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TPS65150: The phase margin at boost converter

Hirotaka Matsumoto
Guru 27585 points
Part Number: TPS65150

Hi all

Would you mind if we ask TPS65150?

There is the description on Table 1. Recommended Compensation Components for Different Input Supply Voltages.
When we consider the phase margin = more than 45degree, should we configure 1/2π√LC < FEED-FORWARD ZERO CUT-OFF FREQUENCY?
What we would like to know is the part which is relation to the phase margin.

Kind regards,

Hirotaka Matsumoto

  • 0
    TI__Mastermind 18550 points
    Hello Matsumoto-san,
    I will look into this and get back to you in the next couple of days.
    Kind Regards,
    Liaqat
  • 0
    TI__Mastermind 18550 points

    Hello Matsumoto-san,

    My apology for a delayed response. To have a higher phase margin, the design should target cross over frequency that is less than feed forward zero cutoff frequency mentioned in table 1. As datasheet suggests, optimum value should still be verified with transient tests to ensure adequate stability margin.

    Kind Regards,

    Liaqat

  • 0 in reply to Liaqat Khan
    Guru 27585 points

    Liaqat san

    Thank you so much for your reply!

    We would like to confirm one point.

    To have a higher phase margin, the design should target cross over frequency that is less than feed forward zero cutoff frequency mentioned in table 1.
    ->The customer's condition is as follow;
       -Vi=5V, L=4.7uF, Cout=22.1uF

    FEED-FORWARD ZERO CUT-OFF FREQUENCY : 11.2kHz which shows on the tabel1.
    Fc=1/2π√LC=15616Hz=15.6kHz

    Thereforre, Fc > FEED-FORWARD ZERO CUT-OFF FREQUENCY, should we increase Cout to inprove the phase margin?
    And how much is "a higher phase margin"? More than 45degrees?

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Mastermind 18550 points

    Hello Matsumoto-san,

    Yes, increasing the output capacitor value will help improve the phase margin. You can use a 2x22uF instead of one capacitor. I cannot answer how much the phase margin will be but it can possibly be greater than 45 degree. You will need to measure it in the application.

    Kind Regards,

    Liaqat