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

7.3.6 Fault Protection

The LP8868 family is able to provide fault protections and send fault report signals in many fault conditions, including LED open, LED short to GND, sense resistor open and short, internal switching FET fault and thermal shutdown. The fault criterion for different topology is shown in below.

Table 7-3 Protections in Buck topology
TYPE CRITERION BEHAVIOR
LED open load VUVP < 1.2 V for 100us Fault pin pulls low. The device stops switching when VUVP < 1.2 V.
LED+ and LED- short circuit VIN - VCSP < 300 mV for 30ms Fault pin pulls low. The keeps normal behavior.
LED- short to GND VUVP < 1.2 V for 100us Fault pin pulls low. The device stops switching and recovers when fault is removed.
Sense-resistor open load VCSP - VCSN > 300mV for 20us Fault pin pulls low. The device stops switching and recovers when fault is removed.
Sense-resistor short circuit Error Amplifer output high for 100us Fault pin pulls low. The device keeps switching under the cycle-by-cycle current limit.
Switching FET open Error Amplifer output high for 100us Fault pin pulls low. The device keeps maximum duty cycle turn-on switching.
Switching FET short VCSP - VCSN > 300 mV for 20us Fault pin pulls low. The device stops switching and recovers when fault is removed.
Thermal shutdown TJ > TTSD for 100us Fault pin pulls low. The device stops switching when TJ>TTSD, and is re-activated when TJ falls below the hysteresis level.
VIN UVLO VCC < 3 V Fault pin pulls low. The device stops switching and recovers when fault is removed.
Table 7-4 Protections in Boost / Buck-Boost topology
TYPE CRITERION BEHAVIOR
LED open load VOVP > 1.2 V for 100us Fault pin pulls low. The device stops switching when VOVP > 1.2 V.
LED+ and LED- short circuit (Buck-Boost) VCSP - VIN < 300mV for 30ms Fault pin pulls low. The device keeps normal behavior.
LED+ short to GND CSP - VCSN > 300mV for 20us Fault pin pulls low. The device stops switching and recovers when fault is removed.
Sense-resistor open load VCSP - VCSN > 300mV for 20us Fault pin pulls low. The device stops switching and recovers when fault is removed.
Sense-resistor short circuit Error Amplifer output high for 100us Fault pin pulls low. The device keeps switching under the cycle-by-cycle current limit.
Switching FET open Error Amplifer output high for 100us Fault pin pulls low. The device keeps maximum duty cycle turn-on switching.
Switching FET short Error Amplifer output high for 100us Fault pin pulls low. The device tries to keep switching.
Thermal shutdown TJ > TTSD for 100us Fault pin pulls low. The device stops switching when TJ>TTSD, and is re-activated when TJ falls below the hysteresis level.
VIN UVLO VCC < 3 V Fault pin pulls low. The device stops switching and recovers when fault is removed.