Specifications

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Increase safety with
remote disable feature
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Remote disable offers a safe way to
shut down a power supply to respond
to some particular operating condition
or to protect system operators (in
response to a cabinet door being
opened unexpectedly or someone
pushing a panic button, 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 collector transistor output
instead of the switch. Figure 1 also
shows a discrete fault indicator (DFI)
that you can use to signal an operator
or other components in the system
when the power supply detects a
user-defined fault.
Almost any operating condition can
create a DFI signal. For example, 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
current the load normally draws.
If the load current exceeds the
maximum, 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.
Figure 1. Remote inhibit and discrete fault
indicator schematic
Figure 2. Daisy-chained DFI and RI
To micro-
processor
+5 V
RI
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DFI
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From micro-
processor
RI
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DFI
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RI
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DFI
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Power supply
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Power supply
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