• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 408 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.

TPS65100: Ringing if the device was disconnected more than 270ms and less than 500ms

Egon Hirsch
Expert 3550 points
Part Number: TPS65100

Hello all,

my customer is using our TPS65100 to supply a 7" TFT-Display. If the customer interrupt the power supply for more than 270ms and less than 500ms

our device oscillates and the power supply shows a ripple of more than 1V.

If the customer interupts the power suplly for only 100ms or longewr than 500ms than no oscillation occurs. The 7" TFT-Display needs only 10mA from the VDDA supply.

The customer changes the value of C5 to 12pF this helps a little bit. With this mortification 85% of the displays shows no ringing or oscillation.

If the customer adds an additional load to the VDDA supply of 1kOhm than the problem also no longer exists.

But in his application its not possible to generate this additional power losses.

I add the schematic from my customer. Any input from your side to overcome this oscillation are highly appreciated.

Best regards

Egon

  • 0
    TI__Expert 6330 points

    Hi,

    I have notified our expert regarding this topic. Please expect a response by 7/12/19. 

    Thanks,

    Aaron

  • 0 in reply to Aaron Goodson
    TI__Mastermind 18550 points

    Hello Egon,

    It appears that there is possibly some boost loop stability issue with this application case. The correct calculated value for C5 based on the feedback resistors used is 12pf so this is the value that should be used. I also noticed that ENR pin is enabled and since there is not feedback mechanism for the linear regulator in this application (since linear regulations components are not there), I would suggest to connect ENR pin to GND.

    After these changes are made, can you please capture scope plots of the VIN, VDDA and switch node simultaneously when this oscillation happens? These plots may provide some clue to what may be going on.

    Kind Regards,

    Liaqat

  • 0 in reply to Liaqat Khan
    TI__Mastermind 18550 points

    Hello Egon,

    Since I have not heard from you about the changes I suggested and information requested, I am going to close this thread for now. I you need further assistance, please create another thread or respond to this one.

    Kind Regards,

    Liaqat