MCF51EM128 查看數據表（PDF） - Freescale Semiconductor
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MCF51EM128 Datasheet PDF : 54 Pages
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Electrical Characteristics
3 Power supply must maintain regulation within operating VDD range during instantaneous and
operating maximum current conditions. If positive injection current (VIn > VDD) is greater than
IDD, the injection current may flow out of VDD and could result in external power supply going
out of regulation. Ensure external VDD load will shunt current greater than maximum injection
current. This will be the greatest risk when the MCU is not consuming power. Examples are: if
no system clock is present, or if the clock rate is very low which would reduce overall power
consumption.
4 Input must be current limited to the value specified. To determine the value of the required
current-limiting resistor, calculate resistance values for positive (VDD) and negative (VSS) clamp
voltages, then use the larger of the two resistance values.
5 All functional non-supply pins are internally clamped to VSS and VDD.
6 Power supply must maintain regulation within operating VDD range during instantaneous and
operating maximum current conditions. If positive injection current (VIn > VDD) is greater than
IDD, the injection current may flow out of VDD and could result in external power supply going
out of regulation. Ensure external VDD load will shunt current greater than maximum injection
current. This will be the greatest risk when the MCU is not consuming power. Examples are: if
no system clock is present, or if the clock rate is very low which would reduce overall power
consumption.
2.3 Thermal Characteristics
This section provides information about operating temperature range, power dissipation, and package
thermal resistance. Power dissipation on I/O pins is usually small compared to the power dissipation in
on-chip logic and it is user-determined rather than being controlled by the MCU design. In order to take
PI/O into account in power calculations, determine the difference between actual pin voltage and VSS or
VDD and multiply by the pin current for each I/O pin. Except in cases of unusually high pin current (heavy
loads), the difference between pin voltage and VSS or VDD will be very small.
Table 7. Thermal Characteristics
Rating
Operating temperature range (packaged)
Maximum junction temperature
Thermal resistance 1,2,3,4
Symbol
Value
Unit
TA
–40 to 85
°C
TJM
95
°C
100-pin LQFP
80-pin LQFP
1s
2s2p
θJA
1s
2s2p
54
42
°C/W
55
42
1 Junction temperature is a function of die size, on-chip power dissipation, package thermal
resistance, mounting site (board) temperature, ambient temperature, air flow, power dissipation
of other components on the board, and board thermal resistance.
2 Junction to Ambient Natural Convection
3 1s — Single layer board, one signal layer
4 2s2p — Four layers board, two signal and two power layers
The average chip-junction temperature (TJ) in °C can be obtained from:
MCF51EM256 Series ColdFire Microcontroller Data Sheet, Rev.2
18
Preliminary—Subject to Change Without Notice
Freescale Semiconductor
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