How to set nPM1300 BCHISETDISCHARGEMSB/-LSB

[sillvi]

Hi,

We want to set the PMIC's battery discharge limit via the registers BCHISETDISCHARGEMSB and BCHISETDISCHARGELSB to 1200mA but the nPM1300 PS does not describe how to translate a current to a register setting.

This post that poses the same question:
nPM1300 BCHGISETDISCHARGE - Nordic Q&A - Nordic DevZone - Nordic DevZone

But we don't understand how to do the conversion from that answer. Could you explain how the translation works?

Thank you

/ Silvia

[Michal]

Hello Silvia,

I will check this internally and I will get back to you.

Best regards,

Michal

[Audun]

Hi sillvi ,

the nPM1300 datasheet was changed from originally showing a wider range of discharge limits to now only two limits, high (1000 mA) and low (200 mA). The electrical specification states a typical value of 1470 mA for the high limit, but this can be lower due to device variation. The 1000 mA and 200 mA limits are guaranteed however.

Best regards,

Audun

[sillvi]

Hi Audun,

I'm not quite understanding what you mean. Are you saying the high limit is 1000 mA or 1470 mA?

We have tried setting the limit to 1000 mA by following the settings described in the data sheet and have read the registers back to confirm they were set correctly. We have also used only the zephyr device tree property

 

dischg-limit-microamp = <1000000>;

With both of these methods, we have manage to load the system with 1600 mA.

We are using a battery that can handle maximum 1200 mA so this is way too high.

If we can't get exactly 1200 mA, how can we at least get the guaranteed 1000 mA limit?

Best regards,

Silvia

Edit: 

When I first posted we were working with an nPM1300 with hardware version code 'C' and tracking code '2503AG' and on that one we did manage to set a discharge current limit slightly below 1200 mA. Just now we saw that in the new version of our hardware, we have an nPM1300 with hardware version code 'D' and tracking code '2521AA' instead (the rest of the IC marking is the same as before).

Could the hardware version have something to do with why the discharge current limit setting no longer works?

[Michal]

Hello Silvia,

I will check with Audun or some others from the PMIC team and get back to you.

Best regards,

Michal

[Michal]

Hello again,

Just a quick update. To my knowledge this is going to be updated in a new version of the datasheet, but I am still trying to find out the details.

Best regards,

Michal