MPC5644B View Datasheet(PDF) - Freescale Semiconductor
Part Name
Description
MFG CO.
'MPC5644B' PDF : 114 Pages View PDF
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:
Therefore, solving equations 1 and 2:
PD = K / (TJ + 273 °C)
Eqn. 2
K = PD (TA + 273 °C) + RJA PD2
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.
MPC5646C Microcontroller Data Sheet, Rev. 3
46
Preliminary—Subject to Change Without Notice
Freescale Semiconductor
Share Link: 
