How can the power dissipation of a general-purpose logic IC be calculated?

Power dissipation can be obtained by multiplying the above current by the voltage applied to an IC.

Static power dissipation: P_S
While general-purpose logic ICs are in a static state (i.e., while its input signal remains unchanged), little current flows in it except tiny leakage current that flows across the internal reverse-biased pn junction (known as static supply current, I_CC). Static power dissipation is I_CC multiplied by the supply voltage.

P_S = V_CC x I_CC
V_CC: Voltage applied to a logic IC
I_CC: Static supply current shown in the datasheet

Dynamic power dissipation
Dynamic supply current is the current that flows in general-purpose logic while its input transitions between High and Low. This current flows during the charging and discharging of capacitance. It is necessary to consider both parasitic capacitance (internal equivalent capacitance) and load capacitance. Dynamic power dissipation is obtained by multiplying this current by the voltage applied to the P-channel or N-channel MOSFET. Here, for the sake of simplicity, the V_CC value at which the maximum current flows is used for power calculation.

Dynamic power dissipation due to load capacitance (C_L): P_L
P_L is dissipated when an external load is charged and discharged as shown by the Fig. 1.
The amount of charge (Q) stored on the load capacitance is calculated as follows:

Q_L = C_L x V_CC
C_L: Load capacitance

Let the output signal frequency be f_OUT (= 1/T_OUT). Then, the average current (I_L) is expressed as follows:

I_L = QL / T = C_L * V_CC * f_OUT

Hence, dynamic power dissipation (P_L) is:

P_L = V_CC * I_L ＝ C_L * V_CC^2 * f_OUT

If an IC has multiple outputs, its dynamic power dissipation can be calculated as follows:

P_L = V_CC^2 * Σ (C_Ln* f_OUTn)

Dynamically Consumed Power with Equivalent Internal Capacitive C_PD: P_PD

General-purpose logic ICs have various parasitic capacitances as shown by Fig. 2. These capacitances are equivalently expressed as C_PD. (Actually, C_PD is calculated from power dissipation at relatively high frequency (1 MHz) under a zero-load condition.) P_PD is the power dissipated by the equivalent capacitance of an IC and can be considered in the same manner as P_L. Note, however, that P_PD is calculated at input frequency (f_IN):

P_PD ＝ V_CC * I_L ＝ C_PD * V_CC^2 * f_IN