Output capacitor type for use with LD1117

Bvan .11 · ‎2022-05-31

Dear Forum members,

Could you please confirm if the LD1117 is specified to work with ceramic output capacitors?

Unfortunately the datasheet makes no mention of capacitor type or ESR requirements.

Thank you

Peter BENSCH · ‎2022-05-31

Welcome, @Bvan .11, to the community!

The LD1117, which is quite 20 years old, is a low-dropout regulator that requires an output capacitor of at least 10µF and an ESR (equivalent series resistance) of at least 0.3 ohms. 20 years ago, they simply used an electrolytic capacitor whose ESR was large enough. In addition, the large capacitance values of ceramic capacitors were not yet available at that time, so they were not mentioned in the data sheet.

If a tantalum capacitor is out of the question (there is massive criticism of the circumstances of tantalum mining), you can also use a ceramic MLCC, but then you should connect a resistor of approx. 0.5-2 ohms in series as an artificial ESR.

Does it answer your question?

Regards

/Peter

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View solution in original post

Tesla DeLorean · ‎2022-05-31

https://community.st.com/s/question/0D53W00000Aaci7SAB/ld1117s50-output-capacitor

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Peter BENSCH · ‎2022-05-31

Welcome, @Bvan .11, to the community!

The LD1117, which is quite 20 years old, is a low-dropout regulator that requires an output capacitor of at least 10µF and an ESR (equivalent series resistance) of at least 0.3 ohms. 20 years ago, they simply used an electrolytic capacitor whose ESR was large enough. In addition, the large capacitance values of ceramic capacitors were not yet available at that time, so they were not mentioned in the data sheet.

If a tantalum capacitor is out of the question (there is massive criticism of the circumstances of tantalum mining), you can also use a ceramic MLCC, but then you should connect a resistor of approx. 0.5-2 ohms in series as an artificial ESR.

Does it answer your question?

Regards

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

Bvan .11 · ‎2022-05-31

Thank you very much Tesla,

The link you provided to the other question/answer was very useful.

Regards

Bvan .11 · ‎2022-05-31

Hello Peter,

Thank you very much for your detailed response.

I suspected something like this.

Regards

Ben

Peter BENSCH · ‎2022-05-31

Great!

If the problem is resolved, please mark this topic as answered by selecting Select as best under your preferred answer. This will help other users find that answer faster.

Good luck!

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

Piranha · ‎2022-05-31

Take a look on LDL1117 - it's a newer and better design. Much better specifications and the required capacitors and ESR are documented good enough.

If something goes wrong, tantalum capacitors tend to fail with a short circuit and explode. Generally try to stick with a ceramic and aluminium electrolytic (especially the polymer) capacitors.

Bvan .11 · ‎2022-05-31

Hello Piranha,

Thank you for the suggestion, Indeed it does looks like a better option.

Regards

Ben