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Suggestions for USB PD and USB Audio to source the SmartAmp TAS5768M

Benjamin Brammer
Intellectual 460 points
Other Parts Discussed in Thread: TMS320C5533, TLV320AIC3256, TAS5768M, TPS65981, TPS65981EVM, TPS25810, TPS6598X-CONFIG, DP-EXPANSION-EVM

Hi Guys,

I already asked my question in the Audio Forum and got some pleasing answers from Roy Hsu. He suggested, that I ask my question, regarding the USB path here again. So here's my question:

I want to build myself a little stereo Soundbar with the TAS5768M as a Poweramp. Since I only want everything handled with one USB-C or USB-Typ A connector (power delivery and audio stream) I am searching for suitable solutions from TI.

I think the best approach would be a USB PD chip capable of handling the apropriate power role depending on the source (PC or Laptop) and checking wether to use 5V@3A or greater. After the negotiation the chip should release the data lines so that an USB audio chip or Microcontroller can handle the USB audio device class recognition so i can use the soundbar as an audio device for my audio output on PC. I am not sure if I can mix a USB PD chip with an USB audio chip (USB 2.0), thats why I ask if someone has some suggestions for me how to realize my little project.

Thanks for your help and suggestions.

best regards

Benjamin

  • 0
    TI__Mastermind 25895 points

    Hi Benjamin,

    Check out this reference design and let me know what you think www.ti.com/.../TIDA-00090
    "Power, control, and streaming audio data provided through USB – no other ports needed" sounds like what you are going for. It doesn't use an audio amp like the 5768, but I understand Roy helped you with that part of the design. Hopefully this can give more insight on the USB side of things.

    If you need more functionality a DSP like TMS320C5533 might also be something to look into. If you need more help with that we may need to get someone from the processing team involved in the discussion, however, as I am still part of TI Audio and not very familiar with those devices.

    Regards,

    Alex

  • 0 in reply to Alex Bhandari-Young
    Intellectual 460 points
    Hey Alex,
    thanks for your response and the suggestion. The TLV320AIC3256 has more capabilities than I need but lacks one big requirement of my project:

    I want to source the power for the loudspeaker amp (TAS5768M) from the USB Port. Since with USB PD I have the chance to source up to 100W and higher Vbus Voltages I want to implement a USB PD solution for my PMM. And even if I used only USB 3.x, I have the chance to sink up to 3A with USB-C . I think I will need at least 15W of power capability.
    I don't know if the TPS65981 would be a good starting point. But this controller has also far more features than I need.

    best regards

    Benjamin
  • 0 in reply to Benjamin Brammer
    TI__Mastermind 25895 points
    Hi Ben,

    I pinged the USB team and hopefully they can jump in to provide some more insight on the USB specific questions and appropriate chips to use. Was my link to the reference design helpful?

    Regards,

    Alex
  • 0 in reply to Alex Bhandari-Young
    TI__Expert 3625 points

    Hi Benjamin,

    If you are not doing USB PD then the TUSB32x or TPS25810 devices could be a good fit for your application. If on the other hand you do want to enable USB PD then the TPS6598x family of products are a great fit. I would recommend the TPS65981 primarily for its Evaluation Module, the TPS65981EVM, is a great tool to evaluate the full capabilities of USB PD and it comes with a built-in FTDI break-off board for easy SPI/I2C debug and FW updates. Plus this break-off board can be used in conjunction with the rest of the TPS6598x EVM family.

    What sets the TPS6598x family apart from other USB Power Delivery controllers is that these chipsets fully implement the Power Path. With the TPS65981 we integrate in FET paths for 20V 3A source/sink power path, 5V 3A source path and 5V 600 mA VCONN path (used for active cables). So 60W can be achieved internally to device with NFET driver options for an extra power path to enable whatever power you wish although the typical use case is the 20V 5A (100W) FET path. Additionally, we integrate reverse current protection, over-current protection, over-voltage protection, under-voltage protection and thermal shutdown protection for our power path.

    For setting data role, power role, mux control and more, we utilize the TPS6598X-CONFIG tool where you can configure the PD controller to operate how you wish it to.

    Regards,

    Karl

  • 0 in reply to Alex Bhandari-Young
    Intellectual 460 points
    Hey Alex,
    yes your link was helpful and showed me some other possibilities but I don't need that kind of codec, since the TAS5768M has some built in DSP capability. I just need one USB PD controller and an USB audio codec delivering me the I2S audio stream or I'll use a microcontroller for this part. For example the STM32 have a build in USB library also with USB audio interface device class.

    best regards

    Benjamin
  • 0 in reply to Karl Fleischmann
    Intellectual 460 points
    Hey Karl,

    thanks for your answer! Now this sounds really good. I will check on that now.
    Thanks

    best regards

    Benjamin
  • 0 in reply to Karl Fleischmann
    Intellectual 460 points

    Hey Karl,

    I have now the EVM but there is one thing I am not sure about: Since I want an USB Host to recognize my custom board as an audio device (soundbar) I need to forward the USB D+/- lines to my microcontroller which then acts as an audio device. Is this even possible with the EVM? As far as I have understood I also need the DP-EXPANSION-EVM to forward the pins. But then I could attach my microcontroller and when I plug the USB-C cable of the EVM to my host computer the TPS65981EVM will negotiate the power role and release the D+/- ports so that the microcontroller can negotiate the data role, right?

    best regards

    Benjamin

  • 0 in reply to Benjamin Brammer
    TI__Genius 12990 points

    Hi Benjamin,

    The TPS6598x devices sense the CC1/CC2 lines in order to detect if an audio device is plugged in its Type-C port. This is done by pulling down on both CC lines through Ra.

    The TIDA POS can be found in the link below which might be helpful. The block diagram from this POS shows how the audio device detection for the TPS6598x works by detecting the CC lines Ra pulldown resistor on the device side. The TS5USUA224 is there to allow the negative swinging analog audio to be passed with no damage to the PHY by MUXing the correct connections according to whats connected to the Type-C port. When the TPS6598x device sees CC1/CC2 have Ra it can toggle one of its GPIOs as a MUX control for the TS5USUA224 to select the correct audio path.

    Thanks,

    Jeff

  • 0 in reply to Jeffrey Mueller
    Intellectual 460 points

    Hey Jeff,

    thanks for your fast reply. As far as I have understood right, your suggestion is about analog audio over USB-C, but this is not what I want to do. I want the TPS65981 to function as my PMM for my intended USB audio device (soundbar). But everything stays digital until I use the TAS576xM as the audio amplifier for my loudspeakers. So generally my soundbar will be plugged in via USB-C . After the power role is negotiated I know how much power I can use and program the amplifier accordignly. The USB audio device is managed via a microcontroller that suits the USB Device Class Definition for Audio Devices Rev. 1.0 . So the flow would be plug in the USB-C --> a new audio device will be recognized in my OS and then I can play audio over my soundbar---> I am happy then :)

    best regards

    Benjamin

  • 0 in reply to Benjamin Brammer
    TI__Genius 12990 points
    Hi Benjamin,

    Thanks for the info, So you would only be using the x81 only as a PD controller and do not care about data role, giving the microcontroller the task of choosing the data role via the D+/D- lines (making the D+/D- pins on the x81 unused or in Hi-Z state)?

    The PD controller can be used as a Source only port and the USB communications capable bit can be set to 0 to have no communication on the data lines between the sink. The data role and power role can also be set permanetly or can be changed with PD messaging. The source port will default as a DFP.

    Thanks
  • 0 in reply to Jeffrey Mueller
    Intellectual 460 points
    Mhh... I thought the x81 can forward the D+/- lines via the internal mux to my microcontroller. I don't know how the x81 should negotiate the connection with the USB audio device library stack on the microcontroller. So I thought power role will be negotiated and the data role is handled by the microcontroller. Or do you have a better idea?

    best regards
  • 0 in reply to Benjamin Brammer
    TI__Genius 12990 points
    Hi Benjamin

    from what I understand the internal mux will flip the lines according to cable orientation. To forward these to the MCU, you can simply wire up the pins directly. I believe the easiest way to change data role is to send a PD message on the CC line to perfrom a data role swap if needed, however I will ask my team how the x81 can negotiate the data role according to the audio device on MCU using the data lines instead of the CC lines.

    Thanks
  • 0 in reply to Jeffrey Mueller
    Intellectual 460 points
    Hi Jeff, perfect!
    thanks a lot! I must say TI has the best customer service and help for engineers !

    best regards
    Benjamin
  • 0 in reply to Benjamin Brammer
    TI__Genius 12990 points
    Hi Benjamin,

    After looking into the data role determination question I found that the PD data role is PD specific. This is supposed to match the USB2.0 host/device and DFP/UFP default connections. USB PD and USB2.0 operate indepedently of each other. The TPS6598x can be a DFP or UFP, this is to control who is talking to the PD (host/device).

    Let me know if you have any more questions!
    Thanks
  • 0 in reply to Jeffrey Mueller
    Intellectual 460 points

    Hey Jeff,

    thanks for your efforts. So this means for my use I program the PD role to an UFP (device) and then the USB 2.0 audio device stack on the microcontroller will handle the rest, when the x81 releases the D+/- lines, correct?

    best regards

    Benjamin

  • 0 in reply to Benjamin Brammer
    TI__Genius 12990 points
    Hi Benjamin,

    No problem!

    Thats correct, you program x81 to be a data DFP/UFP/DRP OR power role source/sink/DRP.

    PD negotiation has nothing to do with the data lines. the data lines are used for example in USB BC1.2 detection, USB EP for HID devices and billboarding alt mode no-entry reporting.

    Thanks