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| ICL7109 August 1997 12-Bit, MicroprocessorCompatible A/D Converter Description The ICL7109 is a high performance, CMOS, low power integrating A/D converter designed to easily interface with microprocessors. The output data (12 bits, polarity and over-range) may be directly accessed under control of two byte enable inputs and a chip select input for a single parallel bus interface. A UART handshake mode is provided to allow the ICL7109 to work with industry-standard UARTs in providing serial data transmission. The RUN/HOLD input and STATUS output allow monitoring and control of conversion timing. The ICL7109 provides the user with the high accuracy, low noise, low drift versatility and economy of the dual-slope integrating A/D converter. Features like true differential input and reference, drift of less than 1V/oC, maximum input bias current of 10pA, and typical power consumption of 20mW make the ICL7109 an attractive per-channel alternative to analog multiplexing for many data acquisition applications. Features * 12-Bit Binary (Plus Polarity and Over-Range) Dual Slope Integrating Analog-to-Digital Converter * Byte-Organized, TTL Compatible Three-State Outputs and UART Handshake Mode for Simple Parallel or Serial Interfacing to Microprocessor Systems * RUN/HOLD Input and STATUS Output Can Be Used to Monitor and Control Conversion Timing * True Differential Input and Differential Reference * Low Noise (Typ) . . . . . . . . . . . . . . . . . . . . . . . . 15VP-P * Input Current (Typ). . . . . . . . . . . . . . . . . . . . . . . . . . .1pA * Operates At Up to 30 Conversions/s * On-Chip Oscillator Operates with Inexpensive 3.58MHz TV Crystal Giving 7.5 Conversions/s for 60Hz Rejection. May Also Be Used with An RC Network Oscillator for Other Clock Frequencies Ordering Information PART NUMBER ICL7109MDL ICL7109IDL ICL7109IJL ICL7109CPL ICL7109MDL/883B ICL7109IPL TEMP. RANGE (oC) -55 to 125 -25 to 85 -25 to 85 0 to 70 -55 to 125 -25 to 85 PACKAGE 40 Ld SBDIP 40 Ld SBDIP 40 Ld CERDIP 40 Ld PDIP 40 Ld SBDIP 40 Ld PDIP PKG. NO. D40.6 D40.6 F40.6 E40.6 D40.6 E40.6 Pinout ICL7109 (CERDIP, PDIP, SBDIP) TOP VIEW GND STATUS POL OR B12 B11 B10 B9 B8 1 2 3 4 5 6 7 8 9 40 V+ 39 REF IN 38 REF CAP37 REF CAP+ 36 REF IN+ 35 IN HI 34 IN LO 33 COMMON 32 INT 31 AZ 30 BUF 29 REF OUT 28 V27 SEND 26 RUN/HOLD 25 BUF OSC OUT 24 OSC SEL 23 OSC OUT 22 OSC IN 21 MODE B7 10 B6 11 B5 12 B4 13 B3 14 B2 15 B1 16 TEST 17 LBEN 18 HBEN 19 CE/LOAD 20 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 321-724-7143 | Copyright (c) Intersil Corporation 1999 File Number 3092.1 5-4 ICL7109 Absolute Maximum Ratings Positive Supply Voltage (GND to V+) . . . . . . . . . . . . . . . . . . . . +6.0V Negative Supply Voltage (GND to V-). . . . . . . . . . . . . . . . . . . . . .-9V Analog Input Voltage (Either Input) (Note 1). . . . . . . . . . . . . V+ to VReference Input Voltage (Either Input) (Note 1) . . . . . . . . . . V+ to VDigital Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (V+) +0.3V Pins 2-27 (Note 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .GND -0.3V Thermal Information Thermal Resistance (Typical, Note 1) JA (oC/W) JC (oC/W) SBDIP Package . . . . . . . . . . . . . . . . . . . . 60 20 CERDIP Package . . . . . . . . . . . . . . . . . . 55 18 PDIP Package . . . . . . . . . . . . . . . . . . . . . 50 N/A Maximum Junction Temperature (PDIP Package). . . . . . . . . . 150oC Maximum Junction Temperature (CERDIP Package) . . . . . . . 175oC Maximum Storage Temperature Range . . . . . . . . . .-65oC to 150oC Maximum Lead Temperature (Soldering 10s Max) . . . . . . . . . 300oC Operating Conditions Temperature Range M Suffix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -55oC to 125oC I Suffix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -25oC to 85oC C Suffix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0oC to 75oC CAUTION: Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device. 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. NOTE: 1. JA is measured with the component mounted on an evaluation PC board in free air. Analog Electrical Specifications PARAMETER SYSTEM PERFORMANCE Oscillator Output Current High, OOH Low, OOL Buffered Oscillator Output Current High, BOOH Low, BOOL Zero Input Reading Ratiometric Error Non-Linearity V+ = +5V, V- = -5V, GND = 0V, TA = 25oC, fCLK = 3.58MHz, Unless Otherwise Specified TEST CONDITIONS MIN TYP MAX UNIT VOUT = 2.5V VOUT = 2.5V - 1 1.5 - mA mA VOUT = 2.5V VOUT = 2.5V VIN = 0.0000V, VREF = 204.8mV VlN = VREF, VREF = 204.8mV (Note 7) Full Scale = 409.6mV to 2.048mV Maximum Deviation from Best Straight Line Fit, Over Full Operating Temperature Range (Notes 4 and 6) Full Scale = 409.6mV to 2.048V Difference in Reading for Equal Positive and Negative Inputs Near Full Scale (Notes 5 and 6), R1 = 0 Full-Scale = 200mV or Full Scale = 2V Maximum Deviation from Best Straight Line Fit (Note 4) -0000 -3 -1 2 5 0000 0.2 +0000 0 +1 mA mA Counts Counts Counts Rollover Error -1 0.2 +1 Counts Linearity - 0.2 50 - 1 (V+) -2.0 - Counts V/V V V pA pA pA nA V/oC Common Mode Rejection Ratio, CMRR VCM = 1V, VIN = 0V, Full Scale = 409.6mV Input Common Mode Range, VCMR Input HI, Input LO, Common (Note 4) (V-) +2.0 - Noise, eN VIN = 0V, Full-Scale = 409.6mV (Peak-to-Peak Value Not Exceeded 95% of Time) VlN = 0V, All Devices at 25oC (Note 4) 0oC to 70oC (Note 4) -25oC to 85oC (Note 4) -55oC to 125oC VlN = 0V, R1 - 0 (Note 4) 15 Leakage Current Input, IILK ICL7109CPL ICL7109IDL ICL7109MDL Zero Reading Drift - 1 20 100 2 0.2 10 100 250 100 1 5-5 ICL7109 Analog Electrical Specifications PARAMETER Scale Factor Temperature Coefficient V+ = +5V, V- = -5V, GND = 0V, TA = 25oC, fCLK = 3.58MHz, Unless Otherwise Specified (Continued) TEST CONDITIONS VIN = 408.9mV = > 77708 Reading Ext. Ref. 0ppm/oC (Note 4) MIN TYP 1 MAX 5 UNIT ppm/oC REFERENCE VOLTAGE Ref Out Voltage, VREF Ref Out Temperature Coefficient POWER SUPPLY CHARACTERISTICS Supply Current V+ to GND, I+ Supply Current V+ to V-, ISUPP VIN = 0V, Crystal Osc 3.58MHz Test Circuit Pins 2 - 21, 25, 26, 27, 29; Open 700 700 1500 1500 A A Referred to V+, 25k Between V+ and REF OUT 25k Between V+ and REF OUT (Note 4) -2.4 -2.8 80 -3.2 V ppm/oC Digital Electrical Specifications PARAMETER DIGITAL OUTPUTS Output High Voltage, VOH Output Low Voltage, VOL Output Leakage Current Control I/O Pullup Current V+ = +5V, V- = -5V, GND = 0V, TA = 25oC, Unless Otherwise Specified TEST CONDITIONS MIN TYP MAX UNIT IOUT = 100A Pins 2 - 16, 18, 19, 20 IOUT = 1.6mA Pins 2 - 16, 18, 19, 20 Pins 3 - 16 High Impedance Pins 18, 19, 20 VOUT = V+ -3V MODE Input at GND (Note 4) HBEN Pin 19 LBEN Pin 18 (Note 4) 3.5 - 4.3 0.20 0.01 5 - 0.40 1 - V V A A Control I/O Loading DIGITAL INPUTS Input High Voltage, VIH Input Low Voltage, VIL Input Pull-Up Current Input Pull-Up Current Input Pull-Down Current TIMING CHARACTERISTICS MODE Input Pulse Width, tW - 50 pF Pins 18 - 21, 26, 27 Referred to GND Pins 18 - 21, 26, 27 Referred to GND Pins 26, 27 VOUT = (V+) -3V Pins 17, 24 VOUT = (V+) -3V Pin 21 VOUT = GND +3V 3.0 - 5 25 5 1 - V V A A A (Note 4) 50 - - ns NOTES: 1. Input voltages may exceed the supply voltages provided the input current is limited to 100A. 2. Due to the SCR structure inherent in the process used to fabricate these devices, connecting any digital inputs or outputs to voltages greater than V+ or less than GND may cause destructive device latchup. For this reason it is recommended that no inputs from sources other than the same power supply be applied to the ICL7109 before its power supply is established, and that in multiple supply systems the supply to the ICL7109 be activated first. 3. This limit refers to that of the package and will not be obtained during normal operation. 4. This parameter is not production tested, but is guaranteed by design. 5. Roll-over error for TA = -55oC to 125oC is 10 counts (Max). 6. A full scale voltage of 2.048V is used because a full scale voltage of 4.096V exceeds the devices Common Mode Voltage Range. 7. For CERDIP package the Ratiometric error can be -4 (Min). 5-6 ICL7109 Pin Descriptions PIN 1 2 SYMBOL GND STATUS DESCRIPTION Digital Ground, 0V. Ground return for all digital logic. Output High during integrate and deintegrate until data is latched. Output Low when analog section is in Auto-Zero configuration. Polarity - HI for positive input. Overrange - HI if overranged. Bit 12 Bit 11 Bit 10 Bit 9 Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 (Most Significant Bit) High = True High = True High = True High = True High = True High = True High = True High = True High = True High = True (Least Significant Bit) Three-State Output Data Bits Three-State Output Data Bits Three-State Output Data Bits Three-State Output Data Bits Three-State Output Data Bits Three-State Output Data Bits Three-State Output Data Bits Three-State Output Data Bits Three-State Output Data Bits Three-State Output Data Bits Three-State Output Data Bits Three-State Output Data Bits Three-State Output Data Bits Three-State Output Data Bits 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 POL OR B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 TEST Input High - Normal Operation. Input Low - Forces all bit outputs high. Note: This input is used for test purposes only. Tie high if not used. Low Byte Enable - With Mode (Pin 21) low, and CE/LOAD (Pin 20) low, taking this pin low activates low order byte outputs B1 through B8. With Mode (Pin 21) high, this pin serves as a low byte flag output used in handshake mode. See Figures 7, 8, 9. High Byte Enable - With Mode (Pin 21) low, and CE/LOAD (Pin 20) low, taking this pin low activates high order byte outputs B9 through B12, POL, OR. With Mode (Pin 21) high, this pin serves as a high byte flag output used in handshake mode. See Figures 7, 8, 9. Chip Enable Load - With Mode (Pin 21) low. CE/LOAD serves as a master output enable. When high, B1 through B12, POL, OR outputs are disabled. With Mode (Pin 21) high, this pin serves as a load strobe used in handshake mode. See Figures 7, 8, 9. Input Low - Direct output mode where CE/LOAD (Pin 20), HBEN (Pin 19) and LBEN (Pin 18) act as inputs directly controlling byte outputs. Input Pulsed High - Causes immediate entry into handshake mode and output of data as in Figure 9. Input High - Enables CE/LOAD (Pin 20), HBEN (Pin 19), and LBEN (Pin 18) as outputs, handshake mode will be entered and data output as in Figures 7 and 8 at conversion completion. Oscillator Input Oscillator Output 18 LBEN 19 HBEN 20 CE/LOAD 21 MODE 22 23 OSC IN OSC OUT 5-7 ICL7109 Pin Descriptions PIN 24 (Continued) DESCRIPTION Oscillator Select - Input high configures OSC IN, OSC OUT, BUF OSC OUT as RC oscillator - clock will be same phase and duty cycle as BUF OSC OUT. Input low configures OSC IN, OSC OUT for crystal oscillator - clock frequency will be 1/58 of frequency at BUF OSC OUT. Buffered Oscillator Output Input High - Conversions continuously performed every 8192 clock pulses. Input Low - Conversion in progress completed, converter will stop in Auto-Zero 7 counts before integrate. Input - Used in handshake mode to indicate ability of an external device to accept data. Connect to +5V if not used. Analog Negative Supply - Nominally -5V with respect to GND (Pin 1). Reference Voltage Output - Nominally 2.8V down from V+ (Pin 40). Buffer Amplifier Output. Auto-Zero Node - Inside foil of CAZ . Integrator Output - Outside foil of CINT . Analog Common - System is Auto-Zeroed to COMMON. Differential Input Low Side. Differential Input High Side. Differential Reference Input Positive. Reference Capacitor Positive. Reference Capacitor Negative. Differential Reference Input Negative. Positive Supply Voltage - Nominally +5V with respect to GND (Pin 1). SYMBOL OSC SEL 25 26 BUF OSC OUT RUN/HOLD 27 SEND 28 29 30 31 32 33 34 35 36 37 38 39 40 VREF OUT BUFFER AUTO-ZERO INTEGRATOR COMMON INPUT LO INPUT HI REF IN + REF CAP + REF CAPREF INV+ NOTE: All digital levels are positive true. 5-8 ICL7109 Design Information Summary Sheet * OSCILLATOR FREQUENCY fOSC = 0.45/RC COSC > 50pF; ROSC > 50k fOSC (Typ) = 60kHz or fOSC (Typ) = 3.58MHz Crystal * OSCILLATOR PERIOD tOSC = RC/0.45 tOSC = 1/3.58MHz (Crystal) * INTEGRATION CLOCK FREQUENCY fCLOCK = fOSC (RC Mode) fCLOCK = fOSC/58 (Crystal) tCLOCK = 1/fCLOCK * INTEGRATION PERIOD tINT = 2048 x tCLOCK * 60/50Hz REJECTION CRITERION tINT/t60Hz or tlNT/t50Hz = Integer * OPTIMUM INTEGRATION CURRENT IINT = 20A * FULL-SCALE ANALOG INPUT VOLTAGE VlNFS Typically = 200mV or 2V * INTEGRATE RESISTOR V INFS R INT = ---------------I INT * VINT MAXIMUM SWING (V- + 0.5V) < VINT < (V+ - 0.5V) VINT (Typ) = 2V * DISPLAY COUNT V IN COUNT = 2048 x ---------------V REF * CONVERSION CYCLE tCYC = tCL0CK x 8192 (In Free Run Mode, Run/HOLD = 1) when fCLOCK = 60kHz, tCYC = 133ms * COMMON MODE INPUT VOLTAGE (V- + 2.0V) < VlN < (V+ - 2V) * AUTO-ZERO CAPACITOR 0.01F < CAZ < 1F * REFERENCE CAPACITOR 0.1F < CREF < 1F * VREF Biased between V+ and VVREF V+ - 2.8V Regulation lost when V+ to V- 6.4V. If VREF is not used, float output pin. * POWER SUPPLY: DUAL 5.0V V+ = +5V to GND V- = -5V to GND * OUTPUT TYPE Binary Amplitude with Polarity and Overrange Bits Tips: Always tie TEST pin HIGH. Don't leave any inputs floating. * INTEGRATE CAPACITOR ( t INT ) ( I INT ) C INT = ------------------------------V INT * INTEGRATOR OUTPUT VOLTAGE SWING ( t INT ) ( I INT ) V INT = ------------------------------C INT Typical Integrator Amplifier Output Waveform (INT Pin) AUTO ZERO PHASE (COUNTS) 6143 - 2048 INTEGRATE PHASE FIXED 2048 COUNTS DE-INTEGRATE PHASE 0 - 4095 COUNTS TOTAL CONVERSION TIME = 8192 x tCLOCK (IN FREE-RUN MODE) 5-9 ICL7109 +5V 1 V+ XTAL 40 GND 1 GND BUF OSC 25 OUT 2 STATUS V+ 40 REF IN - 39 REF CAP- 38 REF CAP+ 37 REF IN+ 36 19 HBEN GND +5V 6 14 FE 15 OE +5V 16 SFD 26 - 33 31 TBR 1 - 8 TRE 24 DRR 18 8 / 8 / / IN HI 35 IN LO 34 COMMON 3-8 B9 - B12, POL,OR INT 9 - 16 AZ B1 - B8 BUF 17 TEST 18 LBEN 33 32 31 30 CAZ 0.33F RINT -5V 20k 0.2V REF 200k 2V REF CINT 0.15F 1M 0.01F 1F +5V 1000pF +5V 2 OSC CONTROL XTAL 17 GND +5V 3 GND 4 RRD EPE 39 CLS1 38 CLS2 37 5 - 12 RBR 1 - 8 13 PE SBS 36 PI 35 CLR 34 - GND EXTERNAL REFERENCE + + INPUT - GND +5V REF OUT 29 V- 28 20 RRI SERIAL INPUT DR 19 21 MODE RUN/HOLD 26 +5V OR OPEN TBRL 23 TBRE 22 20 CE/LOAD 27 SEND OSC SEL 24 OSC OUT 23 OSC IN 22 GND 3.58MHz CRYSTAL 25 TRO SERIAL OUTPUT IM6403 CMOS UART MR 21 GND ICL7109 CMOS A/D CONVERTER FOR LOWEST POWER CONSUMPTION TBR1 - TBR8 INPUTS SHOULD HAVE 100k PULLUP RESISTORS TO +5V FIGURE 1A. TYPICAL CONNECTION DIAGRAM UART INTERFACE-TO TRANSMIT LATEST RESULT, SEND ANY WORD TO UART +5V 2 XTAL1 1 TO 4 RESET 5 SS 6 INT 3 XTAL2 +5V GND +5V 40 V+ 1 GND 17 TEST REF IN - 39 REF CAP- 38 REF CAP+ 37 1F - GND EXTERNAL REFERENCE + 21 - 24 35 - 38 P20 - P27 31 - 34 P14 - P17 8748/9048 REF IN+ 36 / 8 OTHER I/O ICL7109 IN HI 35 IN LO 34 COMMON 33 INT 32 AZ 31 26 RUN/HOLD 2 STATUS 18 LBEN 19 HBEN BUF 30 REF OUT 29 V- 28 SEND 27 RUN/HOLD 26 6 8 3-8 B9 - B12, POL,OR 9 - 16 B1 - B8 20 CE/LOAD BUFF OSC OUT 25 OSC SEL 24 OSC OUT 23 OSC IN 22 MODE 21 3.58MHz CRYSTAL GND -5V +5V +5V OR OPEN CAZ 0.33F RINT CINT 0.15F 1M 0.01F + - INPUT GND 7 EA 8 WR 9 PSEN 11 ALE / 5 GND P13 30 P12 29 P11 28 P10 27 +5V +5V +5V +5V 25 PROG 26 VDD 39 TL 40 VCC 20k 0.2V REF 200k 2V REF / GND 20 GND 12 - 19 DB0 - DB7 RD 10 8 / / FIGURE 1B. TYPICAL CONNECTION DIAGRAM PARALLEL INTERFACE WITH 8048 MICROCOMPUTER FIGURE 1. 5-10 ICL7109 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 10V. 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. CREF De-Integrate Phase The final phase is de-integrate, or reference integrate. Input low is internally connected to analog COMMON and input high is connected across the previously charged (during auto-zero) reference capacitor. Circuitry within the chip ensures that the capacitor will be connected with the correct polarity to cause the integrator output to return to zero crossing (established in Auto-Zero) with a fixed slope. The time required for the output to return to zero is proportional to the input signal. Differential Input The input can accept differential voltages anywhere within the common mode range of the input amplifier, or specifically from 1V below the positive supply to 1.5V 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 4V full scale swing with little loss of accuracy. The integrator output can swing to within 0.3V of either supply without loss of linearity. RINT CAZ CINT INT 32 COMPARATOR TO ZERO CROSS DETECTOR DIGITAL SECTION CREF+ 37 REF IN+ 36 A-Z REF IN39 A-Z CREF 38 BUFFER 30 A-Z 31 + - + - + BUFFER 35 IN HI INT DEDE+ INTEGRATOR A-Z AZ FROM CONTROL LOGIC DIGITAL SECTION A-Z 10A INT DE+ DE- 33 COMMON DE+ A-Z DE() DE- + 6.2V 34 IN LO INT 29 REF OUT 28 V- 40 V+ FIGURE 2. ANALOG SECTION OF ICL7109 5-11 ICL7109 The ICL7109 has, however, been optimized for operation with analog common near digital ground. With power supplies of +5V and -5V, this allows a 4V full scale integrator swing positive or negative thus maximizing the performance of the analog section. Differential Reference 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 deintegrate a positive signal but lose charge (decrease voltage) when called up to deintegrate 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 large enough in comparison to the stray capacitance, this error can be held to less than 0.5 count worst case. (See Component Value Selection.) The roll-over error from these sources is minimized by having the reference common mode voltage near or at analog COMMON. Component Value Selection For optimum performance of the analog section, care must be taken in the selection of values for the integrator capacitor and resistor, auto-zero capacitor, reference voltage, and conversion rate. These values must be chosen to suit the particular application. The most important consideration is that the integrator output swing (for full-scale input) be as large as possible. For example, with 5V supplies and COMMON connected to GND, the normal integrator output swing at full scale is 4V. Since the integrator output can go to 0.3V from either supply without significantly affecting linearity, a 4V integrator output swing allows 0.7V for variations in output swing due to component value and oscillator tolerances. With 5V supplies and a common mode range of 1V required, the component values should be selected to provide 3V integrator output swing. Noise and roll-over will be slightly worse than in the 4V case. For larger common mode voltage ranges, the integrator output swing must be reduced further. This will increase both noise and roll-over errors. To improve the performance, supplies of 6V may be used. Integrating Resistor Both the buffer amplifier and the integrator have a class A output stage with 100A of quiescent current. They supply 20A 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 409.6mV fullscale, 200k is near optimum and similarly a 20k for a 409.6mV scale. For other values of full scale voltage, RINT should be chosen by the relation : full scale voltage R INT = ------------------------------------------- . 20A TeflonTM is a trademark of DuPont Corporation Integrating Capacitor The integrating capacitor CINT should be selected to give the maximum voltage swing that ensures tolerance build-up will not saturate the integrator swing (approximately. 0.3V from either supply). For the ICL7109 with 5V supplies and analog common connected to GND, a 3.5V to 4V integrator output swing is nominal. For 71/2 conversions per second (61.72kHz clock frequency) as provided by the crystal oscillator, nominal values for CINT and CAZ are 0.15F and 0.33F, respectively. If different clock frequencies are used, these values should be changed to maintain the integrator output swing. In general, the value CINT is given by: ( 2048 x clock period ) ( 20A ) C INT = -------------------------------------------------------------------------------- . integrator output voltage swing An additional requirement of the integrating capacitor is that it have low dielectric absorption to prevent roll-over errors. While other types of capacitors are adequate for this application, polypropylene capacitors give undetectable errors at The integrating capacitor should have a low dielectric absorption to prevent roll-over errors. While other types may be adequate for this application, polypropylene capacitors give undetectable errors at reasonable cost up to 85oC. TeflonTM capacitors are recommended for the military temperature range. While their dielectric absorption characteristics vary somewhat from unit to unit, selected devices should give less than 0.5 count of error due to dielectric absorption. Auto-Zero Capacitor The size of the auto-zero capacitor has some influence on the noise of the system: a smaller physical size and a larger capacitance value lower the overall system noise. However, CAZ cannot be increased without limits since it, in parallel with the integrating capacitor forms an R-C time constant that determines the speed of recovery from overloads and the error that exists at the end of an auto-zero cycle. For 409.6mV full scale where noise is very important and the integrating resistor small, a value of CAZ twice CINT is optimum. Similarly for 4.096V full scale where recovery is more important than noise, a value of CAZ equal to half of CINT is recommended. For optimal rejection of stray pickup, the outer foil of CAZ should be connected to the R-C summing junction and the inner foil to pin 31. Similarly the outer foil of CINT should be connected to pin 32 and the inner foil to the R-C summing junction. Teflon, or equivalent, capacitors are recommended above 85oC for their low leakage characteristics. Reference Capacitor A 1F capacitor gives good results in most applications. However, where a large reference common mode voltage exists (i.e., the reference low is not at analog common) and a 409.6mV scale is used, a large value is required to prevent roll-over error. Generally 10F will hold the roll-over error to 0.5 count in this instance. Again, Teflon, or equivalent capacitors should be used for temperatures above 85oC for their low leakage characteristics. 5-12 ICL7109 Reference Voltage The analog input required to generate a full scale output of 4096 counts is VIN = 2VREF . For normalized scale, a reference of 2.048V should be used for a 4.096V full scale, and 204.8mV should be used for a 0.4096V full scale. However, in many applications where the A/D is sensing the output of a transducer, there will exist a scale factor other than unity between the absolute output voltage to be measured and a desired digital output. For instance, in a weighing system, the designer might like to have a full scale reading when the voltage from the transducer is 0.682V. Instead of driving the input down to 409.6mV, the input voltage should be measured directly and a reference voltage of 0.341V should be used. Suitable values for integrating resistor and capacitor are 33k and 0.15F. This avoids a divider on the input. Another advantage of this system occurs when a zero reading is desired for non-zero input. Temperature and weight measurements with an offset or tare are examples. The offset may be introduced by connecting the voltage output of the transducer between common and analog high, and the offset voltage between common and analog low, observing polarities carefully. However, in processor-based systems using the ICL7109, it may be more efficient to perform this type of scaling or tare subtraction digitally using software. Reference Sources The stability of the reference voltage is a major factor in the overall absolute accuracy of the converter. The resolution of the ICL7109 at 12 bits is one part in 4096, or 244ppm. Thus if the reference has a temperature coefficient of 80ppm/oC (onboard reference) a temperature difference of 3oC will introduce a one-bit absolute error. For this reason, it is recommended that an external highquality reference be used where the ambient temperature is not controlled or where high-accuracy absolute measurements are being made. The ICL7109 provides a REFerence OUTput (Pin 29) which may be used with a resistive divider to generate a suitable reference voltage. This output will sink up to about 20mA without significant variation in output voltage, and is provided with a pullup bias device which sources about 10A. The output voltage is nominally 2.8V below V+, and has a temperature coefficient of 80ppm/oC (Typ). When using the onboard reference, REF OUT (Pin 29) should be connected to REF- (Pin 39), and REF+ should be connected to the wiper of a precision potentiometer between REF OUT and V+. The circuit for a 204.8mV reference is shown in the test circuit. For a 2.048mV reference, the fixed resistor should be removed, and a 25k precision potentiometer between REF OUT and V+ should be used. Note that if Pins 29 and 39 are tied together and Pins 39 and 40 accidentally shorted (e.g., during testing), the reference supply will sink enough current to destroy the device. This can be avoided by placing a 1k resistor in series with Pin 39. Detailed Description Digital Section The digital section includes the clock oscillator and scaling circuit, a 12-bit binary counter with output latches and TTLcompatible three-state output drivers, polarity, over-range and control logic, and UART handshake logic, as shown in Figure 4. Throughout this description, logic levels will be referred to as "low" or "high". The actual logic levels are defined in the Electrical Specifications Table. For minimum power consumption, all inputs should swing from GND (low) to V+ (high). Inputs driven from TTL gates should have 3-5k pullup resistors added for maximum noise immunity. POLARITY DETECTED INTEGRATOR OUTPUT AZ PHASE I INTERNAL CLOCK INT PHASE II ZERO CROSSING OCCURS ZERO CROSSING DETECTED DEINT PHASE III AZ INTERNAL LATCH STATUS OUTPUT 2048 COUNTS MINIMUM FIXED 2048 COUNTS 4096 COUNTS MAX AFTER ZERO CROSSING ANALOG SECTION WILL BE IN AUTOZERO CONFIGURATION NUMBER OF COUNTS TO ZERO CROSSING PROPORTIONAL TO VIN FIGURE 3. CONVERSION TIMING (RUN/HOLD PIN HIGH) 5-13 ICL7109 MODE Input The MODE input is used to control the output mode of the converter. When the MODE pin is low or left open (this input is provided with a pulldown resistor to ensure a low level when the pin is left open), the converter is in its "Direct" output mode, where the output data is directly accessible under the control of the chip and byte enable inputs. When the MODE input is pulsed high, the converter enters the UART handshake mode and outputs the data in two bytes, then returns to "direct" mode. When the MODE input is left high, the converter will output data in the handshake mode at the end of every conversion cycle. (See section entitled "Handshake Mode" for further details). STATUS Output During a conversion cycle, the STATUS output goes high at the beginning of Signal Integrate (Phase II), and goes low one-half clock period after new data from the conversion has been stored in the output latches. See Figure 3 for of this timing. This signal may be used as a "data valid" flag (data never changes while STATUS is low) to drive interrupts, or for monitoring the status of the converter. RUN/HOLD Input When the RUN/HOLD input is high, or left open, the circuit will continuously perform conversion cycles, updating the output latches after zero crossing during the Deintegrate (Phase III) portion of the conversion cycle (See Figure 3). In this mode of operation, the conversion cycle will be performed in 8192 clock periods, regardless of the resulting value. LOW ORDER BYTE OUTPUTS B 8 9 B 7 B 6 B 5 B 4 B 3 B 2 B 1 HIGH ORDER BYTE OUTPUTS TEST 17 POL 3 OR 4 5 BBBB 12 11 10 9 6 7 8 10 11 12 13 14 15 16 18 19 20 LBEN HBEN CE/LOAD 14 THREE-STATE OUTPUTS 14 LATCHES 12-BIT COUNTER LATCH CLOCK COMP OUT AZ INT DEINT (+) DEINT (-) 2 STATUS TO ANALOG SECTION CONVERSION CONTROL LOGIC OSCILLATOR AND CLOCK CIRCUITRY HANDSHAKE LOGIC 26 RUN/ HOLD 22 23 24 25 21 27 SEND 1 GND OSC OSC OSC BUF MODE IN OUT SEL OSC OUT FIGURE 4. DIGITAL SECTION DEINT TERMINATED AT ZERO CROSSING DETECTION AUTOZERO PHASE I MIN 1790 COUNTS MAX 2041 COUNTS STATIC IN HOLD STATE INT PHASE II INTEGRATOR OUTPUT INTERNAL CLOCK INTERNAL LATCH STATUS OUTPUT RUN/HOLD INPUT 7 COUNTS FIGURE 5. RUN/HOLD OPERATION 5-14 ICL7109 If RUN/HOLD goes low at any time during Deintegrate (Phase III) after the zero crossing has occurred, the circuit will immediately terminate Deintegrate and jump to Auto-Zero. This feature can be used to eliminate the time spent in Deintegrate after the zero-crossing. If RUN/HOLD stays or goes low, the converter will ensure minimum Auto-Zero time, and then wait in Auto-Zero until the RUN/HOLD input goes high. The converter will begin the Integrate (Phase II) portion of the next conversion (and the STATUS output will go high) seven clock periods after the high level is detected at RUN/HOLD. See Figure 5 for details. Using the RUN/HOLD input in this manner allows an easy "convert on demand" interface to be used. The converter may be held at idle in auto-zero with RUN/HOLD low. When RUN/HOLD goes high the conversion is started, and when the STATUS output goes low the new data is valid (or transferred to the UART; see Handshake Mode). RUN/HOLD may now be taken low which terminates deintegrate and ensures a minimum Auto-Zero time before the next conversion. Alternately, RUN/HOLD can be used to minimize conversion time by ensuring that it goes low during Deintegrate, after zero crossing, and goes high after the hold point is reached. The required activity on the RUN/HOLD input can be provided by connecting it to the Buffered Oscillator Output. In this mode the conversion time is dependent on the input value measured. Also refer to Intersil Application Note AN032 for a discussion of the effects this will have on Auto-Zero performance. If the RUN/HOLD input goes low and stays low during AutoZero (Phase I), the converter will simply stop at the end of Auto-Zero and wait for RUN/HOLD to go high. As above, Integrate (Phase II) begins seven clock periods after the high level is detected. Direct Mode When the MODE pin is left at a low level, the data outputs (bits 1 through 8 low order byte, bits 9 through 12, polarity and over-range high order byte) are accessible under control of the byte and chip enable terminals as inputs. These three inputs are all active low, and are provided with pullup resistors to ensure an inactive high level when left open. When the chip enable input is low, taking a byte enable input low will allow the outputs of that byte to become active (three-stated on). This allows a variety of parallel data accessing techniques to be used, as shown in the section entitled "Interfacing." The timing requirements for these outputs are shown in Figure 6 and Table 1. It should be noted that these control inputs are asynchronous with respect to the converter clock - the data may be accessed at any time. Thus it is possible to access the latches while they are being updated, which could lead to erroneous data. Synchronizing the access of the latches with the conversion cycle by monitoring the STATUS output will prevent this. Data is never updated while STATUS is low. HIGH BYTE DATA LOW BYTE DATA = HIGH IMPEDANCE TABLE 1. DIRECT MODE TIMING REQUIREMENTS (See Note 4 of Electrical Specifications) DESCRIPTION Byte Enable Width Data Access Time from Byte Enable Data Hold Time from Byte Enable Chip Enable Width Data Access Time from Chip Enable Data Hold Time from Chip Enable SYMBOL tBEA MIN 350 TYP 220 MAX UNITS ns tDAB - 210 350 ns tDHB - 150 300 ns tCEA 400 260 - ns tDAC - 260 400 ns tDHC - 240 400 ns tCEA CE/LOAD AS INPUT tBEA HBEN AS INPUT LBEN AS INPUT tDAB DATA VALID tDAC DATA VALID tDHC tDHB DATA VALID FIGURE 6. DIRECT MODE OUTPUT TIMING Handshake Mode The handshake output mode is provided as an alternative means of interfacing the ICL7109 to digital systems where the A/D converter becomes active in controlling the flow of data instead of passively responding to chip and byte enable inputs. This mode is specifically designed to allow a direct interface between the ICL7109 and industry-standard UARTs (such as the Intersil IM6402/3) with no external logic required. When triggered into the handshake mode, the ICL7109 provides all the control and flag signals necessary to sequentially transfer two bytes of data into the UART and initiate their transmission in serial form. This greatly eases the task and reduces the cost of designing remote data acquisition stations using serial data transmission. 5-15 ICL7109 Entry into the handshake mode is controlled by the MODE pin. When the MODE terminal is held high, the ICL7109 will enter the handshake mode after new data has been stored in the output latches at the end of a conversion (See Figures 7 and 8). The MODE terminal may also be used to trigger entry into the handshake mode on demand. At any time during the conversion cycle, the low to high transition of a short pulse at the MODE input will cause immediate entry into the handshake mode. If this pulse occurs while new data is being stored, the entry into handshake mode is delayed until the data is stable. While the converter is in the handshake mode, the MODE input is ignored, and although conversions will still be performed, data updating will be inhibited (See Figure 9) until the converter completes the output cycle and clears the handshake mode. When the converter enters the handshake mode, or when the MODE input is high, the chip and byte enable terminals become TTL-compatible outputs which provide the control signals for the output cycle (See Figures 7, 8, and 9). In handshake mode, the SEND input is used by the converter as an indication of the ability of the receiving device (such as a UART) to accept data. Figure 7 shows the sequence of the output cycle with SEND held high. The handshake mode (Internal MODE high) is entered after the data latch pulse, and since MODE remains high the CE/LOAD, LBEN and HBEN terminals are active as outputs. The high level at the SEND input is sensed on the same high to low internal clock edge that terminates the data latch pulse. On the next low to high internal clock edge the CE/LOAD and the HBEN outputs assume a low level, and the high-order byte (Bits 9 through 12, POL, and OR) outputs are enabled. The CE/LOAD output remains low for one full internal clock period only, the data outputs remain active for 11/2 internal clock periods, and the high byte enable remains low for two clock periods. Thus the CE/LOAD output low level or low to high edge may be used as a synchronizing signal to ensure valid data, and the byte enable as an output may be used as a byte identification flag. With SEND remaining high the converter completes the output cycle using CE/LOAD and LBEN while the low order byte outputs (bits 1 through 8) are activated. The handshake mode is terminated when both bytes are sent. Figure 8 shows an output sequence where the SEND input is used to delay portions of the sequence, or handshake to ensure correct data transfer. This timing diagram shows the relationships that occur using an industry-standard IM6402/3 CMOS UART to interface to serial data channels. In this interface, the SEND input to the ICL7109 is driven by the TBRE (Transmitter Buffer Register Empty) output of the UART, and the CE/LOAD terminal of the ICL7109 drives the TBRL (Transmitter Buffer Register Load) input to the UART. The data outputs are paralleled into the eight Transmitter Buffer Register inputs. INTEGRATOR OUTPUT INTERNAL CLOCK INTERNAL LATCH STATUS OUTPUT MODE INPUT ZERO CROSSING OCCURS ZERO CROSSING DETECTED MODE HIGH ACTIVATES UART CE/LOAD, HBEN, LBEN INTERNAL NORM MODE SEND INPUT CE/LOAD HBEN HIGH BYTE DATA LBEN LOW BYTE DATA = DON'T CARE SEND SENSED SEND SENSED TERMINATES UART MODE MODE LOW, NOT IN HANDSHAKE MODE DISABLES OUTPUTS CE/LOAD, HBEN, LBEN DATA VALID DATA VALID = THREE-STATE HIGH IMPEDANCE = THREE-STATE WITH PULLUP FIGURE 7. HANDSHAKE WITH SEND HELD HIGH 5-16 ICL7109 Assuming the UART Transmitter Buffer Register is empty, the SEND input will be high when the handshake mode is entered after new data is stored. The CE/LOAD and HBEN terminals will go low after SEND is sensed, and the high order byte outputs become active. When CE/LOAD goes high at the end of one clock period, the high order byte data is clocked into the UART Transmitter Buffer Register. The UART TBRE output will now go low, which halts the output cycle with the HBEN output low, and the high order byte outputs active. When the UART has transferred that data to the Transmitter Register and cleared the Transmitter Buffer Register, the TBRE returns high. On the next ICL7109 internal clock high to low edge, the high order byte outputs are disabled, and one-half internal clock later, the HBEN output returns high. At the same time, the CE/LOAD and LBEN outputs go low, and the low order byte outputs become active. Similarly, when the CE/LOAD returns high at the end of one clock period, the low order data is clocked into the UART Transmitter Buffer Register, and TBRE again goes low. When TBRE returns to a high it will be sensed on the next ICL7109 internal clock high to low edge, disabling the data outputs. One-half internal clock later, the handshake mode will be cleared, and the CE/LOAD, HBEN and LBEN terminals return high and stay inactive (as long as MODE stays high). With the MODE input remaining high as in these examples, the converter will output the results of every conversion except those completed during a handshake operation. By triggering the converter into handshake mode with a low to high edge on the MODE input, handshake output sequences may be performed on demand. Figure 9 shows a handshake output sequence triggered by such an edge. In addition, the SEND input is shown as being low when the converter enters handshake mode. In this case, the whole output sequence for the first (high order) byte is similar to the sequence for the second byte. This diagram also shows the output sequence taking longer than a conversion cycle. Note that the converter still makes conversions, with the STATUS output and RUN/HOLD input functioning normally. The only difference is that new data will not be latched when in handshake mode, and is therefore lost. Oscillator The ICL7109 is provided with a versatile three terminal oscillator to generate the internal clock. The oscillator may be overdriven, or may be operated with an RC network or crystal. The OSCILLATOR SELECT input changes the internal configuration of the oscillator to optimize it for RC or crystal operation. When the OSCILLATOR SELECT input is high or left open (the input is provided with a pullup resistor), the oscillator is configured for RC operation, and the internal clock will be of the same frequency and phase as the signal at the BUFFERED OSCILLATOR OUTPUT. The resistor and capacitor should be connected as in Figure 10. The circuit will oscillate at a frequency given by f = 0.45/RC. A 100k resistor is recommended for useful ranges of frequency. For optimum 60Hz line rejection, the capacitor value should be chosen such that 2048 clock periods is close to an integral multiple of the 60Hz period (but should not be less than 50pF). ZERO CROSSING OCCURS ZERO CROSSING DETECTED INTEGRATOR OUTPUT INTERNAL CLOCK INTERNAL LATCH STATUS OUTPUT MODE INPUT UART INTERNAL NORM MODE SEND INPUT (UART TBRE) CE/LOAD OUTPUT (UART TBRL) HBEN HIGH BYTE DATA LBEN LOW BYTE DATA = DON'T CARE SEND SENSED SEND SENSED TERMINATES UART MODE DATA VALID DATA VALID = THREE-STATE HIGH IMPEDANCE FIGURE 8. HANDSHAKE - TYPICAL UART INTERFACE TIMING 5-17 ICL7109 When the OSCILLATOR SELECT input is low a feedback device and output and input capacitors are added to the oscillator. In this configuration, as shown in Figure 11, the oscillator will operate with most crystals in the 1MHz to 5MHz range with no external components. Taking the OSCILLATOR SELECT input low also inserts a fixed /58 divider circuit between the BUFFERED OSCILLATOR OUTPUT and the internal clock. Using an inexpensive 3.58MHz TV crystal, this division ratio provides an integration time given by: tINT = (2048 clock periods) x (tCLOCK) = 33.18ms where: 58 t CLOCK = ------------------------3.58MHZ left open. When OSCILLATOR SELECT is at GND, the clock will be a factor of 58 below the input frequency. When using the ICL7109 with the IM6403 UART, it is possible to use one 3.58MHz crystal for both devices. The BUFFERED OSCILLATOR OUTPUT of the ICL7109 may be used to drive the OSCILLATOR INPUT of the UART, saving the need for a second crystal. However, the BUFFERED OSCILLATOR OUTPUT does not have a great deal of drive capability, and when driving more than one slave device external buffering should be used. Test Input When the TEST input is taken to a level halfway between V+ and GND, the counter output latches are enabled, allowing the counter contents to be examined anytime. When the RUN/HOLD is low and the TEST input is connected to GND, the counter outputs are all forced into the high state, and the internal clock is disabled. When the RUN/HOLD returns high and the TEST input returns to the 1/ (V+ - GND) voltage (or to V+) and one clock is applied, all 2 the counter outputs will be clocked to the low state. This allows easy testing of the counter and its outputs. This time is very close to two 60Hz periods or 33ms. The error is less than one percent, which will give better than 40dB 60Hz rejection. The converter will operate reliably at conversion rates of up to 30 per second, which corresponds to a clock frequency of 245.8kHz. If at any time the oscillator is to be overdriven, the overdriving signal should be applied at the OSCILLATOR INPUT, and the OSCILLATOR OUTPUT should be left open. The internal clock will be of the same frequency, duty cycle, and phase as the input signal when OSCILLATOR SELECT is POSITVE TRANSITION CAUSES ENTRY INTO UART MODE INTERNAL CLOCK INTERNAL LATCH STATUS OUTPUT MODE INPUT INTERNAL MODE SEND INPUT CE/LOAD OUTPUT HBEN HIGH BYTE DATA LBEN LOW BYTE DATA = DON'T CARE = THREE-STATE HIGH IMPEDANCE DATA VALID UART NORM SEND SENSED SEND SENSED ZERO CROSSING OCCURS ZERO CROSSING DETECTED LATCH PULSE INHIBITED IN UART MODE STATUS OUTPUT UNCHANGED IN UART MODE DEINT PHASE III SEND SENSED TERMINATES UART MODE DATA VALID = THREE-STATE WITH PULLUP FIGURE 9. HANDSHAKE TRIGGERED BY MODE 5-18 ICL7109 V+ CLOCK /58 24 OSC SEL 22 OSC IN 23 OSC OUT R V+ OR OPEN C GND CRYSTAL 25 BUFFERED OSC OUT 24 OSC SEL 22 OSC IN 23 OSC OUT 25 BUFFERED OSC OUT OSC = 0.45/RC FIGURE 10. RC OSCILLATOR FIGURE 11. CRYSTAL OSCILLATOR CHIP SELECT 1 GND MODE CE/LOAD B9 - B12 POL, OR ICL7109 ANALOG IN B1 - B8 8 ANALOG IN RUN/HOLD HBEN LBEN CONVERT 6 GND MODE CE/LOAD B1 - B12 POL, OR ICL7109 ANALOG IN 14 GND MODE CHIP SELECT CE/LOAD B9 - B12 POL, OR 6 ICL7109 B1 - B8 8 RUN/HOLD HBEN LBEN CONVERT GND OR CHIP SELECT 2 RUN/HOLD HBEN LBEN CONVERT CONTROL BYTE FLAGS FIGURE 12A. FIGURE 12B. FIGURE 12. DIRECT MODE CHIP AND BYTE ENABLE COMBINATIONS FIGURE 12C. CONVERTER SELECT CONVERTER SELECT 8-BIT BUS CONVERTER SELECT GND MODE CE/LOAD B9 - B12 POL, OR ICL7109 ANALOG IN HBEN B1 - B8 RUN/HOLD LBEN 8 6 GND MODE CE/LOAD B9 - B12 POL, OR ICL7109 ANALOG IN +5V HBEN B1 - B8 RUN/HOLD LBEN 8 6 GND MODE CE/LOAD B9 - B12 POL, OR ICL7109 ANALOG IN +5V HBEN B1 - B8 RUN/HOLD LBEN 8 +5V 6 BYTE SELECT FLAGS FIGURE 13. THREE-STATE SEVERAL ICL7109'S TO A SMALL BUS 5-19 ICL7109 ADDRESS BUS CONTROL BUS DATA BUS GND MODE CE/LOAD B9 - B12 POL, OR RUN/HOLD ICL7109 B1 - B8 STATUS SEE TEXT HBEN GND LBEN 8 RD 6 +5V PB7 - PB0 PC5 WR D7 - D0 A0 - A1 CS PA5 - PA0 8255 (MODE 0) 8008, 8080 8085, 8048, ETC. ANALOG IN FIGURE 14. FULL-TIME PARALLEL INTERFACE TO 8040/80/85 MICROPROCESSORS ADDRESS BUS CONTROL BUS DATA BUS GND MODE CE/LOAD B9 - B12 POL, OR RD 6 WR D7 - D0 A0 - A1 CS PA5 - PA0 PC6 ANALOG IN RUN/HOLD ICL7109 B1 - B8 8 STBA PB7 - PB0 8255 8008, 8080 8085, 8048, ETC. INTRA STATUS HBEN GND LBEN 1F 10k +5V SEE TEXT PC4 PC6 INTR FIGURE 15. FULL-TIME PARALLEL INTERFACE TO 8048/80/85 MICROPROCESSORS WITH INTERRUPT 5-20 ICL7109 Test Circuit GND 1 GND 2 STATUS 3 POL 4 OR HIGH ORDER BYTE OUTPUTS 5 B12 6 B11 7 B10 8 B9 9 B8 10 B7 11 B6 LOW ORDER BYTE OUTPUTS 12 B5 13 B4 14 B3 15 B2 16 B1 +5V BYTE CONTROL INPUTS 17 TEST 18 LBEN 19 HBEN 20 CE/LOAD V+ 40 REF IN - 39 REF CAP- 38 REF CAP+ 37 REF IN+ 36 IN HI 35 IN LO 34 COMMON 33 INT 32 AZ 31 BUF 30 REF OUT 29 V- 28 SEND 27 RUN/HOLD 26 BUF OSC OUT 25 OSC SEL 24 OSC OUT 23 OSC IN 22 MODE 21 3.5795MHz TV CRYSTAL GND 24k V+ CAZ 0.33F RINT -5V 1k REF IN + REF IN CINT 0.15F 1M 0.01F R1 1F +5V DIFFERENTIAL REFERENCE + INPUT HIGH INPUT LOW GND RINT = 20k FOR 0.2V REF = 200k FOR 2.0V REF Typical Applications Direct Mode Interfacing Figure 12 shows some of the combinations of chip enable and byte enable control signals which may be used when interfacing the ICL7109 to parallel data lines. The CE/LOAD input may be tied low, allowing either byte to be controlled by its own enable as in Figure 12A. Figure 12B shows a configuration where the two byte enables are connected together. In this configuration, the CE/LOAD serves as a chip enable, and the HBEN and LBEN may be connected to GND or serve as a second chip enable. The 14 data outputs will all be enabled simultaneously. Figure 12C shows the HBEN and LBEN as flag inputs, and CE/LOAD as a master enable, which could be the READ strobe available from most microprocessors. Figure 13 shows an approach to interfacing several ICL7109s to a bus, connecting the HBEN and LBEN signals of several converters together, and using the CE/LOAD inputs (perhaps decode from an address) to select the desired converter. Some practical circuits utilizing the parallel three-state output capabilities of the ICL7109 are shown in Figures 14 through 19. Figure 14 shows a straightforward application to the Intel 8048/80/85 microprocessors via an 8255PPI, where the ICL7109 data outputs are active at all times. The I/O ports of an 8155 may be used in the same way. This interface can be used in a read-anytime mode, although a read performed while the data latches are being updated will lead to scrambled data. This will occur very rarely, in the proportion of set-up skew times to conversion time. One way to overcome this is to read the STATUS output as well, and if it is high, read the data again after a delay of more than 1/2 converter clock period. If STATUS is now low, the second reading is correct, and if it is still high, the first reading is correct. Alternatively, this timing problem is completely avoided by using a readafter-update sequence, as shown in Figure 15. Here the high to low transition of the STATUS output drives an interrupt to the microprocessor causing it to access the data latches. This application also shows the RUN/HOLD input being used to initiate conversions under software control. A similar interface to Motorola MC6800 or Rockwell R650X systems is shown in Figure 16. The high to low transition of the STATUS output generates an interrupt via the Control Register B CB1 line. Note that CB2 controls the RUN/HOLD pin through Control Register B, allowing software-controlled initiation of conversions in this system as well. The three-state output capability of the ICL7109 allows direct interfacing to most microprocessor busses. Examples of this are shown in Figures 17 and 18. It is necessary to carefully consider the system in this type of interface, to be sure that requirements for setup and hold times, and minimum pulse widths are met. Note also the drive limitations on long buses. Generally this type of interface is only favored if the memory peripheral address density is low so that simple address decoding can be used. Interrupt handling can also require many additional components, and using an interface device will usually simplify the system in this case. 5-21 ICL7109 Handshake Mode Interfacing The handshake mode allows ready interface with a wide variety of external devices. For instance, external latches may be clocked by the rising edge of CE/LOAD, and the byte enables may be used as byte identification flags or as load enables. Figure 19 shows a handshake interface to Intel microprocessors again using an 8255PPI. The handshake operation with the 8255 is controlled by inverting its Input Buffer Full (IBF) flag to drive the SEND input to the ICL7109, and using the CE/LOAD to drive the 8255 strobe. The internal control register of the PPI should be sent in MODE 1 for the port used. If the ICL7109 is in handshake mode and the 8255 IBF flag is low, the next word will be strobed into the port. The strobe will cause IBF to go high (SEND goes low), which will keep the enable byte outputs active. The PPI will generate an interrupt which when executed will result in the data being read. When the byte is read, the IBF will be reset low, which causes the ICL7109 to sequence into the next byte. This figure shows the MODE input to the ICL7109 connected to a control line on the PPI. If this output is left high, or tied high separately, the data from every conversion (provided the data access takes less time than a conversion) will be sequenced in two bytes into the system. If this output is made to go from low to high, the output sequence can be obtained on demand, and the interrupt may be used to reset the MODE bit. Note that the RUN/HOLD input to the ICL7109 may also be obtained on command under software control. Note that one port of the 8255 is not used, and can service another peripheral device. the same arrangement can also be used with the 8155. Figure 20 shows a similar arrangement with the MC6800 or MCS650X microprocessors, except that both MODE and RUN/HOLD are tied high to save port outputs. The handshake mode is particularly convenient for directly interfacing to industry standard UARTs (such as the Intersil IM6402 or Western Digital TR1602) providing a minimum component count means of serially transmitting converted data. A typical UART connection is shown in Figure 1A. In this circuit, any word received by the UART causes the UART DR (Data Ready) output to go high. This drives the MODE input to the ICL7109 high, triggering the ICL7109 into handshake mode. The high order byte is output to the UART first, and when the UART has transferred the data to the Transmitter Register, TBRE (SEND) goes high again, LBEN will go high, driving the UART DRR (Data Ready Reset) which will signal the end of the transfer of data from the ICL7109 to the UART. Figure 21 shows an extension of the one converter one UART scheme to several ICL7109s with one UART. In this circuit, the word received by the UART (available at the RBR outputs when DR is high) is used to select which converter will handshake with the UART. With no external components, this scheme will allow up to eight ICL7109s to interface with one UART. Using a few more components to decode the received word will allow up to 256 converters to be accessed on one serial line. GND MODE B9 - B12 POL, OR ICL7109 B1 - B8 8 PB0 - 7 MC6820 ANALOG IN STATUS RUN/HOLD CE/ LOAD HBEN LBEN GND CB1 CB2 6 PA0 - 5 CRB - -11R-01 MC680X OR MCS650X ADDRESS BUS DATA BUS CONTROL BUS FIGURE 16. FULL-TIME PARALLEL INTERFACE TO MC680X OR MCS650X MICROPROCESSORS 5-22 ICL7109 The applications of the ICL7109 are not limited to those shown here. The purposes of these examples are to provide a starting point for users to develop useful systems and to show some of the variety of interfaces and uses of the combination. In particular the uses of the STATUS, RUN/HOLD, and MODE signals may be mixed. The following application notes contain very useful information on understanding and applying this part and are available from Intersil Corporation. Application Notes NOTE # AN016 AN017 AN018 AN030 AN032 DESCRIPTION "Selecting A/D Converters" "The Integrating A/D Converter" "Do's and Don'ts of Applying A/D Converters" "The ICL7104 - A Binary Output A/D Converter for Microprocessors" "Understanding the Auto-Zero and Common Mode Performance of the ICL7136/7/9 Family" AnswerFAX DOC. # 9016 9017 9018 9030 9032 ADDRESS BUS A14 A15 CONTROL BUS RD DATA BUS HBEN LBEN B9 - B12 POL, OR 6 8008, 8080, 8085 8 ICL7109 B1 - B8 ANALOG IN CE/LOAD MODE RUN/HOLD MEMR OR IOR FOR 8080/8228 SYSTEM GND +5V FIGURE 17. DIRECT INTERFACE - ICL7109 TO 8080/8085 GND MODE RUN/HOLD B9 - B12 POL, OR B1 - B8 ANALOG IN HBEN LBEN CE/LOAD +5V 6 8 MC680X OR MCS650X 74C42 A0 - A2 A15 - A10 74C30 R/W, VMA ADDRESS DATA CONTROL BUS BUS BUS FIGURE 18. DIRECT ICL7109 - MC680X BUS INTERFACE 5-23 ICL7109 ADDRESS BUS CONTROL BUS DATA BUS RD B9 - B12 POL, OR ICL7109 B1 - B8 8 STBA IBFA 6 WR D7 - D0 A0 - A1 CS PA7 - PA0 8008, 8080, 8085, 8048, ETC. 8255 (MODE 1) PC4 PC5 PC6 PC7 PC3 INTR CE/LOAD ANALOG IN SEND RUN/HOLD MODE FIGURE 19. HANDSHAKE INTERFACE - ICL7109 TO 8048, 80/85 +5V MODE RUN/HOLD CRA - -100 - 01 MC6820 ICL7109 PA0 - PA7 MC6800 OR MCS650X ANALOG IN CE/LOAD SEND CA1 CA2 LBEN HBEN ADDRESS BUS DATA BUS CONTROL BUS FIGURE 20. HANDSHAKE INTERFACE - ICL7109 TO MC6800, MCS650X 5-24 ICL7109 SERIAL OUTPUT IM6402 CMOS UART TBRL DRR TBRE RBR1 - RBR8 2 3 SERIAL INPUT TBR1 - TBR8 8-BIT DATA BUS MODE CE/ SEND LOAD B9 - B12 POL, OR MODE 6 CE/ SEND LOAD B9 - B12 POL, OR MODE 6 CE/ SEND LOAD B9 - B12 POL, OR 6 SEND ANALOG IN 8 ANALOG IN SEND 8 ANALOG IN SEND 8 RUN/HOLD HBEN LBEN +5V RUN/HOLD HBEN LBEN +5V RUN/HOLD HBEN LBEN +5V FIGURE 21. MULTIPLEXING CONVERTERS WITH MODE INPUT 5-25 ICL7109 Die Characteristics DIE DIMENSIONS: (122 mils x 135 mils) x 525m 25m Thick METALLIZATION: Type: Al Thickness: 10kA 1kA PASSIVATION: Type: Nitride/Silox Sandwich Thickness: 8kA Nitride over 7kA Silox Metallization Mask Layout ICL7109 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11 B12 TEST LBEN OR POL HBEN CE/LOAD STATUS GND V+ MODE OSC IN OSC OUT REF INOSC SEL BUF OSC OUT REF CAP- REF CAP+ REF IN+ RUN/HOLD SEND V- REF OUT BUF AZ INT COMMON IN LO IN HI All Intersil semiconductor products are manufactured, assembled and tested under ISO9000 quality systems certification. Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries. For information regarding Intersil Corporation and its products, see web site http://www.intersil.com 5-26 |
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