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AV02-2856EN - November 29, 2012

Voltage Sensing

The ACPL-7970 can also be used to isolate signals with

amplitudes larger than its recommended input range

with the use of a resistive voltage divider at its input. The

only restrictions are that the impedance of the divider be

relatively small (less than 1 k

Ω) so that the input resistance

(24 k

Ω) and input bias current (0.3 mA) do not affect the

accuracy of the measurement. An input bypass capacitor

is still required, although the damping resistor is not

(the resistance of the voltage divider provides the same

function). The low-pass filter formed by the divider resis-

tance and the input bypass capacitor may limit the achiev-

able 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 isolated modulator.