SNOSD95C April   2020  – December 2020 LM7480-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Switching Characteristics
    7. 7.7 Typical Characteristics
  8. 8 Parameter Measurement Information
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Charge Pump
      2. 9.3.2 Dual Gate Control (DGATE, HGATE)
        1. 9.3.2.1 Reverse Battery Protection (A, C, DGATE)
        2. 9.3.2.2 Load Disconnect Switch Control (HGATE, OUT)
      3. 9.3.3 Overvoltage Protection and Battery Voltage Sensing (VSNS, SW, OV)
      4. 9.3.4 Low Iq Shutdown and Under Voltage Lockout (EN/UVLO)
    4. 9.4 Device Functional Modes
    5. 9.5 Application Examples
      1. 9.5.1 Redundant Supply OR-ing with Inrush Current Limiting, Overvoltage Protection and ON/OFF Control
      2. 9.5.2 Ideal Diode with Unsuppressed Load Dump Protection
  10. 10Applications and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical 12-V Reverse Battery Protection Application
      1. 10.2.1 Design Requirements for 12-V Battery Protection
      2. 10.2.2 Automotive Reverse Battery Protection
        1. 10.2.2.1 Input Transient Protection: ISO 7637-2 Pulse 1
        2. 10.2.2.2 AC Super Imposed Input Rectification: ISO 16750-2 and LV124 E-06
        3. 10.2.2.3 Input Micro-Short Protection: LV124 E-10
      3. 10.2.3 Detailed Design Procedure
        1. 10.2.3.1 Design Considerations
        2. 10.2.3.2 Charge Pump Capacitance VCAP
        3. 10.2.3.3 Input and Output Capacitance
        4. 10.2.3.4 Hold-Up Capacitance
        5. 10.2.3.5 Overvoltage Protection and Battery Monitor
      4. 10.2.4 MOSFET Selection: Blocking MOSFET Q1
      5. 10.2.5 MOSFET Selection: Hot-Swap MOSFET Q2
      6. 10.2.6 TVS Selection
      7. 10.2.7 Application Curves
    3. 10.3 200-V Unsuppressed Load Dump Protection Application
      1. 10.3.1 Design Requirements for 200-V Unsuppressed Load Dump Protection
      2. 10.3.2 Design Procedure
        1. 10.3.2.1 Charge Pump Capacitance VCAP
        2. 10.3.2.2 Input and output capacitance
        3. 10.3.2.3 VS Capacitance, Resistor and Zener Clamp
        4. 10.3.2.4 Overvoltage Protection and Output Clamp
        5. 10.3.2.5 MOSFET Q1 Selection
        6. 10.3.2.6 Input TVS Selection
        7. 10.3.2.7 MOSFET Q2 Selection
      3. 10.3.3 Application Curves
    4. 10.4 Do's and Don'ts
  11. 11Power Supply Recommendations
    1. 11.1 Transient Protection
    2. 11.2 TVS Selection for 12-V Battery Systems
    3. 11.3 TVS Selection for 24-V Battery Systems
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Receiving Notification of Documentation Updates
    2. 13.2 Support Resources
    3. 13.3 Trademarks
    4. 13.4 Electrostatic Discharge Caution
    5. 13.5 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

10.2.2.2 AC Super Imposed Input Rectification: ISO 16750-2 and LV124 E-06

Alternators are used to power the automotive electrical system and charge the battery during normal runtime of the vehicle. Rectified alternator output contains residual AC ripple voltage superimposed on the DC battery voltage due to various reasons which includes engine speed variation, regulator duty cycle with field switching ON/OFF and electrical load variations. On a 12-V battery supply, alternator output voltage is regulated by a voltage regulator between 14.5 V to 12.5 V by controlling the field current of alternator's rotor. All electronic modules are tested for proper operation with superimposed AC ripple on the DC battery voltage. AC super imposed test specified in ISO 16750-2 and LV124 E-06 requires AC ripple of 2-V Peak-Peak on a 13.5-V DC battery voltage, swept from 15 Hz to 30 KHz. LM7480x-Q1 rectifies the AC superimposed voltage by turning the MOSFET Q1 OFF quickly to cut-off reverse current and turning the MOSFET Q1 ON quickly during forward conduction. Active rectification of 2-V peak-peak 5-KHz AC input by LM7480x-Q1 is shown in Figure 10-3. Fast turn off and quick turn ON of the MOSFET reduces power dissipation in the MOSFET Q1 and active rectification reduces power dissipation in the output hold-up capacitor's ESR by half. Active rectification of 2-V peak-peak 30-KHz AC input is shown in Figure 10-4.

GUID-5EB42EB8-FFC8-42AE-87CF-31A0011ECC8D-low.pngFigure 10-3 AC Super Imposed Test - 2-V Peak-Peak 5 KHz
GUID-FE642D5C-2B9C-43ED-B8BB-350F12D34703-low.pngFigure 10-4 AC Super Imposed Test - 2-V Peak-Peak 30 KHz