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SN74HCS11-Q1: Loss calculate

Lin Vast
Prodigy 240 points
Part Number: SN74HCS11-Q1

I want to calculate the loss of SN74HCS11-Q1.

From CMOS Power Consumption and Cpd Calculation in the pdf,

I havew some problem,

PT=Cpd*VCC^2*fI*NSW

NSW = number of bits switching

PL=CL*VCC^2*fo*NSW

NSW = total number of outputs switching

Does NSW stand for the same thing ?

Does NSW represent the amount of outputs I use ?

  • 0
    Guru 281250 points

    These equations assume that NSW input or output pins are switching at the same frequency. The SN74HCS11-Q1 has nine inputs and three outputs, so these NSW values are unlikely to be the same.

    In the more general case, add up Cpd × VCC² × fI for all input pins (where fI could be different per pin), and add up CL × VCC² × fO for all output pins (where fO could be different per pin).

  • 0 in reply to Clemens Ladisch
    Prodigy 240 points

    Pin1、2、13 are the same input of the AND gate.

    If I want to calculate the loss of this AND gate.

    I should calculate PT-Pin1,PT-Pin2,PT-Pin13,PL-Pin12,is it right ?

    Both Pin1 and Pin2 are at a frequency of 10K.

    Pin12 is always high.

    Could you tell me how to set the value of NSW and the value of fi of Pin12 ?

  • +1 in reply to Lin Vast
    Guru 281250 points

    Pins 1/2/13 are inputs, pin 12 is output.

    When pin 13 is always high, then the frequency is zero, and you can ignore it for PT.
    (You have PT = Cpd × VCC² × 10 kHz + Cpd × VCC² × 10 kHz + Cpd × VCC² × 0 Hz = Cpd × VCC² × (10 kHz + 10 kHz + 0 Hz) = Cpd × VCC² × 10 kHz × 2.)

  • 0 in reply to Clemens Ladisch
    Prodigy 240 points

    OK,I got it,thanks a lot.