I have 9 volt battery to get 5 volt using step down converter. I want to enable the step down using a timer IC max input voltage 6 volt. I will use 3.7 v battery for this.
So my question is: Can I join the ground or negative pole of batteries in the same PCB or circuit, I will have problem with signal voltage to enable step down and power off the timer from the MCU 5 volts ????????