nPM1300 BUCK2 not regulating to 3.3 V in standalone mode

RE: nPM1300 BUCK2 not regulating to 3.3 V in standalone mode

tarunkt — Thu, 11 Jun 2026 09:54:45 GMT

Additional information from testing:

I am able to communicate with the nPM1300 successfully over I²C.

Using the regulator shell commands, I can query the PMIC and obtain the following:

regulator vget BUCK1
3.300000 V

regulator vget BUCK2
3.300000 V

So there appears to be a discrepancy between the PMIC-reported BUCK2 voltage setting (3.3 V) and the physical voltage measured on the BUCK2 output (3.33 V) when LiPo Battery only connected state.

Then I connected USB to give the VBUS supply when battery connected, immediately the voltage on VBUCK2 changed to 4.2V. Still I could see the I2C communication active.

Current consumption shows: 90-110mA in the USB power-meter

Please let me know any insights.

Thank you

RE: nPM1300 BUCK2 not regulating to 3.3 V in standalone mode

tarunkt — Thu, 11 Jun 2026 09:29:51 GMT

Dear Szabolcs,

Thank you for your response and for clarifying the questions.

Please find the complete schematic attached to this ticket for your review.

https://devzone.nordicsemi.com/support/359762

Kindly review the schematic and let me know if you notice anything that could prevent BUCK2 from starting or regulating correctly?

Thank you for your support.

Regards,

Tarun

RE: nPM1300 BUCK2 not regulating to 3.3 V in standalone mode

Szabolcs — Thu, 11 Jun 2026 08:32:53 GMT

Hi,

This sound like an issue, the nPM should start the Buck automatically with the configuration you stated. Can you please post your schematic?

Regarding your questions:

Yes,
Yes.
I think it shouldn't, but you can try replacing it with a 10K resistor just for debugging purposes. If there is no NTC for the battery, this feature should be disabled in the register, but I think it only affects battery charging, and not the Bucks.
Yes, there is no regulator behind VSYS, it is only a current-limited output.
Yes, see BUCKSTATUS and BUCK2VOUTSTATUS.