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
Figure 7-1 shows a typical 12 V reverse battery protection circuit using the LM74700-Q1. The MOSFET body diode is oriented correctly to block reverse current flowing back in to the battery when the LM74700 is turned off. When battery power is applied through anode, body diode of the MOSFET initially conducts before the MOSFET is turned on. During startup, when the anode voltage reaches POR threshold, the internal charge pump turns on and starts to drive the gate of MOSFET higher than the anode (source of MOSFET), thereby turning on the MOSFET. If the battery is installed with reverse polarity or wired incorrectly during maintenance or repair, the MOSFET is off already and body diode of the MOSFET blocks reverse current. This prevents negative voltage from appearing on the output and protects the downstream circuit from damage.