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SN74LS31: What is the minimum pulse width and the maximum frequency which can be input to SN74LS31?

Kazuya Nakai59
Guru 20450 points
Part Number: SN74LS31

 Hello guys,

 One of my customers is considering using SN74LS31. They have the following questions. Could you please tell me your answers or comments for the questions?

Q1. What is the minimum pulse width of high and low level input signal?

Q2. What is the maximum frequency of input signals?

Q3. Do you have any graph of propagation delay (tpd) characteristics graph with the following conditions?

      (1) tpd vs temperature (VCC=5V)

      (2) tpd vs CL (load capacitance) (VCC=5V)

      (3) tpd vs RL (load resistance) (VCC=5V)

      (4) tpd vs VCC

 Your reply would be much appreciated.

 Best regards,

 Kazuya Nakai.

  • 0
    TI__Guru* 96681 points
    Hello Nakai-san,
    The data you have requested could possibly have been taken when the device was characterized, however that was about 50 years ago, and I don't have access to that data.

    Based on the three questions I have seen from you today, it sounds like your customer is trying to find a device with very well characterized propagation delays. I see that they are operating at 5V supply, but you have provided no other data for me to try to help you with.

    Do you know exactly how much delay they are trying to get?

    How much change in delay is acceptable?

    What is their operating temperature range?

    An even more important question is: what are they trying to accomplish in their system?
  • 0 in reply to Emrys Maier
    Guru 20450 points
    Hello Emrys,

    Thank you very much for your reply. I understood. The customer wanted to get those data for just reference if TI has the data.
    But could you please answer me for the following question?

    Q. Is SN74LS31 input signal maximum frequency 35MHz? Because we can see "F @ Nom Voltage (Max) (Mhz) | 35" on the parametrics table in the device TI WEB page (URL: www.ti.com/.../SN74LS31

    Thank you very much again and best regards,
    Kazuya Nakai.
  • 0 in reply to Kazuya Nakai59
    TI__Guru* 96681 points
    Hello Nakai-san,
    The device doesn't have a rated maximum frequency since it is not a clocked device. The "F @ Nom Voltage 9Max) (MHz)" value provided on the website is an estimated maximum frequency of operation (square wave input) based on the technology family.