Switch ONLY when powered off

Hi!

I wonder if there are any curcuits that allow me to only switch when device is powered off.

I select between 2 chips with their 5V pin and I want to prevent to be able to "hot swap". If I would toggle the switch when power on it will stay on the state it was when the system was powered on.

Is there any solution, any chip I could use?

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dougw over 8 years ago in reply to atmn +6

This is a quick example that doesn't need any chips... Q1 and Q3 are P channel FETs like BSS84, Q2 and Q4 are N channel FETs like BSS138. With the switch in the capacitor position, Q2 will turn on Q1 and…
dougw over 8 years ago +2

You could use an DPST switch to select which chip gets power on power-up. The DPST switch state gets latched on power-up by a D-flip-flop. The D-flip-flop clock can be a simple capacitor to the power rail…
Robert Peter Oakes over 8 years ago +1

OK, so a slightly more complicated approach would be to use a very low cost microcontroller (ATTiny or similar), have two power transistors, one for each unit and a button. When you press the button, the…

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RParkerE over 8 years ago

I do not know if there is any switch that will do what you need, but you should look into Hot Swap Controllers.
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atmn over 8 years ago in reply to RParkerE

Thanks, will look into that.

To clearify. The only way to switch to the other chip so to speak is to power off the device, and then toggle a switch and last power on again.

I want it to just "check" upon power on.
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atmn over 8 years ago in reply to RParkerE

Thanks, will look into that.

To clearify. The only way to switch to the other chip so to speak is to power off the device, and then toggle a switch and last power on again.

I want it to just "check" upon power on.
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