power nucleo 32 from lipo battery

[DPiór.1]

Hi,

I have STM32 NUCLEO-L432KC Nucleo-32, I would like to power it from a li-pol battery. Is it possible?

[Andrew Neil]

The User Manual tells you what the possible power supplies are ...

https://www.st.com/resource/en/user_manual/um1956-stm32-nucleo32-boards-mb1180-stmicroelectronics.pdf#page=17

[DPiór.1]

@Andrew Neil thanks for prompt reply.

According to the documentation, Nucleo can be powered from source which gives 3-3,6V or 4,75-5,25V. The li-pol battery has 3,7-4,2V. What would you suggest to do, to power the Nucleo from the li-po battery?

[Peter BENSCH · Accepted solution]

@DPiór.1 It depends on which part of the NUCLEO-L432KC you want to supply with the LiPO battery:

• only the STM32L432KC without ST-LINK, then
  • connect the LiPO battery to +5V (CN4.4)
• the STM32L432KC including ST-LINK, then you have to tinker a little and connect the battery to U5V (of course without a USB host connected), e.g. to
  • Pin 1 of the USB socket or
  • Pin 1, 2 of U1 (top side, between U2 and USB socket)
  • Anode D1 (top side, close to USB socket)

Please note that with this connection there are no protective measures against deep discharge of the LiPO and you must take care of this yourself.

[DPiór.1]

@Peter BENSCH I only need to power the board without the ST-LINK. Do you mean that I can connect the li-po battery to +5V even thought the documentation says that it's voltage range is 4,75-5,25 V?

Maybe I should provide the full picture:
I will have solar cell connected to AEM10941 (https://www.tindie.com/products/jaspersikken/solar-harvesting-into-li-ion-battery/). The lipo battery will be charged from the AEM10941. The Nucleo will be powered from that lipo battery. 

Can I directly connect the lipo to the +5V and GND of the Nucleo board?

[Andrew Neil]

Take a look at the schematics for the board.

Presumably, the +5V input goes to a regulator - so look at the specs for that regulator ...

PS:

Schematics here: https://www.st.com/en/evaluation-tools/nucleo-l432kc.html#cad-resources

[DPiór.1]

Thank you for forcing me to learn something :)

It looks that +5V goes to LD39050PU33R, which has operating input voltage 1,5-5,5 V. That means that indeed I can power Nucleo from lipo battery via this PIN.

This is great news, because I was afraid that I will need to add some component between lipo and Nucleo.

Last question: is it ok, that the battery will be connected to Nuclea and AEM10941?

[Andrew Neil]

---

@DPiór.1 wrote:

which has operating input voltage 1,5-5,5 V. 

---

More important would be the dropout voltage - ie, can it maintain 3.3V output regulation when the input is only 3.7V.

(that might not matter - so long as the output doesn't drop below the minimum operating voltage of the STM32L432KC, and/or anything else on the board)

PS:

It's 400mV max - so you should be OK:

https://www.st.com/resource/en/datasheet/ld39050.pdf#page=7

[Peter BENSCH]

You have to decide - the NUCLEO doesn't care what is connected to the power supply as long as it is within the appropriate range.

[DPiór.1]

@Peter BENSCH  @Andrew Neil  thank you very much for your help!