SBVS114B July   2008  – January 2015 TLC5947

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 Dissipation Ratings
    6. 6.6 Electrical Characteristics
    7. 6.7 Switching Characteristics
    8. 6.8 Typical Characteristics
  7. 7 Parameter Measurement Information
    1. 7.1 Pin Equivalent Input and Output Schematic Diagrams
    2. 7.2 Test Circuits
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Grayscale (GS) Control Function
      2. 8.3.2 Auto Display Repeat Function
      3. 8.3.3 Thermal Shutdown (TSD)
      4. 8.3.4 Noise Reduction
    4. 8.4 Programming
      1. 8.4.1 Register Configuration
  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 Define Basic Parameters
        2. 9.2.2.2 Grayscale (GS) Data
        3. 9.2.2.3 Auto-Display Function
        4. 9.2.2.4 Setting for the Constant Sink Current Value
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
    3. 11.3 Power Dissipation
  12. 12Device and Documentation Support
    1. 12.1 Trademarks
    2. 12.2 Electrostatic Discharge Caution
    3. 12.3 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 24-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 and PWM control data can be written from the SIN input terminal. The PWM timing reference clock can be supplied from the internal oscillation.

9.2 Typical Application

fbd_pg1_bvs114.gifFigure 23. Typical Application Circuit (Multiple Daisy Chained TLC5947s)

9.2.1 Design Requirements

For this design example, use Table 2 as the input parameters.

Table 2. Design Parameters

DESIGN PARAMETER EXAMPLE VALUE
VCC input voltage range 3 V to 5.5 V
LED lamp (VLED) input voltage range Maximum LED forward voltage (VF) + IC knee voltage
SIN, SCLK, LAT, and BLANK voltage range Low level = GND, High level = VCC

9.2.2 Detailed Design Procedure

9.2.2.1 Define Basic Parameters

To begin the design process, a few parameters must be decided as following:

  • Maximum output constant-current value for each color LED lamp
  • Maximum LED forward voltage (VF)
  • Are auto display function used

9.2.2.2 Grayscale (GS) Data

There are a total of 24 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.

9.2.2.3 Auto-Display Function

There are a total of 24 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.

9.2.2.4 Setting for the Constant Sink Current Value

The constant-current value for all channels is set by an external resistor (RIREF) placed between IREF and GND. The resistor (RIREF) value is calculated by Equation 2.

Equation 2. q_riref_bvs114.gif

where

  • VIREF = the internal reference voltage on the IREF pin (typically 1.20 V).

IOLC must be set in the range of 2 mA to 30 mA. The constant sink current characteristic for the external resistor value is shown in Figure 4. Table 3 describes the constant-current output versus external resistor value.

Table 3. Constant-Current Output versus External Resistor Value

IOLC (mA, Typical) RIREF (Ω)
30 1640
25 1968
20 2460
15 3280
10 4920
5 9840
2 24600

9.2.3 Application Curves

appcurve1.pngFigure 24. Output Waveform with GS Data Latch Input
appcurve2.pngFigure 25. Output Waveform without GS Data Latch Input