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TPA2010D1: Connecting single ended load to output

Phil Wise
Prodigy 190 points
Part Number: TPA2010D1
Other Parts Discussed in Thread: TPA6204A1, TPA6211A1

I need to interface to a device/product that uses a TPA2010D1 as the audio amp which feeds connections to the outside world.  I cannot change that.  The + and - outputs are available to me directly (no speaker or other load is connected).  I do not want, and do not need all of the power this output can provide, rather I need to essentially just tap off of it a small level to feed some other audio processing circuitry and I would REALLY like to connect to just one side (prefer the minus side).  I realize that at a minimum I will probably need a blocking cap but what else should I be concerned about?  Do I need to load the unused side (plus) with a similar load as my connection on the minus side?

Thanks,

Phil

  • 0
    TI__Mastermind 20085 points
    Hi Phil,

    This device is not a good choice for a single-ended operation because it won't reproduce all the output signal due to it uses BD modulation.
    I suggest considering the TPA6211A1 and TPA6204A1. They can be used in a single-ended output.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer
  • 0 in reply to José Luis
    Prodigy 190 points
    Thank you for the response but changing the device is not an option. I have to interface to it since is it already and existing, fielded product. I do not need the full output power. I just don't want to do anything that might destabilize it if I try to connect to just one side of the output.
  • 0 in reply to Phil Wise
    TI__Mastermind 20085 points
    Hi Phil,

    As I mentioned this device is not designed for a single-ended output.
    I am not sure which will be the device behavior under this condition. But the device won't work properly if you use it like this.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer
  • 0 in reply to Phil Wise
    TI__Mastermind 20085 points
    Hi Phil,

    Could you give me an update?
    As I mentioned this device is not a good candidate to work with a single-ended output.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer
  • 0 in reply to José Luis
    Prodigy 190 points
    I realize it is not a good candidate for a single ended output (i.e. driving a single ended earphone). But I still want to see if I can exploit some facet of the device to pull a usable single ended output from it. I can make my downstream/connected circuitry be whatever Z is needed and whatever gain is needed. It will most likely feed into an OP amp of some sort (whatever I decide), and I can deal with almost any audio level as long as the fidelity is reasonable after any appropriate filtering is applied (my audio band is only about 100 - 4KHz).

    While I appreciate the response, I did not see you give enough details as to why if would not work for my purposes so I ordered a demo board to try some things with. To rephrase my original question.......what could make the device's output unstable and what is that failure mode so that I might come up with ideas to mitigate the problem?

    To reiterate...... I have to connect to this device, changing it is not an option. And, I am only allowed to connect to one it's two outputs (+ or -).

    Regards,
    Phil
  • 0 in reply to Phil Wise
    TI__Mastermind 20085 points
    Hi Phil,

    This device is BD modulation, so it means that the outputs are not the inverse of each other and it will not play all the signal if you just use one output. This device is designed for speakers and it is not used for headphone. My recommendation would be to change the device for one designed for headphones.
    If the quality and fidelity are not important, so this configuration could work.
    Could you provide me additional information from your application?

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer
  • 0 in reply to José Luis
    Prodigy 190 points

    Jose,

    I'm designing an audio accessory product that connects to a handheld two-way voice radio which is produced by another manufacturer.  That radio is in production and there are many already fielded.  The only connection point on this radio for audio accessories has only one option for pulling off audio.  The mfr. told me that they use this TPA2010D1 IC circuit to directly drive the + and - audio output pins on this connection.  So, you see, there is no option at all to change this configuration.

    I realize that perhaps the simplest option is to transformer couple this connection in order to convert to single ended audio but that is not really an option either in this case, due to other factors.  I may have the option to connect to both + and- pins to, perhaps, apply some sort of termination scheme but I can't use both signals for capturing processable audio.

    I just need a method for getting a reasonably clean voice audio signal from (preferably) the minus output.  After which I can post process that audio for my downstream needs.

    Regards,

    Phil

  • 0 in reply to Phil Wise
    TI__Mastermind 20085 points
    Hi Phil,

    If you can't modify or add anything, so it will be very difficult to solve this. You can try with the single-ended output, but the device's behavior won't be suitable.
    Please let me know once you do the test and let me know your results.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer
  • 0 in reply to José Luis
    Prodigy 190 points

    Jose,

    I actually found app note SLAA701A to be pretty helpful.  Using that and some experimentation on the bench, I believe that I have a solution which will give me what I need for my particular application.  In the end, it looks like I can pull a signal from just one side of the output.  I just need to apply a bit of filtering.

    Regards,

    Phil

  • 0 in reply to Phil Wise
    TI__Mastermind 20085 points
    Hi Phil,

    Keep in mind that this app note was performed for TPA31xx and TPA32xx families. These families have devices with AD modulation and BD modulation. The devices with AD modulation can be connected with single-ended output.
    As I mentioned the TPA20xx just has devices with BD modulation.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer