Hi everyone, I need some help with monitoring battery supply voltage to the chip. I am supplying the pic (12f683) with a 3.7v 18650 battery. Basically I want to trigger a comparator interrupt when the voltage hits the 2.8v mark, which will then put the pic into low power mode (sleep/nap).

My problem is that as the supply voltage is coming from the same battery that I want to monitor the voltage from, I cant seem to find a way to use comparator or adc. This is because the voltage reference (supply voltage) is dropping at the same rate as the pin that I will be reading from, it doesn't matter if I use a divider or not, I just cant find a way.

Can anyone help with this or is it impossible without a separate/fixed voltage input to the chip?