MAXREFDES67#

MAXREFDES67# Datasheet

MAXREFDES67# UNIVERSAL INPUT MICRO PLC

Part	Datasheet
MAXREFDES67#	MAXREFDES67# (pdf)

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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 bits with temperature error as low as 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-theRails 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. • 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 • Board and sensor calibration • Micro PLC form factor • Device drivers • Example C source code • Test data Competitive Advantages • Flexibility • Accelerated time to market • Ease of use • Industrial control and automation • Process control • PLC MAXREFDES67# System Board Enlarge+ MAXREFDES67# Reference Design Block Diagram Enlarge+ MAXREFDES67# Circuit Block Diagram 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 marks a sea change in industrial architectures, characterized by distributed, intelligent control systems. Industry 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 ultrasmall micro PLC form factor marries this indispensible element with the key concepts of Industry 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 MAXREFDES67# System Board Enlarge+ Figure The MAXREFDES67# reference design block diagram. Figure The MAXREFDES67# reference design input circuit block diagram. Detailed Description of Hardware The power requirement is shown in Table Table Power Requirement for the MAXREFDES67# Reference Design Power Type On-board isolated power Input Voltage V 24 Input Current mA, typ 20 Note STM32 and FTDI are powered by USB separately The MAXREFDES67# reference design is a universal analog input card with isolated power and data. It supports voltage, current, RTD PT100 and PT1000 , and thermocouple K type inputs as shown in the configuration diagram of Figure The input circuitry utilizes the digitally controlled analog switches MAX14759 and MAX14763 to make the appropriate electrical connections for different types of input signals, thus relieving the need for any additional jumpers on the terminal block. The dual beyond-the-rail op amp MAX44267 buffers the input signal. The quad low-noise low-power op amp MAX44245 attenuates and also adds 1.5V offset to the input signals. The offset voltage is needed because the ADC is set up to measure positive signals. This setup eliminates the need for a negative voltage reference and voltage supply. The attenuation is for the -12V to +12V voltage signal, and the attenuation is for the current, RTD, and TC input signals. The attenuated signal from the output of the MAX44245 connects to channel 0 of the ADC, and the signal with attenuation connects to channel 1 of the ADC. The STM32 controller determines which channel to read depending on the input selected. The MAX11254 is a highly integrated, 24-bit, 6-channel ADC with an integrated analog input PGA. The ADC’s reference input is driven by an ultra-high-precision voltage reference, the MAX6126, with initial accuracy and a 3ppm/°C maximum temperature coefficient tempco . An onboard digital thermometer MAX31723 is placed close to the input terminal block to determine the temperature at the input port and provide the cold junction temperature of the thermocouple. The MAXREFDES67# uses the ultra-efficient MAX17498C to generate the isolated +17.5V and +7.5V rails from a 24V supply. The two MAX17651 devices provide post-regulated +15V, +3.6V rails. The MAX14930/MAX14932 digital data isolators provide data isolation. The combined power and data isolation achieved is 300VRMS working voltage in pollution degree 2 environment based on material class IIIb per IEC The MAX17552 step-down DC-DC converter converts the +5V supply from the USB to +3.3V and powers the STM32 microcontroller and FTDI USB-UART bridge. A PT100 RTD and a K-type thermocouple are included in the MAXREFDES67# package. For the thermocouple, the yellow wire is the positive signal and the red wire is the negative signal. Figure The MAXREFDES67# input configurations. Detailed Description of Firmware The MAXREFDES67# uses the on-board STM32F4 microcontroller to control the analog switch, read temperature from the digital thermometer, communicate with the ADC, and save the ADC samples in the on-chip SRAM. Users read the sampled data through a terminal program, allowing analysis on any third-party software. Users can also perform system and sensor calibrations through a terminal program. The red color VREF connector on the board is provided for RTD input calibration. The simple process flow is shown in Figure The firmware is written in C using the Keil µVision5 tool. Figure The MAXREFDES67# firmware flowchart. The firmware accepts calibration and sampling commands, and is capable of downloading blocks of sampled data to a standard terminal program via a virtual COM port. The complete source code is provided to speed up customer development. Code documentation can be found in the corresponding firmware platform files. Quick Start Required equipment: • PC with a USB port • MAXREFDES67# board • 24V power supply, provided • PT100 RTD, provided Procedure

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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 bits with temperature error as low as 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-theRails 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.
• 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
• Board and sensor calibration
• Micro PLC form factor
• Device drivers
• Example C source code
• Test data

Competitive Advantages
• Flexibility
• Accelerated time to market
• Ease of use
• Industrial control and automation
• Process control
• PLC MAXREFDES67# System Board

Enlarge+ MAXREFDES67# Reference Design Block Diagram

Enlarge+ MAXREFDES67# Circuit Block Diagram

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 marks a sea change in industrial architectures, characterized by distributed, intelligent control systems. Industry 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 ultrasmall micro PLC form factor marries this indispensible element with the key concepts of Industry 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

MAXREFDES67# System Board

Enlarge+ Figure The MAXREFDES67# reference design block diagram.

Figure The MAXREFDES67# reference design input circuit block diagram.

Detailed Description of Hardware

The power requirement is shown in Table

Table Power Requirement for the MAXREFDES67# Reference Design

Power Type On-board isolated power

Input Voltage V 24

Input Current mA, typ 20

Note STM32 and FTDI are powered by USB separately

The MAXREFDES67# reference design is a universal analog input card with isolated power and data. It supports voltage, current, RTD PT100 and PT1000 , and thermocouple K type inputs as shown in the configuration diagram of Figure The input circuitry utilizes the digitally controlled analog switches MAX14759 and MAX14763 to make the appropriate electrical connections for different types of input signals, thus relieving the need for any additional jumpers on the terminal block. The dual beyond-the-rail op amp MAX44267 buffers the input signal. The quad low-noise low-power op amp MAX44245 attenuates and also adds 1.5V offset to the input signals. The offset voltage is needed because the ADC is set up to measure positive signals. This setup eliminates the need for a negative voltage reference and voltage supply. The attenuation is for the -12V to +12V voltage signal, and the attenuation is for the current, RTD, and TC input signals. The attenuated signal from the output of the MAX44245 connects to channel 0 of the ADC, and the signal with attenuation connects to channel 1 of the ADC. The STM32 controller determines which channel to read depending on the input selected. The MAX11254 is a highly integrated, 24-bit, 6-channel ADC with an integrated analog input PGA. The ADC’s reference input is driven by an ultra-high-precision voltage reference, the MAX6126,
with initial accuracy and a 3ppm/°C maximum temperature coefficient tempco . An onboard digital thermometer MAX31723 is placed close to the input terminal block to determine the temperature at the input port and provide the cold junction temperature of the thermocouple. The MAXREFDES67# uses the ultra-efficient MAX17498C to generate the isolated +17.5V and +7.5V rails from a 24V supply. The two MAX17651 devices provide post-regulated +15V, +3.6V rails. The MAX14930/MAX14932 digital data isolators provide data isolation. The combined power and data isolation achieved is 300VRMS working voltage in pollution degree 2 environment based on material class IIIb per IEC The MAX17552 step-down DC-DC converter converts the +5V supply from the USB to +3.3V and powers the STM32 microcontroller and FTDI USB-UART bridge. A PT100 RTD and a K-type thermocouple are included in the MAXREFDES67# package. For the thermocouple, the yellow wire is the positive signal and the red wire is the negative signal.

Figure The MAXREFDES67# input configurations.

Detailed Description of Firmware

The MAXREFDES67# uses the on-board STM32F4 microcontroller to control the analog switch, read temperature from the digital thermometer, communicate with the ADC, and save the ADC samples in the on-chip SRAM. Users read the sampled data through a terminal program, allowing analysis on any third-party software. Users can also perform system and sensor calibrations through a terminal program. The red color VREF connector on the board is provided for RTD input calibration. The simple process flow is shown in Figure The firmware is written in C using the Keil µVision5 tool.

Figure The MAXREFDES67# firmware flowchart.

The firmware accepts calibration and sampling commands, and is capable of downloading blocks of sampled data to a standard terminal program via a virtual COM port. The complete source code is provided to speed up customer development. Code documentation can be found in the corresponding firmware platform files.

Quick Start

Required equipment:
• PC with a USB port
• MAXREFDES67# board
• 24V power supply, provided
• PT100 RTD, provided

Procedure

Notice: we do not provide any warranties that information, datasheets, application notes, circuit diagrams, or software stored on this website are up-to-date or error free. The archived MAXREFDES67# Datasheet file may be downloaded here without warranties.

Datasheet ID: MAXREFDES67# 647479