SLVSH98A July   2023  – November 2023 LP8868U-Q1 , LP8868V-Q1 , LP8868W-Q1 , LP8868X-Q1 , LP8868Y-Q1 , LP8868Z-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4  Comparison Table
  6. 5 Pin Configuration and Functions
  7. 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
    6. 6.6 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Adaptive Off-Time Current Mode Control
        1. 7.3.1.1 Switching Frequency Settings
        2. 7.3.1.2 Spread Spectrum
      2. 7.3.2 Setting LED Current
      3. 7.3.3 Internal Soft Start
      4. 7.3.4 Dimming Mode
        1. 7.3.4.1 PWM dimming
        2. 7.3.4.2 Analog dimming
        3. 7.3.4.3 Hybrid Dimming
        4. 7.3.4.4 Flexible Dimming
      5. 7.3.5 Undervoltage Lockout
      6. 7.3.6 Fault Protection
      7. 7.3.7 Thermal Foldback
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 LP8868XQDMTRQ1 12-V Input, 1-A Output, 8-piece LED With Boost Topology
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Inductor Selection
          2. 8.2.1.2.2 Input Capacitor Selection
          3. 8.2.1.2.3 Output Capacitor Selection
          4. 8.2.1.2.4 Sense Resistor Selection
          5. 8.2.1.2.5 Other External Components Selection
        3. 8.2.1.3 Application Curves
      2. 8.2.2 LP8868YQDMTRQ1 12-V Input, 1-A Output, 5-piece LED With Buck-Boost Topology
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1 Inductor Selection
          2. 8.2.2.2.2 Input Capacitor Selection
          3. 8.2.2.2.3 Output Capacitor Selection
          4. 8.2.2.2.4 Sense Resistor Selection
          5. 8.2.2.2.5 Other External Components Selection
        3. 8.2.2.3 Application Curves
      3. 8.2.3 LP8868ZQDMTRQ1 12-V Input, 2-A Output, 1-piece LED With Buck Topology
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Detailed Design Procedure
          1. 8.2.3.2.1 Inductor Selection
          2. 8.2.3.2.2 Input Capacitor Selection
          3. 8.2.3.2.3 Output Capacitor Selection
          4. 8.2.3.2.4 Sense Resistor Selection
          5. 8.2.3.2.5 Other External Components Selection
        3. 8.2.3.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Receiving Notification of Documentation Updates
    2. 9.2 Support Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

Package Options

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

7.3.4.2 Analog dimming

The LP8868 family supports analog dimming which regulates the LED current through the ADIM/HD pin. The analog dimming mode is enabled when the PWM/EN pin is always high and the ADIM/HD pin is configured by a PWM input signal. And the internal digital circuits is able to respond to the duty cycle change of the PWM input signal with tens of micro-seconds delay

The internal voltage reference, VREF, changes in proportion to the duty cycle of the PWM input signal at the ADIM/HD pin. VREF is 200 mV when the PWM input signal at the ADIM/HD pin has a 100% duty cycle, for instance, and VREF is 20 mV when the PWM input signal has a 10% duty cycle.