TIDUEX5 October   2020

 

  1.   Description
  2.   Resources
  3.   Applications
  4.   Features
  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 Support Resources
    4. 4.4 Trademarks

2.2.4.1 Blocking MOSFET

Selection of the blocking MOSFET requires consideration of electrical parameters which includes maximum source current through body diode and the Rdson of the device.

Selection of the MOSFET along with TVS diode should ensure that of the MOSFET is not surpassed in automotive transient events and any anticipated fault conditions. For this design 60 V MOSFETS are used with a single bidirectional TVS device. The MOSFETs chosen have a of ±20 V allowing safe operation when the maximum 14 V from the LM74810-Q1 is applied, the MOSFET plays a role in the conduction losses as well as reverse current detection by the ideal diode controller. As such, guidelines are given by the LM74810 data sheet for ranges for MOSFET selection based on the nominal operating current.

Equation 3. GUID-20200710-SS0I-JHMP-R2BH-JHLSLJ8TLLQR-low.gif

The range is provided above to serve as a guideline while keeping in mind the MOSFETs temperature resistance based on expected power dissipation.