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I\)
I\)
EXAMPLE 2 -CALCULATION STD/7000 MIXED CARD SYSTEM
Equations, Assumptions and Constants
7701 Memory Card with 16K/2114L's convection cooling
°
Absolute T
J
=
125 C
Desired Maximum T
J
=
115°C
Hottest IC for 7701 RAM card is
2114L in center of card
RaJc:: 45°C/watt
Pmax (2114L)
=
O.37W
TA
~
24°C
T J
=
T C
+
Raj C . (Pmax)
1/2'
t
spac
i
ng
TA
=
24.8°C
TC
=
70.8°C(measured)
°
T
J
=
70.8 C
+
(45
0
C/W}(0.37W)
T
J
=
70.8°C
+
17°C
=
87.8°0
AT
=
T
J
maximum desired - T
J
Calculatedl AT
=
115°C - 87.8°c
=
27.2°C
T A' maxi mum - T A measured
+
AT
Maximum T
A
=
24.8°C + 27.2
0
C
°
TA,max
=
52 C
I
1" spac i ng component· side 7701 on 1)
TA of 24.8°C
TC
=
64.8°C(measured)
T
J
"64.8°C
+
(45
0
C/W)(0.J7W)
T
J
64.8°C
+ 17°C
=
81.8°c
AT
=
l15
u
C - 8l.8
u
c
=
33.2
u
C
Max T
A
=
24.8°c + 33.2
0
C
=
58°C
T
A
max.
=
58°C
NOTE:
these calculations are for the first two of three examples of configuring a system for
even power (heat distribution).
See figure
The data taken on cards mounted in a Pro-Log CR16A card cage with
3/8"
rubber feet.
o
o
o
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