LM5116: LM5116 start up issue when SS cap is too large

Oscar Ye

Part Number: LM5116

Hi,

I have a startup issue with LM5116 when I put the ss capacitor around 2.2uF. The controller stop switching during the softstart. Please refer to the waveform below:

The CH3 is the feedback pin voltage and it is lower than the CH4 SS pin, but the control stopped switching. Could you please explain why?

This issue was not observed when I change the ss cap to 0.47uF.

Thank you.

Best Regards,

Oscar

over 7 years ago

0 Robert Loke over 7 years ago

TI__Prodigy 700 points

Hi Oscar,

can you please send the schematic you are using.

Thanks in Advance,

Robert Loke

0 Oscar Ye over 7 years ago in reply to Robert Loke

Prodigy 40 points

Dear Robert Loke:

Could you give me your E-mail address for send the schematic to you?

Thanks

0 Wei-Hao Chen (TW-FAE) over 7 years ago in reply to Robert Loke

TI__Expert 3260 points

Hi Robert,

Could you please provide the email for my customer? They are unable to share the confidential schematic online.

Thank you.

Best Regards,

Wei-Hao

0 David Baba over 7 years ago in reply to Wei-Hao Chen (TW-FAE)

TI__Mastermind 35750 points

Sorry for the delay,

Please send to david.baba@ti.com

0 David Baba over 7 years ago in reply to David Baba

TI__Mastermind 35750 points

Discussion continued over email. End user to rule out shoot through looking closely at Ho and Lo timing.

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LM5116: LM5116 start up issue when SS cap is too large