System Board 6185
MAXREFDES67#: UNIVERSAL INPUT MICRO PLC
Overview
The MAXREFDES67# reference design is a complete universal analog input for industrial
applications. This unique 24-bit front-end accepts bipolar voltage and current, resistance
temperature detector (RTD) and thermocouple (TC) inputs. Built in Maxim Integrated’s
ultra-small Micro PLC form factor, the MAXREFDES67# performs with a effective
resolution up to 22.3 bits with temperature error as low as ±0.1% across a range of -40°C
to 150°C.
To enhance ease of use, the innovative system architecture switches all signals on board,
meaning that the connector requires no jumpers or additional connections, regardless of
the type of connection. In addition, the system features Maxim Integrated’s Beyond-the-
Rails feature in all signal-chain elements. Beyond the Rails reduces the need for large
power supplies, allowing each element to accept large input voltages while running from a
low-voltage power rail.
The board features a micro USB connector for quick connection to a PC for evaluation. In
addition, the board requires a 24V power supply, from a power supply or from the included
AC/DC wall adapter. Refer to the Details tab for more information and performance data.
Design files and firmware can be downloaded from the Design Resources tab.
Features
•
•
•
•
•
•
•
High accuracy
-10V to +10V ±20% voltage inputs
-20mA to +20mA ±20% current inputs
RTD and TC tested temperature range (-40°C to +150°C)
Software-controlled input type
24V input protection
Isolated power and data
System Board 6185
MAXREFDES67#: UNIVERSAL INPUT MICRO PLC
Details
Introduction
The universal analog input is the most functional, ubiquitous element in factory automation. The
ability to flexibly measure current, voltage, RTDs, and TCs makes the universal input an
indispensable piece in any installation. In parallel, Industry 4.0 marks a sea change in industrial
architectures, characterized by distributed, intelligent control systems. Industry 4.0 allows for
highly configurable, highly modular factories, which accept an ever increasing number of sensor
inputs while operating at a higher output than ever before. Building a universal input in the ultra-
small micro PLC form factor marries this indispensible element with the key concepts of Industry
4.0. Furthermore, this board requires a number of highly integrated analog and mixed signal
products providing high performance with ultra-low power consumption in an ultra-small package.
MAXREFDES67# is Maxim’s micro PLC, universal analog input card.
The MAXREFDES67# features an analog input that supports voltage, current, RTD, and
thermocouple input signals with isolated power and data. The MAXREFDES67# design integrates
two beyond-the-rail SPST analog switches (MAX14759), two beyond-the-rail SPDT analog
switches (MAX14763), a dual beyond-the-rail buffer (MAX44267), a quad low-noise low-power op
amp (MAX44245), a digital thermometer (MAX31723), a 24-bit 6-channel ADC (MAX11254) with
internal PGA buffers, an ultra-high-precision 4.096V voltage reference (MAX6126), a low-power
precision op amp (MAX44244), 2.75kVRMS data isolation (MAX14930 and MAX14932), a
STM32F4 microcontroller, a FTDI USB-UART bridge, a high-efficiency DC-DC converter
(MAX17552), and isolated/regulated +15V and +3.6V power rails (MAX17498C and two
MAX17651s). The entire system typically operates at less than 500mW and fits into a space
roughly the size of a credit card. While targeted for industrial, micro PLC applications, the
MAXREFDES67# may be used in any application that requires high-accuracy analog-to-digital
conversion. A block diagram of the system is shown in
Figure 1
and
Figure 2.
MAXREFDES67# System Board
FPGA/CPLD
京公网安备 11010802033920号
EEWORLD
