The TPS2660 eFuse provides integrated protection to various system faults such as overcurrent, overvoltage, undervoltage, short-circuit, and reverse input polarity protection. Integrated reverse input polarity protection helps to protect electronic systems from reverse input supply due to miswiring. This application note describes methods to handle the fault of the TPS2660 by downstream circuits under a reverse input polarity condition.
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A PLC system is usually powered by an external 24-V DC power supply to provide power to the controller unit, backplane, and I/O modules within the PLC system. Input protection circuits are required to protect the PLC system from system faults such as overcurrent, overvoltage, and overload. Because the input supply connectors are screw type, there can always be a possibility of reverse connections at the input supply.
The TPS2660 eFuse protects downstream circuits from various systems faults including integrated protection to reverse input supply conditions (see the TPS2660 reference design). This device provides status monitor functions like fault indication and load current monitor, which is used by a downstream microcontroller unit (MCU) to take control decisions or a DC/DC converter to do power sequencing.
The FLTb signal of the TPS2660 combines power good indication along with system faults such as overload, overvoltage, undervoltage, and shutdown. This combination enables downstream loads like DC/DC converters to turn on heavy loads after power good indication. An application example where FLTb is directly connected to enable pin of a DC/DC converter is shown in Figure 1. During startup, FLTb is pulled low by the TPS2660 eFuse initially and is released after eFuse output is fully ON. Pullup resistor R4 and pulldown resistor R5 are used to scale down the pullup voltage and are chosen based on DC/DC converters' enable threshold voltage and its operating maximum rating.
Alternatively, the FLTb signal can be used by an external MCU to take control decisions under various systems fault conditions. An application example where FLTb is directly connected to the IO pin of the MCU and pulled up to the 5-V IO supply is shown in Figure 2.