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SN74LVC14A: On the use of the product SN74LVC14A in 24MHz crystal oscillator

FRANK1
Expert 7835 points
Part Number: SN74LVC14A

Hi Sir，

A customer has a query on the SN74LVC14A use.
In our company's products, as shown in the attached picture.
I want to connect SN74LVC14A with 24MHz crystal oscillator output and its peripheral circuits.
But the worry is can it be used on this frequency?
Just a simple comparison of rise time and fall time.
One cycle of 24MHz is 41.67ns
The maximum tpd of the above products is 6.2ns (– 40 ~ + 85 ℃)
I think there should be no problem with it.
However, if there are other matters needing attention, parameters, etc,
I wanna get your advice.

The final evaluation is implemented by our company,
It would be great if I could hear your above opinion.
Thank you for your clarification.


Regards,

  • 0
    Guru 243180 points

    This is OK, if the oscillator outputs a proper logic signal (and not a sine wave).

    What are the characteristics of the oscillator's output?

  • +1
    TI__Guru* 96591 points

    In general, the LVC family can operate up to about 100 MHz without any issues, so the speed you've listed is fine. As long as the input signal exceeds VT+(max) for and VT-(min).

    -

    I wanted to also bring up a recommended improvement to the frequency divider circuit being used with the LVC74.

    From the timing requirements table of the device:

    Note that the hold time is 1ns, which means that the data input needs to be held for at least 1ns in the previous state after the clock pulse occurs.

    As it is shown above, the circuit will probably be fine, however I would recommend a simple addition to ensure reliable operation under all conditions.

    Just adding a resistor, typically 100 ohm, will add sufficient delay (using the input capacitance for an RC circuit).