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SN74AVC4T245: Hotswap level-1 related questions

Kazuhiko Hirano
Genius 11613 points
Part Number: SN74AVC4T245

Hello,

My customer would like to achieve hot-swap level-1 at their application.
This means that they can accept data corruptions during hot-insertion/removal, but can not accept device damages.
My customer has some questions as follows.

Q1:
My customer thinks SN74AVC4T245 is hot-swap level-1 device. Though the following app note states a “the host system must suspend signaling during daughter-card insertion or removal at level-1 isolation, does host really have to suspend signaling during the insertion or removal to prevent device damages? How SN74AVC4T245 could be damaged if the host system does not suspend the signaling during the insertion or removal? https://www.ti.com/lit/an/scea026/scea026.pdf?ts=1672555633359

Q2:
When SN74AVC4T245 is used at host side, not daughter card side inserted or removed, are there anything customers should care about?

Best regards,

  • 0
    Guru 243910 points

    1. Correct. The disturbances caused by the insertion can influence any currently active signals, but not damage the devices. (AVC I/Os are overvoltage tolerant.)

    2. The host device is not powered off. But it accepts the same voltages at all times, so there is no difference.

    Please note that that app note talks about buses with multiple devices. If you have a point-to-point connection, then there are fewer considerations that you have to care about.

  • 0 in reply to Clemens Ladisch
    TI__Genius 11613 points

    Clemens,

    Thank you for your responses.
    For Q2, when customer uses SN74AVC4T245 at host side where Vcc is always on, what exactly they have to do to prevent SN74AVC4T245 damage by hot removal/insert of a daughter card?

    Best regards,

    K.Hirano

  • +1 in reply to Kazuhiko Hirano
    Guru 243910 points

    Nothing needs to be done; the absolute maximum ratings have the same limits for power-on and power-off states. (It's actually different for the output voltage, but VCC + 0.5 V is the same overshoot as GND − 0.5 V.)