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LM2596: "Phase Margin" parameter in WEBENCH ?

Vladimir Naumenkov
Prodigy 120 points
Part Number: LM2596

Dear Sir, good morning

I made a calculation in WEBENCH, please see attach.

I don't see option  "phase margin" .  Why?

Sincerely,

TIA

Vladimir Naumenkov 

LM2596-12V_1A.pdf

  • +1
    TI__Guru 64055 points

    Hello

    I will assign this post to someone that can help you.

    Thanks

  • +1
    TI__Prodigy 490 points

    Hi Vladimir,

    The WEBENCH for the LM2596 12Vout fixed option does not include a means to get the phase margin. 

    An alternative approach to get the phase margin for the 12Vout fixed option is to use the WEBENCH design tool for the 12Vout adjustable option and modify the external feedback resistors to match the internal feedback resistors that are used in the 12Vout fixed option. These feedback resistor values can be found in section 8.2 Functional Block Diagram in the datasheet. In your WEBENCH design, that would mean Rfb1 = 2.5kΩ and Rfb2 = 21.8kΩ. 

    To find the value of the feedforward capacitor, CF, equation 10 in the datasheet can be used. This results in a CF value of 1.5nF. 

    I have run the simulation with your design inputs using this method, and the resulting phase margin was 95.083 degrees. Design report is attached below. 

    LM2596_12V_ADJ_1A.pdf

    Regards,
    Carol

  • +1 in reply to Carol Zhang
    Prodigy 120 points

    Dear Carol, thank you

    Sincerely

    Vladimir Naumenkov