TPS548D22: TPS548D22 Tdelay_min

user4671884

Part Number: TPS548D22

Hi TI Team,

In section 7.5.1.3.1 of TPS548D22's DATASHEET, if I want to set risetime to 4mS or 8mS, the Tdelay_min should be larger than 9mS or 18mS. what will happen if the Tdelay_min is shorter than 9mS or 18mS?

Thanks and best regards

Lancer Zhang

over 7 years ago

0 JohnTucker over 7 years ago

TI__Guru**** 191445 points

I am checking on this. The easy answer is to ensure your delay is longer than the minimum then you don't need to worry about it.. I'll let you know what I find out.

0 user4671884 over 7 years ago in reply to JohnTucker

Prodigy 30 points

Hi John，

This note is added in Rev.D, our project is in the stage of small MP, it's hard to change it, so please check this, Tks a lot.

BR!

Lancer_zhang

0 JohnTucker over 7 years ago in reply to user4671884

TI__Guru**** 191445 points

I'll see if I can find out the details next week. If we added that to the datasheet with a revision, then I'm sure someone found a real problem with it that caused us to make that addition. Have you noticed any start up issues during your testing? What is your actual delay time on your board?

0 JohnTucker over 7 years ago in reply to JohnTucker

TI__Guru**** 191445 points

Basically, there are 3 distinctive behaviors associated with this issue. They are:
The SS time appears to be much longer than the spec. And Vout startup waveform shows discrete steps prior to regulation.
PGOOD is asserted well before Vout reaches regulation.
OVP is triggered during startup at certain no load condition.

Let me know if you need anything else.

0 user4671884 over 7 years ago in reply to JohnTucker

Prodigy 30 points

I got it, It seems we must change the delay time or SS time, TKS a lot!

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TPS548D22: TPS548D22 Tdelay_min