SNVSCC9B November   2023  – December 2024 LP5812

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  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 Timing Requirements
    7. 6.7 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 Time-Cross-Multiplexing (TCM) Scheme
        1. 7.3.1.1 Direct drive mode
        2. 7.3.1.2 TCM Drive Mode
        3. 7.3.1.3 Mix drive mode
        4. 7.3.1.4 Ghosting Elimination
      2. 7.3.2 Analog Dimming
      3. 7.3.3 PWM Dimming
      4. 7.3.4 Autonomous Animation Engine Control
        1. 7.3.4.1 Animation Engine Pattern
        2. 7.3.4.2 Sloper
        3. 7.3.4.3 Animation Engine Unit (AEU)
        4. 7.3.4.4 Animation Pause Unit (APU)
      5. 7.3.5 Protections and Diagnostics
        1. 7.3.5.1 LED Open Detections
        2. 7.3.5.2 LED Short Detections
        3. 7.3.5.3 Thermal Shutdown
    4. 7.4 Device Functional Modes
    5. 7.5 Programming
    6. 7.6 Register Maps
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Application
      2. 8.2.2 Design Parameters
      3. 8.2.3 Detailed Design Procedure
        1. 8.2.3.1 Input Capacitor Selection
        2. 8.2.3.2 Program Procedure
        3. 8.2.3.3 Programming Example
      4. 8.2.4 Application Performance Plots
    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 Documentation Support
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

7.3.1 Time-Cross-Multiplexing (TCM) Scheme

The LP5812 integrates 4 high-side PMOS scan switches and 4 constant current sinks. Each OUTx (x = 0, 1, 2, 3) has 1 PMOS scan switch and 1 constant current sink. The source of PMOS switches are connected to VCC. During normal operation at default setting, the switches turn on sequentially from OUT0 to OUT3. At the same time, only one OUT is selected working as switch, the other 3 OUTs act as constant current sink. Thus a 4×3 matrix is formed with ¼ multiplexing ratio. The scanning order of OUTs can be configured in 'Dev_config_2' register

Figure 7-2 Time-cross-multiplexing (TCM) Scheme
LP5812

Figure 7-2 shows the simplified TCM scheme timing diagram of the four outputs. A complete display frame includes 4 sub-periods. Each sub-period contains dimming period and blank time period. In switching period, 1 output is selected as switch and the other 3 OUTs are selected as current sinks. Blank time is applied between two adjacent switching periods for ghosting elimination.

One sub-period cycle time Tsub is calculated as Equation 1:

Equation 1. T s u b = T d i m + T b l a n k

  • Tdim is the scan switch on-time for one switching cycle, which equals to one PWM cycle 42μs (PWM frequency set as 24kHz) or 84μs (PWM frequency set as 12kHz).
  • Tblank is blank time is applied between two adjacent dimming periods, which is from 1 μs to 2μs selected by 'Blank_Time' bits in Dev_Config11 Register.

One complete frame time Tframe is calculated as Equation 2:

Equation 2. T f r a m e = T s u b × S c a n   #

  • Scan # is the total scan switches count.

The LP5812 can be configured to direct-drive mode, TCM-drive mode and mix-drive mode by the 'led_mode' bits in 'Dev_Config_1' register. The mix-drive mode contains both direct drive mode and TCM-drive mode for different outputs. With this method, the LP5812 can provide the maximum flexibility for LED configurations of LED average current, LED count, and PCB layouts.