SNVSC36A December   2021  – September 2024 LP5866

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.     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)
      3. 7.3.3 PWM 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
    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 Requirements
      3. 8.2.3 Detailed Design Procedure
        1. 8.2.3.1 Program Procedure
      4. 8.2.4 Application Performance Plots
    3. 8.3 Power Supply Recommendations
      1. 8.3.1 Power Supply Recommendations
      2. 8.3.2 Power Supply Recommendations
      3. 8.3.3 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 Receiving Notification of Documentation Updates
    2. 9.2 Support Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

7.3.2 Analog Dimming (Current Gain Control)

Analog dimming of LP5866 is achieved by configuring the current gain control. There are several methods to control the current gain of each LED.

  • Global 3-bits Maximum Current (MC) setting without external resistor
  • 3 groups of 7-bits Color Current (CC) setting
  • Individual 8-bit Dot Current (DC) setting
Global 3-Bits Maximum Current (MC) Setting

The MC is used to set the maximum current IOUT_MAX for each current sink and this current is the maximum peak current for each LED dot. The MC can be set with 3 bits (8 steps) from 3 mA to 50 mA. When the device is powered on, the MC data is set to default value, which is 15 mA.

For data refresh Mode 1, MC data is effective immediately after new data is updated. For Mode 2 and Mode 3, to avoid unexpected MC data change during high speed data refreshing, MC data must be changed when all channels are off and new MC data is only be updated when the 'Chip_EN' bit in Chip_en register is set to 0, and after the 'Chip_EN' returns to 1, the new MC data is effective. 'Down_Deghost' and 'Up_Deghost' in Dev_config3 work in the similar way with MC.

Table 7-1 Maximum Current (MC) Register Setting
3-BITS MAXIMUM_CURRENT REGISTER IOUT_MAX
Binary Decimal mA
000 0 3
001 1 5
010 2 10
011 (default) 3 (default) 15 (default)
100 4 20
101 5 30
110 6 40
111 7 50
3 Groups of 7-Bits Color Current (CC) Setting

The LP5866 device can adjust the output current of three color groups separately. For each color, the device has 7-bits data in 'CC_Group1', 'CC_Group2', and 'CC_Group3'. Thus, all color group currents can be adjusted in 128 steps from 0% to 100% of the maximum output current, IOUT_MAX.

The 18 current sinks have fixed mapping to the three color groups:

  • CC-Group 1: CS0, CS3, CS6, CS9, CS12, CS15.
  • CC-Group 2: CS1, CS4, CS7, CS10, CS13, CS16.
  • CC-Group 3: CS2, CS5, CS8, CS11, CS14, CS17.

Table 7-2 3 Groups of 7-bits Color Current (CC) Setting
7-BITS CC_GROUP1/CC_GROUP2/CC_GROUP3 REGISTERRATIO OF OUTPUT CURRENT TO IOUT_MAX
BinaryDecimal%
000 000000
000 000110.79
000 001021.57
- - -- - -- - -
100 0000 (default)64 (default)50.4 (default)
- - -- - -- - -
111 110112598.4
111 111012699.2
111 1111127100
Individual 8-bit Dot Current (DC) Setting
The LP5866 can individually adjust the output current of each LED by using dot current function through DC setting. The device allows the brightness deviations of the LEDs to adjusted be individually. Each output DC is programmed with a 8-bit depth, so the value can be adjusted with 256 steps within the range from 0% to 100% of (IOUT_MAX × CC/127).

Table 7-3 Individual 8-bit Dot Current (DC) Setting
8-BIT DC REGISTER RATIO OF OUTPUT CURRENT TO IOUT_MAX × CC/127
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

In summary, the current gain of each current sink can be calculated as below:

Equation 3. IOUT (mA) = IOUT_MAX × (CC/127) × (DC/255)

For time-multiplexing scan scheme, if the scan number is N, each LED dot average current IAVG is shown as below:

Equation 4. IAVG (mA) = IOUT / N = IOUT_MAX × (CC/127) × (DC/255) / N