VBAT on STM32U5G9J-DK1

[RandomGaurav]

Hello,

I have got an STM32U5G9J-DK1 and I want to use its VBAT pin which has been connected to the signal VDD_MCU, which is internal to the board, via solder bridge SB29. As far as my understanding of the data sheet goes, the VBAT pin is supposed to be fed with 1.8 V. So, I was thinking to remove the solder bridge and connect an appropriate battery for this operation. Could you suggest me some good batteries that would suffice this requirement?

Thanks in advance.

Regards,

Gaurav.

[MHoll.2]

The Voltage range on VBAT is 3.6V down to 1.65V, The required battery depend's on the current consumed and the time the battery has to last. Normaly I'm using CR2032 or similar battery's.

[RandomGaurav]

The datasheet repeatedly mentions, "The STM32U5x9J-DKx Discovery kits are low-power systems designed for VDD and VDD_MCU at 1.8 V only." Also, at the top of the block diagram on page #8, it clearly says, "1.8 V power supply." So wouldn't there be an issue if I feed VBAT something other than 1.8 V?

[MHoll.2 · Accepted solution]

VBAT is a separeted power domain, that can be powered up to 3.6V indipendend of the other power domains. So yes You can have a CR2035 (3V) on the VBAT pin and 1.8V on VDD / VDD_CPU.

[TDK]

It looks like VBAT and VDD_MCU are tied. Provided more than 1.8 V, or anything at all, would cause something to be backpowered.

Modifying solder bridges and components could make it work. Consult the schematic to see what you'll need to disconnect.

VBAT isn't exposed on a header anywhere.

[RandomGaurav]

Thanks for specifying this

[RandomGaurav]

I was supposing to remove the solder bridge and use it as a power domain separate from that of VDD_MCU.