single switch on off and mode select

You need to think really hard about currents flowing when you don't want them to -- specifically, you want to avoid a parasitic path that'll power up your microprocessor or some chip through an input pin, via the protection diode.

reg'later Vbat PNP .---. VCC o---------------------- --------| |-------o-------o v / '---' | --- | | | === |< .----o----. GND .--| PNP | | | |\ | | | | .-. .-. .-. | | | | | | | | | | | | | | .-. '-' '-' '-' | | | | | | | | | | '-' | o-----|

power my circuit on and off, and also to flip through different modes of operation.

cycling through these two states)

EEVBlog, video blog)

any better suggestions on how to do this?

something like this with an LDO with enable input (not tested!)

LP2981 Vbat .-----. VCC o----------+-------------| |---------------o | | | | .---+EN | o | | '--+--' |- | | o | | === | | GND | | +--|>|----+----| switch input | | | | .-. .-. | | | | | | | | '-' '-' | | === === GND GND

switch turns on regulator, mcu set HOLD to keep it on switch input can see the switch state

maybe add a small cap on enable so the MCU has a bit of time to set the HOLD pin

want to turn off, clear HOLD and wait for ever

-Lasse

hey thanks alot, thats a neat little circuit, but isn't your switch_open always tied low? seems like the micro would always see a low there regardelss of what you do with the switch

thanks!

hey thanks alot, thats a neat little circuit, but isn't your switch_open always tied low? seems like the micro would always see a low there regardelss of what you do with the switch. Should there be a resistor between the switch_open and ground?

thanks!

Yes, it is. It should be connected to the top of that resistor, not the bottom.

I see a microcontroller in there. Does it have a sleep mode with suitable low current draw and a wake on interrupt for an input?