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'[EE] PFET-based current limit circuit?'
2006\05\01@122224 by Jesse Lackey

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Hello all, I'm looking for a simple-as-possible current limit circuit,
to be used for both inrush control as well as short-circuit-protect in a
battery-based power supply.  What I'd like is something along the lines of:

0.1R current sense resistor
PFET
opamp or some other circuitry that controls the gate on the PFET to keep
the voltage drop across the current sense resistor at some adjustable
maximum, i.e., the max current through the PFET.

it sure seems like such a useful little circuit would exist ... I
haven't found it, and analog is not my forte, I suppose I could design
this little thing but I'd rather use something already proven.

Maybe I'm missing something here?

A 500mA max current @ 5V would be fine, and the PFET would not be
throttling (500mA * 5V = 2.5W) continuously.  For the inrush control
case, it would be a second at the most, and for short-circuit-protect
there would be additional circuitry that detects the situation and shuts
everything down.

Any advice appreciated!
Thanks
Jesse

2006\05\02@081104 by Alan B. Pearce

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>Hello all, I'm looking for a simple-as-possible current
>limit circuit, to be used for both inrush control as
>well as short-circuit-protect in a battery-based power
>supply.  What I'd like is something along the lines of:
>
>0.1R current sense resistor

For the rest of it use an LT6100 or LTC6101 (note that one is "LT" and the
other "LTC") to sense the voltage across the resistor.

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