ZHCSO86B december   2022  – july 2023 LM74900-Q1 , LM74910-Q1

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 说明
  5. 4 Revision History
  6. 5 Device Comparison Table
  7. 6 Pin Configuration and Functions
  8. 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 开关特性
    7. 7.7 Typical Characteristics
  9. 8 Parameter Measurement Information
  10. 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 Overcurrent Protection (CS+, CS-, ILIM, IMON, TMR)
        1. 9.3.3.1 Pulse Overload Protection, Circuit Breaker
        2. 9.3.3.2 Overcurrent Protection With Latch-Off
        3. 9.3.3.3 Short Circuit Protection (ISCP)
        4. 9.3.3.4 Analog Current Monitor Output (IMON)
      4. 9.3.4 Undervoltage Protection, Overvoltage Protection, and Battery Voltage Sensing (UVLO, OV, SW)
      5. 9.3.5 Low IQ SLEEP Mode (SLEEP)
      6. 9.3.6 Ultra Low IQ Shutdown (EN)
  11. 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 Selection of Current Sense Resistor, RSNS
        6. 10.2.3.6 Selection of Scaling Resistor (RSET) and Short-Circuit Protection Setting Resistor (RSCP)
        7. 10.2.3.7 Overcurrent Limit (ILIM), Circuit Breaker Timer (TMR), and Current Monitoring Output (IMON) Selection
        8. 10.2.3.8 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 Addressing Automotive Input Reverse Battery Protection Topologies With LM749x0-Q1
    4. 10.4 Power Supply Recommendations
      1. 10.4.1 Transient Protection
      2. 10.4.2 TVS Selection for 12-V Battery Systems
    5. 10.5 Layout
      1. 10.5.1 Layout Guidelines
  12. 11Device and Documentation Support
    1. 11.1 接收文档更新通知
    2. 11.2 支持资源
    3. 11.3 Trademarks
    4. 11.4 静电放电警告
    5. 11.5 术语表
  13. 12Mechanical, Packaging, and Orderable Information

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10.2.3.8 Overvoltage Protection and Battery Monitor

Resistors R1, R2 and R3, R4 connected from SW pin to ground is used to program the undervoltage and overvoltage threshold. The resistor values required for setting the undervoltage threshold (VUVLO to 5.5 V) and overvoltage threshold (VOV to 37.0 V) a are calculated by solving

Equation 14. GUID-20221122-SS0I-5PWK-N2X1-5SNQTVH166VF-low.svg
Equation 15. GUID-20221122-SS0I-MFP9-JBKZ-KC9B5QNXWHXP-low.svg

For minimizing the input current drawn from the battery through resistors R1, R2, and R3; it is recommended to use higher value of resistance. Using high value resistors will add error in the calculations because the current through the resistors at higher value will become comparable to the leakage current into the OV pin. Maximum leakage current into the OV pin is 1 µA and choosing total ladder resistor < 120 kΩ ensures current through resistors is 100 times greater than leakage through OV pin.

Based on the device electrical characteristics, VUVLOF is 0.55 V. Select R1 = 100 kΩ. Solving Equation 14 gives R2 = 11.5 kΩ. Solving Equation 15 with R3 selected as 100 kΩ and VOVR = 0.6 V gives R4 = 1.65 kΩ as standard 1% resistor values closest to the calculated resistor values.

An optional capacitor CUV can be placed in parallel with R2 on UVLO resistor ladder in order to filter out any fast undervoltage transients on battery lines to avoid false UVLO trigger.

For this application example separate resistor ladder is selected to program overvoltage and undervoltage threshold. However common resistor ladder from SW pin to ground can also be used as shown in Figure 9-9.