M7240 [UTC]

3 1/2 LCD DISPLAY DRIVER, A/D CONVERTERS; 3 1/2 LCD显示驱动， A / D转换器


型号：	M7240
厂家：	Unisonic Technologies
描述：	3 1/2 LCD DISPLAY DRIVER, A/D CONVERTERS 3 1/2 LCD显示驱动， A / D转换器转换器驱动 CD
文件：	总7页 (文件大小：206K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

UNISONIC TECHNOLOGIES CO., LTD

M7240

CMOS IC

3 1/2 LCD DISPLAY DRIVER,

A/D CONVERTERS

DESCRIPTION

The UTC M7240 is a low voltage power supply of three half A/D

conversion IC. With the M7240, the product can be assembled the

digital gauge outfit and digital multimeters with 3V batteries supply.

The M7240 has hare the following features: using the only two

batteries of 7V or a 3V lithium batteries can work for long time the

chip contains an internal clock generator which can be fine-tuned by

a resistor, slicing the band gap in design makes the benchmark

signals shift and temperature shift noise greatly improve, slicing the

negative power produced within the circuit design, the maximum

load current can reach to 2mA.

FEATURES

*Power Supply Voltage:2.5V ~ 6V

*external clock circuit within a resistor, used for clock

frequency fine-tuning

*Built-in close bandgap reference, low temperature drift

*High input impedance

*Low noise A/D converter

*Guaranteed zero reading with zero input.

*Has triggered buttons that keep and low voltage alarm function that

power

*Direct driver LCD display

ORDERING INFORMATION

Ordering Number

Package

LQFP-44

Packing

Tray

Lead Free

Halogen Free

M7240G-QL1-Y

M7240L-QL1-Y

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M7240

CMOS IC

PIN CONFIGURATIONS

PIN DESCRIPTION

1～3、41～44

4～9、21

NAME

A1~G1

A2~G2

A3~G3

AB4

TYPE

PIN DESCRIPTION

LCD segment drive

LCD Drive display minus "-"

LCD public driver

10~13、18~20

POL

BP signal output terminals, inverse for LCD display decimal and other

special symbols of liquid crystal display driver

Low battery flag. Pull high if low battery

Negative voltage

BP_

V-

INT

Integrator output

BUF

Integration register connection.

Auto-zero capacitor connection

INLO

INHI

COM

CRF-

CRF+

RFLO

RFHI

HLDO

Analog low input signal

Analog high input signal

Set the common-mode voltage for the system

Negative capacitor connection for on-chip A/D converter

Positive capacitor connection for on-chip A/D converter

Low differential reference input connection.

High differential reference input connection

Keep output terminal display

The clock frequency adjustment, through a resistance to V + adjustable

reduce chip clock frequency

HOLD

CAP-

GND

CAP+

V+

Hold input pin. Connecting to V+ for hold function

Negative voltage capacitance connection negative terminals

Ground

Negative voltage capacitance connection positive terminals

Positive supply voltage.

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M7240

CMOS IC

BLOCK DIAGRAM

LCD DRIVER

LCD PHASE DRIVER

SEGMENT

DECODE

SEGMENT

DECODE

SEGMENT

DECODE

÷200

LATCH

1000's

COUNTER

100's

COUNTER

10's

COUNTER

1's

COUNTER

TO SWITCH

DRIVERS

V+

osc

V-

÷4

LOGIC CONTROL

RFHI

CAP-

GND

CAP+

LOW

BATTERY

DETECTOR

RFLO

V- GEN

3-½ Digital A/D

Converter

INHI

INLO

ANALOG

COMMON

COM

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M7240

CMOS IC

ABSOLUTE MAXIMUM RATING (unless otherwise specified)

PARAMETER

Power Supply Voltage(V+～V-）

SYMBOL

V_CC

RATINGS

UNIT

Analog input voltage

V_IANG

V_IREF

T_OPR

T_STG

T_J

V+~V-

0 ~ 70

-65 ~ +150

150

Reference Input Voltage

Operating Temperature

Storage Temperature

°C

Junction Temperature

Note: Absolute maximum ratings are those values beyond which the device could be permanently damaged.

Absolute maximum ratings are stress ratings only and functional device operation is not implied.

RECOMMENDED OPERATING CONDITIONS (unless otherwise specified)

PARAMETER

Power Supply Voltage

SYMBOL

V_CC

MIN

2.5

TYP

MAX

UNIT

ELECTRICAL CHARACTERISTICS (V_CC＝3V, T_A=25°C, unless otherwise specified)

PARAMETER

SYMBOL

V_CC

TEST CONDITIONS

MIN

2.5

TYP

MAX

UNIT

V_CCRange

Supply Current

(Does not conclude COMMON current )

I_CC

R_Z

R_R

V_IN=0V

0.2

0.5

Digital

Reading

Digital

DC characteristics Zero Input Reading

Ratio metric Reading

V_IN=0V,full-scale=200mV

V_IN=V_REF, V_REF=100mV

999

1000

± 0.2

1001

Reading

Linearity (MAX deviation form best

straight line fit)

full-scale=200.0mV or

full-scale=2.0V

-1

Counts

Rollover Error

E_R

-V_IN=+V_IN~200mV

V_IH=0V

± 0.2

Counts

Leakage Current Input

Low battery flag

V+ to V-

2.5

2.4

2.6

2.7

Analog Common Voltage

( with respect to V+ )

25kΩ Between Common

and Positive Supply

V_COM

2.5

2.6

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M7240

CMOS IC

TYPICAL APPLICATIONS CIRCUITS

LOW BAT

DATA HOLD

AB4

POL

V+

BP-

M7240

CPA+

GND

CAP-

HOLD

V-

HLDO

4.7uF

GND

0.22uF

330

0.47uF

100K

200

910

25K

0.47uF

INLO INHI

GND

Fig.1

Note ：R_Jis a zero resistance, proper value can eliminate zero salvage value.

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M7240

CMOS IC

APPLICATION INFORMATION

The M7240 is the production of the basic application of LCD digital DC voltage meter and digital multimeter, by

selecting different parameters of the external components, you can create different range gauge outfit. The 200mV

range gauge outfit which the most widely used because it is three and a half the basic components of digital

multimeter. As M7240 of 3V low-voltage power supply, making use M7240 production of the digital DC voltage meter

input signal can be a total of COM and common GND two access methods, Figure 1 is the 200mv typical application

circuit.

In Fig.1 circuit, when moving the jumper J is connected to INLO and COM, the composition of the input signal

connected in COM, when moving the jumper J is connected to INLO and GND, the composition of the input signal

connected in GND, for the production of digital multimeter, two input signal connection method in general to meet the

application requirements. Use the COM method to make the gauge outfit digital multimeter, the circuit is relatively

simple form, but because of COM client can tolerate a few mA maximum current, the need for greater measurement

poured into the current project, not applicable. Use the GND method to make the gauge outfit produced digital

multimeter, there is no current problem of affordability, but measurement converter circuit is slightly changed.

In addition, if you live in the city to use electricity for 60HZ, in order to reduce the frequency of the circuit city

electrical effects, the connection between the RX and power resistors, please use 680KΩ.

ANALOG COMMON

The COM pin is used to set the common-mod voltage for the system in which the input signals are floating with

respect to the power supply of the M7240. In most of the applications, INLO, RFLO and COM pins are tied to the

same point, so that the common mode voltage can be removed from the reference system and the converter.

The COM pin is also used as a voltage reference. It sets a voltage of around 2.5 volts more negative than the

positive supply.

The analog COM is tied internally to an NMOS capable of sinking 30mA. This NMOS will hold the COM voltage

at 2.5 volts when an external load attempts to pull the COM voltage toward the positive supply.

The source current of COM is only 10μA, so it is easy to pull COM voltage to a more negative voltage with

respect to the positive supply.

REFERENCE VOLTAGE

For a 1000 counts reading, the input signal must be equal to the reference voltage. As a result, it requires the

input signal be twice the reference voltage for a 2000 counts full-scale reading. Thus, for the 200.0mV and 2.000V

full-scale, the reference voltage should equal 100.0mV and 1.000V, In some applications the full-scale input voltage

my be other than 200mV or 2V, but 600mV. For example, the reference voltage should be set to 300mV and the

input signal can be used directly without being divided.

The differential reference can be used during the measurement of resistor by the ratio metric method and when

a digital reading of zero is desired for Vin≠0. A compensating offset voltage can be applied between COM and INLO

and the voltage of being measured is connected between COM and INHI.

AUTO-ZERO PHASE

During auto-zero three things happen. First, input high and low are disconnected from the pins and internally

shorted to analog COM. Second, the reference capacitor is charged to the reference voltage. Third, a feedback loop

is closed around the system to charge the auto-zero capacitor C_AZto compensate for offset voltages in the buffer

amplifier, integrator, and comparator. Since the comparator is included in the loop, the AZ accuracy is limited only by

the noise of the system. In any case, the offset referred to the input is less than 10μV.

SIGNAL INTEGRATE PHASE

During signal integrate phase, the auto-zero loop is opened, the internal short is removed, and the internal input

high and low are connected to the external pins. The converter then integrates the differential voltage between INHI

and INLO for a fixed time. This differential voltage can be within a wide common mode range: up to 1V from either

supply. if, on the other hand, the input signal has no return with respect to the converter power supply, INLO can be

tied to analog COM to establish the correct common mode voltage. At the end of this phase, the polarity of the

integrated signal is determined.

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M7240

CMOS IC

APPLICATION INFORMATION(Cont.)

DIFFERENTIAL INPUT

The input can accept differential voltages anywhere within the common mode range of the input amplifier, or

specifically from 0.5V below the positive supply to 1V above the negative supply. In this range, the system has a

CMRR of 86dB typical. However, care must be exercised to assure the integrator output does not saturate. A worst

case condition would be a large positive common mode voltage with a near full scale negative differential input

voltage. The negative input signal drives the integrator positive when most of its swing has been used up by the

positive common mode voltage. For these critical applications the integrator output swing can be reduced to less

than the recommended 2V full scale swing with little loss of accuracy. The integrator output can swing to within 0.3V

of either supply without loss of linearity.

REFERENCE VOLTAGE CAPACITOR

The reference voltage can be generated anywhere within the power supply voltage of the converter. The main

source of common mode error is a roll-over voltage caused by the reference capacitor losing or gaining charge to

stray capacity on its nodes. If there is a large common mode voltage, the reference capacitor can gain charge

(increase voltage) when called up to de-integrate a positive signal but lose charge (decrease voltage) when called up

to de-integrate a negative input signal. This difference in reference for positive or negative input voltage will give a

roll-over error. However, by selecting the reference capacitor such that it is large enough in comparison to the stray

capacitance, this error can be held to less than 0.5 count worst case.

COMPONENT VALUE SELECTION

INTEGRATING RESISTOR

Both the buffer amplifier and the integrator have a class A output stage with 100μA of quiescent current. They

can supply 4μA of drive current with negligible nonlinearity. The integrating resistor should be large enough to

remain in this very linear region over the input voltage range, but small enough that undue leakage requirements are

not placed on the PC board. For 2V full scale, 470kΩ is near optimum and similarly a 100kΩ for a 200mV scale.

INTEGRATING CAPACITOR

The integrating capacitor should be selected to give the maximum voltage swing that ensures tolerance buildup

will not saturate the integrator swing(approximately. 0.3V from either supply).In the M7240, when the analog

COMMON is used as a reference, a nominal+2V full scale integrator swing is fine. For three readings/second (48kHz

clock) nominal values for C_INTare 0.22μF and 0.10μF, respectively. Of course, if different oscillator frequencies are

used, these values should be changed in inverse proportion to maintain the same output swing.

An additional requirement of the integrating capacitor is that it must have a low dielectric absorptiont to prevent

roll-over errors. While other types of capacitors are adequate for this application, polypropylene capacitors give

undetectable errors at reasonable cost.

AUTO-ZERO CAPACITOR

The size of the auto-zero capacitor has some influence on the noise of the system. For 200mV full scale where

noise is very important, a 0.47μF capacitor is recommended. On the 2V scale, a 0.047μF capacitor increases the

speed of recovery from overload and is adequate for noise on this scale.

REFERENCE CAPACITOR

A 0.1μF capacitor gives good results in most applications. However, where a large common mode voltage exists

and a 200mV scale is used, a larger value is required to prevent roll-over error. Generally 1μF will hold the roll-over

error to 0.5 count in this instance.

UTC assumes no responsibility for equipment failures that result from using products at values that

exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or

other parameters) listed in products specifications of any and all UTC products described or contained

herein. UTC products are not designed for use in life support appliances, devices or systems where

malfunction of these products can be reasonably expected to result in personal injury. Reproduction in

whole or in part is prohibited without the prior written consent of the copyright owner. The information

presented in this document does not form part of any quotation or contract, is believed to be accurate

and reliable and may be changed without notice.

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M7240 [UTC]

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