BQ24171: BQ24171 battery detect flow

Star Xu

Part Number: BQ24171

The customer design with BQ24171 to charge the 2 cells. They follow the datasheet 9.3.15 to do the battery detect test.

It was found that at the beginning of charging, charging stopped after maintaining a 100mA charging current for about 500ms, and the charging stop time was also about 500ms. During the period of stopping charging, the state changes from H to L. Then increase the charging current.

Attached the waveform.

Yellow: battery pack voltage

Blue: SW of charging IC

Red: charging current

Green: State of charging IC

Does it comply with the process in 9.3.15? The 125mA charging current is the red box part in flow? The 500ms to stop charging is Is it the switching time to start the official charging?

Please help check it.

Thanks

Star

5 months ago

0 Jeff F 5 months ago

TI__Guru*** 146695 points

Hi Star,

It appears to work correctly. Why does the battery voltage jump so high with only 125mA charge current and then fall so far? Is it a pack protector issue?

Regards,
Jeff

0 Star Xu 5 months ago in reply to Jeff F

TI__Genius 9645 points

Hi Jeff

Thanks for your help.

The reason for the voltage jumped and then recovered is the FET control problem on the battery protection board. There is no problem with the change of battery voltage.

Does 125mA, 0.5s charging correspond in the red mark? Later, charging stopped for 500ms. Is this IC switching mode from detecting battery access to normal pre-charge and CC modes?

0 Jeff F 5 months ago in reply to Star Xu

TI__Guru*** 146695 points

Hi Star,

Yes. After the initial drop, the charger appears to be functioning correctly. If you can zoom, you should see the precharge and then fast charge current.

Regards,

Jeff

0 Nineteen Chen 5 months ago in reply to Jeff F

Prodigy 20 points

Hi Jeff,

Yes,as you described，after charge current drop, I can the precharge and then fast charge current, as shown in the red box

I just want to know，after 500ms 125mA charge condition，why dose BQ2417 stop charging for 500ms？ what is BQ2417 doing during this 500ms period？

Is this consistent with the processing timing inside the chip?

0 Jeff F 5 months ago in reply to Nineteen Chen

TI__Guru*** 146695 points

Hi Nineteen,

The 0.5s timer is a deglitch to determine if the 125mA moved the VB pin enough to indicate a battery was connected. It is part of the battery detection algorithm.

Regards,

Jeff

0 Nineteen Chen 5 months ago in reply to Jeff F

Prodigy 20 points

Hi Jeff，

Thanks for your reply

Regards，

Nineteen

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BQ24171: BQ24171 battery detect flow