SNOSD17G October   2017  – December 2020 LM74700-Q1

PRODMIX  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Switching Characteristics
  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 Input Voltage
      2. 9.3.2 Charge Pump
      3. 9.3.3 Gate Driver
      4. 9.3.4 Enable
    4. 9.4 Device Functional Modes
      1. 9.4.1 Shutdown Mode
      2. 9.4.2 Conduction Mode
        1. 9.4.2.1 Regulated Conduction Mode
        2. 9.4.2.2 Full Conduction Mode
        3. 9.4.2.3 Reverse Current Protection Mode
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Typical Application
        1. 10.1.1.1 Design Requirements
        2. 10.1.1.2 Detailed Design Procedure
          1. 10.1.1.2.1 Design Considerations
          2. 10.1.1.2.2 MOSFET Selection
          3. 10.1.1.2.3 Charge Pump VCAP, input and output capacitance
        3. 10.1.1.3 Selection of TVS Diodes for 12-V Battery Protection Applications
        4. 10.1.1.4 Selection of TVS Diodes and MOSFET for 24-V Battery Protection Applications
        5. 10.1.1.5 Application Curves
    2. 10.2 OR-ing Application Configuration
  11. 11Power Supply Recommendations
  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

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

9.3.3 Gate Driver

The gate driver is used to control the external N-Channel MOSFET by setting the GATE to ANODE voltage to the corresponding mode of operation. There are three defined modes of operation that the gate driver operates under forward regulation, full conduction mode and reverse current protection, according to the ANODE to CATHODE voltage. Forward regulation mode, full conduction mode and reverse current protection mode are described in more detail in the Regulated conduction Mode, Full Conduction Mode and Reverse Current Production Mode sections. Figure 9-2 depicts how the modes of operation vary according to the ANODE to CATHODE voltage of the LM74700-Q1. The threshold between forward regulation mode and conduction mode is when the ANODE to CATHODE voltage is 50 mV. The threshold between forward regulation mode and reverse current protection mode is when the ANODE to CATHODE voltage is –11 mV.

GUID-8126AF89-9A47-404E-A8D5-847887BE8301-low.gifFigure 9-2 Gate Driver Mode Transitions

Before the gate driver is enabled following three conditions must be achieved:

  • The EN pin voltage must be greater than the specified input high voltage.
  • The VCAP to ANODE voltage must be greater than the undervoltage lockout voltage.
  • The ANODE voltage must be greater than VANODE POR Rising threshold.
If the above conditions are not achieved, then the GATE pin is internally connected to the ANODE pin, assuring that the external MOSFET is disabled. Once these conditions are achieved the gate driver operates in the correct mode depending on the ANODE to CATHODE voltage.