The inputs to the CMOS IC are protected against static

discharge and input current latchup. However, 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

when a high current is forced into the input. To prevent

input current latchup and ESD damage, unused inputs

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 recom-

mended that an electronically temperature controlled

and securely grounded soldering iron be used. For best

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 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 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 additional information on contrast enhance-

ment, see Application Note 1015.

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 po-

tentiometer 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 frequencies may cause the display

to flicker.

Extended Function Disable

disables the extended blanking and dimming 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.

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

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 construction makes the

display highly tolerant to temperature cycling and allows

wave soldering.

Figure 4. Intensity modulation control using an astable multivibrator

(reprinted with permission from Electronics magazine, Sept. 19, 1974,

VNU Business pub. Inc.)

+ VDD

555

BL

(PIN 18)

10 kHz

OUTPUT

1 k

250 k

LOG

400 pF

6

2

1

1 k

1N914

7

8

4

3