National Instruments FP-PWM-520 - Manual (Page 5)

© National Instruments Corp. 5 FP-PWM-520 and cFP-PWM-520
Install a 2 A maximum, fast-acting fuse between the external
power supply and the V
SUP
terminal on each channel. Install
a 1 A maximum, fast-acting fuse suitable for the load at the
V
OUT
terminal. Figure 3 shows fuses where appropriate.
Figure 3. Wiring the [c]FP-PWM-520
Caution M aximum output current for the cFP-PWM-520
is lower than 1 A if the module is operating in the
50–70 °C temperature range. Refer to the
Specifications
section for more information, and select fuses for the V
OUT
terminals accordingly.
Pulse-Width Modulator Output Circuit
The [c]FP-PWM-520 output channels are optically isolated from
the rest of the FieldPoint bank. The channels are sourcing outputs
with short-circuit protection circuitry. Sourcing current means that
the V
OUT
terminal provides a path to a voltage supply. In the ON
state of the output period, a transistor is turned on between V
SUP
and V
OUT
. In the OFF state, this transistor is turned off, allowing
only a small leakage current to flow.
In the ON state, the effective resistance between V
OUT
and V
SUP
is
typically 0.15
Ω. This resistance causes a voltage drop between the
external supply voltage and the output voltage. For example, if the
external supply voltage is 5 V and the output current is 1 A, the
output voltage is 4.85 V:
5 V – (1 A × 0.15 Ω) = 4.85 V
C V
V
SUP
V
OUT
[c]FP-PWM-520
COM
Protected
Sourcing
Output
+
–
Load
5 VDC or
10–30 VDC
External
Power Supply COM
2 A Max
User-Supplied
Fuse
1 A Max
User-Supplied
Fuse