HDSP-253X HP [Agilent(Hewlett-Packard)], HDSP-253X Datasheet - Page 14

• Manufacturer Part Number: HDSP-253X
• Description: Eight Character 5 mm Smart Alphanumeric Display
• Manufacturer: HP [Agilent(Hewlett-Packard)]

I
x N/8
I
using “#” as the displayed
character.
I
“V” as the displayed character.
T
B is the percent brightness level.
N is the number of characters
illuminated.
Operation in high temperature
ambients may require power
derating or heatsinking. Figure 10
shows how to derate the power
for an HDSP-253X. You can
reduce the power by tighter
supply voltage regulation or
lowering the brightness level.
Table 3 shows the calculated
maximum allowable ambient
temperature for several different
sets of operating conditions. The
Table 3. Maximum Allowable Ambient Temperature for Various Operating Conditions
AlGaAs Red
DD
DD
DD
J
is the IC junction temperature.
(V) = (54 x V
(V) is the supply current using
Character
# (20 dots)
# (20 dots)
# (20 dots)
# (20 dots)
# (20 dots)
# (20 dots)
# (20 dots)
# (20 dots)
V (12 dots)
(#) is the supply current
DD
-0.6 x T
Characters
Number of
8
8
8
7
6
8
8
8
8
J
) x B
worst case alphanumeric
characters (#,@,B) have 20
pixels. Displaying eight 20-pixel
characters will not occur in
normal operation. Thus, using
eight 20-pixel characters to
calculate power dissipation will
over estimate the power and the
IC junction temperature. The
average number of pixels per
character, supply voltage,
brightness level, and number of
characters are needed to calculate
the power dissipated by the IC.
The ambient temperature, power
dissipated by the IC, and the
thermal resistance are then used
to calculate IC junction tempera-
ture. The typical alphanumeric
character is 15 pixels. For
conditions not listed in Table 3,
you can calculate the power
dissipated by the IC and use
Figure 10 to determine the
maximum ambient temperature.
Brightness
Level
100%
100%
100%
100%
100%
100%
80%
80%
53%
5.25
5.25
V
5.5
5.0
5.5
5.5
5.5
5.5
5.5
DD
V
408
387
366
357
306
327
310
216
228
mA
I
DD
14
Figure 10. Maximum Allowable
Power Dissipation vs. Ambient
Temperature. T
120 C.
2.2
2.0
1.8
2.0
1.7
1.8
1.6
1.2
1.3
P
W
D
R
J
C/W
MAX = 150 C or
39
39
39
39
39
39
39
39
39
J-A
T
A
MAX
64
72
80
72
84
80
85
85
85
C