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TAS5717 PBTL mode

Mark Trainer
Prodigy 240 points
Other Parts Discussed in Thread: TAS5717, TAS5719, TAS5727

any negative consequences in using the TAS5717 or TAS5719 as a mono amp in parallel mode? I will be driving a 6ohm impedance. I read in another post that it was "ok" as long as the wiring is done after the LP filters. (http://e2e.ti.com/support/amplifiers/audio_amplifiers/f/6/t/335259)

 

Are there any "optimized" settings for the PWM output timing variables for PBTL mode?

 

  • 0
    TI__Guru 57800 points

    Hello Max,

    Almost all TAS57xx devices can be implemented in PBTL. In the case of TAS5717/19, effectively the wiring between the outputs should be done after the LC filter. Newer devices like TAS5727 supports single filter PBTL mode.

    You need to take care of how the PWM channel configuration is set in registers 0x19 and 0x25.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Prodigy 240 points

    Thanks Diego-

    With respect to register 0x19

    I suspect the goal will be to link all PWM outputs to the shutdown group 0b00111111=0x3F since in PBTL will all outputs will be singing the same song versus the spec's suggestion of 0x3A??

     

    Also, what is the meaning of Channel 3 and Channel 4, from my understanding these are the parallel channel for DRC2, correct?

     

    With respect to 0x25

    Any difference in:

    (a)  processing only one channel (say channel 1) then paralleling the OUT_A with OUT_C and OUT_B with OUT_D

    vs

    (b) processing two (mono) channels (channel 1 and channel 2) then mux-ing OUT_A/OUT_B with channel 1 and OUT_C/OUT_D with channel 2

     

     

  • 0 in reply to Mark Trainer
    TI__Guru 57800 points

    Hello Mark, 

    Before answering I'd like to point something. Each PWM is derived from the two audio channels as follows:

    In BTL mode, the combinations for each audio pair should be PWM1 and PWM3   or   PWM2 and PWM4. 

    Regarding register 0x19:

    Writing '1' means not powering up the selected PWM channel when exiting shutdown. 0x3A is recommended as only one audio channel is required for PBTL. With 0x3A, Channel 1 is used as the audio source. By setting register 0x19 with 0x3F, you will be shutting down all the PWM channels.

     Regarding register 0x25:

    A typical configuration for PBTL will be connecting OUT_A with OUT_B and OUT_C with OUT_D. If register 0x19 is set with a value of 0x3A, then Audio Channel 1 is used. So register 0x025 must be set with a value of:

    0x01 00 22  45

    Where PWM1 is multiplexed to OUT_A and OUT_B,  and PWM3 is multiplexed to OUT_D and OUT_D

    Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Prodigy 240 points

    thanks again for the insight, especially for register 0x19

    In case others are reading, I'll state the following:

     

    What I have is a stereo/mono configuration working with the following settings (with a schematic similar to the demo board):

    • stereo mode: OUT_A/OUT_B is LEFT (Ch1) and OUT_C/OUT_D is RIGHT (Ch2)

     

    register 0x25 = 0x01021345

     

    • mono mode: In HW, I wire in parallel (after the LP filter) and in SW set OUT_A/OUT_C to Channel1 and OUT_B/OUT_D to ~Channel1

    register 0x25 = 0x01020245

     

    thanks,

    M