I want to use the thermistor inside of a battery pack on the BQ25887 and on a GPIO pin on a microcontroller so that both the microcontroller and the charging IC can monitor the battery voltage. For reference, I'm using the ATMega32U4 with a 5V regulator.
If the charging IC is powered, then I want the thermistor to be used on the BQ25887. If it is not, then I want the thermistor to be used on the microcontroller. I'm trying to think of a way I can use two switches to switch between the charging IC and the MCU. I can't use a Optocoupler since that takes up too much space on my PCB. Here is what I have now, and here are the questions that I have.
- Can NPN transistors be used as High Side switches like this?
- If no current is flowing through the base, will the transistors truly be open? My concern is current backfeeding into either the LDO-5V line or BQ25887.