3 TVS-less automotive reverse-polarity protection using ideal diode controllers

TI’s LM74701-Q1 and LM74721-Q1 ideal diode controller integrates a unique feature to achieve a TVS-less input reverse-polarity protection solution. The device operates an external MOSFET as an active clamp element to dissipate the energy of negative transient event described by ISO 7637-2 Pulse 1. During a ISO 7637-2 Pulse 1 transient event, where there is no output voltage holdup requirement, these devices regulate the voltage across the external FET to a pre-defined threshold by monitoring the voltage drop across the external MOSFET’s drain-to-source (VDS) pins and enabling the gate drive. The reverse current flows from the output capacitor back to the input source, and transient pulse energy dissipates across the MOSFET.

Figure 3-1 shows the ISO 7637-2 Pulse 1 operation differences between a standard ideal diode and a TVS-less ideal diode solution.