STM32l433, Vbat management and LiPo Battery

[emil28]

Hello,

I am using the stm32l433ccu6. I would like to connect my LiPo battery (1 cell) on Vbat. When this battery is full, the voltage is 4.2V. I am very interested in using the Vbat monitoring feature (ADC1_IN18).

But in the Absolute Maximum ratings paragraph, the maximum voltage on Vbat is 4.0V.

For me, this battery management feature is useless if I can't event plug a simple LiPo battery on Vbat and if I need to add components before the Vbat pin to lower the voltage. Is it normal ? Or is it a mistake in the datasheet ?

Thanks.

[RomainR.]

Hi emil28,

For STM32L4 familly, VBAT = 1.55 V to 3.6 V.

VBAT pin is for a backup battery used by the real-time clock and backup Power Domain.

RTC backup batteries are usually non-rechargeable Lithium cells. Their voltage doesn't exceed +3V. CR2032 is an example of such battery.

If your Lipo supply curve reach 4.2V, You need to insert LDO.

BR

[emil28]

Hello,

Thank you for your answer.

It makes sense now.