SLVS515D December   2004  – November 2015 TLC5940

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 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 Switching Characteristics
    7. 6.7 Typical Characteristics
  7. 7 Parameter Measurement Information
    1. 7.1 Test Parameter Equations
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Serial Interface
      2. 8.3.2 Error Information Output
      3. 8.3.3 TEF: Thermal Error Flag
      4. 8.3.4 LOD: LED Open Detection
      5. 8.3.5 Delay Between Outputs
      6. 8.3.6 Output Enable
      7. 8.3.7 Setting Maximum Channel Current
    4. 8.4 Device Functional Modes
      1. 8.4.1 Operating Modes
      2. 8.4.2 Setting DOT Correction
      3. 8.4.3 Setting Grayscale
      4. 8.4.4 Status Information Output
      5. 8.4.5 Grayscale PWM Operation
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Serial Data Transfer Rate
        2. 9.2.2.2 Grayscale (GS) Data
      3. 9.2.3 Application Curve
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
    3. 11.3 Power Dissipation Calculation
  12. 12Device and Documentation Support
    1. 12.1 Community Resources
    2. 12.2 Trademarks
    3. 12.3 Electrostatic Discharge Caution
    4. 12.4 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

9 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

9.1 Application Information

The device is a 16-channel, constant sink current, LED driver. This device can be connected in series to drive many LED lamps with only a few controller ports. Output current control data, dot correction data and PWM control data can be written from the SIN input terminal.

9.2 Typical Application

TLC5940 cascad_lvs515.gif Figure 22. Cascading Devices

9.2.1 Design Requirements

For this design example, use the input parameters shown in Table 4.

Table 4. Design Parameters

PARAMETERS VALUES
VCC input voltage range 3.0 V to 5.5 V
LED lamp (VLED) input voltage range >Maximum LED forward voltage (VF) + IC knee voltage
SIN, SCLK, XLAT, GSCLK, and BLANK voltage range Low level = GND, High level = VCC

9.2.2 Detailed Design Procedure

9.2.2.1 Serial Data Transfer Rate

Figure 22 shows a cascading connection of n TLC5940 devices connected to a controller, building a basic module of an LED display system. The maximum number of cascading TLC5940 devices depends on the application system and is in the range of 40 devices. Equation 9 calculates the minimum frequency needed:

Equation 9. TLC5940 q_f_gsclk_lvs515.gif

where

  • f(GSCLK): minimum frequency needed for GSCLK
  • f(SCLK): minimum frequency needed for SCLK and SIN
  • f(update): update rate of whole cascading system
  • n: number cascaded of TLC5940 device

9.2.2.2 Grayscale (GS) Data

There are a total of 16 sets of 12-bit GS data for the PWM control of each output. Select the GS data of each LED lamp and write the GS data to the register following the signal timing.

9.2.3 Application Curve

TLC5940 waveform_lvs515-2.png Figure 23. Output Waveform with Different Grayscale PWM Data