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TXS0206AEVM: TXS0206AEVM need pull-up resistor

Conor
Guru 12175 points
Part Number: TXS0206AEVM
Other Parts Discussed in Thread: TXS0206, AM5728, TXS0206A, SN74LVC1T45, SN74LXC1T45, 2N7001T, TXU0101

Hi, 

We are evaluating with TXS0206AEVM. But it's not working properly and I'm in trouble.

When the TXS0206AEVM is enabled, the A port remains LO and the B port stays HIGH (excluding CD/WP).

 - Will the signal line between the CPU and the TXS0206 require damping or a pull-up resistor? Also, do we need damping or pull-up resistors on the signal line between the TXS0206 and the SD card?

 - If you have any idea what the cause is, please let me know.

Thanks,

Astro

  • 0
    TI__Guru 51526 points

    Hi Astro,

    Please note that the TXS devices have little to no drive strength and would suggest double confirming the driver used in the application can drive the signal high.

    You will need damping resistors if you have transmission line effects. However, it seems you want to pull the line high, and would be needing pull-up resistors at the input instead(the pull-up resistor at the output would be needed if you want a high voltage while the device is disabled or powered off).

    Also note that the TXS devices have internal pull-ups. Hence, see Effects of pullup and pulldown resistors on TXS and TXB devices, thanks.

    Best Regards,

    Michael.

  • 0 in reply to Michael Ikwuyum
    Guru 12175 points

    Hi, Michael

    We are considering inserting TXS0206A due to the influence of wiring length for communication between AM5728 and SD card.

    Currently, communication is possible up to SDR25, but I would like them to support up to SDR50 (48Mbps, 96MHz clock).

    ■ Since the TXS0206A only supports clocks up to 60MHz, we are considering placing an external logic IC in the clock part. Do you have any concerns or recommended logic ICs?

    ■ If there is any other solution, please let me know.

    Thanks,

    Astro

  • 0 in reply to Conor
    Guru 317210 points

    For the clock signal, you could use any fixed-direction or direction-controlled level shifter, e.g., TXU0101, 2N7001T, or SN74LXC1T45/SN74LVC1T45.

    Anyway, the TXS has edge accelerators, but otherwise it is a passive switch and has no DC drive strength. It does not buffer the signals. (Bidirectional buffers work only for very slow protocols like I²C.) As far as I know, the only solution for SD-card signals over a long wire is to replace it with a shorter wire.