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