SNVS346H November   2007  – October 2024 LM3481

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
    1.     Pin Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings: LM3481
    3. 5.3 Recommended Operating Ratings
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Overvoltage Protection
      2. 6.3.2 Bias Voltage
      3. 6.3.3 Slope Compensation Ramp
      4. 6.3.4 Frequency Adjust, Synchronization, and Shutdown
      5. 6.3.5 Undervoltage Lockout (UVLO) Pin
      6. 6.3.6 Short-Circuit Protection
    4. 6.4 Device Functional Modes
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Applications
      1. 7.2.1 Boost Converter
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
          1. 7.2.1.2.1  Custom Design with WEBENCH Tools
          2. 7.2.1.2.2  Power Inductor Selection
          3. 7.2.1.2.3  Programming the Output Voltage and Output Current
          4. 7.2.1.2.4  Current Limit With Additional Slope Compensation
          5. 7.2.1.2.5  Power Diode Selection
          6. 7.2.1.2.6  Power MOSFET Selection
          7. 7.2.1.2.7  Input Capacitor Selection
          8. 7.2.1.2.8  Output Capacitor Selection
          9. 7.2.1.2.9  Driver Supply Capacitor Selection
          10. 7.2.1.2.10 Compensation
        3. 7.2.1.3 Application Curve
      2. 7.2.2 Typical SEPIC Converter
        1. 7.2.2.1 Design Requirements
        2. 7.2.2.2 Detailed Design Procedure
          1. 7.2.2.2.1 Power MOSFET Selection
          2. 7.2.2.2.2 Power Diode Selection
          3. 7.2.2.2.3 Selection of Inductors L1 and L2
          4. 7.2.2.2.4 Sense Resistor Selection
          5. 7.2.2.2.5 SEPIC Capacitor Selection
          6. 7.2.2.2.6 Input Capacitor Selection
          7. 7.2.2.2.7 Output Capacitor Selection
        3. 7.2.2.3 Application Curve
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Documentation Support
      1. 8.1.1 Custom Design with WEBENCH Tools
      2. 8.1.2 Related Documentation
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Pin Functions

PINI/ODESCRIPTION
NO.NAME
1ISENACurrent sense input pin. Voltage generated across an external sense resistor is fed into this pin.
2UVLOAUnder 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.
3COMPACompensation pin. A resistor and capacitor combination connected to this pin provides compensation for the control loop.
4FBAFeedback pin. Inverting input of the error amplifier.
5AGNDGAnalog ground pin. Internal bias circuitry reference. Should be connected to PGND at a single point.
6FA/SYNC/SDI/AFrequency 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.
7PGNDGPower ground pin. External power circuitry reference. Should be connected to AGND at a single point.
8DRODrive pin of the IC. The gate of the external MOSFET should be connected to this pin.
9VCCODriver supply voltage pin. A bypass capacitor must be connected from this pin to PGND. See Section 7.2.1.2.9 section. Do not bias externally.
10VINPPower supply input pin.