LP2951-N: Output Capacitor (Ceramic type)

Niels Ole Jorgensen

Part Number: LP2951-N

Hi.

I have a question regarding the output capacitors connected to a LP2951-N, where the datasheet have different statements:

Paragraph 8.3.7 (page 17) says, that the output capacitor can be a ceramic type with a ESR down to 6 mOhm
Paragraph 9.2.1.2.1 (page 20-21) says than an ESR of app. 5 Ohm is needed, and an extra resistor must be added in series with the output capacitor.

What is right and what is wrong? Can the LP2951-N run stable with just a ceramic output capacitor, or is an extra 1 - 2 ohm serial resistor needed?

The datasheet is marked "SNVS764P –JANUARY 2000–REVISED MAY 2016"

Best regards

Niels Ole Jorgensen

over 6 years ago

0 Ryan Eslinger over 6 years ago

TI__Guru 55940 points

Hi Niels,

The sections that you point out are not contradictory, although I agree the second section could be more clear. The second section is discussing how the criteria of an aluminum electrolytic where the recommendation is an ESR of 5 Ohm or less with a resonant frequency above 500 kHz.

LP2951-N is ceramic stable. Figure 30 from the datasheet is perhaps the clearest portion of the output capacitor ESR range for stability.

Very Respectfully,

Ryan

0 Niels Ole Jorgensen over 6 years ago in reply to Ryan Eslinger

Prodigy 110 points

Hi Ryan

Thanks for the answer.
I think you perhaps should consider rewriting the 2nd section, since far the most new designs now use ceramic capacitors.

Best regards
Niels Ole

0 sarath ravu over 6 years ago in reply to Niels Ole Jorgensen

Prodigy 30 points

HI Ryan
I have question for you reg LP2951N.I am using 0.47UF at the output of regulator.Is it required to keep low ohmic resistor in series with 0.47UF tantalum capacitor.My out load is 10 to 15mA.Suggest.what would be the out impedance of this LDO?

0 Ryan Eslinger over 6 years ago in reply to sarath ravu

TI__Guru 55940 points

Hi Sarath,

I will respond to your post here:

e2e.ti.com/.../639115

Very Respectfully,
Ryan

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LP2951-N: Output Capacitor (Ceramic type)