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SN74LVC1G17: Logic IC Pin Specifications

SS_hwdesign
Prodigy 250 points
Part Number: SN74LVC1G17

I have a question related to >> (1) Cin, (2) Cout and (3) Cpd of Logic ICs.

I have gone through some documents on TI Website but didnt get satisfied answer.

I want to know >>

1)  what is the exact significance of above mentioned Pin properties.

2) Suppose if I want to interface the output of IC with Cout = 5 pF to IC with Cin = 10 pF, will there be any loading and effect on signal timings?

3) Any further knowledge input will be helpfull.

Thank you.

  • 0
    Guru 316940 points

    See the FAQ entry Anatomy of a Data Sheet, sections 4.6.29, 4.6.31, and 4.11.1 in the linked document.

    (In short: Cout applies only to high-impedance outputs, and Cpd means that the chip uses up as much power as such a capacitor.)

  • 0 in reply to Clemens Ladisch
    Prodigy 250 points
    Thank you Clemens for the feedback.
    I have already refered the suggested document and I found the explaination about the term in generalise form.
    What I want to know is the practical application implications of these terms. ( as I mentioned in the example )
    Thank you.
  • 0 in reply to SS_hwdesign
    Guru 316940 points

    When you connect the output of one IC to an input with Cin = 10 pF, then the load on the output will be the same as if there were a capacitor with 10 pF (plus any parasitic capacitances of your circuit). Higher capacitances make the switching slower (this is why all timing values specifiy the load capacitance).

    Cout would apply only to an output in the high-impedance state; when the output is active, the pin is connected to VCC or GND, and it does not make sense to speak of capacitance.

    Cpd measures how much power the device uses up when switching, on top of the static supply current (ICC). It has the form of a capacitance because it is frequency dependent; for details, see CMOS Power Consumption and Cpd Calculation (SCAA035).