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EXAMPLE 1
SAMPLE CALCULATIONS 7701 MEMORY CARD
Equations, Assumpti9ns and Constants
a
Absolute T
J
=
125 C
Desired Maximum T
J
=
1t50C
Hottest IC for ],101 RAM card is 2114L
in center of card
&.
RWC
=
45
0
C/watt
Pmax(2l14L)
=
0.37
w
T
J
=
Te
+
RSJC . (Pmax)
~T
=
T
J
maximum desired - T
J
calculated
Maximum T
A
= TA measured +AT
Calculations for 7701 Memory Card with 16K/2114L's convection/
coorlnq
1/2
i
'
Spacing
&
TA
=
23.2
0
e
TC
=
93.2
0
C (measured)
T
Jf.
93. 2°C :' " (45°C/W) ( · 37W)
T L.93.20C + 17°C = l10·.2 o C
J -
'
~T
=
115°C ~ l10.2 o C
=
4.8°c
Max
i
mum T A'
=
23.
2
o
C+.l ••
8°C=28°C
1" Spacing
&
TA
=
23.2
0
e
Te
=
65.2
o
C (measured)
T J
='6 5
;~;
20(:
+ ( 4 5°
c
/w·) • 37W
T
=65'
~1oe
+ l7°e
= 82. 2
0
e
I
J
.6T
=
l1s6e ~ ~2. 2.
o
e
=
32.8
Max
i
mum T
f(
= 23. 2°C. + 32. aOC=56°c
&
The data taken was on the center card of 3 adjac-ent memory cards.
~
Abreviations:
TA
=
Temperature ambient, T
J
=
Temperature junction, TC = Temperature case,
ReJC
=
Thermal resistance junction to case, P = Power
&
The data was taken on cards mounted in a Pro-Log card cage with 3/8" rubber feet
o
&
DJta WJS tJken on the center card of 3
memoO~rds
on the IndIcated spacing
i~
" \
~
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