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


  1.   Trademarks
  2. Introduction
  3. Reverse Battery Protection
    1. 2.1 Reverse Battery Protection with Schottky Diode
  4. ORing Power Supplies
  5. Reverse Battery Protection using MOSFETs
    1. 4.1 Reverse Battery Protection using P-Channel MOSFET
    2. 4.2 Input Short or supply interruption
    3. 4.3 Diode Rectification During Line Disturbance
    4. 4.4 Reverse Battery Protection using N-Channel MOSFET
  6. Reverse Polarity Protection vs Reverse Current Blocking
    1. 5.1 Reverse Polarity Protection Controller vs. Ideal Diode Controller
    2. 5.2 Performance Comparison of P-Channel and Reverse Polarity Protection Controller Based Solution
  7. What is an Ideal Diode Controller?
    1. 6.1 Linear Regulation Control Vs Hysteretic ON/OFF Control
    2. 6.2 Low Forward Conduction Loss
    3. 6.3 Fast Reverse Recovery
    4. 6.4 Very Low Shutdown Current
    5. 6.5 Fast Load Transient Response
    6. 6.6 Additional Features in Ideal Diode Controllers
      1. 6.6.1 Back-to-Back FET Driving Ideal Diode Controllers
      2. 6.6.2 Very Low Quiescent Current
      3. 6.6.3 TVSless Operation
  8. Automotive Transient protection with Ideal Diode Controllers
    1. 7.1 LM74700-Q1 with N-Channel MOSFET
    2. 7.2 Static Reverse Polarity
    3. 7.3 Dynamic Reverse Polarity
    4. 7.4 Input Micro-Short
    5. 7.5 Diode Rectification of Supply Line disturbance
  9. ORing Power Supplies with Ideal Diode Controllers
  10. Integrated Ideal Diode Solution
  11. 10Summary
  12. 11References
  13. 12Revision History

Reverse Battery Protection

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.

GUID-1AC447F7-8FED-4031-8452-C96A272D4C7A-low.gifFigure 2-1 Reversed Connected Battery: Damage to MCU or DC/DC converter
GUID-5C0AE182-BB33-412B-80B6-A294623EA927-low.gifFigure 2-2 Reversed Connected Battery: Damage to Polarized Capacitors

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.