SNVSBD1A August   2020  – February 2021 LP8866S-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and 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
    6. 6.6 Logic Interface Characteristics
    7. 6.7 Timing Requirements for I2C Interface
    8.     14
    9. 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 Control Interface
      2. 7.3.2 Function Setting
      3. 7.3.3 Device Supply (VDD)
      4. 7.3.4 Enable (EN)
      5. 7.3.5 Charge Pump
      6. 7.3.6 Boost Controller
        1. 7.3.6.1 Boost Cycle-by-Cycle Current Limit
        2. 7.3.6.2 Controller Min On/Off Time
        3. 7.3.6.3 Boost Adaptive Voltage Control
          1. 7.3.6.3.1 FB Divider Using Two-Resistor Method
          2. 7.3.6.3.2 FB Divider Using Three-Resistor Method
          3. 7.3.6.3.3 FB Divider Using External Compensation
        4. 7.3.6.4 Boost Sync and Spread Spectrum
        5. 7.3.6.5 Boost Output Discharge
        6. 7.3.6.6 Light Load Mode
      7. 7.3.7 LED Current Sinks
        1. 7.3.7.1 LED Output Current Setting
        2. 7.3.7.2 LED Output String Configuration
        3. 7.3.7.3 LED Output PWM Clock Generation
      8. 7.3.8 Brightness Control
        1. 7.3.8.1 Brightness Control Signal Path
        2. 7.3.8.2 Dimming Mode
        3. 7.3.8.3 LED Dimming Frequency
        4. 7.3.8.4 Phase-Shift PWM Mode
        5. 7.3.8.5 Hybrid Mode
        6. 7.3.8.6 Direct PWM Mode
        7. 7.3.8.7 Sloper
        8. 7.3.8.8 PWM Detector Hysteresis
        9. 7.3.8.9 Dither
      9. 7.3.9 Protection and Fault Detections
        1. 7.3.9.1 Supply Faults
          1. 7.3.9.1.1 VIN Undervoltage Faults (VINUVLO)
          2.        52
          3. 7.3.9.1.2 VIN Overvoltage Faults (VINOVP)
          4. 7.3.9.1.3 VDD Undervoltage Faults (VDDUVLO)
          5. 7.3.9.1.4 VIN OCP Faults (VINOCP)
            1. 7.3.9.1.4.1 VIN OCP Current Limit vs. Boost Cycle-by-Cycle Current Limit
          6. 7.3.9.1.5 Charge Pump Faults (CPCAP, CP)
          7. 7.3.9.1.6 CRC Error Faults (CRCERR)
        2. 7.3.9.2 Boost Faults
          1. 7.3.9.2.1 Boost Overvoltage Faults (BSTOVPL, BSTOVPH)
          2. 7.3.9.2.2 Boost Overcurrent Faults (BSTOCP)
          3. 7.3.9.2.3 LEDSET Resistor Missing Faults (LEDSET)
          4. 7.3.9.2.4 MODE Resistor Missing Faults (MODESEL)
          5. 7.3.9.2.5 FSET Resistor Missing Faults (FSET)
          6. 7.3.9.2.6 ISET Resistor Out of Range Faults (ISET)
          7. 7.3.9.2.7 Thermal Shutdown Faults (TSD)
        3. 7.3.9.3 LED Faults
          1. 7.3.9.3.1 Open LED Faults (OPEN_LED)
          2. 7.3.9.3.2 Short LED Faults (SHORT_LED)
          3. 7.3.9.3.3 LED Short to GND Faults (GND_LED)
          4. 7.3.9.3.4 Invalid LED String Faults (INVSTRING)
          5. 7.3.9.3.5 I2C Timeout Faults
        4. 7.3.9.4 Overview of the Fault and Protection Schemes
    4. 7.4 Device Functional Modes
      1. 7.4.1  State Diagram
      2. 7.4.2  Shutdown
      3. 7.4.3  Device Initialization
      4. 7.4.4  Standby Mode
      5. 7.4.5  Power-line FET Soft Start
      6. 7.4.6  Boost Start-Up
      7. 7.4.7  Normal Mode
      8. 7.4.8  Fault Recovery
      9. 7.4.9  Latch Fault
      10. 7.4.10 Start-Up Sequence
    5. 7.5 Programming
      1. 7.5.1 I2C-Compatible Interface
      2. 7.5.2 Programming Examples
        1. 7.5.2.1 General Configuration Registers
        2. 7.5.2.2 Clearing Fault Interrupts
        3. 7.5.2.3 Disabling Fault Interrupts
        4. 7.5.2.4 Diagnostic Registers
    6. 7.6 Register Maps
      1. 7.6.1 FullMap Registers
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Full Feature Application for Display Backlight
        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  Output Capacitor Selection
          3. 8.2.1.2.3  Input Capacitor Selection
          4. 8.2.1.2.4  Charge Pump Output Capacitor
          5. 8.2.1.2.5  Charge Pump Flying Capacitor
          6. 8.2.1.2.6  Output Diode
          7. 8.2.1.2.7  Switching FET
          8. 8.2.1.2.8  Boost Sense Resistor
          9. 8.2.1.2.9  Power-Line FET
          10. 8.2.1.2.10 Input Current Sense Resistor
          11. 8.2.1.2.11 Feedback Resistor Divider
          12. 8.2.1.2.12 Critical Components for Design
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Application with Basic/Minimal Operation
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Curves
      3. 8.2.3 SEPIC Mode Application
        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  Coupling Capacitor Selection
          3. 8.2.3.2.3  Output Capacitor Selection
          4. 8.2.3.2.4  Input Capacitor Selection
          5. 8.2.3.2.5  Charge Pump Output Capacitor
          6. 8.2.3.2.6  Charge Pump Flying Capacitor
          7. 8.2.3.2.7  Switching FET
          8. 8.2.3.2.8  Output Diode
          9. 8.2.3.2.9  Switching Sense Resistor
          10. 8.2.3.2.10 Power-Line FET
          11. 8.2.3.2.11 Input Current Sense Resistor
          12. 8.2.3.2.12 Feedback Resistor Divider
          13. 8.2.3.2.13 Critical Components for Design
        3. 8.2.3.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

10.1 Layout Guidelines

Figure 10-1 shows a layout recommendation for the LP8866S-Q1 used to illustrate the principles of good layout. This layout can be adapted to the actual application layout if and where possible. It is important that all boost components are close to each other and to the chip; the high-current traces must be wide enough. VDD must be as noise-free as possible. Place a VDD bypass capacitor near the VDD and GND pins. A charge-pump capacitor, boost input capacitors, and boost output capacitors must have closest VIAs to GND. Place the charge-pump capacitors close to the device. The main points to guide the PCB layout design:

  • Current loops need to be minimized:
    • For low frequency the minimal current loop can be achieved by placing the boost components as close as possible to each other. Input and output capacitor grounds need to be close to each other to minimize current loop size.
    • Minimal current loops for high frequencies can be achieved by making sure that the ground plane is intact under the current traces. High frequency return currents follow the route with minimum impedance, which is the route with minimum loop area, not necessarily the shortest path. Minimum loop area is formed when return current flows just under the positive current route in the ground plane, if the ground plane is intact under the route.
    • For high frequency the copper area capacitance must be taken into account. For example, the copper area for the drain of boost N-MOSFET is a tradeoff between capacitance and the cooling capacity of the components.
  • GND plane must be intact under the high-current-boost traces to provide shortest possible return path and smallest possible current loops for high frequencies.
  • Route boost output voltage (VOUT) to LEDs, FB pin & Discharge pin after output capacitors not straight from the diode cathode.
  • FB network should be placed as close as possible to the FB pin, not near boost output
  • A small bypass capacitor (TI recommends a 39-pF capacitor) could be placed close to the FB pin and GND to suppress high frequency noise
  • VDD line must be separated from the high current supply path to the boost converter to prevent high frequency ripple affecting the chip behavior.
  • Capacitor connected to charge pump output CPUMP is recommended to have 10-µF capacitance. This capacitor must be as close as possible to CPUMP pin. This capacitor provides a greater peak current for gate driver and must be used even if the charge pump is disabled. If the charge pump is disabled, the VDD and CPUMP pins must be tied together.
  • Input and output capacitors need low-impedance grounding (wide traces with many vias to GND plane).
  • Input/output ceramic capacitors have DC-bias effect. If the output capacitance is too low, it can cause boost to become unstable under certain load conditions. DC bias characteristics should be obtained from the component manufacturer; DC bias is not taken into account on component tolerance.