SLYT818 November   2021 LM74701-Q1 , LM74721-Q1


  1. Introduction
  2. Automotive reverse-battery protection with ideal diode controllers
  3. TVS-less automotive reverse-polarity protection using ideal diode controllers
  4. TVS-less ideal diode: mode of operation and working principle
  5. External MOSFET
  6. Output Capacitor (COUT)
  7. TVS-less ideal diode controller EMC performance
  8. Conclusion
  9. Related Websites
  10. 10Important Notice


An automotive battery connects to multiple loads, including electronic control units (ECUs), relays and motors. Several system-level events, such as turning inductive loads on or off, can create voltage transients along battery supply lines. All reverse-polarity protection circuits must protect downstream electronic loads against these system level transient events.

Ideal diode reverse-battery protection typically comprises of an ideal diode controller, N-channel metal-oxide semiconductor field-effect transistor (MOSFET) and an input-side transient voltage suppression (TVS) diode to clamp transient events. This TVS diode consumes as much as 70% of the solution footprint, however, which is a challenge when designing dense ECU designs such as automotive driver assistance system (ADAS) cameras, USB hubs and display ECUs. Removing the input-side TVS saves system cost, reduces solution size and improves system reliability.

This article describes a TVS-less reverse-battery protection system design using an ideal diode controller, analyzing the system architecture for protection and electromagnetic compliance (EMC) in accordance with International Organization for Standardization (ISO) 7637-2 and 16750-2, and original equipment manufacturer (OEM) standards such as VW8000 (LV124) from German auto manufacturers.