Campbell (MAXREFDES4#): 16-bit, high-accuracy 4-20mA input isolated analog front end (AFE)

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In industrial control and industrial automation applications, high-resolution data converters are often required. Although today's field programmable gate arrays ( FPGAs ) and microcontrollers have integrated analog-to-digital converters (ADCs) , in most cases the resolution of the ADCs is not high and they lack sufficient isolation. Campbell subsystem reference design (MAXREFDES4#) is a 16-bit high-precision industrial analog front end (AFE) that can receive a 4-20mA current loop or a voltage input signal from 0.2V to 4.096V, providing isolated power supply and complete data acquisition in a small form factor design. Campbell designs include a high-precision low-noise buffer ( MAX44250 ), a high-precision ADC ( MAX11100 ), an ultra-precision 4.096V voltage reference ( MAX6126 ), a 600VRMS data isolator ( MAX14850 ), and an isolated 5V supply ( MAX256 / MAX1659 ). This AFE solution can be used in any high-precision analog-to-digital conversion application, but is mainly targeted at industrial sensors, industrial automation, process control, programmable logic controllers (PLC) , and medical applications .

Figure 1. Campbell subsystem design block diagram