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TAD5242: Pseudo-differential Output to headphone directly way

Kevin Lu
Prodigy 10 points
Part Number: TAD5242

Tool/software:

Hi team,

According to datasheet, TAD5242 can set to Pseudo-differential Output mode to drive 16 or 32Ohm headphone directly. But it just exhibited a schematic diagram in Figure 6-10. I am not quite understanding what does "External Common-Mode Sense" means. For my understanding, OUT1M works as Common mode voltage output and OUT2M as Common-mode sense input? I use red line to connect the headphone plug as showed in attached pic. Is it correct or not? Can you provide more details about "Pseudo-differential Output to headphone" connection way? And a real example of schematic is preferred.  Thanks.

  • 0
    TI__Expert 4920 points

    Hi,

    From what I understand, pseudo-differential signals are like a version of a single ended signal but with a common mode applied to both P and M sides of the signal. This can be useful for some headphones that only support a voltage range above 0, for example. The external common mode sense example schematic would be used if the sleeve of the jack already had a bias or common mode applied. In this case, the OUT2M pin would be used to measure the common mode, and the resistors placed would pull up the outputs to that common mode. If you add in a pull up resistor and connect the point at OUT1M to OUT2M, this should work for this setting. If your jack does not already have a bias voltage, you can use the preexisting common mode applied on the outputs as specified in the "DAC channel OTHER PARAMETERS" section of the datasheet, 0.9V or 1.65V depending on your AVDD.

    What are your headphone specs? Let me know any more info about your setup so I can help more.

    Best,
    Mir