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Original question:

LM51231-Q1: Loop stability and compensation

LM5123-Q1: Loop Compensation Component Value Selection

C Justin Smith
Prodigy 10 points
Part Number: LM5123-Q1

I have used both the WEBENCH Power Designer and the spreadsheet based tool to calculate the compensation network component values for an LM5123-Q1 boost converter with the following parameters with wildly different results.

Vin: 12-15V

VinNom: 13.8V

Vout: 50V

Iout: 4A

Fsw: 200kHz

The WEBBENCH Power Designer suggests the following component values:

Rcomp: 2.94kOhm

Ccomp1: 470nF

Ccomp2: 3.3nF

The spreadsheet quickstart tool suggests the following component values:

Rcomp: 110kOhm

Ccomp1: 8.8nF

Ccomp2: 33pF

These values are quite disparate and so I am wondering which tool I should trust. Thank you for your assistance!

CJRS

  • 0
    TI__Genius 13535 points

    Hi Justin,

     You should determine the crossover frequency/ phase margin you want to have first, and then find the component values. Both component values can be OK as they have different crossover frequency/ phase margin.

    Best Regards,

    Feng Ji

  • 0 in reply to Feng Ji
    TI__Mastermind 46951 points

    Hi Justin,

    I have not seen an update for the last 22 days, so I assume the questions are/or answered and the issue is solved.
    I close this thread now. If there is still something open reply and the thread will get open again.
    If you have any other question or of the thread gets locked, please open a new one.

    Clicking the Resolved Button also helps us to maintain this forum.

    Best regards,
    Stefan