SNVS346F November   2007  – November 2014 LM3481 , LM3481-Q1


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Handling Ratings: LM3481
    3. 6.3 Handling Ratings: LM3481-Q1
    4. 6.4 Recommended Operating Ratings
    5. 6.5 Thermal Information
    6. 6.6 Electrical Characteristics
    7. 6.7 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Overvoltage Protection
      2. 7.3.2 Bias Voltage
      3. 7.3.3 Slope Compensation Ramp
      4. 7.3.4 Frequency Adjust, Synchronization, and Shutdown
      5. 7.3.5 Undervoltage Lockout (UVLO) Pin
      6. 7.3.6 Short-Circuit Protection
    4. 7.4 Device Functional Modes
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Boost Converter
        1. Design Requirements
        2. Detailed Design Procedure
          1.  Custom Design with WEBENCH Tools
          2.  Power Inductor Selection
          3.  Programming the Output Voltage and Output Current
          4.  Current Limit With Additional Slope Compensation
          5.  Power Diode Selection
          6.  Power MOSFET Selection
          7.  Input Capacitor Selection
          8.  Output Capacitor Selection
          9.  Driver Supply Capacitor Selection
          10. Compensation
        3. Application Curve
      2. 8.2.2 Typical SEPIC Converter
        1. Design Requirements
        2. Detailed Design Procedure
          1. Power MOSFET Selection
          2. Power Diode Selection
          3. Selection of Inductors L1 and L2
          4. Sense Resistor Selection
          5. SEPIC Capacitor Selection
          6. Input Capacitor Selection
          7. Output Capacitor Selection
        3. Application Curve
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Custom Design with WEBENCH Tools
      2. 11.1.2 Receiving Notification of Documentation Updates
      3. 11.1.3 Related Documentation
    2. 11.2 Related Links
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

1 Features

  • LM3481QMM are Automotive-Grade Products That are AEC-Q100 Grade 1 Qualified (–40°C to +125°C Operating Junction Temperature)
  • 10-Lead VSSOP Package
  • Internal Push-Pull Driver With 1-A Peak Current Capability
  • Current Limit and Thermal Shutdown
  • Frequency Compensation Optimized With a Capacitor and a Resistor
  • Internal Softstart
  • Current Mode Operation
  • Adjustable Undervoltage Lockout With Hysteresis
  • Pulse Skipping at Light Loads
  • Key Specifications
    • Wide Supply Voltage Range of 2.97 V to 48 V
    • 100-kHz to 1-MHz Adjustable and Synchronizable Clock Frequency
    • ±1.5% (Over Temperature) Internal Reference
    • 10-µA Shutdown Current (Over Temperature)
  • Create a Custom Design Using the LM3481 with the WEBENCH Power Designer

2 Applications

  • Automotive Start-Stop Applications
  • Automotive ADAS Driver Information
  • One Cell/Two Cell Li-ion Battery Powered Portable Bluetooth Audio Systems
  • Notebooks, PDAs, Digital Cameras, and Other Portable Applications
  • Offline Power Supplies
  • Set-Top Boxes
  • Boost for Audio Amplifiers

3 Description

The LM3481 device is a versatile Low-Side N-FET high-performance controller for switching regulators. The device is designed for use in Boost, SEPIC and Flyback converters and topologies requiring a low-side FET as the primary switch. The LM3481 device can be operated at very high switching frequencies to reduce the overall solution size. The switching frequency of the LM3481 device can be adjusted to any value between 100kHz and 1MHz by using a single external resistor or by synchronizing it to an external clock. Current mode control provides superior bandwidth and transient response in addition to cycle-by-cycle current limiting. Current limit can be programmed with a single external resistor.

The LM3481 device has built-in protection features such as thermal shutdown, short-circuit protection and overvoltage protection. Power-saving shutdown mode reduces the total supply current to 5 µA and allows power supply sequencing. Internal soft-start limits the inrush current at start-up. Integrated current slope compensation simplifies the design and, if needed for specific applications, can be increased using a single resistor.

Device Information(1)

LM3481 VSSOP (10) 3.00 mm × 3.00 mm
  1. For all available packages, see the orderable addendum at the end of the data sheet.

automotive Boost Converter,5V to 12V boost converter schematic LM3481 LM3481-Q1 LM3481_Boost_schematic.gif Figure 1. LM3481 Typical 5V to 12V Boost Converter Application