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Analog Devices - Universal Multichannel Industrial Signal Conditioning ADC

Numéro de référence AD280
Description Universal Multichannel Industrial Signal Conditioning ADC
Fabricant Analog Devices 
Logo Analog Devices 





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AD280 fiche technique
a
Universal Multichannel Industrial
Signal Conditioning ADC
PRELIMINARY TECHNICAL DATA
AD280
FEATURES
Four Input Channels, with Protection and Switchable
Attenuation
Provision for Cold Junction Sensor
Programmable Excitation Sources for RTD Measure-
ment and Open Input Detection
PGA with Programmable Gains from 1 to 128
High Resolution Integrating A/D Converter with Pro-
grammable Integration Period, Up to 18-Bit Usable
Resolution
2.5 Volt Reference
Crystal Oscillator
Charge Pump Circuit to Allow Single +5 V Power
Serial Interface Compatible with Most Microcontrollers
and Microprocessors
APPLICATIONS
Industrial Data Acquisition
DCS (Distributed Control Systems)
PLC (Programmable Logic Controllers)
FUNCTIONAL BLOCK DIAGRAM
DIN0–DIN3
DOUT0–
DOUT3
EXC0
EXC1
EXC2
EXC3
ISET
AIN0
AIN1
AIN2
AIN3
GND SNSE
AGND
CJCIN
REFIN
REFOUT
EXC
CONTROL
LOGIC
SK
DI
DO
CE
DRDY
RESET
INPUT
MUX
PGA
CHARGE
BALANCE
A/D
PTAT
AD280
REF
XTAL
OSC
CHARGE
PUMP
XTAL XTAL2 XTAL1
OUT
CPE
DVDD
AVDD
ALO
CINT1
CINT2
PGAOUT
DGND
C1
C2
C3
GENERAL DESCRIPTION
The AD280 is a front-end integrated circuit for use in industrial
Ydata acquisition applications. It has been specifically designed
Rfor the stringent requirements of industrial applications, with
Afunctions such as protection/protectability and high normal-
INmode rejection. The AD280 can be configured to accept up to
Lfour mV/V/TC inputs, or up to two RTD inputs (in 2-, 3- or 4-
IM Awire connection modes).
L ICThe AD280 is not a stand-alone product, but is intended to be
E Nused with a companion microcontroller or microprocessor.
RDescriptions of appropriate algorithms and control routines for
P CH Athis device are contained in this data sheet, as well as on a
E Tseparate application note.
T AThe four primary input channels are designed for high input
Dimpedance for input signals up to ± 2.5 volts. Each also con-
The AD280 also offers four configurable excitation current
sources. Two of these sources can be configured to provide
excitation for RTDs, the amplitude of which can be set by an
external resistor. All four excitation sources can be set to pro-
vide +25 nA or –25 nA for use in detecting open inputs. The
excitation sources are separately pinned out to allow for external
protection devices to achieve very high normal-mode voltage
protection.
The input multiplexer feeds a programmable gain amplifier,
with binary gains from 1 to 128. The PGA drives a high resolu-
tion integrating A/D converter, which is software programmable
for integration time and can achieve usable resolution of up to
18 bits.
The AD280 features a serial interface, operable to 10 MHz, and
is compatible with a wide variety of microcontrollers and micro-
tains a programmable input attenuator for input ranges up to
processors. An onboard crystal oscillator and charge pump
± 10 volts at reduced input impedance. The inputs contain inter- circuit are provided. The charge pump circuit, requiring just
nal protection to allow for overload without affecting the accu- two external capacitors, provides the negative bias for this de-
racy or operability of adjacent inputs. The input multiplexer
vice and allows full operation from a single +5 V supply.
also features a ground sense input and a separate input (with
programmable excitation) for solid-state or thermistor tempera-
ture sensors for cold junction compensation of thermocouples.
An internal PTAT (Proportional to Absolute Temperature)
Four general purpose digital outputs and four general purpose
digital inputs are also provided; these may be used to implement
external functions that may be required in some applications.
sensor permits measurement of internal die temperature.
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices 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 Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1998
http://www.Datasheet4U.com

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