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

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

20

510

0

25

CURRENT – mA

SIMULTANEOUS

SIMULTANEOUS

CROSSLOAD

30

Figure 15. Isolated Power Supplies vs. Load

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

50

1

0

75

LOAD – mA

30

25

0

234567

Figure 16a. Isolated Supply Ripple vs. Load

(External 4.7

µF 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.

1V

10mV

0.1µF

100mV

1mV

CAPACITANCE

1µF

10µF

100µF

(

)

(

)

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.

15

30

29

+15V

2

4

14

1

0.001µF

0.002µF

R (k

Ω) =

(

)

112.5

AD542

3

19

18

AD210

R

R

16

17

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 k

Ω

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