56F8322 Techncial Data, Rev. 10.0
126 Freescale Semiconductor
Preliminary
B, the internal [state-dependent component], reflects the supply current required by certain on-chip
resources only when those resources are in use. These include RAM, Flash memory and the ADCs.
C, the internal [dynamic component], is classic C*V2*F CMOS power dissipation corresponding to the
56800E core and standard cell logic.
D, the external [dynamic component], reflects power dissipated on-chip as a result of capacitive loading
on the external pins of the chip. This is also commonly described as C*V2*F, although simulations on two
of the IO cell types used on the 56800E reveal that the power-versus-load curve does have a non-zero
Y-intercept.
Note: VREFH is tied to VDDA and VREFLO is tied to VSSA inside this package.
Power due to capacitive loading on output pins is (first order) a function of the capacitive load and
frequency at which the outputs change. Table 10-25 provides coefficients for calculating power dissipated
in the IO cells as a function of capacitive load. In these cases:
TotalPower = Σ((Intercept + Slope*Cload)*frequency/10MHz)
where:
Summation is performed over all outp ut pins with capacitive loads
TotalPower is expressed in mW
Cload is expressed in pF
Because of the low duty cycle on most device pins, power dissipation due to capacitive loads was found
to be fairly low when averaged over a period of time.
E, the external [static component], reflects the effects of placing resistive loads on the outputs of the
device. Sum the total of all V2/R or IV to arrive at the resistive load contribution to power. Assume V =
0.5 for the purposes of these rough calculations. For instance, if there is a total of eight P WM outputs
driving 10mA into LEDs, then P = 8*.5*.01 = 40mW.
In previous discussions, power consumption due to parasitics associated with pure input pins is ignored,
as it is assumed to be negligible.
Table 10-25 IO Loading Coefficients at 10MHz
Intercept Slope
PDU08DGZ_ME 1.3 0.11mW / pF
PDU04DGZ_ME 1.15mW 0.11mW / pF