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REV. C

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AD202/AD204

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

Tel: 781/329-4700 World Wide Web Site: www.analog.com

Fax: 781/326-8703 © Analog Devices, Inc., 2001

Low-Cost, Miniature

Isolation Amplifiers

FUNCTIONAL BLOCK DIAGRAM

RECT

AND

FILTER

OSCILLATOR

DEMOD

MOD

SIGNAL

POWER

5V

+7.5V

–7.5V

25kHz

AD202

IN–

IN+

IN COM

SIG

ISO

OUT

–V

ISO

OUT

5V

15V DC

POWER

RETURN

OUT

FEATURES

Small Size: Four 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 reduce

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

uncommitted op amp on the input stage. They feature a bipolar

±5 V output range, an adjustable gain range of from 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 spacing. 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 appli-

cations 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 filtering,

summing, high-voltage ranges, and current (transimpedance) 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.

Summary of content (12 pages)

PAGE 1
a FEATURES Small Size: Four Channels/lnch Low Power: 35 mW (AD204) High Accuracy: 0.
PAGE 2
AD202/AD204–SPECIFICATIONS (Typical @ 25 C and V = 15 V unless otherwise noted.) S Model AD204J AD204K AD202J AD202K GAIN Range Error vs. Temperature vs. Time vs. Supply Voltage Nonlinearity (G = 1 V/V) 1 Nonlinearity vs. Isolated Supply Load 1 V/V–100 V/V ± 0.5% typ (± 4% max) ± 20 ppm/°C typ (± 45 ppm/°C max) ± 50 ppm/1000 Hours ± 0.01%/V ± 0.05% max ± 0.0015%/mA * * * * ± 0.01%/V ± 0.025% max * * * * * ± 0.01%/V ± 0.05% max * * * * * ± 0.01%/V ± 0.
PAGE 3
AD202/AD204 PIN DESIGNATIONS AD246–SPECIFICATIONS (Typical @ 25°C and VS = 15 V unless otherwise noted.) Model AD246JY AD202/AD204 SIP Package AD246JN l OUTPUT Frequency Voltage Fan-Out 25 kHz Nominal * 15 V p-p Nominal * 32 Max * POWER SUPPLY REQUIREMENTS Input Voltage Supply Current Unloaded Each AD204 Adds Each 1 mA Load on AD204 +VISO or –VISO Adds 15 V ± 5% * 35 mA 2.2 mA * * 0.
PAGE 4
AD202/AD204 the output leads to get signal inversion. Additionally, in multichannel applications, the unbuffered outputs can be multiplexed with one buffer following the mux. This technique minimizes offset errors while reducing power consumption and cost. The output resistance of the isolator is typically 3 kΩ for the AD204 (7 kΩ for AD202) and varies with signal level and temperature, so it should not be loaded (see Figure 2 for the effects of load upon nonlinearity and gain drift).
PAGE 5
AD202/AD204 AD246 Clock Driver. The AD246 is a compact, inexpensive clock driver that can be used to obtain the required clock from a single 15 V supply. Alternatively, the circuit shown in Figure 4 (essentially an AD246) can be used. In either case, one clock circuit can operate at least 32 AD204s at the rated minimum supply voltage of 14.25 V and one additional isolator can be operated for each 40 mV increase in supply voltage up to 15 V.
PAGE 6
AD202/AD204 Adjustments. When gain and zero adjustments are needed, the circuit details will depend on whether adjustments are to be made at the isolator input or output, and (for input adjustments) on the input circuit used. Adjustments are usually best done on the input side, because it is better to null the zero ahead of the gain, and because gain adjustment is most easily done as part of the gain-setting network.
PAGE 7
AD202/AD204 Except at the highest useful gains, the noise seen at the output of the AD202 and AD204 will be almost entirely comprised of carrier ripple at multiples of 25 kHz. The ripple is typically 2 mV p-p near zero output and increases to about 7 mV p-p for outputs of ± 5 V (1 MHz measurement bandwidth). Adding a capacitor across the output will reduce ripple at the expense of bandwidth: for example, 0.05 µF at the output of the AD204 will result in 1.
PAGE 8
AD202/AD204 Using Isolated Power. Both the AD202 and the AD204 provide ±7.5 V power outputs referenced to input common. These may be used to power various accessory circuits which must operate at the input common-mode level; the input zero adjustment pots described above are an example, and several other possible uses are shown in the section titled Application Examples. Operation at Reduced Signal Swing.
PAGE 9
AD202/AD204 CHANNEL 0 HI CHANNEL 1 HI LO RG RF RF in Figure 17. A three-pole active filter is included in the design to get normal-mode rejection of frequencies above a few Hz and to provide enhanced common-mode rejection at 60 Hz. If offset adjustment is needed, it is best done at the trim pins of the OP07 itself; gain adjustment can be done at the feedback resistor. LO Note that the isolated supply current is large enough to mandate the use of 1 µF supply bypass capacitors.
PAGE 10
AD202/AD204 High-Compliance Current Source. In Figure 19, an isolator is used to sense the voltage across current-sensing resistor R to allow direct feedback control of a high-voltage transistor or FET used as a high-compliance current source. Since the isolator has virtually no response to dc common-mode voltage, the closedloop current source has a static output resistance greater than 1014 Ω even for output currents of several mA.
PAGE 11
AD202/AD204 OUTLINE DIMENSIONS Dimensions shown in inches and (mm). AD202/AD204 SIP Package AD202/AD204 DIP Package 0.250 (6.3) TYP 0.260 (6.6) MAX 2.100 (53.3) MAX 0.350 (8.9) MAX 2.08 (52.8) MAX FRONT VIEW 0.15 (3.81) TYP BOTTOM VIEW 1 3 5 2 4 6 31 1 2 3 38 37 36 22 21 20 1.60 (40.6) 0.12 (3.05) NOTE: PIN 31 IS PRESENT ONLY ON AD202 PIN 33 IS PRESENT ONLY ON AD204 NOTE: PIN 20 IS PRESENT ONLY ON AD202 PIN 21 IS PRESENT ONLY ON AD204 AC1508 Mating Socket AC1060 Mating Socket 0.10 (2.
PAGE 12
AD202/AD204–Revision History Location Page Data Sheet changed from REV. B to REV. C. PRINTED IN U.S.A. C00483e–0–4/01(C) Change to SIP Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 –12– REV.