• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 598 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: Unstable TPS65131RGER

Fabio Soriano
Expert 4130 points
Part Number: TPS65131

Hi Team,

I received the following request:

#########################################

We have a problem with buck-boost dual converter TPS65131RGER. Our product has just started production but we could not solved it, it is very urgent.

The symptoms are below:

When the input voltage (marked as Battery_Out in the schematic) goes above 4.05V, both output stages of VR4 (TPS65131RGER) become unstable, i.e the 8V stage falls to about 3.8V and -5V stage even worse. The supply outputs are quite stable when “Battery_Out” ranges between 3V to 4.05V.

We checked the datasheet again but could not find any component value or related specification that seems wrong to cause such a behavior. 

#########################################

I will send the schematic separately.

Regards,

Fabio

  • 0
    TI__Expert 4130 points
    In addition to previous mail:
    the problem occurs only at startup (when it starts with 3.8V, then rised to 4.2V, the output stays stable).
    In our tests, we realized when the “4.7uF capacitor” connected to the Vin over a 100R resistor in the reference design is removed solves the problem, but we could not figure the reason out because the impedance from the “battery_out” supply is low enough (a LiPo battery is connected there over a simple FET channel) and have low probability to cause startup problems.
  • 0 in reply to Fabio Soriano
    TI__Expert 6330 points
    Hi,

    I have notified our expert regarding this topic. Please expect a response by 4/24/19.

    Thanks,
    Aaron
  • 0 in reply to Fabio Soriano
    TI__Mastermind 18550 points
    Hello Fabio,

    Can you please send schematics of your design so that I can check to see if I can spot something wrong? Also, can you please capture scope plot of SW node for both boost and inverting converters? Behavior of the SW node voltage can give us some clues. Feel free to e-mail this information directly to me if you prefer.

    Kind Regards,
    Liaqat Khan
  • 0 in reply to Liaqat Khan
    TI__Mastermind 18550 points
    Hello Fabio:

    Since we are discussing this over the e-mail directly, I am closing this thread.

    Kind Regards,
    Liaqat