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33 Industry 4.0 and Beyond | ADI Figure 3: AD5423 functional block diagram. (Source: Analog Devices Inc.) Table 1: High Voltage Transient Protection (Source: Analog Devices Inc.) The ADG5401F power supplies set the overvoltage fault threshold. If the voltage on the source pins (S or SFB) goes above the ADG5401F supply voltage, this is considered a fault, and the main switch channel and the secondary feedback channel will automatically open. When the switch channels are open during a fault, any large fault currents are prevented from flowing back into the DAC output and into the system power supply. With no large fault currents flowing during an overvoltage event, the system power dissipation is no longer constrained by the power dissipation during a fault, thereby reducing the design effort required for the system power supplies. The ADG5401F allows the system to remove current limiting resistors in the output signal path that can cause headroom issues in some applications. The ADG5401F (Figure 2) includes an integrated open-loop prevention switch. Suppose the V OUT /I OUT node is subjected to an overvoltage signal up to ±60V. In that case, the ADG5401F will implement its overvoltage protection mode, and the main channel and secondary feedback channel switches will open. At the same time, the internal open-loop prevention switch, an internal connection between D and DFB, will close. This open-loop prevention switch keeps the DAC output feedback loop intact and prevents the DAC from driving the output to the rails. To achieve protection from high voltage transients, such as IEC 61000-4-2 ESD, IEC 61000-4-4 electrical fast transient (EFT), and IEC 61000-4-5 surge, implement a circuit such as the one shown in Table 1 by using discrete resistors and a transient voltage suppression (TVS) device. Place the resistors inside the system's feedback loop so that the resistors do not add any error to the system output. Diagnostics The AD5423 (Figure 3) contains a 12-bit internal diagnostic ADC that provides diagnostic information on user-selectable inputs such as supplies, grounds, internal die temperatures, and references. Onboard diagnostic registers contain flags that indicate various fault situations, and a FAULT pin that triggers any fault. In voltage out mode, short-circuit detection is monitored, while in current out mode, open-circuit detection is monitored. The AD5423 also offers a cyclic redundancy check (CRC), which performs a check on the received data and triggers the FAULT pin if the current data package appears to be incorrect. Temperature monitoring is also available, which registers a fault if the die temperature exceeds a programmed limit. Conclusion Together, the AD5423 and the ADG5401F offer the precision and robustness required by industrial process applications. The AD5423's 16-bit I/V output provides the accurate control signals required for modern analog output modules, while the ADG5401F maintains that precision and provides robust protection against external stresses in harsh environments. 3 ADG5401F Fault Protection SPST Switch LEARN MORE AD5423 Current/Voltage Output DAC" LEARN MORE