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MC68331
USER’S MANUAL
ELECTRICAL CHARACTERISTICS
MOTOROLA
A-3
A
NOTES:
The average chip-junction temperature (T
J
) in C can be obtained from:
T
J
= T
A
+ (P
D
×
Θ
Α
)
(1)
where
T
A
Θ
Α
P
D
P
INT
P
I/O
=
=
=
=
=
Ambient Temperature,
°
C
Package Thermal Resistance, Junction-to-Ambient,
°
C/W
P
INT
+ P
I/O
I
DD
×
V
DD
, Watts — Chip Internal Power
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:
P
D
= K
÷
(T
J
+ 273
°
C)
Solving equations 1 and 2 for K gives:
K = P
D
+ (T
A
+ 273
°
C) +
Θ
Α
×
P
D2
where K is a constant pertaining to the particular part. K can be determined from equation (3) by mea-
suring P
D
(at equilibrium) for a known T
A
. Using this value of K, the values of P
D
and T
J
can be ob-
tained by solving equations (1) and (2) iteratively for any value of T
A
.
(2)
(3)
Table A-3 Thermal Characteristics
Num
1
Rating
Symbol
Θ
Α
Value
Unit
°
C/W
Thermal Resistance
Plastic 132-Pin Surface Mount
Plastic 144-Pin Surface Mount
Thin Plastic 144-Pin Surface Mount
38
46
49
Table A-4 16.78 MHz Clock Control Timing
(V
DD
and V
DDSYN
= 5.0 Vdc
±
10%, V
SS
= 0 Vdc, T
A
= T
L
to T
H,
32.768 kHz reference)
Num
1
2
Characteristic
Symbol
f
ref
Min
25
dc
0.131
dc
—
Max
50
16.78
16.78
16.78
20
Unit
kHz
PLL Reference Frequency Range
System Frequency
1
On-Chip PLL System Frequency
External Clock Operation
PLL Lock Time
2,3,4,5
VCO Frequency
6
Limp Mode Clock Frequency
SYNCR X bit = 0
SYNCR X bit = 1
CLKOUT Stability
2,3,4,7
Short term (5
μ
s interval)
Long term (500
μ
s interval)
f
sys
MHz
3
4
5
t
lpll
f
VCO
f
limp
ms
MHz
MHz
2 (f
sys
max)
—
—
f
sys
max/2
f
sys
max
6
C
stab
–0.5
–0.05
0.5
0.05
%