TC7136_技术文档

TC7136/TC7136A

Low Power 3-1/2 Digit Analog-to-Digital Converter

Features

General Description

• Fast Over Range Recovery, Ensured First Reading

Accuracy

The TC7136 and TC7136A are low power, 3-1/2 digit

with liquid crystal display (LCD) drivers and analog-to-

digital converters. These devices incorporate an "inte-

grator output zero" phase, which enables over range

recovery. The performance of existing TC7126,

TC7126A and ICL7126 based systems may be

upgraded with minor changes to external, passive

components.

• Low Temperature Drift Internal Reference

- TC7136: 70ppm/°C (Typ.)

- TC7136A: 35ppm/°C (Typ.)

• Zero Reading with Zero Input

• Low Noise: 15µV

P-P

• High Resolution: 0.05%

The TC7136A has an improved internal zener refer-

ence voltage circuit which maintains the analog com-

mon temperature drift to 35ppm/°C (typical) and

75ppm/°C (maximum). This represents an improve-

ment of two to four times over similar 3-1/2 digit con-

verters. The costly, space consuming external

reference source may be removed.

• Low Input Leakage Current: 1pA (Typ.)/10pA (Max.)

• Precision Null Detectors with True Polarity at Zero

• High-Impedance Differential Input

• Convenient 9V Battery Operation with Low Power

Dissipation: 500µW (Typ.)/900µW (Max.)

The TC7136 and TC7136A limit linearity error to less

than 1 count on 200mV or 2V full scale ranges. The roll-

over error (the difference in readings for equal magni-

tude, but opposite polarity input signals) is below ±1

count. High-impedance differential inputs offer 1pA

leakage currents and a 10 Ω input impedance. The

differential reference input allows ratiometric measure-

ments for ohms or bridge transducer measurements.

Applications

• Thermometry

• Bridge Readouts: Strain Gauges, Load Cells,

Null Detectors

12

• Digital Meters: Voltage/Current/Ohms/Power, pH

• Digital Scales, Process Monitors

• Portable Instrumentation

The 15µV

noise performance ensures a "rock solid"

P-P

reading. The auto-zero cycle enables a zero display

readout for a 0V input.

Device Selection Table

Temperature

Part Number

Package

Range

TC7136 CPI

TC7136 CKW

TC7136 CLW

TC7136A CPI

TC7136A CKW

TC7136A CLW

40-Pin PDIP

44-Pin PQFP

44-Pin PLCC

40-Pin PDIP

44-Pin PQFP

44-Pin PLCC

0°C to +70°C

2002 Microchip Technology Inc.

DS21461B-page 1

TC7136/TC7136A

Package Type

44-Pin PLCC

44-Pin PQFP

6

5

4

3

2

1

44 43 42 41 40

44 43 42 41 40 39 38 37 36 35 34

33

1

2

3

4

NC

F

G

E

7

8

39

38

37

36

35

34

33

32

31

30

29

REF LO

1

32 G

2

3

C

+

1

REF

C

31

TEST

OSC3

NC

C

-

9

1

REF

ANALOG

COMMON

30 A

D

10

2

29

28

27

26

25

24

23

G

5

6

3

TC7136CLW

TC7136ACLW

C

11

12

13

14

15

16

17

IN HI

2

TC7136CKW

TC7136ACKW

BP

OSC2

OSC1

V+

NC

POL

7

B

2

IN LO

AZ

AB

4

8

A

2

D

1

E

3

9

F

2

BUFF

INT

F

3

10

11

C

1

E

2

B

3

B

1

D

3

V-

25 26 27 28

18 19 20 21 22 23 24

19 20 21 22

12 13 14 15 16 17 18

40-Pin PDIP

OSC1

OSC2

1

2

40 OSC1

1

2

40

39

38

37

36

35

34

33

32

31

30

29

28

27

26

25

24

23

22

21

V+

Normal Pin

Configuration

Reverse Pin

Configuration

D

1

D

1

39

38

37

36

35

34

33

32

31

30

29

28

27

26

25

24

23

22

21

OSC2

C

1

C

1

3

OSC3

TEST

OSC3

TEST

B

1

4

B

1

V

+

-

A

1

A

1

5

1's

V

+

-

REF

1's

REF

F

1

F

1

V

C

6

REF

+

-

G

1

G

1

C

+

7

REF

C

TC7136RCPL

TC7136ARCPL

E

1

E

1

-

8

REF

TC7136CPL

TC7136ACPL

ANALOG

COMMON

ANALOG

COMMON

9

D

2

V

+

10

11

12

13

14

15

16

17

18

19

20

10

11

12

13

14

15

16

17

18

19

20

C

2

V

+

IN

2

IN

V

-

B

2

V

-

IN

2

IN

10's

C

A

C

V

A

2

AZ

2

AZ

V

F

2

BUFF

2

BUFF

INT

V

E

2

V

INT

2

D

V-

G

V-

D

3

B

3

G

2

3

2

100's

C

3

F

3

C

3

100's

A

3

A

E

3

G

3

AB

1000's

G

1000's

4

3

POL

(MINUS SIGN)

POL

(Minus Sign)

BP

(Backplane)

BP

(Backplane)

NC = No Internal Connection

DS21461B-page 2

2002 Microchip Technology Inc.

TC7136/TC7136A

Typical Application

0.1µF

33

34

C

LCD

+

C

-

REF

1MΩ

31

9-19

22-25

Segment

Drive

+

V

+

IN

Analog

Input

–

TC7136

TC7136A

0.01µF

20

30

32

POL

BP

V

-

IN

Minus Sign

21

1

Backplane

ANALOG

COMMON

V+

28

V

240kΩ

BUFF

+

9V

0.47

180kΩ

0.15µF

36

µF

V

+

REF

29

10kΩ

C

AZ

35

26

V

-

REF

27

V

INT

V-

1 Conversion/Sec

OSC2 OSC3 OSC1

C

39

38

40

OSC

To Analog Common (Pin 32)

50pF

R

OSC

560kΩ

2002 Microchip Technology Inc.

DS21461B-page 3

TC7136/TC7136A

Functional Block Diagram

DS21461B-page 4

2002 Microchip Technology Inc.

TC7136/TC7136A

*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.

1.0

ELECTRICAL

CHARACTERISTICS

Absolute Maximum Ratings*

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

Analog Input Voltage (Either Input) (Note 1)... V+ to V-

Reference Input Voltage (Either Input)............ V+ to V-

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

Package Power Dissipation (T ≤ 70°C) (Note 2):

A

Plastic DIP ...................................................1.23W

Plastic Quad Flat Package ..........................1.00W

PLCC ...........................................................1.23W

Operating Temperature Range:

C Devices.......................................... 0°C to +70°C

I Devices ........................................ -25°C to +85°C

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

TC7136 AND TC7136A ELECTRICAL SPECIFICATIONS

Electrical Characteristics: V_S= 9V, f_CLK= 16kHz, and T_A= +25°C, unless otherwise noted.

Symbol

Input

Parameter

Min

Typ

Max

Unit

Test Conditions

Zero Input Reading

-000.0

±000.0

+000.0

Digital V_IN= 0V, Full Scale = 200mV

Reading

Zero Reading Drift

—

0.2

1

µV/°C V_IN= 0V, 0°C ≤ T_A≤ +70°C

Ratiometric Reading

999

999/1000

1000

Digital V_IN= V_REF, V_REF= 100mV

Reading

NL

Non-Linearity Error

—

1

±0.2

Count Full Scale = 20mV or 2V Max.

Deviation from best Straight Line

E_R

Rollover Error

-1

—

-1

15

1

±0.2

—

1 Count V_IN- = V_IN+ ≈ 200mV

e_N

Noise

µV_P-PV_IN= 0V, Full Scale = 200mV

I_L

Input Leakage Current

Common Mode Rejection Ratio

10

—

pA

V_IN= 0V

CMRR

TC_SF

50

1

µV/V

V_CM= ±1V, V_IN= 0V, Full Scale = 200mV

Scale Factor Temperature

Coefficient

5

ppm/°C V_IN= 199mV, 0°C ≤ T_A≤ +70°C

Ext. Ref. Temp. Coeff. = 0ppm/°C

Note 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 PC board.

3: Refer to "Differential Input" discussion.

4: Backplane drive is in phase with segment drive for "OFF" segment and 180° out-of-phase for "ON" segment. Frequency

is 20 times conversion rate. Average DC component is less than 50mV.

5: See "Typical Application".

6: A 48kHz oscillator increases current by 20µA (typical). Common current not included.

2002 Microchip Technology Inc.

DS21461B-page 5

TC7136/TC7136A

TC7136 AND TC7136A ELECTRICAL SPECIFICATIONS (CONTINUED)

Electrical Characteristics: V_S= 9V, f_CLK= 16kHz, and T_A= +25°C, unless otherwise noted.

Symbol

Parameter

Min

Typ

Max

Unit

Test Conditions

Analog Common

V_CTC

Analog Common Temperature

Coefficient

250kΩ between Common and V+

TC7136A

TC7136

—

35

70

75

ppm/°C 0°C ≤ T_A≤ +70°C

150

100

150

3.35

ppm/°C "C" Commercial Temp. Range Devices

ppm/°C -25°C ≤ T_A≤ +85°C

TC7136A

—

35

TC7136

—

70

ppm/°C "I" Industrial Temp. Range Devices

V_C

Analog Common Voltage

2.7

3.05

V

250kΩ Between Common and V+

LCD Drive

V_SD

V_BD

LCD Segment Drive Voltage

LCD Backplane Drive Voltage

4

5

6

V_P-P

V+ to V- = 9V

Power Supply

I_SPower Supply Current

—

70

100

µA

V_IN= 0V, V+ to V- = 9V (Note 6)

Note 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 PC board.

3: Refer to "Differential Input" discussion.

4: Backplane drive is in phase with segment drive for "OFF" segment and 180° out-of-phase for "ON" segment. Frequency

is 20 times conversion rate. Average DC component is less than 50mV.

5: See "Typical Application".

6: A 48kHz oscillator increases current by 20µA (typical). Common current not included.

DS21461B-page 6

2002 Microchip Technology Inc.

TC7136/TC7136A

2.0

PIN DESCRIPTIONS

The descriptions of the pins are listed in Table 2-1.

TABLE 2-1:

PIN DESCRIPTION

Pin Number

(40-Pin PDIP)

Normal

(Reverse)

Symbol

Description

1

(40)

(39)

(38)

(37)

(36)

(35)

(34)

(33)

(32)

(31)

(30)

(29)

(28)

(27)

(26)

(25)

(24)

(23)

(22)

(21)

(20)

(19)

(18)

(17)

(16)

(15)

(14)

V+

D₁

C₁

B₁

Positive supply voltage.

2

Activates the D section of the units display.

Activates the C section of the units display.

Activates the B section of the units display.

Activates the A section of the units display.

Activates the F section of the units display.

Activates the G section of the units display.

Activates the E section of the units display.

Activates the D section of the tens display.

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 negative polarity display.

3

4

5

A₁

6

F₁

7

G₁

E₁

8

9

D₂

C₂

B₂

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

A₂

F₂

E₂

D₃

B₃

F₃

E₃

AB₄

POL

BP

G₃

A₃

Backplane drive output.

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.

C₃

G₂

V-

V_INT

The integrating capacitor should be selected to give the maximum voltage swing

that ensures component tolerance buildup will not allow the integrator output to sat-

urate. When analog common is used as a reference and the conversion rate is 3

readings per second, a 0.047µF capacitor may be used. The capacitor must have a

low dielectric constant to prevent rollover errors. See Section 6.3, Integrating

Capacitor for additional details.

28

29

(13)

(12)

V_BUFF

C_AZ

Integration resistor connection. Use a 180kΩ for a 20mV full scale range and a

1.8MΩ for 2V full scale range.

The size of the auto-zero capacitor influences the system noise. Use a 0.47µF

capacitor for a 200mV full scale and a 0.1µF capacitor for a 2V full scale.

See Section 6.1, Auto-Zero Capacitor for more details.

30

31

32

(11)

(10)

(9)

V_IN

ANALOG

-

The low input signal is connected to this pin.

+

The high input signal is connected to this pin.

This pin is primarily used to set the Analog Common mode voltage for battery

COMMON operation, or in systems where the input signal is referenced to the power supply.

See Section 7.3, Analog Common for more details. It also acts as a reference

voltage source.

33

(8)

C_REF

-

See Pin 34.

2002 Microchip Technology Inc.

DS21461B-page 7

TC7136/TC7136A

TABLE 2-1:

PIN DESCRIPTION (CONTINUED)

Pin Number

(40-Pin PDIP)

Normal

(Reverse)

Symbol

Description

34

(7)

C_REF

+

A 0.1µF capacitor is used in most applications. If a large Common mode voltage

exists (for example, the V_IN- pin is not at analog common) and a 200mV scale is

used, a 1µF capacitor is recommended, which will hold the rollover error to

0.5 count.

35

(6)

(5)

V_REF

-

See Pin 36.

+

The analog input required to generate a full scale output (1999 counts). Place

100mV between Pins 35 and 36 for 199.9mV full scale. Place 1V between Pins 35

and 36 for 2V full scale. See Section 6.6, Reference Voltage.

36

(4)

TEST

Lamp test. When pulled HIGH (to V+), all segments will be turned ON and the

display should read -1888. It may also be used as a negative supply for externally

generated decimal points. See Section 7.4, Test for additional information.

37

38

39

(3)

(2)

(1)

OSC3

OSC2

OSC1

See Pin 40.

Pins 40, 39 and 38 make up the oscillator section. For a 48kHz clock

(3 readings per second), connect Pin 40 to the junction of a 180kΩ resistor and a

50pF capacitor. The 180kΩ resistor is tied to Pin 39 and the 50pF capacitor is tied

to Pin 38.

DS21461B-page 8

2002 Microchip Technology Inc.

TC7136/TC7136A

FIGURE 3-1:

BASIC DUAL SLOPE

CONVERTER

3.0

DETAILED DESCRIPTION

(All Pin Designations Refer to 40-Pin PDIP.)

C

INT

3.1

Dual Slope Conversion Principles

Analog Input

Signal

Integrator

–

The TC7136/A is a dual slope, integrating analog-to-

digital converter. An understanding of the dual slope

conversion technique will aid in following detailed

TC7136/A operational theory.

Comparator

–

+

Switch

Driver

The conventional dual slope converter measurement

cycle has two distinct phases (see Figure 3-1).

Clock

Phase

Control

REF

Voltage

Control

Logic

1. Input signal integration

Polarity Control

Display

2. Reference voltage integration (de-integration)

The input signal being converted is integrated for a

Counter

fixed time period (t ), measured by counting clock

SI

pulses. An opposite polarity constant reference voltage

is then integrated until the integrator output voltage

returns to zero. The reference integration time is

V

≈ V

REF

IN

≈ 1/2 V

REF

directly proportional to the input signal (t ).

Fixed Variable

RI

Signal Reference

Integrate Integrate

Time Time

In a simple dual slope converter, a complete conver-

sion requires the integrator output to "ramp up" and

"ramp down."

FIGURE 3-2:

NORMAL MODE

REJECTION OF DUAL

SLOPE CONVERTER

A simple mathematical equation relates the input

signal, reference voltage, and integration time:

EQUATION 3-1:

30

20

10

0

t

V

t

SI

R RI

1

RC

--------

V

(t)d^t= ------------

IN

RC

0

Where:

V

= Reference voltage

R

t

= Signal integration time (fixed)

= Reference voltage integration time

(variable)

SI

RI

t = Measured Period

For a constant V

:

IN

0.1/t

1/t

10/t

EQUATION 3-2:

Input Frequency

t

RI

-------

V

= V

R

IN

t

The dual slope converter accuracy is unrelated to the

integrating resistor and capacitor values, as long as

they are stable during a measurement cycle. Noise

immunity is an inherent benefit. Noise spikes are inte-

grated or averaged to zero during integration periods.

Integrating ADCs are immune to the large conversion

errors that plague successive approximation convert-

ers in high noise environments. Interfering signals with

frequency components at multiples of the averaging

period will be attenuated. Integrating ADCs commonly

operate with the signal integration period set to a

multiple of the 50Hz/60Hz power line period.

SI

2002 Microchip Technology Inc.

DS21461B-page 9

TC7136/TC7136A

The differential input voltage must be within the device

Common mode range when the converter and mea-

sured system share the same power supply common

(ground). If the converter and measured system do not

4.0

ANALOG SECTION

In addition to the basic integrate and de-integrate dual

slope cycles discussed above, the TC7136 and

TC7136A designs incorporate an "integrator output

zero cycle" and an "auto-zero cycle." These additional

cycles ensure the integrator starts at 0V (even after a

severe over range conversion) and that all offset volt-

age errors (buffer amplifier, integrator and comparator)

are removed from the conversion. A true digital zero

reading is assured without any external adjustments.

share the same power supply common, V - should be

IN

tied to analog common.

Polarity is determined at the end of signal integrate

phase. The sign bit is a true polarity indication, in that

signals less than 1LSB are correctly determined. This

allows precision null detection, limited only by device

noise and auto-zero residual offsets.

A complete conversion consists of four distinct phases:

4.4

Reference Integrate Phase

1. Integrator output zero phase

2. Auto-zero phase

The third phase is reference integrate or de-integrate.

3. Signal integrate phase

4. Reference de-integrate phase

V

- is internally connected to analog common and

+ is connected across the previously charged refer-

IN

ence capacitor. Circuitry within the chip ensures that

the capacitor will be connected with the correct polarity

to cause the integrator output to return to zero. The

time required for the output to return to zero is propor-

tional to the input signal and is between 0 and 2000

internal clock periods. The digital reading displayed is:

4.1

Integrator Output Zero Phase

This phase ensures the integrator output is at 0V

before the system zero phase is entered. This ensures

that true system offset voltages will be compensated

for, even after an over range conversion. The count for

this phase is a function of the number of counts

required by the de-integrate phase. The count lasts

from 11 to 140 counts for non over range conversions

and from 31 to 640 counts for over range conversions.

EQUATION 4-2:

V

IN

1000 = ----------------

V

REF

4.2

Auto-Zero Phase

FIGURE 4-1:

CONVERSION TIMING

DURING NORMAL

OPERATION

During the auto-zero phase, the differential input signal

is disconnected from the circuit by opening internal

analog gates. The internal nodes are shorted to analog

common (ground) to establish a zero input condition.

Additional analog gates close a feedback loop around

the integrator and comparator. This loop permits com-

parator offset voltage error compensation. The voltage

1000

INT

1-2000

DENT

level established on C compensates for device offset

voltages. The auto-zero phase residual is typically

AZ

11-140

ZI

AZ

10µV to 15µV.

910-2900

4000

The auto-zero duration is from 910 to 2900 counts for

non over range conversions and from 300 to 910

counts for over range conversions.

FIGURE 4-2:

CONVERSION TIMING

DURING OVER RANGE

OPERATION

4.3

Signal Integration Phase

The auto-zero loop is entered and the internal differen-

tial inputs connect to V + and V -. The differential

IN

input signal is integrated for a fixed time period. The

TC7136/A signal integration period is 1000 clock peri-

ods or counts. The externally set clock frequency is

divided by four before clocking the internal counters.

The integration time period is:

1000

INT

2001-2090

31-640

DEINT

EQUATION 4-1:

ZI

AZ

4

300-910

4000

t

=

x 1000

SI

F

OSC

Where F

= external clock frequency.

OSC

DS21461B-page 10

2002 Microchip Technology Inc.

TC7136/TC7136A

Each phase of the measurement cycle has the

following length:

5.0

DIGITAL SECTION

The TC7136/A contains all the segment drivers neces-

sary to directly drive a 3-1/2 digit LCD. An LCD back-

plane driver is included. The backplane frequency is

the external clock frequency divided by 800. For three

conversions per second, the backplane frequency is

60Hz with a 5V nominal amplitude. When a segment

driver is in phase with the backplane signal, the seg-

ment is OFF. An out-of-phase segment drive signal

causes the segment to be ON, or visible. This AC drive

configuration results in negligible DC voltage across

each LCD segment, ensuring long LCD life. The polar-

ity segment driver is ON for negative analog inputs. If

1. Auto-zero phase: 3000 to 2900 counts

(1200 to 11,600 clock pulses)

2. Signal integrate: 1000 counts

(4000 clock pulses)

This time period is fixed. The integration period is:

EQUATION 5-1:

Where:

1

t

= 4000

SI

F

OSC

F

is the externally set clock frequency.

OSC

V

+ and V - are reversed, this indicator would

IN

reverse.

3. Reference integrate: 0 to 2000 counts

4. Zero integrator: 11 to 640 counts

On the TC7136/A, when the TEST pin is pulled to V+,

all segments are turned ON. The display reads -1888.

During this mode, the LCD segments have a constant

DC voltage impressed.

The TC7136 is a drop-in replacement for the TC7126

and ICL7126. The TC7136A offers a greatly improved

internal reference temperature coefficient. Minor com-

ponent value changes are required to upgrade existing

designs and improve the noise performance.

Note: Do not leave the display in this mode for

more than several minutes. LCDs may be

destroyed if operated with DC levels for

extended periods.

6.0

6.1

COMPONENT VALUE

SELECTION

The display font and segment drive assignment are

shown in Figure 5-1.

Auto-Zero Capacitor (C_AZ

)

FIGURE 5-1:

DISPLAY FONT AND

SEGMENT ASSIGNMENT

The C capacitor size has some influence on system

AZ

noise. A 0.47µF capacitor is recommended for 200mV

full scale applications, where 1LSB is 100µV. A 0.1µF

capacitor is adequate for 2V full scale applications. A

Mylar type dielectric capacitor is adequate.

Display Font

1000's

100's

10's

1's

6.2

Reference Voltage Capacitor

(C_REF

)

The reference voltage, used to ramp the integrator out-

put voltage back to zero during the reference integrate

phase, is stored on C . A 0.1µF capacitor is accept-

REF

able when V

Common mode voltage exists (V

- is tied to analog common. If a large

REF

5.1

System Timing

- ≠ analog com-

REF

The oscillator frequency is divided by 4 prior to clocking

the internal decade counters. The four-phase mea-

surement cycle takes a total of 4000 counts, or 16,000

clock pulses. The 4000 count cycle is independent of

input signal magnitude.

mon) and the application requires a 200mV full scale,

increase C to 1µF. Rollover error will be held to less

than 0.5 count. A Mylar type dielectric capacitor is

adequate.

REF

6.3

Integrating Capacitor (C_INT)

C

should be selected to maximize integrator output

INT

voltage swing without causing output saturation. Ana-

log common will normally supply the differential voltage

reference in this case, a ±2V full scale integrator output

swing is satisfactory. For 3 readings per second

(F

= 48kHz), a 0.047µF value is suggested. For

OSC

one reading per second, 0.15µF is recommended. If a

different oscillator frequency is used, C must be

INT

changed in inverse proportion to maintain the nominal

±2V integrator swing.

2002 Microchip Technology Inc.

DS21461B-page 11

TC7136/TC7136A

An exact expression for C

is:

6.5

Oscillator Components

INT

EQUATION 6-1:

C

should be 50pF. R

is selected from the

OSC

equation:

V

R

1

FS

(4000)

F

EQUATION 6-2:

OSC

INT

C

=

INT

V

0.45

RC

INT

F

=

OSC

Where:

F

= Clock frequency at Pin 38

= Full scale input voltage

Note that F

is ÷ 4 to generate the TC7136A's inter-

OSC

nal clock. The backplane drive signal is derived by

dividing F by 800.

V

FS

OSC

R

= Integrating resistor

INT

To achieve maximum rejection of 60Hz noise pickup,

the signal integrate period should be a multiple of

60Hz. Oscillator frequencies of 240kHz, 120kHz,

80kHz, 60kHz, 40kHz, etc. should be selected. For

50Hz rejection, oscillator frequencies of 200kHz,

100kHz, 66-2/3kHz, 50kHz, 40kHz, etc. would be suit-

able. Note that 40kHz (2.5 readings per second) will

reject both 50Hz and 60Hz.

V

= Desired full scale integrator output swing

INT

C

must have low dielectric absorption to minimize

rollover error.

recommended.

INT

A

polypropylene capacitor is

6.4

Integrating Resistor (R_INT)

The input buffer amplifier and integrator are designed

with Class A output stages. The output stage idling cur-

rent is 6µA. The integrator and buffer can supply 1µA

6.6

Reference Voltage Selection

A full scale reading (2000 counts) requires the input

signal be twice the reference voltage.

drive currents with negligible linearity errors. R

is

INT

chosen to remain in the output stage linear drive

region, but not so large that PC board leakage currents

Required Full Scale Voltage*

V

REF

induce errors. For a 200mV full scale, R

2V full scale requires 1.8MΩ (see Table 6-1).

is 180kΩ. A

INT

200mV

2V

100mV

1V

Note:

*V_REF= 2V_REF.

TABLE 6-1:

In some applications, a scale factor other than unity

may exist between a transducer output voltage and the

required digital reading. Assume, for example, a pres-

Nominal Full Scale Voltage

Component

Value

200mV

2V

2

sure transducer output for 2000 lb/in is 400mV. Rather

C

R

0.47µF

180kΩ

0.1µF

1.8MΩ

0.047µF

AZ

than dividing the input voltage by two, the reference

voltage should be set to 200mV. This permits the trans-

ducer input to be used directly. The differential refer-

ence can also be used when a digital zero reading is

INT

C

0.047µF

Note:

F_OSC= 48kHz (3 reading per sec).

required, when V is not equal to zero. This is common

IN

R_OSC= 180kΩ, C_OSC= 50pF.

in temperature measuring instrumentation. A compen-

sating offset voltage can be applied between analog

common and V -. The transducer output is connected

IN

between V + and analog common.

IN

DS21461B-page 12

2002 Microchip Technology Inc.

TC7136/TC7136A

V+ – 1V to V- + 1V. Common mode voltages are

removed from the system when the TC7136A operates

from a battery or floating power source (isolated from

measured system), Common mode voltage removed

7.0

7.1

DEVICE PIN FUNCTIONAL

DESCRIPTION

Differential Signal Inputs

V_IN+ (Pin 31), V_IN- (Pin 30)

in battery operation with V = analog common and V

-

IN

is connected to analog common (V

Figure 7-1).

)

(see

COM

The TC7136/A is designed with true differential inputs

and accepts input signals within the input stage Com-

mon mode voltage range (V ). The typical range is

CM

FIGURE 7-1:

COMMON MODE VOLTAGE REMOVED IN BATTERY OPERATION WITH

V

= ANALOG COMMON

IN

Segment

Drive

LCD

Measured

System

V

C

V

INT

POL BP

BUF

AZ

OSC1

V+

TC7136

V+

OSC3

V-

TC7136A

V-

OSC2

V-

GND

ANALOG

COMMON

V

- V

+

REF REF

V+

V-

GND

Power

Source

+

9V

In systems where Common mode voltages exist, the

86dB Common mode rejection ratio minimizes error.

Common mode voltages do, however, affect the inte-

grator output level. A worst case condition exists if a

7.2

Differential Reference

_REF+ (Pin 36), V_REF- (Pin 35)

V

The reference voltage can be generated anywhere

within the V+ to V- power supply range.

large positive V exists in conjunction with a full scale

CM

negative differential signal. The negative signal drives

To prevent rollover type errors being induced by large

the integrator output positive along with V

(see

CM

Common mode voltages, C

should be large com-

REF

Figure 7-2.) For such applications, the integrator out-

put swing can be reduced below the recommended 2V

full scale swing. The integrator output will swing within

0.3V of V+ or V- without increased linearity error.

pared to stray node capacitance. The TC7136/A offers

a significantly improved analog common temperature

coefficient. This potential provides a very stable volt-

age, suitable for use as a voltage reference. The

temperature coefficient of analog common is typically

35ppm/°C.

FIGURE 7-2:

COMMON MODE

VOLTAGE REDUCES

AVAILABLEINTEGRATOR

SWING (V_COM≠ V_IN)

7.3

Analog Common (Pin 32)

The analog common pin is set at a voltage potential

approximately 3V below V+. The potential is between

2.7V and 3.35V below V+. Analog common is tied inter-

nally to an N-channel FET, capable of sinking 100µA.

This FET will hold the common line at 3V below V+ if an

external load attempts to pull the common line toward

V+. Analog common source current is limited to 1µA.

Analog common is, therefore, easily pulled to a more

negative voltage (i.e., below V+ – 3V).

C

I

Input Buffer

R

+

I

–

V

I

V

IN

+

Integrator

–

t

I

V

=

V

CM

= V

IN [

I

[

V

C

I

CM

Where:

4000

t = Integration time

=

I

F

OSC

C = Integration capacitor

I

R = Integration resistor

I

2002 Microchip Technology Inc.

DS21461B-page 13

TC7136/TC7136A

The TC7136/A connects the internal V + and V

-

IN

FIGURE 7-3:

ANALOG COMMON

TEMPERATURE

COEFFICIENT

IN

inputs to analog common during the auto-zero phase.

During the reference integrate phase, V - is connected

IN

to analog common. If V - is not externally connected to

IN

200

180

analog common, a Common mode voltage exists, but

is rejected by the converter's 86dB Common mode

rejection ratio. In battery operation, analog common

No Maximum

Specified

160

140

120

100

Maximum

and V - are usually connected, removing Common

IN

mode voltage concerns. In systems where V - is con-

IN

Typical

nected to the power supply ground or to a given

voltage, analog common should be connected to V -.

IN

The analog common pin serves to set the analog sec-

tion reference, or common point. The TC7136A is spe-

cifically designed to operate from a battery, or in any

measurement system where input signals are not refer-

enced (float), with respect to the TC7136A power

source. The analog common potential of V+ – 3V gives

a 7V end of battery life voltage. The common potential

has a 0.001%/% voltage coefficient.

Maximum

80

60

40

20

Typical

TC7136A

TC7136

ICL7136

0

With

sufficiently

high

total

supply

voltage

(V+ – V- > 7V), analog common is a very stable poten-

tial with excellent temperature stability (typically

35ppm/°C for TC7136A. This potential can be used to

generate the TC7136A's reference voltage. An external

voltage reference will be unnecessary in most cases,

because of the 35ppm/°C temperature coefficient. See

Section 7.5, TC7136A Internal Voltage Reference

discussion.

FIGURE 7-4:

TC7136A INTERNAL

VOLTAGE REFERENCE

CONNECTION

9V

+

26

1

240kΩ

10kΩ

V-

V+

7.4

TEST (Pin 37)

TC7136

TC7136A

The TEST pin potential is 5V less than V+. TEST may

be used as the negative power supply connection for

external CMOS logic. The TEST pin is tied to the inter-

nally generated negative logic supply through a 500Ω

resistor. The TEST pin load should not be more than

1mA. See Section 8.0, Typical Applications for addi-

tional information on using TEST as a negative digital

logic supply.

36

V

+

REF

V

REF

35

V

-

REF

32

ANALOG

COMMON

= 1/2 V

Set V

REF

If TEST is pulled high (to V+), all segments plus the

minus sign will be activated. DO NOT OPERATE IN

THIS MODE FOR MORE THAN SEVERAL MINUTES.

With TEST = V+, the LCD segments are impressed with

a DC voltage which will destroy the LCD.

7.5

TC7136A Internal Voltage

Reference

The TC7136 analog common voltage temperature sta-

bility has been significantly improved (Figure 7-3). The

"A" version of the industry standard TC7136 device

allows users to upgrade old systems and design new

systems without external voltage references. External

R and C values do not need to be changed; however,

noise performance will be improved by increasing C

AZ

(see Section 6.1, Auto-Zero Capacitor). Figure 7-4

shows analog common supplying the necessary

voltage reference for the TC7136/A.

DS21461B-page 14

2002 Microchip Technology Inc.

TC7136/TC7136A

The unknown resistance is put in series with a known

standard and a current passed through the pair. The

voltage developed across the unknown is applied to the

input and the voltage across the known resistor applied

to the reference input. If the unknown equals the stan-

dard, the display will read 1000. The displayed reading

can be determined from the following expression:

8.0

8.1

TYPICAL APPLICATIONS

Liquid Crystal Display Sources

Several manufacturers supply standard LCDs to inter-

face with the TC7136A 3-1/2 digit analog-to-digital

converter.

Representative

Part Numbers*

EQUATION 8-1:

Manufac.

Address/Phone

R

UNKNOWN

STANDARD

Displayed(Reading) =

x 1000

Crystaloid

Electronics

5282 Hudson Dr.

Hudson, OH 44236

216-655-2429

C5335, H5535,

T5135, SX440

The display will over range for:

AND

720 Palomar Ave.

FE 0201, 0501

R

≥ 2 x R

STANDARD

Sunnyvale, CA 94086 FE 0203, 0701

408-523-8200 FE 2201

UNKNOWN

VGI, Inc.

1800 Vernon St. Ste.2, I1048, I1126

Roseville,

CA 95678

FIGURE 8-1:

DECIMAL POINT AND

ANNUNCIATOR DRIVES

916-783-7878

Simple Inverter for Fixed Decimal Point

or Display Annunciator

Hamlin, Inc. 612 E. Lake St.

Lake Mills,

3902, 3933, 3903

V+

WI 53551

414-648-236100

V+

TC7136

TC7136A

4049

Note:

Contact LCD manufacturer for full product listing/

specifications.

To LCD

Decimal Point

21

37

BP

8.2

Decimal Point and Annunciator

Drive

GND

TEST

The TEST pin is connected to the internally generated

digital logic supply ground through a 500Ω resistor. The

TEST pin may be used as the negative supply for exter-

nal CMOS gate segment drivers. LCD annunciators for

decimal points, low battery indication, or function indi-

cation may be added without adding an additional sup-

ply. No more than 1mA should be supplied by the TEST

pin; its potential is approximately 5V below V+.

To LCD Backplane

Multiple Decimal Point or

Annunciator Driver

V+

BP

TC7136

TC7136A

To LCD

Decimal Point

Decimal

Point

Select

8.3

Ratiometric Resistance

Measurements

The TC7136A's true differential input and differential

reference make ratiometric readings possible. In ratio-

metric operation, an unknown resistance is measured

with respect to a known standard resistance. No

accurately defined reference voltage is needed.

4030

GND

TEST

2002 Microchip Technology Inc.

DS21461B-page 15

TC7136/TC7136A

FIGURE 8-2:

LOW PARTS COUNT

RATIOMETRIC

RESISTANCE

FIGURE 8-4:

POSITIVE TEMPERATURE

COEFFICIENT RESISTOR

TEMPERATURE SENSOR

MEASUREMENT

9V

+

V+

V

+

-

5.6kΩ

160kΩ

REF

R

V+

V-

REF

STANDARD

R

20kΩ

V

IN

-

1

1N4148

LCD

V

+

IN

V

+

TC7136

IN

R

UNKNOWN

TC7136A

TC7136

TC7136A

0.7%/°C

R

20kΩ

2

R

3

V

-

V

+

PTC

IN

REF

ANALOG

COMMON

-

REF

COMMON

FIGURE 8-3:

TEMPERATURE SENSOR

+

9V

160kΩ

300kΩ

V+

V-

V

IN

-

R

50kΩ

1N4148

Sensor

1

V

+

IN

TC7136

TC7136A

REF

R

50kΩ

2

V

+

-

REF

COMMON

DS21461B-page 16

2002 Microchip Technology Inc.

TC7136/TC7136A

9.0

9.1

PACKAGING INFORMATION

Package Marking Information

Package marking data not available at this time.

9.2

Taping Form

Component Taping Orientation for 44-Pin PQFP Devices

User Direction of Feed

PIN 1

W

P

Standard Reel Component Orientation

for TR Suffix Device

Carrier Tape, Number of Components Per Reel and Reel Size

Package

Carrier Width (W)

Pitch (P)

Part Per Full Reel

Reel Size

44-Pin PQFP

24 mm

16 mm

500

13 in

Note: Drawing does not represent total number of pins.

Component Taping Orientation for 44-Pin PLCC Devices

User Direction of Feed

PIN 1

W

P

Standard Reel Component Orientation

for TR Suffix Device

Carrier Tape, Number of Components Per Reel and Reel Size

Package

Carrier Width (W)

Pitch (P)

Part Per Full Reel

Reel Size

44-Pin PLCC

32 mm

24 mm

500

13 in

Note: Drawing does not represent total number of pins.

2002 Microchip Technology Inc.

DS21461B-page 17

TC7136/TC7136A

9.3

Package Dimensions

40-Pin PDIP (Wide)

PIN 1

.555 (14.10)

.530 (13.46)

2.065 (52.45)

2.027 (51.49)

.610 (15.49)

.590 (14.99)

.200 (5.08)

.140 (3.56)

.040 (1.02)

.020 (0.51)

.015 (0.38)

.008 (0.20)

.150 (3.81)

.115 (2.92)

3° MIN.

.700 (17.78)

.610 (15.50)

.110 (2.79)

.090 (2.29)

.070 (1.78)

.045 (1.14)

.022 (0.56)

.015 (0.38)

Dimensions: inches (mm)

44-Pin PLCC

PIN 1

.021 (0.53)

.013 (0.33)

.050 (1.27) TYP.

.695 (17.65)

.685 (17.40)

.630 (16.00)

.591 (15.00)

.656 (16.66)

.650 (16.51)

.032 (0.81)

.026 (0.66)

.020 (0.51) MIN.

.656 (16.66)

.650 (16.51)

.120 (3.05)

.090 (2.29)

.695 (17.65)

.685 (17.40)

.180 (4.57)

.165 (4.19)

Dimensions: inches (mm)

DS21461B-page 18

2002 Microchip Technology Inc.

TC7136/TC7136A

9.3

Package Dimensions (Continued)

44-Pin PQFP

7° MAX.

.009 (0.23)

.005 (0.13)

PIN 1

.041 (1.03)

.026 (0.65)

.018 (0.45)

.012 (0.30)

.398 (10.10)

.390 (9.90)

.557 (14.15)

.537 (13.65)

.031 (0.80) TYP.

.010 (0.25) TYP.

.398 (10.10)

.390 (9.90)

.083 (2.10)

.075 (1.90)

.557 (14.15)

.537 (13.65)

.096 (2.45) MAX.

Dimensions: inches (mm)

2002 Microchip Technology Inc.

DS21461B-page 19

TC7136/TC7136A

SALES AND SUPPORT

Data Sheets

Products supported by a preliminary Data Sheet may have an errata sheet describing minor operational differences and recom-

mended workarounds. To determine if an errata sheet exists for a particular device, please contact one of the following:

1. Your local Microchip sales office

2. The Microchip Corporate Literature Center U.S. FAX: (480) 792-7277

3. The Microchip Worldwide Site (www.microchip.com)

Please specify which device, revision of silicon and Data Sheet (include Literature #) you are using.

New Customer Notification System

Register on our web site (www.microchip.com/cn) to receive the most current information on our products.

DS21461B-page 20

2002 Microchip Technology Inc.

TC7136/TC7136A

Information contained in this publication regarding device

applications and the like is intended through suggestion only

and may be superseded by updates. It is your responsibility to

ensure that your application meets with your specifications.

No representation or warranty is given and no liability is

assumed by Microchip Technology Incorporated with respect

to the accuracy or use of such information, or infringement of

patents or other intellectual property rights arising from such

use or otherwise. Use of Microchip’s products as critical com-

ponents in life support systems is not authorized except with

express written approval by Microchip. No licenses are con-

veyed, implicitly or otherwise, under any intellectual property

rights.

Trademarks

The Microchip name and logo, the Microchip logo, FilterLab,

KEELOQ, microID, MPLAB, PIC, PICmicro, PICMASTER,

PICSTART, PRO MATE, SEEVAL and The Embedded Control

Solutions Company are registered trademarks of Microchip Tech-

nology Incorporated in the U.S.A. and other countries.

dsPIC, ECONOMONITOR, FanSense, FlexROM, fuzzyLAB,

In-Circuit Serial Programming, ICSP, ICEPIC, microPort,

Migratable Memory, MPASM, MPLIB, MPLINK, MPSIM,

MXDEV, PICC, PICDEM, PICDEM.net, rfPIC, Select Mode

and Total Endurance are trademarks of Microchip Technology

Incorporated in the U.S.A.

Serialized Quick Turn Programming (SQTP) is a service mark

of Microchip Technology Incorporated in the U.S.A.

All other trademarks mentioned herein are property of their

respective companies.

Printed on recycled paper.

Microchip received QS-9000 quality system

certification for its worldwide headquarters,

design and wafer fabrication facilities in

Chandler and Tempe, Arizona in July 1999

and Mountain View, California in March 2002.

The Company’s quality system processes and

procedures are QS-9000 compliant for its

PICmicro^®8-bit MCUs, KEELOQ^®code hopping

devices, Serial EEPROMs, microperipherals,

non-volatile memory and analog products. In

addition, Microchip’s quality system for the

design and manufacture of development

systems is ISO 9001 certified.

2002 Microchip Technology Inc.

DS21461B-page 21

WORLDWIDE SALES AND SERVICE

Japan

AMERICAS

ASIA/PACIFIC

Microchip Technology Japan K.K.

Benex S-1 6F

3-18-20, Shinyokohama

Kohoku-Ku, Yokohama-shi

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Tel: 81-45-471- 6166 Fax: 81-45-471-6122

Corporate Office

Australia

2355 West Chandler Blvd.

Microchip Technology Australia Pty Ltd

Suite 22, 41 Rawson Street

Epping 2121, NSW

Chandler, AZ 85224-6199

Tel: 480-792-7200 Fax: 480-792-7277

Technical Support: 480-792-7627

Web Address: http://www.microchip.com

Australia

Tel: 61-2-9868-6733 Fax: 61-2-9868-6755

Korea

Rocky Mountain

China - Beijing

Microchip Technology Korea

168-1, Youngbo Bldg. 3 Floor

Samsung-Dong, Kangnam-Ku

Seoul, Korea 135-882

2355 West Chandler Blvd.

Chandler, AZ 85224-6199

Tel: 480-792-7966 Fax: 480-792-7456

Microchip Technology Consulting (Shanghai)

Co., Ltd., Beijing Liaison Office

Unit 915

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Atlanta

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Tel: 770-640-0034 Fax: 770-640-0307

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Hong Kong

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Tel: 91-80-2290061 Fax: 91-80-2290062

03/01/02

DS21461B-page 22

2002 Microchip Technology Inc.


型号：	TC7136
厂家：	MICROCHIP
描述：	Low Power 3-1/2 Digit Analog-to-Digital Converter 低功耗3-1 / 2位模拟数字转换器转换器
文件：	总22页 (文件大小：534K)
中文：	中文翻译
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TC7136 [MICROCHIP]

相关型号：

TC7136A

TC7136A

TC7136ACKW

TC7136ACKW

TC7136ACKW713

TC7136ACKWTR

TC7136ACLW

TC7136ACLW

TC7136ACLW713

TC7136ACLWTR

TC7136ACPI

TC7136ACPL