circuit power disabler

Hi,

I have a circuit (analog and digital) that I would like to be able to cut its own power supply for a fixed time, ie. ~3 seconds, so that the circuit can be totally reset, like flipping the power switch manually would do. I have considered using a dedicated micro controlling a high side pfet switch to cut the power, with the micro supply fed from before the pfet, but was wondering if there is a purely analog way to turn the pfet off for a couple seconds, or another simpler way to accomplish this.

cheers, Jamie

Reply to
Jamie Morken
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Monostable multivibrator?

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Sylvia.

Reply to
Sylvia Else

Reset controller chip?

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Good Luck! Rich

Reply to
Rich Grise

You may want to consider a soft start scheme. Some chips are prone to latchup if you switch a power supply at electronic switch "naked" speed. It could be as simple as a resistor in the PFET drive. Maybe a diode so that you turn off fast but turn on slow.

Reply to
miso

On Jan 14, 11:54=A0am, Jamie Morken wrote:

Try something like this. Something I put together in LTspice. May or may not be suitable. As usual , build the thing to actually test it!! Don't rely on spice...

Version 4 SHEET 1 880 680 WIRE -160 -80 -448 -80 WIRE -48 -80 -160 -80 WIRE 32 -80 -48 -80 WIRE 112 -80 32 -80 WIRE 352 -80 208 -80 WIRE -48 -48 -48 -80 WIRE 32 -32 32 -80 WIRE -448 -16 -448 -80 WIRE -112 0 -160 0 WIRE -160 48 -160 0 WIRE -48 64 -48 48 WIRE 32 64 32 32 WIRE 32 64 -48 64 WIRE 128 64 128 -32 WIRE 128 64 32 64 WIRE 128 96 128 64 WIRE -160 160 -160 128 WIRE 352 176 352 -80 WIRE -336 208 -400 208 WIRE -224 208 -256 208 WIRE -448 304 -448 64 WIRE -400 304 -400 288 WIRE -400 304 -448 304 WIRE -160 304 -160 256 WIRE -160 304 -400 304 WIRE 128 304 128 176 WIRE 128 304 -160 304 WIRE 192 304 128 304 WIRE 352 304 352 256 WIRE 352 304 192 304 WIRE 192 320 192 304 FLAG 192 320 0 SYMBOL pmos 208 -32 M270 SYMATTR InstName M1 SYMATTR Value IRF7205 SYMBOL res 336 160 R0 SYMATTR InstName Load SYMATTR Value 10 SYMBOL res 112 80 R0 SYMATTR InstName R2 SYMATTR Value 470k SYMBOL voltage -448 -32 R0 WINDOW 3 24 44 Left 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 12 SYMBOL cap 16 -32 R0 SYMATTR InstName C1 SYMATTR Value 220=B5 SYMBOL pnp -112 48 M180 WINDOW 3 21 -29 Left 0 SYMATTR InstName Q1 SYMATTR Value 2N3906 SYMBOL res -176 -96 R0 SYMATTR InstName R3 SYMATTR Value 1k SYMBOL res -176 32 R0 SYMATTR InstName R4 SYMATTR Value 10k SYMBOL npn -224 160 R0 SYMATTR InstName Q2 SYMATTR Value 2N2222 SYMBOL res -240 192 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R5 SYMATTR Value 1k SYMBOL voltage -400 192 R0 WINDOW 3 -115 138 Left 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value PULSE(0 5 20s 100n 100n 1) TEXT -34 280 Left 0 !.tran 100 TEXT -568 168 Left 0 ;Pulse to turn off power

Cheers. Rob

Reply to
neddie

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