MAXREFDES185

Description

The MAXREFDES185# is a complete, universal input-output (UIO) reference design with Safety Monitoring of all IO signals. It demonstrates a fully software-configurable UIO module (analog IO + digital IO on a common pin) using the MAX22000 industrial configurable analog IO device and the MAX14914A low-leakage digital IO device. The industry-standard four-way PCB terminal block includes support for temperature measurement using a resistance temperature detector (RTD) or a thermocouple, including built-in cold-junction compensation for thermocouple measurements.

The MAXREFDES185#, built in an industrial form-factor (Figure 1), uses an industry-standard Pmod™ connector with a 3.3V power supply. A barrel connector supports an external 24V DC input, from which higher voltage HVDD and HVSS rails are generated. The complete reference design fits on a 75mm x 20mm printed circuit board (PCB).

The configurable modes include an analog voltage input (0 to +10V), an analog current input (0 to +20mA), an analog voltage output (0 to +10V), and an analog current output (0 to +20mA), as well as a digital input (IEC 61131-2 Types 1, 2 or 3) and a digital output (0-24V, up to 1.3A) across the UIO and GND terminals. The accuracy is as good as 0.1% FSR over a ±50°C temperature variation. The other two terminals can be configured to measure temperature using a standard device such as a PT100 or PT1000 RTD.

The MAX14914A is a pin-controlled low-DOI-leakage version of the MAX14914, designed to work seamlessly with the MAX22000 for universal IO (UIO) applications. The MAX14914A features full IEC 61131-2 compliance in both DO and DI modes of operation. The MAX14914A provides monitoring of the DOI output in both high-side and push-pull modes and the corresponding logic level can be seen through the inversed DOI_LVL logic output.

The MAX22005 is a 12-channel industrial-grade analog-input IC that can operate in voltage or current mode. For this design, the MAX22005 has channels configured to monitor all the analog signals from the MAX22000 no matter if it is operating as an analog input or analog output (voltage or current mode) in addition to monitoring the temperature measurement sensor.

Features & Benefits

Features

• Universal Analog IO
• Safety Monitoring
• IEC 61131-2 Compliant
• Power Tracking

Application

• Industrial Automation
• Universal Input Output Modules
• PLC and DCS Systems
• Smart Sensors and Actuators