BQ25730: The *BATDRV pin does not transition to 'L'

Masashi Mineda

Part Number: BQ25730

Tool/software:

Dear Sirs and Madams,

We are fabricating and evaluating a BQ25730 board.

We are evaluating multiple boards, and a problem occurs where *BATDRV does not transition to 'L', so the BATFET turns OFF, causing current to flow from the body diode of the BATFET to the load. There was a board.

The results of observing input power, load power, and battery power are shown below.

The initial settings of the various registers are the same.

In the above measurements, the PSU and battery were left unchanged, only the board was measured.

I checked the CHRG_INHIBIT on the board that is not charging and it was 0b.

We would like to turn on BATFET for all boards and charge the battery, but do you know why it goes into power pass mode like this?

Regards,

10 months ago

0 Tiger Zhou 10 months ago

TI__Mastermind 32715 points

Hi, MM,

it looks the charge operation is stopped in the second case. It could be the watchdog timer or any fault.

Regards

Tiger

0 Masashi Mineda 10 months ago in reply to Tiger Zhou

Expert 1155 points

Hello Tiger,

We confirmed for the faults of the product that was working properly and the product that was not working properly, but there was no difference in the faults.

The incidence of boards exhibiting problematic behavior is quite low.

Is there anything else you can think of?

Regards,

0 Tiger Zhou 10 months ago in reply to Masashi Mineda

TI__Mastermind 32715 points

Hi, MM,

Please tie the CELL_BATPRESZ pin to the REGN and configure the part for 5S.

This will raise the SYSOVP level and avoid the SYSOVP fault. BTW, there is no register bit to indicate the SYSOVP fault.

Regards,

Tiger

0 Masashi Mineda 10 months ago in reply to Tiger Zhou

Expert 1155 points

Hello Tiger,

I checked our customer's schematic and CELL_BATPRESZ pin is connected to VDDA, so when I measured it, it was set to 6V for 5S.

I am thinking about replacing the BATFET, but do you know anything else I should check?

Regards,

0 Tiger Zhou 10 months ago in reply to Masashi Mineda

TI__Mastermind 32715 points

Hi, MM,

Feel free to change the BATFET, however, I am confused about the PFET status. Below photo shows the BATFET is ON, otherwise there should be 0.7V diode drop on the FET. Could you measure the BATDRV voltage together with VBAT, VSYS?

Regards,

Tiger

0 Masashi Mineda 10 months ago in reply to Tiger Zhou

Expert 1155 points

Hello Tiger,

The waveforms of VSYS(Source), VBAT(Drain) and *BATDRV(Gate) were measured.

The P-MOS FET used for BATFET is PDC3901X.

Is this problem due to the high Ciss of PDC3901?

Regards,

0 Tiger Zhou 10 months ago in reply to Masashi Mineda

TI__Mastermind 32715 points

Hi, MM,

The above plot shows the PFET is ON, the VGS(PFET)= VSYS-VBATDRV=19-16.8=2.2V.

The BATDRV current is weak, you should choose a PFET with CISS<5000PF.

Regards,

Tiger

+1 Masashi Mineda 9 months ago in reply to Tiger Zhou

Expert 1155 points

Hello Tiger,

I apologize for the late reply.

When we verified the operation, we found an issue where the bottom FET on the Boost side could not be fully turned on.

We confirmed that changing the bottom FET improved operation.

Thank you for your advice.

Regards,

Power management

Power management forum

BQ25730: The *BATDRV pin does not transition to 'L'