AD280

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 Measurement and Open Input Detection PGA with Programmable Gains from 1 to 128 High Resolution Integrating A/D Converter with Programmable 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 INPUT MUX GND SNSE AGND CJCIN REFIN REFOUT PTAT PGA CHARGE BALANCE A/D CONTROL LOGIC EXC SK DI DO CE DRDY RESET DVDD AVDD ALO CINT1 CINT2 PGAOUT DGND CHARGE PUMP C1 C2 C3 AD280 XTAL OSC REF XTAL XTAL2 XTAL1 OUT CPE GENERAL DESCRIPTION The AD280 is a front-end integrated circuit for use in industrial data acquisition applications. It has been specifically designed for the stringent requirements of industrial applications, with functions such as protection/protectability and high normalmode rejection. The AD280 can be configured to accept up to four mV/V/TC inputs, or up to two RTD inputs (in 2-, 3- or 4wire connection modes). The AD280 is not a stand-alone product, but is intended to be us...