Datasheet

Power Consumption
56F8356 Technical Data, Rev. 13
Freescale Semiconductor 165
Preliminary
3. Equivalent resistance for the ESD isolation resistor and the channel select mux; 500 ohms
4. Sampling capacitor at the sample and hold circuit. Capacitor C1 is normally disconnected from the input and is only
connected to it at sampling time; 1pf
Figure 10-23 Equivalent Circuit for A/D Loading
10.18 Power Consumption
This section provides additional detail which can be used to optimize power consumption for a given
application.
Power consumption is given by the following equation:
A, the internal [static component], is comprised of the DC bias currents for the oscillator, PLL, leakage
current, and voltage references. These sources operate independently of processor state or operating
frequency.
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*V
2
*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*V
2
*F, although simulations on two
of the IO cell types used on the device reveal that the power-versus-load curve does have a non-zero
Y-intercept.
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)
Total power =
A: internal [static component]
+B: internal [state-dependent component]
+C: internal [dynamic component]
+D: external [dynamic component]
+E: external [static]
Table 10-25 IO Loading Coefficients at 10MHz
Intercept Slope
PDU08DGZ_ME 1.3 0.11mW / pF
PDU04DGZ_ME 1.15mW 0.11mW / pF