11
Mechanical and Electrical
Considerations
The HDLX-2416 is an 18 pin DIP
package that can be stacked
horizontally and vertically to
create arrays of any size. The
HDLX-2416 is designed to operate
continuously from -40
°
C to + 85
°
C
for all possible input conditions.
The HDLX-2416 is assembled by
die attaching and wire bonding
140 LEDs and a CMOS IC to a
high temperature printed circuit
board. A polycarbonate lens is
placed over the PC board creating
an air gap environment for the
LED wire bonds. Backfill epoxy
environmentally seals the display
package. This package construc-
tion makes the display highly
tolerant to temperature cycling
and allows wave soldering.
The inputs to the CMOS IC are
protected against static discharge
and input current latchup. How-
ever, for best results standard
CMOS handling precautions
should be used. Prior to use, the
HDLX-2416 should be stored in
anti-static tubes or 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 charge build-up.
Input current latchup is caused
when the CMOS inputs are sub-
jected either to 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
connected either to ground or to
V
DD
. Voltages should not be
applied to the inputs until V
DD
has
been applied to the display.
Transient input voltages should be
eliminated.
Soldering and Post
Solder Cleaning
Instructions for the
HDLX-2416
The HDLX-2416 may be hand
soldered or wave soldered with
SN63 solder. When hand soldering
it is recommended that an elec-
tronically 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
dwell in the wave should be set
between 1 1/2 to 3 seconds for
optimum soldering. The preheat
temperature should not exceed
110°C (230°F) as measured on the
solder side of the PC board.
For further information on solder-
ing and post solder cleaning, see
Application Note 1027,
Soldering
LED Components.
Figure 4. Intensity Modulation Control
Using an Astable Multivibrator
(reprinted with permission from
Electronics
magazine, Sept. 19, 1974,
VNU Business pub. Inc.)
Figure 4 shows a circuit designed
to dim the display from 98% to 2%
by pulse width modulating the BL
input. A logarithmic or a linear
potentiometer may be used to
adjust the display intensity.
However, a logarithmic potenti-
ometer matches the response of
the human eye and therefore
provides better resolution at low
intensities. The circuit frequency
should be designed to operate at
10 kHz or higher. Lower frequen-
cies may cause the display to
flicker.
Extended Function
Disable
Extended Function Disable (bit D
6
of the Control Register) disables
the extended blanking and dim-
ming functions in the HDLX-2416.
If the Extended Function Disable
is a logic 1, the internal brightness
control, Master Blank, and Digit
Blank Disable bits are ignored.
However the BL input and Cursor
control are still active. This allows
downward compatibility to the
HPDL-2416.
Contrast Enhancement
The objective of contrast enhance-
ment is to provide good readabil-
ity in the end user’s ambient
lighting conditions. The concept is
to employ both luminance and
chrominance contrast techniques.
These enhance readability by
having the OFF-dots blend into the
display background and the ON-
dots vividly stand out against the
same background. For additional
information on contrast enhance-
ment, see Application Note 1015.
AGILENT [ AGILENT TECHNOLOGIES, LTD. ]
