I've designed a PCB that should contain as few components as possible but it should have a simple way for measuring the battery voltage using an ADC channel and a simple voltage divider. My current design with 100k-220k division:
Consumes around 12µA, which is still a bit much for my project constraints.
I'd like to use resistances with 10x that value so around 1MOhm-2MOhm. The readings don't have to be accurate, I just want to have a rough estimate of the LiPo voltage to know when it is empty. I guess if there's too little current drawn over the voltage divider, the noise will be a problem for the ADC.
Is there a best practice for my application or some reference on estimating the noise caused by such high resistances?
EDIT: I am using an ATMEGA1284p AVR MCU, which has an input impedance of 100MOhm