11
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-3416 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 (Vin < ground)
or to a voltage higher than V
DD
(Vin > 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-3416
The HDLX-3416 may be hand soldered or wave soldered
with SN63 solder. When hand solder ing it is recommend-
ed that an electronically temperature con trolled 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 ux 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
1½ to 3 seconds for optimum soldering. The preheat tem-
perature 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.
Contrast Enhancement
The objective of contrast enhance ment is to provide good
read abil ity in the end user’s ambient lighting conditions.
The concept is to employ both luminance and chromi-
nance 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 back-
ground. For addi tional information on contrast enhance-
ment, see Application Note 1015.
Figure 4. Intensity modulation control using an astable multivibrator
(reprinted with permission from Electronics magazine, Sept. 19, 1974, V
NU 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 log-
arithmic or a linear potentiometer may be used to adjust
the display intensity. However, a logarithmic potentio-
meter 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 fre quencies may cause the display
to icker.
Extended Function Disable
Extended Function Disable (bit D
6
of the Control Register)
disables the extended blanking and dimming functions in
the HDLX-3416. 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.
Mechanical and Electrical Considerations
The HDLX-3416 is a 22 pin DIP package that can be stacked
horizontally and vertically to create arrays of any size. The
display is designed to operate continuously from -40°C to
+85°C for all possible input conditions.
The HDLX-3416 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. Back ll epoxy environmentally seals the
display package. This package construc tion makes the
display highly tolerant to temperature cycling and allows
wave soldering.
+ V
DD
555
BL
(PIN 18)
10 kHz
OUTPUT
1 k
250 k
LOG
400 pF
6
21
1 k
1N914
7
8
4
3
