SNVSBP3B May   2020  – June 2021 LM62435-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 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 Timing Characteristics
    7. 7.7 Systems Characteristics
    8. 7.8 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  EN Uses for Enable and VIN UVLO
      2. 8.3.2  MODE/SYNC Pin Operation
        1. 8.3.2.1 Level-Dependent MODE/SYNC Pin Control
        2. 8.3.2.2 Pulse-Dependent MODE/SYNC Pin Control
        3. 8.3.2.3 Clock Locking
      3. 8.3.3  PGOOD Output Operation
      4. 8.3.4  Internal LDO, VCC UVLO, and BIAS Input
      5. 8.3.5  Bootstrap Voltage and VCBOOT-UVLO (CBOOT Pin)
      6. 8.3.6  Adjustable SW Node Slew Rate
      7. 8.3.7  Spread Spectrum
      8. 8.3.8  Soft Start and Recovery From Dropout
      9. 8.3.9  Output Voltage Setting
      10. 8.3.10 Overcurrent and Short Circuit Protection
      11. 8.3.11 Thermal Shutdown
      12. 8.3.12 Input Supply Current
    4. 8.4 Device Functional Modes
      1. 8.4.1 Shutdown Mode
      2. 8.4.2 Standby Mode
      3. 8.4.3 Active Mode
        1. 8.4.3.1 CCM Mode
        2. 8.4.3.2 Auto Mode - Light Load Operation
          1. 8.4.3.2.1 Diode Emulation
          2. 8.4.3.2.2 Frequency Reduction
        3. 8.4.3.3 FPWM Mode - Light Load Operation
        4. 8.4.3.4 Minimum On-time (High Input Voltage) Operation
        5. 8.4.3.5 Dropout
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1  Choosing the Switching Frequency
        2. 9.2.2.2  Setting the Output Voltage
        3. 9.2.2.3  Inductor Selection
        4. 9.2.2.4  Output Capacitor Selection
        5. 9.2.2.5  Input Capacitor Selection
        6. 9.2.2.6  BOOT Capacitor
        7. 9.2.2.7  BOOT Resistor
        8. 9.2.2.8  VCC
        9. 9.2.2.9  BIAS
        10. 9.2.2.10 CFF and RFF Selection
        11. 9.2.2.11 External UVLO
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Ground and Thermal Considerations
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Support Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

8.4.3 Active Mode

The LM61435-Q1 is in active mode whenever the EN pin is above VEN, VIN is high enough to satisfy VIN_OPERATE, and no other fault conditions are present. The simplest way to enable the operation is to connect the EN pin to VIN, which allows self start-up when the applied input voltage exceeds the minimum VIN_OPERATE.

In active mode, depending on the load current, input voltage, and output voltage, the LM62435-Q1 is in one of five modes:

  • Continuous conduction mode (CCM) with fixed switching frequency when load current is above half of the inductor current ripple.
  • Auto Mode - Light Load Operation: PFM when switching frequency is decreased at very light load.
  • FPWM Mode - Light Load Operation: Discontinuous conduction mode (DCM) when the load current is lower than half of the inductor current ripple.
  • Minimum on-time: At high input voltage and low output voltages, the switching frequency is reduced to maintain regulation.
  • Dropout mode: When switching frequency is reduced to minimize voltage dropout.