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TPS65130: Part worked at first, now loading down supply from ISOW7842 , not regulating. Ringing sound

William Thompson44
Prodigy 195 points
Part Number: TPS65130
Other Parts Discussed in Thread: ISOW7842

My design incorporates the TPS65130 to provide +/-12V rails to an incoming unity gain op-amp (I am measuring input voltage up to 12V).

The part worked at first, it regulated nicely at +/-12, then after awhile it stopped working. I noticed a ringing sound (could this be the inductors?)  and my supply to the part dropped from 5V to holding steadily at 2V, and it is no longer regulating. 

Any ideas what could have happened?  What could have changed all of the sudden to load down the part? I have attached my schematic. Thanks so much for any help! 

Also to note, I am powering this chip from your guys ISOW7842 part (isolated power).

Thanks so much,

Will 

  • 0
    TI__Mastermind 18550 points

    Hello Will,

    Thank you for your post. We will look into it and get back to you by 10/18/19.

    Kind Regards,

    Liaqat

  • 0 in reply to Liaqat Khan
    Prodigy 195 points

    Thanks  Liaqat,

    -Will 

  • 0
    TI__Mastermind 18550 points

    Hello Will,

    I reviewed your schematics/layout and did not see anything particularly wrong. In the layout it is not clear but I assume there are vias connecting the exposed ground pad of TPS65130 (pin 25 in your design) to the solid ground plane on other layer(s).

    Ringing or buzzing sound is likely coming from inductors. What is the saturation current rating of the inductor? Also what is the load current on 12V and -12V output from TPS65130? I am just trying to see if the peak current in the inductor is higher than its saturation current rating which can saturate the inductor and significantly reduce its inductance.

    Also, you mentioned that input supply to TPS65130 dropped from 5V to 2V. Could it be that the input supply is not able to provide needed current for the application? What happens if you provide 5V from a bench top power supply?

    Kind Regards,

    Liaqat

  • 0 in reply to Liaqat Khan
    Prodigy 195 points

    Liaqat,

    Thanks for looking it over.

    Yes, the ground pad is connected to the gnd layer by 4 vias. 

    The saturation current for the inductors is 1.29A. The load current is minimal.. all it is doing is providing the rails to a unity gain buffer (PN LT1468) with expected load current of 3.9mA.

    I tried putting the 5V from the bench onto the circuit but was still loaded down. I increased the current limit all the way to .350A but it still hung around 2.3V. 

    Do you think I could possibly send you my schematic? Im not sure what could be going on besides a problem with the chip itself during soldering..

    Thanks 

  • 0 in reply to William Thompson44
    TI__Mastermind 18550 points

    Will,

    Saturation current rating of the inductor is definitely more than enough for your application. At this point, I suspect some board assembly issue. Is this only one board or do you have multiple assembled boards exhibiting the issue? As for schematics, you had already posted that on the forum and I reviewed it and it looks good.

    Kind Regards,

    Liaqat

  • 0 in reply to Liaqat Khan
    TI__Mastermind 18550 points

    Hello Will,

    Since I have not seen any further activity on this post in the last few days, I hope that your issue is resolved. I will close this post for now but if you have any further questions, please feel free to create a new one.

    Kind Regards,

    Liaqat