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SN54LVC573A: SN54LVC573A

Raheel Bari
Intellectual 575 points
Part Number: SN54LVC573A

Hello

SN54LVC573A is 5-V tolerant tolerant input which means you can apply input of 5.0V having vcc of 3.3V. I'm confused with the output voltage range in 3-state which can be 5.5V. In my application, the input voltage is 5.0V when the latch is 3-state. Does it mean that in 3-state 5.0V can appear on the output pins of latch if the input voltage is 5.0V or it means that in 3-state output pins are also 5-v tolerant regardless of the input voltage?

Regards;

  • 0
    TI__Guru 62930 points
    Raheel,
    When the output is tristated, the output can be driven (from another device) to 5V without causing damage to device. When the output is tristated, the output will be high impedance. The Absolute max spec allows this to go to 6.5V when output tristated.
    If you are concerned with the output voltage during tristate (since it is essentially floating), a small pullup or pulldown can be used to put output in known state when not being driven by device.
    If this answers your question, please click "Verify it as the answer"
    Regards,
    Wade
  • 0 in reply to Wade Vonbergen
    Intellectual 575 points

    Wade

    Thank you for the update.

    Once in tristate, will this affect other 2 to 3 peripherals who're sharing these output data pins.? I think it isn't a compulsion to pull up the pins if in high impedance.

    Regards;

  • 0 in reply to Raheel Bari
    TI__Guru 62930 points
    This is more of a concern for the downstream inputs. They may suffer oscillations if the output is left floating.
    Biasing with pullup or down is best practice.
    Floating inputs can affect device reliability.
    This app note discusses this. Note, it does not cause any issues with the outputs.
    www.ti.com/.../getliterature.tsp

    If this answers your question, please click "Verify it as the answer"
    Regards,
    Wade
  • 0 in reply to Wade Vonbergen
    Intellectual 575 points

    What do you mean by down streaming input. Do you mean the peripheral connected to the output terminal which can go tristate

  • 0 in reply to Raheel Bari
    TI__Guru 62930 points
    Yes, referring to any inputs that this output could be driving. It may leave these inputs in indeterminate state causing higher current flow. The app note above explains this.
    Regards,
    Wade
  • 0 in reply to Wade Vonbergen
    Intellectual 575 points
    Thank you.

    In my application there are 2 peripherals connected to output pins of tristate pins. In the tristate condition, One peripheral is output and second is input. if there is always one output and other is input connected to this tri state buffer output pins, do i still need to ensure pull up resistors still?

    Regards
  • 0 in reply to Raheel Bari
    Intellectual 575 points
    Thank you.

    In my application there are 2 peripherals connected to output pins of tristate pins. In the tristate condition, One peripheral is output and second is input. if there is always one output and other is input connected to this tri state buffer output pins, do i still need to ensure pull up resistors still once i put the buffer in tri state?
  • 0 in reply to Raheel Bari
    TI__Guru 62930 points
    If the signal line is always driven, without contention (two outputs driving at same time), then you will not have issue. The weak biasing will pull it to valid level if it is tristated for longer durations.
    Regards,
    Wade