ADC0844CCJ

ADC0844/ADC0848 8-Bit µP Compatible A/D Converters with Multiplexer Options June 1999 ADC0844/ADC0848 8-Bit µP Compatible A/D Converters with Multiplexer Options General Description The ADC0844 and ADC0848 are CMOS 8-bit successive approximation A/D converters with versatile analog input multiplexers. The 4-channel or 8-channel multiplexers can be software configured for single-ended, differential or pseudo-differential modes of operation. The differential mode provides low frequency input common mode rejection and allows offsetting the analog range of the converter. In addition, the A/D’s reference can be adjusted enabling the conversion of reduced analog ranges with 8-bit resolution. The A/Ds are designed to operate from the control bus of a wide variety of microprocessors. TRI-STATE ® output latches that directly drive the data bus permit the A/Ds to be configured as memory locations or I/O devices to the microprocessor with no interface logic necessary. Features n Easy interface to all microprocessors n Operates ratiometrically or with 5 VDC voltage reference n No zero or full-scale adjust required n 4-channel or 8-channel multiplexer with address logic n Internal clock n 0V to 5V input range with single 5V power supply n 0.3" standard width 20-pin or 24-pin DIP n 28 Pin Molded Chip Carrier Package Key Specifications n n n n n Resolution Total Unadjusted Error Single Supply Low Power Conversion Time 8 Bits ± 1⁄2 LSB and ± 1 LSB 5 VDC 15 mW 40 µs Block and Connection Diagrams DS005016-1 *ADC0848 shown in DIP Package CH5-CH8 not included on the ADC0844 TRI-STATE ® is a registered trademark of National Semiconductor Corp. © 1999 National Semiconductor Corporation DS005016 www.national.com Block and Connection Diagrams Molded Chip Carrier Package (Continued) Dual-In-Line Package Dual-In-Line Package DS005016-2 Top View DS005016-29 DS005016-30 Top View See Ordering Information Top View Ordering Information Temperature Range 0˚C to +70˚C ADC0848BCN ADC0848CCN ADC0844BCJ −40˚C to +85˚C ADC0844CCJ ADC0848BCV ADC0848CCV 8 4 8 Total Unadjusted Error MUX Channels 4 Package Outline N20A Molded Dip N24C Molded Dip J20A Cerdip V28A Molded Chip Carrier ± 1⁄2 LSB ± 1 LSB ADC0844CCN www.national.com 2 Absolute Maximum Ratings (Notes 1, 2) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage (VCC) Voltage Logic Control Inputs At Other Inputs and Outputs Input Current at Any Pin (Note 3) Package Input Current (Note 3) Storage Temperature Package Dissipation at TA = 25˚C ESD Susceptibility (Note 4) 6.5V −0.3V to +15V −0.3V to VCC+0.3V 5 mA 20 mA −65˚C to +150˚C 875 mW 800V Lead Temperature (Soldering, 10 seconds) Dual-In-Line Package (Plastic) Dual-In-Line Package (Ceramic) Molded Chip Carrier Package Vapor Phase (60 seconds) Infrared (15 seconds) 260˚C 300˚C 215˚C 220˚C (Notes 1, 2) 4.5 VDC to 6.0 VDC TMIN≤TA≤TMAX 0˚C≤TA≤70˚C −40˚C≤TA≤85˚C Operating Conditions Supply Voltage (VCC) Temperature Range ADC0844CCN, ADC0848BCN, ADC0848CCN ADC0844BCJ, ADC0844CCJ, ADC0848BCV, ADC0848CCV Electrical Characteristics The following specifications apply for VCC = 5 VDC unless otherwise specified.Boldface limits apply from TMIN to TMAX; all other limits TA = Tj = 25˚C. ADC0844BCJ ADC0844CCJ Parameter Conditions Typ (Note 5) CONVERTER AND MULTIPLEXER CHARACTERISTICS Maximum Total Unadjusted Error ADC0844BCN, ADC0848BCN, BCV ADC0844CCN, ADC0848CCN, CCV ADC0844CCJ Minimum Reference Input Resistance Maximum Reference Input Resistance Maximum Common-Mode Input Voltage Minimum Common-Mode Input Voltage DC Common-Mode Error Power Supply Sensitivity Off Channel Leakage Current Differential Mode VCC = 5V ± 5% (Note 10) On Channel = 5V, Off Channel = 0V On Channel = 0V, Off Channel = 5V DIGITAL AND DC CHARACTERISTICS VIN(1), Logical “1” Input Voltage (Min) VIN(0), Logical “0” Input Voltage (Max) IIN(1), Logical “1” Input Current (Max) IIN(0), Logical “0” Input Current (Max) VOUT(1), Logical “1” Output Voltage (Min) VIN = 0V VCC = 4.75V IOUT = −360 µA IOUT = −10 µA 2.4 4.5 2.8 4.6 2.4 4.5 V V −0.005 −1 −0.005 −1 µA VIN = 5.0V 0.005 1 0.005 1 µA VCC = 4.75V 0.8 0.8 0.8 V VCC = 5.25V 2.0 2.0 2.0 V 1 0.1 1 µA −1 −0.1 −1 µA (Note 9) GND−0.05 GND−0.05 GND−0.05 V LSB LSB (Note 9) VCC+0.05 VCC+0.05 VCC+0.05 V 2.4 5.9 2.4 5.4 5.9 kΩ 2.4 VREF = 5.00 VDC (Note 8) Tested Limit (Note 6) Design Limit (Note 7) ADC0844CCN ADC0848BCN, ADC0848CCN ADC0848BCV, ADC0848CCV Typ (Note 5) Tested Limit (Note 6) Design Limit (Note 7) Limit Units ± 1⁄2 ±1 ±1 1.1 2.4 1.2 ± 1⁄2 ±1 1.1 LSB LSB LSB kΩ ± 1/16 ± 1/16 ± 1⁄4 ± 1⁄8 ± 1/16 ± 1/16 ± 1⁄4 ± 1⁄8 ± 1⁄4 ± 1⁄8 3 www.national.com Electrical Characteristics (Continued) The following specifications apply for VCC = 5 VDC unless otherwise specified.Boldface limits apply from TMIN to TMAX; all other limits TA = Tj = 25˚C. ADC0844BCJ ADC0844CCJ Parameter Conditions Typ (Note 5) DIGITAL AND DC CHARACTERISTICS VOUT(0), Logical “0” Output Voltage (Max) IOUT, TRI-STATE Output Current (Max) ISOURCE, Output Source Current (Min) ISINK, Output Sink Current (Min) ICC, Supply Current (Max) CS = 1, VREF Open 1 2.5 1 2.3 2.5 mA VOUT = VCC 16 8.0 16 9.0 8.0 mA VCC = 4.75V IOUT = 1.6 mA VOUT = 0V VOUT = 5V VOUT = 0V −0.01 0.01 −14 −3 3 −6.5 −0.01 0.01 −14 −0.3 0.3 −7.5 −3 3 −6.5 µA µA mA 0.4 0.34 0.4 V Tested Limit (Note 6) Design Limit (Note 7) ADC0844CCN ADC0848BCN, ADC0848CCN ADC0848BCV, ADC0848CCV Typ (Note 5) Tested Limit (Note 6) Design Limit (Note 7) Limit Units AC Electrical Characteristics The following specifications apply for VCC = 5VDC, tr = tf = 10 ns unless otherwise specified. Boldface limits apply from TMIN to TMAX; all other limits TA = Tj = 25˚C. Tested Parameter tC, Maximum Conversion Time (See Graph) tW(WR), Minimum WR Pulse Width tACC, Maximum Access Time (Delay from Falling Edge of RD to Output Data Valid) t1H, t0H, TRI-STATE Control (Maximum Delay from Rising Edge of RD to Hi-Z State) tWI, tRI, Maximum Delay from Falling Edge of WR or RD to Reset of INTR tDS, Minimum Data Set-Up Time tDH, Minimum Data Hold Time CIN, Capacitance of Logic Inputs COUT, Capacitance of Logic Outputs (Note 11) (Note 11) 50 0 5 5 100 50 ns ns pF pF (Note 11) CL = 100 pF (Note 11) CL = 10 pF, RL = 10k (Note 11) (Note 11) 200 400 ns Conditions Typ (Note 5) 30 50 145 125 Limit (Note 6) 40 150 225 200 Design Limit (Note 7) 60 µs ns ns ns Units Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not apply when operating the device beyond its specified operating conditions. Note 2: All voltages are measured with respect to the ground pins. Note 3: When the input voltage (VIN) at any pin exceeds the power supply rails (VIN < V−or VIN > V+) the absolute value of the current at that pin should be limited to 5 mA or less. The 20 mA package input current limits the number of pins that can exceed the power supply boundaries with a 5 mA current limit to four. Note 4: Human body model, 100 pF discharged through a 1.5 kΩ resistor. Note 5: Typicals are at 25˚C and represent most likely parametric norm. Note 6: Tested limits are guaranteed to National’s AOQL (Average Outgoing Quality Level). Note 7: Design limits are guaranteed by not 100% tested. These limits are not used to calculate outgoing quality levels. Note 8: Total unadjusted error includes offset, full-scale, linearity, and multiplexer error. Note 9: For VIN (−) ≥ VIN(+) the digital output code will be 0000 0000. Two on-chip diodes are tied to each analog input, which will forward-conduct for analog input voltages one diode drop below ground or one diode drop greater than VCC supply. Be careful during testing at low VCC levels (4.5V), as high level analog inputs (5V) can cause this input diode to conduct, especially at elevated temperatures, and cause errors for analog inputs near full-scale. The spec allows 50 mV forward bias of either diode. This means that as long as the analog VIN does not exceed the supply voltage by more than 50 mV, the output code will be correct. To achieve an absolute 0 VDC to 5 VDC input voltage range will therefore require a minimum supply voltage of 4.950 VDC over temperature variations, initial tolerance and loading. Note 10: Off channel leakage current is measured after the channel selection. Note 11: The temperature coefficient is 0.3%/˚C. www.national.com 4 Typical Performance Characteristics Logic Input Threshold Voltage vs Supply Voltage Output Current vs Temperature Power Supply Current vs Temperature DS005016-31 DS005016-32 DS005016-33 Linearity Error vs VREF Conversion Time vs VSUPPLY DS005016-34 DS005016-35 Conversion Time vs Temperature Unadjusted Offset Error vs VREF Voltage DS005016-36 DS005016-37 5 www.national.com TRI-STATE Test Circuits and Waveforms t1H t1H, CL = 10 pF DS005016-4 DS005016-5 tr = 20 ns t0H t0H, CL = 10 pF DS005016-7 DS005016-6 tr = 20 ns Leakage Current Test Circuit DS005016-8 www.national.com 6 Timing Diagrams Programming New Channel Configuration and Starting a Conversion DS005016-9 Note 12: Read strobe must occur at least 600 ns after the assertion of interrupt to guarantee reset of INTR . Note 13: MA stands for MUX address. Using the Previously Selected Channel Configuration and Starting a Conversion DS005016-10 7 www.national.com ADC0848 Functional Block Diagram DS005016-11 www.national.com 8 Functional Description The ADC0844 and ADC0848 contain a 4-channel and 8-channel analog input multiplexer (MUX) respectively. Each MUX can be configured into one of three modes of operation differential, pseudo-differential, and single ended. These modes are discussed in the Applications Information Section. The specific mode is selected by loading the MUX address latch with the proper address (see Table 1 and Table 2). Inputs to the MUX address latch (MA0-MA4) are common with data bus lines (DB0-DB4) and are enabled when the RD line is high. A conversion is initiated via the CS and WR lines. If the data from a previous conversion is not read, the INTR line will be low. The falling edge of WR will reset the INTR line high and ready the A/D for a conversion cycle. The rising edge of WR, with RD high, strobes the data on the MA0/ DB0-MA4/DB4 inputs into the MUX address latch to select a new input configuration and start a conversion. If the RD line is held low during the entire low period of WR the previous MUX configuration is retained, and the data of the previous conversion is the output on lines DB0-DB7. After the conversion cycle (tC ≤ 40 µs), which is set by the internal clock frequency, the digital data is transferred to the output latch and the INTR is asserted low. Taking CS and RD low resets INTR output high and outputs the conversion result on the data lines (DB0-DB7). The actual voltage converted is always the difference between an assigned “+” input terminal and a “−” input terminal. The polarity of each input terminal of the pair being converted indicates which line the converter expects to be the most positive. If the assigned “+” input is less than the “−” input the converter responds with an all zeros output code. A unique input multiplexing scheme has been utilized to provide multiple analog channels. The input channels can be software configured into three modes: differential, single ended, or pseudo-differential. Figure 1 shows the three modes using the 4-channel MUX ADC0844. The eight inputs of the ADC0848 can also be configured in any of the three modes. In the differential mode, the ADC0844 channel inputs are grouped in pairs, CH1 with CH2 and CH3 with CH4. The polarity assignment of each channel in the pair is interchangeable. The single-ended mode has CH1–CH4 assigned as the positive input with the negative input being the analog ground (AGND) of the device. Finally, in the pseudo-differential mode CH1–CH3 are positive inputs referenced to CH4 which is now a pseudo-ground. This pseudo-ground input can be set to any potential within the input common-mode range of the converter. The analog signal conditioning required in transducer-based data acquisition systems is significantly simplified with this type of input flexibility. One converter package can now handle ground referenced inputs and true differential inputs as well as signals with some arbitrary reference voltage. The analog input voltages for each channel can range from 50 mV below ground to 50 mV above VCC (typically 5V) without degrading conversion accuracy. Applications Information 1.0 MULTIPLEXER CONFIGURATION The design of these converters utilizes a sampled-data comparator structure which allows a differential analog input to be converted by a successive approximation routine. TABLE 1. ADC0844 MUX ADDRESSING MUX Address MA3 X X X X L L L L H H H X X = don’t care CS MA0 L H L H L H L H L H L X L L L L L L L L L L L L WR RD CH1 H + − CH2 − + Channel# CH3 CH4 AGND MUX Mode Differential MA2 L L L L H H H H H H H X MA1 L L H H L L H H L L H X L H H H H + − + + + − + − − − + − PseudoDifferential − Single-Ended L H H H H + L L H H L + + − − Previous Channel Configuration 9 www.national.com Applications Information 4 Single-Ended (Continued) 2 Differential DS005016-12 DS005016-13 3 Pseudo-Differential Combined DS005016-14 DS005016-15 FIGURE 1. Analog Input Multiplexer Options 2.0 REFERENCE CONSIDERATIONS The voltage applied to the reference input of these converters defines the voltage span of the analog input (the difference between VIN(MAX) and VIN(MIN)) over which the 256 possible output codes apply. The devices can be used in either ratiometric applications or in systems requiring absolute accuracy. The reference pin must be connected to a voltage source capable of driving the minimum reference input resistance of 1.1 kΩ. This pin is the top of a resistor divider string used for the successive approximation conversion. In a ratiometric system (Figure 2a), the analog input voltage is proportional to the voltage used for the A/D reference. This voltage is typically the system power supply, so the VREF pin can be tied to VCC. This technique relaxes the stability requirements of the system reference as the analog input and A/D reference move together maintaining the same output code for a given input condition. For absolute accuracy (Figure 2b), where the analog input varies between very specific voltage limits, the reference pin can be biased with a time and temperature stable voltage source. The LM385 and LM336 reference diodes are good low current devices to use with these converters. The maximum value of the reference is limited to the VCC supply voltage. The minimum value, however, can be quite small (see Typical Performance Characteristics) to allow direct conversions of transducer outputs providing less than a 5V output span. Particular care must be taken with regard to noise pickup, circuit layout and system error voltage sources when operating with a reduced span due to the increased sensitivity of the converter (1 LSB equals VREF/256). 3.0 THE ANALOG INPUTS 3.1 Analog Differential Voltage Inputs and Common-Mode Rejection The differential input of these converters actually reduces the effects of common-mode input noise, a signal common to both selected “+” and “−” inputs for a conversion (60 Hz is www.national.com 10 most typical). The time interval between sampling the “+” input and then the “−” inputs is 1⁄2 of a clock period. The change in the common-mode voltage during this short time interval can cause conversion errors. For a sinusoidal common-mode signal this error is: DS005016-38 where fCM is the frequency of the common-mode signal, Vpeak is its peak voltage value and tC is the conversion time. For a 60 Hz common-mode signal to generate a 1⁄4 LSB error (≈5 mV) with the converter running at 40 µS, its peak value would have to be 5.43V. This large a common-mode signal is much greater than that generally found in a well designed data acquisition system. Applications Information MUX Address MA4 MA3 MA2 MA1 MA0 X X X X X X X X L L L L L L L L H H H H H H H X L L L L L L L L H H H H H H H H H H H H H H H X L L L L H H H H L L L L H H H H L L L L H H H X L L H H L L H H L L H H L L H H L L H H L L H X L H L H L H L H L H L H L H L H L H L H L H L X L L L L L L L L L L L L L L L L L L L L L L L L L L L L (Continued) TABLE 2. ADC0848 MUX Addressing CS WR RD CH1 H H H H H H H H H H H H H H H H H H H H H H H L + + + + + + + + + − CH2 − + + − − + CH3 CH4 Channel CH5 CH6 CH7 CH8 AGND MUX Mode Differential + − − + + − − + − − − − + + + + − − − − + + + − − − PseudoDifferential − − − − Single-Ended Previous Channel Configuration put 0000 0000 digital code for this minimum input voltage by biasing any VIN (−) input at this VIN(MIN) value. This is useful for either differential or pseudo-differential modes of input channel configuration. The zero error of the A/D converter relates to the location of the first riser of the transfer function and can be measured by grounding the V− input and applying a small magnitude positive voltage to the V+ input. Zero error is the difference between actual DC input voltage which is necessary to just cause an output digital code transition from 0000 0000 to 0000 0001 and the ideal 1⁄2 LSB value (1⁄2 LSB = 9.8 mV for VREF = 5.000 VDC). 4.2 Full-Scale The full-scale adjustment can be made by applying a differential input voltage which is 1 1⁄2 LSB down from the desired analog full-scale voltage range and then adjusting the magnitude of the VREF input for a digital output code changing from 1111 1110 to 1111 1111. 4.3 Adjusting for an Arbitrary Analog Input Voltage Range If the analog zero voltage of the A/D is shifted away from ground (for example, to accommodate an analog input signal which does not go to ground), this new zero reference should be properly adjusted first. A VIN (+) voltage which equals this desired zero reference plus 1⁄2 LSB (where the 11 www.national.com 3.2 Input Current Due to the sampling nature of the analog inputs, short duration spikes of current enter the “+” input and exit the “−” input at the clock edges during the actual conversion. These currents decay rapidly and do not cause errors as the internal comparator is strobed at the end of a clock period. Bypass capacitors at the inputs will average these currents and cause an effective DC current to flow through the output resistance of the analog signal source. Bypass capacitors should not be used if the source resistance is greater than 1 kΩ. 3.3 Input Source Resistance The limitation of the input source resistance due to the DC leakage currents of the input multiplexer is important. A worst-case leakage current of ± 1 µA over temperature will create a 1 mV input error with a 1 kΩ source resistance. An op amp RC active low pass filter can provide both impedance buffering and noise filtering should a high impedance signal source be required. 4.0 OPTIONAL ADJUSTMENTS 4.1 Zero Error The zero of the A/D does not require adjustment. If the minimum analog input voltage value, VIN(MIN), is not ground, a zero offset can be done. The converter can be made to out- Applications Information (Continued) reference voltage at the corresponding “−” input should then be adjusted to just obtain the 00HEX to 01HEX code transition. LSB is calculated for the desired analog span, 1 LSB = analog span/256) is applied to selected “+” input and the zero DS005016-16 a) Ratiometric b) Absolute with a Reduced Span FIGURE 2. Referencing Examples The full-scale adjustment should be made [with the proper VIN (−) voltage applied] by forcing a voltage to the VIN (+) input which is given by: DS005016-17 The VREF (or VCC) voltage is then adjusted to provide a code change from FEHEX to FFHEX. This completes the adjustment procedure. For an example see the Zero-Shift and Span Adjust circuit below. where VMAX = the high end of the analog input range and VMIN = the low end (the offset zero) of the analog range. (Both are ground referenced.) Zero-Shift and Span Adjust (2V≤VIN≤5V) DS005016-18 www.national.com 12 Applications Information (Continued) Differential Voltage Input 9-Bit A/D DS005016-19 Span Adjust (0V≤VIN≤3V) DS005016-20 Protecting the Input DS005016-21 Diodes are 1N914 13 www.national.com Applications Information (Continued) High Accuracy Comparators DS005016-22 DO = all 1s if VIN(+) > VIN(−) DO = all 0s if VIN(+) < VIN(−) Operating with Automotive Ratiometric Transducers DS005016-23 *VIN(−) = 0.15 VCC 15% of VCC≤VXDR≤85% of VCC www.national.com 14 Applications Information (Continued) A Stand Alone Circuit DS005016-25 Note: DUT pin numbers in parentheses are for ADC0844, others are for ADC0848. Start a Conversion without Updating the Channel Configuration DS005016-26 CS • WR will update the channel configuration and start a conversion. CS • RD will read the conversion data and start a new conversion without updating the channel configuration. Waiting for the end of this conversion is not necessary. A CS • WR can immediately follow the CS • RD . 15 www.national.com Applications Information (Continued) ADC0844 — INS8039 Interface DS005016-27 SAMPLE PROGRAM FOR ADC0844 — INS8039 INTERFACE CONVERTING TWO RATIOMETRIC, DIFFERENTIAL SIGNALS ORG 0000 0010 0012 0014 0016 0018 001A 001C 001D 04 10 B9 FF B8 20 89 FF 23 00 14 50 23 02 18 14 50 BEGIN: JMP ORG MOV MOV ORL MOV CALL MOV INC CALL 0H BEGIN 10H R1,#0FFH R0,#20H P1,#0FFH A,00H CONV A,#02H R0 CONV ;START PROGRAM AT ADDR 10 ;MAIN PROGRAM ;LOAD R1 WITH A UNUSED ADDR ;LOCATION ;A/D DATA ADDRESS ;SET PORT 1 OUTPUTS HIGH ;LOAD THE ACC WITH A/D MUX DATA ;CH1 AND CH2 DIFFERENTIAL ;CALL THE CONVERSION SUBROUTINE ;LOAD THE ACC WITH A/D MUX DATA ;CH3 AND CH4 DIFFERENTIAL ;INCREMENT THE A/D DATA ADDRESS ;CALL THE CONVERSION SUBROUTINE ;CONTINUE MAIN PROGRAM ;CONVERSION SUBROUTINE ;ENTRY:ACC — A/D MUX DATA ;EXIT: ACC — CONVERTED DATA ORG 0050 0052 0053 99 FE 91 09 LOOP: CONV: ANL MOVX IN 50H P1,#0FEH @ R1,A ;CHIP SELECT THE A/D ;LOAD A/D MUX & START CONVERSION ;INPUT INTR STATE A,P1 www.national.com 16 Applications Information (Continued) SAMPLE PROGRAM FOR ADC0844 — INS8039 INTERFACE CONVERTING TWO RATIOMETRIC, DIFFERENTIAL SIGNALS (Continued) 0054 0056 0057 0059 005A 32 53 81 89 01 A0 83 JB1 MOVX ORL MOV RET I/O Interface to NSC800 LOOP A,@R1 P1,&01H @ R0,A ;IF INTR = 1 GOTO LOOP ;IF INTR = 0 INPUT A/D DATA ;CLEAR THE A/D CHIP SELECT ;STORE THE A/D DATA ;RETURN TO MAIN PROGRAM DS005016-28 SAMPLE PROGRAM FOR ADC0848 — NSC800 INTERFACE 0008 000F 001F 3C00 0000' 0004' 0008' 000A' 000C' 000F' 0012' 0014' 0015' 0017' 0018' 001B' 001D' 001E' 08 09 0A 0B 0C 0D 0E 0F 0E 1F 06 16 21 0000' 11 003C ED A3 EB 3E 0F 3D C2 0013' ED A2 EB C2 000E' WAIT: STCONV: START: NCONV DEL CS ADDTA MUXDTA: EQU EQU EQU EQU DB DB LD LD LD LD OUTI EX LD DEC JP INI EX JP END Note 14: This routine sequentially programs the MUX data latch in the signal-ended mode. For CH1-CH8 a conversion is started, then a 50 µs wait for the A/D to complete a conversion and the data is stored at address ADDTA for CH1, ADDTA + 1 for CH2, etc. 16 15 1FH 003CH 08H,09H,0AH,0BH 0CH,0DH,0EH,0FH C,CS B,NCONV HL,MUXDTA DE,ADDTA ;LOAD A/D’S MUX DATA ;AND START A CONVERSION DE,HL A,DEL A NZ,WAIT ;WAIT 50 µsec FOR THE ;CONVERSION TO FINISH ;STORE THE A/D’S DATA ;CONVERTED ALL INPUTS? DE,HL NZ,STCONV ;IF NOT GOTO STCONV ;HL = RAM ADDRESS FOR THE ;A/D DATA ;DELAY 50 µsec CONVERSION ;THE BOARD ADDRESS ;START OF RAM FOR A/D ;DATA ;MUX DATA 17 www.national.com Physical Dimensions inches (millimeters) unless otherwise noted Ceramic Dual-In-Line Package (J) NS Package Number J20A Molded Dual-In-Line Package (N) NS Package Number N20A www.national.com 18 Physical Dimensions inches (millimeters) unless otherwise noted (Continued) Molded Dual-In-Line Package (N) NS Package Number N24C 19 www.national.com ADC0844/ADC0848 8-Bit µP Compatible A/D Converters with Multiplexer Options Physical Dimensions inches (millimeters) unless otherwise noted (Continued) Molded Chip Carrier Package (V) NS Package Number V28A LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. 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