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TAS5558

Holger Schindler
Prodigy 650 points
Other Parts Discussed in Thread: TAS5558, TAS3108

I’m using the TAS5558 PWM modulator in a Soundbar application and I’d like to use the I2S output (pins 29-31) to connect a Wireless subwoofer (via a Wireless subwoofer module with I2S input).

All registers of the TAS5558 are in default configuration, only the ASRC mode Control register (0xC5) was changed to 0x03000300 (I2S out enabled, DAP output as source  for Serial Out). There is a valid output signal (unfiltered and unaffected by volume settings), but I’d like to use audio processing capabilities of the TAS5558 for the I2S output as well. Unfortunately I didn’t found any hints in the datasheet on how to achieve this. What I want to do is:

 

  1. 1.      Use one of the 8 processing channels for the Subwoofer (low pass filter, some equalization, volume/gain setting)
  2. 2.      Feed this channel into the I2S output

 

It seems I’m on the right track with setting bits D9 & D8 in register 0xC5 to 1, but there is no hint in the datasheet which DAP channel is routed to the I2S output.

 

Thanks

Holger

  • 0
    TI__Mastermind 33420 points
    Hello Holger,Let me take a look at this and get back with you ASAP.Thanks,Tuan
  • 0 in reply to Tuan
    TI__Prodigy 105 points
    Hi Tuan

    I'm working with Holger for the customer.
    The customer asked to get feedback this week. Do you think this is doable?

    Regards
    Sven
  • 0
    TI__Mastermind 33420 points

    Hi Holger and Sven,

    The SDOUT can be used in two of the three conditions stated in section 9.2 of the data sheet (SLES273A).  Internally TAS5558 has a ROM program that allows access for certain modes.  It's flexible enough to do the things stated in the data sheet but not fully flexible to be able to re-route some of the channels for special or all types of applications.

    -For case 1, inputs from SDIN1-4 are used to create Dolby down-mix output to SDOUT and is controlled in register 0x04 bit D0.  Since SDOUT pin is a dual function pin (SDIN5) and SDIN5 is the default setting, SDOUT must also be enabled in register 0xC5 bit D16.  The SDOUT Dobly coefficients are described in section 11.46

    -For case 2, SDOUT is not supported

    -For case 3, SDOUT can be routed to external audio processor with I2S input (TAS3108), and then re-routed back to TAS5558 for PWM output.  This mode was created specifically to work with TAS3108 since it does not have ASRC.

    For the application that you described above, it seems that you can use case 1, but then you have to route SDIN4 to either SDIN1 or SDIN2 since only these two can be routed to SDOUT.

    Hope this helps.

    Thanks,

    Tuan

  • 0 in reply to Tuan
    Prodigy 95 points
    Dear Tuan,

    is there any way to route the signal through the processing block first (including biquads, master volume and DRC) and then to the I2S SDOUT?

    Regards,
    Daniel
  • 0 in reply to Daniel Konrad
    TI__Mastermind 33420 points

    Hi Daniel,

    I wish I could say yes.  Since SDOUT was design for either pass through (stereo with no processing) or subwoofer channel (downmix), the signal path for it doesn't go through the biquads, DRC, etc.

    Regards,

    Tuan