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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10.2.3.7 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 11.

Equation 11. GUID-20221120-SS0I-4SH5-HCDR-FJW4SMJ9L5XZ-low.svg

To set 10 A as overcurrent protection threshold, RILIM value is calculated to be 60 kΩ. Choose the closest available standard value: 60 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 to set 1 ms for TOC can be calculated using Equation 12.

Equation 12. GUID-20230608-SS0I-DTT1-8RG8-SNJQXSTQ0QLK-low.svg

Choose closest available standard value: 68 nF, 10%.

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 13.

Equation 13. GUID-20221120-SS0I-QS38-DQZJ-GMFJPGWRWF9G-low.svg

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.