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TELCOM SEMICONDUCTOR, INC.

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TC826

A/D CONVERTER WITH BAR GRAPH DISPLAY OUTPUT

FEATURES

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Bipolar A/D Conversion

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2.5% Resolution

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Direct LCD Display Drive

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‘Thermometer’ Bar or Dot Display

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40 Data Segments Plus Zero

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Overrange Plus Polarity Indication

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Precision On–Chip Reference ................ 35ppm/

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Differential Analog Input

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Low Input Leakage .......................................... 10pA

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Display Flashes on Overrange

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Display Hold Mode

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Auto–Zero Cycle Eliminates Zero Adjust

Potentiometer

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9V Battery Operation

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Low Power Consumption ............................ 1.1mW

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20mV to 2.0 V Full–Scale Operation

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Non–Multiplexed LCD Drive for Maximum

Viewing Angle

GENERAL DESCRIPTION

In many applications a graphical display is preferred

over a digital display. Knowing a process or system oper-

ates, for example, within design limits is more valuable than

a direct system variable readout. A bar or moving dot display

supplies information precisely without requiring further inter-

pretation by the viewer.

The TC826 is a complete analog–to–digital converter

with direct liquid crystal (LCD) display drive. The 40 LCD

data segments plus zero driver give a 2.5% resolution bar

display. Full–scale differential input voltage range extends

from 20mV to 2V. The TC826 sensitivity is 500

µv. A low drift

35 ppm/

°C internal reference, LCD backplane oscillator and

driver, input polarity LCD driver, and overrange LCD driver

make designs simple and low cost. The CMOS design

required only 125

µA from a 9V battery. In +5V systems a

TC7660 DC to DC converter can supply the –5V supply. The

differential analog input leakage is a low 10pA.

Two display formats are possible. The BAR mode

display is like a ‘thermometer’ scale. The LCD segment

driver that equals the input plus all below it are on. The DOT

mode activates only the segment equal to the input. In either

mode the polarity signal is active for negative input signals.

An overrange input signal causes the display to flash and

activates the overrange annunciator. A hold mode can be

selected that freezes the display and prevents updating.

The dual slope integrating conversion method with

auto–zero phase maximizes noise immunity and eliminates

zero–scale adjustment potentiometers. Zero–scale drift is a

low 5

µV/°C. Conversion rate is typically 5 per second and

is adjustable by a single external resistor.

A compact, 0.5" square, flat package minimizes PC

board area. The high pin count LSI package makes multi-

plexed LCD displays unnecessary. Low cost, direct drive

LCD displays offer the widest viewing angle and are readily

available. A standard display is available now for TC826

prototyping work.

PIN CONFIGURATION

ORDERING INFORMATION

Part No.

Package

Temperature

TC826CBU

64–Pin PFP

0

°C to +70°C

TC826-6

11/6/96

30

29

28

50

51

25

52

24

53

23

54

22

55

21

56

20

57

19

58

18

59

17

60

31

5

6

7

8

9

10

11

12

13

14

15

41

40

39

38

37

36

35

34

33

47

46

62

63

64

49

26

1

2

3

4

45

44

43

42

BAR 30

BAR 29

BAR 28

BAR 27

BAR 26

BAR 25

BAR 24

BAR 23

BAR 22

BAR 21

BAR 20

BAR 19

BAR 18

NC

16

48

32

61

OSC1

BP

ANALOG

COMMON

+IN

– IN

REF IN

VDD

VSS

OSC2

BAR 0

C

+

REF

C

–

REF

VBUF

CAZ

VINT

NC

BAR 17

BAR 16

TC826CBU

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