• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 64 subscribers
  • Views 1285 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.

TPS65130: Inverting converter is not regulating under load

Joseph DiPietro
Prodigy 30 points
Part Number: TPS65130

I've constructed a +-12 Volt supply using the design from the datasheet.  See schematic and board layout below:

With no load the outputs are +11.93V and -12.1V.  When I add a 560 Ohm resistive load to each output in turn they read +11.93V and ~-21V.

The voltage on pin 16 is -0.03V unloaded and +0.48V loaded.

I've replaced U6 and obtained identical results.

Any suggestions?

Thanks,

Joe D.

  • 0
    TI__Expert 6330 points
    Hi Joseph,

    I have notified our expert regarding this topic. Please expect a response by 9/13/18.

    Thanks,
    Aaron
  • 0 in reply to Aaron Goodson
    TI__Mastermind 18550 points
    Hello,
    We have noticed that in nosier board environment, it is helpful to have a series resistor of around 51K between C14 and negative inverter output to reduce noise coupling into the FBN feedback pin. Can you please add this resistor in your design to see if it resolves the issue that you are seeing? I also noticed that your schematic shows inverting converter feedback resistros R20 and R21 both as 100K ohm and these are not the correct values for the output you are setting.
    Kind Regards,
    Liaqat
  • 0 in reply to Liaqat Khan
    Prodigy 30 points
    I can certainly try your suggestion but it does not seem to be addressing the issue of the device not being in regulation.
    If you look a little closer you will find that R21 is 1M Ohm, not 100k Ohm.
  • 0 in reply to Joseph DiPietro
    TI__Mastermind 18550 points
    Hello,
    If there is noise coupling into the feedback pin FBN, this will impact device's ability regulate the voltage properly so it is relevant to add the series resistor that I recommended in the last response. My mistake and my apology in not reading the extra zero in R21.
    Let me know how adding the resistor in series with C14 to negative converter output impacts circuit behavior. Just to be sure, R21 should still be connected to VNEG pin so the added resistor should only be be in series with C14 and VNEG.

    Kind Regards,
    Liaqat
  • 0 in reply to Liaqat Khan
    Prodigy 30 points

    I tombstoned the cap and resistor on opposite sides of the cap's footprint.  Much to my surprise that fixed the problem.

    Thank you very much.

    Joe