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SN74LV541A: Have Hysteresis on SN74LV541A, and why exist "input transition raise or fall rate"?

Motoyasu Hattori
Genius 9165 points
Part Number: SN74LV541A
Other Parts Discussed in Thread: SN74HCS244-Q1, SN74LV8151

Hi,

SN74LV541A has the Hysteresis.  Is it correct?  Please advise us.

If yes, Why does SN74LV541A "input transition rise or fall rate" define on the datasheet P.5?   If SN74LV541A has Hysteresis.  I think there is no need of this spec.  Please advise us.

Thanks and best regards,
M.HATTORI.

  • 0
    TI__Mastermind 43570 points

    Hi Motoyasu,

    If the device does have hysteresis, you would see the spec below in data sheet:

    What exactly is leading you to believe this device has hysteresis? 

  • 0 in reply to Dylan Hubbard
    TI__Genius 9165 points

     

    Hi,
    I found the following sentence on old standard logic status report 2011 in Japanese. 

    The LV series has a hysteresis characteristic of about 400 mV (at VCC = 3.3 V) at the input.

    Please let me know your comments.

    Thanks and best regards,
    M.HATTORI.

  • 0 in reply to Motoyasu Hattori
    Guru 261450 points

    Leadframe and bond wires add parasitic resistance and inductance, which slow down even fast signal edges, and cause ground bounce.

    So to increase the noise margin around the switching threshold, the inputs of many CMOS logic families have a small amount of hysteresis (100 mV to 400 mV).

    This hysteresis is not large enough that it would be possible to guarantee an useable amount as an electrical characteristic. Neither is it large enough to allow slow signals.

    Devices with Schmitt-trigger inputs have larger hysteresis, and are designed to handle the cross currents that happen for slow signals.

  • 0 in reply to Clemens Ladisch
    TI__Genius 9165 points

    Ladisch-san,

    Thank you for your reply.  I understand your comments.

    I have one more questions.   Please let us know "ICs of same LV541A function and large account of hysteresis?

    Thanks and best regards,
    M.HATTORI

  • 0 in reply to Motoyasu Hattori
    Guru 261450 points

    There is no pin-to-pin replacement.

    The only 8-bit buffer with Schmitt-trigger inputs is the SN74HCS244-Q1. If you want inputs and outputs on opposite sides of the package, use the SN74LV8151.