SLVAE57B February 2021 – October 2021 LM5050-1 , LM5050-2 , LM5051 , LM66100 , LM74202-Q1 , LM74500-Q1 , LM74610-Q1 , LM74700-Q1 , LM74720-Q1 , LM74721-Q1 , LM74722-Q1 , LM7480-Q1 , LM7481-Q1 , LM76202-Q1 , SM74611 , TPS2410 , TPS2411 , TPS2412 , TPS2413 , TPS2419
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This application report discusses traditional methods using schottky diodes or P-Channel MOSFETs to provide front-end input protection such as reverse battery protection, reverse current blocking, and protection during input micro-shorts. Next, the report discusses ORing power supplies to provide supply redundancy and increase power capacity. The report discusses in detail the drawbacks of existing methods and the benefits of using TI's Ideal Diode Controllers for input protection and ORing applications.
In front-end power system designs, modules, or subsystems that directly run from battery power require protection from reverse battery connection or dynamic reverse polarity conditions during a inductive load disconnect from the battery. During maintenance of car battery or jump start of the vehicle, the battery can be connected in reverse polarity during reinstallation and can cause damage to the connected subsystems, circuits, and components. Figure 2-1 shows a battery that is reverse connected. When this occurs, huge current flows through ESD diode of micro-controllers, DC/DC converters, or other integrated circuits cause severe damage to battery connected subsystems. Polarized components such as electrolytic capacitors can be damaged by reverse connected battery as shown in Figure 2-2.
Passenger cars and commercial vehicles are fitted with 12-V or 24-V battery and the subsystems powered through the 12-V or 24-V battery are subjected to various electrical transients on their power supply lines during the operating life time of the vehicle. Automotive EMC testing standards such as ISO 7637-2 and ISO 16750-2, among others, specify electrical transients, test methods, and classify functional performance for immunity against the specified transients. Reverse battery protection solution is expected to protect the electrical subsystems from the transients and meet the functional performance status required for each subsystem. Traditionally, schottky diodes are used to provide reverse battery protection and prevent damage to battery connected subsystems.