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

[KostasH]

I would like to check if our observation with nPM1300's VBAT node is expected per the IC's design.

As a background, in our application ee use a low-leakage switch to isolate the battery from nPM1300's VBAT node.

1) Once the battery is isolated while VBUS=0V, the IC shuts down VSYS=0V and this is as expected.

2) Next, we apply VBUS=5.0V and the node VSYS settles to ~4.9V at which point our host can communicate

with the nPM1300 over i2C. What we observe at this phase is that node VBAT generates narrow pulses 

~200us in duration at a repetition rate of ~500ms with peak amplitude of ~5V. I term this behavior as "battery pinging".    

3) The node VBAT becomes steady state ~4V once the host has configures the nPM1300 charger with charging parameters and enables charging.

Is the above battery pinging and battery connecting "normal behavior" and makes sense in terms of the nPM1300 design?

Is there a way to change the nPM1300 OTP memory to enable battery connection per default once the part starts up and without host intervention over i2C?

Thanks in advance, 

Kostas   

[mathiaso]

Hi, Kostas.

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

Best regards,
Mathias

[KostasH]

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 

     

   

[mathiaso]

Hi, Kostas.

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

KostasH said:

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) ?

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

[KostasH]

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  

[mathiaso]

KostasH said:

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.

Good to hear that, Kostas.

KostasH said:

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?

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.

[KostasH]

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.  

[mathiaso]

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

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