Specifications
Remote disable offers a safe way
to shut down a power supply to
respond to some particular operat-
ing condition or to protect system
operators (in response to a cabinet
door being opened unexpectedly
or someone pushing a panic but-
ton, for instance).
Remote inhibit (RI) is an input to
the power supply that disables the
output when the RI terminal is
pulled low (Figure 1). Shorting the
normally open switch turns off the
supply’s output. You could also
use a logic chip with an open col-
lector transistor output instead of
the switch. Figure 1 also shows the
discrete fault indicator (DFI),
which you can use to signal an
operator or other components in
the system whenever the power
supply detects a user-defined fault.
Almost any operating condition
can create a DFI signal. For exam-
ple, to generate a DFI signal when
the load draws excessive current,
enable the over current protection
(OCP) mode, program the unit to
generate a DFI signal when it
enters constant current mode,
then program the maximum cur-
rent the load normally draws. If
the load current exceeds the maxi-
mum, the DFI output goes low,
disables the power supply, and
informs the operator of the over-
current condition (or performs
another user-defined function),
without tying up the system bus or
interrupting the system controller.
You can daisy chain DFI and RI as
shown in Figure 2. If one supply
detects a fault, all supplies in the
system are disabled. Using this
approach, you can chain together
an unlimited number of supplies.
Increase Safety with
Remote Disable Feature
Tip
3
To Micro-
processor
From Micro-
processor
+5 V
RI
Masse
DFI
Com
RI
Com
DFI
RI
RI
Com
DFI
RI
Power Supply
# 1
Power Supply
# 2
Figure 1. Remote inhibit and discrete
fault indicator schematic.
Figure 2. Daisy-chained DFI and RI.
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