Datasheet AD210 Datasheet (Analog Devices)

INPUT

POWER

SUPPLY

19

14

15

16

17

18

V

O

30

29

T2

POWER

POWER

OSCILLATOR

INPUT OUTPUT

MOD

DEMOD

FILTER

1

2

OUTPUT

POWER

SUPPLY

3

4

O

COM

+V

OSS

–V

OSS

AD210

PWR COMPWR

T3

T1

–V

ISS

+V

ISS

I

COM

+IN

–IN

FB

Precision, Wide Bandwidth

a

FEATURES
High CMV Isolation: 2500 V rms Continuous

63500 V Peak Continuous
Small Size: 1.00" 3 2.10" 3 0.350"
Three-Port Isolation: Input, Output, and Power
Low Nonlinearity: 60.012% max
Wide Bandwidth: 20 kHz Full-Power (–3 dB)
Low Gain Drift: 625 ppm/8C max
High CMR: 120 dB (G = 100 V/V)
Isolated Power: 615 V @ 65mA
Uncommitted Input Amplifier

APPLICATIONS
Multichannel Data Acquisition
High Voltage Instrumentation Amplifier
Current Shunt Measurements
Process Signal Isolation

GENERAL DESCRIPTION

The AD210 is the latest member of a new generation of low
cost, high performance isolation amplifiers. This three-port,
wide bandwidth isolation amplifier is manufactured with sur­face-mounted components in an automated assembly process.
The AD210 combines design expertise with state-of-the-art
manufacturing technology to produce an extremely compact
and economical isolator whose performance and abundant user
features far exceed those offered in more expensive devices.

The AD210 provides a complete isolation function with both
signal and power isolation supplied via transformer coupling in­ternal to the module. The AD210’s functionally complete de­sign, powered by a single +15 V supply, eliminates the need for
an external DC/DC converter, unlike optically coupled isolation
devices. The true three-port design structure permits the
AD210 to be applied as an input or output isolator, in single or
multichannel applications. The AD210 will maintain its high
performance under sustained common-mode stress.

Providing high accuracy and complete galvanic isolation, the
AD210 interrupts ground loops and leakage paths, and rejects
common-mode voltage and noise that may other vise degrade
measurement accuracy. In addition, the AD210 provides pro­tection from fault conditions that may cause damage to other
sections of a measurement system.

PRODUCT HIGHLIGHTS

The AD210 is a full-featured isolator providing numerous user
benefits including:

High Common-Mode Performance: The AD210 provides
2500 V rms (Continuous) and ±

*Covered by U.S. Patent No. 4,703,283.

REV. A

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.

3500 V peak (Continuous) common-

3-Port Isolation Amplifier

AD210*

FUNCTIONAL BLOCK DIAGRAM

mode voltage isolation between any two ports. Low input
capacitance of 5 pF results in a 120 dB CMR at a gain of 100,
and a low leakage current (2 µA rms max @ 240 V rms, 60 Hz).

High Accuracy: With maximum nonlinearity of ± 0.012% (B
Grade), gain drift of ±25 ppm/°C max and input offset drift of
(±10 ±30/G) µV/°C, the AD210 assures signal integrity while
providing high level isolation.

Wide Bandwidth: The AD210’s full-power bandwidth of
20 kHz makes it useful for wideband signals. It is also effective
in applications like control loops, where limited bandwidth
could result in instability.

Small Size: The AD210 provides a complete isolation function
in a small DIP package just 1.00" × 2.10" × 0.350". The low
profile DIP package allows application in 0.5" card racks and
assemblies. The pinout is optimized to facilitate board layout
while maintaining isolation spacing between ports.

Three-Port Design: The AD210’s three-port design structure
allows each port (Input, Output, and Power) to remain inde­pendent. This three-port design permits the AD210 to be used
as an input or output isolator. It also provides additional system
protection should a fault occur in the power source.

Isolated Power: ±15 V @ 5 mA is available at the input and
output sections of the isolator. This feature permits the AD210
to excite floating signal conditioners, front-end amplifiers and
remote transducers at the input as well as other circuitry at the
output.

Flexible Input: An uncommitted operational amplifier is pro­vided at the input. This amplifier provides buffering and gain as
required and facilitates many alternative input functions as
required by the user.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] Fax: [phone]

AD210–SPECIFICATIONS

WARNING!

ESD SENSITIVE DEVICE

(typical @ +258C, and VS = +15 V unless otherwise noted)

Model AD210AN AD210BN AD210JN

GAIN

Range 1 V/V – 100 V/V * *
Error ± 2% max ±1% max *
vs. Temperature(0°C to +70°C) +25 ppm/°C max * *

vs. Supply Voltage ±0.002%/V * *
Nonlinearity

INPUT VOLTAGE RATINGS

Linear Differential Range ±10 V * *
Maximum Safe Differential Input ±15 V * *
Max. CMV Input-to-Output *

ac, 60 Hz, Continuous 2500 V rms * 1500 V rms
dc, Continuous ±3500 V peak * ± 2000 V peak

Common-Mode Rejection *

60 Hz, G = 100 V/V *

≤ 500 Ω Impedance Imbalance 120 dB * *

R

S

Leakage Current Input-to-Output *

@ 240 V rms, 60 Hz 2 µA rms max * *

INPUT IMPEDANCE

Differential l0
Common Mode 5 GΩi5pF * *

INPUT BIAS CURRENT

Initial, @ +25°C 30 pA typ (400 pA max) * *
vs. Temperature (0°C to +70°C) 10 nA max * *

INPUT DIFFERENCE CURRENT

Initial, @ +25°C 5 pA typ (200 pA max) * *
vs. Temperature(0°C to + 70°C) 2 nA max * *

INPUT NOISE

Voltage (l kHz) 18 nV/√
Current (1 kHz) 0.01 pA/√Hz **

FREQUENCY RESPONSE

Bandwidth (–3 dB) *

G = 1 V/V 20 kHz * *
G = 100 V/V 15 kHz * *

Settling Time (± 10 mV, 20 V Step) *

G = 1 V/V 150 µs* *
G = 100 V/V 500 µs* *

Slew Rate (G = 1 V/V) 1 V/µs* *

OFFSET VOLTAGE (RTI)

Initial, @ +25°C ±15 ± 45/G) mV max (±5 ±15/G) mV max *
vs. Temperature (0°C to +70°C) (±10 ±30/G) µV/°C* *

(–25°C to +85°C) (±10 ±50/G) µV/°C* *
RATED OUTPUT

Voltage, 2 kΩ Load ± 10 V min * *
Impedance 1 Ω max * *
Ripple (Bandwidth = 100 kHz) 10 mV p-p max * *

ISOLATED POWER OUTPUTS

Voltage, No Load ±15 V * *
Accuracy ±10% * *
Current ±5mA * *
Regulation, No Load to Full Load See Text * *
Ripple See Text * *

POWER SUPPLY

Voltage, Rated Performance +15 V dc ± 5% * *
Voltage, Operating +15 V dc ± 10% * *
Current, Quiescent 50 mA * *
Current, Full Load – Full Signal 80 mA * *

TEMPERATURE RANGE

Rated Performance –25°C to +85°C* *
Operating –40°C to +85°C* *
Storage –40°C to +85°C* *

PACKAGE DIMENSIONS

Inches 1.00 × 2.10 × 0.350 * *
Millimeters 25.4 × 53.3 × 8.9 * *

NOTES
*Specifications same as AD210AN.

1

Nonlinearity is specified as a % deviation from a best straight line..

2

RTI – Referred to Input.

3

A reduced signal swing is recommended when both ±V

loaded, due to supply voltage reduction.

4

See text for detailed information. _

Specifications subject to change without notice.

(–25°C to +85°C) ±50 ppm/°C max * *

1

(–25°C to +85°C) 30 nA max * *

(–25°C to +85°C) 10 nA max * *

(10 Hz to 10 kHz) 4 µV rms * *

2

3

±0.025% max ±0.012% max *

12

Ω **

Hz **

4

and ±V

ISS

supplies are fully

OSS

–2–

OUTLINE DIMENSIONS

Dimensions shown in inches and (mm).

AC1059 MATING SOCKET

AD210 PIN DESIGNATIONS

Pin Designation Function

1 V
2O
3+V
4–V
14 +V
15 –V

O

COM

OSS

OSS

ISS

ISS

Output
Output Common
+Isolated Power @ Output
–Isolated Power @ Output
+Isolated Power @ Input

–Isolated Power @ Input
16 FB Input Feedback
17 –IN –Input
18 I

COM

Input Common
19 +IN +Input
29 Pwr Com Power Common
30 Pwr Power Input

CAUTION

ESD (electrostatic discharge) sensitive device. Elec­trostatic charges as high as 4000 V readily accumu­late on the human body and test equipment and can
discharge without detection. Although the AD210
features proprietary ESD protection circuitry, per­manent damage may occur on devices subjected to
high energy electrostatic discharges. Therefore,
proper ESD precautions are recommended to avoid
performance degradation or loss of functionality.

REV. A

INSIDE THE AD210

19

14

15

16

17

18

30

29

+V

OSS

V

SIG

AD210

+V

ISS

–V

ISS

+15V

2

3

4

–V

OSS

1

V

OUT

= V

SIG

1+

( )

R

F

R

G

R

G

R

F

19

14

15

16

17

18

30

29

+V

OSS

AD210

+V

ISS

–V

ISS

+15V

2

3

4

–V

OSS

1

R

S1

I

S

V

S2

V

S1

R

S2

R

F

V

OUT

V

OUT

= –R

F

V

S1

R

S1

( )

V

S2

R

S2

+

+ IS + ...

19

15

16

17

18

30

29

+V

OSS

AD210

+V

ISS

–V

ISS

+15V

2

3

4

–V

OSS

R

G

HI

V

OUT

V

SIG

14

200Ω

47.5kΩ
5kΩ

100kΩ

50kΩ

LO

GAIN

OFFSET

1

The AD210 basic block diagram is illustrated in Figure 1.
A +15 V supply is connected to the power port, and
±15 V isolated power is supplied to both the input and
output ports via a 50 kHz carrier frequency. The uncom­mitted input amplifier can be used to supply gain or buff­ering of input signals to the AD210. The fullwave
modulator translates the signal to the carrier frequency for
application to transformer T1. The synchronous demodu­lator in the output port reconstructs the input signal. A
20 kHz, three-pole filter is employed to minimize output
noise and ripple. Finally, an output buffer provides a low
impedance output capable of driving a 2 kΩ load.

INPUT OUTPUT

MOD

T2

T1

POWER

POWER

OSCILLATOR

30

PWR COMPWR

DEMOD

FILTER

29

T3

AD210

OUTPUT

POWER

SUPPLY

1

V

O

O

2

COM

+V

3

OSS

4

–V

OSS

+V

–V

I

COM

–IN
+IN

FB

ISS

ISS

16

17
19

18

14

15

INPUT

POWER

SUPPLY

Figure 1. AD210 Block Diagram

USING THE AD210

The AD210 is very simple to apply in a wide range of ap­plications. Powered by a single +15 V power supply, the
AD210 will provide outstanding performance when used
as an input or output isolator, in single and multichannel
configurations.

Input Configurations: The basic unity gain configura­tion for signals up to ±10 V is shown in Figure 2. Addi­tional input amplifier variations are shown in the following
figures. For smaller signal levels Figure 3 shows how to
obtain gain while maintaining a very high input impedance.

16

V

1

OUT

V

OUT

(±10V)

2

V

SIG

±10V

17
19

AD210

18

AD210

Figure 3. Input Configuration for G > 1

Figure 4 shows how to accommodate current inputs or sum cur­rents or voltages. This circuit configuration can also be used for
signals greater than ±10 V. For example, a ±100 V input span
can be handled with R

Figure 4. Summing or Current Input Configuration

Adjustments

When gain and offset adjustments are required, the actual cir­cuit adjustment components will depend on the choice of input
configuration and whether the adjustments are to be made at
the isolator’s input or output. Adjustments on the output side
might be used when potentiometers on the input side would
represent a hazard due to the presence of high common-mode
voltage during adjustment. Offset adjustments are best done at
the input side, as it is better to null the offset ahead of the gain.

Figure 5 shows the input adjustment circuit for use when the in­put amplifier is configured in the noninverting mode. This offset
adjustment circuit injects a small voltage in series with the

= 20 kΩ and RS1 = 200 kΩ.

F

+V

ISS

14

–V

15

ISS

30

Figure 2. Basic Unity Gain Configuration

The high input impedance of the circuits in Figures 2 and
3 can be maintained in an inverting application. Since the
AD210 is a three-port isolator, either the input leads or
the output leads may be interchanged to create the signal
inversion.

REV. A

+15V

29

+V

–V

OSS

OSS

3

4

Figure 5. Adjustments for Noninverting Input

–3–

AD210

180

140

40

10 20 50 60 100 200 500 1k 2k 5k 10k

160

100

120

60

80

FREQUENCY – Hz

R

LO

= 0Ω

R

LO

= 500Ω

R

LO

= 0Ω

R

LO

= 10kΩ

R

LO

= 10kΩ

G = 100
G = 1

CMR – dB

low side of the signal source. This will not work if the source has
another current path to input common or if current flows in the
signal source LO lead. To minimize CMR degradation, keep the
resistor in series with the input LO below a few hundred ohms.

Figure 5 also shows the preferred gain adjustment circuit. The
circuit shows R

of 50 kΩ, and will work for gains of ten or

F

greater. The adjustment becomes less effective at lower gains
(its effect is halved at G = 2) so that the pot will have to be a
larger fraction of the total R

at low gain. At G = 1 (follower)

F

the gain cannot be adjusted downward without compromising
input impedance; it is better to adjust gain at the signal source
or after the output.

Figure 6 shows the input adjustment circuit for use when the
input amplifier is configured in the inverting mode. The offset
adjustment nulls the voltage at the summing node. This is pref­erable to current injection because it is less affected by subse­quent gain adjustment. Gain adjustment is made in the feedback
and will work for gains from 1 V/V to 100 V/V.

GAIN

47.5kΩ

R

S

V

SIG

50kΩ

OFFSET

5kΩ

200Ω

100kΩ

16

17
19

V

OUT

1

AD210

OSS

OSS

2

3

4

18

+V

ISS

14

–V

15

ISS

30

+V

–V

29

0.1"

GRID

CHANNEL OUTPUTS

1

RFR

G

1

2

R

G

2

CHANNEL INPUTS

R

3

POWER

R

F

R

F

G

3

Figure 8. PCB Layout for Multichannel Applications with
Gain

Synchronization: The AD210 is insensitive to the clock of an
adjacent unit, eliminating the need to synchronize the clocks.
However, in rare instances channel to channel pick-up may
occur if input signal wires are bundled together. If this happens,
shielded input cables are recommended.

+15V

Figure 6. Adjustments for Inverting Input

Figure 7 shows how offset adjustments can be made at the out­put, by offsetting the floating output port. In this circuit, ± 15 V
would be supplied by a separate source. The AD210’s output
amplifier is fixed at unity, therefore, output gain must be made
in a subsequent stage.

16

OSS

OSS

1

2

3

4

200Ω

V

OUT

50kΩ

0.1µF

+15V

17
19

AD210

18

+V

ISS

14

–V

15

PCB Layout for Multichannel Applications: The unique
pinout positioning minimizes board space constraints for multi­channel applications. Figure 8 shows the recommended printed
circuit board layout for a noninverting input configuration with
gain.

ISS

30

+15V

Figure 7. Output-Side Offset Adjustment

+V

–V

29

100k

OFFSET

PERFORMANCE CHARACTERISTICS

Common-Mode Rejection: Figure 9 shows the common-

mode rejection of the AD210 versus frequency, gain and input
source resistance. For maximum common-mode rejection of
unwanted signals, keep the input source resistance low and care­fully lay out the input, avoiding excessive stray capacitance at
the input terminals.

–15V

Figure 9. Common-Mode Rejection vs. Frequency

–4–

REV. A

+0.04

+0.03

+0.02

+0.01

0

–0.01

–0.02

–0.03

–0.04

–10 –8 –6 –4 –2 0 +2 +4 +6 +8 +10

OUTPUT VOLTAGE SWING – Volts

+8

+6

+4

+2

0

–2

–4

–6

–8

ERROR – mV

ERROR – %

0.01

0.009

0.008

0.007

0.006

0.005

0.004

0.003

0.002

0.001

0.000

100

90

80

70

60

50

40

30

20

10

0

0 2 4 6 8 10 12 14 16 18 20

TOTAL SIGNAL SWING – Volts

ERROR – % of Signal Swing

ERROR – ppm of Signal Swing

400

200

0

–200

–400

–600

–800

–1000

–1200

–1400

–1600

–25 0 +25 +50 +70 +85

TEMPERATURE – °C

GAIN ERROR – ppm of Span

G = 1

Phase Shift: Figure 10 illustrates the AD210’s low phase shift
and gain versus frequency. The AD210’s phase shift and wide
bandwidth performance make it well suited for applications like
power monitors and controls systems.

AD210

60

40

20

0

–20

GAIN – dB

–40

–60

–80

φG = 1

φG = 100

100 100k10k1k10

FREQUENCY – Hz

0

–20

–40

–60

–80

–100

PHASE SHIFT – Degrees

–120

–140

Figure 10. Phase Shift and Gain vs. Frequency

Input Noise vs. Frequency: Voltage noise referred to the input
is dependent on gain and signal bandwidth. Figure 11 illustrates
the typical input noise in nV/√

Hz of the AD210 for a frequency

range from 10 to 10 kHz.

60

50

Figure 12. Gain Nonlinearity Error vs. Output

40

Hz

√

30

NOISE – nV/

20

10

0

100 10k1k10

FREQUENCY – Hz

Figure 11. Input Noise vs. Frequency

Gain Nonlinearity vs. Output: Gain nonlinearity is defined as the
deviation of the output voltage from the best straight line, and is
specified as % peak-to-peak of output span. The AD210B provides
guaranteed maximum nonlinearity of ±0.012% with an output span of
±10 V. The AD210’s nonlinearity performance is shown in Figure 12.

Gain Nonlinearity vs. Output Swing: The gain nonlinearity
of the AD210 varies as a function of total signal swing. When
the output swing is less than 20 volts, the gain nonlinearity as a
fraction of signal swing improves. The shape of the nonlinearity
remains constant. Figure 13 shows the gain nonlinearity of the
AD210 as a function of total signal swing.

REV. A

Figure 13. Gain Nonlinearity vs. Output Swing

Gain vs. Temperature: Figure 14 illustrates the AD210’s
gain vs. temperature performance. The gain versus temperature
performance illustrated is for an AD210 configured as a unity
gain amplifier.

Figure 14. Gain vs. Temperature

–5–

AD210

V

OUT

15

30

29

+V

OSS

+V

ISS

–V

ISS

+15V

2

4

–V

OSS

14

1

0.001µF

0.002µF

R (kΩ) =

( )

112.5

f

C

(kHz)

AD542

+V

OSS

–V

OSS

3

V

SIG

19

18

AD210

R

R

16

17

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
between +V

and –V

ISS

. The curves labeled V

ISS

, the load is placed

ISS

and V

ISS

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.

30

30

25

VOLTAGE

20

5100

CURRENT – mA

CROSSLOAD

V

OSS

SIMULTANEOUS

V

OSS

V

ISS

SIMULTANEOUS

V

ISS

Figure 15. Isolated Power Supplies vs. Load

Lastly, the curves labeled V

simultaneous and V

OSS

simulta-

ISS

neous indicate the load characteristics of the isolated power sup­plies 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.

30

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 iso­lated 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.

1V

100mV

+V

10mV

RIPPLE – Peak-Peak Volts

1mV

0.1µF

1µF 10µF

100µF

CAPACITANCE

ISS

( )

+V

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 com­pared to the measured signal. However, in some applications,
particularly when a fast analog-to-digital converter is used fol­lowing the isolator, it may be desirable to add filtering; other­wise ripple may cause inaccurate measurements. Figure 17
shows a circuit that will limit the isolator’s bandwidth, thereby
reducing the carrier ripple.

+V

ISS

+V

OSS

–V

ISS

–V

OSS

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-

–6–

REV. A

100

75

50

RIPPLE – mV p-p

25

Under any circumstances, care should be taken to ensure that
the power supplies do not accidentally become shorted.

0

10

Figure 16a. Isolated Supply Ripple vs. Load

µ

F Bypass)

(External 4.7

234567

LOAD – mA

AD210

+V

OSS

+V

ISS

–V

ISS

+15V

2

–V

OSS

3

18

AD210

16

17

4

13.7k

30

29

10k

R

G

5k

A1

19

–V

ISS

10k

220pF

100k

THERMAL
CONTACT

52.3Ω

COLD

JUNCTION

–V

ISS

+V

ISS

1k

-20k-

"J"

15

14

1000pF

1

V

OUT

AD590

AD OP-07

R

G

+V

OSS

+V

ISS

–V

ISS

+15V

–V

OSS

AD210

200Ω

1kΩ

+V

ISS

V

OUT

0 - –10V

100kΩ

50kΩ

17

1

3

2

18

16

12-BIT

DIGITAL

INPUT

AD7541

2kΩGAIN

HP5082-2811

OR EQUIVALENT

+V

ISS

AD581

OFFSET

17

15

4

1

3

2

18

16

4

15

19

14

30 29

lent current V

/2 kΩ. This resistor directly affects the output

OUT

gain temperature coefficient, and must be of suitable stability for
the application. The external low power op amp, powered by
+V

and –V

OSS

maintains its summing junction at output

OSS,

common. All the current flowing through the 2 kΩ resistor flows
through the output Darlington pass devices. A Darlington con­figuration is used to minimize loss of output current to the base.

FDH333

+V

LF441

–V

OSS

OSS

RETURN

V

SIG

0-10V

16

17
19

2kΩ

1

AD210

18

14

+V

ISS

–V

15

ISS

30

29

+15V

2

3

+V

OSS

4

–V

OSS

Figure 18. Self-Powered Isolated Current Source

The low leakage diode is used to protect the base-emitter junc­tion against reverse bias voltages. Using –V

as a current

OSS

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

ADJUST
TO 4mA
WITH 0V IN

16

17

V

SIG

19

18

14

+V

ISS

Figure 19. Isolated Voltage-to-Current Loop Converter

Isolated Thermocouple Amplifier

The AD210 application shown in Figure 20 provides amplifica­tion, isolation and cold-junction compensation for a standard J
type thermocouple. The AD590 temperature sensor accurately

REV. A

15

–V

ISS

30

+15V

AD210

+V

OSS

–V

OSS

29

.

LOAD

3.0k

2N2907

1 +V

AD308

2

3

4

S

–V

S

SPAN
ADJ

500Ω

143Ω

1N4149

CURRENT

2N2219

576Ω
100Ω

CURRENT

R

LOAD

2N3906

I

OUT

I

OUT

+28V

LOOP

LOOP

monitors the input terminal (cold-junction). Ambient tempera­ture changes from 0°C to +40°C sensed by the AD590, are can­celled 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
source to +0.02185 V (400°C) and adjust R

for E

O

equal to 0.000 V. Set the millivolt

OUT

for V

G

OUT

+4.000 V. This application circuit will produce a nonlinearized
output of about +10 mV/°C for a 0°C to +400°C range.

(2)

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 compat­ible. Both the AD7541 and AD581 voltage reference are pow­ered by the isolated power supply + V

ISS

. I

should be tied to

COM

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

may be freely

COM

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.

Figure 21. Precision Floating Programmable Reference

–7–

equal to

AD210

CHANNEL 1

CHANNEL 2

CHANNEL 3

CHANNEL 4

+V

AD584

ISS

E

AD590

IN

+10V

200kΩ

1kΩ

0.47µF

50k

100Ω

50kΩ

1k

8.25k

50k

RG 5k

+V

ISS

AD OP-07

–V

ISS

+V

A2

–V

1M

10T

10T

ISS

ISS

R

O

50k

R

15.8k

OFFSET
50k

16
17
19

18
14

+V

ISS

–V

15

ISS

F

16
17
19

18
14

+V

ISS

–V

15

ISS

16
17
19

18

14

+V

ISS

–V

15

ISS

16
17
19

18

+V

14

ISS

–V

15

ISS

AD210

1

2

+V

30

–V

29

AD210

+V

30

–V

29

OSS

OSS

OSS

OSS

3

4

+V

–V

COM

1

2

3

4

AD7502

MULTIPLEXER

TO A/D

C1005–9–9/86

AD210

1

2

+V

30

–V

29

OSS

OSS

3

4

CHANNEL
SELECT

AD210

1

2

+V

30

–V

29

OSS

OSS

3

4

COM

DC POWER

SOURCE

+15V

10T

RG 1kΩ

4-20mA 25Ω

10T

R

O

1kΩ

–V

ISS

AD580

+V

ISS

A1

–V

ISS

39k

20k

20k

9.31k
+V

ISS

1.0µF

50Ω

20k

20k

A1; A2 = AD547

Figure 22. Multichannel Data Acquisition Front-End

MULTICHANNEL DATA ACQUISITION FRONT-END

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

O

+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
+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

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
for this circuit, eliminating the need for a separate isolated excita­tion source.

Each channel is individually addressed by the multiplexer’s chan­nel select. Additional filtering or signal conditioning should follow
the multiplexer, prior to an analog-to-digital conversion stage

and RG to produce an output of

F

provides the complete power

ISS

put.

PRINTED IN U.S.A.

.

–8–

REV. A