Microchip Technology TC811CPL, TC811CKW Datasheet

3-1/2 Digit Analog-To-Digital Converter with Hold and
Differential Reference Inputs

TC811

FEATURES

■ Differential Reference Input

■ Display Hold Function

■ Fast Over-Range Recovery, Guaranteed Next

Reading Accuracy

■ Low Temperature Drift Internal

Reference ....................................... 35ppm/°C (Typ)

■ Guaranteed Zero Reading With Zero Input

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

■ High Resolution (0.05%) and Wide Dynamic

Range (72 dB)

■ High Impedance Differential Input

■ Low Input Leakage Current .................... 1pA (Typ)

■ Direct LCD Drive -No External Components

■ Precision Null Detection with True Polarity at Zero

■ Crystal Clock Oscillator

■ Available in DIP, Compact Flat Package or PLCC

■ Convenient 9V Battery Operation with

Low Power Dissipation (600µA Typical, 1mW
Maximum)

FUNCTIONAL BLOCK DIAGRAM

µV

p-p

10pA Max

TYPICAL APPLICATIONS

■ Thermometry

■ Digital Meters

— Voltage/Current/Power
— pH Measurement
— Capacitance/Inductance
— Fluid Flow Rate/Viscosity
— Humidity
— Position

■ Panel Meters

■ LVDT Indicators

■ Portable Instrumentation

■ Digital Scales

■ Process Monitors

■ Gaussometers

■ Photometers

ORDERING INFORMATION

Temp. Max V

Part No. Package Range Temp. Co.

TC811CKW 44-Pin PQFP
TC811CPL

40-Pin Plastic DIP 0°C to +70°C

0°C to +70°C

75 ppm/°C
75 ppm/°C

REF

V

ANALOG

COMMON

V

TYPICAL SEGMENT OUTPUT

0.5mA

2mA

INTERNAL DIGITAL GROUND

TC811CPL

C

C

V

+

REF

DE (+)

REF

ZI & A/Z

DE
(–)DE(+)

AZ & DE (±)

V

DE (–)

–

REF

–

C

REF

33

ZI &
A/Z

V+– 3.0V

26

–

V

+

C

REF

10
µA

31

+
IN

INT

A/Z

32

30

–
IN

INT

R

INT

V

–
+

BUFF

ZI

–
+

28

LOW
TEMPCO
V

REF

V

V

+

AZ

+

29

38

INTEGRATOR

+

A/Z

OSC

10pF

V

27343635

–

COMPARATOR

FROM COMPARATOR OUTPUT
CLOCK

40

1

22MΩ

470k

V

SEGMENT

OUTPUT

C

INT

INT

DIGITAL

SECTION

+
–

TO SWITCH DRIVERS

39

OSC

2

20pF

+

TO

THOUSANDS

f

OSC

INTERNAL DIGITAL GOUND

V

4

+

7 SEGMENT

DECODE

HUNDREDS

LCD DISPLAY

LCD SEGMENT DRIVERS

7 SEGMENT

DECODE

DATA LATCH

TENS UNITS

CONTROL LOGIC

V

TH

= 1V

7 SEGMENT

DECODE

≈70kΩ

1
HLDR

BACKPLANE

21

200

6.2V

Ω

500

38

+

V

TEST

26

–

V

© 2001 Microchip Technology Inc. DS21472A

TC811-7 11/5/96

TC811

3-1/2 Digit Analog-To-Digital Converter with

Hold and Differential Reference Inputs

GENERAL DESCRIPTION

The TC811 is a low power, 3-1/2 digit, LCD display
analog-to-digital converter. This device incorporates both a
display hold feature and differential reference inputs. A
crystal oscillator, which only requires two pins, permits
added features while retaining a 40-pin package. An addi­tional feature is an "Integrator Output Zero" phase which
guarantees rapid input overrange recovery.

The TC811 display hold (HLDR) function can be used to
"freeze" the LCD display. The displayed reading will remain
indefinitely as long as HLDR is held high. Conversions
continue but the output data display latches are not updated.
The TC811 also includes a differential reference for easy
ratiometric measurements. Circuits which use the
7106/26/36 can easily be upgraded to include the hold
function with the TC811.

The TC811 has an improved internal zener reference
voltage circuit which maintains the Analog Common tem­perature drift to 35ppm/°C (typical) and 75ppm/°C (maxi­mum). This represents an improvement of two to four times
over similar 3-1/2 digit converters, eliminating the need for
a costly, space consuming external reference source.

The TC811 limits linearity error to less than one count on
both the 200mV and the 2.00V full-scale ranges. Rollover
error—the difference in readings for equal magnitude but
opposite polarity input signals—is below ±1 count. High
impedance differential inputs offer 1pA leakage currents
and a 10
mance guarantees a “rock solid” reading. The Auto Zero
cycle guarantees a zero display readout for a zero volt input.

devices for a 3-1/2 digit analog to digital converter to directly
drive an LCD display. On-board oscillator, precision voltage
reference and display segment and backplane drivers sim-

12

Ω input impedance. The 15µV

noise perfor-

p-p

The single chip CMOS TC811 incorporates all the active

plify system integration, reduce board space requirements
and lower total cost. A low cost, high resolution (0.05%)
indicating meter requires only a TC811, an LCD display, five
resistors, six capacitors, a crystal, and a 9V battery. Com­pact, hand held multimeter designs benefit from the Micro­chip Semiconductor small footprint package option.

The TC811 uses a dual slope conversion technique
which will reject interference signals if the converters inte­gration time is set to a multiple of the interference signal
period. This is especially useful in industrial measurement
environments where 50, 60 and 400Hz line frequency sig­nals are present.

ABSOLUTE MAXIMUM RATINGS*

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

Analog Input voltage (Either Input)1.....................V+ to V

Reference Input Voltage ...................................... V+ to V

Clock Input ...................................................... TEST to V

Power Dissipation2 (TA ≤ 70°C)

44-Pin Flat Package .........................................1.00W

40-Pin Plastic DIP.............................................1.23W

Operating Temperature Range

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

Industrial Package (I)........................– 25°C to +85°C

Storage Temperature Range ................– 65°C to +150°C

Lead Temperature (Soldering, 10 sec) .................+300°C

*Static-sensitive device. Unused devices must be stored in conductive

material. Protect devices from static discharge and static fields. 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
affect device reliability.

–
–
+

ELECTRICAL CHARACTERISTICS: V

Supply

= 9V, f

= 32.768kHz, and TA = 25°C, unless otherwise noted.

CLOCK

Symbol Parameter Test Conditions Min Typ Max Unit
Input

— Zero Input Reading VIN = 0V – 000.0 ±000.0 +000.0 Digital

VFS = 200mV Reading
— Zero Reading Drift VIN = 0V, 0°C ≤ TA ≤ 70°C — 0.2 1 µV/°C
— Ratiometric Reading VIN = V

NL Linearity Error VFS = 200mV or 2.000V – 1 ±0.2 +1 Counts
E

R

e

N

I

L

CMRR Common-Mode Rejection VCM = ±1V, VIN = 0V, — 50 — µV/V

TC811-7 11/5/96

Roll Over Error VIN– = VIN+ ≈ 200mV – 1 ±0.2 +1 Counts
Noise VIN = 0V, VFS = 200mV — 15 — µV
Input Leakage Current VIN = 0V — 1 10 pA

VFS = 200mV

REF

, V

= 100mV 999 999/1000 1000 Digital

REF

2

© 2001 Microchip Technology Inc. DS21472A

Reading

P-P

3-1/2 Digit Analog-To-Digital Converter with
Hold and Differential Reference Inputs

TC811

ELECTRICAL CHARACTERISTICS: V

Supply

= 9V, f

= 32.768kHz, and TA = 25°C, unless otherwise noted.

CLOCK

Symbol Parameter Test Conditions Min Typ Max Unit

TC

SF

Scale Factor Temperature VIN = 199mV, 0°C ≤ TA ≤ 70°C — 1 5 ppm/°C
Coefficient (ext. V

tc = 0ppm)

REF

Analog Common Section

V

CTC

V

C

Analog Common 250KΩ from V+ to Analog Common — — — —
Temperature Coefficient 0°C ≤ T

≤ 70°C————

A

"C" Commercial — 35 75 ppm/°C
"I" Industrial — 35 100 ppm/°C

Analog Common Voltage 250kΩ from V+ to Analog Common 2.7 3.05 3.35 Volts

Hold Pin Input Section

Input Resistance Pin 1 to Pin 37 — 70 — kΩ

V

IL

V

IH

LCD Drive Section

V

SD

V

SD

Input Low Voltage Pin 1 — — Test +1.5 V
Input High Voltage Pin 1 V+ – 1.5 — — V

3

LCD Segment Drive Voltage V+ to V– = 9V 4 5 6 V
LCD Backplane Drive Voltage V+ to V– = 9V 4 5 6 V

P-P
P-P

Power Supply

I

SUP

NOTES: 1. Input voltages may exceed supply voltages when input current is limited to 100µA.

2. Dissipation rating assumes device is mounted with all leads soldered to a printed circuit board.

3. Backplane drive is in phase with the segment drive for "segment off" 180° out of phase for "segment on." Frequency is 20 times the

Power Supply Current VIN = 0V, V+ to V– = 9V — — — —

f

= 16kHz — 70 100 µA

OSC

f

= 48kHz — 90 125 µA

OSC

conversion rate. Average DC component is less than 50mV.

PIN CONFIGURATIONS

HLDR

D
C
B

1's

A

F
G
E
D
C
B

10's

A

F
E
D

B

100's

1000's

(MINUS SIGN)

F
E

AB

POL

1

NORMAL PIN

2

CONFIGURATION

1

3

1

4

1

5

1

6

1

7

1

8

1
2
2

2
2
2
2
3
3
3
3

4

NC = NO INTERNAL CONNECTION

9
10
11
12
13
14
15
16

17
18
19
20

TC811CPL

(40-PIN PDIP)

40
39
38
37
36
35
34
33
32
31
30
29

28

27
26
25
24
23
22
21

OSC

1

OSC

2

+

V
TEST

+

V

REF

+

C

REF

–

C

REF

–

V

REF
ANALOG
COMMON

+

V

IN

–

V

IN

C

AZ
V

BUFF

V

INT

–

V

G

10's

2

C

3

100's

A

3

G

3

BP
(BACKPLANE)

TEST

V

OSC
OSC

HLDR

+

+

REF

REF

C

V

44 43 42 41 39 3840

1

NC

2

NC

3

+

4

NC

5

6

2

7

1

8

D

9

1

10

C

1

11

B

1

12 13 14 15 17 18

1F1G1E1

A

–

REF

C

–

REF

COM

V

TC811CKW

16

D2C2B2A

+

IN

V

(PQFP)

–

IN

V

C

37AZ36

19 20 21 22

2F2E2

BUFF35INT

–

VVV

34

33

NC

32

G

2

C

31

3

30

A

3

29

G

3

BP

28

POL

27
26

AB

4

E

25

3

F

24

3

23

B

3

3

D

© 2001 Microchip Technology Inc. DS21472A

3

TC811-7 11/5/96

TC811

PIN DESCRIPTION

Pin No.
40-Pin Plastic DIP Symbol Description

1 HLDR Hold pin, logic 1 holds present display reading.
2D1Activates the D section of the units display.
3C1Activates the C section of the units display.
4B1Activates the B section of the units display.
5A1Activates the A section of the units display.
6F1Activates the F section of the units display.
7G1Activates the G section of the units display.
8E1Activates the E section of the units display.
9D2Activates the D section of the tens display.
10 C
11 B
12 A
13 F
14 E
15 D
16 B
17 F
18 E
19 AB

2
2
2

2

2
3
3

3

3

4

20 POL Activates the negative polarity display.
21 BP Backplane drive output.
22 G
23 A
24 C
25 G
26 V
27 V
28 V
29 C
30 V
31 V

3
3
3
2

–

INT

BUFF

AZ

–

IN

+

IN

32 COM Analog Common: Internal zero reference.
33 V

34 C
35 C
36 V

–

REF

–

REF

+

REF

+

REF

37 TEST All LCD segment test when pulled high (V+).
38 V
39 OSC
40 OSC

+

2
1

Activates the C section of the tens display.
Activates the B section of the tens display.
Activates the A section of the tens display.
Activates the F section of the tens display.
Activates the E section of the tens display.
Activates the D section of the hundreds display.
Activates the B section of the hundreds display.
Activates the F section of the hundreds display.
Activates the E section of the hundreds display.
Activates both halves of the 1 in the thousands display.

Activates the G section of the hundreds display.
Activates the A section of the hundreds display.
Activates the C section of the hundreds display.
Activates the G section of the tens display.
Negative power supply voltage.
Integrator output, connection for C
Buffer output, connection for R
Integrator input, connection for CAZ.
Analog input low.
Analog input high.

Reference input low.
Negative connection for reference capacitor.
Positive connection for reference capacitor.
Reference input high.

Positive power supply voltage.
Crystal oscillator output.
Crystal oscillator input.

3-1/2 Digit Analog-To-Digital Converter with

Hold and Differential Reference Inputs

.

INT

.

INT

TC811-7 11/5/96

4

© 2001 Microchip Technology Inc. DS21472A

3-1/2 Digit Analog-To-Digital Converter with
Hold and Differential Reference Inputs

TC811

0.1µF

33

+

ANALOG

INPUT

–

1MΩ

0.01µF

180kΩ

0.068µF

35

34

+

C

C

REF

REF

31

+

V

IN

–

30

V

TC811

IN

ANALOG

32

COMMON

28

V

BUFF

0.47

µF

29

C

AZ

27

V

INT

OSC

2

39 40

22MΩ

470k

20pF

+

V

9–19

22–25

POL

HLDR

V

V

OSC

BP

V

+
REF

–

REF

V

+

–

1

SEGMENT
DRIVE

20

MINUS SIGN

21
38

1
36

33
26

10pF

TO ANALOG COMMON
(PIN 32)

LCD

BACKPLANE

240kΩ

+

10k

Ω

2 CONVERSION/SEC

+

V

9V

Figure 1. Typical Operating Circuit

GENERAL THEORY OF OPERATION
Dual-Slope Conversion Principles

(All Pin Designations Refer to 40-Pin DIP Package)

The TC811 is a dual slope, integrating analog-to-digital
converter. An understanding of the dual slope conversion
technique will aid the user in following the detailed TC811
theory of operation following this section. A conventional
dual slope converter measurement cycle has two distinct
phases:

1) Input Signal Integration

2) Reference Voltage Integration (Deintegration)

Referring to Figure 2, the unknown input signal to be
converted is integrated from zero for a fixed time period
(T

), measured by counting clock pulses. A constant

INT

reference voltage of the opposite polarity is then integrated
until the integrator output voltage returns to zero. The
reference integration (deintegration) time (T
directly proportional to the unknown input voltage (VIN).

In a simple dual slope converter, a complete conversion
requires the integrator output to “ramp-up” from zero and
“ramp-down” back to zero. A simple mathematical equation
relates the input signal, reference voltage and integration
time:

t

1 V

R

INT CINT

INT

VIN(t) dt =

∫

R

0

REF tDEINT

INT CINT

DEINT

) is then

ANALOG

INPUT

SIGNAL

+/–

REF

VOLTAGE

OUTPUT

INTEGRATOR

FIXED

SIGNAL

INTEGRATE

TIME

INTEGRATOR

SWITCH
DRIVER

POLARITY CONTROL

DISPLAY

VARIABLE
REFERENCE
INTEGRATE
TIME

Figure 2. Basic Dual Slope Converter

30

20

10

NORMAL MODE REJECTION (dB)

0

0.1/T 1/T 10/T
INPUT FREQUENCY

Figure 3. Normal-Mode Rejection of

Dual Slope Converter

For a constant V

VIN = V

REF

[

INT

t

:

DEINT

t

INT

C

PHASE
CONTROL

V

≈

IN

FULL SCALE

1.2 V

≈

IN

COMPARATOR

–

+

CONTROL

LOGIC

COUNTER

FULL SCALE

–

+

V
V

T = MEASUREMENT PERIOD

]

CLOCK

where:

V

= Reference voltage

REF

t

= Integration Time

INT

t

= Deintegration Time

DEINT

© 2001 Microchip Technology Inc. DS21472A

5

TC811-7 11/5/96