Maxim > Design Support > Technical Documents > Subsystem Boards > APP 5563 Keywords: Fresno, MAXREFDES11, subsystem reference design, analog front end, AFE, industrial sensors, isolated power and data, industrial automation, PLC, medical SUBSYSTEM BOARD 5563 Fresno (MAXREFDES11 ): 16-Bit High-Accuracy 0 to 10V Input Isolated Analog Front End (AFE) Jan 19, 2013 Abstract: This document explains how the Fresno (MAXREFDES11 ) subsystem reference design meets the higher resolution and higher voltage 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 Low resolution and low input voltage analog-to-digital converters (ADCs) are integrated in many of today s field programmable gate arrays (FPGAs) and microcontrollers. However, they fall short on meeting the needs of industrial control More detailed image (JPG) and industrial automation applications that require higher resolutions and higher input voltages. The Fresno (MAXREFDES11 ) subsystem reference design is a 16-bit high-accuracy industrial analog front end (AFE) that accepts 0 to 10V signals and features isolated power and dataall integrated into a small form factor. The Fresno design integrates an ultra-precision low-noise buffer (MAX44250) a highly accurate ADC (MAX11100) an ultra-high-precision 4.096V voltage reference (MAX6126) 600V data RMS isolation (MAX14850) and isolated/regulated +5.5V, +5V, and -3V power rails (MAX256/MAX1659/MAX1735). 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. Page 1 of 11Figure 1. The Fresno subsystem design block diagram. Features Applications High accuracy Industrial sensors 0 to 10V input range Process control Isolated power and data Industrial automation Small printed circuit board (PCB) area PLC Device drivers Medical Example C source code Pmod -compatible form factor Detailed Description of Hardware The Pmod specification allows for both 3.3V and 5V modules as well as various pin assignments. This module is designed only for a supply voltage of 3.3V and uses the SPI pin assignments as illustrated on the right. The power requirements are shown in Table 1. The currently supported platforms and ports are shown in Table 2. Page 2 of 11