SNVS682D November   2010  – December 2015 LM3444

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Theory of Operation
      2. 7.3.2 Valley-Fill Circuit
      3. 7.3.3 Valley-Fill Operation
      4. 7.3.4 Buck Converter
      5. 7.3.5 Overview Of Constant Off-Time Control
      6. 7.3.6 Thermal Shutdown
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1  Determining Duty-Cycle (D)
      2. 8.1.2  Calculating Off-Time
      3. 8.1.3  Setting the Switching Frequency
      4. 8.1.4  Inductor Selection
      5. 8.1.5  Setting the LED Current
      6. 8.1.6  Valley Fill Capacitors
      7. 8.1.7  Determining the Capacitance Value of the Valley-Fill Capacitors
      8. 8.1.8  Determining Maximum Number of Series Connected LEDs Allowed
      9. 8.1.9  Output Capacitor
      10. 8.1.10 Switching MOSFET
      11. 8.1.11 Recirculating Diode
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curve
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary

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10 Layout

10.1 Layout Guidelines

Keep the low power components for FILTER and COFF close to the LM3444 with short traces. The ISNS trace should also be as short and direct as possible. Keep the high current switching paths generated by R3, Q2, L2, and D10 as short as possible to minimize generated switching noise and improve EMI.

10.2 Layout Example

LM3444 snvs682_layout.gif Figure 21. Layout Recommendation