Soft start equation of TPS54227

Satoshi

Guru 19555 points

Other Parts Discussed in Thread: TPS54227, TPS54225

Please let me know about soft start equation of TPS54227.

On the datasheet page-9, soft start equation is below.

※Tss(ms) = (C6 x Vref x 1.1) / Iss

I don't understand multiplied "1.1".

（TPS54225 are not multiplied 1.1）

What mean is "1.1"?

Best regards,

Satoshi

over 7 years ago

0 JohnTucker over 7 years ago

TI__Guru**** 191445 points

From the IC designer:

"I add the one Vbe voltage shift function of the SS pin for the latest CS version.
Because high output current caused rapid SS voltage up due to the parasitic inductance.
So I added the one bipolar transistor in order to protect the noise.
As a result, SS start up is somewhat delayed. So you need to include the 1.1 factor.

0 Satoshi over 7 years ago in reply to JohnTucker

Guru 19555 points

Jorn Tucker-san

Thank you for quick reply.

If there spec information for Min~Max value (or accuracy) of 1.1 factor, please let me know.

Best regards,
Satoshi

0 JohnTucker over 7 years ago in reply to Satoshi

TI__Guru**** 191445 points

So far as I know there is no specification for it.

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Soft start equation of TPS54227