BQ24232: Reverse current on BQ24232

Oliver Ou

Intellectual 2845 points

Part Number: BQ24232

Hi,

Customer uses BQ24232 with below circuit:

U6 is a boot converter, U70 is BQ24232, BAT_VCC connects to a small battery.

V_BAT connect to external battery to charger internal battery on BAT_VCC, the current is 30mA and meets design spec.

when removing the battery on V_BAT, there is a reverse current from U70 to U6, the current is higher to 63mA. and also see an oscillation on PV50 point(input of U70)

Could you check and give some comments for this phenomena?

Dose BQ24232 has reverse current blocking feature?

Thanks.

over 4 years ago

0 Raheem over 4 years ago

TI__Mastermind 21590 points

Hello Oliver,

The BQ24232 has reverse blocking feature. What's the frequency of the oscillation? Do you see a similar behavior without the boost converter?

0 Ma Hank over 4 years ago in reply to Raheem

Prodigy 30 points

Hi Raheem, I am the customer using this chip. The frequency is about 900Hz. It seems that the reverse block does not work when the V_BAT is removed.

0 Oliver Ou over 4 years ago in reply to Ma Hank

TI__Intellectual 2845 points

Hi Raheem,

Refer to Hank's feedback about the frequency，Could you give more comments or suggestion for this issue? If need more information, please let us know too.

Thanks a lot.

0 Raheem over 4 years ago in reply to Oliver Ou

TI__Mastermind 21590 points

Hello,

I'm curious where the current is coming from since there is no battery present. Can you try to first remove the boost converter and see if the issue occurs. Next, sent EN1 and EN2 high. This will turn off the input FET. And check again if the issue occurs.

0 Ma Hank over 4 years ago in reply to Raheem

Prodigy 30 points

There is a small Li-ion battery connected to the BAT1/2 of the U70. But the output of this chip is disconnected to the load. If the booster is removed, then it is OK. Or If I place a forward diode to replace the FB5, the bead connected to the booster and charger, then it is also ok. It may exist some unknown path... If I place a current meter in series with the battery at the charger side(BAT1/2), then it is also ok....

0 Raheem over 3 years ago in reply to Ma Hank

TI__Mastermind 21590 points

Hello,

If you remove the boost converter and just place a load on the input pin, do you see any current going from battery to input?

0 Raheem over 3 years ago in reply to Raheem

TI__Mastermind 21590 points

Hello,

Any updates here?

0 Oliver Ou over 3 years ago in reply to Raheem

TI__Intellectual 2845 points

Hi Ma Hank,

Could you post the test result here and continue the discussion?

Thanks.

0 Ma Hank over 3 years ago in reply to Raheem

Prodigy 30 points

we removed all of the circuit, only keep the charger chip, do the on/off test to observe the current flow in and out the battery. the below pcuture shows some current glitch. the second shows the details. It shows that the battery will suddenly provide current, but we did not have the load.

0 Raheem over 3 years ago in reply to Ma Hank

TI__Mastermind 21590 points

Hello,

This looks like the battery current going to the input capacitor right before the FET shuts off. If you place a resistor on the input around 10k and run the test, do you see this? The resistor will help discharge the input capacitors when power is removed which should cause the input FETs to turn off quickly. Are you able to try this test?

0 Raheem over 3 years ago in reply to Raheem

TI__Mastermind 21590 points

Any updates here?

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BQ24232: Reverse current on BQ24232