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29 Industry 4.0 and Beyond | ADI Current input mode can support externally powered and loop- powered configurations. The 16-bit, sigma-delta ADC automatically measures the current through the sense resistor. The filterable sense pins (SENSEHF_x and SENSELF_x) are used for this purpose. Also, both types of current input functions have additional HART- compatibility mode with minimum 230Ω receive impedance ensured. Voltage input mode measures voltages with the ADC via one of the filtered ports (SENSELF_x) and ground sense. One can choose additional pull-down options against floating voltages. In voltage input mode, thermocouple readings can also be made because of a dedicated range setting in the ADC. The resistance measurement mode biases an external 2-wire RTD with a voltage derived from 2.5V bias. With the pull-up resistors to bias voltage, an accurate ratiometric measurement will be ensured. The low excitation current minimizes power dissipation, reducing the self-heating of the RTD. Digital input mode supports IEC 61131-2 Type I, Type II, and Type III devices. The thresholds are programmable via a dedicated register. Each channel has a dedicated general-purpose output (GPO) and user-programmable debounce filtering. Robustness and Diagnostics Because of the nature of industrial environments, the AD74413R is designed to be robust in noisy environments and can withstand overvoltage cases such as miswire and surge events. Because of on-chip line protectors, the screw terminals do not dump power into the integrated circuit when connected to a higher potential than the analog supply (AVDD) pin. Additional TVS diodes can be used to withstand high surges on the input/output terminals. Moreover, to increase the robustness of the AD74413R, a cyclic redundancy check (CRC) is built into the Serial Peripheral Interface (SPI) interface. Multiple diagnostic features ensure that the AD74413R functions correctly, and they provide a warning against most common failure scenarios. The on-chip diagnostics can monitor power- supply voltages, reference, die temperature (as alert or shutdown), and screw terminals. Diagnostics for the last factor can help for miswiring detections when a failure voltage occurs above AVDD or below 0V connected at the terminals. The external sense resistor further assists for diagnostics as well as for normal operation. For example, it provides short-circuit detection for voltage modes or helps regulate the current output modes. Users also can program their diagnostic routines to test connected sensor/ actuators because the AD74113R can force voltages or currents and read current or voltage responses from the field device. If an alert condition happens, the ALERT pin asserts. The ALERT_STATUS register determines the source of the failure. Companion Solutions One common application request is that I/O modules or programmable logic controllers (PLCs) feature microprocessor isolation or an electronic control unit from the bus side. The data and the power sources should all be galvanically separated. For both purposes, Analog Devices developed a dedicated power and data isolator for the SWIO family. The ADP1032 is a high- performance isolated power management unit (PMU) that comprises an isolated flyback with a buck regulator and data isolation channels. It is shown in Figure 2. Two regulators are phase-shifted for very low electromagnetic interference (EMI). The current mode flyback controller can supply 6V to 28V. It has undervoltage lockout (UVLO), overcurrent/ overvoltage protection, enable control, soft start, and slew rate control. Moreover, it has seven low-power digital isolation channels—four for SPI and three for general-purpose communication. Another typical need in I/O modules is driving relays or lamps. AD74413R has GPOs, which can also be programmed as special digital outputs (DOs). With an external PMOS and ADM1270 current-limiting controller, this pin can regulate a few hundred MULTIPLE DIAGNOSTIC FEATURES ENSURE THAT THE AD74413R FUNCTIONS CORRECTLY, AND THEY PROVIDE A WARNING AGAINST MOST COMMON FAILURE SCENARIOS. AD74413R Quad-Channel Software Configurable I/O LEARN MORE