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SN74AVC8T245: Power Sequence

user6235192
Prodigy 65 points
Part Number: SN74AVC8T245

Hello,

Please tell me about the following.　I would appreciate it if you could give me an answer as soon as possible.

・Does the SN74AVC8T245 have power sequence requirements?　Please tell me if there is.

・What kind of problems can be expected when the OE pin is connected to GND while VCCA is on？

・If both the power supply VCCA and VCCB are 0V, is it okay if a signal enters the OE, A port, or B port ?　Will there be unexpected logical values or failures ?

・I would like to know if there is no problem even if only VCCA is powered on for a long time. There is no sequence requirement, but will only VCCA fail if the power is on for a long time?

・Is it possible to switch directions dynamically? Please tell me the procedure if possible.

Best regards,

  • 0
    TI__Mastermind 45795 points

    Hi,

    There are no power sequencing requirements. GND can be applied to the OE pin with no issue. While both supplies are off it is okay to apply signals to the A/B port and OE input. Powering on VCCA while VCCB is off is fine as long as it is in the recommended supply range. You can dynamically change the direction, the best way to do it is to disable the device using the OE pin, then change the state of the Dir and re-enable the device using the OE pin. Make sure to take into account the delay times which can be found in the switching characteristics tables in the data sheet.

  • 0 in reply to Dylan Hubbard
    Prodigy 65 points

    Hello,

    Please ask again about the answers below.

    If the OE pin is fixed to GND before VCCA ramps up, does SN74AVC8T245 output unexpected logic from A port to port B during VCCA ramps up?

    > GND can be applied to the OE pin with no issue. 

  • 0 in reply to user6235192
    TI__Guru* 97046 points

    Hello,

    No, the device will not output "unexpected logic" during the power ramp. Please see this application report for details, and take note that the device shown in the report has an internal OE which is permanently enabled (the same as what you are describing): https://www.ti.com/lit/scea058