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Maxim > Design Support > Technical Documents > Sub-System Boards > APP 5562

isolated power and data, industrial automation, 4-20mA, current loop, PLC, medical

SUB-SYSTEM BOARD 5562

Campbell (MAXREFDES4#): 16-Bit High-Accuracy 4-

20mA Input Isolated Analog Front End (AFE)

Jan 16, 2013

Abstract: This document explains how the Campbell (MAXREFDES4#) subsystem reference design meets the

higher resolution and isolation needs of industrial control and industrial automation applications. Hardware and

firmware design files as well as FFTs and histograms from lab measurements are provided.

Introduction

In industrial control and industrial

automation applications, high-resolution

data converters are often required.

Although today's field programmable gate

arrays (FPGAs) and microcontrollers may

integrate analog-to-digital converters

(ADCs), in many cases, the resolution is

not high enough and isolation is lacking.

The Campbell (MAXREFDES4#) subsystem reference design is a 16-bit high-accuracy industrial analog front

end (AFE) that accepts a 4–20mA current loop or a 0.2V to 4.096V voltage input signal, and features isolated

power and data—all integrated into a small form factor. The Campbell design integrates a precision low-noise

buffer (MAX44250), a high-accuracy ADC (MAX11100), an ultra-high-precision 4.096V voltage reference

This AFE solution can be used in any application that needs high-accuracy analog-to-digital conversion, but it is

mainly targeted for industrial sensors, industrial automation, process control, programmable logic controllers

(PLCs), and medical applications.

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