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ICL7109IJL Datasheet(PDF) 8 Page - Intersil Corporation |
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ICL7109IJL Datasheet(HTML) 8 Page - Intersil Corporation |
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8 / 25 page  8 Detailed Description Analog Section Figure 2 shows the equivalent circuit of the Analog Section for the ICL7109. When the RUN/HOLD input is left open or connected to V+, the circuit will perform conversions at a rate determined by the clock frequency (8192 clock periods per cycle). Each measurement cycle is divided into three phases as shown in Figure 3. They are (1) auto-zero (A-Z), (2) signal integrate (INT) and (3) de-integrate (DE). Auto-Zero Phase During auto-zero three things happen. First, input high and low are disconnected from the pins and internally shorted to analog COMMON. 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 A-Z accuracy is limited only by the noise of the system. In any case, the offset referred to the input is less than 10 µV. Signal Integrate Phase During signal integrate, 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 IN HI and IN LO for a fixed time. This differential voltage can be within a wide common mode range of the inputs. At the end of this phase, the polarity of the integrated signal is determined. FIGURE 1B. TYPICAL CONNECTION DIAGRAM PARALLEL INTERFACE WITH 8048 MICROCOMPUTER FIGURE 1. 9 25 26 40 39 / 5 20 5 6 17 26 19 18 40 1 2 V+ TEST 3 - 8 B9 - B12, 9 - 16 STATUS HBEN CE/LOAD 28 39 38 37 36 35 34 33 32 31 30 29 26 24 23 21 REF IN - REF CAP- REF CAP+ REF IN+ IN HI IN LO COMMON INT AZ BUF REF OUT V- RUN/HOLD OSC SEL OSC OUT OSC IN GND GND 1 µF 0.01 µF 0.33 µF 0.15 µF CAZ CINT RINT 1M Ω 3.58MHz CRYSTAL - + + INPUT GND EXTERNAL REFERENCE -5V GND - 20k Ω 0.2V REF 200k Ω 2V REF +5V OR OPEN GND / / 6 8 B1 - B8 1 4 7 8 11 20 XTAL1 TO RESET EA WR ALE GND 28 30 29 27 10 XTAL2 P12 P11 P10 RD P13 +5V 8 / 27 25 22 MODE SEND BUFF OSC OUT +5V +5V SS INT 2 RUN/HOLD LBEN POL,OR 12 - 19 DB0 - DB7 31 - 34 P14 - P17 35 - 38 P20 - P27 / 8 21 - 24 OTHER I/O GND PSEN GND PROG VDD VCC +5V TL +5V +5V +5V ICL7109 8748/9048 3 +5V ICL7109 |
Similar Part No. - ICL7109IJL |
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Similar Description - ICL7109IJL |
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