User’s Guide August 2012 LP8556TM-EVM User’s Guide CONTENTS LIST OF FIGURES ............................................................................................................. 2 LIST OF TABLES ............................................................................................................... 2 August 2012 1. INTRODUCTION ......................................................................................................... 3 2. SETUP ............................................
Setup 7. LP8556 USAGE AND PROGRAMMING .................................................................. 14 7.1. IN CIRCUIT OPERATION ...................................................................................... 14 7.2. ENABLE AND STANDBY ...................................................................................... 14 7.3. BOOST CONVERTER CONFIGURATION ............................................................ 15 7.4. LED DRIVER CONFIGURATION....................................
Setup 1. Introduction The Texas Instruments LP8556TM-EVM evaluation module (EVM) helps designers evaluate the operation and performance of the LP8556 High-Efficiency LED Backlight Driver. The device offers configurability and can be setup to switch at 312.5 kHz, 625 kHz and 1.25 MHz. The EVM contains one LED Driver (See Table 1).
Setup 2. Setup This section describes the jumpers and connectors on the EVM as well and how to properly connect, set up and use the LP8556TM-EVM. For a quicker way to enabling the LEDs refer to the LP8556TM-EVM Quick Start document. 2.1. Input / Output Connector Description VIN_B – Input is the power input terminal for the boost converter. The terminal provides a power (Vbat) connection to allow the user to attach the EVM to a power supply via a cable assembly with banana plugs.
Setup 2.2. Test Setup Figure 2 shows the picture of the LP8556TM-EVM board in the setup with the USB-I2C Interface Board and LED Board.
Setup 2.3. LP8556TM-EVM Setup Figures 3 and 4 illustrate how to properly configure the LP8556TM-EVM. Current sense GND VDDIO resistors (0.5W ) 1.62V to 3.6V are optional. Install 0W VIN 2.7V to 20V To connect VIN to VDD install jumper as shown Termination resistor (50W ) is optional Install ISET resistor at R3 (24.3 kW ) if ISET_EN=1 I2C I/O Pull-up Select: Install jumper as shown LED current sense resistors (10W ) are optional Install jumpers as shown to bypass the LED current sense resistors .
2.4. LED Board Setup Figure 5 illustrates how to properly configure the LED Board.
2.5. Instructions The LP8556 evaluation kit includes an I2C compatible program and USB docking board that can help exercise the part in a simple way. Contained in this document is a description of how to use the USB docking board with the evaluation board and interface software. The LP8556 evaluation board has the means to “plug into” the USB docking board. The USB docking board provides all of the control signals for the simple interface. Power to the part must be provided externally.
The register addresses are shown with the register names in the boxes surrounding the controls. The minimum procedure for turning on the LEDs is as follows: 1. Connect the LED board to the LP8556 evaluation board. Set jumpers for number of LEDs per string. 2. Connect external power and ground to the board. a. Suggest 3.6V to VIN jack. b. Suggest 3.3V to VDDIO jack. c. Connect Ground to GND jack. 3. Jumper on P2 VDD to VIN 4. Jumper on P6 I2C PU to VUSB 5. Turn on the external supplies. 6.
3. LP8556TM-EVM Component Placement Figure 7 shows the top assembly layer of the LP8556TM-EVM.
4. LP8556TM-EVM Component List Table 2 shows the component list of the LP8556TM-EVM. Table 2: Component List Quantity Designator Description Footprint Part Numer Manufacturer Value UMK316BJ225KD-T Taiyo Yuden 2.2 uF UMK316BJ225KD-T Taiyo Yuden 2.2 uF 1 C1 MLCC, 50V, X5R, 10% SM1206 0 C2 NS SM1210 2 C3, C4 MLCC, 50V, X5R, 10% SM1206 0 C5 NS SM0603 2 C6, C7 MLCC, 25V, X5R, 20% SM0603 Standard 1 uF 1 C8 MLCC, 25V, X5R, 20% SM0603 Standard 4.
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7. LP8556 Usage and Programming The LP8556 white LED driver requires configuration of the boost converter and dimming operation. The boost converter can operate at three switching frequencies. Options can be set for spread spectrum and slew rate control. The dimming can be done with a full PWM output, linear current control, or an adaptive combination of the two for the greatest power savings. Phase-shift modes are available for the PWM output. Additional safety features also need to be configured. 7.1.
7.3. Boost Converter Configuration The LP8556 boost converter configuration is determined by the size of the LED array to be driven. Additionally, component constraints will affect operating frequency selection. A calculation tool is available for selecting the boost operating point and external components along with the desired frequency of operation. 7.3.1.
7.4. LED Driver Configuration The LED driver can control the power to the LEDs using PWM dimming, pure current control, or an adaptive combination of the two. See the Adaptive Dimming Control and Brightness control sections of the datasheet for descriptions. The appropriate registers must be set once brightness and dimming control method is selected. The PWM_DIRECT bit in CFG5 may be set for direct control of the PWM output or the BRT_MODE must be selected in the Device Control register at 01h.
7.4.5. Phase Shift LED Outputs The Phase Shift PWM scheme delays the time when each LED driver becomes active as shown in the PS_MODE diagram of the datasheet. Set the PS_MODE bits in the CFG5 to the desired setting. A 111b value selects no phase shift for six drivers. 7.4.6. Curve Shaping and Brightness Change Control Large changes in brightness can be smoothed and controlled using the features of the LP8556.
7.7.
Table 4: Example EPROM Configuration Using I2C Control ADR NAME A0h CFG0 B7 B6 B5 B4 B3 B2 B1 B0 11111111 (Set maximum current, adjust with Brightness Control) A1h CFG1 A2h CFG2 A3h CFG3 CURR_MAX[2:0] CURRENT[11:8] 0 011 (20mA) 1111 Reserved UVLO_EN UVLO_TH BL_ON ISET_EN 1 0 0 0 CFG5 A6h CFG6 A7h A8h AAh CFG10 0 000 00 00 PWM_TO_I_THRESHOLD[3:0] Reserved STEADY DITHER[1:0] 0111 (25% transition point) 0 0 00 PDIRECT PS_MODE[2:0] 0 000 (6 phase) 0100 (9.
7.8. Instructions for Burning the EPROM Once in production the configuration settings will be burned into the EPROM at the factory. Sample units will not have the configuration information saved in EPROM. This can be verified by reading register 72h. The low four bits will read back as 0000b if the configuration portion of the EPROM has not been burned. A successfully burned configuration EPROM will read back as 0Fh. Once a configuration is set it can be burned to the EPROM.
EVALUATION BOARD/KIT/MODULE (EVM) ADDITIONAL TERMS Texas Instruments (TI) provides the enclosed Evaluation Board/Kit/Module (EVM) under the following conditions: The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user indemnifies TI from all claims arising from the handling or use of the goods.
FCC Interference Statement for Class A EVM devices This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment.
Conformément à la réglementation d'Industrie Canada, le présent émetteur radio peut fonctionner avec une antenne d'un type et d'un gain maximal (ou inférieur) approuvé pour l'émetteur par Industrie Canada. Dans le but de réduire les risques de brouillage radioélectrique à l'intention des autres utilisateurs, il faut choisir le type d'antenne et son gain de sorte que la puissance isotrope rayonnée équivalente (p.i.r.e.
EVALUATION BOARD/KIT/MODULE (EVM) WARNINGS, RESTRICTIONS AND DISCLAIMERS For Feasibility Evaluation Only, in Laboratory/Development Environments. Unless otherwise indicated, this EVM is not a finished electrical equipment and not intended for consumer use.
IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46C and to discontinue any product or service per JESD48B. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.
