How to use the Vbat

[Tivon]

I am using stm32l431cbt6.when I use the Vbat(3.0V) and close the vdd,I Measure the current is 0.4ma.I see datasheet say i = 200na.I wonder if any software configuration is missing

[Uwe Bonnes]

To get to low power you first need ti understand what is needed and then implement it in the software on the chip. Mostly you need ti care that non pin float and then put the CPU in the right deep sleep.

[Tivon]

I se 5V adaptive power supply.A simple calendar application.I need to be able to use RTC when someone removes the 5V adapter.I want to know why the current is much higher than the specification when VDD is disconnected and only VBAT is powered

[waclawek.jan]

Check if you have all VDD and GND pins connected properly (check both for DPS errors and bad solder joints). This includes also all analog pins (VDDA).

JW

PS. Please change your username to a normal nick.

[Tivon]

I confirm that all VDD VSS have been linked. The following is the schematic diagram. At present, when I use VBAT power supply, I find that there is 0.4V in the 5V power supply, which can exclude the peripheral circuit string. I want to know whether there is any need to set in the MCU

[waclawek.jan]

The internal switch between VBAT and VDD should be OFF, if the mcu is in reset (i.e. VDDA is below reset level)

Question is, whether the 0.4V is caused by open switch between VBAT/VDD, or some other parasitic path.

Is VCC-3.3V switched off (i.e. at 0V) together with VCC?

Can you also try to set some of the brownout flags and see if it makes a difference?

JW