Datasheet

MC9S08SF4 Series MCU Data Sheet, Rev. 4
Thermal Characteristics
Freescale Semiconductor6
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 small.
The average chip-junction temperature (T
J
) in C can be obtained from:
T
J
= T
A
+ (P
D
 
JA
) Eqn. 1
Table 2. Absolute Maximum Ratings
Rating Symbol Value Unit
Supply voltage V
DD
–0.3 to 5.8 V
Maximum current into V
DD
I
DD
120 mA
Digital input voltage V
In
–0.3 to V
DD
+0.3 V
Instantaneous maximum current
Single pin limit (applies to all port pins)
1, 2, 3
1
Input must be current limited to the value specified. To determine the value of the required
current-limiting resistor, calculate resistance values for positive (V
DD
) and negative (V
SS
) clamp
voltages, then use the larger of the two resistance values.
2
All functional non-supply pins are internally clamped to V
SS
and V
DD
.
3
Power supply must maintain regulation within operating V
DD
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 the external power supply going
out of regulation. Ensure external V
DD
load shunts current greater than the 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).
I
D
25 mA
Storage temperature range T
stg
–55 to 150 C
Table 3. Thermal Characteristics
Rating Symbol Value Unit
Operating temperature range
(packaged)
T
A
T
L
to T
H
–40 to 125
C
Thermal resistance (single-layer board)
20-pin TSSOP
16-pin TSSOP

JA
115
123
C/W
Thermal resistance (four-layer board)
20-pin TSSOP
16-pin TSSOP

JA
76
75
C/W