nPM1300 VBAT is in pinging mode (not DC / steady state) after VBUS reaches valid range

RE: nPM1300 VBAT is in pinging mode (not DC / steady state) after VBUS reaches valid range

mathiaso — Fri, 30 Jan 2026 14:21:30 GMT

You're very welcome, Kostas! Happy to hear that.

Then we'll close this ticket. Have a nice weekend!

RE: nPM1300 VBAT is in pinging mode (not DC / steady state) after VBUS reaches valid range

KostasH — Fri, 30 Jan 2026 04:15:36 GMT

Thank you all at Nordic's technical support team, especially Mathias and Asbjørn for the comprehensive answers to my questions. I will close the ticket since the discussion points have all been addressed.

RE: nPM1300 VBAT is in pinging mode (not DC / steady state) after VBUS reaches valid range

mathiaso — Mon, 26 Jan 2026 13:26:23 GMT

[quote user="KostasH"]Not to worry about the delay in your response, thank you for answering my question and clarifying the condition (battery is loaded both for during charging and discharging) under which the ADC measures the battery voltage.[/quote]

Good to hear that, Kostas.

[quote user="KostasH"]If I understand your comment correctly, the ADC measurement of the NTC's resistance is not automatically done by the charger in which case the application f/w should perform the measurement periodically to ensure that battery charging follows JEITA profile rules?[/quote]

As described in the datasheet's Monitor battery temperature section:
"Battery temperature is measured by the on-chip System Monitor at regular intervals during charging. The latest result is available in registers ADCNTCRESULTMSB and ADCGP0RESULTLSBS."

Unless, if the functionality is explicitly disabled, as described further up in the same section.

RE: nPM1300 VBAT is in pinging mode (not DC / steady state) after VBUS reaches valid range

KostasH — Thu, 22 Jan 2026 14:44:20 GMT

Hello Mathias,

Not to worry about the delay in your response, thank you for answering my question and clarifying the condition (battery is loaded both for during charging and discharging) under which the ADC measures the battery voltage.

If I understand your comment correctly, the ADC measurement of the NTC's resistance is not automatically done by the charger in which case the application f/w should perform the measurement periodically to ensure that battery charging follows JEITA profile rules?

best regards,

Kostas

RE: nPM1300 VBAT is in pinging mode (not DC / steady state) after VBUS reaches valid range

mathiaso — Thu, 22 Jan 2026 11:54:32 GMT

Hi, Kostas.

Apologies for the delayed response, Kostas. Asbjørn is currently out of office.

[quote user="KostasH"]Can you please kindly clarify from the nPM1300 charge management and system monitor standpoint, what the battery voltage ADC measurement looks like on circuit level? Is the battery voltage measured in open-circuit conditions during charging (charging current stops, battery terminals disconnect from VSYS for a short period of time) and also what about during discharging (I can't imagine the battery disconnects to allow the battery to recover from load, but perhaps the disconnection time is super short) ?[/quote]

The ADC measurement of VBAT is not used by the charger. For the charger, there are analog comparators.

To measure VBAT with the ADC, there is no need to disconnect VBAT (note that the NTC resistor measurement is done by the ADC, and the result has influence on the charger with JEITA profile).

Best regards,
Mathias

RE: nPM1300 VBAT is in pinging mode (not DC / steady state) after VBUS reaches valid range

KostasH — Tue, 13 Jan 2026 18:35:40 GMT

Hello Asbjørn,

Your observations are correct. The sawtooth-like fundamental frequency changes from ~4Hz to ~60Hz and the onset of VRECT rising up seems to be triggered in response to load current picking up on VSYS, or by Charger temporarily start/stopping injecting current into the battery. When VRECT drops below 5V the downstream DCDC regulator that feeds VBUS is no longer in regulation mode i.e. its output voltage VBUS simply tracks VRECT. This is caused by the wireless charger source impedance that varies across coupling distance and dynamics in the load that the nPM1300 plus downstream active consumers.

The nPM1304 is not a better choice for our application because of lower max charging current and lack of the two internal LDOs.

Can you please kindly clarify from the nPM1300 charge management and system monitor standpoint, what the battery voltage ADC measurement looks like on circuit level? Is the battery voltage measured in open-circuit conditions during charging (charging current stops, battery terminals disconnect from VSYS for a short period of time) and also what about during discharging (I can't imagine the battery disconnects to allow the battery to recover from load, but perhaps the disconnection time is super short) ?

Thanks and best regards,

Kostas

RE: nPM1300 VBAT is in pinging mode (not DC / steady state) after VBUS reaches valid range

Asbjørn — Tue, 13 Jan 2026 11:11:16 GMT

Hello Kostas,

Here are my observations from the video:

- It seems the VRECT starts this sequence of modulation. At 22-23 seconds of the video all three signals show a voltage drop. Is this when the charging engages? This stage lasts from 12 seconds until saw tooth ripple emerges on - Vrect and Vbat is showing repeatable small drops on the voltage.

- At 34 seconds though, just before the saw tooth on Vrect, there's a really short pulse noticeable on all domains, see the one to the right here and after that the saw tooth start on Vrect. Vbdomains then show

- The saw tooth increases in frequency after a couple of seconds and not visible on Vrect after. The saw tooth is visible on Vbat until 46 seconds where it seems Vrect goes back up towards 6.2V.

- Another cycle of this starts at 1:09.

Q1: Again Vrect drops down to 4.1V from 6.2-6.3V. Is this dop expected from the buck that feeds VBUS?

Q2: What does VBUS look like?

Q3: Is the wireless charger able to deliver enough current to sustain this? Suspect that that VBUS drops as Vrect drops and it's not capable of delivering enough current. That's why there's a 2V drop on Vrect.

Is it possible that the nPM1304 with the option of smaller charge currents could be an alternative for you?

https://docs.nordicsemi.com/bundle/ps_npm1304/page/keyfeatures_html5.html

Best regards

Asbjørn

RE: nPM1300 VBAT is in pinging mode (not DC / steady state) after VBUS reaches valid range

KostasH — Mon, 12 Jan 2026 14:17:07 GMT

devzone.nordicsemi.com/.../Recording-2026_2D00_01_2D00_08-133023.mp4

Hello Asbjørn,

I have attached a movie recording three traces and their time domain characteristics as the nMP1300 enters battery charging likely in trickle charge mode (fw to 20sec to see the temporal modulations).

VRECT in the top trace is the AC/DC rectifier output of the wireless power RX, that feeds a 5V buck regulator that has its output connected to nPM1300 VBUS input.

The ADC measurement and data readout in the application is slow, at a rate of 1/5 seconds, it does not correlate to the rate of voltage modulation that I have seen. My current hypothesis is that is either caused by the buck regulator's switching scheme, or the nPM1300 charging logic especially if the charging algorithm cahrges the battery using a pulsatile current rather than DC.

Your thoughts?

Thanks and best regards,

Kostas

RE: nPM1300 VBAT is in pinging mode (not DC / steady state) after VBUS reaches valid range

Asbjørn — Mon, 12 Jan 2026 11:55:21 GMT

Hello Kostas,

If I may ask what sort of modulation are you observing? Is it the same frequency as you have configured the ADC to measure?

Is it related to TWI frequency? Is it related to wireless charging switching?

How are you observing the modulation? Are you able to share plots from what you observe?

Best regards

Asbjørn

RE: nPM1300 VBAT is in pinging mode (not DC / steady state) after VBUS reaches valid range

KostasH — Sat, 10 Jan 2026 21:42:24 GMT

Hello Asbjørn,

I appreciate your replies to my questions, the details you have provide are very valuable. I have taken note in regards to Q1 and Q2 and will apply changes in our host f/w accordingly.

I hope that you will be able to help answer one more circuit detail specific to the battery charging in the nPM1300. As a background, we feed VBUS from a wireless charging receiver (AC/DC rectifier) and have observed temporal voltage modulation at the supply voltage side i.e. VBUS during stationary battery charging (in this scenario no external consumers are supplied from VSYS, nor DC/DC or LDO 1/2).

I wonder if this voltage modulation on VBUS is caused by the charger itself if the charging current is pulsatile over time, or if charging is interrupted periodically by the nPM1300 to take ADC measurements of VBAT and or IBAT?

Have a good weekend!

best regards,

Kostas

RE: nPM1300 VBAT is in pinging mode (not DC / steady state) after VBUS reaches valid range

Asbjørn — Sat, 10 Jan 2026 20:27:56 GMT

Hello Kostas,

[quote user="KostasH"]

"For the VBAT connection, battery is applied from the VBAT pin and provided to VSYS"

Does this mean that VBAT is always connected to VSYS in the absence of VBUS (VBUS<3.8V) as long as VBAT is higher than VBATPOR=2.75V, and there is no need for the host to enable battery charging in the nPM1300 in order for the battery to connect to VSYS?

[/quote]

You don't need to enable battery charging for VBAT to be connected to VSYS, but VBAT will be disconnected if VBUS is connected and you enable charging.

Q1: There other circumstances where the BCHGCHARGESTATUS is invalid/off. See chapter 6.2.7 of the product specification.

Q2:

If automatic measurements are configured, you will have ADC measurements coming in the selected scenarios.

Best regards

Asbjørn

RE: nPM1300 VBAT is in pinging mode (not DC / steady state) after VBUS reaches valid range

KostasH — Wed, 07 Jan 2026 16:56:55 GMT

Hello Asbjørn,

Thank you for your reply and clarification about the battery detection function in the nPM1300.

Your explanation makes a lot of sense to me know and also explains why we have been seeing the battery detection function to behave differently across different boards that we have built so far. I have checked the IC marking in two different lots that we have built, the package type is the same in both i.e. WLCSP 35 pin BGA:

Lot#1: [NPM1300, CAAAC0, 2405AE]

Lot#2: [NPM1300, CAAAD0, 2519AA]

It appears the the first lot of boards was assembled with the older silicon, the 2nd one with the newer version that has the battery detection function revised/removed. Please confirm if this is your understanding as well.

Can you please clarify one detail, namely where you wrote:

"For the VBAT connection, battery is applied from the VBAT pin and provided to VSYS"

Your explanation is very clear about the start of battery charging that should be conditional to VBUS being connected and reported as such in the VBUSINSTATUS register of system regulator block.

I have two more questions about the charging status(es) that are reported in the two different hardware registers, namely 1) BCHGCHARGESTATUS in the charger block and 2) ADCIBATMEASSTATUS in the system monitor (ADC) block of the IC.

Q1) Is the BCHGCHARGESTATUS register only valid when ADCIBATMEASSTATUS reports that the charger is in Charging mode?

Q2) Is the system monitor generally always active regardless of the charger being enabled or not, are the ADC measurements of VBAT and IBAT accurate in all three possible states namely during a) Battery Discharging, b) Battery Charging and c) VSYS load supplied exclusively from VBUS?

Thanks and Best Regards,

Kostas

RE: nPM1300 VBAT is in pinging mode (not DC / steady state) after VBUS reaches valid range

Asbjørn — Wed, 07 Jan 2026 11:48:40 GMT

Hello Kostas,

About the battery detection. In the latest revision of the silicon the battery detection is disabled since there was some issues with some battery protection circuitry and we decided to disable the whole functionality. We got more issues than the detection was helpful as the detection circuitry triggered batteries to enter shut down mode and manually needed to be unplugged.

What is the part numbers you have now on the nPM1300? The detection functionality will not be there for a larger build quantity, so we recommend avoiding the functionality even if you should have development boards with it available.

For the VBAT connection, battery is applied from the VBAT pin and provided to VSYS. If VBUS is available with a voltage higher than VBATm VSYS will switch and use VBUS as source in order to disconnect VBAT from VSYS and possibly charge VBAT from VSYS (if that's what you want). You don't have to do any configurations for the VSYS source, but you would have to configure what is supposed to happen if VBUS is connected. I.e if you want to activate the charger and charge the battery while VBUS is there.

Best regards

Asbjørn

RE: nPM1300 VBAT is in pinging mode (not DC / steady state) after VBUS reaches valid range

KostasH — Fri, 02 Jan 2026 17:51:36 GMT

Hi Mathias,

Apology for the delay in responding to your reply. Unfortunately, I do not have any recorded traces and I am unable to reproduce the "battery pinging" that I have described in my original post, this might be caused by changes in the MCU f/w that configures and controls the nP1300 in our application.

Can you please shed some light on the battery detection functionality in the nPM1300, if such a function exists in the present silicon that we use in our boards?

I have just discovered that the v1.2 version of the nPM1300 datasheet has removed the battery detection function and status info all together, does this mean that from a certain silicon revision of the IC the battery detection has been removed?

Lastly, I'd appreciate it if you please clarify what the necessary conditions are for a Li-Ion battery to connect to the power distribution path VBAT->VSYS and also the in-built down-stream regulators (LDO and DCDCs). What I mean by that is e.g. does the host MCU need to configure the nPM1300 with charging mode enabled for the battery to connect to the supply inputs and also VSYS?

Thanks and best regards,

Kostas

RE: nPM1300 VBAT is in pinging mode (not DC / steady state) after VBUS reaches valid range

mathiaso — Tue, 16 Dec 2025 15:06:45 GMT

Hi, Kostas.

Do you have any plots showing the behaviour you're describing?

Best regards,
Mathias