SNOSDC2B September   2021  â€“ July 2022 LM74721-Q1

PRODUCTION DATA  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Switching Characteristics
    7. 6.7 Typical Characteristics
  7. Parameter Measurement Information
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Reverse Battery Protection (A, C, GATE)
        1. 8.3.1.1 Input TVS Less Operation: VDS Clamp
      2. 8.3.2 Load Disconnect Switch Control (PD)
      3. 8.3.3 Overvoltage Protection and Battery Voltage Sensing (VSNS, SW, OV)
      4. 8.3.4 Boost Regulator
    4. 8.4 Shutdown Mode
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical 12-V Reverse Battery Protection Application
      1. 9.2.1 Design Requirements for 12-V Battery Protection
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Boost Converter Components (C2, C3, L1)
        2. 9.2.2.2 Input and Output Capacitance
        3. 9.2.2.3 Hold-Up Capacitance
        4. 9.2.2.4 MOSFET Selection: Q1
      3. 9.2.3 Application Curves
    3. 9.3 What to Do and What Not to Do
  10. 10Power Supply Recommendations
    1. 10.1 Transient Protection
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Receiving Notification of Documentation Updates
    2. 12.2 Support Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

Layout Guidelines

  • Connect A, GATE and C pins of LM74721-Q1 close to the MOSFET SOURCE, GATE and DRAIN pins for the ideal diode stage, c.
  • Use thick and short traces for source and drain of the MOSFET to minimize resistive losses because the high current path of for this solution is through the MOSFET.
  • Have the PowerPAD™ integrated circuit package (exposed pad) of the MOSFET soldered directly to the top plane for best thermal performance. Other planes, such as the bottom side of the circuit board, can be used to increase heat sinking. Thermal considerations: during the VDS clamp operation, the MOSFET acts as an active clamp with pulse power dissipation.
  • Connect the GATE pin of the LM74721-Q1 to the MOSFET GATE with short trace.
  • Minimize the loops formed by capacitor across CAP pin and DRAIN of the FET and C3 to GND by placing these capacitors as close as possible. Keep the GND side of the C3 capacitor close to GND pin of LM74721-Q1. Boost converter switching currents flow into LX, CAP, GND pins and C3 (across DRAIN of the FET to GND).
  • Place transient suppression components like output Schottky close to C pin of LM74721-Q1.