HCMS-39X2 Datasheet, PDF (18/22 Pages) Agilent(Hewlett-Packard) – 3.3 V High Performance CMOS 5x7 AlphaNumeric Displays

Appendix A. Thermal
Considerations
The display IC has a maximum
junction temperature of 150°C.
The IC junction temperature can
be calculated with Equation 1 in
Table 3.
A typical value for Rθ_JA is 100°C/
W. This value is typical for a
display mounted in a socket and
covered with a plastic filter. The
socket is soldered to a .062 inch
thick PCB with .020-inch wide,
one ounce copper traces. P_D can
be calculated as Equation 2 in
Table 3.
Figure 9 shows how to derate the
power of one IC versus ambient
temperature. Operation at high
ambient temperatures may
require the power per IC to be
reduced. The power consumption
can be reduced by changing the
N, I_PIXEL , Osc cyc or V_LED.
Changing V_LOGIC has very little
impact on the power
consumption.
1.3
1.2
R_θJ-A = 100°C/W
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
25 30 35 40 45 50 55 60 65 70 75 80 85 90
T_A– AMBIENT TEMPERATURE – °C
Figure 9. Maximum power dissipation per IC versus ambient temperature.
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