ADLINK cPCI-7434 - Manual (Page 34)

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Operation Theory
4.2 Isolated Digital Output Channels
The common ground connection of isolated digital output is shown figure 13,
while common power connection of isolated digital output as figure 14.
When the isolated digital output goes “ON”, the sink current will be
conducted through the transistors. When the isolated digital output goes
“OFF”, no current is conducted flow through the transistors. Please note that
when the load is of an “inductance nature” such as a relay, coil or motor, the
VDD pin must be connected to an external power source. The extra
connection is utilized for the ‘fly-wheel diode’ to form a current-release
closed loop, so that the transistors are protected from any high reverse
voltage which can be generated by the inductance load when the output is
switched from “ON” to “OFF”.
DD
V
Load
5~35V
-
IGND
VDD n
+
V5V
DC-DC
Convertor
Figure 13: Common Ground Connection for cPCI-7434R and cPCI-7432R
D D
V Load
5~35V
-
IGND
VDD n
+
V5V
DC-DC
Convertor
Figure 14: Common Power Connection for cPCI-7434R/P and cPCI-
7432R/P