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 ?

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 281410 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 C_pd × V_CC² × f_I for all input pins (where f_I could be different per pin), and add up C_L × V_CC² × f_O for all output pins (where f_O could be different per pin).

0 Lin Vast over 1 year ago 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 Clemens Ladisch over 1 year ago in reply to Lin Vast

Guru 281410 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 P_T.
(You have P_T = C_pd × V_CC² × 10 kHz + C_pd × V_CC² × 10 kHz + C_pd × V_CC² × 0 Hz = C_pd × V_CC² × (10 kHz + 10 kHz + 0 Hz) = C_pd × V_CC² × 10 kHz × 2.)

0 Lin Vast over 1 year ago in reply to Clemens Ladisch

Prodigy 240 points

OK,I got it,thanks a lot.

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SN74HCS11-Q1: Loss calculate