BQ25120: Li-Po deep discharge issue

Damien Genouille

Part Number: BQ25120

Hi TI team,

We seem to have an issue with the BQ25120 when it comes to charging a battery pack that has a blocked PCM, meaning VBAT = 0V, because of overdischarge.

To be unlocked, there should be a current injected into the battery so that the PCM re-opens the power path, however when plugging in a blocked battery and then a valid VIN (4.96V), the BQ does not do anything: no current measured on the battery cables, still 0V at its terminals.
There is only a small glitch on VBAT as you can see here:

Figure: VBAT when 5V is put on VIN

Here is the registers dump while the charger is attached but the battery is still blocked:

Register	Value
00	C1
01	20
02	00
03	9D
04	BA
05	78
06	BA
07	00
08	68
09	14
10	78
11	C2

Is there any register manipulation we should do to enable PCM unlock?
Is the BQ25120 even able to detect and unblock a battery pack in such condition?

Thank you,
Best regards,

Damien

over 7 years ago

0 Damien Genouille over 7 years ago

Intellectual 365 points

Hello,
Any news about this thread?
Thanks,
Damien

0 Gautham over 7 years ago in reply to Damien Genouille

TI__Genius 12485 points

Damien,

We recently released the BQ25120A device which is recommend for all our customers to move to.

That being said- We have addressed this issue on the BQ25120A where we can startup with any BAT condition. Could you check PMID? if PMID doesnt come up- it reflects the issue we fixed on the original version 1 of the silicon.

The old silicon had a requirement of BAT to not be between 0.2V to 1V when startup.

regards,

gautham

0 Damien Genouille over 7 years ago in reply to Gautham

Intellectual 365 points

Hi Gautham,

Sorry for the late reply.

We will make sure to switch to BQ25120A ASAP.

However I checked PMID and it does come and stay up when VIN is switched on:

Also, I checked VBAT again when swithcing VIN on, and here is what I get:

Not sure why I did not get this behaviour last time I checked. VBAT voltage eventually gets to 0V and does not come up again unless I recycle VIN.

Obviously, PMID does not come up unless VIN is switched on as VBAT=0V when the battery pack PCM is blocked.

Is this the same issue as depicted in your reply that should be solved with new silicon?

Thanks,

Damien

0 Andrey Mostovov over 7 years ago in reply to Damien Genouille

Prodigy 65 points

Hi Gautham,

any feedback on that?

0 Gautham over 7 years ago in reply to Andrey Mostovov

TI__Genius 12485 points

Andrey, Damien,

I am reviewing the data. I should have feedback in a few hours.

0 Gautham over 7 years ago in reply to Gautham

TI__Genius 12485 points

Damien,

Good question- i see that there might have been a fault triggered that might have caused this. PMID coming up is a good sign- the behavior on the non A version is that PMID won't come up.

1. Are you seeing any other faults than the UVLO?

2. If i revert to your register settings on the begining of the forum post, /CD is showing Low. Please confirm as well.

regards,

gautham

0 Damien Genouille over 7 years ago in reply to Gautham

Intellectual 365 points

Hi Gautham,

1. No other fault than BUVLO.

2. /CD pin is low when inserting charger, however there is a small glitch @~870ms after strartup below (yellow is VIN, blue is /CD)

Zoom on /CD glitch:

Thanks,

Damien

0 Gautham over 7 years ago in reply to Damien Genouille

TI__Genius 12485 points

Damien,

Given this information, i dont see any issue. Let me contact you offline on your email. i have your info.

thanks,

gautham

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BQ25120: Li-Po deep discharge issue