SNVSBZ4A February   2020  – November 2021 LM61480 , LM61495 , LM62460

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 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  Output Voltage Selection
      2. 8.3.2  Enable EN Pin and Use as VIN UVLO
      3. 8.3.3  SYNC/MODE Uses for Synchronization
      4. 8.3.4  Clock Locking
      5. 8.3.5  Adjustable Switching Frequency
      6. 8.3.6  RESET Output Operation
      7. 8.3.7  Internal LDO, VCC UVLO, and BIAS Input
      8. 8.3.8  Bootstrap Voltage and VCBOOT-UVLO (CBOOT Pin)
      9. 8.3.9  Adjustable SW Node Slew Rate
      10. 8.3.10 Spread Spectrum
      11. 8.3.11 Soft Start and Recovery From Dropout
      12. 8.3.12 Overcurrent and Short Circuit Protection
      13. 8.3.13 Hiccup
      14. 8.3.14 Thermal Shutdown
    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 Peak Current Mode Operation
        2. 8.4.3.2 Auto Mode Operation
          1. 8.4.3.2.1 Diode Emulation
        3. 8.4.3.3 FPWM Mode Operation
        4. 8.4.3.4 Minimum On-time (High Input Voltage) Operation
        5. 8.4.3.5 Dropout
        6. 8.4.3.6 Recovery from Dropout
        7. 8.4.3.7 Other Fault Modes
  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  CFF and RFF Selection
        10. 9.2.2.10 RSPSP Selection
        11. 9.2.2.11 RT Selection
        12. 9.2.2.12 RMODE Selection
        13. 9.2.2.13 External UVLO
        14. 9.2.2.14 Maximum Ambient Temperature
      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 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Support Resources
    4. 12.4 Trademarks
    5. 12.5 Glossary
    6. 12.6 Electrostatic Discharge Caution
  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 LM6x4xx is in active mode when the following occurs:

  • The EN pin is above VEN.
  • VIN is above VEN.
  • VIN is high enough to satisfy the VIN minimum operating input voltage.
  • No other fault conditions are present.
See Section 8.3 for protection features. The simplest way to enable the operation is to connect EN to VIN, allowing 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 LM6x4xx is in one of six sub-modes:

  • Continuous conduction mode (CCM) with fixed switching frequency and peak current mode operation
  • Discontinuous conduction mode (DCM) while in auto mode when the load current is lower than half of the inductor current ripple. If current continues to reduce, the device enters Pulse Frequency Modulation (PFM), which reduces the switch frequency to maintain regulation while reducing switching losses to achieve higher efficiency at light load.
  • Minimum on-time operation while the on time of the device needed for full-frequency operation at the requested low-duty cycle is not supported by TON_MIN
  • Forced pulse width modulation (FPWM) similar to CCM with fixed-switching frequency, but extends the fixed frequency range of operation from full to no load
  • Dropout mode when switching frequency is reduced to minimize dropout
  • Recovery from dropout similar to other modes of operation except the output voltage setpoint is gradually moved up until the programmed setpoint is reached.