Source: https://www.scribd.com/document/149462678/IMPRIMIR-DATASHEET-1
Timestamp: 2019-04-20 08:57:13+00:00

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The Intersil ICL7139 and ICL7149 are high performance, low power, auto-ranging digital multimeter lCs. Unlike other autoranging multimeter ICs, the ICL7139 and ICL7149 always display the result of a conversion on the correct range. There is no “range hunting” noticeable in the display. The unit will autorange between the four different ranges. A manual switch is used to select the 2 high group ranges. DC current ranges are 4mA and 40mA in the low current group, and 400mA and 4A in the high current group. Resistance measurements are made on 4 ranges, which are divided into two groups. The low resistance ranges are 4/40kΩ . The high resistance ranges are 0.4/4MΩ . Resolution on the lowest range is 1Ω .
COM EXTERNAL RESISTORS AND CAPACITORS 3-34 .ICL7139. INTEGRATION AND COMPARATOR V+ V. ICL7149 Functional Block Diagram SWITCHES CRYSTAL OSC CONTROL LOGIC INCLUDING AUTORANGING LOGIC BEEPER DRIVER PIEZO ELECTRIC BEEPER DISPLAY DRIVER AND LATCHES COUNTERS DIGITAL COMMON DISPLAY POWER SUPPLY SECTION ANALOG SECTION ANALOG SWITCHES.
(Note 3) -50 V+ . 4. . 3. . .75 ±1 ±0. . Guaranteed by design. . . . . . . . . . . . 95% of Time) VIN = 0.00 (Notes 1 and 8) (Notes 1 and 8) (Notes 1 and 8) (Notes 1 and 8) (Notes 1 and 8) (Notes 1 and 8) (Notes 1 and 8) At 60Hz (Notes 5. . 3-35 . 4K and 4M Range Accuracy DC I. . . . . . . .-65oC to 150oC Maximum Lead Temperature (Soldering 10s) . . . . . 150oC Maximum Storage Temperature Range . 7. VREF = 1. . . Electrical Speciﬁcations PARAMETER Zero Input Reading V+ = 9V. 15V Reference Input Voltage (VREF to COM) . . .(Note 4) 7 6. . . . . .0 75 25 2 1. . . Temp. ICL7149 Absolute Maximum Ratings Supply Voltage (V+ to V-) . . . . .4 3. . .5 V.30 ±0. . .5 2. . (See Figure 14) TEST CONDITIONS VIN or IIN or RIN = 0.0 -1 2. . . . . . .8 VIN = V+ to V. . . . . . Adjusted for Full Scale Accuracy AC V Open Circuit Voltage for Ω Measurements Noise Noise Supply Current Analog Common (with Respect to V+) Temperature Coefficient of Analog Common Output Impedance of Analog Common Backplane/Segment Drive Voltage Backplane/Segment Display Frequency Switch Input Current Switch Input Levels (High Trip Point) Switch Input Levels (Mid Trip Point) Switch Input Levels (Low Trip Point) Beeper Output Drive (Rise or Fall Time) Beeper Output Frequency Continuity Detect Power Supply Functional Operation Low Battery Detect ±0. . .2 ±2 VREF 0. . . . . .5 TYP - MAX +00.5 9 7 NOTES: 1. 300oC (MQFP . 100µA Clock Input Swing. . . DC Voltage Range ICOMMON < 10µA ICOMMON < 10µA. . Applies to pins 17-20. V+ to V+ -3 Thermal Information Thermal Resistance (Typical. Noise is defined as the width of the uncertainty window (where the display will flicker) between two adjacent codes. AC V (Note 2. . . . . . . . Analog Common falls out of regulation when the Low Battery Detect is asserted. . . . . . This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this speciﬁcation is not implied. .5 100 11 7. 50 MQFP Package .1 4 1. . . . . . 400V Range Only Accuracy DC V.Lead Tips Only) Operating Conditions Temperature Range . 4K and 400K Range Accuracy Ω. . . .00V V+ to VV+ to V. 7. . . .ICL7139. NOTE: 1. . . . . θJA is measured with the component mounted on an evaluation PC board in free air. . . . . .5 UNITS V. . . . .2 +50 V+ V+ . VREF adjusted for -3. . . = 0oC To 70oC ICOMMON < 10µA Average DC < 50mV MIN -00. .0oC to 70oC CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. 6. . . . . . . . . . . . . . . . .7 2. . . test circuit as shown in Figure 3. . . . . . . . . For 50Hz use a 100kHz crystal. 80 Maximum Junction Temperature . . . . I. . . 5. however the ICL7139 and ICL7149 will continue to operate correctly with a supply voltage above 7V and below 11V. . . . . and rollover error. . . . . TA = 25oC. Crystal = 120kHz. . .2. linearity. . .700 reading on DC volts. . 2. 8.+ 3 VCLOAD = 10nF Range = Low Ω . . . . . . . . . . . . DC V (Note 2. . . 400V Range Excluded Accuracy Ω. . . RDG = Reading. . and 8) RUNKNOWN = Infinity VIN = 0. Accuracy is deﬁned as the worst case deviation from ideal input value including: offset. .+ 0. . . . . . . . . . . . . . . . . . 95% of Time) VIN = 0. ICL7139 only. Note 1) θJA (oC/W) PDIP Package . . not tested. . .75 2. .1 10 3. . . .0. . . . 3V Analog Input Current (IN + Current or IN + Voltage) . . .9 -100 1 3. . . . . . . Ω Counts % of RDG ±1 % of RDG ±1 % of RDG ±8 % of RDG ±9 % of RDG ±1 % of RDG ±1 % of RDG V LSB LSB mA V ppm/ oC Ω V Hz µA V V V µs kHz kΩ V V Linearity (Best Straight Line) (Note 6) Accuracy DC V. .0 +1 ±1 ±0. . . Unadjusted for Full Scale Accuracy DC I.5 V. . . . .
ICL7139. 3-36 . Example: pin 27. segment C0 is on backplane 2. ICL7149 Timing Waveform FIRST AUTO ZERO FIRST INTEGRATE FIRST DEINTEGRATE UNDERRANGE AUTO ZERO SECOND AUTO ZERO SECOND INTEGRATE SECOND DEINTEGRATE UNDERRANGE AUTO ZERO THIRD AUTO ZERO THIRD INTEGRATE THIRD DEINTEGRATE UNDERRANGE AUTO ZERO FOURTH AUTO ZERO FOURTH INTEGRATE FOURTH DEINTEGRATE AUTO ZERO 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 FIGURE 1. segments are listed as (segment for backplane 1)/(segment for backplane 2). LINE FREQUENCY CYCLES (1 CYCLE = 1000 INTERNAL CLOCK PULSES = 2000 OSCILLATION CYCLES) Pin Descriptions I/O O O O I I I O O I/O I/O I I I I I O I I I PIN NUMBER 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 DESCRIPTION Segment Driver POL/AC Backplane 2 Backplane 1 V+ VReference Input Lo Ω Hi Ω Deintegrate Analog Common Int I Int V/ Ω Triple Point Auto Zero Capacitor (CAZ) Integrate Capacitor (CINT) Beeper Output mA/ µA Ω /V/A Hi Ω DC/Lo Ω AC I/O I O I O O O O O O O O O O O O O PIN NUMBER 20 21 22 23 24 25 26 27 28 29 32 33 34 35 39 40 Hold Oscillator Out Oscillator In Segment DRIVER k/m Segment Driver Ω /A Segment Driver M Ω / µ A Segment Driver Lo Bat/V Segment Driver B0 /C0 Segment Driver A0 /D0 Segment Driver G0 /E0 Segment Driver A1 /D1 Segment Driver G1 /E1 Segment Driver F1 /DP1 Segment Driver B2 /C1 Segment Driver B3 /C3 Segment Driver ADG3 /E3 DESCRIPTION NOTE: For segment drivers. segment B0 is on backplane 1.
During the range 1 integrate period. DETAILED CIRCUIT DIAGRAM FOR DC VOLTAGE MEASUREMENT 3-37 .the autozero capacitor. The analog section contains the integrator. each measurement starts with an autozero (AZ) phase. The output of the integrator. which are gated out over a period of 1000 clock cycles to ensure good normal mode rejection of AC line interference. Range 1 Integrate a g d f e b kΩ MΩ c mAV µA AC DP3 DP2 DP1 The ICL7139 and ICL7149 perform a full autorange search for each reading. The input signal is integrated for 10 clock cycles. DIGIT 3 LOW BATT 2 1 0 DC Voltage Measurement Autozero Only those portions of the analog section which are used during DC voltage measurements are shown in Figure 3. The oscillator output is divided by two to generate the internal master clock.7V ANALOG COMMON COMMON + - T = (INT)(AR)(AZ) AR = AUTORANGE CHOPPER AZ = AUTOZERO INT = INTEGRATE 80µA V- FIGURE 3. the offset of the comparator is stored in ClNT . DISPLAY SEGMENT NOMENCLATURE RDEINT TRIPLE POINT CAZ CAZ CINT CINT RDEINT VIN INT V/ Ω RINTV T T AZ AZ DEINTAZ DEINTVREF AZ + INTEGRATOR - VREF DEINT+ DEINT+ + COMPARATOR TO LOGIC SECTION - V+ 6. The digital section is powered by V+ and Digital Common. comparator. ICL7149 Detailed Description General The Functional Block Diagram shows the digital section which includes all control logic. FIGURE 2. beginning with range 1. is stored on CAZ . Similarly. counters. which is equal to its offset. or one 50Hz line cycle with a 100kHz oscillator. internal switches connect the INT V/Ω terminal to the Triple Point (Pin 13). and several analog switches which are controlled by the digital logic. As shown in the timing diagram (Figure 1). The oscillator is also in the digital section.ICL7139. reference section. and display drivers. which is about 3V below V+. The autozero cycle equals 1000 clock cycles which is one 60Hz line cycle with a 120kHz oscillator. Normally 120kHz for rejection of 60Hz AC interference and 100kHz for rejection of 50Hz AC should be used. During this phase. analog buffers. the integrator and comparator are conﬁgured as unity gain buffers and their non-inverting inputs are connected to Common. The analog section is powered from V+ and V-.
When the voltage on CINT is reduced to zero (actually to the VOS of the comparator). except that the input signal is integrated during the full 1000 clock cycles (one line frequency cycle). 2 and 3 measurements. The result is displayed if the reading is greater than 360 counts.is asserted. Range 2 The range 2 measurement begins with an autozero cycle similar to the one that preceded range 1 integration. and the ICL7139 and ICL7149 then switch to range 2 . Autozero After ﬁnding the ﬁrst range for which the reading is above 360 counts. an underrange has occurred. The length of the autozero cycle is variable which results in a ﬁxed measurement period of 24.9Ω (LOW current ranges) RDEINT TRIPLE POINT CAZ CAZ CINT CINT RDEINT INT I LOW I I T AZ AZ DEINT- DEINTVREF RINTI T 9. The range 2 deintegrate cycle is identical to the range 1 deintegrate cycle. and a range 4 measurement is performed if the result is below 360 counts. This is done to maintain good normal mode rejection. If the CINT voltage zero-crossing does not occur before 4000 counts have elapsed.1Ω (HI current ranges). The result of this measurement is transferred to the output latches and displayed even if the reading is less than 360. When performing the range 2 cycle. The integrator capacitor CINT is then discharged with a current equal to VREF/RDElNT . Range 2 cycle length however.1Ω ANALOG COMMON COMMON 6. with the result being displayed only for readings greater than 360 counts. If the latched result is between 360 and 3999. the polarity of the voltage on the integrator capacitor (CINT) is checked. ICL7149 Range 1 Deintegrate At the beginning of the deintegrate cycle. “OL” (overload) is then displayed on the LCD. the display is updated and an autozero cycle is entered. The comparator monitors the voltage on CINT . the comparator output switches. Range 2 sensitivity is ten times greater than range 1 (100 vs 10 clock cycle integration) and the full scale voltage of range 2 is 40V. When the count is less than 360. Range 4 This measurement is similar to the range 1. the count is transferred to the output latches and is displayed. the ICL7139 and ICL7149 again asserts the internal underrange signal and proceeds to range 3. If the reading is below 360 counts. Range 3 The range 3V or 4V full scale measurement is identical to the range 2 measurement. The DC current measurements are very similar to DC voltage measurements except: 1) The input voltage is developed by passing the input current through a 0.000 clock cycles (24 line cycles). the overload ﬂag is set.the 40V scale. is one AC line cycle. DC Current Figure 4 shows a simpliﬁed block diagram of the analog section of the ICL7139 and ICL7149 during DC current measurement.9Ω VREF HIGH I AZ + INTEGRATOR AZ - + COMPARATOR TO LOGIC SECTION - DEINT+ DEINT+ V+ 0. DETAILED CIRCUIT DIAGRAM FOR DC CURRENT MEASUREMENT 3-38 .ICL7139. Underrange is asserted. except that the integration period is 10.000 clock cycles (10 line cycles) long. distributed throughout one line cycle. minus 360 clock cycles. and either the DElNT+ or DElNT.7V + - T = (INT)(AR)(AZ) AR = AUTORANGE CHOPPER AZ = AUTOZERO INT = INTEGRATE 80µA V- FIGURE 4. the signal is integrated for 100 clock cycles. or 9. and the current count is latched.
The AC measurement cycle is begun by disconnecting the integrator capacitor and using the integrator as an autozeroed comparator to detect the positive-going zero crossing. except in the DC current timing diagram. ClNT . rather than the 10MΩ value used for the RlNT V resistor.1107.7V ~ COMMON + - S = AZ • ACS • ACINT T = (INT + ACS) AZ AR ACS = AC SYNC AR = AUTORANGE CHOPPER AZ = AUTOZERO INT = INTEGRATE 80µA V- FIGURE 5. the voltage drop across the current sensing resistor is 40mV maximum on the 4mA and 400mA ranges. the AC input voltage is applied directly to the ICL7139 input resistor. Once synchronized to the AC input. This conversion factor is π/2√2 = 1. AC Voltage Measurement for ICL7139 As shown in Figure 5. As a result the deintegrate and autozero cycle times are reduced by 10%. With some increase in noise. Since the voltage on ClNT is proportional to the half-wave rectiﬁed average AC input voltage.ICL7139.000 clock cycles of integration are used. and the AC annunciator is enabled. It will autorange through two voltage ranges (400V and 40V). RDEINT CAZ TRIPLE POINT CINT CAZ CINT 5 ACINT D1 ACS D2 VREF D4 DEINTDEINT DEINT ~ INT V/Ω RINTV T T D3 ACINT AZ ACS AZ + INTEGRATOR AZ - + COMPARATOR - AC IN V+ 6. the ﬁrst and second integrate and deintegrate phases are skipped. AC current can also be measured with some simple modiﬁcations to either of the two circuits in Figures 6 and 7. and the system clock is manipulated to perform the RMS conversion. the autozero loop is closed and a normal integrate/deintegrate cycle begins. AC Voltage Measurement for ICL7149 The ICL7149 is designed to be used with an optional AC to DC voltage converter circuit. No separate AC to DC conversion circuitry is needed. DETAILED CIRCUIT DIAGRAM FOR AC VOLTAGE MEASUREMENT FOR ICL7139 ONLY 3-39 . while an RMS to DC converter is shown in Figure 7. 2) Only those ranges with 1000 and 10. a conversion factor must be applied to convert the reading to RMS. only positive current from the integrator ﬂows into the integrator capacitor. By using the lower value integration resistor. and only the 2 most sensitive ranges. Because diode D4 is in series with the integrator capacitor. The DC current measurement timing diagram is similar to the DC voltage measurement timing diagram. 400mV maximum on the 40mA and 4A scales. The ICL7139 resynchronizes itself to the AC input prior to every reading. 3) The RlNT l resistor is 1MΩ . these “burden” voltages can be reduced by lowering the value of both the current sense resistors and the RlNT l resistor proportionally. ICL7149 current sensing resistor. A typical averaging AC to DC converter is shown in Figure 6.
1µF 10 COMMON FIGURE 6.400VAC 50Hz .2µF + V+ 2.1000Hz 4 50kΩ ICL7652 8 1 7 10 2 43.0µF 100kΩ V+ V- 11 20MΩ VIN 0VAC .1000Hz 10MΩ 2 AD736 8 + 10µF 4. ICL7149 1.2µF 1 + 7 3 6 5 4 FULL SCALE ADJUST 5kΩ 12 INT (V/Ω) VIN 0VAC .1µF 11 20MΩ 4 ICL7149 7 10 2 8 ICL7652 5 + 1 0.2kΩ 5kΩ 12 FULL SCALE ADJUST INT (V/Ω) 100kΩ 5 + 0.1µF V+ V- 0.ICL7139.1µF COM 0. AC VOLTAGE MEASUREMENT USING OPTIONAL RMS CONVERTER CIRCUIT 3-40 .400VAC 0Hz . AC VOLTAGE MEASUREMENT USING OPTIONAL AVERAGING CIRCUIT 2.99kΩ V- V+ ICL7149 30kΩ 10 COM COMMON FIGURE 7.
5V and 3VP-P . shown in Figure 10. The crystal eliminates the need to trim the oscillator frequency. When the voltage across RX is less than approximately 100mV. An external signal may be capacitively coupled in OSC IN. LOΩ RKNOWN + Common Voltage The analog and digital common voltages of the ICL7139 and ICL7149 are generated by an on-chip resistor/zener/diode combination. CONTINUITY BEEPER DRIVE CIRCUIT 3-41 . 2) During the deintegrate phases. if desired. with an output impedance of 10Ω . When RKNOWN is 10kΩ . Analog common may be used to generate the reference voltage. and requires no other external components. V+ 80µA 6. the input voltage is the voltage across the reference resistor RKNOWN1 or RKNOWN2 . This voltage is then buffered to provide the analog common and the digital common voltages. the Ω measurements are split into two sets of ranges. or source 0. and the full scale ranges are 0. and the full scale ranges are 4kΩ and 40kΩ . The analog common buffer can sink about 20mA. HI Ω measurements use a 1MΩ reference resistor. Like the current measurements. ICL7149 RDEINT TRIPLE POINT CAZ CAZ CINT CINT RDEINT INT V/Ω RINTV T T AZ AZ AZ + INTEGRATOR AZ - + LOΩ RX RKNOWN 1 HIΩ RKNOWN 2 COMMON LOW Ω LOW Ω + - - DEINT+ DEINT+ COMPARATOR TO LOGIC SECTION + - VREF T = INT + DEINT AZ = AUTOZERO INT = INTEGRATE FIGURE 8.ICL7139. the beeper output will be on. The shunting effect of RINTV does not affect the reading because it cancels exactly between integration and deintegration. The measurement phases and timing are the same as the measurement phases and timing for DC current except: 1) During the integrate phases the input voltage is the voltage across the unknown resistor RX .1V ANALOG COMMON P (PIN 10) LOGIC SECTION 5K + + 180K - DIGITAL COMMON P (INTERNAL) LO BAT -+ 0. A pullup resistor to V+ may be used if more sourcing capability is desired. then effectively deintegrating the voltage across a known resistor (RKNOWN1 or RKNOWN2 of Figure 8). ANALOG AND DIGITAL COMMON VOLTAGE GENERATOR CIRCUIT - Oscillator The ICL7139 and ICL7149 use a parallel resonant-type crystal in a Pierce oscillator conﬁguration.7V 125K + 3V + 3.3V + V- HIΩ + - LOΩ VREF V+ BEEPER OUTPUT V+ FIGURE 10. The nominal voltage between V+ and analog common is 3V. The resistor values are chosen so the coefﬁcient of the diode voltage cancels the positive temperature coefﬁcient of the zener voltage. LO Ω measurements use a 10kΩ reference resistor. RX . the continuity circuit of Figure 9 will be active. DETAILED CIRCUIT DIAGRAM FOR RATIOMETRIC Ω MEASUREMENT Ratiometric Ω Measurement The ratiometric Ω measurement is performed by ﬁrst integrating the voltage across an unknown resistor.4MΩ and 4MΩ . and. Continuity Indication When the ICL7139 and ICL7149 are in the LO Ω measurement mode. Because the RUNKNOWN RX COM + - 2kHz VX VX = 100mV FIGURE 9.01mA. with a signal level between 0. as shown in Figure 11. the beeper output will be on when RX is less than 1kΩ .
when not externally connected. the logic level is the “Amps”. When connected to V-. loading on this pin should not exceed a single CMOS input. INTERNAL OSCILLATOR CIRCUIT DIAGRAM Display Drivers Figure 12 shows typical LCD Drive waveforms. one referenced to each backplane. or “Volts” state. see Table 2. In this case.06V SEGMENT OFF O 2VPEAK O (VOLTAGE ACROSS ON SEGMENT) VSEGMENT ON -2VPEAK VPEAK (VOLTAGE ACROSS OFF SEGMENT) VSEGMENT OFF O -VPEAK FIGURE 12. care must be taken when selecting external components.ICL7139. Annunciators are used to indicate polarity. Component Selection For optimum performance while maintaining the low-cost advantages of the ICL7139 and ICL7149. and RMS OFF voltage calculations. ICL7149 OSC OUT pin is not designed to drive large external loads.4VRMS threshold voltage should be used. Each drive line can drive two individual segments. The frequency should be 120kHz to reject 60Hz AC signals. The ICL7139 and ICL7149 drive 33/4 7-segment digits. The third voltage level needed for duplex drive waveforms is generated through an on-chip resistor string. This input is internally tied to the common voltage through a high-value resistor. Duplex multiplexing is used to minimize the number of connections between the ICL7139 and ICL7149 and the LCD. approximately 5µA of current ﬂows out of the input. Peak drive voltage across the display is approximately 3V. DUPLEXED LCD DRIVE WAVEFORMS 3-42 . the logic level is the “Ω”. and the range in use. and 11 annunciators. and 100kHz to reject 50Hz signals. or 3-level input. The DC component of the drive waveforms is guaranteed to be less than 50mV. When connected to V+. For other pins. 3 decimal points. The LCD has two separate backplanes. RMS ON. about 5µA of current ﬂows into the input. and will go to the middle. Here.37V RMS OFF → 1. or high state. The oscillator frequency is internally divided by two to generate the ICL7139 and ICL7149 clock. low battery condition. TERNARY INPUTS CONNECTIONS 5pF 10pF PIN NUMBER 17 18 19 20 V+ mA Ω HiΩ/DC Hold OPEN OR COM µA V LoΩ/AC Auto VTest Amps Test Test FIGURE 11. This section reviews speciﬁcations and performance effects of various external components. BACKPLANE VPEAK V+ VPEAK / 2 O DCOM VPEAK O VPEAK V RMS = 5 --V ON 8 PEAK 5 --V OFF 8 PEAK SEGMENT ON V RMS = VPEAK = 3V ±10% RMS ON → 2. An LCD with approximately 1. TABLE 2. or low state. OSC IN 5M 330K OSC OUT Ternary Input The Ω /Volts/Amps logic input is a ternary.
The integrator thus appears to have zero offset voltage. Other ﬁlm capacitors such as polyester. RDElNT should normally be the same value as RlNT V . the RMS ON voltage will be 2. and low battery annunciators. their ratio should be 10:1.3nF (0. and subtracts that voltage from the input signal during the integrate phases. With a 3V peak display voltage. Polypropylene capacitors add undetectable errors at a reasonable cost. Most display manufacturers supply a graph that shows contrast versus RMS drive voltage. These should normally be 10kΩ and 1MΩ .5%. This graph can be used to determine what the contrast ratio will be when driven by the ICL7139 and ICL7149. Deintegration Resistor. switches driving these inputs should be rated for low current. within 0. with an absolute accuracy of at least 0. These requirements set a lower limit of 0. Autozero Capacitor. The threshold at the maximum operating temperature should be checked to ensure that the “off” segments will not be turned “on” at high temperatures. Integrator voltage swing should be about ±2V when using standard component values. the CAZ voltage change should be less than 1/10 of a count during the 10. Saturation occurs when the integrator output is within 1V of either V+ or V-. RDElNT Unlike most dual-slope A/D converters.4V. polarity.000 x 2 x Oscillator Period ) × 0. Because the display voltage is not adjustable. For different RlNTV and oscillator frequencies the value of ClNT can be calculated from: ( Integrate Time ) × ( Integrate Current ) C INT = --------------------------------------------------------------------------------------------------( Desired Integrator Swing ) ( 10. CAZ The CAZ is charged to the integrator’s offset voltage during the autozero phases. Crystal The ICL7139 and ICL7149 are designed to use a parallel resonant 120kHz or 100kHz crystal with no additional external components. the display should have a 10% ON threshold of about 1.047µF for CAZ but 0.0033µF) ClNT with an oscillator frequency of 120kHz and an RlNTV of 10MΩ .05%. which is then measured using RlNT l.6W. the accuracy of ohm reading is primarily determined by the absolute accuracy of the RKNOWN1 and RKNOWN2 . 3) Charge injection from the internal autozero switches. If a few seconds of settling time upon power-up is acceptable. Display The ICL7139 and ICL7149 use a custom. Because RlNT V drives a virtual ground point. 2) CAZ self-discharge. The RS parameter should be less than 25kΩ to ensure oscillation. With a 100kHz oscillator frequency (for 50Hz line frequency rejection). which requires it to dissipate 1. Initial frequency tolerance of the crystal can be a relatively loose 0. Slight errors in matching may be corrected by trimming the reference voltage.000 count clock cycle integration period for the 400mV range. ClNT As with all dual-slope integrating convertors.9Ω current sensing resistors convert the measured current to a voltage. The ICL7139 and ICL7149 are designed to use a 3. the frequency needed to drive the transducer can be calculated by dividing the crystal frequency by 60.06V maximum. provided it does not have excessive leakage. RMS OFF voltage will be 1. or “dry” operations. Also. and the 1 line cycle time period allotted to autozero.1µF is the preferred value. The beeper output off state is at the V+ rail. 3-43 . Some carbon composition resistors have a large voltage coefﬁcient which will cause linearity errors on the 400V scale. the ICL7139 and ICL7149 use different resistors for integration and deintegration. The class “A” output of the integrator begins to have nonlinearities if required to sink more than 70µA (the sourcing limit is much higher). The upper limit on the value of CAZ is set by the time constant of the autozero loop. the CAZ may be a ceramic capacitor. polystyrene. To avoid errors. The two resistors must be closely matched. Most display thresholds decrease with increasing temperature.37V minimum. The 0.05%. Integrator Resistors The normal values of the RlNT V and RlNT l resistors are 10MΩ and 1MΩ respectively. with a voltage output swing of V+ to V-. while polystyrene and polycarbonate may be used in less critical applications. and have the same temperature coefﬁcient. Ohm Measurement Resistors Because the ICL7139 and ICL7149 use a ratiometric ohm measurement technique. ICL7149 Integrator Capacitor. Switches Because the logic input draws only about 5µA. the integration capacitor must have low dielectric absorption to reduce linearity errors. and the ratio between RlNT l and these two resistors must be accurate . duplexed drive display with range. and polycarbonate introduce negligible errors. CAZ may be several 10s of µF before approaching this limit. the input impedance of the meter is equal to R lNT V . some carbon composition resistors are very noisy. When crystals with different frequencies are used. Continuity Beeper The Continuity Beeper output is designed to drive a piezoelectric transducer at 2kHz (using a 120kHz crystal).5%. Though their absolute values are not critical.normally 0.1Ω resistor must be capable of handling the full scale current of 4A.1Ω and 9. Voltage swing should be as high as possible without saturating the integrator. and be able to handle voltages in excess of 400VAC .4V/R INTV = ------------------------------------------------------------------------------------------------------------------------( 2V ) The ideal CAZ is a low leakage polypropylene or Teﬂon capacitor. unless the value of the current sensing resistors are trimmed. Minimum CAZ value is determined by: 1) Circuit leakages.ICL7139. Current Sensing Resistors The 0. The switches on the external inputs must be able to reliably switch low currents. ClNT and RINTV affects the voltage swing of the integrator.
3.about 100PPM/oC. part number PKM24-4A0 (or Equivalent). both the ICL7139 and ICL7149 and their external components could be damaged under such fault conditions.2W or 4. no additional protection circuitry is required. While minimizing external component count.1µF 13 3. Examples. fast-blow fuses should be used between S5A in Figure 14 and the 0. 10K 10M ICL8069 10K 1M TRIPLE POINT DEINTEGRATE INTEGRATE VOLT/ Ω INTEGRATE CURRENT EXTERNAL REFERENCE REFERENCE INPUT ANALOG COMMON FIGURE 13. Meter Protection The ICL7139 and ICL7149 and their external circuitry should be protected against accidental application of 110/220V AC line voltages on the Ω and current ranges. Multimeter protection components have not been shown. Beeper is from muRata. BASIC MULTIMETER APPLICATION CIRCUIT FOR ICL7139 AND ICL7149 3-44 . Crystal is a Statek or SaRonix CX-IV type.7µF + 10kΩ TANT COMMON 30K50K V ICL8069 PIN 10 V+ µA V+ VmA Ω 18 A S4B 17 20 S3 S2 CLOSED: HIΩ-DC S3 CLOSED: HOLD READING NOTES: 1. 4. The following sections discuss the functions of speciﬁc components and various options. For the current ranges. the 10kΩ resistor connected to pin 7 must be able to dissipate 1. Without the necessary precautions. V+ 10M Applications. To improve the tempco. ICL7149 Reference Voltage Source A voltage divider connected to V+ and Common is the simplest source of reference voltage.8W for short periods of time during accidental application of 110V or 220VAC line voltages respectively. The reference voltage source output impedance must be ≤ RDElNT/4000. and Hints A complete autoranging 33/4 digit multimeter is shown in Figure 14. However.ICL7139.1Ω and 9. For the Ω ranges.9Ω ICL7149 0. Display is from LXD.3nF 120kHz CRYSTAL 21 22 mAVµA 14 15 INPUTS V/Ω V S4A A S5A A µA mA Ω TRIPLE CAZ CINT OSC OSC OUT IN POINT 9 DEINT DISPLAY 10MΩ 12 DRIVE INT (V/Ω) OUTPUTS 10kΩ 7 LOΩ 1MΩ 8 HIΩ BEEPER 1MΩ 11 INT (I) V+ ICL7139 9. 2. an ICL8069 bandgap reference may be used (see Figure 13). EXTERNAL VOLTAGE REFERENCE CONNECTION TO ICL7139 AND ICL7149 10MΩ 0. FIGURE 14.9Ω shunt resistors.1Ω 2W 10 COMMON V/Ω/A mA/µA VVREF HIΩ-DC/LOΩ-AC HOLD LO BAT 1-3 23-40 AC 16 4 + + 1µF ON/OFF 5 6 19 S3 V+ V+ 9V BATTERY BEEPER kΩMΩ PIN 4 10kΩ S1 4. this approach will provide the same voltage tempco as the ICL7139 and ICL7149 Common . part number 38D8R02H (or Equivalent).
Information furnished by Intersil is believed to be accurate and reliable. Boards should be properly cleaned after soldering. Intersil products are sold by description only. leakages. and guarding when designing the PCB for a ICL7139 and ICL7149 based multimeter. PC BOARD LAYOUT 9 10 11 12 13 14 15 Rollover Performance.com 3-45 . Leakages. nor for any infringements of patents or other rights of third parties which may result from its use. The analog circuitry should be removed or shielded from any 120V AC power inputs. (see Figure 15) which is driven by the output of the integrator. Accordingly. Areas of particular importance are: 1) The INT V/Ω and INT l Pins. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries. it is essential that the PCB have low leakage. The conversion scheme used by the ICL7139 and ICL7149 changes the common mode voltage on the integrator and the capacitors CAZ and ClNT during a positive deintegrate cycle. Stray Pickup FIGURE 15. no responsibility is assumed by Intersil or its subsidiaries for its use. the reader is cautioned to verify that data sheets are current before placing orders.intersil. Stray capacitance to ground is charged when this occurs. 2) The Triple Point. Rollover error is not seen as gain error. thus reducing magnetically coupled interference coming from power transformers. 3) The RDElNT and the CAZ pins. and Guarding Because the ICL7139 and ICL7149 system measures very low currents. assembled and tested under ISO9000 quality systems certiﬁcation. removing some of the charge on ClNT and causing rollover error. or other sources. see web site http://www. Keeping the analog circuit section close to the ICL7139 and ICL7149 will also help keep the area free of any loops. Guarding these nodes with the output of the integrator reduces the stray capacitance to ground. the analog circuitry should be as close as possible to the ICL7139 and ICL7149. However. All Intersil semiconductor products are manufactured. any stray coupling will affect the AC reading. the guarding should be used on both sides of the PC board. For information regarding Intersil Corporation and its products. If possible. Rollover error increases about 1 count for each picofarad of capacitance between CAZ or the Triple Point and ground. The ICL7139 and ICL7149 will read -1 when approximately -100µV is applied. While the ICL7139 and ICL7149 have excellent rejection of line frequency noise and pickup in the DC ranges. Intersil Corporation reserves the right to make changes in circuit design and/or speciﬁcations at any time without notice. and is seen as a zero offset for positive voltages. Generally. The ICL7139 and ICL7149 will thus read zero until several hundred microvolts are applied in the positive direction.ICL7139. The rollover error causes the width of the +0 count to be larger than normal. The rollover error can be minimized by guarding the Triple Point and CAZ nodes with a trace connected to the ClNT pin. ICL7149 Printed Circuit Board Layout Considerations Particular attention must be paid to rollover performance. and any AC sources such as LCD drive waveforms. which minimizes the charge error on ClNT and CAZ .
com Datasheets for electronic components. .This datasheet has been downloaded from: www.DatasheetCatalog.

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