HDLA-3416 datasheet(11/12 Pages) HP

11 / 12 page

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 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 flicker.

Extended Function

Disable

Extended Function Disable (bit

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. 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-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 >

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

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 recommended 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 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 11/

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.

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 addi-

tional information on contrast

enhancement, see Application

Note 1015.

Figure 4. Intensity Modulation Control

Using an Astable Multivibrator

(reprinted with permission from

Electronics magazine, Sept. 19, 1974,

VNU Business pub. Inc.).

+ VDD

555

(PIN 18)

10 kHz

OUTPUT

1 k

250 k

LOG

400 pF

1 k

1N914

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