SNVSBD1B August   2020  – May 2024 LP8866S-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  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 Logic Interface Characteristics
    7. 5.7 Timing Requirements for I2C Interface
    8.     14
    9. 5.8 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 Control Interface
      2. 6.3.2 Function Setting
      3. 6.3.3 Device Supply (VDD)
      4. 6.3.4 Enable (EN)
      5. 6.3.5 Charge Pump
      6. 6.3.6 Boost Controller
        1. 6.3.6.1 Boost Cycle-by-Cycle Current Limit
        2. 6.3.6.2 Controller Min On/Off Time
        3. 6.3.6.3 Boost Adaptive Voltage Control
          1. 6.3.6.3.1 FB Divider Using Two-Resistor Method
          2. 6.3.6.3.2 FB Divider Using Three-Resistor Method
          3. 6.3.6.3.3 FB Divider Using External Compensation
        4. 6.3.6.4 Boost Sync and Spread Spectrum
        5. 6.3.6.5 Boost Output Discharge
        6. 6.3.6.6 Light Load Mode
      7. 6.3.7 LED Current Sinks
        1. 6.3.7.1 LED Output Current Setting
        2. 6.3.7.2 LED Output String Configuration
        3. 6.3.7.3 LED Output PWM Clock Generation
      8. 6.3.8 Brightness Control
        1. 6.3.8.1 Brightness Control Signal Path
        2. 6.3.8.2 Dimming Mode
        3. 6.3.8.3 LED Dimming Frequency
        4. 6.3.8.4 Phase-Shift PWM Mode
        5. 6.3.8.5 Hybrid Mode
        6. 6.3.8.6 Direct PWM Mode
        7. 6.3.8.7 Sloper
        8. 6.3.8.8 PWM Detector Hysteresis
        9. 6.3.8.9 Dither
      9. 6.3.9 Protection and Fault Detections
        1. 6.3.9.1 Supply Faults
          1. 6.3.9.1.1 VIN Undervoltage Faults (VINUVLO)
          2. 6.3.9.1.2 VIN Overvoltage Faults (VINOVP)
          3. 6.3.9.1.3 VDD Undervoltage Faults (VDDUVLO)
          4. 6.3.9.1.4 VIN OCP Faults (VINOCP)
            1. 6.3.9.1.4.1 VIN OCP Current Limit vs. Boost Cycle-by-Cycle Current Limit
          5. 6.3.9.1.5 Charge Pump Faults (CPCAP, CP)
          6. 6.3.9.1.6 CRC Error Faults (CRCERR)
        2. 6.3.9.2 Boost Faults
          1. 6.3.9.2.1 Boost Overvoltage Faults (BSTOVPL, BSTOVPH)
          2. 6.3.9.2.2 Boost Overcurrent Faults (BSTOCP)
          3. 6.3.9.2.3 LEDSET Resistor Missing Faults (LEDSET)
          4. 6.3.9.2.4 MODE Resistor Missing Faults (MODESEL)
          5. 6.3.9.2.5 FSET Resistor Missing Faults (FSET)
          6. 6.3.9.2.6 ISET Resistor Out of Range Faults (ISET)
          7. 6.3.9.2.7 Thermal Shutdown Faults (TSD)
        3. 6.3.9.3 LED Faults
          1. 6.3.9.3.1 Open LED Faults (OPEN_LED)
          2. 6.3.9.3.2 Short LED Faults (SHORT_LED)
          3. 6.3.9.3.3 LED Short to GND Faults (GND_LED)
          4. 6.3.9.3.4 Invalid LED String Faults (INVSTRING)
          5. 6.3.9.3.5 I2C Timeout Faults
        4. 6.3.9.4 Overview of the Fault and Protection Schemes
    4. 6.4 Device Functional Modes
      1. 6.4.1  State Diagram
      2. 6.4.2  Shutdown
      3. 6.4.3  Device Initialization
      4. 6.4.4  Standby Mode
      5. 6.4.5  Power-line FET Soft Start
      6. 6.4.6  Boost Start-Up
      7. 6.4.7  Normal Mode
      8. 6.4.8  Fault Recovery
      9. 6.4.9  Latch Fault
      10. 6.4.10 Start-Up Sequence
    5. 6.5 Programming
      1. 6.5.1 I2C-Compatible Interface
      2. 6.5.2 Programming Examples
        1. 6.5.2.1 General Configuration Registers
        2. 6.5.2.2 Clearing Fault Interrupts
        3. 6.5.2.3 Disabling Fault Interrupts
        4. 6.5.2.4 Diagnostic Registers
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Applications
      1. 7.2.1 Full Feature Application for Display Backlight
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
          1. 7.2.1.2.1  Inductor Selection
          2. 7.2.1.2.2  Output Capacitor Selection
          3. 7.2.1.2.3  Input Capacitor Selection
          4. 7.2.1.2.4  Charge Pump Output Capacitor
          5. 7.2.1.2.5  Charge Pump Flying Capacitor
          6. 7.2.1.2.6  Output Diode
          7. 7.2.1.2.7  Switching FET
          8. 7.2.1.2.8  Boost Sense Resistor
          9. 7.2.1.2.9  Power-Line FET
          10. 7.2.1.2.10 Input Current Sense Resistor
          11. 7.2.1.2.11 Feedback Resistor Divider
          12. 7.2.1.2.12 Critical Components for Design
        3. 7.2.1.3 Application Curves
      2. 7.2.2 Application with Basic/Minimal Operation
        1. 7.2.2.1 Design Requirements
        2. 7.2.2.2 Detailed Design Procedure
        3. 7.2.2.3 Application Curves
      3. 7.2.3 SEPIC Mode Application
        1. 7.2.3.1 Design Requirements
        2. 7.2.3.2 Detailed Design Procedure
          1. 7.2.3.2.1  Inductor Selection
          2. 7.2.3.2.2  Coupling Capacitor Selection
          3. 7.2.3.2.3  Output Capacitor Selection
          4. 7.2.3.2.4  Input Capacitor Selection
          5. 7.2.3.2.5  Charge Pump Output Capacitor
          6. 7.2.3.2.6  Charge Pump Flying Capacitor
          7. 7.2.3.2.7  Switching FET
          8. 7.2.3.2.8  Output Diode
          9. 7.2.3.2.9  Switching Sense Resistor
          10. 7.2.3.2.10 Power-Line FET
          11. 7.2.3.2.11 Input Current Sense Resistor
          12. 7.2.3.2.12 Feedback Resistor Divider
          13. 7.2.3.2.13 Critical Components for Design
        3. 7.2.3.3 Application Curves
    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 Device Support
      1. 8.1.1 Third-Party Products Disclaimer
    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

6.3.6.4 Boost Sync and Spread Spectrum

Spread spectrum function could be enabled when BST_SYNC pin is high and disabled when BST_SYNC pin is low.

If an external CLK signal is on the BST_SYNC pin, the boost controller can be clocked by this signal. If the clock disappears later, the boost continues operation at the frequency defined by RBST_FSET resistor, and the spread spectrum function will be enabled or disabled depending on the final pin level of BST_SYNC.

Table 6-3 Boost Synchronization Mode
BST_SYNC PIN LEVEL BOOST CLOCK MODE
Low (GND) Spread spectrum disabled
High (VDDIO) Spread spectrum enabled
100kHz to 2222kHz clock frequency Spread spectrum disabled, external synchronization mode

If using the external BST_SYNC input, the RBST_SET resistor should be chosen the closest boost frequency options with the external frequency.

The spread spectrum function helps to reduce EMI noise around the switching frequency and its harmonic frequencies. The internal spread spectrum function modulates the boost frequency ±3.3% to 7.2% from the central frequency with a 200Hz to 1.2kHz modulation frequency. The switching frequency variation is programmable by SPREAD_RANGE register, and the modulation frequency is programmable by SPREAD_MOD_FREQ register. The spread-spectrum function cannot be used when an external synchronization clock is used.

Table 6-4 Spread Spectrum Frequency Range
SPREAD_RANGE (Binary) SWITCHING FREQUENCY VARIATION
00 ±3.3%
01 ±4.3%
10 (Default) ±5.3%
11 ±7.2%
Table 6-5 Spread Spectrum Modulation Frequency
SPREAD_MOD_FREQ (Binary) MODULATION FREQUENCY
00 (Default) 200Hz
01 500Hz
10 800Hz
11 1200Hz