11

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-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

subjected either to a voltage below ground (Vin < ground)

high current is forced into the input. To prevent input

current latchup and ESD damage, unused inputs should

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 soldering it is recommend-

ed 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 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 soldering and post solder

cleaning, see Application Note 1027, Soldering LED

Components.

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. 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 frequencies may cause the display

to flicker.

Extended Function Disable

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. Backfill epoxy environmentally seals the

display package. This package construction makes the

display highly tolerant to temperature cycling and allows

wave soldering.

555

BL

(PIN 18)

10 kHz

OUTPUT

1 k

250 k

LOG

400 pF

6

21

1 k

1N914

7

8

4

3