SNVS523G September   2007  – January 2018 LM3103

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Typical Application Schematic
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin 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 Functional Block Diagram
    2. 7.2 Feature Description
      1. 7.2.1  COT Control Circuit Overview
      2. 7.2.2  Startup Regulator (VCC)
      3. 7.2.3  Regulation Comparator
      4. 7.2.4  Zero Coil Current Detect
      5. 7.2.5  Over-Voltage Comparator
      6. 7.2.6  ON-Time Timer, Shutdown
      7. 7.2.7  Current Limit
      8. 7.2.8  N-Channel MOSFET and Driver
      9. 7.2.9  Soft-Start
      10. 7.2.10 Thermal Protection
  8. 8 Applications and Implementation
    1. 8.1 Application Information
      1. 8.1.1 External Components
  9. 9 Device and Documentation Support
    1. 9.1 Receiving Notification of Documentation Updates
    2. 9.2 Community Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  10. 10Mechanical, Packaging, and Orderable Information

Package Options

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

7.2.2 Startup Regulator (VCC)

A startup regulator is integrated within the LM3103. The input pin VIN can be connected directly to a line voltage up to 42 V. The VCC output regulates at 6 V, and is current limited to 30 mA. Upon power up, the regulator sources current into an external capacitor CVCC, which is connected to the VCC pin. For stability, CVCC must be at least 1 µF. When the voltage on the VCC pin is higher than the under-voltage lock-out (UVLO) threshold of 3.7 V, the main MOSFET is enabled and the SS pin is released to allow the soft-start capacitor CSS to charge.

The minimum input voltage is determined by the dropout voltage of the regulator and the VCC UVLO falling threshold (≊3.4 V). If VIN is less than ≊4.0 V, the regulator shuts off and VCC goes to zero.