
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
power supply and signal connections. V
CC
should be by-
passed to Com 2 with a 0.1
μ
F ceramic capacitor and 100
μ
H
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
the full scale voltage appearing on F
B
does not exceed
±
10V.
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
SS
.
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
μ
F 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
SS
.
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.
C has minimal effect on total IMR.
F
B
–
+