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

Package Options

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

6.3.2 Analog Dimming

The current gain of each LED can be controlled by 2 methods to achieve analog dimming in the LP5811.

  • Global 1-bit Maximum Current (MC) control for all LEDs without external resistor
  • Individual 8-bit Dot Current (DC) control for each LED

The maximum output current IOUT_max of each current sink can be programmed by the 1-bit max_current. The default value of max_current is 0h, which means the LED maximum current is set to 25.5mA in default.

Table 6-1 Maximum Current (MC) Bit Setting
1 bit Maximum Current (MC) IOUT_MAX (mA)
Binary Decimal
0 (default) 0 (default) 25.5 (default)
1 1 51

The LP5811 can individually adjust the peak current of each LED by using Dot Current (DC) function. The brightness deviation among the LED bins can be miminized, to achieve uniform display performance. The current is adjusted with 256 steps from 0 to 100% of IOUT_MAX., which is programmed in an 8-bit register whose default value is 80h.

Table 6-2 Dot Current (DC) Bits Setting
8-bits Dot Current (DC) Register Ratio of IOUT_MAX
Binary Decimal
0000 0000 0 0%
0000 0001 1 0.39%
0000 0010 2 0.78%
--- --- ---
1000 0000 (default) 128 (default) 50.2% (default)
--- --- ---
1111 1101 253 99.2%
1111 1110 254 99.6%
1111 1111 255 100%

By configuring the MC and DC, the peak current of each current sink can be calculated as Equation 4:

Equation 4. I O U T   ( m A ) = I O U T _ m a x × D C 255

The average current of each LED in TCM drive mode and mix drive mode is shown as Equation 5:

Equation 5. I A V E   ( m A ) = I O U T N × D C 255 × D P W M

  • N is the total scan number setting.
  • DPWM is the PWM duty.