13
taneously at full brightness for 10
seconds at 25°C as a lamp test.
The IC has a maximum allowable
junction temperature of 150°C.
The IC junction temperature can
be calculated with the following
equation:
T
J
MAX = T
A
+ (P
D
x Rθ
J-A
)
T
J
MAX is the maximum allowable
IC junction temperature.
T
A
is the ambient temperature
surrounding the display.
P
D
is the power dissipated by the
IC.
Rθ
J-A
is the thermal resistance
from the IC through the display
package and printed circuit board
to the ambient.
A typical value for Rθ
J-A
is
39°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 0.062 in.
thick printed circuit board with
0.020 in. wide one-ounce copper
traces.
P
D
can be calculated as follows:
P
D
= V
DD
x I
DD
V
DD
is the supply voltage and I
DD
is the supply current.
V
DD
can vary from 4.5 V to 5.5 V.
I
DD
changes with V
DD
,
temperature, brightness level, and
number of on-pixels.
Figure 9. Improper Method to Manually Insert a Display.
Figure 8. Proper Method to Manually Insert a Display.
Thermal Considerations
The HDSP-253X can operate from
-40°C to +85°C. The display’s low
thermal resistance allows heat to
flow from the CMOS IC to the 24
package pins. Typically, this heat
is conducted through the printed
circuit board traces to free air.
For most applications, no
additional heatsinking is needed.
Illuminating all 280 LEDs
simultaneously at full brightness
is not recommended for continuo-
us operation. However, all 280
LEDs can be illuminated simul-
For AlGaAs
I
DD
(#) = (83.8 x V
DD
-0.35 x T
J
)
x B x N/8
I
DD
(V) = (63 x V
DD
-0.79 x T
J
) x
B x N/8
For the other colors
I
DD
(#) = (75.4 x V
DD
-0.28 x T
J
)
x B x N/8
AGILENT [ AGILENT TECHNOLOGIES, LTD. ]
