MC9S08QE32 Datasheet, PDF (10/44 Pages) Freescale Semiconductor, Inc – 8-Bit HCS08 Central Processor Unit (CPU)

Electrical Characteristics
3 _{Power supply must maintain regulation within operating VDD range during instantaneous and}
operating maximum current conditions. If positive injection current (V_In > V_DD) is greater than
I_DD, the injection current may flow out of V_DD and could result in external power supply going
out of regulation. Ensure external V_DD 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).
3.4 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 voltage regulator circuits, and
it is user-determined rather than being controlled by the MCU design. To take P_I/O into account in power calculations, determine
the difference between actual pin voltage and V_SS or V_DD 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 V_SS or V_DD will be very small.
Table 4. Thermal Characteristics
Rating
Operating temperature range
(packaged)
Maximum junction temperature
Thermal resistance
Single-layer board
48-pin QFN
44-pin LQFP
32-pin LQFP
28-pin SOIC
Thermal resistance
Four-layer board
48-pin QFN
44-pin LQFP
32-pin LQFP
28-pin SOIC
Symbol
T_A
T_JM
θ_JA
Value
Unit
T_L to T_H
–40 to 85
°C
95
°C
81
68
°C/W
66
57
26
46
θ_JA
°C/W
54
42
The average chip-junction temperature (T_J) in °C can be obtained from:
T_J = T_A + (P_D × θ_JA)
Eqn. 1
where:
T_A = Ambient temperature, °C
θ_JA = Package thermal resistance, junction-to-ambient, °C/W
P_D = P_int + P_I/O
P_int = I_DD × V_DD, Watts — chip internal power
P_I/O = Power dissipation on input and output pins — user determined
For most applications, P_I/O << P_int and can be neglected. An approximate relationship between P_D and T_J (if P_I/O is neglected)
is:
MC9S08QE32 MCU Series Data Sheet, Rev. 1
10
Freescale Semiconductor