• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 120 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM5175-Q1: Ripple is detected both input and output

Chase Jeong
Mastermind 7625 points
Part Number: LM5175-Q1
Other Parts Discussed in Thread: LM5175

Tool/software:

Dear TI experts,

My customer tests LM5175-Q1 in their own PCB, and they found that ripple is detected both input and output.

I think layout is something wrong, so I want you to check schematic and layout.

Just these files are confidential, so I want to send these files by private message.

Could you send me the friendship request? Then I will give schematic, layout and some test results.

Best regards,

Chase

  • 0
    TI__Guru 58641 points

    HI Chase,

    you can send this to me on private message. Just hover with the mouse over my avatar and then select send private message.

    Once done please drop a note in this thread so that i know to check my private messages.

    Best regards,

      Stefan

  • 0 in reply to Stefan Schauer
    Mastermind 7625 points

    Dear Stefan,

    Thank you for you support.

    I sent you a message, please check it.

    Best regards,

    Chase

  • 0 in reply to Chase Jeong
    TI__Guru 58641 points

    Hi Chase,

    there are a few items which should be checked first.

    - The slope compensation capacitor is much higher then recommended

    - Thermal pad of the LM5175 has thermals which will have bad thermal connection and also add inductance

    - connection of the Sense Resistor R694 is not done as Kelvin connection. This can add additional noise in the sensing signal and disturbe the regulation.

    - phase margin is only 34 Degree

    Best regards,

     Stefan

  • 0 in reply to Stefan Schauer
    TI__Guru 58641 points

    Hi Chase,

    please always drop a note in the thread - otherwise you might not get a reply for days or weeks as private message gets not checked regularly and can not be accessed by the whole apps team.

    - The slope compensation capacitor is much higher then recommended -> I will test the value as same as EVM.

    -> please do not use the value of the EVM but use the value which fits to your design based on the datasheet or quickstart calculator

    - Thermal pad of the LM5175 has thermals which will have bad thermal connection and also add inductance -> Does it mean that thermal pad of LM5175 have a bad connection to GND of PCB? and this bad connection caused additional inductance? Can I improve it through adding vias on GND pad?

    -> Vias can improve but would also use the out side layer for better thermal connection without using thermals for the thermal pad.

    - connection of the Sense Resistor R694 is not done as Kelvin connection. This can add additional noise in the sensing signal and disturb the regulation. -> I checked about Kelvin connection in google. but EVM is also not done as kelvin connection. Could you tell me why and give me ideal example for Kelvin connection?

    -> the EVM has a Kelvin connection to the shunt resistor on CS/CSB

    - phase margin is only 34 Degree -> How can I expand phase margin? Is it possible to change the values on the PCB? Or should I change PCB layout?

    -> phase margin can be adjusted by the compensation (components on the COMP pin) the quickstart calculator can help you on that

    =>  LM5175QUICKSTART-CALC — LM5175 Quick Start Calculator

    Best regards,

     Stefan