JAJSIH9B December   2019  – November 2022 LMR36503

PRODUCTION DATA  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
  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 (Commercial) 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 Switching Characteristics
    8. 7.8 System Characteristics
    9. 7.9 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  Enable, Start-up, and Shutdown
      2. 8.3.2  Adjustable Switching Frequency (with RT)
      3. 8.3.3  Power-Good Output Operation
      4. 8.3.4  Internal LDO, VCC UVLO, and VOUT/BIAS Input
      5. 8.3.5  Bootstrap Voltage and VCBOOT-UVLO (CBOOT Terminal)
      6. 8.3.6  Output Voltage Selection
      7. 8.3.7  Soft Start and Recovery from Dropout
        1. 8.3.7.1 Recovery from Dropout
      8. 8.3.8  Current Limit and Short Circuit
      9. 8.3.9  Thermal Shutdown
      10. 8.3.10 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
          1. 9.2.2.2.1 FB for Adjustable Output
        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 CBOOT
        7. 9.2.2.7 VCC
        8. 9.2.2.8 CFF Selection
          1. 9.2.2.8.1 External UVLO
        9. 9.2.2.9 Maximum Ambient Temperature
      3. 9.2.3 Application Curves
    3. 9.3 Best Design Practices
    4. 9.4 Power Supply Recommendations
    5. 9.5 Layout
      1. 9.5.1 Layout Guidelines
        1. 9.5.1.1 Ground and Thermal Considerations
      2. 9.5.2 Layout Example
  10. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 サポート・リソース
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  11. 11Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ
発注情報

8.4.3 Active Mode

The LMR36503 is in active mode whenever the EN pin is above VEN-VOUT, VIN is high enough to satisfy VIN_R, 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_R.

In active mode, depending on the load current, input voltage, and output voltage, the LMR36503 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.