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 www.unisonic.com.tw Copyright © 2011 Unisonic Technologies Co., Ltd Package Packing LQFP-44 Tray 1 of 7 QW-R502-682.a 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. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 2 of 7 QW-R502-682.a 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 UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw COM 3 of 7 QW-R502-682.a M7240 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 www.unisonic.com.tw 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 4 of 7 QW-R502-682.a 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. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 5 of 7 QW-R502-682.a 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 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. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 6 of 7 QW-R502-682.a 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 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 7 of 7 QW-R502-682.a