LM3549

LM3549 Evaluation Kit LM3549 Evaluation Kit National Semiconductor Application Note 2062 Anssi Raisanen August 6, 2010 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 stand-alone operation without I2C interface. Non-volatile memory is rewritable 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 powersupply needs to be used. If evalution 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. 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 30125042 FIGURE 1. AN-2062 © 2010 National Semiconductor Corporation 301250 www.national.com AN-2062 Hardware Set-up 30125025 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) The onboard microcontroller has USB interface to communicate with PC. Connect evaluation board to PC with USB cable. Evaluation software is used to control LM3549’s logic inputs and to use the I2C interface. Evaluation software setup and use are described in the following chapters. LM3549 evaluation board has three high current LEDs. These LED's are very bright even with minimum current setting. Never look straight into the LEDs. This can damage your eyes!It is good practice to always cover the LEDs with something to avoid looking straight into them. CONNECTOR LISTING • J1 - USB connector. Use this to connect the LM3549 to your PC. • VIO - selector for digital logic levels. There should be a shunt in 3.3V position. • X1- power supply connector. VDD terminal can be used to supply LM3549 input voltage from external power supply. VIOX terminal can be used to connect external voltage for the digital signals. • Connector for microcontroller programming is used to program the on-board microcontroller. This has no user functions and needs to always be unconnected. www.national.com 2 AN-2062 • • • P2 - P2 pin rail is used to connect on-board microcontroller to LM3549 digital lines. If user want to connect LM3549 to his/her own system shunts can be removed and user system can be connected to right side pins of the P2 pin rail. J3, J4 and J5 - LED disconnecting jumpers. These can be used to disconnect the LEDs from LM3549 LED outputs. This can be used to test the fault detection or to measure LED currents. P1 - Connector for VOUT and LED outputs. This can be used to connect external LEDs to the LM3549 evaluation board. 2. 3. 4. 5. 6. Connecting the Evaluation Board to a Computer 1. Check that the jumpers on the evaluation board are on wanted positions. 7. Connect external power supply to the evaluation board or, if evaluation board is to be powered form USB port, set shunt to VDD position of the P2 pin rail. Connect the USB board to your computer using a USB cable Start the evaluation software LM3549.exe Evaluation software may prompt you to update firmware of the LM3549 evaluation board. If it does click ok and wait until update is completed. Status bar at the center of the bottom row should say "OK" on green background. This indicates that I2C interface between microcontroller and LM3549 is working correctly. The evaluation kit is now fully up and running and the device can be controlled through the PC software. Figure 3 shows the evaluation software user interface (Control Panel). 30125001 FIGURE 3. LM3549 Evaluation Software Control Panel You should see USB OK message on the status bar (shown in the lower part of the window). If the USB communication is not working correctly, shut down the evaluation software and unplug the USB cable. Plug in the USB cable again and wait about 5 seconds and restart the evaluation software. You can also try toggling the Enable button few times. 3 www.national.com AN-2062 Controlling the Evaluation Board Evaluation software doesn’t need installation and can be run by double clicking the icon. If evaluation board is set up correctly evaluation software’s user interface should look like in Figure 3. When software starts up it sets Enable control to “1” and reads the control register values. Status bar at the center of the bottom row should say OK on green background. This indicates that I2C interface between microcontroller and LM3549 is working correctly. If there are any error messages on red background something is wrong with the I2C interface. In this case check the control signal jumpers and verify that proper VDD voltage is applied to the board. The evaluation software provides read-write control over the registers within the LM3549. Bits can be set from a logical '1' to a logical '0' or vice versa by a mouse click and for some settings there is a slider control. 30125019 FIGURE 4. I2C Log View Figure 4 shows the I2C Log tab of the evaluation software. All I2C write commands will be logged and can be seen on I2C Log tab. User can copy/paste write commands into his/her own application if needed. I2C COMMUNICATION LM3549 registers 00h-16h and 19h – 1Ah are read/write accessible using controls (buttons and track bars where available) on System tab of the software window. Register 17h (Fault register) is read only register. Button ReadAll reads all register values of the LM3549 and updates register map related buttons and track bars according to results. Note that www.national.com 4 ReadAll button doesn't update external pin buttons. Button WriteAll stores values of buttons and track bars to LM3549. Note that specific register will be updated immediately when clicking/dragging on its control buttons or track bar if Auto Write checkbox is checked. I2C communication status after register read or write command are shown on status bar (at bottom of window). DIRECT ACCESS TO REGISTERS Controls on the frame Direct Access allows user to read/write from/to the chip registers manually. Enter the register address to the Addr field and choose the binary value by clicking on AN-2062 the Data bits 7...0 and write the selected value to the chip register by clicking on the Store button. Note that after clicking the Store button all the register values will be read back automatically. Disable the automatic read by unchecking Auto Write checkbox. Enter register address to the Addr field and click the Read button to read the specific register. Result will be displayed in the Data field in binary format. CONTROL SIGNALS Buttons Enable, R_EN, G_EN, B_EN and PWM are used to manipulate input pins of the LM3549. Button Fault Status is used to read status of FAULT pin. Pin value appears to value bar beside the button. Setting Enable button high puts LM3549 to standby mode. I2C registers can be read and written in standby mode but buck-boost converter and LED drivers are off. Setting Enable button low sets LM3549 to shutdown mode. When device is on the standby mode LEDs can be turned on one at the time by clicking R_EN, G_EN or B_EN. Even if two or more buttons are turned high at the same time, only the LED that was set high first will be on. Generation of special sequence of R, G and B signals can be enabled/disabled by checking/unchecking Enable sequence checkbox. Period of the sequence is about 60 Hz and is similar to that described in the LM3549 Datasheet. Note that clicking on one of the R_EN, G_EN, B_EN button will disable sequence generation automatically. PWM generation can be enabled by dragging PWM track bar on bottom of the window. PWM frequency is about 7.6kHz. EEPROM PROGRAMMING Desired default register values can be stored to EEPROM. These values are always read back to registers when Enable button is set from low to high. Keep the Enable button on and set all x_EN buttons off and uncheck Enable sequence box. Write suitable values to all user registers. Set VDD to 5.0V and click on the Store User Registers to EEPROM button. Set the Enable button off and back to on. Read all registers by pressing the ReadAll button and verify that the values match with the stored values. FAULT LED LED D4 is connected to LM3549's open drain fault output. If LM3549 detects any fault conditions e.g. LED short or LED open it pulls the fault output low and turns on the fault LED. LM3549 has a fault register which indicates what fault has occurred. Reading the fault register reset it's state and also reset the fault output to high-z state. Different fault conditions are described in the LM3549 datasheet. 5 www.national.com AN-2062 www.national.com 30125023 Schematic 6 FIGURE 5. Schematic of the LM3549 Evaluation Board AN-2062 Bill of Materials Designator C1, C4 C2, C7 C3 C5 C6 D1 D2 D3 D4 D5 FB1 L1 R1 R2, R3, R4, R5 R6 R7 U1 U2 10 μF 100 nF 4.7 μF 22 μF 4.7 μF LR W5AP LT W5AP LD W5AP LS L296 BAT760 BK2125HS101-T 2.2 μH 10 kΩ 1.5 kΩ 330Ω 0Ω LM3549 C8051F326 0603 0603 0603 0805 LLP24 QFN-28 Microcontroller 2125 Ferrite bead Resistor Resistor Resistor Resistor 0603 LED Value Footprint 0805 0805 0805 1210 0603 Comment Capacitor Capacitor Capacitor Capacitor Capacitor Red LED Green LED Blue LED Red LED Osram Diamond Dragon LED Osram Diamond Dragon LED Osram Diamond Dragon LED Schotky diode Description Quantity 2 2 1 1 1 1 1 1 1 1 1 4 1 1 1 1 Fault indicator LED 1 VLF4014ST-2r2M1R9 TDK SMD inductor 1 7 www.national.com LM3549 Evaluation Kit Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Amplifiers Audio Clock and Timing Data Converters Interface LVDS Power Management Switching Regulators LDOs LED Lighting Voltage References PowerWise® Solutions Temperature Sensors PLL/VCO www.national.com/amplifiers www.national.com/audio www.national.com/timing www.national.com/adc www.national.com/interface www.national.com/lvds www.national.com/power www.national.com/switchers www.national.com/ldo www.national.com/led www.national.com/vref www.national.com/powerwise WEBENCH® Tools App Notes Reference Designs Samples Eval Boards Packaging Green Compliance Distributors Quality and Reliability Feedback/Support Design Made Easy Design Support www.national.com/webench www.national.com/appnotes www.national.com/refdesigns www.national.com/samples www.national.com/evalboards www.national.com/packaging www.national.com/quality/green www.national.com/contacts www.national.com/quality www.national.com/feedback www.national.com/easy www.national.com/solutions www.national.com/milaero www.national.com/solarmagic www.national.com/training Applications & Markets Mil/Aero PowerWise® Design University Serial Digital Interface (SDI) www.national.com/sdi www.national.com/wireless www.national.com/tempsensors SolarMagic™ THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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