SNVSCC4A October   2023  – September 2024 LP5811

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Timing Requirements
    7. 5.7 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 Synchronous Boost Converter
        1. 6.3.1.1 Undervoltage Lockout
        2. 6.3.1.2 Enable and Soft Start
        3. 6.3.1.3 Switching Frequency
        4. 6.3.1.4 Current Limit Operation
        5. 6.3.1.5 Boost PWM Mode
        6. 6.3.1.6 Boost PFM Mode
      2. 6.3.2 Analog Dimming
      3. 6.3.3 PWM Dimming
      4. 6.3.4 Autonomous Animation Engine Control
        1. 6.3.4.1 Animation Engine Pattern
        2. 6.3.4.2 Sloper
        3. 6.3.4.3 Animation Engine Unit (AEU)
        4. 6.3.4.4 Animation Pause Unit (APU)
      5. 6.3.5 Protections and Diagnostics
        1. 6.3.5.1 Overvoltage Protection
        2. 6.3.5.2 Output Short-to-Ground Protection
        3. 6.3.5.3 LED Open Detections
        4. 6.3.5.4 LED Short Detections
        5. 6.3.5.5 Thermal Shutdown
    4. 6.4 Device Functional Modes
    5. 6.5 Programming
    6. 6.6 Register Maps
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Application
      2. 7.2.2 Design Parameters
      3. 7.2.3 Detailed Design Procedure
        1. 7.2.3.1 Inductor Selection
        2. 7.2.3.2 Output Capacitor Selection
        3. 7.2.3.3 Input Capacitor Selection
        4. 7.2.3.4 Program Procedure
        5. 7.2.3.5 Programming Example
      4. 7.2.4 Application Performance Plots
    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
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

7.2.3.1 Inductor Selection

The inductor is the most important component in power regulator design, which affects steady-state operation, transient behavior, and loop stability. There are three important inductor specifications, inductor value, saturation current, and dc resistance (DCR).

The integrated boost converter in LP5811 is designed to work with inductor values between 0.37 µH and 2.9 µH. 1 µH is recommended in typical application. The inductor peak current can be calculated by Equation 8. Using the minimum input voltage, maximum output voltage, and maximum load current of the application can calculate the worst case.

In a boost regulator, the inductor dc current can be calculated by Equation 6.

Equation 6. ∆ I L D C = V O U T × I O U T V I N × η

where

  • VOUT is the output voltage of the boost converter
  • IOUT is the output current of the boost converter
  • VIN is the input voltage of the boost converter
  • η is the power-conversion efficiency, use 90% for most cases

The inductor ripple current is calculated by Equation 7.

Equation 7. ∆ I L P - P = V I N × D L × f S W

where

  • D is the duty cycle, which can be calculated by
  • L is the inductance value of the inductor
  • fSW is the switching frequency
  • VIN is the input voltage of the boost converter

Therefore, the inductor peak current is calculated by Equation 8.

Equation 8. ∆ I L P = ∆ I L D C + ∆ I L P - P 2

Inductor peak-to-peak current is recommended to be designed less than 40% of the average inductor current, with maximum output current setting. Large inductor value reduces the magnetic hysteresis losses in the inductor and improves EMI performance with small inductor ripple, but the load transient response time increases. The saturation current of the inductor must be higher than the calculated peak inductor current.

Table 7-2 Recommended Inductors
Part Number L (µH) DCR MAX (mΩ) SATURATION CURRENT (A) SIZE L×W×H (mm) VENDOR
XEL4030-102ME 1 9.78 9.0 4.0 × 4.0 × 3.1 Coilcraft
74438357010 1 13.5 9.6 4.1 × 4.1 × 3.1 Wurth Elecktronik
HBME042A-1R0MS-99 1 11.5 7.0 4.1 × 4.1 × 2.1 Cyntec