EVALUATION BOARD DATA SHEET EV179 Evaluation Board for the AAT1451 Four-LED String, High Efficiency White LED Driver for LCD Backlighting Introduction The AAT1451 evaluation board demonstrates the functionality of the AAT1451 and its application as a white LED driver under PWM control. The AAT1451 is a step-up LED driver with four-precision current sinks and an input voltage range of 5V to 26V. The wide input voltage range, the small solution size, the PWM adjustment with phase shift and the high efficiency are suitable for LED backlight solutions in notebooks, netbook computers, monitors and portable TVs that use power supplied by DC sources such as cigarette lighter adapters or multi-cell Li-ion batteries. The precision high-voltage current sink maintains the maximum LED current, set by an external resistor, up to 31mA. The high switching frequency supports ultra-small, low-cost filtering components. This document describes the evaluation board and its accompanying user interface. A brief “Getting Started” section is included to help the user to begin operating the evaluation board. The AAT1451 evaluation board is shown in Figure 1. Figure 2 and Figure 10 depict the board schematic and layout. For additional information, please consult the AAT1451 product datasheet. Board Picture a: Top Side b: Bottom Side Figure 1: AAT1451 Evaluation Board Picture. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202318A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012 1 EVALUATION BOARD DATA SHEET EV179 Evaluation Board for the AAT1451 Four-LED String, High Efficiency White LED Driver for LCD Backlighting Schematic SW DS1 SS16L L1 4.7µH U1 AAT1451 J1 VIN 5V-26V DC+ 1 2 CIN 2.2µF/50V R4 10k C2 0.1µF CCOMP 15nF PWM RCOMP 20k RSET 7.5k CYCLE S3 AAT1451 Evaluation Board R1 42.7k 16 SW OVP VOUT COUT 2.2µF 50V R2 1.2k 15 The evaluation board J3 should be connected to LED board J1 FLT SHDN FAULT R3 10k 10 FB1 5 FB1 1 FB2 6 FB2 2 ISET FB3 7 FB3 3 FSLCT FB4 8 FB4 11 PWM 13 COMP 4 3 PGND RFS 20k 1 5 J3 EP GND 0 4 VCC 14 Da7 Db7 Dc7 Dd7 MCU Da 8 Db 8 Dc8 Dd8 Da 6 Db 6 Dc6 Dd 6 Da9 Db9 Dc9 Dd 9 Da5 Db5 Dc5 Dd 5 Da10 Db10 Dc10 Dd10 Da 4 Db 4 Dc4 Dd 4 VMCU R8 R9 R10 1k 1k 1k DOWN S2 VDD 12 R5 10k UP S1 9 CVDD 2.2µF 6.3V EN VCC VIN 3 GND VCC 2.2V-5V 2 VOUT U2 PIC12F675 1 S1 2 3 4 S2 VDD GP5 GP4 GP3 VSS GP0 GP1 GP2 C1 0.1µF 8 7 6 5 R6 330 LED2 Green S3 R7 1k LED1 Red Da11 Db11 Dc11 Dd11 Da3 Db3 Dc3 Dd 3 Da12 Db12 Dc12 Dd12 Da 2 Db 2 Dc2 Dd 2 FB 1 FB 2 FB 3 FB 4 1 2 3 4 J1 Da1 Db1 Dc1 Dd1 5 VOUT JP1 JP2 JP3 JP4 LED Board Figure 2: AAT1451 Evaluation Board and LED Board Schematic. 2 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202318A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012 EVALUATION BOARD DATA SHEET EV179 Evaluation Board for the AAT1451 Four-LED String, High Efficiency White LED Driver for LCD Backlighting LED Board The AAT1451 can drive up to 12 LEDs in each of four channels in many combinations. The LED board shown in figure 3 is designed to work with the AAT1451 evaluation board. Users can evaluate LED string combinations with fewer than the maximum number supported by the AAT1451. a: Top view of LED board b: LED board connected to the AAT1451 demo board Figure 3: LED Board Picture. To demonstrate operation with fewer WLEDs, some of the WLEDs on the LED board can be shorted. For example, for 4 strings with 9 WLEDs per string for a total of 36 WLEDs as shown in Figure 4, all four jumpers are connected and 3 WLEDs are shorted by short wiring each string. Figure 4: WLED Setting of 8 WLEDs for each of 4 Strings. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202318A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012 3 EVALUATION BOARD DATA SHEET EV179 Evaluation Board for the AAT1451 Four-LED String, High Efficiency White LED Driver for LCD Backlighting Getting Started The evaluation is performed using a bench test set up with or without a signal source for PWM. Figure 5(a) shows the connections for PWM dimming using a microcontroller and Figure 5(b) shows the connections using an external signal source. The tables below highlight the steps for configuring the board for each of these options and making the correct connections to the appropriate test equipment. Apply power to the board only after verifying that all the jumpers and the connections are in the right place. Power Supply 5V~26V 2.2V~5V Power Supply Here are the terminals of VOUT and current sinks. They should be connected to LED board 5V~26V 2.2V~5V Signal Source Square wave Freq=100~10kHz VPWM(H)=2.2V~5V (a) PWM dimming through microcontroller Here are the terminals of VOUT and current sinks. They should be connected to LED board (b) PWM dimming through external signal source Figure 5: AAT1451 Evaluation Board Demonstration Connection. PWM Dimming Through Microcontroller - Refer To Figure 5(a) Step Actions Configure Board Place J1 Jumper to the Left Place EN Jumper to the Left Place a Jumper on the MCU posts Place a Jumper on the Left posts of PWM 4 Function Comments Connects VIN Power to the AAT1451 Connects VCC Power to AAT1451 enable (SHDN) Connects VCC Power to Microcontroller VDD Enables PWM using Microcontroller Must be Open when Using External Source for PWM Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202318A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012 EVALUATION BOARD DATA SHEET EV179 Evaluation Board for the AAT1451 Four-LED String, High Efficiency White LED Driver for LCD Backlighting Make Connections Evaluate/Demonstrate Capabilities Connect the LED Board (J1) to the AAT1451 Evaluation Board (J3) Connect Bench Power Supply '+' Terminals to the VIN and VCC Inputs on the Board Connect Bench Power Supply '-' Terminals to the GND Input on the Board Apply Power to the Microcontroller and the AAT1451 Press One of Three Buttons: UP DOWN BUTTON CYCLE Connects the LED Strings to AAT1451 Used for Lighting the LEDs 5V~26V to Power AAT1451 (U1) 2.2V~5V to Power the Microcontroller (U2) and enable AAT1451 (U1) Ensure that the Power Supply is OFF at this point Common Ground Turns on the LED Strings with Maximum Brightness 100% Duty Cycle Increases Current from Min to Max and Wraps Back Decreases Current from Max to Min and Wraps Back Increments or Decrements Automatically Based on Previous State LED1 (red) will light up Changes PWM Duty Cycle in 5% Steps Through Entire Range PWM Dimming Through External Signal Source - Refer To Figure 5(b) Step Actions Configure Board Make Connections Evaluate/Demonstrate Capabilities Place J1 Jumper to the Left Place EN Jumper to the Left Place a Jumper on the MCU posts Open the Jumper on the Left posts of PWM Connect the LED Board (J1) to the AAT1451 Evaluation Board (J3) Connect Bench Power Supply '+' Terminals to the VIN and VCC Inputs on the Board Connect Bench Power Supply '-' Terminals to the GND Input on the Board Connect Signal Source to Right Terminal of PWM Jumper Post Apply Power to the Microcontroller and the AAT1451 Press One of Three Buttons: UP DOWN BUTTON CYCLE Function Comments Connects VIN Power to the AAT1451 Connects VCC Power to AAT1451 enable (SHDN) Connects VCC Power to Microcontroller VDD Enables PWM using External Signal Source Must be Closed for Microcontroller Mode Connects the LED Strings to AAT1451 Used for Lighting the LEDs 5V~26V to Power AAT1451 (U1) 2.2V~5V to Power the Microcontroller (U2) and enable AAT1451 (U1) Ensure that the Power Supply is OFF at this point Common Ground PWM Control by External Signal Source Turns on the LED Strings with Maximum Brightness 100% Duty Cycle Increases Current from Min to Max and Wraps Back Decreases Current from Max to Min and Wraps Back Increments or Decrements Automatically Based on Previous State LED1 (red) will light up Changes PWM Duty Cycle in 5% Steps Through Entire Range Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202318A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012 5 EVALUATION BOARD DATA SHEET EV179 Evaluation Board for the AAT1451 Four-LED String, High Efficiency White LED Driver for LCD Backlighting PWM Dimming through Microcontroller When using the microcontroller as the PWM source, the LED brightness is changed by using the three buttons marked "UP", "DOWN" and "CYCLE". The WLED current will change between the maximum LED current, as set by RSET, and 5% of ILED(MAX). The generated PWM signal varies between 5% and 100% in 5% steps to adjust the WLED current according to the status of the three buttons. The operation steps are: 1. Configure board for the PWM Dimming Through Microcontroller mode as described in the Getting Started section. 2. Apply power to AAT1451 (U1) and MCU (U2). All WLEDs will light up to 21mA with the PWM at 100% duty cycle and RSET of 7.5kΩ. 3. Press one of the three buttons to observe the white LED dimming or brightening under the PWM control with varied duty cycle. • UP button: With every push/release, the WLED current rises from 5% of the maximum value (21mA) to the maximum value as the PWM duty cycle increases from 5% to 100% in 5% steps and then wraps back to 5%. • DOWN button: With every push/release the current is decreased from maximum value (21mA) to 5% of maximum as the PWM duty cycle decreases from 100% to 5% in 5% steps and then wraps back to 100%. • CYCLE button: After one push/release, the WLED current increases or decreases cyclically as the duty cycle increments or decrements automatically in 5% steps based on the previous PWM duty cycle event (up or down). PWM Duty vs WLED Current LED Current (mA) 25 20 VIN= 5.0 15 VIN= 8.0 10 VIN= 18.0 VIN= 12.0 VIN= 22.0 VIN= 26.0 5 0 0 10 20 30 40 50 60 70 80 90 100 PWM Duty (%) Figure 6: PWM Dimming Duty Cycle vs. LED Current PWM Dimming through External Signal Source To use external PWM dimming control, configure the board as described in the PWM Dimming through External Signal Source mode as described in the Getting Started section. Set the external signal source to generate a square waveform with VPWM(H) = 2.2V ~ 5V, Freq = 100~10kHz with Duty varying from 5% to 100%. The WLED brightness is changed by the PWM signal with varied duty cycle. The UP, DOWN and CYCLE buttons do not function in this condition. 6 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202318A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012 EVALUATION BOARD DATA SHEET EV179 Evaluation Board for the AAT1451 Four-LED String, High Efficiency White LED Driver for LCD Backlighting Test Waveform Operation Waveform Figure 7 shows the waveform under VIN = 5V with 11 WLEDs in series in 4 sinks for a total of 44 WLEDs, ILED = 21mA. PWM high. Figure 8 shows the waveform under the same test conditions as Figure 7 except that PWM is modified to 50% duty cycle. Figure 7: Operation Waveform Under Full PWM Duty Cycle. Ch1: SW; Ch2: VIN (AC); Ch3: IL; Ch4: VOUT (AC) Figure 8: Operation Waveform Under 50% PWM Duty Cycle. Ch1: VFBx; Ch2: PWM; Ch3: ILEDx; Ch4: VOUT Automatic Phase Shift Figure 9 shows the AAT1451's feedback voltage phase shift waveform under VIN = 5V, PWM = 1kHz, 50% duty cycle, ILED = 21mA, 4 sinks, 11 LEDs in series. Figure 9: Feedback Voltage Phase Shift Waveform. (Ch1: VFB1; Ch2: VFB2; Ch3: VFB3; Ch4: VFB4) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202318A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012 7 EVALUATION BOARD DATA SHEET EV179 Evaluation Board for the AAT1451 Four-LED String, High Efficiency White LED Driver for LCD Backlighting Printed Circuit Board a: Top layer (not to scale) b: Bottom Layer (not to scale) Figure 10: AAT1451 Evaluation Board. AAT1451 EVAL Component Listing Component Part Number Description Manufacturer U1 U2 S1~S3 RCOMP, RFS RSET R4 R6 R7, R8, R9, R10 AAT1451IRN PIC12F675 PTS645TL50 Chip Resistor Chip Resistor Chip Resistor Chip Resistor Chip Resistor High Efficiency White Backlight LED Driver 8-Pin Flash-Based 8-Bit CMOS Microcontroller Switch Tact, SPST, 5mm 20kΩ, 1%, 1/4W; 0603 7.5kΩ, 1%, 1/4W; 0603 51kΩ, 1%, 1/4W; 0603 330Ω, 1%, 1/4W; 0603 1kΩ, 1%, 1/4W; 0603 Skyworks Microchip ITT Industries CIN, COUT GRM31CR71H225KA88 2.2μF, 50V, X7R, 1206 CVDD GCM188R70J225KE22 2.2μF, 6.3V, X7R, 0603 CCOMP GRM188R71H153KA01 15nF, 50V, X7R, 0603 C1 GRM188R71H104KA93 0.1μF, 50V, X7R, 0603 L1 DS1 LED1 LED2 SD53-4R7-R SS16L CMD15-21SRC/TR8 CMD15-21UGC/TR8 4.7μH, 45mΩ, 2.01A, 20% 1.0Amp., 60V Surface Mount Schottky Barrier Rectifier Red LED; 1206 Green LED; 1206 Vishay Murata Coiltronics TSC Chicago Miniature Lamp Chicago Miniature Lamp Table 1: AAT1451 Evaluation Board Bill of Materials. 8 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202318A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012 EVALUATION BOARD DATA SHEET EV179 Evaluation Board for the AAT1451 Four-LED String, High Efficiency White LED Driver for LCD Backlighting Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved. Information in this document is provided in connection with Skyworks Solutions, Inc. (“Skyworks”) products or services. These materials, including the information contained herein, are provided by Skyworks as a service to its customers and may be used for informational purposes only by the customer. Skyworks assumes no responsibility for errors or omissions in these materials or the information contained herein. Skyworks may change its documentation, products, services, specifications or product descriptions at any time, without notice. Skyworks makes no commitment to update the materials or information and shall have no responsibility whatsoever for conflicts, incompatibilities, or other difficulties arising from any future changes. No license, whether express, implied, by estoppel or otherwise, is granted to any intellectual property rights by this document. Skyworks assumes no liability for any materials, products or information provided hereunder, including the sale, distribution, reproduction or use of Skyworks products, information or materials, except as may be provided in Skyworks Terms and Conditions of Sale. THE MATERIALS, PRODUCTS AND INFORMATION ARE PROVIDED “AS IS” WITHOUT WARRANTY OF ANY KIND, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHERWISE, INCLUDING FITNESS FOR A PARTICULAR PURPOSE OR USE, MERCHANTABILITY, PERFORMANCE, QUALITY OR NON-INFRINGEMENT OF ANY INTELLECTUAL PROPERTY RIGHT; ALL SUCH WARRANTIES ARE HEREBY EXPRESSLY DISCLAIMED. SKYWORKS DOES NOT WARRANT THE ACCURACY OR COMPLETENESS OF THE INFORMATION, TEXT, GRAPHICS OR OTHER ITEMS CONTAINED WITHIN THESE MATERIALS. SKYWORKS SHALL NOT BE LIABLE FOR ANY DAMAGES, INCLUDING BUT NOT LIMITED TO ANY SPECIAL, INDIRECT, INCIDENTAL, STATUTORY, OR CONSEQUENTIAL DAMAGES, INCLUDING WITHOUT LIMITATION, LOST REVENUES OR LOST PROFITS THAT MAY RESULT FROM THE USE OF THE MATERIALS OR INFORMATION, WHETHER OR NOT THE RECIPIENT OF MATERIALS HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. Skyworks products are not intended for use in medical, lifesaving or life-sustaining applications, or other equipment in which the failure of the Skyworks products could lead to personal injury, death, physical or environmental damage. Skyworks customers using or selling Skyworks products for use in such applications do so at their own risk and agree to fully indemnify Skyworks for any damages resulting from such improper use or sale. Customers are responsible for their products and applications using Skyworks products, which may deviate from published specifications as a result of design defects, errors, or operation of products outside of published parameters or design specifications. Customers should include design and operating safeguards to minimize these and other risks. Skyworks assumes no liability for applications assistance, customer product design, or damage to any equipment resulting from the use of Skyworks products outside of stated published specifications or parameters. Skyworks, the Skyworks symbol, and “Breakthrough Simplicity” are trademarks or registered trademarks of Skyworks Solutions, Inc., in the United States and other countries. Third-party brands and names are for identification purposes only, and are the property of their respective owners. Additional information, including relevant terms and conditions, posted at www.skyworksinc.com, are incorporated by reference. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202318A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 30, 2012 9