SNVSB55H February   2019  – June 2024 LM63615-Q1 , LM63625-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 6 Specifications
    1.     Absolute Maximum Ratings
    2. 6.1 ESD Ratings
    3. 6.2 Recommended Operating Conditions
    4. 6.3 Thermal Information
    5. 6.4 Electrical Characteristics
    6. 6.5 Timing Characteristics
    7. 6.6 Switching Characteristics
    8. 6.7 System Characteristics
    9. 6.8 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Sync/Mode Selection
      2. 7.3.2 Output Voltage Selection
      3. 7.3.3 Switching Frequency Selection
        1. 7.3.3.1 Spread Spectrum Option
      4. 7.3.4 Enable and Start-Up
      5. 7.3.5 RESET Flag Output
      6. 7.3.6 Undervoltage Lockout and Thermal Shutdown and Output Discharge
    4. 7.4 Device Functional Modes
      1. 7.4.1 Overview
      2. 7.4.2 Light Load Operation
        1. 7.4.2.1 Sync/FPWM Operation
      3. 7.4.3 Dropout Operation
      4. 7.4.4 Minimum On-time Operation
      5. 7.4.5 Current Limit and Short-Circuit Operation
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Choosing the Switching Frequency
        2. 8.2.2.2 Setting the Output Voltage
          1. 8.2.2.2.1 CFF Selection
        3. 8.2.2.3 Inductor Selection
        4. 8.2.2.4 Output Capacitor Selection
        5. 8.2.2.5 Input Capacitor Selection
        6. 8.2.2.6 CBOOT
        7. 8.2.2.7 VCC
        8. 8.2.2.8 External UVLO
        9. 8.2.2.9 Maximum Ambient Temperature
      3. 8.2.3 Full Feature Design Example
      4. 8.2.4 Application Curves
      5. 8.2.5 EMI Performance Curves
    3. 8.3 Best Design Practices
    4. 8.4 Power Supply Recommendations
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
        1. 8.5.1.1 Ground and Thermal Considerations
      2. 8.5.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Device Nomenclature
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

Package Options

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

7.3.6 Undervoltage Lockout and Thermal Shutdown and Output Discharge

The LM636x5-Q1 incorporates an undervoltage-lockout feature on the output of the internal LDO (at the VCC pin). When VIN reaches approximately VPOR-R, the device is ready to receive an EN signal and start up. When VIN falls below VPOR-F, the device shuts down, regardless of EN status. Because the LDO is in dropout during these transitions, the above values roughly represent the VCC voltage levels during the transitions. An extended input voltage UVLO can also be accomplished as shown in Section 8.2.2.8.

Thermal shutdown is provided to protect the regulator from excessive junction temperature. When the junction temperature reaches about 163°C, the device shuts down; re-start occurs when the temperature falls to about 150°C.

The LM636x5-Q1 features an output voltage discharge FET connected from the SW pin to ground. This FET is activated when the EN input is below VEN-L, or when the output voltage exceeds VRESET-HIGH. This way, the output capacitors are discharged through the power inductor. At output voltages above about 5 V, the discharge current is approximately constant at IPOR or about 1.4 mA. Below this voltage, the FET characteristic looks approximately resistive at a value of 2.5 kΩ.