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

8.2.2.6 Overcurrent Limit (ILIM), Circuit Breaker Timer (TMR), and Current Monitoring Output (IMON) Selection

Programming the Overcurrent Protection Threshold – RILIM Selection

The RILIM sets the overcurrent protection (circuit breaker detection) threshold, whose value can be calculated using Equation 15.

Equation 15. RILIM=12×RSETILIM×RSENSE

To set 5 A as overcurrent protection threshold, RILIM value is calculated to be 120 kΩ. Choose available standard value: 120 kΩ, 1%.

Programming the Circuit Breaker Time – CTMR Selection

For the design example under discussion, overcurrent transients are allowed for 1-ms duration. This blanking interval, TOC (or circuit breaker interval, TCB) can be set by selecting appropriate capacitor CTMR from TMR pin to ground. The value of CTMR can be calculated using Equation 16.

Equation 16. TOC=1.2×CTMR82.3 μA

CTMR value of 68 nF, 10% is selected to allow circuit breaker duration of close to 1-ms.

Programming Current Monitoring Output – RIMON Selection

Voltage at IMON pin VIMON is proportional to the output load current. This can be connected to an ADC of the downstream system for monitoring the operating condition and health of the system. The RIMON must be selected based on the maximum load current and the input voltage range of the ADC used. RIMON is set using Equation 17.

Equation 17. VIMON=0.9×VSENSE×RIMONRSET

For this application example, VIMON is selected to be 2.7 V at full load current of 5 A. RIMON value of 30.1 kΩ, 1% is selected.