LMR14020 fsw=2.2MHz Setting

tateo yamashiro

Other Parts Discussed in Thread: LMR14020

Hi,

My customer has questions about LMR14020.
Could you tell us about questions?

[Question]
My customer consider the design of LMR14020 fsw=2.2MHz under the following conditions. My customer has questions.

<conditions>
Vin=9V to 14V
Vout=3.3V
Iout=1.5A
fsw=2.2MHz
Cout=ceramic capacitor

- How much is the value recommended of L and Cout? My customer will use ceramic capacitor for Cout.
- How much is the accuracy of fsw?
- Do you have a table of L, Cout and Cff typical values like the LM4360x?
- What the switching frequency is the best for the internal compensation?

Best Regards,
tateo

over 10 years ago

0 Anston Lobo over 10 years ago

TI__Genius 16025 points

We've received your query and will get back to you shortly.

Thanks,
Anston

0 Arief Hernadi over 10 years ago

TI__Mastermind 23845 points

webench_design_Tateo.pdfHi Tateo,

Please find the attached design file from webench for your conditions.

The accuracy of fsw if using the 1% Rt is about 20% according to the datasheet.

Unfortunately we do not have the table for recommended L and C value for this part but a webench design tool is a good start.

Normally for these kind of part, the internal compensation is done as such it covers the whole possible operation frequency.

I think it might be better to choose the switching frequency based on efficiency and size first since the compensation will covers the range.

Thanks

-Arief

0 tateo yamashiro over 10 years ago in reply to Arief Hernadi

Guru 10890 points

Thank you for your support.

I saw your suggestion. It use electrolyte capacitor for Cout.
I tried WEBENCH simuration, too. The result is electrolyte capacitors for Cout.
My customer want to use ceramic capacitor for Cout. Can we use ceramic capacitor for Cout?
Ceramic capacitor is cheaper than electrolyte capacitor.

Best regards,

tateo

0 Arief Hernadi over 10 years ago in reply to tateo yamashiro

TI__Mastermind 23845 points

Hi Tateo,

Yes you can use the ceramic capacitor. In the EVM they do use the ceramic capacitor. You can find the actual part number for it on the following link.
www.ti.com/.../snvu467.pdf

Thanks
-Arief

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LMR14020 fsw=2.2MHz Setting