SBVS237 March   2014 TLC5955

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Terminal Configurations and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Handling Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Switching Characteristics
    7. 6.7 Typical Characteristics
  7. 7 Parameter Measurement Information
    1. 7.1 Terminal-Equivalent Input and Output Schematic Diagrams
    2. 7.2 Test Circuits
    3. 7.3 Timing Diagrams
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Output Current Calculation
      2. 8.3.2 Register and Data Latch Configuration
        1. 8.3.2.1 769-Bit Common Shift Register
        2. 8.3.2.2 Grayscale (GS) Data Latch
        3. 8.3.2.3 Control Data Latch
        4. 8.3.2.4 Dot Correction (DC) Data Latch
        5. 8.3.2.5 Maximum Current (MC) Data Latch
        6. 8.3.2.6 Global Brightness Control (BC) Data Latch
        7. 8.3.2.7 Function Control (FC) Data Latch
      3. 8.3.3 Status Information Data (SID)
      4. 8.3.4 LED Open Detection (LOD)
      5. 8.3.5 LED Short Detection (LSD)
      6. 8.3.6 Noise Reduction
    4. 8.4 Device Functional Modes
      1. 8.4.1 Maximum Current Control (MC) Function
      2. 8.4.2 Dot Correction (DC) Function
      3. 8.4.3 Global Brightness Control (BC) Function
      4. 8.4.4 Grayscale (GS) Function (PWM Control)
        1. 8.4.4.1 Conventional PWM Control
        2. 8.4.4.2 Enhanced Spectrum (ES) PWM Control
        3. 8.4.4.3 Auto Display Repeat Function
        4. 8.4.4.4 Display Timing Reset Function
        5. 8.4.4.5 Auto Data Refresh Function
  9. 9 Applications and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Daisy-Chain Application
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 Step-by-Step Design Procedure
          2. 9.2.1.2.2 Maximum Current (MC) Data
          3. 9.2.1.2.3 Global Brightness Control (BC) Data
          4. 9.2.1.2.4 Dot Correction (DC) Data
          5. 9.2.1.2.5 Grayscale (GS) Data
          6. 9.2.1.2.6 Other Control Data
        3. 9.2.1.3 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 Device Support
      1. 12.1.1 Development Support
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    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 Applications and Implementation

9.1 Application Information

The device is a 48-channel, constant sink current, LED driver. This device is typically connected in series to drive many LED lamps with only a few controller ports. Output current control data and PWM control data can be written from the SIN input terminal. The PWM timing reference clock can be supplied from the GSCLK input terminal. Also, the LED open and short error flag can be read out from the SOUT output terminal. Furthermore, the device maximum GSCLK clock frequency is 33 MHz and can reduce flickering discernable by the human eye.

9.2 Typical Application

9.2.1 Daisy-Chain Application

In this application, the device VCC and LED lamp anode voltages are supplied from different power supplies.

ai_daisy_chain_app_bvs237.gifFigure 33. Multiple Daisy-Chained TLC5955 Devices

9.2.1.1 Design Requirements

For this design example, use the following as the input parameters.

Table 13. Design Parameters

DESIGN PARAMETER EXAMPLE VALUE
VCC input voltage range 3.0 V to 5.5 V
LED lamp (VLED) input voltage range Maximum LED forward voltage (VF) + 0.3 V (knee voltage)
SIN, SCLK, LAT, and GSCLK voltage range Low level = GND, High level = VCC

9.2.1.2 Detailed Design Procedure

9.2.1.2.1 Step-by-Step Design Procedure

To begin the design process, a few parameters must be decided upon. The designer needs to know the following:

  • Maximum output constant-current value for each color LED ramp.
  • Maximum LED forward voltage (VF).
  • Current ratio of red, green, and blue LED lamps for the best white balance.
  • Are the auto display repeat function, display timing reset function, or auto data refresh function used?
  • Which PWM control method is used: ES-PWM or conventional PWM?
  • Is the LED short detect (LSD) function used? If so, which detection level (70% VCC or 90% VCC) is used?

9.2.1.2.2 Maximum Current (MC) Data

There are a total of nine bits of MC data for the red, green, and blue LED ramp. Select the MC data to be greater than each LED ramp current and write the data with other control data.

9.2.1.2.3 Global Brightness Control (BC) Data

There are a total of three sets of 7-bit BC data for the red, green, and blue LED ramp. Select the BC data for the best white balance of the red, green, and blue LED ramp and write the data with other control data.

9.2.1.2.4 Dot Correction (DC) Data

There are a total of 48 sets of 7-bit DC data for each current adjustment. Select the DC data for the best uniformity of each color LED ramp and write the data with other control data.

9.2.1.2.5 Grayscale (GS) Data

There are a total of 48 sets of 16-bit GS data for the PWM control of each output. Select the GS data of the LED ramp intensity and color control and write the data with other GS data.

9.2.1.2.6 Other Control Data

There are five bits control data to set the function mode for the auto display repeat, display timing reset, auto data refresh, ES-PWM, and LSD functions explained in the Device Functional Modes section. Write the 5-bit control data for the appropriate operation of the display system with MC, BC, and DC data as the control data.

9.2.1.3 Application Curves

One LED connected to each output.

Scope_02_SBVS237.gif
MCX = 4 BCX = DCXn = 7Fh GSCLK = 33 MHz
VLED = 4.2 V VCC = 3.3 V DSPRPT = 1
TMGRST, RFRESH, ESPWM, LSDVLT = 0
Figure 34. Output Waveform Immediately After First GS Data Latch Input (GSXn = 0001h)
Scope_03_SBVS237.gif
MCX = 4 BCX = DCXn = 7Fh GSCLK = 33 MHz
VLED = 4.2 V VCC = 3.3 V DSPRPT = 1
TMGRST, RFRESH, ESPWM, LSDVLT = 0
Figure 35. Output Waveform Immediately After First GS Data Latch Input (GSXn = 7FFFh)