Battery monitor circuit

Hi all,

I wonder whether anyone can suggest what’s going on here? Probably something obvious, but… I’ve been playing with a design based on the battery monitoring circuit shown on

The idea being to turn off the resistor network necessary for battery voltage sensing, except when it’s actually needed, to reduce current consumption. I think I’ve incorporated the design into my schematic correctly (see attached).

Q7 happily turns on and off under the control of PIN_A. However, the voltage on the gate of Q1 never gets above 0.4V (this with 3.6V on the battery rail). I am deeply confused by this - does anyone have any suggestions? I’m clutching at straws, at the moment.



My guess: check the pinout of your FETs are correct (ie, that D,G,S are on the pins that you think they are). Never trust libraries :wink:

Yeah, I thought I had my level of suspicion turned up high enough, but evidently not! I’ll check again…

For future reference: yep, the D & S pins on the transistor I was using were swapped. Some leg-twiddling and all is good.