Hello Shony,

Can you provide your register information when this issue occurs?

Best Regards

Christian.

Hi Christian,

I am using the default power-up registers setting.

Thanks,

Hello Shony,

The registers values include the status registers and this will help me conclude how the device is behaving and help narrow down the issues.

Can you provide all of your register information when this issue occurs?

Best Regards,

Unfortunately i am just in the beginning of my board ramp-up. Can't read the registers yet. Hope that i will be able to do that soon.

B.R

Shony

Hi Christian,

I finally can read the charger status register REG0x21 and I found the following result:

When the battery voltage is ~33.4V and its current is ~80mA, the status register content is not stable - sometimes 04h (Tamper) and sometimes 07H (Termination).

When I check with scope the STAT1 and STAT2 pins I see them toggling between '01' and '10' in cyclic manner - ~2Hz. Seems they are indeed reflecting the register results.

Hope that it can give you some hint about the cause of this instability.

Best regards,

Hello Shony,

Thanks for working with this problem.

We recommend setting EN_PFM=0 when the battery termination current is less than 2A. Does setting EN_PFM=0 effect the behavior?

Best Regards,
Ethan Galloway

Thank you again. I will try that and let you know the results.

Hi Ethan,

I tried that. Unfortunately it wasn't helpful.

Anyway, I figure out that any register modification will not help, because I need it to work OK also while my system is power-off - the charger is powered but my CPU is off and can't control the charger.

Hello Shoney,

Thanks for letting me know. Let me get back to you later on this question.

Best Regards,
Ethan Galloway

Hello Shoney,

PFM can also be turned off by feeding in an external clock signal into FSW_SYNC. Is that an option for the system?

Best Regards,
Ethan Galloway

Hi Ethan,

I just figured out that the battery I am using is special one (BB-2590/U). It is combined of two independent battery packages, which I connected in series before charging with the BQ25750.

I think now that if the two are not fully charged and equalized carefully, the charger can't charge them correctly.

I tried two more batteries like it and found that each of them behave differently - one of them can't be charged at all and the second one charged 'correctly' and I finally got the stable Charging DONE from the charger.

And yet, even this third battery that fully charged is not absolutely OK, because I got the DONE only when the battery current reduced during tamper to only 30mA, instead of 400mA (10% of maximum defined charging current). I think that this is because even here the equalization is not absolutely fine.

So, this is very problematic battery. But I wonder if there is better, but yet simple, way to charge it?

B.R

Hello Shoney,

That is a strange battery.

Does the BB-2590/U have a battery monitor / battery gauge protector inside of it? Are there 2 devices or just 1?

Best Regards,
Ethan Galloway

Hi,

Yes. it has two complete battery packs inside. Each includes protection circuit, etc.

Meanwhile I discharged the 'good' battery and charging it again. Guess what? Now I got finally the DONE status as it should be - when tamper current reduced bellow 400mA. Case closed!