LM74722-Q1: LM74722+TPS3760 slow rise Fail

jianyan xia

Prodigy 50 points

Part Number: LM74722-Q1
Other Parts Discussed in Thread: TPS3760

Tool/software:

Hi teams,

Please help to check it ,many thanks!

solution: LM74722+TPS3760

test item:slow rise

description: when the voltage of KL30_VBAT1 rise to 5.61V, the voltage of KL30_VBAT1 and KL30_PORTA suddenly drop,after the KL30_VBAT1 rise to 5.61V again, The KL30_PORTA is not power on, why the KL30_VBAT1 drop to ~4.4V?(reference the red arrow of the test picture)

SCH reference

7 months ago

0 Shiven Dhir 7 months ago

TI__Mastermind 37820 points

Hi Jianyan,

I cant find the Vs pin in the schematic. Where is it?

Regards,

Shiven Dhir

0 jianyan xia 7 months ago

Prodigy 50 points

Hi Shiven ,

What is the 'Vs pin' meaning?

0 jianyan xia 7 months ago

Prodigy 50 points

any updated?

Many thanks!

0 jianyan xia 7 months ago

Prodigy 50 points

Hi teams ,

Please add comments?

Thanks!

0 Shiven Dhir 7 months ago in reply to jianyan xia

TI__Mastermind 37820 points

Hi Jianyan,

Sorry for delay in response. Schematic looks fine to me. Only thing to point out is that we recommend keeping total OV ladder resistor value <120k.

What is the input source? Is there any current limit on the source?

Regards,

Shiven Dhir

0 jianyan xia 7 months ago in reply to Shiven Dhir

Prodigy 50 points

Hi Shiven ，

Thank you!

Only thing to point out is that we recommend keeping total OV ladder resistor value <120k.

--- If the total OV ladder resistor value <120k , the leakage current would be larger. If the total OV ladder resistor value >120k , what is the adverse effects?

What is the input source? Is there any current limit on the source?

Chroma, Yes,110A.

I was also confused ,why the voltage suddenly drop ?

0 jianyan xia 7 months ago in reply to jianyan xia

Prodigy 50 points

During this time(reference the red arrow of the test picture), only LM74722+TPS3760 work

0 jianyan xia 7 months ago in reply to jianyan xia

Prodigy 50 points

Hi teams, any updated?

0 Shiven Dhir 7 months ago in reply to jianyan xia

TI__Mastermind 37820 points

Hi Jianyan,

I understand that chroma,110A is used. Is there any current limit set on chroma as well?

Looks like some downstream load is being turned-on which chroma is not able to supply and VIN droops. When VIN droops, TPS3760 resets the EN and this cycle repeats.

Can you test with R2417 DNI and R2418 populated to break this loop and see the behavior. This looks to be some setup issue.

Regards,

Shiven Dhir

0 jianyan xia 6 months ago

Prodigy 50 points

Hi shiven ,

Thanks very much,I change the chroma to other power supply,it's OK now,and I test the current of KL30_VBAT1, it's nearly to zero at the first turing.(the bule arrow)