NPM1300 does not start with VBUS at very low VBAT (2.6V)

RE: NPM1300 does not start with VBUS at very low VBAT (2.6V)

Kenneth — Mon, 20 Oct 2025 08:37:14 GMT

Thanks for the update. Closing case.

Kenneth

RE: NPM1300 does not start with VBUS at very low VBAT (2.6V)

mirhamza708 — Sat, 18 Oct 2025 14:48:42 GMT

I have attached 2x10uF capacitors at VSYS and 1x1uF at VBUSIN. Discharged the battery completely and then plugged in the USB and now it works. we were only able to do a few tests only because discharging a battery takes time. The VBUSout still dont have a capacitor. We are manufacturing a new board. And we will include all the recomendations.

Thank you kenneth.

RE: NPM1300 does not start with VBUS at very low VBAT (2.6V)

mirhamza708 — Wed, 15 Oct 2025 11:15:45 GMT

I am not sure about the battery cuttoff because the battery embeds the cuttoff circuit, all I know is I see a 2.5V on the battery output. The supplier mentioned that it has a 2.75V cuttoff.

I do not have an EK board for reference. The VSYS fluctuates a lot on multimeter. so I think maybe it is the missings caps causing the problem. I will try to attach some capacitors to the pins. And see the results.

And the VSET1 is 68K already i think the picture quality is not showing the number correctly.

thanks for the reply i will try to get back to you soon.

RE: NPM1300 does not start with VBUS at very low VBAT (2.6V)

Kenneth — Wed, 15 Oct 2025 10:55:48 GMT

Hello,

Comments on the schematic:

VBUS is missing bypass capacitor (1uF)
VSET1 should be 68k for 2V output voltage
VBUSOUT should be 1uF capacitor even if not used
PVDD/VSYS should have 3x10uF capacitors

Questions:

- Does the battery cutoff mean that that the battery protection circuit kicks in and effectively disconnects the battery? In any case, the behavior does not sound right and it could be related to the missing components on VBUS/PVDD etc.

- Do you have nPM1300-EK to be used as a reference for testing this case?

Kenneth