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SN74LVCH16T245: SN74LVCH16T245 Floating Inputs / Outputs

Charles McCarthy
Intellectual 500 points
Part Number: SN74LVCH16T245

This post is related to a previous post, "SN74LVCH16T245 - How do I configure unused input and output pins?"  Like the previous answer, I believe unused inputs/outputs should both be left open.  However, the datasheet (SCES635B) states in §10.2.1:

"This device uses drivers which are enabled depending on the state of the DIR pin. The designer must know the intended flow of data and take care not to violate any of the high or low logic levels. It is important that unused data inputs not be floating, as this can cause excessive internal leakage on the input CMOS structure. Make sure to tie any unused input and output ports directly to ground."

This seems like a contradiction to your statement to leave inputs AND outputs floating.  Please clarify.

  • 0
    TI__Guru* 97046 points

    Hi Charles,

    The SN74LVCH16T245 has bus-hold circuits on all input pins (which means all I/O pins). For this particular case, the pins being disconnected does not mean they are left floating -- the bus-hold circuit will force the input to a valid level.

    Note the description section (page 3)

    The statement you are quoting is a standard blurb put into transceiver datasheets that do not have the bus-hold feature (typically). It seems that it was copied into the SN74LVCH16T245 datasheet mistakenly.

    I will make a note that we need to update that section of the datasheet.  Thanks for bringing it to our attention.