RTC battery

I have a custom PCB that uses the PCF8523 with a coin cell battery for backup. The PCB runs off of a AA battery. Is it feasible to just run the entire PCB and RTC off of the AA battery? It is sleeping most of the time so I anticipate the RTC will be running off of backup most of the time (I use a TPL5110 to shut down the board).

It seems strange to have 2 batteries.

Looking at the data sheet it looks like you need to have both... but I’m probably reading it wrong.

The data sheet makes it clear that data will not be valid if the chip power is removed, but I don't see anything stating that the backup battery is required.

Remove the backup battery, try it out and let us know what happens.

I’ll try it out. By both being required, I meant it’s unclear if the chip can run off the same power source for both battery backup and normal operation. Thanks!

It is very clear that the battery backup is used to maintain data validity and keep the oscillator running when the main chip power is removed.

There is obviously no point in connecting the two power inputs together.

An AA battery is 1.5 V, a coin cell is 3 V. What electronics are you using that runs off 1.5 V?

AA LiFePO4