Low-ESR capacitor for TPS54310

Anonymous

Other Parts Discussed in Thread: TPS54310

Hello,

I would like to ask about the requirement of capacitor for TPS54310.

I am referencing the design of SpectrumDigital’s EVM6437. In its schematics, page 34, there is a low-ESR 10uF polarized capacitor C342 connected to VIN pins.

From its BOM I found the device for C342, and Digikey search doesn’t seem to suggest any characteristics of low-ESR (low equivalent serial resistance).

So my question is low-ESR a must? Can EMK325F106ZF-T be used?

Thanks,

Zheng

over 13 years ago

0 JohnTucker over 13 years ago

TI__Guru**** 191445 points

That looks to be a non-polarized ceramic capacitor. Even though the ESR is not specified it is probably low. However I do not recommend using Y5V dielectric in this application. You should use X5R or X7R.

0 Anonymous over 13 years ago in reply to JohnTucker

Guru 17045 points

Dear John,

Thanks for advice, I will choose X7R.

But does it has to be

1. Low-ESR or not

2. Polarized or not

3. Tantalum or not

Could you give an authoritative answer on this?

Zheng

0 Anonymous over 13 years ago in reply to JohnTucker

Guru 17045 points

Quote:

"That looks to be a non-polarized ceramic capacitor. Even though the ESR is not specified it is probably low."

Does it mean that low-ESR is more commonly a feature of ceramic capacitor than tantalum capacitor?

Zheng

0 JohnTucker over 13 years ago in reply to Anonymous

TI__Guru**** 191445 points

Use a ceramic non-polarized capacitor. Dielectric X5R or X7R. Sometimes the ESR spec is hard to find or unpublished, but they are usually less than .005 ohm for that type of cap.

In general ceramic is the lowest ESR.

0 Anonymous over 13 years ago in reply to JohnTucker

Guru 17045 points

Dear John,

I got it, thanks very much.

Zheng

0 Sudharsan K over 10 years ago in reply to JohnTucker

Intellectual 385 points

Does adding parallel capacitors reduces the ESR of the cap?

In case we are expecting ESR of 2mOhm, if we use 3 capacitors of each (5mOhm ESR) will the resultant cap be 1.5mOhm ESR?

0 JohnTucker over 10 years ago in reply to Sudharsan K

TI__Guru**** 191445 points

If you put capacitors in parallel, the Effective ESR is reduced. Froma a small signal standpoint the ESR zero stays the same. Fz = 1/ (2*pi*nC*Resr/n), the "n" (number of capacitors) cancels out. If you mix the types of capacitors, say an electrolytic and a ceramic, it becomes more complicated.

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Low-ESR capacitor for TPS54310