ADLINK PCI-8124-C - Manual (Page 28)

18 Signal Connections
3.2 Isolated Input Ports (LTC, INCOM)
There are 4 pairs of isolated input ports on PCI-8124-C. Each pair
has two terminals. One is INCOMx, and the other is LTCx.
Because the input port of the photo coupler utilized on PCI-8124-C
is single-directional, LTC signal must be lower than INCOM signal.
When there is a differential voltage between LTCx and corre-
sponding INCOMx, the photo coupler will turn on immediately.
There is an internal resistor in the PCI-8124-C circuit as figure
shows below. So it is not necessary to attach additional resistor
connected outside the PCI-8124-C. The forward current of input
signal is 7.5mA to 12.5mA. The typical forward voltage is 1.65V,
and the maximum forward voltage is 1.9V. So users should calcu-
late the appropriate voltage applied on LTCx and INCOMx.
CN1 Pin No. Name Description
1 INCOM1 In1 Com
3 INCOM2 In2 Com
30 INCOM3 In3 Com
32 INCOM4 In4 Com
2 LTC1 Isolated Latch 1
4 LTC2 Isolated Latch 2
27 LTC3 Isolated Latch 3
29 LTC4 Isolated Latch 4
INCOMx
LTCx
Outside PCI-8124 inside PCI-8124
Max 30mA 2.2KΩ
7.5mA to 12.5mA