 130 dB at a gain of 100 dB to
104 dB (minimum at unity gain) and very low leakage current
(2
碌A(chǔ)
maximum).
Flexible Input:
An uncommitted op amp is provided at the
input of all models. This provides buffering and gain as required,
and facilitates many alternative input functions including filter-
ing, summing, high-voltage ranges, and current (transimped-
ance) input.
Isolated Power:
The AD204 can supply isolated power of
鹵
7.5 V at 2 mA. This is sufficient to operate a low-drift input
preamp, provide excitation to a semiconductor strain gage, or to
power any of a wide range of user-supplied ancillary circuits.
The AD202 can supply
鹵
7.5 V at 0.4 mA which is sufficient to
operate adjustment networks or low-power references and op
amps, or to provide an open-input alarm.
The AD202 and AD204 are general purpose, two-port, trans-
former-coupled isolation amplifiers that may be used in a broad
range of applications where input signals must be measured,
processed and/or transmitted without a galvanic connection.
These industry standard isolation amplifiers offer a complete
isolation function, with both signal and power isolation provided
for in a single compact plastic SIP or DIP style package. The
primary distinction between the AD202 and the AD204 is that
the AD202 is powered directly from a +15 V dc supply while
the AD204 is powered by an externally supplied clock, such as
the recommended AD246 Clock Driver.
The AD202 and AD204 provide total galvanic isolation between
the input and output stages of the isolation amplifier through
the use of internal transformer-coupling. The functionally com-
plete AD202 and AD204 eliminate the need for an external,
user-supplied dc/dc converter. This permits the designer to
minimize the necessary circuit overhead and consequently re-
duce the overall design and component costs.
The design of the AD202 and AD204 emphasizes maximum
flexibility and ease of use, including the availability of an un-
committed op amp on the input stage. They feature a bipolar
鹵5
V output range, an adjustable gain range of from 1 to 100 V/V,
鹵
0.025% max nonlinearity (K grade), 130 dB of CMR and the
AD204 consumes a low 35 mW of power.
PRODUCT HIGHLIGHTS
The AD202 and AD204 are full-featured isolators offering
numerous benefits to the user:
Small Size:
The AD202 and AD204 are available in SIP and
DIP form packages. The SIP package is just 0.25" wide, giving
the user a channel density of four channels per inch. The
isolation barrier is positioned to maximize input to output spac-
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
漏 Analog Devices, Inc., 1994
One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A.
Tel: 617/329-4700
Fax: 617/326-8703
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