ADLINK PCI-7260 - Manual (Page 42)

32 Operation Theorem
Figure 4-3: CPLD with WDTimer Function
4.4 Isolated Digital Input
The PCI-7260 contains 8 opto-isolated digital input channels. The
circuit diagram of the isolated input channel is shown below.
Figure 4-4: Photo Coupler
The digital input is first routed through a photo-coupler (PC3H4),
so that the connection are not polarity sensitive whether using
positive or negative voltage.
In addition, a first order-filter with time constant about 1.5ms is
provided to filter high frequency noise. The normal input voltage
range for high state is 5 to 24V.
The PCI-7260 provides an isolated +5V power for dry contact
input. When the external circuit has no voltage source(e.g. a
switch), users can use the on board +5V to respond the change of