FUNCTIONAL BLOCK DIAGRAM

a

Low Cost, Miniature

Isolation Amplifiers

AD202/AD204

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.

FEATURES

Small Size: 4 Channels/lnch

Low Power: 35 mW (AD204)

High Accuracy:

±0.025% max Nonlinearity (K Grade)

High CMR: 130 dB (Gain = 100 V/V)

Wide Bandwidth: 5 kHz Full-Power (AD204)

High CMV Isolation:

±2000 V pk Continuous (K Grade)

(Signal and Power)

Isolated Power Outputs

Uncommitted Input Amplifier

APPLICATIONS

Multichannel Data Acquisition

Current Shunt Measurements

Motor Controls

Process Signal Isolation

High Voltage Instrumentation Amplifier

GENERAL DESCRIPTION

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

±5 V output range, an adjustable gain range offrom 1 to 100 V/V,

±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-

ing. For applications requiring a low profile, the DIP package

provides a height of just 0.350".

High Accuracy:

With a maximum nonlinearity of

±0.025%

for the AD202K/AD204K (

±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’s 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

±2000 V pk continuous common-mode isola-

tion, while the AD202J/AD204J provide

±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

µA 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

±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

±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.

© 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

MOD

RECT &

FILTER

3

2

1

4

SIGNAL

DEMOD

±5V

F.S.

25kHz

25kHz

POWER

OSCILLATOR

FB

IN–

IN+

IN COM

38

37

31

RETURN

+15V DC

HI

LO

AD202

+7.5V

–7.5V

±5V

FS

6

5