56F8356 Datasheet, PDF (166/176 Pages) Motorola, Inc – 56F8356 16-bit Hybrid Controller

where:
• Summation is performed over all output 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. The one possible exception to this is if the chip is
using the external address and data buses at a rate approaching the maximum system rate. In this case,
power from these buses can be significant.
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 8 PWM 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.
56F8356 Technical Data, Rev. 13
166
Freescale Semiconductor
Preliminary