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TPA6120A2: Single Supply Questions

Peter Campbell
Prodigy 100 points
Part Number: TPA6120A2

I’m using this on a single 30V supply and am seeing considerable DC offset at the output when referencing the input to mid rail (15V). On the EVM, I biased the xIN+ pins to 15V with 20k resistors initially, but found reducing these to 5k helped considerably. Any comments on DC offset with regards to single supply operation would be appreciated.

Additionally, on the product we're developing, we are using the VQFN package. I cannot get it to output anything below the mid rail reference of 15V. Aside from the package change, the circuit appears identical to our EVM.

  • 0
    TI__Guru** 109825 points
    Hi Peter,

    Welcome to e2e.
    It is recommended to use TPA6120A2 in a split supply connection. This device is not enhanced in offset at the output.
    Could you share your schematic? Are you biasing the positive inputs only?
    What do you mean by output anything below the mid rail reference? Isn't the signal variating above and below mid-rail reference? You should use series capacitors at the output to remove the mid-rial bias.
    You can send your schematic to my address ivan.salazar@ti.com if you don't want to share it on the forum.

    Best regards,
    -Ivan Salazar
    Texas Instruments
  • 0 in reply to Ivan Salazar
    Prodigy 100 points
    Ivan,

    Thank you for the information regarding offset pertaining to single supply operation.

    Schematic has been emailed. All inputs are biased to midrail. The signal is varying above the midrail reference but not below. Output capacitors are being used.

    Peter
  • 0 in reply to Ivan Salazar
    Prodigy 100 points
    Ivan,

    Did you receive the schematic? I have compared the eval board (which works) and our latest hardware (which doesn't). The DC bias points match on every pin. Also, we included the VQFN part on 2 completely different PCBs and they both behave the same (don't work). I know split supply mode is recommended, but is there something about the VQFN package that would prevent it from working in single supply mode, unlike the HSOP package which does?

    Peter
  • 0 in reply to Ivan Salazar
    Prodigy 100 points

    Ivan,

    I have now modified our board to support dual +/-14.5V supplies and the issue persists. I have e-mailed you the updated schematic which reflects this as well as a waveform showing the problem. Do you see any issues with the schematic? Again, this is not an issue with the HSOP package, just the VQFN in our experience.

    Regards,

    Peter

  • 0
    Prodigy 100 points

    Ivan,

    Regarding the clipping issue, I have identified the problem and it's not associated with the 6120. Thanks for your help.

    Peter