nPM1300 Setup Guidance

RE: nPM1300 Setup Guidance

Johann — Wed, 29 Oct 2025 12:47:40 GMT

Thank you for the reply, Yes the Cap recommendations will be followed this was a snippet out of a larger design as example. so not all net connection are terminated/ shown. wanted to clarify that the buck1 could not be set by default to 3v3 and that all current downstream of the chip was measurable by the fuel gauge

RE: nPM1300 Setup Guidance

mathiaso — Mon, 27 Oct 2025 13:42:07 GMT

[quote user="Rustie0125"]and yes I'm asking if all current is measured by the coulomb counter for accurate reporting[/quote]

It should then be the fuel gauging functionality you're looking for. There's also a page about this in the documentation.

If you want to have a default output voltage on VOUT2 of 3.3V, a resistor in the 250...500kΩ range should be used on the VSET2 pin.

As described in the hardware design guidelines, there should be a 1µF decoupling cap on the VBUS pin.

How is the SHPHLD button connected?

The VBUSOUT pin should have a 1µF decoupling cap.

It might be a good idea to evaluate whether should add a smaller cap in the 10 to 100nF range as well to the VSYS output/PVDD input or not.

In LDO mode, it's recommended to have two 10µF caps in parallel on each of the LDO outputs.

RE: nPM1300 Setup Guidance

Johann — Fri, 24 Oct 2025 14:52:46 GMT

Updated. setup. so MCU can stay powered via Buck 2 and the two load switches turn on and off independently for sensors.

RE: nPM1300 Setup Guidance

Johann — Fri, 24 Oct 2025 13:21:49 GMT

That's the next best option yes, SO will need to setup the MCU on BUCK 2 to make sure 3v3 is correct at startup. and yes I'm asking if all current is measured by the coulomb counter for accurate reporting

RE: nPM1300 Setup Guidance

mathiaso — Thu, 23 Oct 2025 09:21:22 GMT

[quote user="Rustie0125"]So the next approach is to power the MCU and Memory off the buck1 output. and all sensors off the LDO1 and or LDO 2 outputs to allow power savings and rail control. I'm asking if this makes sense an approach,[/quote]

I can't immediately see any problems with this, as long as the voltages are the same.

[quote user="Rustie0125"]secondly if I will be able to still monitor total system current consumption in this setup with the battery column counter when running on battery.[/quote]

I'm sorry, but is it a battery coulomb counter you're referring to?

[quote user="Rustie0125"]if you look at the example provided R23 is used to set the buck1 output voltage on startup. if the voltage level for either buck 1 or buck 2 is set in registers, does these settings remain even after reboot? and if so what is the use/point of external VSEL resistors ?[/quote]

As seen in the answer to this ticket, there's no non-volatile memory on the nPM1300. Thus, the VSET resistors will determine the output voltage at start-up.

[quote user="Rustie0125"]if the settings does not persist across reboots and the external resistors are needed for VSEL does the 150K make sense on BUck1 output as the datasheet shows up to 2.7v and not 3.3 like buck 2. page 47 table 18 and tablet 19 of the datasheet. Long stroy short how do I set VSET1 to 3.3V on boot if the table shows it can only go to 2.7v[/quote]

As you've already seen in the VSET table, BUCK1 may only be set to voltages up to 2.7V at start-up by using the resistors and the BUCK1NORMVOUT register must be written to in order to set it to 3.3V.

Is there a reason why you can't just use BUCK2 instead?

RE: nPM1300 Setup Guidance

Johann — Wed, 22 Oct 2025 13:44:34 GMT

Hi Mathias, Let me clarify as it seems you are not understanding what I'm asking. The net labels are miss leading so let me ask questions differently.

) I know the VBUS and VSYS outputs require the external Capacitors as per reference design. I have those added in this design. My question here was, I assumed VSYS was a regulated voltage ( my case 3v3) and I could power my MCU and memory off this rail permanently. Looking at the graphs the VSYS voltage out that output requires additional regulation hence why they are fed into the Buck inputs to allow regulation. So the next approach is to power the MCU and Memory off the buck1 output. and all sensors off the LDO1 and or LDO 2 outputs to allow power savings and rail control. I'm asking if this makes sense an approach, and secondly if I will be able to still monitor total system current consumption in this setup with the battery column counter when running on battery.
) if you look at the example provided R23 is used to set the buck1 output voltage on startup. if the voltage level for either buck 1 or buck 2 is set in registers, does these settings remain even after reboot? and if so what is the use/point of external VSEL resistors ? if the settings does not persist across reboots and the external resistors are needed for VSEL does the 150K make sense on BUck1 output as the datasheet shows up to 2.7v and not 3.3 like buck 2. page 47 table 18 and tablet 19 of the datasheet. Long stroy short how do I set VSET1 to 3.3V on boot if the table shows it can only go to 2.7v

RE: nPM1300 Setup Guidance

mathiaso — Wed, 22 Oct 2025 11:39:10 GMT

Hi, Johann.

[quote user=""]1) Does this make sense for best shutdown setup and current consumption monitoring ? My initial thought was that the VSYS output would be regulated and the LDO 1 and 2 could be used independently but it does not seem like that's the case.[/quote]

By "VSYS" here, do you mean the VOUT1 output called "3.3V-SYS" in your schematic, or do you mean the VSYS output? The relationship between VSYS and VBUS is shown in these graphs in the datasheet. Do you mean using LDOs 1 and 2 independently from each other, or independently from the rest of the nPM1300? In your schematic, you're powering LDO from the VOUT1 buck output, which again is powered by VSYS through PVDD, as shown in the block diagram.

[quote user=""]2) I know the LDO outputs can be setup via the registers but since the SOC will be powered on boot by LDO1 how do I set the boot up voltage to 3v3? The datasheet notes the max as 2.7V for LDO1 ?[/quote]

The maximum LDO output voltage is 3.3V, as shown in the LDO electrical specification. As seen in the register overview, the LDO output voltages are set in the LDSW1VOUTSEL and LDSW2VOUTSEL registers.

[quote user=""]3) If the above is correct do I just leave VSYS and SYS-VBUS unconnected/used ?[/quote]

The reference circuitry has to be followed even if not connecting VSYS or VBUSOUT to any external circuitry. The configurations can be combined to match your design. E.g., in configuration 3, VBUSOUT isn't used.

Best regards,
Mathias