Datasheet

MC9RS08KB12 Series MCU Data Sheet, Rev. 5
Electrical Characteristics
Freescale Semiconductor8
unusually high pin current (heavy loads), the difference between pin voltage and V
SS
or V
DD
will be very
small.
The average chip-junction temperature (TJ) 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 PD and TJ
(if P
I/O
is neglected) is:
P
D
= K ÷ (T
J
+ 273°C) Eqn. 2
Solving Equation 1 and Equation 2 for K gives:
K = P
D
× (T
A
+ 273°C) + θ
JA
× (PD)
2
Eqn. 3
where K is a constant pertaining to the particular part. K can be determined from Equation 3 by measuring
P
D
(at equilibrium) for a known T
A
. Using this value of K, the values of P
D
and T
J
can be obtained by
solving Equation 1 and Equation 2 iteratively for any value of T
A
.
3.5 ESD Protection and Latch-Up Immunity
Although damage from electrostatic discharge (ESD) is much less common on these devices than on early
CMOS circuits, normal handling precautions must be used to avoid exposure to static discharge.
Qualification tests are performed to ensure that these devices can withstand exposure to reasonable levels
of static without suffering any permanent damage.
Table 4. Thermal Characteristics
Rating Symbol Value Unit
Operating temperature range (packaged)
T
A
T
L
to T
H
–40 to 85
°C
Maximum junction temperature T
JMAX
150 °C
Thermal resistance 24-pin QFN θ
JA
113 °C/W
Thermal resistance 20-pin SOIC θ
JA
83 °C/W
Thermal resistance 16-pin SOIC NB θ
JA
103 °C/W
Thermal resistance 16-pin TSSOP θ
JA
29 °C/W
Thermal resistance 8-pin SOIC θ
JA
150 °C/W
Thermal resistance 8-pin DFN θ
JA
110 °C/W