3-231

TELCOM SEMICONDUCTOR, INC.

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6

5

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TC7129

FEATURES

s

Count Resolution .........................................

s

Resolution on 200 mV Scale .......................... 10

s

True Differential Input and Reference

s

Low Power Consumption ................... 500

s

Direct LCD Driver for 4-1/2 Digits, Decimal Points,

Low-Battery Indicator, and Continuity Indicator

s

Overrange and Underrange Outputs

s

Range Select Input ............................................ 10:1

s

High Common-Mode Rejection Ratio ......... 110 dB

s

External Phase Compensation Not Required

GENERAL DESCRIPTION

The TC7129 is a 4-1/2 digit analog-to-digital converter

(ADC) that directly drives a multiplexed liquid crystal dis-

play (LCD). Fabricated in high-performance, low-power

CMOS, the TC7129 ADC is designed specifically for high-

resolution, battery-powered digital multimeter applications.

The traditional dual-slope method of A/D conversion has

been enhanced with a successive integration technique to

produce readings accurate to better than 0.005% of full

scale, and resolution down to 10

µV per count.

The TC7129 includes features important to multimeter

applications. It detects and indicates low-battery condition.

A continuity output drives an annunciator on the display, and

can be used with an external driver to sound an audible

alarm. Overrange and underrange outputs and a range-

change input provide the ability to create auto-ranging

instruments. For snapshot readings, the TC7129 includes a

latch-and-hold input to freeze the present reading. This

combination of features makes the TC7129 the ideal

choice for full-featured multimeter and digital measurement

applications.

TYPICAL OPERATING CIRCUIT

4-1/2 DIGIT ANALOG-TO-DIGITAL CONVERTER

WITH ON-CHIP LCD DRIVERS

TC7129-5 10/18/96

ORDERING INFORMATION

Pin

Temperature

Part No.

Layout

Package

Range

TC7129CKW

Formed

44-Pin PQFP

0

°C to +70°C

TC7129CLW

—

44-Pin PLCC

0

°C to +70°C

TC7129CPL

Normal

40-Pin PDIP

0

°C to +70°C

TC7129

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

40

39

38

37

36

35

34

33

32

31

30

29

28

27

26

25

24

23

22

21

9V

+

TC04

LOW BATTERY

CONTINUITY

V+

5 pF

120 kHz

10 pF

0.1

µF

20

k

Ω

0.1

µF

100 k

Ω

1

µF

0.1

µF

150 k

Ω

10 k

Ω

V+

VIN

–

+

+

*

NOTE: RC network between pins 26 and 28 is not required.

*

330 k

Ω