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CD74HC75PW

An Engineer
Prodigy 50 points
Other Parts Discussed in Thread: SN74LVC1G373

I'm planning on using the CD74HC75PW, but I'll only be using one of the latches (1D0, so pins 2, 16 and 1), what should I do with unused latch pins (3, 6, 7, 15, 14, 10, 11, 9 and 8)?  Should I tie them to ground?  Since I’m not using 2D0 and 2D1 should I tie 2E (pin 4) to ground or pull it high?

  • 0
    TI__Genius 9860 points

    You can tie those unused inputs to ground. The outputs can float.

    What is the end application? We have smaller latches like the SN74LVC1G373 if you do not need multiple unused inputs.

    -Ryan

  • 0 in reply to C. Ryan Land
    Prodigy 50 points

    Hi Ryan

    I had looked at the single latch options, but the OE^ line would give me problems because the purpose of the latch is to hold the run pin on a power supply in the event of a uP soft reset.  The uP would hold OE^ low (external pull up as per datasheet), release that line when it resets, the output would go tri-state so releasing the run pin of the power supply.  I can't have a pull up on the output of the latch to keep the power supply running because the run in is ORd in with a switch and would then mean that the power supply would be on all of the time.

    There is a possibility of using a reset generator to hold the line along with the latch, which I'm looking into now and would mean I could get away with the single latch package.

    Thanks for your help and advice!