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TAS5706A Mono BTL Output + Stereo headphones

Andy Lucas
Prodigy 40 points
Other Parts Discussed in Thread: TAS5706A

Hello,

I wish to run the TAS5706A in a mono configuration - in other words, I only want to output on OUT_A and OUT_B in BTL configuration. However, I also wish to be able to output to headphones in stereo. 

If this is possible, should OUT_C and OUT_D and their corresponding power and ground pins be floated on the PCB design? Can this channel be disable in software via I2C?

Many thanks,

Andrew

  • 0
    TI__Genius 9670 points

    Andy,

    Yes you can configure this device in mono BTL using only outputs A and B.  See setup below.

    Do the following to disable the unused channel (OUT_C and OUT_D):

    1.  Connect PVCC_x to power, and PGND_x to power ground.  All power and grounds must be connected as usual, but decoupling caps are not necessary on the unused channels. 
    2. Leave the output pins floating on the unused channels.
    3. No decoupling cap on VCLAMP_CD is necessary. 
    4. No boostrap cap on unused channels, IF the inputs to the unused channels are ground internally (see next step).
    5. To ground channel C and D internally, use register 0x20 and 0x25.  (Only possible using one input source, SDIN1L)
      Ground input channel 4 - register 0x20 - b[D10, D8] = 110.b
      Route channel 4 to outputs C and D - 0x25 - b[D31,D28] = 0011.b

    In summary,

    1. Channel 1 = SDIN1L output BTL+ on OUT_A, and output on HPL
    2. Channel 2 = SDIN1R output on HPR
    3. Channel 3 = BTL- of channel 1 to OUT_B
    4. Channel 4 = Ground output on OUT_C and OUT_D

     In your system, do the headphones and loudspeaker use the same audio source? If not we may need to try something else. 

    Thanks,
    Brian

  • 0 in reply to Brian Burk
    Prodigy 40 points

    Thanks Brian,

    That's exactly what I needed to know. I'll only be using one audio source so that should work fine.

    Just to clarify: 

    • VCLAMP_CD should be left floating?
    • BST_C and BST_D should also be left floating?

    Thanks,
    Andy

  • 0 in reply to Andy Lucas
    TI__Genius 9670 points

    Andy,

    Correct,

    1) VCLAMP_CD should be left floating.

    2) BST_C and BST_D should be left floating, only if you ground outputs C and D internally using register settings outlined in the previous post.  (The high side FET needs to be off.)

    Thanks,
    Brian