HDSP-210X_08 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, q_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