SNAS416K July   2007  – November 2019 LM48511

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      EMI Graph: LM48511 RF Emissions — 3-Inch Cable
  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 VDD = 5 V
    6. 6.6 Electrical Characteristics VDD = 3.6 V
    7. 6.7 Electrical Characteristics VDD = 3 V
    8. 6.8 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 General Amplifier Function
      2. 7.3.2 Differential Amplifier Explanation
      3. 7.3.3 Audio Amplifier Power Dissipation and Efficiency
      4. 7.3.4 Regulator Power Dissipation
      5. 7.3.5 Shutdown Function
      6. 7.3.6 Regulator Feedback Select
    4. 7.4 Device Functional Modes
      1. 7.4.1 7.4.1 Fixed Frequency
      2. 7.4.2 7.4.2 Spread Spectrum Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1  Proper Selection of External Components
        2. 8.2.2.2  Power Supply Bypassing
        3. 8.2.2.3  Audio Amplifier Gain Setting Resistor Selection
        4. 8.2.2.4  Audio Amplifier Input Capacitor Selection
        5. 8.2.2.5  Selecting Regulator Output Capacitor
        6. 8.2.2.6  Selecting Regulating Bypass Capacitor
        7. 8.2.2.7  Selecting the Soft-Start (CSS) Capacitor
        8. 8.2.2.8  Selecting Diode (D1)
        9. 8.2.2.9  Duty Cycle
        10. 8.2.2.10 Selecting Inductor Value
        11. 8.2.2.11 Inductor Supplies
        12. 8.2.2.12 Setting the Regulator Output Voltage (PV1)
        13. 8.2.2.13 Discontinuous and Continuous Operation
        14. 8.2.2.14 ISW Feed-Forward Compensation for Boost Converter
        15. 8.2.2.15 Calculating Regulator Output Current
        16. 8.2.2.16 Design Parameters VSW and ISW
      3. 8.2.3 Application Curve
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Power and Ground Circuits
      2. 10.1.2 Layout Helpful Hints
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

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8.2.2.15 Calculating Regulator Output Current

The load current of the boost converter is related to the average inductor current by the relation:

Equation 12. IAMP = IINDUCTOR(AVE) × (1 – DC) (A)

where

  • DC is the duty cycle of the application

The switch current can be found by:

Equation 13. ISW = IINDUCTOR(AVE) + 1/2 (IRIPPLE) (A)

Inductor ripple current is dependent on inductance, duty cycle, supply voltage and frequency:

Equation 14. IRIPPLE = DC × (VDD – VSW) / (f × L) (A)

where

  • f = switching frequency = 1MHz

combining all terms, we can develop an expression which allows the maximum available load current to be calculated:

 

Equation 15. IAMP(max) = (1–DC) × [ISW(max)– DC (V – VSW)] / 2fL (A)

 

The equation shown to calculate maximum load current takes into account the losses in the inductor or turnoff switching losses of the FET and diode.