mc68hc05l28 Freescale Semiconductor, Inc, mc68hc05l28 Datasheet - Page 126

• Manufacturer Part Number: mc68hc05l28
• Description: ?exible General-purpose Microcomputer
• Manufacturer: Freescale Semiconductor, Inc

12
12.2
The average chip junction temperature, T
equation:
where:
An approximate relationship between P
Solving equations [1] and [2] for K gives:
where K is a constant for a particular part. K can be determined by measuring P
for a known T
by solving the above equations. The package thermal characteristics are shown in Table 12-2.
MOTOROLA
12-2
PA0–7, PB0–7
A
Thermal characteristics and power considerations
. Using this value of K, the values of P
P
P
Pins
P
INT
T
I/O
JA
D
A
= Ambient Temperature ( C)
= Package Thermal Resistance, Junction-to-ambient ( C/W)
= P
= Internal Chip Power = I
= Power Dissipation on Input and Output pins (User determined)
Thermal Resistance
– Plastic 56-pin SDIP
INT
Table 12-2 Package thermal characteristics
3.26k
+ P
R1
Characteristics
K
I/O
ELECTRICAL SPECIFICATIONS
Figure 12-1 Equivalent test load
=
(W)
2.38k
P
T
R2
D
J
D
P
=
J
D
and T
, in degrees Celcius can be obtained from the following
T
T
=
A
50pF
A
C
+
+
--------------------- -
T
DD
273
J
J
P
(if P
+
• V
K
D
273
Symbol
DD
+
D
I/O
JA
and T
JA
(W)
JA
is neglected) is:
P
J
Value
D
TBD
can be obtained for any value of T
Point
Test
2
Unit
C/W
C
V
DD
= 4.5 V
D
MC68HC05L28
(at equilibrium)
R2
R1
[1]
[2]
[3]
A
TPG