©
National Instruments Corporation
11
NI SCC-CTR01 User Guide and Specifications
Outputs
The outputs on the NI SCC-CTR01 consist of N-channel MOSFETs that
are connected as low-side switches. A Schottky diode blocks reverse
current flow.
Figure 4 illustrates an NI SCC-CTR01 isolated output.
Figure 4.
Connecting an NI SCC-CTR01 Isolated Output
For the output circuit to function, you must provide 5 to 48 V between V
dd
and V
ss
. Reverse connections of V
dd
and V
ss
do not damage the circuit as
long as these connections do not exceed 60 VDC, as listed in the
section.
If the amount of current the MOSFET conducts exceeds a certain level
(800 mA, typical)—such as when a short occurs in the load—the
MOSFET turns off for 250 ms to protect itself and the load. After this
period of time, the output tries to switch on. If the short still exists, it turns
off for another 250 ms. This process continues until the overcurrent or short
condition is removed, after which switching automatically resumes.
Note
Add bypass capacitor(s) between V
dd
and V
ss
at the load to reduce the chances of
ringing when the output switches on and off, especially when the connecting wires are
longer than 2 m.
V
dd
V
ss
NI SCC-CTR01
Isolator
Load
Out
+
–
Voltage
Regulator
Gate
Control
Current
Sensor
DAQ Device
V
source
