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SN65HVD62: How to gate off TXIN and RXOUT

Doane Arnold
Intellectual 335 points
Part Number: SN65HVD62

I'm using 2 of these devices tied together to tap an AISG bus. The logic side of the chips (TXIN and RXOUT) are used to split and tap the bus. I would also like to be able to defeat the feature by turning one of the chips off. To do this, I need to switch power off to the chip and gate TXIN and RXOUT so that these inputs do not self bias the chip. Switching the power is easy, but I would like a suggestion for removing TXIN and RXOUT from the chip (logic gate or analog switch?).

Hope this makes sense.

Doane.

  • 0
    TI__Mastermind 25705 points
    Doane,
    TXIN has weak pull up reistor to VL internally and RXOUT should be high impedance with power off. I'm not very sure I understand what you mean 'self bias the chip' but I guess analog switch might do the job by disconnecting those pins from the bus.
    Regards,
  • 0 in reply to Hao L
    Intellectual 335 points

    Hao,

    Thank you for the response. I added a second SN65HVD62 to my system by connecting TXIN of one chip to RXOUT of the 2nd chip, and RXOUT of the 1st chip to TXIN of the 2nd. In addition, I had to add one 2 input AND gate to the TXIN of the 1st chip to control traffic from multiple sources. For some applications, I need to shut the second SN65HVD62 off. I used a 5V load switch to gate power to the device, but the part is receiving bias through either the TXIN or RXOUT connection (part draws current even though 5V is removed). I believe TXIN and RXOUT need to be disconnected in order for the part not to draw current. I'll try one of your dual SPST analog switches.

    Thanks, Doane

  • 0 in reply to Doane Arnold
    TI__Mastermind 25705 points

    Doane,

    From what you described, it looks like TXIN is biasing. Please let me know if the analog switches don't work here.

    Regards,

    Hao

  • 0 in reply to Hao L
    Intellectual 335 points
    Hao,
    Thank you.