TC7107 datasheet(17/26 Pages) MICROCHIP

17 / 26 page

DS21455B-page 17

TC7106/A/TC7107/A

ments (a “111” display) to worst case (a “1888” display),

the resistor will change about 230mW, while a circuit

without the resistor will change about 470mW. There-

fore, the resistor will reduce the effect of display dissi-

pation on reference voltage drift by about 50%.

The change in LED brightness caused by the resistor is

almost unnoticeable as more segments turn off. If dis-

play brightness remaining steady is very important to

the designer, a diode may be used instead of the

resistor.

FIGURE 9-4:

DIODE OR RESISTOR

LIMITS PACKAGE POWER

DISSIPATION

10.0

TYPICAL APPLICATIONS

10.1

Liquid Crystal Display Sources

Several manufacturers supply standard LCDs to inter-

face with the TC7106A 3-1/2 digit analog-to-digital

converter.

Note:

Contact LCD manufacturer for full product listing and

specifications.

10.2

Light Emitting Diode Display

Sources

Several LED manufacturers supply seven segment

digits with and without decimal point annunciators for

the TC7107A.

10.3

Decimal Point and Annunciator

Drive

The TEST pin is connected to the internally generated

digital logic supply ground through a 500

Ω resistor. The

TEST pin may be used as the negative supply for exter-

nal CMOS gate segment drivers. LCD display annunci-

ators for decimal points, low battery indication, or

function indication may be added without adding an

additional supply. No more than 1mA should be sup-

plied by the TEST pin; its potential is approximately 5V

below V+ (see Figure 10-1

FIGURE 10-1:

DECIMAL POINT DRIVE

USING TEST AS LOGIC

GROUND

Manufacturer

Address/Phone

Representative

Part Numbers*

Crystaloid

Electronics

5282 Hudson Dr.

Hudson, OH 44236

216-655-2429

C5335, H5535,

T5135, SX440

AND

720 Palomar Ave.

Sunnyvale, CA 94086

408-523-8200

FE 0201, 0701

FE 0203, 0701

FE 0501

Epson

3415 Kashikawa st.

Torrance, CA 90505

213-534-0360

LD-B709BZ

LD-H7992AZ

Hamlin, Inc.

612 E. Lake St.

Lake Mills, WI 53551

414-648-236100

3902, 3933, 3903

TP2

TP5

100

Ω

TP1

24k

Ω

0.1

µF

TP3

0.01

µF

–

0.22

µF

Display

100

+5V

Ω

-5V

150

Ω

0.47

µF

TC7107A

Ω

1N4001

5.1

Ω 1/4W

Manufacturer

Address/Phone

Display

Hewlett-Packard

Components

640 Page Mill Rd.

Palo Alto, CA 94304

LED

AND

720 Palomar Ave.

Sunnyvale, CA 94086

408-523-8200

LED

TC7106A

TEST

V+

GND

To LCD

Decimal

Point

To LCD

Decimal

Point

To LCD

Backplane

4049

TC7106A

Decimal

Point

Select

V+

TEST

GND

4030

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