SNVS346F November   2007  – November 2014 LM3481 , LM3481-Q1

PRODUCTION DATA.  

  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. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1  Custom Design with WEBENCH Tools
          2. 8.2.1.2.2  Power Inductor Selection
          3. 8.2.1.2.3  Programming the Output Voltage and Output Current
          4. 8.2.1.2.4  Current Limit With Additional Slope Compensation
          5. 8.2.1.2.5  Power Diode Selection
          6. 8.2.1.2.6  Power MOSFET Selection
          7. 8.2.1.2.7  Input Capacitor Selection
          8. 8.2.1.2.8  Output Capacitor Selection
          9. 8.2.1.2.9  Driver Supply Capacitor Selection
          10. 8.2.1.2.10 Compensation
        3. 8.2.1.3 Application Curve
      2. 8.2.2 Typical SEPIC Converter
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1 Power MOSFET Selection
          2. 8.2.2.2.2 Power Diode Selection
          3. 8.2.2.2.3 Selection of Inductors L1 and L2
          4. 8.2.2.2.4 Sense Resistor Selection
          5. 8.2.2.2.5 SEPIC Capacitor Selection
          6. 8.2.2.2.6 Input Capacitor Selection
          7. 8.2.2.2.7 Output Capacitor Selection
        3. 8.2.2.3 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

5 Pin Configuration and Functions

10-Pin
VSSOP Package
Top View
LM3481 LM3481-Q1 LM3481_Boost_Controller_pinout.gif Figure 2. LM3481 10-Pin VSSOP Package

Pin Functions

PIN I/O DESCRIPTION
NO. NAME
1 ISEN A Current sense input pin. Voltage generated across an external sense resistor is fed into this pin.
2 UVLO A Under voltage lockout pin. A resistor divider from VIN to ground is connected to the UVLO pin. The ratio of these resistances determine the input voltage which allows switching and the hysteresis to disable switching.
3 COMP A Compensation pin. A resistor and capacitor combination connected to this pin provides compensation for the control loop.
4 FB A Feedback pin. Inverting input of the error amplifier.
5 AGND G Analog ground pin. Internal bias circuitry reference. Should be connected to PGND at a single point.
6 FA/SYNC/SD I/A Frequency adjust, synchronization, and shutdown pin. A resistor connected from this pin to ground sets the oscillator frequency. An external clock signal at this pin will synchronize the controller to the frequency of the clock. A high level on this pin for ≥ 30 µs will turn the device off and the device will then draw 5 µA from the supply typically.
7 PGND G Power ground pin. External power circuitry reference. Should be connected to AGND at a single point.
8 DR O Drive pin of the IC. The gate of the external MOSFET should be connected to this pin.
9 VCC O Driver supply voltage pin. A bypass capacitor must be connected from this pin to PGND. See Driver Supply Capacitor Selection section. Do not bias externally.
10 VIN P Power supply input pin.