RE: nPM1300 HARDWARE

Priyanka — Fri, 24 Apr 2026 09:01:52 GMT

Hi Jermi,

Here are the observations for the schematics:

1. VBUS nominal capacitance recommended is 1uF.

2. VBAT needs to be connected to a 2.2uF bypass capacitor.

3. For the SDA/SCL pins, if they are not used, connect to GND or VDDIO. Else, connect to VDDIO via pull-up resistors.

4. Could you tell me why you have an additional 2.0V here:

5. At the VBUSOUT pin, you need to have a 1uF decoupling capacitor here, even if it's not used.

6. For VINLDO1 & VINLDO2, connect to the supply for switch/LDO and connect to GND if not used.

7. The same for VOUTLDOx . i.e. connect to output capacitor if used, else connect them to ground.

8. Also, this is how the VOUT1 and VOUT2 is connected to the supply:

But I am not sure I see this in your schematic.

[quote user=""]Can this NTC be used to measure the battery level?
[/quote]

I don't think that's possible because NTC is used to measure the temperature. And this cannot reliably tell you how much battery energy is left.

[quote user=""]The GPIO pins of the nPM1300 are not used. Is it necessary to supply power to VDDIO?[/quote]

The GPIO of the nPM is not used, but you do use TWI (I2C) on the main controller and since the TWI pins are on the same bus as the external sensors, the chip does need the VDDIO as the I/O voltage level.

So this VDDIO basically tell the nPM chip what voltage the I2C buses are.

I would suggest you to take a look at the nPM1300 Design Checklist, nPM1300 Hardware Design Guidelines and also the reference circuitry to properly and correctly proceed with the designing.

Regards,

Priyanka