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ADC08831/ADC08832

8-Bit Serial I/O CMOS A/D Converters with Multiplexer

and Sample/Hold Function

General Description

The ADC08831/ADC08832 are 8-bit successive approxima-

tion Analog to Digital converters with 3-wire serial interfaces

and a configurable input multiplexer for 2 channels. The se-

rial I/O will interface to COPS

™

family, PLD’s, microproces-

sors, DSP’s, or shift registers. The serial I/O is configured to

comply with the NSC MICROWIRE

™

serial data exchange

standard.

To minimize total power consumption, the

ADC08831/ADC08832 automatically go into low power

mode whenever they are not performing conversions.

A track/hold function allows the analog voltage at the positive

input to vary during the actual A/D conversion.

The analog inputs can be configured to operate in various

combination of single-ended, differential, or

pseudo-differential modes. The voltage reference input can

be adjusted to allow encoding of small analog voltage spans

to the full 8-bits of resolution.

Applications

n Digitizing sensors and waveforms

n Process control monitoring

n Remote sensing in noisy environments

n Instrumentation

n Embedded Systems

Features

n 3-wire serial digital data link requires few I/O pins

n Analog input track/hold function

n 2-channel input multiplexer option with address logic

n Analog input voltage range from GND to V

n No zero or full scale adjustment required

n TTL/CMOS input/output compatible

n Superior pin compatible replacement for ADC0831/2

Key Specifications

n Resolution: 8 bits

n Conversion time (f

2 MHz): 4µs (max)

n Power dissipation: 8.5mW (typ)

n Low power mode 3.0mW (typ)

n Single supply: 5V

n Total unadjusted error:

1LSB

n No missing codes over temperature

Typical Application

COPS

™

is a trademark of National Semiconductor Corporation.

MICROWIRE

™

is a trademark of National Semiconductor Corporation.

TRI-STATE

™

DS100108-44

DS100108-43

December 1998

ADC08831/ADC08832 8-Bit Serial I/O CMOS A/D Converters with Multiplexer and Sample/Hold

Function

Summary of content (24 pages)

PAGE 1
ADC08831/ADC08832 8-Bit Serial I/O CMOS A/D Converters with Multiplexer and Sample/Hold Function General Description The ADC08831/ADC08832 are 8-bit successive approximation Analog to Digital converters with 3-wire serial interfaces and a configurable input multiplexer for 2 channels. The serial I/O will interface to COPS™family, PLD’s, microprocessors, DSP’s, or shift registers. The serial I/O is configured to comply with the NSC MICROWIRE™ serial data exchange standard.
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Connection Diagrams ADC08831 Wide Body SO Packages ADC08832 Wide Body SO Packages DS100108-4 DS100108-3 ADC08831 N,M,MM Packages ADC08832 N,M,MM Packages DS100108-2 DS100108-1 Ordering Information Temperature Range Package Industrial (−40˚C ≤ TJ ≤ +85˚C) ADC08831IN N08E ADC08832IN ADC08831IWM, M14B ADC08832IWM, ADC08831IM, M08A ADC08832IM, ADC08831IMM, MUA08A ADC08832IMM, www.national.
PAGE 3
Absolute Maximum Ratings (Notes 1, 3) Mounting Temperature Lead Temp. (soldering, 10 sec) Infrared (10 sec) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.
PAGE 4
Electrical Characteristics (Continued) The following specifications apply for VCC = VREF = +5VDC, and fCLK = 2 MHz unless otherwise specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25˚C. Symbol Parameter Conditions Typical (Note 8) Limits (Note 9) Units (Limits) DC CHARACTERISTICS ICC Supply Current CLK = high ICC ADC08831 Supply Current ADC08832 CLK = high (Note 16) CS = VCC CS = LOW CS = VCC CS = LOW 0.6 1.0 mA (max) 1.7 2.4 mA (max) 1.3 1.
PAGE 5
Dynamic Characteristics The following specifications apply for VCC = 5V, fCLK = 2MHz, TA = 25˚C, RSOURCE = 50Ω, fIN = 45kHz, VIN = 5VP-P, VREF = 5V, non-coherent 2048 samples with windowing. Symbol Parameter ADC08831 ADC08832 Conditions Typical (Note 8) fCLK/11 fCLK/13 Limits (Note 9) Units (Limits) 181 153 ksps ksps fS Sampling Rate SNR Signal-to -Noise Ratio (Note 19) 48.5 dB THD Total Harmonic Distortion (Note 20) −59.5 dB SINAD Signal-to -Noise and Distortion 48.
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Block Diagram DS100108-47 *For ADC08831 VREF pin is available, for ADC08832 DI pin is available, and VREF is tied to VCC Pin names in parentheses refer to ADC08832 www.national.
PAGE 7
Typical Performance Characteristics The following specifications apply for TA = 25˚C, VCC = VREF = 5V, unless otherwise specified.
PAGE 8
Typical Performance Characteristics The following specifications apply for TA = 25˚C, VCC = VREF = 5V, unless otherwise specified. (Continued) Spectral Response with 10KHz Sine Wave Input Spectral Response with 55 KHz Sine Wave Input DS100108-13 Spectral Response with 90 KHz Sine Wave Input DS100108-34 DS100108-16 Total Unadjuster Error Plot DS100108-38 Leakage Current Test Circuit DS100108-5 www.national.
PAGE 9
TRI-STATE Test Circuits and Waveforms DS100108-20 DS100108-21 Timing Diagrams Data Input Timing DS100108-22 Data Output Timing DS100108-23 9 www.national.
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Timing Diagrams (Continued) ADC08831 Start Conversion Timing DS100108-24 ADC08831 Timing DS100108-25 *LSB first output not available on ADC08831. ADC08832 Timing DS100108-26 www.national.
PAGE 11
*Some of these functions/pins are not available with other options. DS100108-12 ADC08832 Functional Block Diagram 11 www.national.
PAGE 12
Since the input configuration is under software control, it can be modified as required before each conversion. A channel can be treated as a single-ended, ground referenced input for one conversion; then it can be reconfigured as part of a differential channel for another conversion. The analog input voltages for each channel can range from 50mV below ground to 50mV above VCC (typically 5V) without degrading conversion accuracy. Functional Description 1.
PAGE 13
Functional Description digital logic enter static current modes. However power dissipation from the reference ladder occurs, regardless of the signal on CS (Continued) 3.0 Reducing Power Consumption The ADC08831 operate up to a 2MHz clock frequency, or about 181 ksps. At 5V supply, it consumes about 1.7 mA or 8.5 mW when CS is logic low. The ADC08831 has a low power mode to minimize total power consumption.
PAGE 14
Functional Description 5.4 Board layout Consideration, grounding and bypassing: (Continued) 5.0 THE ANALOG INPUTS The ADC08831/2 are easy to use with some board layout consideration. They should be used with an analog ground plane and single-point grounding techniques. The GND pin should be tied directly to the ground plane.
PAGE 15
Functional Description 7.4 Signal-to-Noise And Distortion Signal-to-Noise And Distortion ratio (SINAD) is the ratio of RMS magnitude of the fundamental to the RMS sum of all the non-fundamental signals, including the noise and harmonics, up to 1/2 of the sampling frequency (Nyquist), excluding DC. (Continued) The VREFIN (or VCC) voltage is then adjusted to provide a code change from FEHEX to FFHEX. This completes the adjustment procedure. 7.
PAGE 16
Applications Low-Cost Remote Temperature Sensor DS100108-6 Operating with Ratiometric Transducers DS100108-7 *VIN(−) = 0.15 VCC 15% of VCC ≤ VXDR ≤ 85% of VCC www.national.
PAGE 17
Applications (Continued) Span Adjust; 0V ≤ VIN ≤ 3V DS100108-8 Zero-Shift and Span Adjust: 2V≤VIN ≤ 5V 17 www.national.
PAGE 18
Applications (Continued) Protecting the Input DS100108-9 Diodes are 1N914 Digital Load Cell DS100108-10 • • • • Uses one more wire than load cell itself Two mini-DIPs could be mounted inside load cell for digital output transducer Electronic offset and gain trims relax mechanical specs for gauge factor and offset Low level cell output is converted immediately for high noise immunity www.national.
PAGE 19
Applications (Continued) 4 mA-20 mA Current Loop Converter DS100108-11 • All power supplied by loop • 1500V isolation at output Isolated Data Converter DS100108-40 19 www.national.
PAGE 20
Applications (Continued) A “Stand-Alone” Hook-Up for ADC08832 Evaluation DS100108-39 www.national.
PAGE 21
PAGE 22
Physical Dimensions inches (millimeters) unless otherwise noted Order Number ADC08831IWM, ADC08832IWM, NS Package Number M14B Order Number ADC08831IM or ADC08832IM NS Package Number M08A www.national.
PAGE 23
Physical Dimensions inches (millimeters) unless otherwise noted (Continued) Order Number ADC08831IN, ADC08832IN NS Package Number N08E 23 www.national.
PAGE 24
ADC08831/ADC08832 8-Bit Serial I/O CMOS A/D Converters with Multiplexer and Sample/Hold Function Physical Dimensions inches (millimeters) unless otherwise noted (Continued) Order Number ADC08831IMM or ADC08832IMM NS Package Number MUA08A 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.