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

Back-to-Back FET Driving Ideal Diode Controllers

Ideal Diode controllers such as LM7480-Q1 and LM7472x-Q1 can drive and control external back to back N-Channel MOSFETs to emulate an ideal diode rectifier with power path ON/OFF control, inrush current limiting and over voltage protection. Load disconnection during an overvoltage fault such as load-dump allows use of low voltage downstream components, enabling dense ECU designs such as ADAS camera, USB Hubs, LIDAR, and TCU. LM7480x-Q1 and LM7472x-Q1 have separate GATE controls for ideal diode control and ON/OFF control.

Automotive ECU designs powered from a vehicle battery need to be load dump tolerant. For the 12-V car battery based designs, the suppressed load dump peak specification is 35-V. For the system designs without the centralized load dump suppression, the surge voltage due to unsuppressed load dump can peak up to 101 V in 12-V systems and 202 V in 24-V battery based systems as per the ISO-16750-2 standard. Conventional solutions use several high-power TVS stacks (SMD sized) to clamp to a safe level (below the downstream absolute maximum voltages) during the unsuppressed load dump resulting in an increase in overall solution size and BoM cost of the front-end protection circuit.

The LM7480-Q1 controller with the external MOSFETs configured in common source topology as shown in Figure 6-7 below provides unsuppressed load dump protection.

GUID-4AF10950-545C-41CD-AC11-62888267D488-low.gifFigure 6-7 Application Circuit for 200V Unsuppressed Load Dump Protection