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TXG1042: USB ground separation

Yu Sato
Intellectual 910 points
Part Number: TXG1042
Other Parts Discussed in Thread: TXG8122, ISOUSB111

Tool/software:

Hi team,

1: Can TXG series devices be used in USB communication? I would like to cut the ground between my application and PC to avoid ground loops and the noises caused by it. USB 2.0 Full Speed (12Mbps) is used for communication. Connection side will be powered from VBUS, and the application side will be powered by a battery.

2: Also, how should I consider the ground voltage offset between 2 battery powered devices? 

BR,

Yu

  • 0
    TI__Mastermind 22480 points

    Hello Yu,

    From my understanding, USB uses differential signaling (D+ and D-) for communication. TXG does not support differential signals.

    Regards,

    Josh 

  • 0 in reply to Joshua Salinas
    TI__Intellectual 910 points

    Hi Josh, 

    Is it because the TGX1042 is fixed directional? I do not see why differential signal would be an issue on TXG devices, since it does not require negative voltages. If the out-of-phase logic signals are inputted into the 2 channels, wouldn't the device just output the same signal?

    Would something like TXG8122 work better for a bidirectional differential signal?

    Also, could you comment on my second question as well? If neither sides are properly grounded, would there be an issue of ground offset being too large for TXG devices?

    Yu Sato said:
    2: Also, how should I consider the ground voltage offset between 2 battery powered devices? 

    BR,

    Yu

  • 0 in reply to Yu Sato
    Guru 316740 points

    The TGX requires and outputs logic signals, and each channel is unidirectional. USB signals have different electrical characteristics and are bidirectional.

    The TGX8122-Q1 is bidirectional, but I²C and USB still have entirely different electrical characteristics.

    For USB isolation, you need an isolator that understand the USB protocol, i.e., ISOUSB111.

  • 0 in reply to Yu Sato
    TI__Mastermind 22480 points

    Hello Yu,

    I would follow the layout example on how to configure two devices with different ground offsets.

    Regards,

    Josh