SNOSDF6 October   2023 LM74930-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Revision History
  6. 5 Pin Configuration and Functions
  7. 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
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Charge Pump
      2. 7.3.2  Dual Gate Control (DGATE, HGATE)
        1. 7.3.2.1 Load Disconnect Switch Control (HGATE, OUT)
        2. 7.3.2.2 Reverse Battery Protection (A, C, DGATE)
      3. 7.3.3  Overcurrent Protection (CS+, CS-, ILIM, IMON, TMR)
      4. 7.3.4  Overcurrent Protection with Circuit Breaker (ILIM, TMR)
      5. 7.3.5  Overcurrent Protection With Latch-Off
      6. 7.3.6  Short-Circuit Protection (ISCP)
        1. 7.3.6.1 Device Wake-Up With Output Short-Circuit Condition
      7. 7.3.7  Analog Current Monitor Output (IMON)
      8. 7.3.8  Overvoltage and Undervoltage Protection (OV, UVLO, OVCLAMP)
      9. 7.3.9  Disabling Reverse Current Blocking Functionality (MODE)
      10. 7.3.10 Device Functional Modes
        1. 7.3.10.1 Low Quiescent Current Shutdown Mode (EN)
  9. 8 Applications and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application: 200-V Unsuppressed Load Dump Protection Application
      1. 8.2.1 Design Requirements for 200-V Unsuppressed Load Dump Protection
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1  VS Capacitance, Resistor R1 and Zener Clamp (DZ)
        2. 8.2.2.2  Charge Pump Capacitance VCAP
        3. 8.2.2.3  Input and Output Capacitance
        4. 8.2.2.4  Overvoltage and Undervoltage Protection Component Selection
        5. 8.2.2.5  Selection of Scaling Resistor (RSET) and Short-Circuit Protection Setting Resistor (RSCP)
        6. 8.2.2.6  Overcurrent Limit (ILIM), Circuit Breaker Timer (TMR), and Current Monitoring Output (IMON) Selection
        7. 8.2.2.7  Selection of Current Sense Resistor, RSNS
        8. 8.2.2.8  Hold-Up Capacitance
        9. 8.2.2.9  MOSFET Q1 Selection
        10. 8.2.2.10 MOSFET Q2 Selection
        11. 8.2.2.11 Input TVS Selection
      3. 8.2.3 Application Curves
    3. 8.3 Best Design Practices
    4. 8.4 Power Supply Recommendations
      1. 8.4.1 Transient Protection
      2. 8.4.2 TVS Selection for 12-V Battery Systems
      3. 8.4.3 TVS Selection for 24-V Battery Systems
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
      2. 8.5.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Receiving Notification of Documentation Updates
    2. 9.2 Support Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.2.7 Selection of Current Sense Resistor, RSNS

LM74930-Q1 has integrated short-circuit detection comparator with default sense threshold of 20 mV. For this application, short-circuit limit is set to 20 A. The sense resistor value based on short circuit comparator can be calculated by Equation 18.

Equation 18. RSENSE=VSENSEISCP

Select a 1-mΩ resistor with 1% tolerance to set short-circuit protection limit of 20 A.

Selecting the lower current sense resistor value helps with lower power dissipation, however it has comparatively smaller drop across current sense resistor at full load. If higher drop across current sense resistor is desired for better current monitoring accuracy, device short-circuit limit can be increased using RISCP resistor. Please refer to device design calculator on LM74930-Q1 product page.