LM5122: Which CComp equation is best

Jon Loeck

Part Number: LM5122

Tool/software:

Thanks for releasing V1.1.0 Quickstart Calculator spreadsheet and fixing the issue with the RCOMP calculation. It appears that the datasheet EQ 48 needs updating also.

For calculating Ccomp , the datasheet suggests using "twice the Load Pole Frequency" (Equation 49), The document "Under the Hood of a Multiphase Synchronous Rectified Boost Converter" suggests using Fcross/10 ( Equations 39 and 40), and it appears the Quickstart Calculator uses the actual Power Pole frequency.

Out of the three options, which is the best choice?

3 months ago

0 Feng Ji 3 months ago

TI__Mastermind 22790 points

Hi Jon,

The expert will be back on Monday.

Please expect a reply by then.

Best Regards,
Feng

0 Niklas Schwarz 2 months ago in reply to Feng Ji

TI__Mastermind 30260 points

Hi Jon,

Thanks for the feedback on the quickstart calculator update.
I agree that the equations (48) and (49) in the datasheet need to be updated as well, to match with the calculator again.

Regarding the document "Under the Hood of a Multiphase Synchronous Rectified Boost Converter", do you mean these equations?

This equation for Ccomp is valid and the results should match with the updated quickstart calculator and our power stage designer tool.

Best regards,
Niklas

0 Jon Loeck 2 months ago in reply to Niklas Schwarz

Prodigy 10 points

Yes, that is the other equation I referred to but it gives me a Ccomp value nearly 1/4 that of the quickstart calculator.

0 Niklas Schwarz 2 months ago in reply to Jon Loeck

TI__Mastermind 30260 points

Hi Jon,

This is unexpected.
Could you send me your filled in quickstart calculator once more?
This is so I can double check the calculations to see if I get the same results.

Thanks and best regards,
Niklas

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LM5122: Which CComp equation is best