SLVSGD5 July   2021 LP5890

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Switching Characteristics
    8. 7.8 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Independent and Stackable Mode
        1. 8.3.1.1 Independent Mode
        2. 8.3.1.2 Stackable Mode
      2. 8.3.2 Current Setting
        1. 8.3.2.1 Brightness Control (BC) Function
        2. 8.3.2.2 Color Brightness Control (CC) Function
        3. 8.3.2.3 Choosing BC/CC for a Different Application
      3. 8.3.3 Frequency Multiplier
      4. 8.3.4 Line Transitioning Sequence
      5. 8.3.5 Protections and Diagnostics
        1. 8.3.5.1 Thermal Shutdown Protection
        2. 8.3.5.2 IREF Resistor Short Protection
        3. 8.3.5.3 LED Open Load Detection and Removal
          1. 8.3.5.3.1 LED Open Detection
          2. 8.3.5.3.2 Read LED Open Information
          3. 8.3.5.3.3 LED Open Caterpillar Removal
        4. 8.3.5.4 LED Short and Weak Short Circuitry Detection and Removal
          1. 8.3.5.4.1 LED Short and Weak Short Detection
          2. 8.3.5.4.2 Read LED Short Information
          3. 8.3.5.4.3 LSD Caterpillar Removal
    4. 8.4 Device Functional Modes
    5. 8.5 Continuous Clock Series Interface
      1. 8.5.1 Data Validity
      2. 8.5.2 CCSI Frame Format
      3. 8.5.3 Write Command
        1. 8.5.3.1 Chip Index Write Command
        2. 8.5.3.2 VSYNC Write Command
        3. 8.5.3.3 Soft_Reset Command
        4. 8.5.3.4 Data Write Command
      4. 8.5.4 Read Command
    6. 8.6 PWM Grayscale Control
      1. 8.6.1 Grayscale Data Storage and Display
        1. 8.6.1.1 Memory Structure Overview
        2. 8.6.1.2 Details of Memory Bank
        3. 8.6.1.3 Write a Frame Data into Memory Bank
      2. 8.6.2 PWM Control for Display
    7. 8.7 Register Maps
      1. 8.7.1  FC0
      2. 8.7.2  FC1
      3. 8.7.3  FC2
      4. 8.7.4  FC3
      5. 8.7.5  FC4
      6. 8.7.6  FC10
      7. 8.7.7  FC11
      8. 8.7.8  FC12
      9. 8.7.9  FC13
      10. 8.7.10 FC14
      11. 8.7.11 FC15
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
        1. 9.2.1.1 System Structure
        2. 9.2.1.2 SCLK Frequency
        3. 9.2.1.3 Internal GCLK Frequency
        4. 9.2.1.4 Line Switch Time
        5. 9.2.1.5 Blank Time Removal
        6. 9.2.1.6 BC and CC
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Chip Index Command
        2. 9.2.2.2 FC Registers Settings
        3. 9.2.2.3 Grayscale Data Write
        4. 9.2.2.4 VSYNC Command
        5. 9.2.2.5 LED Open and Short Read
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Receiving Notification of Documentation Updates
    2. 12.2 Support Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

9.2.1.5 Blank Time Removal

The LP5890 has an algorithm to distribute the blank time into each subperiod in order to prevent the black field when taking photos or video.

From Equation 3, 83.1-MHz GCLK frequency and 1.44-us line switch time, the calculated blank time is 1.0361 ms (86100 GCLK), which is too long and will bring black field.

Here are detailed steps of the algorithm:

Step1: Distribute blank time into each segment

When the blank GCLK number is larger than Nsub_period × Nscan_line, it can be distributed into each segment.

In this application, the blank GCLK number is 86100 and Nsub_period × Nscan_line is 960, so the distributed GCLK number in each segment is 86100/960 = 89...660. These 89 GCLKs can be used to increase PWM length or extend line switch time. If used to increase PWM length, the GCLK number in each segment will be 512 + 89 = 601, so the SEG_LENGTH (Bit9-0 in FC1 register) will be 1001011001b.

Step2: Distribute blank time into each sub-period

If the left GCLK number is larger than Nsub_period, it can be distributed into each sub-period.

In this application, the left GCLK is 600 and the distributed GCLK number in each sub-period is 600/32=18...24. The BLK_ADJ (Bit46-41 in FC1 register) is 010001b.

After distributing into each sub-period, the left GCLK number is 24, which is about 289 ns. This time is too short to bring black field.