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 

     

   

[Asbjørn]

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

[KostasH]

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" 

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?

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 

  

  

     

[Asbjørn]

Hello Kostas,

KostasH said:

"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?

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