LM317's capacitors

Nicolas Prieto Angueira

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I'm using a LM317 with 0.1uF ceramic capacitors on the input and output. Would it improve its transient response and ripple rejection if I use tantalum capacitors instead of ceramic ones? What values should I use for input and output?

Thank you!

Regards!

over 13 years ago

0 Ron Michallick over 13 years ago

TI__Guru**** 164796 points

Hello Nicolas,

Ceramic capacitors are better for transient response. A capacitor on the adjustment pin to ground helps both parameters.
How much output ripple and transient shift are you observing? How much reduction do you require?

Regards,
Ron Michallick

0 Nicolas Prieto Angueira over 13 years ago in reply to Ron Michallick

Prodigy 70 points

I just want to use the better option because the certification tests for the equipment I'm developing are really rough. I want to filter in the best way my voltage source so I don't have problems in the certification.

Thank you.

0 Ron Michallick over 13 years ago in reply to Nicolas Prieto Angueira

TI__Guru**** 164796 points

Nicolas,

I tried different capacitors in the lab yesterday, The results looked best when the input capacitance was at least 1uF and the output capacitance was at least 10uF. I did not notice much difference between ceramic and tantalum.

Regards,
Ron Michallick

0 Oliver over 13 years ago in reply to Ron Michallick

Prodigy 50 points

Hello,

I want to use LM317 regulator but I am not allowed to use tantalum capacitors because of fiability issues, they are forbidden in my company.

Is it possible to replace output capacitor with a 10 uF Ceramic X5R capacitor like Murata GRM31CR61E106MA12 ?

Best regards

0 Ron Michallick over 13 years ago in reply to Oliver

TI__Guru**** 164796 points

Oliver,

Yes, ceramic output capacitors can be used.
That capacitor is OK to use.

Regards,
Ron Michallick

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LM317's capacitors