Hello,
3V3 power comes from 9V standard battery. It's a temperature measurement tool,
shaped as a pistol, with a trigger. So the hardware is always powered down,
when the trigger is pressed the 9-3V3 regulator is kept on by a MSP keepalive signal
to this regulator shutdown pin.
Ok, the problem is we need a low bat check. There's no ADC, the comparator input
is already in use. This level check should draw 5nA top, but preferably be in
shutdown mode and turned on only when the MSP wants to inquire it if everything
is shining with the battery level.
I'm wondering about using a commercial vco to do this. Since this
is far from a new problem, I'd ask if someone could please share his/her thoughts about this?
Thanks in advance,
Xezi.