TPS40170: min and max value of Css

Shinichi Inoue

Guru 21566 points

Part Number: TPS40170

Dear Specialists,

My customer is considering TPS40170 and has a question.

Could you please advise?

---question

(1)According to the datasheet P.19 7.3.5.2 Equations for Soft-Start and Restart Time, it describe tss and Css.

Is there a min and max Css value?

(2) Could it possible to use the condition below?

Css:2.2uF

Tss=Css[ns]×0.09＝2200*0.09=198msTss=Css[ns]×0.09＝2200*0.09=198ms

Is it OK?

---

I appreciate your great help.

Best regards,

Shinichi

over 8 years ago

0 Shinichi Inoue over 8 years ago

Guru 21566 points

Hi all,

Your immediate response is highly appreciated.

Best regards,
Shinichi

0 Shinichi Inoue over 8 years ago in reply to Shinichi Inoue

Guru 21566 points

Hi everyone,

I think there is not limitation of softstart cap(Css), but larger capacitance causes a false operation, so it must take care of noise.

I am looking forward to receiving your suggestion.

Thank you.

Best regards,
Shinichi

0 Arief Hernadi over 8 years ago in reply to Shinichi Inoue

TI__Mastermind 23845 points

Hi,

A couple of suggestions:

1) You can try to simulate your design using TINA spice and see if that is ok. I think it should be ok.

2) What is your reason on having a slow soft-start time? You can have a delay also on UVLO pin in combination with soft-start.

Thanks

-Arief

0 Shinichi Inoue over 8 years ago in reply to Arief Hernadi

Guru 21566 points

Hi Arief

Thank you for your reply.

The customer wants to know the range of soft start capacitor in advance.

In some cases the value are determined in advance.

I'll confirm later, and I also think it's ok.

I appreciate your great help and cooperation.

Best regards,
Shinichi

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TPS40170: min and max value of Css