BQ24296: Charger hanged when battery discharged

Vladimir Aparin

Part Number: BQ24296

Hello, we using BQ24296 with typical schematics. All working good most times.

But time-to-time we got strange behavior. When we disconnect external power supply from charger battery going discharge as expected. It happens until battery fully discharged (0.8V on battery, 0.5V on SYS). It's first strange point because BQ24296 has integrated discharge protection on 2.4V. Battery should not discharge below this voltage.

When we connect external power supply voltage on BAT going down to 0.6V, while SYS increased up to 0.8 V. We can't access to BQ24296 registers in this mode. Charger just hanged.

We can going out from this state only when battery will disconnected while external power will connected. After it all working good again.

over 7 years ago

0 Joel Hernandez II over 7 years ago

TI__Mastermind 25800 points

Hey Vladimir,

Does your battery have a protector circuit integrated?

If so, are you measuring the BAT pin voltage (on the bq24296 charger) or on the Cell+ of the protector?

Do you have a schematic you can provide, even though you are using the typical schematic?

Regards,

Joel H

0 Vladimir Aparin over 7 years ago in reply to Joel Hernandez II

Expert 2610 points

Hello Joel,
Yes Battery has an integrated protection schematics. And we think, that this protection works. Because after power up BQ24296 and reattach battery it charging fast up to normal voltage (3.4 V). So we can make conclusion that protection in latch mode. What can you recommend in this case?

0 Vladimir Aparin over 7 years ago in reply to Joel Hernandez II

Expert 2610 points

Now I think that problem may lay in D26 (LDO) directly connected to Battery (X2 connector). When protection latch worked it can't turn off until battery has any load (at least LDO in this schematics).

0 Joel Hernandez II over 7 years ago in reply to Vladimir Aparin

TI__Mastermind 25800 points

Hey Vladimir,

Just to clarify, you are saying the protection circuit for the battery is latching off, and will not re-open until there is not load on the output?

Regards,

Joel H

0 Vladimir Aparin over 7 years ago in reply to Joel Hernandez II

Expert 2610 points

Yes, it is, as we understand now.
As I think it may leads to hanging of BQ24296. Can you approve or deny this mention?

0 Joel Hernandez II over 7 years ago in reply to Vladimir Aparin

TI__Mastermind 25800 points

Hey Vladimir,

What battery protector are you using?

I didn't see it in the schematic you posted. Or is it an integrated battery protector?

Regards,
Joel H

0 Vladimir Aparin over 7 years ago in reply to Joel Hernandez II

Expert 2610 points

It's integrated protector.

0 Joel Hernandez II over 7 years ago in reply to Vladimir Aparin

TI__Mastermind 25800 points

Hey Vladimir,

Have you tried using a battery simulator to do the same thing, instead of the real battery with integrated protector?

You can use a bipolar/quadrant power supply that can source/sink current. We typically use Kepco or Keithley supplies to do this.

You can also try using a different battery (no protector) and see if the same behavior exists.

If not, you may have to work with battery/protector manufacturer to understand the latch condition. We may also want to at what else in your system is on the VBAT or VSYS power rails, if any.

If yes, then we can investigate further.

Regards,

Joel H

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BQ24296: Charger hanged when battery discharged