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Original question:

TPS65130: Problems with the output voltages (Both positive and negative)

TPS65130: Incorrect Negative Output on Evaluation Board

Matthew Anauo
Prodigy 110 points
Part Number: TPS65130
Other Parts Discussed in Thread: , TPS65131

Hi,

I purchased the TPS65130 evaluation board (TPS65130EVM-839) for testing. The end application will be generating +/-12V rails from a 3.3V supply, with an expected load of ~50mA.

I modified the evaluation board feedback resistors to adjust the output voltages, but the negative rail is not working correctly. The positive rail is steady at 11.93V, as expected, but the negative rail is stuck around -0.1V.

The following components were changed:

  • R4: 162kΩ → 100kΩ.
  • R2: 162kΩ → 100kΩ.
  • R5: 665kΩ → 1MΩ.

These changes should set the outputs to +/-12V according to the calculations in the applications section of the datasheet.

The voltage at the FBN pin is measuring -0.02V, and the voltage at the VREF pin is measuring 1.213V, both of which make sense. The layout can't be the issue with an eval board, and no other components have changed - has anyone resolved similar issues with this device?

  • 0
    TI__Mastermind 18550 points

    Hello,

    If these are the only changes, I would expect the voltage to be +/-12V so I am suspecting that something has gone wrong during component swap. Are you able to go back to original component values and get the original voltage that the EVM came set with?

    Kind Regards,

    Liaqat

  • 0 in reply to Liaqat Khan
    Prodigy 110 points

    After reverting to the original component values that the EVM set came with on the negative rail, the output is still only -1.1V. I measured the components that were taken off and put on the verify the resistances, and probed extensively against the schematic to verify all the correct continuities.

  • 0 in reply to Matthew Anauo
    TI__Mastermind 18550 points

    Hello Matthew,

    If you are not able to get it to work with the original components, than it appears that the board has somehow got damaged during component swap. Yo may need to get a new EVM or replace the device.

    Kind Regards,

    Liaqat

  • 0 in reply to Liaqat Khan
    Prodigy 110 points

    I understand where you're coming from, but I'm extremely skeptical that my re-soldering a single resistor irreparably damaged something in the circuit, especially seeing the number of other people that have had issues specifically with the negative output of this regulator.

    Are there any other resources you can provide, calculation reference sheets, simulation models, reference simulations, etc.? I've followed everything available in the datasheet, but it clearly isn't working.

  • 0 in reply to Matthew Anauo
    TI__Mastermind 18550 points

    Hello,

    If the EVM board was working when it came in and is not working after replacing some components in the feedback divider even after going back to the original components, I think it is reasonable to assume that something has got damaged during component swap. I would suggest to check the inverting converter diode and inductor to make sure that they are still good. If they are, then it is possible that the TPS65131 IC itself is damaged.

    I change feedback resistors on this EVM all the time to set different voltages and have never run into any issues so am not sure what else I can suggest to help in this.

    Kind Regards,

    Liaqat