Hello,
We use a CR3032 Lithium battery to backup the clock and do intrusion detection during power down of the machine.
We just connected VBat to the battery. UL told us we would need to protect the battery from reverse currents. For this we would need to use a resistor (for current limiting) and a diode with low leakage.
On the other hand, if the MCU would have this circuitry already and would have a batch named “battery protection circuit�?, we could just do as we want and directly connect the battery to the VBat.
Unfortunately we see in some App-Notes a direct connection as we want to do but no documentation of the internals of the VBat. So we cannot argument with the UL.
I searched in some documentation of different manufacturers with the key words battery and RTC and found both ways:
a) Please use the resistor and diode to get the UL approval
b) Please don’t use resistor and diode, these are integrated already
Whom would I ask for this information about the STM32F769NIH6? Does anybody know here in the community – but I would need some official documentation to argue with the UL I guess.
Please help!
Thanks
Uwe
