8

®

ISO213

system transients. The isolation barrier has been extensively

evaluated under a combination of high temperatures and

high voltage to confirm its performance in this respect.

ISO213 is free from partial discharges at rated voltages.

PARTIAL DISCHARGE TESTING IN PRODUCTION

This test method provides far more qualitative information

about stress withstand levels than did previous stress tests. It

also provides quantitative measurements from which quality

assurance and control measures can be based. Tests similar

to this test have been used by some manufacturers such as

those of high voltage power distribution equipment for some

time. They employed a simple measurement of RF noise to

detect ionization. This method was not quantitative with

regard to energy of the discharge and was not sensitive

enough for small components such as isolation amplifiers.

Now, however, manufacturers of HV test equipment have

developed means to measure partial discharge, and VDE, the

German standards group, has adopted use of this method for

the testing of opto-couplers. To accommodate poorly de-

fined transients, the part under test is exposed to a voltage

that is 1.6 times the continuous rated voltage and must

display <5pC partial discharge level in a 100% production

test. Where transients are not present on an applied voltage

and the bulk inception voltage is not exceeded, degradation

will not take place. This is the case where OEM production

testing is performed to satisfy regulatory requirements. The

normal test is to apply a relatively slow ramp to a defined

test voltage. Maintain that voltage for 1 minute and then

ramp to zero. Where this test voltage is less than or equal to

the partial discharge test voltage it can be seen that degrada-

tion will not occur. Hence ISO213 is guaranteed to with-

stand a continuous test voltage for 1 minute at the partial

discharge test voltage.

INSTALLATION AND

OPERATING INSTRUCTIONS

POWER SUPPLY AND SIGNAL CONNECTIONS

As with any mixed analog and digital signal component,

correct decoupling and signal routing precautions must be

used to optimize performance. Figure 1 shows the proper

passed to Com 2 with a 0.1

µF ceramic capacitor and 100µH

inductor as close to the device as possible. Short leads will

minimize lead inductance. A ground plane will also reduce

noise problems. If a low impedance ground plane is not

used, signal common lines, and ACom 2 should be tied

directly to the ground at the supply and Com 2 returned via

a separate trace to the supply ground.

To avoid gain and isolation mode (IMR) errors introduced

by the external circuit, connect grounds as indicated in

Figure 3. Layout practices associated with isolation amplifi-

ers are very important. In particular, the capacitance associ-

ated with the barrier, and series resistance in the signal and

reference leads, must be minimized. Any capacitance across

the barrier will increase AC leakage and, in conjunction with

ground line resistance, may degrade high frequency IMR.

VOLTAGE GAIN MODIFICATIONS

The uncommitted instrumentation amplifier at the input can

be used to provide gain, signal inversion, or current to

voltage conversion. The standard design approach for any

instrumentation amplifier stage can be used, provided that

Also, it should be noted that the current required to drive the

equivalent impedance of any feedback network is supplied

by the internal DC/DC converter and must be taken into

account when calculating the loading added to

±V

ISOLATED POWER OUTPUT DRIVE CAPABILITY

On the input side of ISO213, there are two power supplies

capable of delivering 3mA at

±14V typical to power external

circuitry. When using these supplies with external loads, it

is recommended that additional decoupling in the form of

10

µF tantalum bead capacitors, is added to improve the

voltage regulation. Loss of linearity will result if additional

filtering is not used with an output load. Again, power

dissipated in a feedback network must be subtracted from

the available power output at

±V

If ISO213 is to be used in multiple applications, care should

be taken in the design of the power distribution network,

especially when all ISO213s are synchronized. It is best to

use a well decoupled distribution point and to take power

to each ISO213 from this point in a star arrangement as shown

in Figure 4.

FIGURE 3. Technique for Connecting Com 1 and Com 2.

V

ISO

CC

+V

CC

–V

Power

Supply

Load

Circuit

R

ACom 2

Com 2

Com 1

Input

Common

C

INT

C

EXT 2

C

EXT 1

V

OUT

C

and R have a direct effect.

EXT 2

C

has minimal effect on total IMR.

EXT 1

F

B

–

+