BQ24773: Vsys, PH unable to regulate

Victory Loh

Prodigy 60 points

Part Number: BQ24773

Hi,

Thanks for your support.

Our application of BQ24773

Input voltage: 18.2V

Battery: 4s4p (12v~16.4v, 10800mAh)

I've found one of the defect board has the problem of unable to regulate Vsys.

I've captured the VIN, ACDET, REGN, ACOK, VSYS, and PH signals as below. (below condition was without insertion of battery)

The ACOK signal rise after ACDET & REGN about ~800msec, which I think it was abnormal.

VSYS and PH also doesn't not regulate normally.

ACDET, and REGN work normally.

VIN is the drain voltage of high side switching mosfet. (ACFET & RBFET work fine.)

Could you advice under what kinds of circumstances that will happen this kinds of defect?

I can provide you our schematic through email, if possible please let me know your email. Thanks a lot!

regards,

over 4 years ago

0 Angelo Zhang87 over 4 years ago

TI__Genius 11850 points

Hi Victory,

I have sent you a friend request through E2E. Please accept this friend request and then send me the schematic through a private message.

Victory Loh said:
I've found one of the defect board has the problem of unable to regulate Vsys.

Do you mean that you have tested multiple boards, and only some of them show this issue with regulating VSYS and no switching? Or do all of the boards behave the same way?

Best regards,

Angelo

0 Victory Loh over 4 years ago in reply to Angelo Zhang87

Prodigy 60 points

Thanks for your reply. I've sent you the schematic through PM. Yup, I've several pcs of prototype board, this is the only one that having problem.

+1 Angelo Zhang87 over 4 years ago in reply to Victory Loh

TI__Genius 11850 points

Hi Victory,

I suggest increasing C86 from 100 pF to 1 nF in your schematic, and you can also remove C109. However, I don't think this would cause the behavior that you're seeing on the defective board, where there is no switching or VSYS regulation.

Since only one of the boards shows this issue, can you try swapping the BQ24773 on the failing board with a known good IC? Does the defective board work after changing the IC?

Best regards,

Angelo

0 Victory Loh over 4 years ago in reply to Angelo Zhang87

Prodigy 60 points

Thanks for your help and advice.

Yup, I'll do the swap test for the defect IC.

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BQ24773: Vsys, PH unable to regulate