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USB Hot Plug,Damage the CPU

Y tck
Intellectual 835 points
Other Parts Discussed in Thread: TPD4S012

Hi,

In my board,USB0 is used as a host,and USB1 is used as a device.Board-A's USB0 is connected to Board-B's USB1,and,Board-B's USB0 is connected to Board-A's USB1.

Board-A USB0(host) --DP,DN--- USB1(dev)
USB1(dev) --DP,DN--- USB0(host) Board-B

The USB1(dev) power is provided by itself board, not the connected host board，which connected the two board is only DP,DN pins,ESD using a TPD4S012.

When I do a hot plug,unfortunately，the two board are all damaged,the CPU can not work any more.

Can anyone help me ?

Thanks

YanTCK

  • 0
    TI__Mastermind 27890 points

    Are you mixing the power/ground domains between the boards? From the the description it sounds as if you are. You say you have only connected DP/DN between the boards...does that mean the USB interfaces do not share a common ground at any point?

  • 0 in reply to -DK-
    Intellectual 835 points

    Hi,DK

    There are three boards in my design,Board-A,Board-B,and a Baseboard,Board-A and Board-B share a common ground from the Baseboard,also the power.That means the Baseboard provides the power and ground domains for both A and B.

    Thanks

    YanTCK

  • 0 in reply to -DK-
    Intellectual 835 points

    Additional，The TPD4S012 is broken down.

  • 0 in reply to Y tck
    TI__Mastermind 27890 points

    USB requires 90 Ohm differential impedance matching for the length of the interface, but in your design you are not routing the necessary ground reference along with the DP/DM pair so it is certain that there exists a ground potential mismatch between transmitter and receiver. This voltage/ground potential mismatch is the very likely cause of your circuit damage.

  • 0 in reply to -DK-
    Intellectual 835 points
    Hi,DK

    Thank for your suggestion，I will do a test.
    In addition,if I modify the pinmux of the USB_DP,USB_DM, to a status of "Receiver disabled" before the Hot Plug done,is it helpful ?
     
    A08h         conf_usb0_dm 
    A0Ch        conf_usb0_dp
    A20h         conf_usb1_dm 
    A24h         conf_usb1_dp
     
    0: Receiver disabled
     
    0: Pulldown selected
     
    0: Pullup/pulldown enabled


    thank you

    YanTCK
  • 0 in reply to Y tck
    TI__Guru 62855 points

    I need to confirm this, but do not think these registers exist since the USB terminals do not have pin multiplexing like many of the other IO terminals.  I will have the TRM updated after this has been confirmed.

    The USB DP/DM signals are always connected to the internal USB PHY and they only have two possible functions.  The primary function of these terminals is USB DP/DM, but the USB PHY also provides an option to connect UART signals to these terminals.  It is possible to connect UART2 signals to USB0 and UART3 signals to USB1.  However, the registers you mentioned are not used to configure this option.  Please refer to the USB GPIO Details section of the TRM for more details.

    Regards,
    Paul