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TPA3111D1: Output DC offset specification

Alexandre Baril
Prodigy 10 points

Part Number: TPA3111D1

Hello,

I have a design in development with the TPA3111D1 where the output goes through a coupling transformer. With my first prototypes, it worked fine but a newly made prototype produced an asymmetric saturation of the transformer (resulting in distortion). When debugging, I found out that the newly made protoype has an output DC voltage offset of 10 mV while my other prototypes were around 2-3 mV. I am powering the TPA3111D at 24 V and using a gain configuration of 26 dB. 

I have two questions regarding the datasheet.

First, when I download the latest revision of the TPA3111D datasheet, dated july 216, the specification Class-D output offset voltage (measured differentially) is in mA unit ?!? I suspect the correct unit is mV right ? See attached print screen of the issue.

e9033129-99fe-4a23-889e-6703ddfcf8cc.jpgSecond, the datasheet specification Class-D output offset voltage (measured differentially) is given with test condition of Vin = 0 (so a short-circuit at the input I suppose) and Gain = 36 dB. For my gain configuration of 26 dB, can I expect a smaller range of outût offset voltage or a bigger one ? I would need this information to properly update the coupling transformer part so it can tolerate the maximum DC output offset voltage. 

Thank you for taking the time to look into my issue. 

 

  • +1
    TI__Expert 5190 points

    Hi Alexandre,

    You are correct, the "mA" is a mistake in the datasheet and the unit should be "mV", thanks for pointing that out so we can correct it.

    For a lower gain setting, I would expect a similar to smaller output offset voltage compared to a higher gain setting.

    Regards,

    Isaac

  • 0 in reply to Isaac Buliva
    Prodigy 10 points

    Just to make sure I understand this correctly, I still have to expect a maximum of 15 mV of Class-D output offset voltage (measured differentially) even if I use a gain of 26 dB right ?

  • 0 in reply to Alexandre Baril
    TI__Expert 5190 points

    Alexandre,

    I would expect this to be lower with 26dB gain, but with the absence of data for this specific case all I can say for sure is that it should not exceed 15mV. Your other prototypes that have a 2-3mV offset make more sense for an expected value, but 15mV should be considered a worst case scenario.

    Regards,

    Isaac