Hello,
In my system I'm using one Li-Ion battery and there is no possibility to add another battery to the system. So just one Li-Ion.
I was planning to use the Li-Ion battery until a voltage of around 3.0V. Then I would disable the LDO which is used to generate 1.8V for the MCU and the MCU would stop working. From this moment on only the RTC of the MCU shall run until the protection circuit of the battery cuts the battery off at approximately 2.5V. The problem is, that I can't connect the battery directly to VBAT to supply the RTC, because in the datasheet it's written that the voltage at VBAT cannot be higher than 3.6V.
Do you have any suggestion how to get around this problem. I thought of maybe adding a voltage divider, since the current consumption of the VBAT pin is very low at around 300 nA. Or just adding a resistor in series to generate a voltage drop of around 1V or using a diode in series, but at such low currents, the voltage drop over the diode may won't be enough.
Thanks and cheers,
Marco
