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LP875701-Q1: Bode test

YEPENG ZHANG
Prodigy 85 points
Part Number: LP875701-Q1

Hi TI engineer，

   We want to test Phase Margin and Gain Margin for LP875701,  but we found there is no feedback  resistor circuit，so can you tell us how to do the BODE test ，and how to change the feedback circuit parameters

  • 0
    TI__Prodigy 530 points

    Greetings Yepeng,

    I hope you are doing well! Thank you for reaching out. The expert on this part is out of office until early next week and will get back to you as soon as possible.

    Best regards,

    John  

  • 0 in reply to John Bui
    Prodigy 85 points

    Hi John

       Thanks for you reply，I'll keep waiting

  • 0 in reply to YEPENG ZHANG
    TI__Guru* 81034 points

    Hi Yepeng,

    The expert will be back from holiday vacation tomorrow (Wednesday) and I will ask him to reply by the end of that day.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    TI__Genius 13880 points

    Good Morning Yepeng Zhang,

    The feedback network of the bucks in this PMIC are internal in this design. To obtain the measurements you would need for gain and phase margin, you would need to insert a resistor into the FB pathway. For these PMICs, we tend to rely more on step response for our stability testing so I don't have extensive insight on the Bode plot measurement technique.

    Here is another E2E thread with additional information (it is a different part, but a similar situation as the feedback network is internal to that part as well).

    And here is an application note detailing the measurement further (specifically section 4.3).

    Kind regards,

    Conner Gillette