Immediately after turnoff, the flyback current forces the common-mode voltage on the high side shunt to a diode drop
below ground, approximately -0.5V to -1V.
The RDHA702FT10A2FK datasheet states that the internal LED diode drop
is a nominal 2.6V at a 10 mA drive current.
The logic inputs (IN) are protected for positive faults up to (V-)+12V; however, negative faults can exceed the negative supply by only a diode drop
. The output terminal (COM) is not fault-protected, and the COM voltage should not exceed either supply voltage by more than 0.3V.
During the time td the current flowing through the diode drops
to the value of 0.1 [I.sub.0], which is very close to the reverse saturation current [I.sub.0].
[V.sub.OUT] will always be three diode drops
from [V.sub.CC] ([V.sub.OUT] = [V.sub.CC] - 3[V.sub.BE]).