Voltage Sensing
The HCPL-7860/HCPL-786J Isolated Modulator can also
be used to isolate signals with amplitudes larger than its
recommended input range with the use of a resistive volt-
age divider at its input. The only restrictions are that the
impedance of the divider be relatively small (less than 1
kꢆ) so that the input resistance (280 kꢆ) and input bias
current (1 ꢄA) do not affect the accuracy of the measure-
ment. An input bypass capacitor is still required, although
the 39 ꢆ series damping resistor is not (the resistance of
the voltage divider provides the same function). The low-
pass filter formed by the divider resistance and the input
bypass capacitor may limit the achievable bandwidth. To
obtain higher bandwidth, the input bypass capacitor (C2)
can be reduced, but it should not be reduced much below
1000 pF to maintain adequate input bypassing of the iso-
lated modulator.
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Data subject to change. Copyright © 2005-2011 Avago Technologies. All rights reserved. Obsoletes 5989-2166EN
AV02-0409EN - March 28, 2011
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