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TAS6584Q1EVM: Shorted Load DC Error when Configured in PBTL

Brendan Dunn
Prodigy 20 points
Part Number: TAS6584Q1EVM


Hello,

    I've been trying to use the TAS6584Q1EVM eval kit to play audio in 2-channel PBTL mode and I seem to be having issues getting it to recognize that it's in PBTL mode. I'm able to play audio in BTL as you'd expect by connecting the positive and negative terminals of a speaker up to the positive and negative terminals of any given channel and playing audio into the device (using optical TOSlink). Setting the device into PBTL mode seems to be problematic, however. Here's a summary of my procedure:

1. I am manually shorting the + and - terminals of channel 1 and 2 with a jumper in the terminal block. This is done before device is powered



2. Turn on supplies, boot up purepath console and connect the device. Start device in PBTL mode using the GUI

2. a. I verify that the damp_ctrl register is appropriately set to PBTL mode on channels 1 & 2
3. Manually set device to deep sleep using the registers and or device and monitor control and re-verify that damp_ctrl register is set to PBTL mode and read all registers

4. Go to "Device and Monitor Control" and run a DC load diagnostics. Device reports a SL error on channels 1 and 2 (as you'd expect based on the configuration)

4.a. The PVdd supply does not draw any current -- this seems to be in contrast to a BTL mode in standby, which will draw some current when connected to a load

I've tried removing the jumpers and just connecting the speaker to every permutation of the + and - pins to connect channels 1 and 2 -- it seems that this either results in both channels detecting an OL condition, or one detects an OL condition, the other has no errors, and it's able to play what sounds like one leg of the bridge (going to scope this to verify). This seems to suggest to me that it's properly being set to play audio in a PBTL configuration, but the SL fault is preventing it from ever doing so. Is there some other register I need to set? There was a note about changing bit 4 in the DGTL_CTRL register to change the current limit for PBTL mode, but this doesn't seem to help much.

I'd appreciate any help here. Not too sure what I'd be doing different than the documentation suggests. Happy to provide photos of my setup if it would help. 

  • 0
    TI__Guru 51860 points

    Hi Brendan

       I'm sorry that the PBTL for this device is indeed a little hard to config. We have below document for the guidance, and the key point is, we need to let device initialize first, and specially enter STANDBY, only write config PBTL script, then would success. 

    TAS6584_PBTL_20221018.pptx

  • 0
    TI__Expert 5740 points

    Hi.

    When use PBTL mode, you should follow below sequence:

    And we strongly recommend using 1spw mode when set to PBTL mode. Because there will have large ground bounce at BD or Hybrid mode.

    BR.

    Wei Qiu.

  • 0 in reply to Shadow He
    Prodigy 20 points

    Thanks for the graphic -- it seems like I can now successfully play audio out of channels 1 & 2 in PBTL mode. It seems like I'm also able to set channels 3 & 4 to PBTL mode as well (by writing "w c0 04 0c") but it doesn't seem like it's able to actually play the audio I'm inputting. Any idea of why this may be? The exact behavior I'm seeing is:

    1. I enable channels 3 & 4 in PBTL mode in the same way I enable channels 1 & 2

    2. I see from the current read on my supply that it's in play mode and ready to play audio (same current draw as channels 1 & 2)

    3. I play audio and do not hear or see anything from the speaker. The current draw remains constant (unlike when channels 1 & 2 are playing audio)

    3.a. I should note that the hardware seems OK -- using the tone generator function in the app will allow the speaker to be driven. I believe channels 3 & 4 both operate as you'd expect driving them in BTL mode

    Any ideas here? Was wondering if it's maybe set up in stereo mode and it thinks my optical toslink input is just a mono signal? Haven't been able to find a setting that would correspond to this. 

  • 0 in reply to Brendan Dunn
    TI__Guru 51860 points

    Hi Brendan

      From your description, seems we not able to send in audio signal to PBTL 3&4. We need to check the Serial Audio Port, the detailed information at chapter 8.3.2, datasheet. 

      If you are using I2S signal, you need to config one of the GPIO pin to SDIN2 function, and give your audio signal to both SDIN1 and GPIO pins. The register 0x9F is used to set the GPIO pins to SDIN2

       If you are using TDM signal, the PBTL 3&4 will use the Slot 3 audio data, please make sure you have correct audio signal at Slot 3.