3-217

TELCOM SEMICONDUCTOR, INC.

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TC7126

TC7126A

3-1/2 DIGIT ANALOG-TO-DIGITAL CONVERTERS

FEATURES

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Low Temperature Drift Internal Reference

TC7126 ....................................... 80 ppm/

TC7126A ..................................... 35 ppm/

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Guaranteed Zero Reading With Zero Input

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Low Noise .................................................... 15

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High Resolution .............................................. 0.05%

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Low Input Leakage Current ...................... 1 pA Typ

10 pA Max

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Precision Null Detectors With True Polarity at

Zero

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High-Impedance Differential Input

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Convenient 9V Battery Operation With

Low Power Dissipation ........................ 500

900

TYPICAL APPLICATIONS

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Thermometry

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Bridge Readouts: Strain Gauges, Load Cells, Null

Detectors

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Digital Meters and Panel Meters

— Voltage/Current/Ohms/Power, pH

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Digital Scales, Process Monitors

GENERAL DESCRIPTION

The TC7126A is a 3-1/2 digit CMOS analog-to-digital

converter (ADC) containing all the active components nec-

essary to construct a 0.05% resolution measurement sys-

tem. Seven-segment decoders, digit and polarity drivers,

voltage reference, and clock circuit are integrated on-chip.

The TC7126A directly drives a liquid crystal display (LCD),

and includes a backplane driver.

A low-cost, high-resolution indicating meter requires

only a display, four resistors, and four capacitors. The

TC7126A's extremely low power drain and 9V battery

operation make it ideal for portable applications.

The TC7126A reduces linearity error to less than 1

count. Roll-over error (the difference in readings for equal

magnitude but opposite polarity input signals) is below

±1

count. High-impedance differential inputs offer 1 pA leak-

noise performance guarantees a "rock solid" reading, and

the auto-zero cycle guarantees a zero display reading with

a 0V input.

The TC7126A features a precision, low-drift internal

voltage reference and is functionally identical to the TC7126.

A low-drift external reference is not normally required with

the TC7126A.

ORDERING INFORMATION

PART CODE

TC7126X X XXX

A or blank*

R (reversed pins) or blank (CPL pkg only)

* "A" parts have an improved reference TC

Package Code (see below):

Package

Temperature

Code

Package

Range

CKW

44-Pin PQFP

0

°C to +70°C

CLW

44-Pin PLCC

0

°C to +70°C

CPL

40-Pin PDIP

0

°C to +70°C

IPL

40-Pin PDIP (non-A only)

– 25

°C to +85°C

+

TC7126

TC7126A

33

34

240 k

Ω

10 k

Ω

31

29

39

38

40

–

0.33

µF

0.1 µF

V

–

1

OSC

3

OSC

2

OSC

TO ANALOG COMMON

(PIN 32)

1 CONVERSION/SEC

COSC

560 k

Ω

180 k

Ω

0.15 µF

0.01 µF

ANALOG

INPUT

+

–

–

+

+

–

ANALOG

COMMON

20

21

1

SEGMENT

DRIVE

2–19

22–25

POL

BP

V

+

MINUS SIGN

BACKPLANE

28

50 pF

LCD

1 M

Ω

27

30

32

35

36

9V

+

ROSC

26

NOTE: Pin numbers refer to 40-pin DIP.

40-Pin Plastic DIP

44-Pin Plastic Quad Flat

Package Formed Leads

44-Pin Plastic Chip

Carrier PLCC

AVAILABLE PACKAGES

TYPICAL OPERATING CIRCUIT

TC7126/A-8 11/6/96