AD210JN Datasheet AD210JN, AD210BN, AD210AN | P7-P9

AD210

REV. A

–6–

Isolated Power: The AD210 provides isolated power at the

input and output ports. This power is useful for various signal

conditioning tasks. Both ports are rated at a nominal ±15 V at

5 mA.

The load characteristics of the isolated power supplies are

shown in Figure 15. For example, when measuring the load

rejection of the input isolated supplies V

ISS

, the load is placed

between +V

ISS

and –V

ISS

. The curves labeled V

ISS

and V

OSS

are

the individual load rejection characteristics of the input and the

output supplies, respectively.

There is also some effect on either isolated supply when loading

the other supply. The curve labeled CROSSLOAD indicates the

sensitivity of either the input or output supplies as a function of

the load on the opposite supply.

5100

CURRENT – mA

VOLTAGE

OSS

ISS

SIMULTANEOUS

CROSSLOAD

Figure 15. Isolated Power Supplies vs. Load

Lastly, the curves labeled V

OSS

simultaneous and V

ISS

simulta-

neous indicate the load characteristics of the isolated power sup-

plies when an equal load is placed on both supplies.

The AD210 provides short circuit protection for its isolated

power supplies. When either the input supplies or the output

supplies are shorted to input common or output common,

respectively, no damage will be incurred, even under continuous

application of the short. However, the AD210 may be damaged

if the input and output supplies are shorted simultaneously.

100

LOAD – mA

RIPPLE – mV p-p

–V

OSS

ISS

OSS

–V

ISS

234567

Figure 16a. Isolated Supply Ripple vs. Load

(External 4.7

F Bypass)

Under any circumstances, care should be taken to ensure that

the power supplies do not accidentally become shorted.

The isolated power supplies exhibit some ripple which varies as

a function of load. Figure 16a shows this relationship. The

AD210 has internal bypass capacitance to reduce the ripple to a

point where performance is not affected, even under full load.

Since the internal circuitry is more sensitive to noise on the

negative supplies, these supplies have been filtered more heavily.

Should a specific application require more bypassing on the iso-

lated power supplies, there is no problem with adding external

capacitors. Figure 16b depicts supply ripple as a function of

external bypass capacitance under full load.

10mV

0.1µF

100mV

1mV

CAPACITANCE

RIPPLE – Peak-Peak Volts

1µF 10µF

100µF

( )

ISS

OSS

( )

–V

ISS

–V

OSS

Figure 16b. Isolated Power Supply Ripple vs. Bypass

Capacitance (Volts p-p, 1 MHz Bandwidth, 5 mA Load)

APPLICATIONS EXAMPLES

Noise Reduction in Data Acquisition Systems: Transformer

coupled isolation amplifiers must have a carrier to pass both ac

and dc signals through their signal transformers. Therefore,

some carrier ripple is inevitably passed through to the isolator

output. As the bandwidth of the isolator is increased more of the

carrier signal will be present at the output. In most cases, the

ripple at the AD210’s output will be insignificant when com-

pared to the measured signal. However, in some applications,

particularly when a fast analog-to-digital converter is used fol-

lowing the isolator, it may be desirable to add filtering; other-

wise ripple may cause inaccurate measurements. Figure 17

shows a circuit that will limit the isolator’s bandwidth, thereby

reducing the carrier ripple.

OUT

OSS

ISS

–V

ISS

+15V

–V

OSS

0.001µF

0.002µF

R (kΩ) =

( )

112.5

(kHz)

AD542

OSS

–V

OSS

SIG

AD210

Figure 17. 2-Pole, Output Filter

Self-Powered Current Source

The output circuit shown in Figure 18 can be used to create a

self-powered output current source using the AD210. The 2 kΩ

resistor converts the voltage output of the AD210 to an equiva-

AD210

REV. A

–7–

lent current V

OUT

/2 kΩ. This resistor directly affects the output

gain temperature coefficient, and must be of suitable stability for

the application. The external low power op amp, powered by

OSS

and –V

OSS,

maintains its summing junction at output

common. All the current flowing through the 2 kΩ resistor flows

through the output Darlington pass devices. A Darlington con-

figuration is used to minimize loss of output current to the base.

OUT

OSS

ISS

–V

ISS

+15V

–V

OSS

LF441

OSS

–V

OSS

SIG

0-10V

AD210

2kΩ

2N3906

(2)

FDH333

OUT

RETURN

Figure 18. Self-Powered Isolated Current Source

The low leakage diode is used to protect the base-emitter junc-

tion against reverse bias voltages. Using –V

OSS

as a current

return allows more than 10 V of compliance. Offset and gain

control may be done at the input of the AD210 or by varying

the 2 kΩ resistor and summing a small correction current

directly into the summing node. A nominal range of 1 mA–

5 mA is recommended since the current output cannot reach

zero due to reverse bias and leakage currents. If the AD210 is

powered from the input potential, this circuit provides a fully

isolated, wide bandwidth current output. This configuration is

limited to 5 mA output current.

Isolated V-to-I Converter

Illustrated in Figure 19, the AD210 is used to convert a 0 V to

+10 V input signal to an isolated 4–20 mA output current. The

AD210 isolates the 0 V to +10 V input signal and provides a

proportional voltage at the isolator’s output. The output circuit

converts the input voltage to a 4–20 mA output current, which

in turn is applied to the loop load R

LOAD

OSS

ISS

–V

ISS

+15V

–V

OSS

1 +V

–V

SIG

AD210

500Ω

2N2907

CURRENT

LOOP

143Ω

3.0k

ADJUST

TO 4mA

WITH 0V IN

+28V

CURRENT

LOOP

2N2219

576Ω

1N4149

SPAN

ADJ

100Ω

AD308

Figure 19. Isolated Voltage-to-Current Loop Converter

Isolated Thermocouple Amplifier

The AD210 application shown in Figure 20 provides amplifica-

tion, isolation and cold-junction compensation for a standard J

type thermocouple. The AD590 temperature sensor accurately

monitors the input terminal (cold-junction). Ambient tempera-

ture changes from 0°C to +40°C sensed by the AD590, are can-

celled out at the cold junction. Total circuit gain equals 183;

100 and 1.83, from A1 and the AD210 respectively. Calibration

is performed by replacing the thermocouple junction with plain

thermocouple wire and a millivolt source set at 0.0000 V (0°C)

and adjusting R

for E

OUT

equal to 0.000 V. Set the millivolt

source to +0.02185 V (400°C) and adjust R

for V

OUT

equal to

+4.000 V. This application circuit will produce a nonlinearized

output of about +10 mV/°C for a 0°C to +400°C range.

OSS

ISS

–V

ISS

+15V

–V

OSS

AD210

13.7k

10k

–V

ISS

10k

220pF

100k

THERMAL

CONTACT

52.3Ω

COLD

JUNCTION

–V

ISS

-20k-

"J"

1000pF

OUT

AD590

AD OP-07

Figure 20. Isolated Thermocouple Amplifier

Precision Floating Programmable Reference

The AD210, when combined with a digital-to-analog converter,

can be used to create a fully floating voltage output. Figure 21

shows one possible implementation.

The digital inputs of the AD7541 are TTL or CMOS compat-

ible. Both the AD7541 and AD581 voltage reference are pow-

ered by the isolated power supply + V

ISS

. I

COM

should be tied to

input digital common to provide a digital ground reference for

the inputs.

The AD7541 is a current output DAC and, as such, requires an

external output amplifier. The uncommitted input amplifier

internal to the AD210 may be used for this purpose. For best

results, its input offset voltage must be trimmed as shown.

The output voltage of the AD210 will go from 0 V to –10 V for

digital inputs of 0 and full scale, respectively. However, since

the output port is truly isolated, V

OUT

and O

COM

may be freely

interchanged to get 0 V to +10 V.

This circuit provides a precision 0 V–10 V programmable refer-

ence with a ±3500 V common-mode range.

OSS

ISS

–V

ISS

+15V

–V

OSS

AD210

200Ω

1kΩ

ISS

OUT

0 - –10V

100kΩ

50kΩ

12-BIT

DIGITAL

INPUT

AD7541

2kΩGAIN

HP5082-2811

OR EQUIVALENT

ISS

AD581

OFFSET

30 29

Figure 21. Precision Floating Programmable Reference

AD210

REV. A

–8–

MULTICHANNEL DATA ACQUISITION FRONT-END

Illustrated in Figure 22 is a four-channel data acquisition front-

end used to condition and isolate several common input signals

found in various process applications. In this application, each

AD210 will provide complete isolation from input to output as

well as channel to channel. By using an isolator per channel,

maximum protection and rejection of unwanted signals is

obtained. The three-port design allows the AD210 to be

configured as an input or output isolator. In this application the

isolators are configured as input devices with the power port

providing additional protection from possible power source

faults.

Channel 1: The AD210 is used to convert a 4–20 mA current

loop input signal into a 0 V–10 V input. The 25 Ω shunt resistor

converts the 4-20 mA current into a +100 mV to +500 mV signal.

The signal is offset by –100 mV via R

to produce a 0 mV to

+400 mV input. This signal is amplified by a gain of 25 to produce

the desired 0 V to +10 V output. With an open circuit, the AD210

will show –2.5 V at the output.

Channel 2: In this channel, the AD210 is used to condition and

isolate a current output temperature transducer, Model AD590. At

+25°C, the AD590 produces a nominal current of 298.2 µA. This

level of current will change at a rate of 1 µA/°C. At –17.8°C (0°F),

the AD590 current will be reduced by 42.8 µA to +255.4 µA. The

AD580 reference circuit provides an equal but opposite current,

resulting in a zero net current flow, producing a 0 V output from

the AD210. At +100°C (+212°F), the AD590 current output will

be 373.2 µA minus the 255.4 µA offsetting current from the

AD580 circuit to yield a +117.8 µA input current. This current is

converted to a voltage via R

and R

to produce an output of

+2.12 V. Channel 2 will produce an output of +10 mV/°F over a

0°F to +212°F span.

Channel 3: Channel 3 is a low level input channel configured with

a high gain amplifier used to condition millivolt signals. With the

AD210’s input set to unity and the input amplifier set for a gain of

1000, a ±10 mV input will produce a ±10 V at the AD210’s out

put.

Channel 4: Channel 4 illustrates one possible configuration for

conditioning a bridge circuit. The AD584 produces a +10 V

excitation voltage, while A1 inverts the voltage, producing negative

excitation. A2 provides a gain of 1000 V/V to amplify the low level

bridge signal. Additional gain can be obtained by reconfiguration

of the AD210’s input amplifier. ±V

ISS

provides the complete power

for this circuit, eliminating the need for a separate isolated excita-

tion source.

Each channel is individually addressed by the multiplexer’s chan-

nel select. Additional filtering or signal conditioning should follow

the multiplexer, prior to an analog-to-digital conversion stage

OSS

ISS

–V

ISS

–V

OSS

AD210

50k

COM

TO A/D

OSS

ISS

–V

ISS

–V

OSS

OFFSET

50k

ISS

–V

ISS

OSS

–V

OSS

AD210

OSS

–V

OSS

AD210

1kΩ

200kΩ

8.25k

AD210

10T

4-20mA 25Ω

50k

1kΩ

10T

15.8k

10T

50k

100Ω

AD590

AD580

–V

ISS

1kΩ

10T

9.31k

AD OP-07

ISS

–V

ISS

–V

ISS

0.47µF

50kΩ

50Ω

1.0µF

39k

20k

ISS

–V

ISS

–V

ISS

AD584

ISS

COM

+15V

DC POWER

SOURCE

AD7502

MULTIPLEXER

–V

CHANNEL

SELECT

CHANNEL 3

CHANNEL 1

CHANNEL 2

CHANNEL 4

+10V

A1 A2 = AD547

Figure 22. Multichannel Data Acquisition Front-End

C1005–9–9/86

PRINTED IN U.S.A.

P1-P3 P4-P6 P7-P9

AD210JN

Mfr. #:

Buy AD210JN

Manufacturer:

Analog Devices Inc.

Description:

Isolation Amplifiers 120 kHz Bandwidth Iso AMP IC

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AD210JN

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