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USB/AUDIO Switch Suggestion for switching between USB full speed D+/D- and heaphone audio signals eg TS5USBA224

Michael Raleigh
Expert 3245 points
Other Parts Discussed in Thread: TLV320AIC3204, TS5USBA224, TSU5511, TS3USBA225, TS5A22362

Hello,

We have a customer that is looking for a USB / Audio switch to allow audio output on the USB connector so need to switch between USB full speed D+/D- and the head phone out from the TLV320AIC3204.  Again the head phone out is bi-polar so was thinking about the TS5USBA224 but that has an internal 100 to 200 ohm resistor that appears to have an Imax of 10mA.  With the 3204 running at 3.3 to 3.6V on the head phone amp I am concerned that will pop the shunt resistor.  Also want to be able to potentially add headphones in parallel to the shunt resistor and with head phones that are up to 100 ohms that would significantly reduce the head phone volume.  Also found the TSU5511 which looks interesting but can't really find a reference design for it:

Thanks,

-MIchael

  • 0
    TI__Mastermind 45495 points

    Micheal,

    If you are looking to place bipolar audio signals on the USB Type C connector take a look the TIDA00565 reference design.  

    http://www.ti.com/tool/tida-00565

    Are you referencing the spec below stating the current limit through the shunt resistor is 10mA?   The 10mA spec below is the forced test condition in which the shunt resistance was measured.

    According to the abs make table the I/O pins should be able to handle up to 100mA through the switch, but I will check with design to see if there is a limitation on the shunt resistor. 

    The shunt resistor on the L/R pins is only connected when the L and R pins are not selected.  You can see this post below for more information.

    https://e2e.ti.com/support/interface/etc_interface/f/388/t/417071

      Let me know if you have further questions.

    Thank you,

    Adam

  • 0 in reply to Adam Torma
    TI__Expert 3245 points
    Hi Adam,

    Thanks for the response.

    Yes the question was specific to the 100 ohm shunt resistor. When the audio path is not selected the audio pins are connected to the shunt resistors. The only reference I see to the current for the shunt resistors is the IOshunt you highlighted that is 10mA. However the output of the headphone amp could be up to it's relative voltage which is probably going to be 3.6V which would put 36 mA through the shunt resistor. Even if it is centered around ground that would be 18mA both are larger than the IOshunt.

    Thanks,
    -Michael
  • 0 in reply to Michael Raleigh
    TI__Mastermind 45495 points
    Micheal,

    We are still evaluating this use case but we would recommend not exceeding the 10mA test condition on the shunt resistor to unsure the long term reliability of the device.

    Thank you,
    Adam
  • 0 in reply to Adam Torma
    TI__Expert 3245 points
    Hi Adam,

    Thanks for following up with this.

    What alternatives can we suggest to enable the customers solution?

    Thanks,
    Michael
  • 0 in reply to Adam Torma
    TI__Expert 3245 points
    The issue comes when the USB port is in USB mode not analog out and headphones are connected the 100ohm is effectively in parallel with the headphones and will be driven.
  • 0 in reply to Michael Raleigh
    TI__Mastermind 45495 points
    Michael,

    I think I am understanding the use case better that there are multiple ports in the system. There is port1 where the TS5USBA224 is being used to switch between USB data path and the audio codec. There is an additional headphone port2 to allow an option to have headphones plugged into port2 and have USB data transferred through port1 simultaneously. Port2 is directly connected to the codec which also connects to the TS5USBA224 causing the concern.

    The truth table on both the TS5USBA224 and TS3USBA225 do not allow a way to turn on the USB path without having the 100 ohm shunt resistors engaged on the L and R pins.

    You could try placing a switch like the TS5A22362 in between the codec and the TS5USBA224 L and R pins to place the path in a high impedance state for this use case to prevent the current to flow into the TS5USBA224 shunt resistors when the codec is driving the headphones.

    Thank you,
    Adam