• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 616 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.

TPS65131: TPS65131 VNEG output -6V output ripple

Jimmy Huang22
Expert 1470 points
Part Number: TPS65131

Hi ti team,

     input 5V,output 6V/50ma,-6V/50mA for LCD, then test output find -6V output ripple is too high,SCH,PCB and output ripple as below

Could you pls help if there is anyting we can do to improve? thanks!

  • 0
    TI__Expert 6330 points
    Hi,

    I have notified our expert regarding this topic. Please expect a response by 3/20/19.

    Thanks,
    Aaron
  • 0
    TI__Mastermind 18550 points
    Hello Jimmy,
    Based on the values used for R26 and R18 in your schematics, I have calculated the values of the feed-forward capacitor C38=75pF and C17=68pF (please see datasheet equations for calculations). So I would suggest to adjust these values. In addition to these value adjustment, I also recommend to use a resistor of 51.1K ohm in series with capacitor C38 (between C38 and VDDN_-6V net). This normally helps to reduce noise coupling into FBN pin and improves stability. Hopefully these changes will resolve the high ripple you are seeing but if you continue to see issues, please write back with your observation after implementing these changes.

    Kind Regards,
    Liaqat