15
used. Prior to use, the HDSP-
210X/-211X/-250X should be
stored in antistatic tubes or in
conductive material. During
assembly, a grounded conductive
work area should be used, and
assembly personnel should wear
conductive wrist straps. Lab
coats made of synthetic material
should be avoided since they are
prone to static buildup. Input
current latchup is caused when
the CMOS inputs are subjected to
either a voltage below ground
(V
IN
< ground) or to a voltage
higher than V
DD
(V
IN
> V
DD
) and
when a high current is forced into
the input. To prevent input
current latchup and ESD damage,
unused inputs should be con-
nected either to ground or to V
DD
.
Voltages should not be applied to
the inputs until V
DD
has been
applied to the display.
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, Rθ
J-A
are shown in Table 3 and include
the effects of Rθ
J-C
.
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.
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 interconnec-
tions 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
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 recom-
mended 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 solder-
ing, a rosin-based RMA flux can
be used. The solder wave temper-
ature should be set at 245°C
±
5°C (473°F
±
9°F), and the dwell
in the wave should be set
between 1
1
/
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.
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.
Table 3. Thermal Resistance,
θ
JA
, Using Various Amounts of
Heatsinking Material
Heatsinking
Metal
per Device
sq. in.
0
1
3
Max. Metal
4 Board Avg
W/Sockets W/O Sockets
W/O Filter W/O Filter
(Avg.)
(Avg.)
31
31
30
29
30
30
28
26
25
27
W/Sockets
W/Filter
(Avg.)
35
33
33
32
33
Units
°C/W
°C/W
°C/W
°C/W
°C/W
AGILENT [ AGILENT TECHNOLOGIES, LTD. ]
