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TPA2016D2: Single-ended input question

Mike Molt
Prodigy 70 points
Part Number: TPA2016D2

Why does TI recommend grounding the positive left and right connections on the TPA2016 when connecting it to a single-ended audio source?

See page 31 of the datasheet: http://www.ti.com/lit/ds/symlink/tpa2016d2.pdf

In my experience the negative inputs are connect to ground for single-ended audio sources.

  • 0
    Genius 3295 points

    Hi Mike,

    The inputs on the device are differential. "Grounding" the positive input effectively turns this into a "single ended inverting input" amplifier. I didn't study the entire datasheet, however, this appears to create an inverted output. That may be corrected for in the following stages.

    Please refer to diagram 9.2 Functional Block Diagram on page 12.

    B'rgds,

    Mike Tripoli

  • 0
    TI__Mastermind 20085 points
    Hi Mike Molt,

    Welcome to E2E, thanks for your interest in our devices.
    Our class-D amplifiers with a differential input use a fully differential input stage, so it makes absolutely no difference which input you use. You can use whichever makes your layout easier.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer
  • 0 in reply to José Luis
    Prodigy 70 points

    Thanks for your reply Jose, and I'm guessing my lack of understanding is the issue here, but if you don't mind I'd like a bit more explanation.

    I will be connecting a single ended audio signal to this amplifier. This particular amplifier has differential inputs, but provides a method to connect a single ended input.

    In the single ended input scenario, one of the differential input lines is to be connected to ground. For the sake of this conversation, ground is perfectly 0V. Also for the sake of this conversation, lets say the single ended input signal has an instantaneous value of +2V.

    Depending on which of the differential inputs are connected to ground (0V), the differential output will be +2V or -2V.

    This seems like a problem unless the output is somehow automatically corrected (absolute value) by the amplifier.

  • 0 in reply to Mike Tripoli
    Prodigy 70 points
    Thank you Mike Tripoli. I'm awaiting response from someone at Ti on the "that may be corrected for in the following stages" portion of the complete answer.

    -Mike
  • 0 in reply to Mike Molt
    TI__Mastermind 20085 points
    Hi Mike,

    The TPA2016D2 is a fully differential amplifier with differential inputs and outputs and a common-mode amplifier. The fully differential amplifier ensures a differential voltage in the amplifier outputs with single-ended and differential inputs. It means that the device sets the right phase in each output.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer