Philips Semiconductors Linear Products Product specification CMOS 8-bit A/D converters ADC0803/4-1 DESCRIPTION PIN CONFIGURATION The ADC0803 family is a series of three CMOS 8-bit successive approximation A/D converters using a resistive ladder and capacitive array together with an auto-zero comparator. These converters are designed to operate with microprocessor-controlled buses using a minimum of external circuitry. The 3-State output data lines can be connected directly to the data bus. D1, N PACKAGES The differential analog voltage input allows for increased common-mode rejection and provides a means to adjust the zero-scale offset. Additionally, the voltage reference input provides a means of encoding small analog voltages to the full 8 bits of resolution. CS 1 20 VCC RD 2 19 CLK R WR 3 18 D0 4 17 D1 INTR 5 16 D2 VIN(+) 6 15 D3 VIN(-) 7 14 D4 8 13 D5 VREF/2 9 12 D6 D GND 10 11 D7 CLK IN A GND FEATURES * Compatible with most microprocessors * Differential inputs * 3-State outputs * Logic levels TTL and MOS compatible * Can be used with internal or external clock * Analog input range 0V to VCC * Single 5V supply * Guaranteed specification with 1MHz clock TOP VIEW NOTE: SOL -- Released in large SO package only. APPLICATIONS * Transducer-to-microprocessor interface * Digital thermometer * Digitally-controlled thermostat * Microprocessor-based monitoring and control systems ORDERING INFORMATION TEMPERATURE RANGE ORDER CODE DWG # 20-Pin Plastic Dual In-Line Package (DIP) DESCRIPTION -40 to +85C ADC0803/04-1 LCN 0408B 20-Pin Plastic Dual In-Line Package (DIP) 0 to 70C ADC0803/04-1 CN 0408B 20-Pin Plastic Small Outline (SO) Package 0 to 70C ADC0803/04-1 CD 1021B 20-Pin Plastic Small Outline (SO) Package -40 to 85C ADC0803/04-1 LCD 1021B RATING UNIT 6.5 V Logic control input voltages -0.3 to +16 V All other input voltages -0.3 to (VCC +0.3) V ADC0803/04-1 LCD -40 to +85 C ADC0803/04-1 LCN -40 to +85 C ADC0803/04-1 CD 0 to +70 C ABSOLUTE MAXIMUM RATINGS SYMBOL VCC TA PARAMETER Supply voltage Operating temperature range 0 to +70 C -65 to +150 C 300 C N package 1690 mW D package 1390 mW ADC0803/04-1 CN TSTG Storage temperature TSOLD Lead soldering temperature (10 seconds) PD Maximum power dissipation TA=25C (still air)1 NOTES: 1. Derate above 25C, at the following rates: N package at 13.5mW/C; D package at 11.1mW/C August 31, 1994 555 853-0034 13721 Philips Semiconductors Linear Products Product specification CMOS 8-bit A/D converters ADC0803/4-1 BLOCK DIAGRAM VIN (-) 7 + M VIN (+) 6 - + 9 VREF/2 8 AUTO ZERO COMPARATOR LADDER AND DECODER A GND VCC - 20 D7 (MSB) (11) OUTPUT LATCHES SAR 10 D GND LE 3 WR 8-BIT SHIFT REGISTER CLOCK 1 CS S INTR FF R Q 2 RD 5 INTR August 31, 1994 556 4 CLK IN 19 CLK R OE D6 D5 D4 (12) (13) (14) D3 D2 D1 D0 (LSB) (15) (16) (17) (18) Philips Semiconductors Linear Products Product specification CMOS 8-bit A/D converters ADC0803/4-1 DC ELECTRICAL CHARACTERISTICS VCC = 5.0V, fCLK = 1MHz, TMIN TA TMAX, unless otherwise specified. SYMBOL RIN PARAMETER TEST CONDITIONS ADC0803/4 Min Typ Max UNIT ADC0803 relative accuracy error (adjusted) Full-Scale adjusted 0.50 LSB ADC0804 relative accuracy error (unadjusted) VREF/2 = 2.500VDC 1 LSB VREF/2 input resistance3 VCC = 0V2 Analog input voltage range3 400 680 -0.05 DC common-mode error Over analog input voltage range 1/16 Power supply sensitivity VCC = 5V 10%1 1/16 VCC+0.05 V 1/8 LSB LSB Control inputs VIH Logical "1" input voltage VCC = 5.25VDC VIL Logical "0" input voltage VCC = 4.75VDC IIH Logical "1" input current VIN = 5VDC IIL Logical "0" input current VIN = 0VDC 2.0 15 0.005 -1 -0.005 VDC 0.8 VDC 1 ADC ADC Clock in and clock R VT+ Clock in positive-going threshold voltage 2.7 3.1 3.5 VDC VT- Clock in negative-going threshold voltage 1.5 1.8 2.1 VDC VH Clock in hysteresis (VT+)-(VT-) 0.6 1.3 2.0 VDC VOL Logical "0" clock R output voltage IOL = 360A, VCC = 4.75VDC 0.4 VDC VOH Logical "1" clock R output voltage IOH = -360A, VCC = 4.75VDC 2.4 VDC Data output and INTR VOL Logical "0" output voltage Data outputs IOL = 1.6mA, VCC = 4.75VDC 0.4 VDC INTR outputs IOL = 1.0mA, VCC = 4.75VDC 0.4 VDC IOH = -360A, VCC = 4.75VDC 2.4 IOH = -10A, VCC = 4.75VDC 4.5 3-state output leakage VOUT = 0VDC, CS = logical "1" -3 IOZH 3-state output leakage VOUT = 5VDC, CS = logical "1" ISC +Output short-circuit current ISC -Output short-circuit current VOH Logical "1" output voltage IOZL ICC Power supply current ADC 3 ADC VOUT = 0V, TA = 25C 4.5 12 mADC VOUT = VCC, TA = 25C 9.0 30 mADC fCLK = 1MHz, VREF/2 = OPEN, CS = Logical "1", TA = 25C NOTES: 1. Analog inputs must remain within the range: -0.05 VIN VCC + 0.05V. 2. See typical performance characteristics for input resistance at VCC = 5V. 3. VREF/2 and VIN must be applied after the VCC has been turned on to prevent the possibility of latching. August 31, 1994 VDC 557 3.0 3.5 mA Philips Semiconductors Linear Products Product specification CMOS 8-bit A/D converters ADC0803/4-1 AC ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER TO FROM fCLK=1MHz1 Conversion time fCLK TEST CONDITIONS ADC0803/4 Min 66 frequency1 0.1 Clock duty cycle1 40 Clock CR Free-running conversion rate tW(WR)L Start pulse width tACC Access time Typ 1.0 CS=0, fCLK=1MHz INTR tied to WR CS=0 Output Max UNIT 73 s 3.0 MHz 60 % 13690 conv/s 30 ns RD CS=0, CL=100pF 75 100 ns Output RD CL=10pF, RL=10k See 3-State test circuit 70 100 ns INTR WD or RD 100 150 ns t1H, t0H 3-State control tW1, tR1 INTR delay CIN Logic input=capacitance 5 7.5 pF COUT 3-State output capacitance 5 7.5 pF NOTES: 1. Accuracy is guaranteed at fCLK=1MHz. Accuracy may degrade at higher clock frequencies. FUNCTIONAL DESCRIPTION ANALOG OPERATION These devices operate on the Successive Approximation principle. Analog switches are closed sequentially by successive approximation logic until the input to the auto-zero comparator [ VIN(+)-VIN(-) ] matches the voltage from the decoder. After all bits are tested and determined, the 8-bit binary code corresponding to the input voltage is transferred to an output latch. Conversion begins with the arrival of a pulse at the WR input if the CS input is low. On the High-to-Low transition of the signal at the WR or the CS input, the SAR is initialized, the shift register is reset, and the INTR output is set high. The A/D will remain in the reset state as long as the CS and WR inputs remain low. Conversion will start from one to eight clock periods after one or both of these inputs makes a Low-to-High transition. After the conversion is complete, the INTR pin will make a High-to-Low transition. This can be used to interrupt a processor, or otherwise signal the availability of a new conversion result. A read (RD) operation (with CS low) will clear the INTR line and enable the output latches. The device may be run in the free-running mode as described later. A conversion in progress can be interrupted by issuing another start command. Analog Input Current The analog comparisons are performed by a capacitive charge summing circuit. The input capacitor is switched between VIN(+)4 and VIN(-), while reference capacitors are switched between taps on the reference voltage divider string. The net charge corresponds to the weighted difference between the input and the most recent total value set by the successive approximation register. The internal switching action causes displacement currents to flow at the analog inputs. The voltage on the on-chip capacitance is switched through the analog differential input voltage, resulting in proportional currents entering the VIN(+) input and leaving the VIN(-) input. These transient currents occur at the leading edge of the internal clock pulses. They decay rapidly so do not inherently cause errors as the on-chip comparator is strobed at the end of the clock period. Input Bypass Capacitors and Source Resistance Bypass capacitors at the input will average the charges mentioned above, causing a DC and an AC current to flow through the output resistance of the analog signal sources. This charge pumping action is worse for continuous conversions with the VIN(+) input at full scale. This current can be a few microamps, so bypass capacitors should NOT be used at the analog inputs of the VREF/2 input for high resistance sources (> 1k). If input bypass capacitors are desired for noise filtering and a high source resistance is desired to minimize capacitor size, detrimental effects of the voltage drop across the input resistance can be eliminated by adjusting the full scale with both the input resistance and the input bypass capacitor in place. This is possible because the magnitude of the input current is a precise linear function of the differential voltage. Digital Control Inputs The digital control inputs (CS, WR, RD) are compatible with standard TTL logic voltage levels. The required signals at these inputs correspond to Chip Select, START Conversion, and Output Enable control signals, respectively. They are active-Low for easy interface to microprocessor and microcontroller control buses. For applications not using microprocessors, the CS input (Pin 1) can be grounded and the A/D START function is achieved by a negative-going pulse to the WR input (Pin 3). The Output Enable function is achieved by a logic low signal at the RD input (Pin 2), which may be grounded to constantly have the latest conversion present at the output. August 31, 1994 558 Philips Semiconductors Linear Products Product specification CMOS 8-bit A/D converters ADC0803/4-1 Large values of source resistance where an input bypass capacitor is not used will not cause errors as the input currents settle out prior to the comparison time. If a low pass filter is required in the system, use a low valued series resistor (< 1k) for a passive RC section or add an op amp active filter (low pass). For applications with source resistances at or below 1k, a 0.1F bypass capacitor at the inputs will prevent pickup due to series lead inductance or a long wire. A 100 series resistor can be used to isolate this capacitor (both the resistor and capacitor should be placed out of the feedback loop) from the output of the op amp, if used. Reference Voltage Span Adjust Note that the Pin 9 (VREF/2) voltage is either 1/2 the voltage applied to the VCC supply pin, or is equal to the voltage which is externally forced at the VREF/2 pin. In addition to allowing for flexible references and full span voltages, this also allows for a ratiometric voltage reference. The internal gain of the VREF/2 input is 2, making the full-scale differential input voltage twice the voltage at Pin 9. For example, a dynamic voltage range of the analog input voltage that extends from 0 to 4V gives a span of 4V (4-0), so the VREF/2 voltage can be made equal to 2V (half of the 4V span) and full scale output would correspond to 4V at the input. Analog Differential Voltage Inputs and CommonMode Rejection On the other hand, if the dynamic input voltage had a range of 0.5 to 3.5V, the span or dynamic input range is 3V (3.5-0.5). To encode this 3V span with 0.5V yielding a code of zero, the minimum expected input (0.5V, in this case) is applied to the VIN(-) pin to account for the offset, and the VREF/2 pin is set to 1/2 the 3V span, or 1.5V. The A/D converter will now encode the VIN(+) signal between 0.5 and 3.5V with 0.5V at the input corresponding to a code of zero and 3.5V at the input producing a full scale output code. The full 8 bits of resolution are thus applied over this reduced input voltage range. The required connections are shown in Figure 2. These A/D converters have additional flexibility due to the analog differential voltage input. The VIN(-) input (Pin 7) can be used to subtract a fixed voltage from the input reading (tare correction). This is also useful in a 4/20mA current loop conversion. Common-mode noise can also be reduced by the use of the differential input. The time interval between sampling VIN(+) and VIN(-) is 4.5 clock periods. The maximum error due to this time difference is given by: V(max)=(VP) (2fCM) (4.5/fCLK), where: Operating Mode These converters can be operated in two modes: V=error voltage due to sampling delay VP=peak value of common-mode voltage 1) absolute mode 2) ratiometric mode fCM=common mode frequency In absolute mode applications, both the initial accuracy and the temperature stability of the reference voltage are important factors in the accuracy of the conversion. For VREF/2 voltages of 2.5V, initial errors of 10mV will cause conversion errors of 1 LSB due to the gain of 2 at the VREF/2 input. In reduced span applications, the initial value and stability of the VREF/2 input voltage become even more important as the same error is a larger percentage of the VREF/2 nominal value. See Figure 3. For example, with a 60Hz common-mode frequency, fcm, and a 1MHz A/D clock, FCLK, keeping this error to 1/4 LSB (about 5mV) would allow a common-mode voltage, VP, which is given by: VP [V(max) (f CLK) (2f CM)(4.5) or VP (5 x 10 3) (10 4) 2.95V (6.28) (60) (4.5) In ratiometric converter applications, the magnitude of the reference voltage is a factor in both the output of the source transducer and the output of the A/D converter, and, therefore, cancels out in the final digital code. See Figure 4. The allowed range of analog input voltages usually places more severe restrictions on input common-mode voltage levels than this, however. Generally, the reference voltage will require an initial adjustment. Errors due to an improper reference voltage value appear as full-scale errors in the A/D transfer function. An analog input span less than the full 5V capability of the device, together with a relatively large zero offset, can be easily handled by use of the differential input. (See Reference Voltage Span Adjust). ERRORS AND INPUT SPAN ADJUSTMENTS There are many sources of error in any data converter, some of which can be adjusted out. Inherent errors, such as relative accuracy, cannot be eliminated, but such errors as full-scale and zero scale offset errors can be eliminated quite easily. See Figure 2. Noise and Stray Pickup The leads of the analog inputs (Pins 6 and 7) should be kept as short as possible to minimize input noise coupling and stray signal pick-up. Both EMI and undesired digital signal coupling to these inputs can cause system errors. The source resistance for these inputs should generally be below 5k to help avoid undesired noise pickup. Input bypass capacitors at the analog inputs can create errors as described previously. Full scale adjustment with any input bypass capacitors in place will eliminate these errors. Zero Scale Error Zero scale error of an A/D is the difference of potential between the ideal 1/2 LSB value (9.8mV for VREF/2=2.500V) and that input voltage which just causes an output transition from code 0000 0000 to a code of 0000 0001. Reference Voltage If the minimum input value is not ground potential, a zero offset can be made. The converter can be made to output a digital code of 0000 0000 for the minimum expected input voltage by biasing the VIN(-) input to that minimum value expected at the VIN(-) input to that minimum value expected at the VIN(+) input. This uses the For application flexibility, these A/D converters have been designed to accommodate fixed reference voltages of 5V to Pin 20 or 2.5V to Pin 9, or an adjusted reference voltage at Pin 9. The reference can be set by forcing it at VREF/2 input, or can be determined by the supply voltage (Pin 20). Figure 1 indicates how this is accomplished. August 31, 1994 559 Philips Semiconductors Linear Products Product specification CMOS 8-bit A/D converters ADC0803/4-1 At higher CPU clock frequencies, time can be extended for I/O reads (and/or writes) by inserting wait states (8880) or using clock-extending circuits (6800, 8035). differential mode of the converter. Any offset adjustment should be done prior to full scale adjustment. Full Scale Adjustment Finally, if time is critical and capacitive loading is high, external bus drivers must be used. These can be 3-State buffers (low power Schottky is recommended, such as the N74LS240 series) or special higher current drive products designed as bus drivers. High current bipolar bus drivers with PNP inputs are recommended as the PNP input offers low loading of the A/D output, allowing better response time. Full scale gain is adjusted by applying any desired offset voltage to VIN(-), then applying the VIN(+) a voltage that is 1-1/2 LSB less than the desired analog full-scale voltage range and then adjusting the magnitude of VREF/2 input voltage (or the VCC supply if there is no VREF/2 input connection) for a digital output code which just changes from 1111 1110 to 1111 1111. The ideal VIN(+) voltage for this full-scale adjustment is given by: V IN() ) + V IN(*) * 1.5 x V MAX * V MIN 255 POWER SUPPLIES Noise spikes on the VCC line can cause conversion errors as the internal comparator will respond to them. A low inductance filter capacitor should be used close to the converter VCC pin and values of 1F or greater are recommended. A separate 5V regulator for the converter (and other 5V linear circuitry) will greatly reduce digital noise on the VCC supply and the attendant problems. where: VMAX=high end of analog input range (ground referenced) VMIN=low end (zero offset) of analog input (ground referenced) WIRING AND LAYOUT PRECAUTIONS CLOCKING OPTION Digital wire-wrap sockets and connections are not satisfactory for breadboarding this (or any) A/D converter. Sockets on PC boards can be used. All logic signal wires and leads should be grouped or kept as far as possible from the analog signal leads. Single wire analog input leads may pick up undesired hum and noise, requiring the use of shielded leads to the analog inputs in many applications. The clock signal for these A/Ds can be derived from external sources, such as a system clock, or self-clocking can be accomplished by adding an external resistor and capacitor, as shown in Figure 6. Heavy capacitive or DC loading of the CLK R pin should be avoided as this will disturb normal converter operation. Loads less than 50pF are allowed. This permits driving up to seven A/D converter CLK IN pins of this family from a single CLK R pin of one converter. For larger loading of the clock line, a CMOS or low power TTL buffer or PNP input logic should be used to minimize the loading on the CLK R pin. A single-point analog ground separate from the logic or digital ground points should be used. The power supply bypass capacitor and the self-clocking capacitor, if used, should be returned to digital ground. Any VREF/2 bypass capacitor, analog input filter capacitors, and any input shielding should be returned to the analog ground point. Proper grounding will minimize zero-scale errors which are present in every code. Zero-scale errors can usually be traced to improper board layout and wiring. Restart During a Conversion A conversion in process can be halted and a new conversion began by bringing the CS and WR inputs low and allowing at least one of them to go high again. The output data latch is not updated if the conversion in progress is not completed; the data from the previously completed conversion will remain in the output data latches until a subsequent conversion is completed. APPLICATIONS Microprocessor Interfacing This family of A/D converters was designed for easy microprocessor interfacing. These converters can be memory mapped with appropriate memory address decoding for CS (read) input. The active-Low write pulse from the processor is then connected to the WR input of the A/D converter, while the processor active-Low read pulse is fed to the converter RD input to read the converted data. If the clock signal is derived from the microprocessor system clock, the designer/programmer should be sure that there is no attempt to read the converter until 74 converter clock pulses after the start pulse goes high. Alternatively, the INTR pin may be used to interrupt the processor to cause reading of the converted data. Of course, the converter can be connected and addressed as a peripheral (in I/O space), as shown in Figure 7. A bus driver should be used as a buffer to the A/D output in large microprocessor systems where the data leaves the PC board and/or must drive capacitive loads in excess of 100pF. See Figure 9. Continuous Conversion To provide continuous conversion of input data, the CS and RD inputs are grounded and INTR output is tied to the WR input. This INTR/WR connection should be momentarily forced to a logic low upon power-up to insure circuit operation. See Figure 5 for one way to accomplish this. DRIVING THE DATA BUS This CMOS A/D converter, like MOS microprocessors and memories, will require a bus driver when the total capacitance of the data bus gets large. Other circuitry tied to the data bus will add to the total capacitive loading, even in the high impedance mode. There are alternatives in handling this problem. The capacitive loading of the data bus slows down the response time, although DC specifications are still met. For systems with a relatively low CPU clock frequency, more time is available in which to establish proper logic levels on the bus, allowing higher capacitive loads to be driven (see Typical Performance Characteristics). August 31, 1994 Interfacing the SCN8048 microcomputer family is pretty simple, as shown in Figure 8. Since the SCN8048 family has 24 I/O lines, one of these (shown here as bit 0 or port 1) can be used as the chip select signal to the converter, eliminating the need for an address 560 Philips Semiconductors Linear Products Product specification CMOS 8-bit A/D converters ADC0803/4-1 decoder. The RD and WR signals are generated by reading from and writing to a dummy address. A Digital Thermostat Circuit Description The schematic of a Digital Thermostat is shown in Figure 11. The A/D digitizes the output of the LM35, a temperature transducer IC with an output of 10mV per C. With VREF/2 set for 2.56V, this 10mV corresponds to 1/2 LSB and the circuit resolution is 2C. Reducing VREF/2 to 1.28 yields a resolution of 1C. Of course, the lower VREF/2 is, the more sensitive the A/D will be to noise. Digitizing a Transducer Interface Output Circuit Description Figure 10 shows an example of digitizing transducer interface output voltage. In this case, the transducer interface is the NE5521, an LVDT (Linear Variable Differential Transformer) Signal Conditioner. The diode at the A/D input is used to insure that the input to the A/D does not go excessively beyond the supply voltage of the A/D. See the NE5521 data sheet for a complete description of the operation of that part. The desired temperature is set by holding either of the set buttons closed. The SCC80C451 programming could cause the desired (set) temperature to be displayed while either button is depressed and for a short time after it is released. At other times the ambient temperature could be displayed. Circuit Adjustment To adjust the full scale and zero scale of the A/D, determine the range of voltages that the transducer interface output will take on. Set the LVDT core for null and set the Zero Scale Scale Adjust Potentiometer for a digital output from the A/D of 1000 000. Set the LVDT core for maximum voltage from the interface and set the Full Scale Adjust potentiometer so the A/D output is just barely 1111 1111. The set temperature is stored in an SCN8051 internal register. The A/D conversion is started by writing anything at all to the A/D with port pin P10 set high. The desired temperature is compared with the digitized actual temperature, and the heater is turned on or off by clearing setting port pin P12. If desired, another port pin could be used to turn on or off an air conditioner. The display drivers are NE587s if common anode LED displays are used. Of course, it is possible to interface to LCD displays as well. August 31, 1994 561 Philips Semiconductors Linear Products Product specification CMOS 8-bit A/D converters ADC0803/4-1 TYPICAL PERFORMANCE CHARACTERISTICS Power Supply Current vs Temperature Clock Frequency vs Clock Capacitor 2.6 5.5V 2.4 5.0V 2.2 4.0 3 VCC = 5.0V TA = 25oC 4 2 2.0 MAX. (mA) 2.8 5 1.0 0.8 0.6 1 REF/2 fCLK = 1MHz CS = H 10.0 8.0 6.0 0 -1 f 3.0 CLOCK FRQ (MHz) POWER SUPPLY CURRENT (mA) 3.2 Input Current vs Applied Voltage at VREF/2 Pin -2 0.4 TYP. -3 0.2 4.5V 2.0 -4 MIN. -5 0.1 1.8 -50 -25 0 25 50 75 10 100 125 20 40 60 80100 AMBIENT TEMPERATURE (Co) 200 400 600 1000 0 Logic Input Threshold Voltage vs Supply Voltage +125oC 1.50 1.40 1.30 4.50 4.75 5.00 5.25 VCC = 5.0V -55oC < TA 125oC 4.0 3.5 VT+ 3.0 2.5 VT 2.0 VCC SUPPLY VOLTAGE (V) 4.75 5.00 5.25 14 12 VO = 2.5V 10 VO = 0.4V 6 -50 5.50 -25 0 25 50 VCC SUPPLY VOLTAGE (V) Delay From RD Falling Edge to Data Valid vs Load Capacitance 4 350 VCC = 5.0V VREF/2 = VCC = 5.0V TA = 25oC 300 2.5V 250 DEALY (ns) 3 2 200 150 100 1 50 0 0 0 20 40 60 80 100 0 120 CONVERSION TIME (s) August 31, 1994 200 400 600 800 LOAD CAPACITANCE (pF) 562 75 100 AMBIENT TEMPERATURE (oC) Full Scale Error vs Conversion Time ERROR (LSB) 16 8 1.5 1.0 4.50 5.50 5 4 18 OUTPUT CURRENT (mA) CLK-IN THRESHOLD VOLTAGE (V) LOGIC INPUT (V) +25oC 3 Output Current vs Temperature CLK-IN Threshold Voltage vs Supply Voltage -55oC 1.60 2 APPLIED VREF/2 (V) 4.5 1.70 1 CLOCK CAP (pF) 1000 125 Philips Semiconductors Linear Products Product specification CMOS 8-bit A/D converters ADC0803/4-1 3-STATE TEST CIRCUITS AND WAVEFORMS (ADC0801-1) 20ns VCC VCC RD RD DATA OUTPUT CS CL 10pF GND VCC tr VOH DATA OUTPUT RD 10K t1H 10K VCC VCC 90% 50% 10% RD 90% GND DATA OUTPUT CS CL GND t1H 10pF tr 90% 50% 10% t0H VOH DATA OUTPUT 10% GND tOH TIMING DIAGRAMS (All timing is measured from the 50% voltage points) START CONVERSION CS WR tWI tW(WR)L "BUSY" ACTUAL INTERNAL STATUS OF THE CONVERTER DATA IS VALID IN OUTPUT LATCHES "NOT BUSY" (LAST DATA WAS READ) INTERNAL TC 1 TO 8 X 1/fCLK INTR (LAST DATA WAS NOT READ) INT ASSERTED 1/2 TCLK INTR INTR RESET CS tRI RD NOTE DATA OUTPUTS THREE-STATE tACC t1H, t0H Output Enable and Reset INTR NOTE: Read strobe must occur 8 clock periods (8/fCLK) after assertion of interrupt to guarantee reset of INTR. August 31, 1994 563 Philips Semiconductors Linear Products Product specification CMOS 8-bit A/D converters ADC0803/4-1 VCC (5V) VREF VREF 20 R VREF/2 9 - FS OFFSET ADJUST 330 TO VREF/2 + 0.1F DIGITAL CIRCUITS ZS OFFSET ADJUST ANALOG CIRCUITS R TO VIN(-) Figure 2. Offsetting the Zero Scale and Adjusting the Input Range (Span) 8 10 NOTE: The VREF/2 voltage is either 1/2 the VCC voltage or is that which is forced at Pin 9. Figure 1. Internal Reference Design +5V +5V VCC + VIN(+) VCC + VIN(+) 10F 2k A/D 10F 2k A/D VREF/2 VREF/2 VIN(-) VOLTAGE REFERENCE VREF/2 a. Fixed Reference 2k b. Fixed Reference Derived from VCC VCC VIN(+) VCC + 10F 2k A/D VIN(-) VREF/2 FULL SCALE 100 OPTIONAL 2k Figure 4. Ratiometric Mode of Operation with Optional Full Scale Adjustment August 31, 1994 100 VIN(-) Figure 3. Absolute Mode of Operation TRANSDUCER +5V 564 2k c. Optional Full Scale Adjustment Philips Semiconductors Linear Products Product specification CMOS 8-bit A/D converters ADC0803/4-1 +5V 10k +5V 10K 2.7k 47F TO 100F 10k 56pF CS 1 20 VCC RD 2 19 CLK R WR 3 18 D0 CLK IN 4 17 D1 INTR 5 16 D2 VIN(+) 6 VIN(-) 7 14 D4 A GND 8 13 D5 VREF/2 9 12 D6 D GND 10 11 D7 DB0 DB1 DB2 A/D 15 D3 DB3 DB4 DB5 DB6 DB7 Figure 5. Connection for Continuous Conversion +5V CLK R 19 R VCC CLK IN 4 fCLK = 1/1.7 R C R = 10K C A/D Figure 6. Self-Clocking the Converter SCN8051 OR SCN80C51 INT I/O WR D0 18 2 P1.1 D1 17 3 P1.2 D2 16 4 P1.3 D3 15 5 P1.4 D4 14 6 P1.5 D5 13 7 P1.6 D6 12 8 P1.7 D7 11 6 VIN(+) RD 2 7 VREF/2 12 INTO 39 P0.0 CS 1 ANALOG INPUTS 56pF 10k 4 CLK IN 56pF A/D ANALOG INPUTS WR 3 INTR 5 12 A GND CS 1 11 D GND 20 VCC RD 2 19 CLK R WR 3 18 D0 CLK IN 4 17 D1 INTR 5 16 D2 VIN(+) 6 19 CLK R P1.0 16 WR +5V 20 1 17 RD I/O RD 10k VCC 40 CLK DB0 Figure 8. SCN8051 Interfacing DB1 DB2 A/D 18 D0 15 D3 VIN(-) 7 14 D4 A GND 8 13 D5 VREF/2 9 12 D6 D GND 10 11 D7 DB3 17 D1 DB4 16 D2 DB5 15 D3 DB6 14 D4 DB7 A/D 13 D5 12 D6 ADDRESS 8-BIT BUFFER DATA BUS N74LS241 N74LS244 N74LS541 11 D7 DECODE LOGIC Figure 7. Interfacing to 8080A Microprocessor OE Figure 9. Buffering the A/D Output to Drive High Capacitance Loads and for Driving Off-Board Loads August 31, 1994 565 Philips Semiconductors Linear Products Product specification CMOS 8-bit A/D converters ADC0803/4-1 +5V Ct 18k 4.7k 1.5k 820 LVDT NE5521 1F 4.7k 0.47F 22k +5V 470 IN4148 VCC VIN(+) 3.3k 2k A/D 2k VIN(-) VREF/2 FULL 100 SCALE ADJUST 2k Figure 10. Digitizing a Transducer Interface Output August 31, 1994 566 Philips Semiconductors Linear Products Product specification CMOS 8-bit A/D converters ADC0803/4-1 RBI 5 6 2 1 1/4 HEF4071 NE587 7 7 8 3 RBO 6 4 10K RBI 5 2 1 1/4 HEF4071 NE587 7 7 8 3 10K LOWER P15 13 14 RAISE P16 SCC80C51 18 DB0 D0 18 17 DB1 D1 17 16 DB2 D2 16 15 DB3 D3 15 14 DB4 D4 14 13 DB5 D5 13 12 DB6 D6 12 11 DB7 D7 11 8 RD RD 2 10 WR WR 3 6 INT INTR 5 +5V 20 VCC + 10F 19 CLK R 10K A/D 4 CLK IN 56pF 27 CS P10 1 D GND 29 P12 20 GND +V 2N3906 1N4148 TO HEATER Figure 11. Digital Thermostat August 31, 1994 567 6 VIN(+) 7 VIN(-) 10 8 A GND LM35