Texas Instruments Incorporated AN-2062 User's Guide
1 General Description
The LM3549 is a high power LED driver with up to 700mA output current. It has three constant current
LED drivers and a buck boost SMPS for driving RGB LEDs with high efficiency. LED drivers are designed
for sequential drive so only one driver can be enabled at a time.
LED driver output current settings can be stored to integrated non-volatile memory which allows standalone operation without I2C interface. Non-volatile memory is re-writable so current setting can be changed
if needed.
LM3549 has a fault detection feature that can detect several different fault conditions. In case of a fault
error flags are set and FAULT output sends interrupt to control logic. Error flags can be read through I2C
interface.
Total brightness can be controlled with PWM input or with master fader register if I2C interface is used.
LM3549 evaluation board is designed to help getting familiarized with the LM3549. It can be used to
measure key parameters of the LM3549 and to speed up design in of the device. The evaluation board
has a microcontroller that acts as an USB to I2C interface. Microcontroller is also used to manipulate the
digital control signals of the LM3549. LM3549 evaluation board can be powered from the USB interface or
from external power supply. If evaluation board is used to measure the electrical parameters of the
LM3549 or used with high output currents external power supply needs to be used. If evaluation board is
used to check the functionality of the LM3549 with small output currents or to support software
development it can be powered directly from USB interface. This document describes how to get the
LM3549 evaluation board up and running and how to use evaluation software.
User's Guide
SNVA443A–August 2010–Revised April 2013
AN-2062 LM3549 Evaluation Kit
2 What Is Needed
To get started you will need:
• LM3549 evaluation board
• LM3549 evaluation software (LM3549.exe)
• USB cable
• PC with one free USB port
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SNVA443A–August 2010–Revised April 2013 AN-2062 LM3549 Evaluation Kit
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What Is Needed
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Figure 1. Evaluation Board
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AN-2062 LM3549 Evaluation Kit SNVA443A–August 2010–Revised April 2013
Copyright © 2010–2013, Texas Instruments Incorporated
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3 Hardware Set-Up
Hardware Set-Up
Figure 2. LM3549 Evaluation Board Setup
The LM3549 evaluation kit is based on a one board system, where the USB communication and
evaluation related components are assembled onto one board, (see Figure 2). The evaluation board was
designed especially for evaluation and, therefore, is not optimized for the smallest layout size. The
components are physically large to make changing component values easier.
LM3549 input voltage VDD can be supplied from the USB port or by connecting an external power supply
to the X1 connector. If voltage is supplied from USB port shunt needs to be placed on the VDD position of
P2 pin rail. If external power supply is used this shunt needs to be removed. USB port's maximum output
current is 500mA. This is not enough to drive the LEDs with maximum output current but can be used to
test functionality of the LM3549.
Figure 2 shows how to setup the LM3549 evaluation board. This configuration uses onboard
microcontroller to control the LM3549’s logic inputs. If one wishes to use external source to drive the
control signals, control signal jumpers needs to be removed and external control signals needs to be
connected to the right side of the P2 pin rail. Control signals are labeled for easy connection.
I2C interface pull-up resistors are placed on the microcontroller side of the control signal jumpers. If
external I2C interface is connected to the board it needs to have pull-up resistors. LM3549 I2C ID is 36h
(in 7bit format) -> write = 6Ch (8-bit format) and read = 6Dh (8-bit format)
SNVA443A–August 2010–Revised April 2013 AN-2062 LM3549 Evaluation Kit
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Copyright © 2010–2013, Texas Instruments Incorporated
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