TPS54325: Iout=0A don't have a smooth Vout

Brian Chan

Part Number: TPS54325

Hi Experts

the Vout would be higher and go back to normal value after delay.

do you think it would be relate to PG? could I solve it by use larger soft start capacitor or other way you can suggest it?

CH1 input

Ch2 output

Ch3 PG

Ch4 Iout

best

regards

brian

over 1 year ago

0 Zixu Wang over 1 year ago

TI__Expert 8100 points

Hi Brian,

I will check and give you feedback soon!

BRs

Zixu

0 Brian Chan over 1 year ago in reply to Zixu Wang

TI__Expert 3830 points

Hi Zixu

any feedback form you

best

regards

brian

0 Zixu Wang over 1 year ago in reply to Brian Chan

TI__Expert 8100 points

Hi Brian,

I have conducted test on EVM with default setup, whose ss cap is 3300pF. I did not find your mentioned phenomenon.

Could you please help to measure Vout + SW + VREG5+ Vin?

BRs

Zixu

0 Brian Chan over 1 year ago in reply to Zixu Wang

TI__Expert 3830 points

Hi Zixu

this is Vout +SW + VREG5 +Vin waveform

best

regards

brian

0 Zixu Wang over 1 year ago in reply to Brian Chan

TI__Expert 8100 points

Hi Brian,

Thanks! I will analyze it and give you feedback soon!

BRs

Zixu

0 Zixu Wang over 1 year ago in reply to Brian Chan

TI__Expert 8100 points

Hi Brian,

Based on your shown waveform, Vout drop is caused by abnormal DCM operation in startup. In DCM operation, Vout would be boosted to higher value for DCAP2 converter. But TPS54325 is FCCM part from bench test, which means the DCM operation is not supposed to be shown.

I found similar e2e thread for your reference.

(+) TPS54325: Pulse skip when powering up with no load - Power management - INTERNAL forum - Power management - INTERNAL - TI E2E support forums

Since I did not replicate customer phenomenon on our EVM, three actions could be conducted from my side:

1. Please share layout of customer

2. Please remove C267 to check whether this phenomenon still exists.

3. Please conduct ABBA test for customer.

Anything unclear, please let me know.

BRs

Zixu

0 Brian Chan over 1 year ago in reply to Zixu Wang

TI__Expert 3830 points

Hi Zixu

thx for your detail reply

My customer also have other question

Best

Regards

Brian

0 Athos Zhao over 1 year ago in reply to Brian Chan

TI__Expert 7320 points

Hi Brian,

Since we're in a vacation until June 25th, Zixu will reply you next Monday.

0 Brian Chan over 1 year ago in reply to Athos Zhao

TI__Expert 3830 points

Hi Zixu

attached file is layout. could you help me check it ?

142000003403AR0A-B-0420.zip

best

regards

brian

0 Brian Chan over 1 year ago in reply to Zixu Wang

TI__Expert 3830 points

Hi Zixu

#2, If we remove the C267, it will let the Bode plot fail.

Why do we remove the C267?

In addition, in our test, scale is 20mV/Div.

I think it should see the same performance in EVM.

#3 what do you mean ABBA test?

In has the same result in series of 48P.

best

regards

brian

0 Zixu Wang over 1 year ago in reply to Brian Chan

TI__Expert 8100 points

Hi Brian,

I will check all your threads soon.

ABBA means following actions: solder normal parts on customer board to check whether issue happens & solder customer failed part on our EVM to check whether issue happens.

Removal of C267 is to check whether this phenomenon is related with Cff. Does the issue still happen if C267 is removed?

BRs

Zixu

0 Brian Chan over 1 year ago in reply to Zixu Wang

TI__Expert 3830 points

Hi Zixu

the phenomenon still happen after remove C267.

BRs

Brian

0 Zixu Wang over 1 year ago in reply to Brian Chan

TI__Expert 8100 points

Hi Brian,

I will conduct further analysis based on customer BOM on EVM.

For other questions, I will analyze and give you feedback soon!

BRs

Zixu

0 Ann_Lien over 1 year ago in reply to Zixu Wang

TI__Genius 11820 points

Hello Zixu,

Since this issue lasts two weeks, customer would like to have a update from our side. Could you kindly check if the EVM result will or will not have this issue? Or if you can provide the reason why this Vout will have step, it might be helpful for us? Sorry to push you but customer need an answer tomorrow morning timeframe. Thanks!

Best regards,

Ann Lien

0 Zixu Wang over 1 year ago in reply to Ann_Lien

TI__Expert 8100 points

Hi Ann,

Will communicate via email. I am analyzing it carefully on EVM and will close the thread.

BRs

Zixu

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TPS54325: Iout=0A don't have a smooth Vout