HDSP-2107_10 Datasheet, PDF (15/16 Pages) AVAGO TECHNOLOGIES LIMITED – Eight Character 5 mm and 7 mm Smart Alphanumeric Displays

Thermal Considerations
The HDSP-210X/-211X/-212X/250X have been designed
to provide a low thermal resistance path for the CMOS
IC to the 26 package pins. Heat is typically conducted
through the traces of the printed circuit board to free
air. For most applications no additional heatsinking is
required.
Measurements were made on a 32 character display
string to determine the thermal resistance of the display
assembly. Several display boards were constructed using
0.062 in. thick printed circuit material, and one ounce
copper 0.020 in. traces. Some of the device pins were
connected to a heatsink formed by etching a copper
area on the printed circuit board surrounding the display.
A maximally metallized printed circuit board was also
evaluated. The junction temperature was measured for
displays soldered directly to these PC boards, displays
installed in sockets, and finally displays installed in
sockets with a filter over the display to restrict airflow.
The results of these thermal resistance measurements,
Rq_J-A are shown in Table 3 and include the effects of
Rq_J-C.
Ground Connections
Two ground pins are provided to keep the internal IC
logic ground clean. The designer can, when necessary,
route the analog ground for the LED drivers separately
from the logic ground until an appropriate ground
plane is available. On long interconnections between
the display and the host system, the designer can keep
voltage drops on the analog ground from affecting the
display logic levels by isolating the two grounds.
The logic ground should be connected to the same
ground potential as the logic interface circuitry.
The analog ground and the logic ground should be
connected at a common ground which can withstand
the current introduced by the switching LED drivers.
When separate ground connections are used, the analog
ground can vary from -0.3 V to +0.3 V with respect to the
logic ground. Voltage below -0.3 V can cause all dots to
be on. Voltage above +0.3 V can cause dimming and dot
mismatch.
Soldering and Post Solder
Cleaning Instructions for the
HDSP-210X/-211X/-250X
The HDSP-210X/-211X/-250X may be hand soldered or
wave soldered with SN63 solder. When hand soldering,
it is recommended that an electronically temperature
controlled and securely grounded soldering iron be used.
For best results, the iron tip temperature should be set at
315°C (600°F). For wave soldering, a rosin-based RMA flux
can be used. The solder wave temperature should be set
at 245°C ± 5°C (473°F ± 9°F), and the dwell in the wave
should be set between 1¹ /₂ to 3 seconds for optimum
soldering. The preheat temperature should not exceed
105°C (221°F) as measured on the solder side of the PC
board.
For additional information on soldering and post solder
cleaning, see Application Note 1027, Soldering LED Com-
ponents.
Contrast Enhancement
The objective of contrast enhancement is to provide
good readability in a variety of ambient lighting condi-
tions. For information on contrast enhancement see
Application Note 1015, Contrast Enhancement Techniques
for LED Displays.
Table 3. Thermal Resistance, T_JA, Using Various Amounts
of Heatsinking Material
Heatsinking
Metal
per Device
sq. in.
W/Sockets
W/O Filter
(Avg.)
W/O Sockets
W/O Filter
(Avg.)
W/Sockets
W/Filter
(Avg.)
Units
0
31
30
35
°C/W
1
31
28
33
°C/W
3
30
26
33
°C/W
Max. Metal
29
25
32
°C/W
4 Board Avg
30
27
33
°C/W
15