SNVS817B June   2012  – June 2019 LMR12015 , LMR12020

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application Circuit
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Descriptions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Recommended Operating Ratings
    3. 6.3 Electrical Characteristics
    4. 6.4 Typical Performance Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Boost Function
      2. 7.3.2  Low Input Voltage Considerations
      3. 7.3.3  High Output Voltage Considerations
      4. 7.3.4  Frequency Synchronization
      5. 7.3.5  Current Limit
      6. 7.3.6  Frequency Foldback
      7. 7.3.7  Soft Start
      8. 7.3.8  Output Overvoltage Protection
      9. 7.3.9  Undervoltage Lockout
      10. 7.3.10 Thermal Shutdown
    4. 7.4 Device Operation Modes
      1. 7.4.1 Enable Pin / Shutdown Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Detailed Design Procedure
        1. 8.2.1.1  Custom Design With WEBENCH® Tools
        2. 8.2.1.2  Inductor Selection
          1. 8.2.1.2.1 Inductor Calculation Example
          2. 8.2.1.2.2 Inductor Material Selection
        3. 8.2.1.3  Input Capacitor
        4. 8.2.1.4  Output Capacitor
        5. 8.2.1.5  Catch Diode
        6. 8.2.1.6  Boost Diode (Optional)
        7. 8.2.1.7  Boost Capacitor
        8. 8.2.1.8  Output Voltage
        9. 8.2.1.9  Feedforward Capacitor (Optional)
        10. 8.2.1.10 Calculating Efficiency and Junction Temperature
          1. 8.2.1.10.1 Schottky Diode Conduction Losses
          2. 8.2.1.10.2 Inductor Conduction Losses
          3. 8.2.1.10.3 MOSFET Conduction Losses
          4. 8.2.1.10.4 MOSFET Switching Losses
          5. 8.2.1.10.5 IC Quiescent Losses
          6. 8.2.1.10.6 MOSFET Driver Losses
          7. 8.2.1.10.7 Total Power Losses
          8. 8.2.1.10.8 Efficiency Calculation Example
          9. 8.2.1.10.9 Calculating the LMR2015/20 Junction Temperature
      2. 8.2.2 Application Curves
      3. 8.2.3 LMR12015/20 Circuit Examples
  9. 9 Layout
    1. 9.1 Layout Considerations
      1. 9.1.1 Compact Layout
      2. 9.1.2 Ground Plane and Shape Routing
      3. 9.1.3 FB Loop
      4. 9.1.4 PCB Summary
  10. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Third-Party Products Disclaimer
      2. 10.1.2 Development Support
        1. 10.1.2.1 Custom Design With WEBENCH® Tools
    2. 10.2 Related Links
    3. 10.3 Receiving Notification of Documentation Updates
    4. 10.4 Community Resources
    5. 10.5 Trademarks
    6. 10.6 Electrostatic Discharge Caution
    7. 10.7 Glossary
  11. 11Mechanical, Packaging, and Orderable Information

Package Options

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

7.4.1 Enable Pin / Shutdown Mode

Connect the EN pin to a voltage source greater than 1.8V to enable operation of the LMR12015/20. Apply a voltage less than 0.4V to put the part into shutdown mode. In shutdown mode the quiescent current drops to typically 70 nA. Switch leakage adds another 40 nA from the input supply. For proper operation, the LMR12015/20 EN pin should never be left floating, and the voltage should never exceed VIN + 0.3 V.

The simplest way to enable the operation of the LMR12015/20 is to connect the EN pin to AVIN which allows self start-up of the LMR12015/20 when the input voltage is applied.

When the rise time of VIN is longer than the soft-start time of the LMR12015/20 this method may result in an overshoot in output voltage. In such applications, the EN pin voltage can be controlled by a separate logic signal, or tied to a resistor divider, which reaches 1.8V after VIN is fully established (see Figure 25). This will minimize the potential for output voltage overshoot during a slow VIN ramp condition. Use the lowest value of VIN , seen in your application when calculating the resistor network, to ensure that the 1.8-V minimum EN threshold is reached.

LMR12015 LMR12020 30197008.gifFigure 25. Resistor Divider on EN
Equation 7. LMR12015 LMR12020 30197042.gif