JAJSTC8A February   2024  – April 2024 LP5867

PRODUCTION DATA  

  1.   1
  2. 1 特長
  3. 2 アプリケーション
  4. 3 概要
  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.     14
    8. 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-Multiplexing Matrix
      2. 7.3.2 Analog Dimming (Current Gain Control)
        1. 7.3.2.1 Global 3-Bits Maximum Current (MC) Setting
        2. 7.3.2.2 3 Groups of 7-Bits Color Current (CC) Setting
        3. 7.3.2.3 Individual 8-bit Dot Current (DC) Setting
      3. 7.3.3 PWM Dimming
        1. 7.3.3.1 Individual 8-Bit / 16-Bit PWM for Each LED Dot
        2. 7.3.3.2 Programmable Groups of 8-Bit PWM Dimming
        3. 7.3.3.3 8-Bit PWM for Global Dimming
      4. 7.3.4 ON and OFF Control
      5. 7.3.5 Data Refresh Mode
      6. 7.3.6 Full Addressable SRAM
      7. 7.3.7 Protections and Diagnostics
        1. 7.3.7.1 LED Open Detection
        2. 7.3.7.2 LED Short Detection
        3. 7.3.7.3 Thermal Shutdown
        4. 7.3.7.4 UVLO (Under Voltage Lock Out)
    4. 7.4 Device Functional Modes
    5. 7.5 Programming
      1. 7.5.1 Interface Selection
      2. 7.5.2 I2C Interface
        1. 7.5.2.1 I2C Data Transactions
        2. 7.5.2.2 I2C Data Format
        3. 7.5.2.3 Multiple Devices Connection
      3. 7.5.3 Programming
        1. 7.5.3.1 SPI Data Transactions
        2. 7.5.3.2 SPI Data Format
        3. 7.5.3.3 Multiple Devices Connection
    6. 7.6 Register Maps
  9. 8 Register Maps
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Application
      2. 9.2.2 Design Requirements
      3. 9.2.3 Detailed Design Procedure
        1. 9.2.3.1 Program Procedure
      4. 9.2.4 Application Performance Plots
    3. 9.3 Power Supply Recommendations
      1. 9.3.1 VDD Input Supply Recommendations
      2. 9.3.2 VLED Input Supply Recommendations
      3. 9.3.3 VIO Input Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 ドキュメントの更新通知を受け取る方法
    2. 10.2 サポート・リソース
    3. 10.3 Trademarks
    4. 10.4 静電気放電に関する注意事項
    5. 10.5 用語集
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

7.3.3.3 8-Bit PWM for Global Dimming

The Global PWM Control function affects all LEDs simultaneously.

The final PWM duty cycle can be calculated as below:

Equation 5. PWM_Final(8-bit) = PWM_Individual(8-bit) × PWM_Group(8-bit) × PWM_ Global(8-bit)
Equation 6. PWM_Final(16-bit) = PWM_Individual(16-bit) × PWM_Group(8-bit) × PWM_ Global(8-bit)

The LP5867 supports 125kHz or 62.5kHz PWM output frequency. The PWM frequency is selected by configuring the 'PWM_Fre' in Dev_initial register. An internal 32MHz oscillator is used for generating PWM outputs. The oscillator’s high accuracy design (ƒOSC_ERR ≤ ± 3%) enables a better synchronization if multiple LP5867 devices are connected together.

A PWM phase-shifting scheme is implemented in each current sink to avoid the current overshot when turning on simultaneously. As the LED drivers are not activated simultaneously, the peak load current from the pre-stage power supply is significantly decreased. This scheme also reduces input-current ripple and ceramic-capacitor audible ringing. LED drivers are grouped into three different phases. By configuring the 'PWM_Phase_Shift' in Dev_config1 register, which is default off, the LP5867 supports tphase_shift = 125ns shifting time shown in Figure 7-4.

  • Phase 1: CSR0, CSR1.
  • Phase 2: CSG0, CSG1.
  • Phase 3: CSB0, CSB1.
LP5867 Phase ShiftFigure 7-4 Phase Shift

To avoid high current sinks output ripple during line switching, current sinks can be configured to turn on with 1 clock delay (62.5ns or 31.25ns according to the PWM frequency) after lines turn on, as shown in Figure 7-3. This function can be configured by 'CS_ON_Shift' in Dev_config1 register.

The LP5867 allows users to configure the dimming scale either exponentially (Gamma Correction) or linearly through the 'PWM_Scale_Mode' in Dev_config1 register. If a human-eye-friendly dimming curve is desired, using the internal fixed exponential scale is an easy approach. If a special dimming curve is desired, using the linear scale with software correction is recommended. The LP5867 supports both linear and exponential dimming curves under 8-bit and 16-bit PWM depth. Figure 7-5 is an example of 8-bit PWM depth.

LP5867 Linear and Exponential Dimming CurvesFigure 7-5 Linear and Exponential Dimming Curves

In summary, the PWM control method is illustrated as Figure 7-6:

LP5867 PWM Control SchemeFigure 7-6 PWM Control Scheme