TC7126 datasheet(16/26 Pages) MICROCHIP

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TC7126/A

DS21458C-page 16

8.0

TYPICAL APPLICATIONS

8.1

Liquid Crystal Display Sources

Several manufacturers supply standard LCDs to inter-

face with the TC7126A, 3-1/2 digit analog-to-digital

converter.

Note:

Contact LCD manufacturer for full product list-

ing/specifications.

8.2

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 annunciators for

decimal points, low battery indication, or function indi-

cation may be added, without adding an additional sup-

ply. No more than 1mA should be supplied by the TEST

pin; its potential is approximately 5V below V+ (see

Figure ).

FIGURE 8-1:

Decimal Point and

Annunciator Drives

8.3

Flat Package

The TC7126 is available in an epoxy 64-pin formed

lead package. A test socket for the TC7126ACBQ

device is available:

Part Number:

IC 51-42

Manufacturer:

Yamaichi

Distribution:

Nepenthe Distribution

2471 East Bayshore, Ste. 520

Palo Alto, CA 94043

(650) 856-9332

8.4

Ratiometric Resistance

Measurements

The TC7126A’s true differential input and differential

reference make ratiometric reading possible. In a ratio-

metric operation, an unknown resistance is measured

with respect to a known standard resistance. No

accurately defined reference voltage is needed.

The unknown resistance is put in series with a known

standard and a current passed through the pair. The

voltage developed across the unknown is applied to the

input and the voltage across the known resistor is

applied to the reference input. If the unknown equals

the standard, the display will read 1000. The displayed

reading

can

determined

from

the

following

expression:

EQUATION 8-1:

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 0801

FE 0203

VGI, Inc.

1800 Vernon St., Ste. 2

Roseville, CA 95678

916-783-7878

LD-B709BZ

LD-H7992AZ

Hamlin, Inc.

612 E. Lake St.

Lake Mills,

WI 53551

414-648-2361

3902, 3933,

3903

TC7126A

V+

TEST

GND

4030

TC7126A

TEST

V+

GND

To LCD

Decimal

Point

To LCD

Decimal

Point

To LCD

Decimal

Point

Backplane

4049

Multiple Decimal Point or

Annunciator Driver

Simple Inverter for Fixed Decimal Point

or Display Annunciator

Displayed (Reading) =

RUNKNOWN

RSTANDARD

x 1000

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