MPC5601DXLL datasheet(25/77 Pages) FREESCALE

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Electrical characteristics

MPC5602D Microcontroller Data Sheet, Rev. 3.1

Preliminary—Subject to Change Without Notice

Freescale Semiconductor

4.6.2

Power considerations

The average chip-junction temperature, TJ, in degrees Celsius, may be calculated using Equation 1:

TJ = TA + (PD x RJA)

Eqn. 1

Where:

TA is the ambient temperature in °C.

RJA is the package junction-to-ambient thermal resistance, in °C/W.

PD is the sum of PINT and PI/O (PD = PINT + PI/O).

PINT is the product of IDD and VDD, expressed in watts. This is the chip internal power.

PI/O represents the power dissipation on input and output pins; user determined.

Most of the time for the applications, PI/O< PINT and may be neglected. On the other hand, PI/O may be significant, if the device

is configured to continuously drive external modules and/or memories.

An approximate relationship between PD and TJ (if PI/O is neglected) is given by:

PD = K / (TJ + 273 °C)

Eqn. 2

Therefore, solving equations 1 and 2:

K = PD x (TA + 273 °C) + RJA x PD

Eqn. 3

Where:

K is a constant for the particular part, which may be determined from Equation 3 by measuring PD (at equilibrium)

for a known TA. Using this value of K, the values of PD and TJ may be obtained by solving equations 1 and 2

iteratively for any value of TA.

4.7

I/O pad electrical characteristics

4.7.1

I/O pad types

The device provides four main I/O pad types depending on the associated alternate functions:

•

Slow pads—These pads are the most common pads, providing a good compromise between transition time and low

electromagnetic emission.

•

Medium pads—These pads provide transition fast enough for the serial communication channels with controlled

current to reduce electromagnetic emission.

•

Input only pads—These pads are associated to ADC channels (ADC_P[X]) providing low input leakage.

Medium pads can use slow configuration to reduce electromagnetic emission except for PC[1], that is medium only, at the cost

of reducing AC performance.

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