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ADC0816/ADC0817

8-Bit µP Compatible A/D Converters with 16-Channel

Multiplexer

General Description

The ADC0816, ADC0817 data acquisition component is a

monolithic CMOS device with an 8-bit analog-to-digital con-

verter, 16-channel multiplexer and microprocessor compat-

ible control logic. The 8-bit A/D converter uses successive

approximation as the conversion technique. The converter

features a high impedance chopper stabilized comparator, a

256R voltage divider with analog switch tree and a succes-

sive approximation register. The 16-channel multiplexer can

directly access any one of 16-single-ended analog signals,

and provides the logic for additional channel expansion. Sig-

nal conditioning of any analog input signal is eased by direct

access to the multiplexer output, and to the input of the 8-bit

A/D converter.

The device eliminates the need for external zero and

full-scale adjustments. Easy interfacing to microprocessors

is provided by the latched and decoded multiplexer address

inputs and latched TTL TRI-STATE

outputs.

The design of the ADC0816, ADC0817 has been optimized

by incorporating the most desirable aspects of several A/D

conversion techniques. The ADC0816, ADC0817 offers high

speed, high accuracy, minimal temperature dependence, ex-

cellent long-term accuracy and repeatability, and consumes

minimal power. These features make this device ideally

suited to applications from process and machine control to

consumer and automotive applications. For similar perfor-

mance in an 8-channel, 28-pin, 8-bit A/D converter, see the

ADC0808, ADC0809 data sheet. (See AN-258 for more in-

formation.)

Features

n Easy interface to all microprocessors, or operates “stand

alone”

n Operates ratiometrically or with 5 V

or analog span

adjusted voltage reference

n 16-channel multiplexer with latched control logic

n Outputs meet TTL voltage level specifications

n 0V to 5V analog input voltage range with single 5V

supply

n No zero or full-scale adjust required

n Standard hermetic or molded 40-pin DIP package

n Temperature range −40˚C to +85˚C or −55˚C to +125˚C

n Latched TRI-STATE output

n Direct access to “comparator in” and “multiplexer out” for

signal conditioning

n ADC0816 equivalent to MM74C948

n ADC0817 equivalent to MM74C948-1

Key Specifications

n Resolution: 8 Bits

n Total Unadjusted Error:

⁄

LSB and

1 LSB

n Single Supply: 5 V

n Low Power: 15 mW

n Conversion Time: 100 µs

TRI-STATE

is a registered trademark of National Semiconductor Corporation.

December 1994

ADC0816/ADC0817 8-Bit µP Compatible A/D Converters with 16-Channel Multiplexer

Summary of content (14 pages)

PAGE 1
ADC0816/ADC0817 8-Bit µP Compatible A/D Converters with 16-Channel Multiplexer General Description Features The ADC0816, ADC0817 data acquisition component is a monolithic CMOS device with an 8-bit analog-to-digital converter, 16-channel multiplexer and microprocessor compatible control logic. The 8-bit A/D converter uses successive approximation as the conversion technique.
PAGE 2
Block Diagram DS005277-1 www.national.
PAGE 3
Absolute Maximum Ratings Molded Chip Carrier Package Vapor Phase (60 seconds) Infrared (15 seconds) ESD Susceptibility (Note 9) (Notes 1, 2) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. 215˚C 220˚C 400V Operating Conditions Supply Voltage (VCC) (Note 3) 6.5V Voltage at Any Pin −0.3V to (VCC+0.3V) Except Control Inputs Voltage at Control Inputs −0.
PAGE 4
Electrical Characteristics (Continued) Digital Levels and DC Specifications: ADC0816CCJ, ADC0816CCN, ADC0817CCN — 4.75V≤VCC≤5.25V, −40˚C≤TA≤+85˚C unless otherwise noted. Symbol Parameter Conditions Min Typ Max Units CONTROL INPUTS VIN(1) Logical “1” Input Voltage VIN(0) Logical “0” Input Voltage IIN(1) Logical “1” Input Current VCC−1.5 V VIN = 15V 1.5 V 1.0 µA (The Control Inputs) IIN(0) Logical “0” Input Current VIN = 0 −1.
PAGE 5
Additional single-ended analog signals can be multiplexed to the A/D converter by disabling all the multiplexer inputs using the expansion control. The additional external signals are connected to the comparator input and the device ground. Additional signal conditioning (i.e., prescaling, sample and hold, instrumentation amplification, etc.) may also be added between the analog input signal and the comparator input.
PAGE 6
Functional Description (Continued) DS005277-4 FIGURE 3. 3-Bit A/D Absolute Accuracy Curve DS005277-3 FIGURE 2. 3-Bit A/D Transfer Curve DS005277-5 FIGURE 4. Typical Error Curve Timing Diagram DS005277-7 FIGURE 5. www.national.
PAGE 7
Timing Diagram The most important section of the A/D converter is the comparator. It is this section which is responsible for the ulimate accuracy of the entire converter. It is also the comparator drift which has the greatest influence on the repeatability of the device. A chopper-stabilized comparator provides the most effective method of satisfying all the converter requirements. (Continued) The successive approximation register (SAR) performs 8 iterations to approximate the input voltage.
PAGE 8
Typical Performance Characteristics DS005277-18 DS005277-19 FIGURE 6. Comparator IIN vs VIN (VCC = VREF = 5V) FIGURE 7. Multiplexer RON vs VIN (VCC = VREF = 5V) TRI-STATE Test Circuits and Timing Diagrams DS005277-9 DS005277-10 FIGURE 8. Applications Information OPERATION (1) 1.0 RATIOMETRIC CONVERSION The ADC0816, ADC0817 is designed as a complete Data Acquisition System (DAS) for ratiometric conversion systems.
PAGE 9
Applications Information 2.0 RESISTOR LADDER LIMITATIONS The voltages from the resistor ladder are compared to the selected input 8 times in a conversion. These voltages are coupled to the comparator via an analog switch tree which is referenced to the supply. The voltages at the top, center and bottom of the ladder must be controlled to maintain proper operation.
PAGE 10
Applications Information (Continued) DS005277-12 FIGURE 10. Ground Referenced Conversion System Using Trimmed Supply DS005277-13 FIGURE 11. Ground Referenced Conversion System with Reference Generating VCC Supply DS005277-14 FIGURE 12. Typical Reference and Supply Circuit www.national.
PAGE 11
Applications Information (Continued) DS005277-15 FIGURE 13. Symmetrically Centered Reference VREF(+) ÷512) 4.0 ANALOG COMPARATOR INPUTS The dynamic comparator input current is caused by the periodic switching of on-chip stray capacitances These are connected alternately to the output of the resistor ladder/ switch tree network and to the comparator input as part of the operation of the chopper stabilized comparator.
PAGE 12
Typical Application DS005277-16 *Address latches needed for 8085 and SC/MP interfacing the ADC0816, 17 to a microprocessor Microprocessor Interface Table PROCESSOR READ WRITE INTERRUPT (COMMENT) 8080 MEMR MEMW INTR (Thru RST Circuit) 8085 RD WR INTR (Thru RST Circuit) Z-80 RD WR INT (Thru RST Circuit, Mode 0) SC/MP NRDS NWDS SA (Thru Sense A) 6800 VMA • φ 2 • R/W VMA • Q2 • R/W IRQA or IRQB (Thru PIA) Ordering Information TEMPERATURE RANGE Error −40˚C to +85˚C ± 1⁄2 Bit Unadjust
PAGE 13
Physical Dimensions inches (millimeters) unless otherwise noted Cavity Dual-In-Line Package (J) NS Package Number J40A Molded Dual-In-Line Package (N) NS Package Number N40A 13 www.national.
PAGE 14
ADC0816/ADC0817 8-Bit µP Compatible A/D Converters with 16-Channel Multiplexer 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 OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 2. A critical component in any component of a life support 1.