Datasheet

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
Lead Free
Halogen Free
M7240L-QL1-Y
M7240G-QL1-Y
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Copyright © 2011 Unisonic Technologies Co., Ltd
Package
Packing
LQFP-44
Tray
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M7240
CMOS IC
„
PIN CONFIGURATIONS
„
PIN DESCRIPTION
PIN
1~3、41~44
4~9、21
10~13、18~20
14
15
16
NAME
A1~G1
A2~G2
A3~G3
AB4
POL
BP
TYPE
O
O
O
O
O
O
17
BP_
O
22
23
24
25
26
27
28
29
30
31
32
33
34
LB
VINT
BUF
AZ
INLO
INHI
COM
CRFCRF+
RFLO
RFHI
HLDO
O
I
I
I
I
35
Rx
-
36
37
38
39
40
HOLD
CAPGND
CAP+
V+
I
I
PIN DESCRIPTION
LCD segment drive
LCD segment drive
LCD segment drive
LCD segment drive
LCD Drive display minus "-"
LCD public driver
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
Integrator output
Integration register connection.
Auto-zero capacitor connection
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 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
7
SEGMENT
DECODE
7
SEGMENT
DECODE
7
SEGMENT
DECODE
÷200
LATCH
1000's
COUNTER
100's
COUNTER
10's
COUNTER
1's
COUNTER
TO SWITCH
DRIVERS
V+
osc
÷4
LOGIC CONTROL
VRFHI
CAPV- GEN
GND
LOW
BATTERY
DETECTOR
3-½ Digital A/D
Converter
CAP+
RFLO
INHI
INLO
ANALOG
COMMON
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COM
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CMOS IC
ABSOLUTE MAXIMUM RATING (unless otherwise specified)
PARAMETER
Power Supply Voltage(V+~V-)
SYMBOL
RATINGS
UNIT
VCC
7
V
Analog input voltage
VIANG
V+~VV
Reference Input Voltage
VIREF
V+~VV
Operating Temperature
TOPR
0 ~ 70
°C
Storage Temperature
TSTG
-65 ~ +150
°C
Junction Temperature
TJ
150
°C
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
VCC
MIN
2.5
TYP
3
MAX
6
UNIT
V
ELECTRICAL CHARACTERISTICS (VCC=3V, TA=25°C, unless otherwise specified)
PARAMETER
VCC Range
Supply Current
(Does not conclude COMMON current )
SYMBOL
VCC
TEST CONDITIONS
ICC
VIN=0V
DC characteristics Zero Input Reading
RZ
VIN=0V,full-scale=200mV
Ratio metric Reading
RR
VIN=VREF, VREF=100mV
Linearity (MAX deviation form best
straight line fit)
Rollover Error
Leakage Current Input
Low battery flag
Analog Common Voltage
( with respect to V+ )
L
ER
IL
VCOM
full-scale=200.0mV or
full-scale=2.0V
-VIN=+VIN~200mV
VIH =0V
V+ to V25kΩ Between Common
and Positive Supply
UNISONIC TECHNOLOGIES CO., LTD
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MIN
2.5
TYP
3
MAX
6
UNIT
V
0.2
0.5
mA
0
0
0
999
1000
1001
-1
± 0.2
+1
Counts
-1
2.5
± 0.2
1
2.6
+1
10
2.7
Counts
PA
V
2.4
2.5
2.6
V
Digital
Reading
Digital
Reading
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M7240
TYPICAL APPLICATIONS CIRCUITS
HD
D1
C1
A1
D2
D2
F1
C2
C2
F1
B2
B2
G1
A2
A2
E1
F2
F2
G1
E2
E2
E1
D3
B3
D3
F3
B3
F3
E3
BPBP
POL
AB4
A3
G3
C3
LB
B1
LOW BAT
DATA HOLD
G2
A1
E3
B1
AB4
C1
POL
D1
BP
G3
GND
A3
CAP-
C3
HOLD
LB
HLDO
CRF+
CRF-
INHI
COM
AZ
INLO
BUF
INT
4.7uF
0.22uF
RFHI
Rx
RFLO
G2
V-
GND
1M
Rj
330
100K
0.47uF
1M
GND
CPA+
1uF~4uF
V+
M7240
BP-
0.01uF
„
CMOS IC
910
200
25K
J
0.47uF
3V
INLO INHI
GND
Fig.1
Note :RJ is a zero resistance, proper value can eliminate zero salvage value.
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M7240
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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 CAZ to 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
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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 CINT are 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.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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