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SN74LVC8T245: Pull up and pull down requirement in SN74LVC8T245

Nidhi P Shetty
Intellectual 735 points
Part Number: SN74LVC8T245

Hello

In SN74LVC8T245 datasheet it is mentioned:The input circuitry on both A and B ports is always active and must have a logic HIGH or LOW level applied to prevent excess ICC and ICCZ.
Typical application : There are no pull up or pull down provided. Description details and typical application do not match.

Please let us know when DIR and OE pins are pulled up to VCCA do we need to provide pull up/pull down resistor to prevent excess ICC and ICCZ on port B?

Regards

Nidhi P Shetty

  • 0
    TI__Mastermind 45915 points
    Hi Nidhi,

    With the Dir pin pulled high then the B port will be an output so there won't need to be any pull-up/pull-down resistors only on A port to avoid floating inputs. On top of that, since the OE pin is pulled high, all I/Os are disabled.
  • 0 in reply to Dylan Hubbard
    Intellectual 735 points

    Hello 

    In out design 3 pins on input side are left unconnected. So how much excess Icc and Iccz will be there? 

    Regards

    Nidhi P Shetty

  • 0 in reply to Nidhi P Shetty
    TI__Guru 62240 points
    Hi Nidhi,

    With OE high, the IO ports are Hi-Z, but if the Vccx ports are still active, it is recommended to have weak pulldown resistors eg 100k on the ports.
    For eg, if OE high, Vcca high and Vccb 0V application, A ports can have pulldown and B ports can be open. If OE low, Vcca 0V, Vccb high, B ports can have pulldown and A port open.Let me know if this is clear.
    I see that you are considering many translation solutions, what are the application voltage levels? Are all this for different projects or the same project?