3-257

TELCOM SEMICONDUCTOR, INC.

7

6

5

4

3

1

2

8

V

–

ANALOG

COMMON

TC7136

TC7136A

VREF

+

32

35

36

26

240 k

Ω

10 k

Ω

VREF

–

VREF

1

+

9V

SET VREF = 1/2 VFULL SCALE

V

+

analog common is a very stable potential with excellent

temperature stability (typically 35 ppm/

°c). for TC7136A

This potential can be used to generate the TC7136A's

reference voltage. An external voltage reference will be

unnecessary in most cases because of the 35 ppm/

°C

temperature coefficient. See TC7136A Internal Voltage

Reference discussion.

TEST (Pin 37)

used as the negative power supply connection for external

CMOS logic. The TEST pin is tied to the internally-generated

negative logic supply through a 500

Ω resistor. The TEST pin

load should not be more than 1 mA. See the Applications

Section for additional information on using TEST as a

negative digital logic supply.

minus sign will be activated. DO NOT OPERATE IN THIS

MODE FOR MORE THAN SEVERAL MINUTES. With TEST

which will destroy the LCD.

TC7136A Internal Voltage Reference

The TC7136 analog common voltage temperature sta-

bility has been significantly improved (Figure 9). The "A"

version of the industry-standard TC7136 device allows

users to upgrade old systems and design new systems

without external voltage references. External R and C val-

ues do not need to be changed; however, noise perfor-

Capacitor section.) Figure 10 shows analog common sup-

plying the necessary voltage reference for the TC7136/A.

Figure 9. Analog Common Temperature Coefficient

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 external

CMOS gate segment drivers. LCD annunciators for decimal

points, low battery indication, or function indication may be

added without adding an additional supply. No more than 1

mA should be supplied by the TEST pin: its potential is

TYPICAL

GUARANTEED

MAXIMUM

TYPICAL

GUARANTEED

MAXIMUM

TYPICAL

NO MAXIMUM

SPECIFIED

200

180

160

140

120

100

80

60

40

20

0

TC7136

TC7136A

ICL7136

Figure 10. TC7136A Internal Voltage Reference Connection

APPLICATIONS INFORMATION

Liquid Crystal Display Sources

Several manufacturers supply standard LCDs to inter-

face with the TC7136A 3-1/2 digit analog-to-digital con-

verter.

Representative

Manufacturer

Address/Phone

Crystaloid

5282 Hudson Dr.

C5335, H5535,

Electronics

Hudson, OH 44236

T5135, SX440

216-655-2429

AND

720 Palomar Ave.

FE 0201, 0501

Sunnyvale, CA 94086

FE 0203, 0701

408-523-8200

FE 2201

VGI, Inc.

1800 Vernon St. Ste. 2

I1048, I1126

Roseville, CA 95678

916-783-7878

Hamlin, Inc.

612 E. Lake St.

3902, 3933, 3903

Lake Mills, WI 53551

414-648-2361

LOW POWER, 3-1/2 DIGIT

ANALOG-TO-DIGITAL CONVERTERS

TC7136

TC7136A