Microchip Technology TC826CBU Datasheet

TC826

Analog-to-Digital Converter with Bar Graph Display Output

Features

• Bipolar A/D Conversion

• 2.5% Resolution

• Direct LCD Display Drive

• ‘Thermometer’ BAR or DOT Display

• 40 Data Segments Plus Zero

• Over Range Plus Polarity Indication

• PrecisionOn-Chip Reference: 35ppm/°C

• Differential Analog Input

• Low Input Leakage: 10pA

• Display Flashes on Over Range

• Display HOLD Mode

• Auto-Zero Cycle Eliminates Zero Adjust
Potentiometer

• 9V Battery Operation

• Low Power Consumption: 1.1mW

• 20mV to 2.0V Full Scale Operation

• Non-Multiplexed LCD Drive for Maximum
Viewing Angle

Device Selection Table

Part Number Package Temperature Range

TC826CBU 64-Pin PQFP 0°Cto+70°C

General Description

In many applications, a graphical display is preferred
over a digital display. Knowing a process or system
operates,forexample,within design limitsismorevalu­able than a direct system variable read out. A bar or
moving dot display supplies informationprecisely with­out requiringfurther interpretation 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 extendsfrom 20mV to2V.TheTC826 sensitivity
is 500µV. A low drift35ppm/°C internal reference,LCD
backplane oscillator and driver, input polarity LCD
driver, and over rangeLCD driver make designs simple
and low cost. The CMOS design required only 125µA
from a 9V battery.In +5V systems, a TC7660DC 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 allbelow it are on. The
DOT mode activates only the segment equal to the
input. In either mode, t he polarity signal is active for
negative input signals. An over range input signal
causesthedisplayt o flashandactivates the over range
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 5µV/°C. Conversion rate is typically
5 per second and is adjustable by a single external
resistor.

A compact, 0.5" s quare, flat package minimizes PC
board area. The high pin count LSI package makes
multiplexed LCD displays unnecessary. Low cost,
directdriveLCD displays offer the widest viewing angle
and are readily available. A standard display is avail­able now for TC826 prototypingwork.

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2002 Microchip TechnologyInc. DS21477B-page 1

TC826

Package Type

64-Pin PQFP

ANALOG

COMMON

REF IN

C

C

OSC2

BAR 0

Typical Application

NC

+IN

REF

REF

V

V

BUF

C

V

INT

V

OSC1

NC

1

2

3

-IN

4

5

+

6

-

7

DD

8

9

AZ

10

11

SS

12

13

14

BP

15

16

NC

BAR/DOT

HOLD

TEST

61

626364 49

19

BAR 3

BAR 2

BAR 1

OR

POL-

5818591760

TC826CBU

BAR 5

BAR 4

BAR 40

BAR 6

BAR 39

BAR 7

BAR 38

26

BAR 8

BAR 37

27

BAR 9

BAR 36

BAR 10

BAR 34

BAR 35

BAR 12

BAR 11

BAR 33

302928

BAR 13

BAR 32

5051255224532354225521562057

31

BAR 14

BAR 31

32

BAR 15

48

NC

47

BAR 30

46

BAR 29

45

BAR 28

44

BAR 27

43

BAR 26

42

BAR 25

41

BAR 24

40

BAR 23

39

BAR 22

38

BAR 21

37

BAR 20

36

BAR 19

35

BAR 18

34

BAR 17

33

BAR 16

1MΩ

1MΩ

1MΩ

Component

R

INT

C

INT

C

REF

C

AZ

C

INT

C

AZ

V

61

62

BAR/DOT

HOLD

R

INT

V

BUFCAZ

TC826

63

TEST

12

V

SS

V

DD

9V

2V

Full Scale

2MΩ 20kΩ 20kΩ

0.033mf 0.033mf 0.033mf

1mf 1mf 1mf

0.068mf 0.068mf 0.014mf R1 + R2 = 250kΩ

R

1

200mV

Full Scale

REFINANALOG

COMMON -IN +IN

58 2 43 60

R

2

-IN +IN

20mV

Full Scale

11109

INT

BAR 0-

BAR 40 POL-

6

C

+

REF

7

C

-

REF

13

OSC1

14

OSC2

15

BP

59

OR

Segment Drive

–OR

C

REF

1.0mf

R

OSC

430kΩ

Backplane

41 Segment LCD
Bar Graph

DS21477B-page 2

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2002 Microchip TechnologyInc.

TC826

1.0 ELECTRICAL

CHARACTERISTICS

Absolute Maximum Ratings*

Supply Voltage (V+ to V-).......................................15V

*Stresses above those listed under "Absolute Maximum
Ratings" may cause permanent damage to the device. These
are stress ratings only and functional operation of the device
at these or any other conditions above those indicated in the
operation sections of the specifications is not implied.
Exposure to Absolute Maximum Rating conditions for
extended periods may affectdevice reliability.

Analog Input Voltage(Either Input) (Note 1)... V+ to V­Power Dissipation (T

≤ 70°C)

A

64-Pin Plastic Flat Package ...............................1.14W

Operating Temperature Range:

Commercial Package (C)........................ 0°C to +70°C

StorageTemperature Range..............-65°C to +150°C

TC826 ELECTRICAL SP EC IFICATIONS

Electrical Characteristics: V

Symbol Parameter Min Typ Max Unit Test Conditions

Zero Input -0 ±0 +0 Display V
Zero Reading Dri ft — 0.2 1 µV/°C V

NL Linearity Error -1 0.5 +1 Count Max Deviation from Best Straight Line
R/O Rollover Error -1 0 +1 Count -V
EN Noise — 60 — µV
ILK InputLeakage Current — 10 20 pA V
CMRR Comm on Mode Rejection Ratio — 5 0 — µV/V VCM = ±1V

Scale Factor Temperature Coefficient — 1 — ppm/°C 0 ≤ T

V

CTC

V

COM

VSD LCD Segment Drive Voltage 4 5 6 V
VBD LCD Backplane DriveVoltage 4 5 6 V
I

DD

Note 1: Input voltagesmay exceedthe supplyvoltages when the input currentis limited to 100µA.

Analog Common Temperature
Coefficient

Analog Common Voltage 2.7 2.9 3.35 V 250kΩ betweenCommonand V

Power Supply Current — 125 175 µA

2: Static sensitivedevice. Unused devicesshould be stored in conductive material to protect devices from staticdischarge

and static fields.

3: Backplane drive is in phase with segmentdrive for ‘off’ segment and 180°C out of phase for ‘on’ segment. Frequency is

10 times conversion rate.

4: Logic input pins 58, 59, and 60 should be connected through 1MΩ series resistors to V

=9V;R

S

=430kΩ;TA= 25°C; Full Scale = 20mV, unless otherwise stated.

OSC

=0.0V

IN

=0.0V

IN

0°C ≤ T

=+V

IN

P-PVIN

— 35 100 ppm/°C 250kΩ between Common and

P-P
P-P

=0V
=0V

IN

=0V

V

IN

A

External Ref. Temperature
Coefficient = 0ppm/°C

V+, 0°C ≤ T

SS

≤ +70°C

A

IN

≤ 7+0°C

≤ +70°C

A

for logic 0.

DD



2002 Microchip TechnologyInc. DS21477B-page 3

TC826

2.0 PIN DESCRIPTION

ThedescriptionsofthepinsarelistedinTable2-1.

TABLE 2-1: PIN FUNCTION TABLE

Pin Number

(64-Pin PQFP)

1 NC Positive analog signal input.
2ANALOG

3 +IN Positive analog signal input.
4 -IN Negative analog signal input.
5 REF IN Reference voltage positiveinput. Measured relative to analog common.

6C
7C
8V

9V
10 C
11 V
12 V
13 OSC1 Oscillator resistor (R
14 OSC2 Oscillator resistor (R
15 BP LCDBackplane driver.
16 BAR 0 LCD Segment driver: Bar 0.
17 NC No connection.
18 BAR 1 LCD Segment driver: Bar 1.
19 BAR 2 LCD Segment driver: Bar 2.
20 BAR 3 LCD Segment driver: Bar 3.
21 BAR 4 LCD Segment driver: Bar 4.
22 BAR 5 LCD Segment driver: Bar 5.
23 BAR 6 LCD Segment driver: Bar 6.
24 BAR 7 LCD Segment driver: Bar 7.
25 BAR 8 LCD Segment driver: Bar 8.
26 BAR 9 LCD Segment driver: Bar 9.
27 BAR10 LCD Segment driver: Bar 10.
28 BAR 11 LCD Segment driver: Bar 11.
29 BAR12 LCD Segment driver: Bar 12.
30 BAR13 LCD Segment driver: Bar 13.
31 BAR14 LCD Segment driver: Bar 14.
32 BAR15 LCD Segment driver: Bar 15.
33 BAR16 LCD Segment driver: Bar 16.
34 BAR17 LCD Segment driver: Bar 17.
35 BAR18 LCD Segment driver: Bar 18.
36 BAR19 LCD Segment driver: Bar 19.
37 BAR20 LCD Segment driver: Bar 20.
38 BAR21 LCD Segment driver: Bar 21.
39 BAR22 LCD Segment driver: Bar 22.
40 BAR23 LCD Segment driver: Bar 23.

Symbol Description

COMMON

+ Reference capacitor connection.

REF

- Reference capacitor connection.

REF

DD

BUF

AZ
INT
SS

Establishesthe internal analog ground point.A nalog common is set to 2.9V belowthe
positivesupply COMMON by an internalzener reference circuit. The voltage difference
betweenV
inputatREFIN(Pin5).

REF IN ≈ Full Scale/2.

Positive supply terminal.
Buffer output. Integration resistor connection.
Negative comparator input. Auto-zero capacitor connection.
Integrator output.Integrationcapacitorconnection.
Negative supply terminal.

DD

and analogcommoncan be used to supply the TC826 voltagereference

) connection.

OSC

) connection.

OSC

DS21477B-page 4

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2002 Microchip TechnologyInc.

TABLE 2-1: PIN FUNCTION TABLE (CONTINUED)

Pin Number

(64-Pin PQFP)

41 BAR24 LCD Segment driver: Bar 24.
42 BAR25 LCD Segment driver: Bar 25.
43 BAR26 LCD Segment driver: Bar 26.
44 BAR27 LCD Segment driver: Bar 27.
45 BAR28 LCD Segment driver: Bar 28.
46 BAR29 LCD Segment driver: Bar 29.
47 BAR30 LCD Segment driver: Bar 30.
48 NC No connection.
49 BAR31 LCD Segment driver: Bar 31.
50 BAR32 LCD Segment driver: Bar 32.
51 BAR33 LCD Segment driver: Bar 33.
52 BAR34 LCD Segment driver: Bar 34.
53 BAR35 LCD Segment driver: Bar 35.
54 BAR36 LCD Segment driver: Bar 36.
55 BAR37 LCD Segment driver: Bar 37.
56 BAR38 LCD Segment driver: Bar 38.
57 BAR39 LCD Segment driver: Bar 39.
58 BAR40 LCD Segment driver: Bar 40.
59 OR LCDsegment driver thatindicated input out-of-rangecondition.
60 POL- LCD segment driver that indicates input signal is negative.
61 BAR/DOT

62 HOLD

63 TEST

64 NC No connection.

Symbol Description

Inputlogic signalthatselectsBARorDOTdisplay format.Normally in BAR mode.Connect
to V

through 1MΩ resistorforDOT format.

SS

Inputlogicsignal that preventsdisplay from changing.P ulled high internally to inactive
state.Connect to V

Input logic signal. Sets TC826 to BAR Display mode. BAR 0 to 40, plus OR flash on and
off.ThePOL-LCDdriver is on. Pulled high internally to inactivestate. Connectto V
1MΩ series resistor to activate.

through 1MΩ series resistor for HOLD mode operation.

SS

TC826

with

SS



2002 Microchip TechnologyInc. DS21477B-page 5

TC826

3.0 DETAILED DESCRIPTION

3.1 Dual Slope Conversion Principles

The TC826 is a dualslope,integratinganalog-to-digital
converter. The conventionaldual slope converter mea­surement cycle has two distinct phases:

• Input Signal Integration

• Reference VoltageIntegration (De-integration)
The input signal being converted is integrated for a

fixed time period (T
clock pulses. An opposite polarity constant reference
voltage is then i ntegrated until the integrator output
voltage returns to zero. The reference integration time
is directly proportional to the input signal (T
(Figure3-1).

In a simple dual slope converter, a complete conver­sion requires the integrator output to ‘ramp-up’ and
‘ramp-down’.

FIGURE 3-1: BASIC DUAL SLOPE CONVERTER

). Time is measured by counting

SI

)

RI

C

A simple mathematicalequation relates the input signal
reference voltage and integration time:

EQUATION 3-1:

t

1

INT

V

IN

∫

0

RC

Where:

= Ref erence Voltage

V

R

= Si gnal Integration Time (Fixed)

V

SI

= Ref erence Voltage I ntegration Time

T

RI

(Variable)

(t)dt =

V

RTRI

RC

Analog Input

Signal

Output

Integrator

+/–

REF

Voltage

Fixed Signal

Integrate

Time

R

Switch Driver

Polarity Control

Variable

Reference

Integrate

Time

Integrator

–

+

VIN ≈ 1/2 V

VIN ≈ 1/4 V

Comparator

–

+

Phase Control

FULL SCALE

FULL SCALE

Control

Logic

Clock

Counter

Display

DS21477B-page 6



2002 Microchip TechnologyInc.