MPC5646C datasheet(46/114 Pages) FREESCALE

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MPC5646C Microcontroller Data Sheet, Rev. 3

Preliminary—Subject to Change Without Notice

Freescale Semiconductor

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  (TA + 273 °C) + RJA  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.

4.6

I/O pad electrical characteristics

4.6.1

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.

•

Fast pads—These pads provide maximum speed. These are used for improved Nexus debugging capability.

•

Input only pads—These pads are associated to ADC channels and 32 kHz low power external crystal oscillator

providing low input leakage.

•

Low power pads—These pads are active in standby mode for wakeup source.

Also, medium/slow and fast/medium pads are available in design which can be configured to behave like a slow/medium and

medium/fast pads depending upon the slew-rate control.

Medium and fast pads can use slow configuration to reduce electromagnetic emission, at the cost of reducing AC performance.

4.6.2

I/O input DC characteristics

Table 13 provides input DC electrical characteristics as described in Figure 5.

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