TPS53355 MODE pin pull-up by external power supply

Keiichi Kajino

Expert 2365 points

Other Parts Discussed in Thread: TPS53355

Hi, folks

Our customer wants to pull-up MODE pin of TPS53355 to external power supply not VREG.

I guess the TPS53355 wiil fetch SS setting by MODE pin after 250us from enable, so it will be NO problem.

Am I correct?

over 9 years ago

0 JohnTucker over 9 years ago

TI__Guru**** 191445 points

Why would they want to do that? It is recommended to pull MODE up to PGOD so that it will operate in skip mode during SS time and then transition to FCCM. Are you going to pull up to 5 V?

0 Keiichi Kajino over 9 years ago in reply to JohnTucker

Expert 2365 points

John,

I am sorry I misunderstood, its pull-up source should be PGOOD not VREG.
Thank you for your pointing out.

0 Keiichi Kajino over 9 years ago in reply to Keiichi Kajino

Expert 2365 points

John,

I am sorry I misunderstood again. What we want to ask is about Pull-up source.
The recommendation is VREG(eq to 5V) via pull-up resistor, but we would like to connect to external 3.3V via pull-up resister.
Does it cause any problem?

0 JohnTucker over 9 years ago in reply to Keiichi Kajino

TI__Guru**** 191445 points

I am not 100% certain, but I doubt you can pull up to 3.3 V source. I am pretty sure the pull up values are calculated for 5 V pull up. Let me see if I can find someone who knows for sure.

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TPS53355 MODE pin pull-up by external power supply