ST AN2415 Application note

AN2415

Application note

Using the output detection feature of the high-brightness

LED driver STP08CDC596 evaluation board

Introduction

This document describes how to implement a complete solution for driving a high-brightness LED array. Based on STP08CDC596 drivers and controlled by an ST7FLITE3x microcontroller, there are two versions of the evaluation board:

■ STEVAL-ILL002V1 using OSRAM LEDs

■ STEVAL-ILL002V2 using Toshiba LEDs

Note: The STP08CDC596 LED driver is replaced by the new, higher performing STP08DP05 LED

driver. The two available versions of the evaluation board with the STP08DP05 replace the STEVAL-ILL002V1 and the STEVAL-ILL002V2, and are described in application note AN2478.

The new boards available are:

■ STEVAL-ILL002V3 using OSRAM LEDs

■ STEVAL-ILL002V4 using VISHAY LEDs

Forty high-brightness LEDs are arranged on the board in a 5x8 matrix. The matrix is driven by five 8-channel STP08CDC596 drivers.

The main features of the evaluation board are:

■ Brightness and blinking regulation

■ Animated text

■ Error detection on output

■ GUI (graphic user interface)

■ DC-DC converter

The innovative feature of the STP08CDC596 is the full output error detection function which enables output status checking without invasive testing (via software only).

Figure 1. STEVAL-ILL002Vx evaluation board

For more information about other boards based on the STPxxC/L596 driver family, refer to application note AN2141 which provides details concerning the basic features of the driver family, the microcontroller interface and chip power dissipation. Refer to user manual UM0181 for information about how to get started using the evaluation boards.

August 2007 Rev 4 1/11

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Contents AN2415

Contents

1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2 Operation mode switching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.1 Normal mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.2 Error detection mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3 Firmware implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3.1 Timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3.2 Option byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3.3 GUI features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

4 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

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AN2415 List of figures

List of figures

Figure 1. STEVAL-ILL002Vx evaluation board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Figure 2. STEVAL-ILL002Vx evaluation board block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Figure 3. Error Detection mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Figure 4. Normal mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Figure 5. Timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Figure 6. MCU option bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Figure 7. LED matrix board application diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

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Overview AN2415

1 Overview

The STEVAL-ILL002Vx evaluation board can be powered with voltages from 7 V up to 32 V. The SMPS DC-DC converter block is based on the L5970D step-down switching regulator and the DC-DC block is based on the LE50ABD voltage regulator. The power topology makes it possible to power the board using a laptop power supply.

Figure 2 shows the block diagram of the evaluation board.

Figure 2. STEVAL-ILL002Vx evaluation board block diagram

SMP

Power Supply

DC/DC

LED M atrix

……

Control Panel

8-bit µC

RS232 Driver

LED Driver

SPI

…….

The brain of the board is the 8-bit ST7FLITE39 microcontroller. It receives inputs from the control panel, sends and receives data from the LED drivers through the serial peripheral interface (SPI) and enables PC communication through the serial communications interface (SCI). The control panel consists of switches, potentiometers and jumpers. Switches are used to reset the microcontroller and to enter Detection mode. Potentiometers change the brightness and text speed. Jumpers are used to simulate errors (open and short circuit) on the LED matrix.

A LED matrix consists of 40 LEDs arranged in a 5x8 matrix. A dedicated PC GUI displays the status of the LEDS.

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