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STM32 Vbat pin setup

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unscripted:
I recently found this setup for the battery pin of the STM32L476 (see attached). It's simplified just to show the connections of Vbat pin. I wonder if this setup right. Shouldn't VBAT pin be connected to 3.3V_bat net instead of directly connected to the battery? The 3.3V_bat net is also used to power some minor backup circuit. I did not find information on the MCU having internal reverse polarity protection. What would happen if one mistakenly connect a battery in reverse and 3.3V is there? It may cause some unwanted behavior in the MCU.

SiliconWizard:
I guess the idea was to not draw current from the coin cell when Vdd is present?
If so, yes, as it is shown it's useless as the 3.3V_bat isn't connected to anything. At least anything shown on this piece of schematic.

But also, if this was the goal, the whole idea itself is useless anyway. The STM32L4 series does not draw any significant current from the VBAT pin when Vdd is present. It only goes in VBAT mode when Vdd does not power the MCU (and even in this case it only draws ~300 nA). So there's nothing external to add.

Now if the goal was actually something else (since we don't see where 3V_bat goes), anything goes.

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