JAJU793 October   2020

 

  1.   概要
  2.   リソース
  3.   アプリケーション
  4.   特長
  5.   5
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Ideal Diode Design Overview
      2. 2.2.2 Current Sensing Amplifier Design Overview
      3. 2.2.3 OR Gate Design Overview
      4. 2.2.4 MOSFET Selection
        1. 2.2.4.1 Blocking MOSFET
        2. 2.2.4.2 Hot-Swap MOSFET
      5. 2.2.5 TVS Input Diode Selection
      6. 2.2.6 Inrush Current
    3. 2.3 Highlighted Products
      1. 2.3.1 LM74810-Q1
      2. 2.3.2 INA302-Q1
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
      1. 3.1.1 Getting Started
      2. 3.1.2 Testing and Results
        1. 3.1.2.1 Over-Voltage Protection Cut-Off Mode
        2. 3.1.2.2 Over-Voltage Protection Clamping-Mode
        3. 3.1.2.3 ISO7637-2 Pulse 1
        4. 3.1.2.4 Overcurrent Protection
        5. 3.1.2.5 Load Dump
        6. 3.1.2.6 Cold Crank, Warm Start, and Cold Start
          1. 3.1.2.6.1 Cold Crank
          2. 3.1.2.6.2 Warm Start
          3. 3.1.2.6.3 Cold Start
        7. 3.1.2.7 Standby Current
        8. 3.1.2.8 Currency Sense Accuracy
  9. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
    2. 4.2 Documentation Support
    3. 4.3 サポート・リソース
    4. 4.4 Trademarks

Overcurrent Protection

Overcurrent protection testing primarily consisted of ensuring that the INA302 responded appropriately to increases in current and for the current sense amplifier to turn off LM74810 if an over-current event occurs. As mentioned in section 2.1.1, the INA302 can operate in latch mode or transparent mode. The testing shown in Figure 3-5 and Figure 3-6 was performed in latch mode.

GUID-20200710-SS0I-SGCL-8BMR-99KV8RTZRGSQ-low.pngFigure 3-5 Normal Transient Current

As shown in Figure 3-5, the red trace is the current output which sees an increase in current from 15A to 50A for 100ms. The overcurrent threshold is at 60A and as such the EN pin stays high in normal transient operation.

GUID-20200710-SS0I-PJWF-WDVX-7JPWSBQ8B5K9-low.pngFigure 3-6 Latch Mode Overcurrent Protection

As shown in Figure 3-6, the red trace is the current output to the e-load which experiences a 62A transient for 100ms. A 62A transient will trigger the overcurrent protection if the transient last longer than roughly 100µs. The green trace, which is the enable signal, pulls low during the fault conditions and will remain low until the INA302 LATCH pins are toggled to clear the fault. Having the enable signal pulled low, will turn off the MOSFETs, disconnecting the output from the input, resulting in a decrease in output voltage.