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SN74LVC16T245: Pull up questions

Part Number: SN74LVC16T245
Other Parts Discussed in Thread: SN74LVCH16T245

Hello,

After reading more about this part from the datasheet and this application note, I have a few clarifying questions.
http://www.ti.com/lit/an/slva746/slva746.pdf

First here are some application details:

  • The direction pin will be permanently tied to one direction.
  • The enable pin will be permanently tied high
  • The customer does not want to switch to the SN74LVCH16T245 which has bus-hold.

I was hoping you could confirm/correct these thoughts I have:

  1. No pull up resistor is needed if the input is driven from a push-pull
  2. Pull ups are needed on every input NOT driven from a push-pull
  3. Pull ups are needed on unused inputs to prevent them from oscillating and wasting power
  4. Pull ups are not needed on the outputs since they will always be outputs
  5. Figure 9 from that application note says to put pull ups on the input pins if the device is permanently enabled. Does this exclude inputs driven by a push-pull as stated in #1? 

Thank you!

Regards,
Ryan B.

    1. Yes.
    2. Yes, if you mean an open-drain driver.
    3. Yes, or a pull-down.
    4. The datasheet says:

      The input circuitry on both A and B ports always is active and must have a logic HIGH or LOW level applied to prevent excess ICC and ICCZ.

      But if the outputs are always active (OE tied low), then there are always valid logic levels at the pins.
    5. The application note says:

      This ensures proper/glitch free operation during power up.

      If you do not care about the output value during power up (when the other device with the push-pull driver is not yet active), you do not need a pull-up.