EVALUATION BOARD DATA SHEET EV191 Evaluation Board for the AAT2428 Sixteen-Channel White LED Driver Solutionwith LED Current and Timing Control Introduction The AAT2428 evaluation board is a hardware platform to evaluate the functions of the AAT2428, a 16-channel white LED driver for LED current and timing control. The AAT2428 operates over a 10.8V to 28V range. The LED input voltage range, VLED, is determined by the highest VF (LED Forward Voltage) multiplied by the number of LEDs in a given string. The maximum VLED is limited to 50V. The maximum VLED must be less than 50V to avoid damage to the AAT2428 on the demo board. The AAT2428 CSFBO and ISCFB outputs provide both a voltage mode (CSFBO) for Skyworks regulators and a current mode (ICSFB) current sense feedback for a third party system power supply. The current sinks are setup in a bank of 4, 8, or 16 current sinks. Each bank is programmable via the SPI interface. Full scale LED current is programmed using an external resistor, R1. DOT correction is applied to each bank independently with 8-bit resolution. Both phase delay and grayscale clock (GS Clock) PWM on-time are user programmable with 12-bit resolution for each current sink bank. Timing and synchronization are determined by externally applied VSYNC and GSCLK signals. The AAT2428 also provides an internal GSCLK signal that tracks with the VSYNC signal with a 4192 ratio to VSYNC. The AAT2428 is available in a small 7mm x 7mm QFN package. More details on the AAT2428 may be found in the product datasheet. This document will cover the board schematic, layout guidelines and setup of a few key configuration registers to demonstrate the AAT2428 driving LED strings with different brightness levels. Scope shots to show the corresponding relationships between related waveforms are also included. Evaluation Board Pictures Figure 1: AAT2428 Evaluation Board Picture. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202328A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 3, 2012 1 EVALUATION BOARD DATA SHEET EV191 Evaluation Board for the AAT2428 Sixteen-Channel White LED Driver Solutionwith LED Current and Timing Control Board Schematic AATI USB Module EN ADDR1 ADDR0 SGND CSB SCLK VCC VIN EN 33 VIN 31 30 CSFBO 29 CSFBI C5 4.7µF 50V C3 2.2µF C1 2.2µF Header 10X2 GND P3.3 GSCLK P3.2 VSYNC P3.1 1 2 SCLK SDO SDI CSB CS16 26 CS15 25 CS14 JP2 1 2 CSB SDI 1 2 3 4 5 6 7 8 9 10 GSCLK VSYNC SDO SCL K JP5 1 3 2 4 GND P2.7 P2.6 P2.5 P2.4 30 29 28 27 26 25 VIN ADDR0 SDI VLED C7 DNP GND TP9 GND GND TP10 TP11 CSFBO 1 2 3 4 5 2 4 ADDR1 SDI P5 1 2 3 Header 5 GSCLK VSYNC P7 1 2 3 4 P9 1 2 CSFBI TP1 P11 1 2 1 2 3 Header 3 1 2 3 4 Header 4 P10 VIN 1 2 Header 2 C8 DNP P6 P8 VLED Header 4 Header 2 CSFBO Header 2 VIN GND GND TP6 TP8 P4 SCLK SDO SDI CSB Header 3 AGND VIN JP6 1 3 R4 DNP Header 5X2 VCC GND 1 2 3 4 5 Header 5 P2 AGND P3 P12 1 2 Header 2 TP2 CSFBO AGND TP3 VLED Parameter Min Input Voltage Range VLED Voltage Range VSYNC Frequency GSCLK Frequency SPI Clock Frequency Ambient Temperature Range Operating Junction Temperature Range 10.8 Typ 55 1024 · VSYNC -40 -40 Max 28 50 1000 2M 15 85 150 Table 1: AAT2428 Evaluation Board Specifications. 2 31 JP1 Printed Circuit Board Specification VIN VLED fVSYNC fGSCLK fSCLK TA TJ 32 1 2 Figure 2: AAT2428 Evaluation Board Schematic. Symbol 34 33 24 23 22 21 20 USB Module P2.3 GND P2.2 P3.0 GND P2.1 P1.3 CSFBI 28 27 VCC CSFBI CS13 CS12 CS11 CS10 CS9 CS8 CS7 CS6 CS5 GND CS2 CS4 CS6 CS8 CS10 CS12 CS14 CS16 VLED 2 4 6 8 10 12 14 16 18 20 12 P3.4 35 JP4 ADDR1 1 3 5 7 9 11 13 15 17 19 11 SCL ENABLE VCC GND GND CS1 CS3 CS5 CS7 CS9 CS11 CS13 CS15 VLED C20 DNP 1 2 ADDR0 P1 10 P3.5 36 GSCLK VCCIO 34 24 23 22 21 SGND CS14 CS13 CS15 N/C CS12 N/C CS11 CS16 CS10 SGND 36 35 32 VSYNC P3.6 19 SDI SDI SDO DGND GSCLK EP VSYNC SGND SGND 13 12 CSFBI 20 11 CS4 CS9 10 N/C CSFBO 19 9 CS2 CS3 SGND 8 VIN SGND 7 CS4 CS1 18 6 CS3 N/C 17 CS2 VCC CS8 5 SGND SGND CS7 CS1 AGND 9 VSYNC U1 AAT2428 VCCIO 16 AGND 4 RSET ICSFB CS6 3 C10 DNP AGND 1 2 15 6.04k 14 C11 2.2µF R1 FLT R13 DNP D2 Diode 1N4148 C21 DNP JP3 GSCLK CSB SDA 18 VSYNC EN ADDR1 AGND DNP 37 38 40 39 41 42 43 44 45 48 R2 GSCLK CS5 12.1k 47 49 D3 C12 DNP DNP 46 AGND DNP R11 R5 R6 R7 R8 0 0 0 0 ADDR0 R9 R10 0 0 AGND R12 SDO R3 2k FLT TP5 FB-I GSCLK TP4 CSB 8 SCLK D1 Red LED VSYNC 7 P3.7 P2.0 6 SDI 17 5 CSB VCC 3V P1.5 4 SDO P1.4 SDI 5V 16 3 SCLK GND SDO GND GND 15 2 14 SCLK 13 1 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202328A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 3, 2012 Units V Hz MHz °C EVALUATION BOARD DATA SHEET EV191 Evaluation Board for the AAT2428 Sixteen-Channel White LED Driver Solutionwith LED Current and Timing Control Getting Started Setup 1. Connect an input power source (to supply between 10.8V and 28V) between VIN and ground. 2. If using the Skyworks USB Module, connect the USB Module to USB Module connector on the AAT2428 demo board. Otherwise, connect frequency generators to apply between 55Hz to 480Hz to VSYNC and the appropriate frequency to GSCLK, leading edge synchronized to VSYNC. Apply a frequency that has a minimum of 4096 · VSYNC frequency on GSCLK. Refer to the AAT2428 product datasheet to determine the correct GSCLK frequency for the application operating condition. Connect SPI interface on P2. 3. Apply VLED. If VLED is in closed-loop operation and is applied from a third party SMPS converter, connect the FB-I for current mode to the feedback input of the third party SMPS converter. Calculate the value of resistor R3 for desired VLED level. If using an Skyworks boost converter, connect the CSFBO to the feedback input of the Skyworks boost converter. 4. Connect JP1 jumper to ON to enable AAT2428. 5. Set ADDR0 and ADDR1 jumpers to desired address setting. 6. Connect LED strings to P1 using information provided in Table 2. 7. If desired, multiple AAT2428 demo boards with different device address settings can be cascaded together to drive more than 16 LED channels as shown in Figure 3. Pin 1 2 3 4 5 6 7 8 9 10 Description GND GND Current Current Current Current Current Current Current Current Sink Sink Sink Sink Sink Sink Sink Sink 1 2 3 4 5 6 7 8 Pin 11 12 13 14 15 16 17 18 19 20 Description Current Current Current Current Current Current Current Current VLED VLED Sink Sink Sink Sink Sink Sink Sink Sink 9 10 11 12 13 14 15 16 Table 2: P1 LED Pinout Configuration. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202328A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 3, 2012 3 EVALUATION BOARD DATA SHEET EV191 Evaluation Board for the AAT2428 Sixteen-Channel White LED Driver Solutionwith LED Current and Timing Control Figure 3: AAT2428 PCB + LED Board Picture. Figure 4: Multiple AAT2428 Demo Boards Cascaded Together to Drive More Than 16 LED Channels. 4 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202328A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 3, 2012 EVALUATION BOARD DATA SHEET EV191 Evaluation Board for the AAT2428 Sixteen-Channel White LED Driver Solutionwith LED Current and Timing Control Functional Test and Evaluation RSET and DOT Register The RSET resistors, R1, on the AAT2428 is 6.04kΩ, and set the maximum full scale LED current to 101.72mA. The DOT correction register provides 256 linear steps between current sink being off and the maximum full scale LED current to adjust the luminance of the LEDs. Figure 4 shows the LED current at its full scale setting with DOT register sets to 0xFF. Figure 5 shows the LED current at its half scale setting with DOT register sets to 0x80. Figure 5: LED Current with DOT = 0xFF. Figure 6: LED current with DOT = 0x80. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202328A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 3, 2012 5 EVALUATION BOARD DATA SHEET EV191 Evaluation Board for the AAT2428 Sixteen-Channel White LED Driver Solutionwith LED Current and Timing Control GS Registers The GS registers control the PWM duty cycle of the LED current sinks for adjusting the brightness. Figure 6 shows a LED string running at 50% duty with GS register sets to 0x800. Figure 7 shows a LED string running at 25% duty with GS register sets to 0x400. Figure 8 shows a LED string running at 75% duty with GS register sets to 0xC00. Figure 7: PWM at 50% Duty Cycle with GS = 0x800. Figure 8: PWM at 25% Duty Cycle with GS = 0x400. 6 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202328A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 3, 2012 EVALUATION BOARD DATA SHEET EV191 Evaluation Board for the AAT2428 Sixteen-Channel White LED Driver Solutionwith LED Current and Timing Control Figure 9: PWM at 75% Duty Cycle with GS=0xC00. DLY Registers The DLY registers set the phase shift from the rising edge of VSYNC to when the current sink PWM cycle begins for each LED current sink. Figure 9 shows a phase shift of 0° with DLY register setting to 0x000. Figure 10 shows a phase shift of 90° with DLY register sets to 0x400. Figure 11 shows a phase shift of 180° with DLY register setting to 0x800. Figure 12 shows a phase shift of 270° with DLY register setting to 0xC00. Figure 13 shows a phase shift of 360° with DLY register setting to 0xFFF. One advantage of using delay is that it allows each current sink to start at different time to reduce the stress on a system power supply. The other advantage is that it can provide a fixed off time in scanning mode when the delay is used in combination with the INVERT function. Figure 10: 0° Phase Shift with DLY = 0x000. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202328A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 3, 2012 7 EVALUATION BOARD DATA SHEET EV191 Evaluation Board for the AAT2428 Sixteen-Channel White LED Driver Solutionwith LED Current and Timing Control Figure 11: 90° Phase Shift with DLY = 0x400. Figure 12: 180° Phase Shift with DLY = 0x800. 8 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202328A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 3, 2012 EVALUATION BOARD DATA SHEET EV191 Evaluation Board for the AAT2428 Sixteen-Channel White LED Driver Solutionwith LED Current and Timing Control Figure 13: 270° Phase Shift with DLY = 0xC00. Figure 14: 360° Phase Shift with DLY = 0xFFF. INVERT Function The INVERT function allows the PWM signal to be inverted. A 25% duty cycle (GS = 0x400) with the INVERT function enabled will be a 75% duty cycle output. A 90° delay turn-on time (DLY = 0x400) with the INVERT function enabled will have a turn-on time at 90°. The INVERT function can provide a fixed off time in scanning mode. Figure 14 and 15 show two PWM waveforms with INVERT function disabled, sharing the same turn-on time with different duty cycle. Figure 16 and 17 show two PWM waveforms with the same setting as Figure 16 and 17 with INVERT function enabled. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202328A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 3, 2012 9 EVALUATION BOARD DATA SHEET EV191 Evaluation Board for the AAT2428 Sixteen-Channel White LED Driver Solutionwith LED Current and Timing Control Figure 15: Non-Inverted 20% Duty Cycle with 45° Phase Shift Turn-On Time (GS = 0x333, DLY = 0x200, INVERT = 0). Figure 16: Non-Inverted 80% Duty Cycle with 45° Phase Shift Turn-On Time (GS = 0xCCC, DLY = 0x200, INVERT = 0). 10 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202328A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 3, 2012 EVALUATION BOARD DATA SHEET EV191 Evaluation Board for the AAT2428 Sixteen-Channel White LED Driver Solutionwith LED Current and Timing Control Figure 17: Inverted 20% Duty Cycle with 45° Phase Shift Turn-Off Time (GS = 0x333, DLY = 0x200, INVERT = 1). Figure 18: Inverted 80% Duty Cycle with 45° Phase Shift Turn-Off Time (GS = 0xCCC, DLY = 0x200, INVERT = 1). Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202328A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 3, 2012 11 EVALUATION BOARD DATA SHEET EV191 Evaluation Board for the AAT2428 Sixteen-Channel White LED Driver Solutionwith LED Current and Timing Control Open and Short Fault Detection The AAT2428 provides the open and short fault detection to detect any LED that is open or short. The fault status is indicated by the FLT pin and Fault Status registers. The AAT2428 has a programmable open fault blanking time. The blanking time can be programmed to 2, 4, 8, or 16 VSYNC cycles to prevent any false fault detection due to the slow system response from SMPS at PWM startup. The AAT2428 does not provide short fault blanking time. The AAT2428 has an open fault clear bit and a short fault clear bit. By setting the fault clear bit, the fault status is removed and any further fault will not be detected until the bit is reset back to 0. Figure 18, 19, 20 and 21 show the 2, 4, 8, and 16 VSYNC blanking time settings in open fault detection. Figure 22 shows the short fault detection without any VSYNC blanking time. Figure 19: Open Fault with the 2 VSYNC Blanking Time. Figure 20: Open Fault with the 4 VSYNC Blanking Time. 12 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202328A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 3, 2012 EVALUATION BOARD DATA SHEET EV191 Evaluation Board for the AAT2428 Sixteen-Channel White LED Driver Solutionwith LED Current and Timing Control Figure 21: Open Fault with the 8 VSYNC Blanking Time. Figure 22: Open Fault with the 16 VSYNC Blanking Time. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202328A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 3, 2012 13 EVALUATION BOARD DATA SHEET EV191 Evaluation Board for the AAT2428 Sixteen-Channel White LED Driver Solutionwith LED Current and Timing Control Figure 23: Short Fault Detection – No VSYNC Blanking. 14 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202328A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 3, 2012 EVALUATION BOARD DATA SHEET EV191 Evaluation Board for the AAT2428 Sixteen-Channel White LED Driver Solutionwith LED Current and Timing Control Layout Guidelines Follow the guidelines below to ensure proper operation of the AAT2428: 1. Maintain a ground plane and connect to the IC GND pin(s), and minimize the distance from the input capacitor negative terminal to the GND pins. 2. Consider additional PCB GND exposed area for the AAT2428 to maximize heat sinking capability. Connect the EP (bottom of the die) to GND. Connect GND and SGND as close as possible to the package and maximize the heat sinking space for overall performance. 3. Maximize package thermal dissipation and power handling capacity of the QFN77-48 package, solder the exposed paddle of the IC onto the thermal landing of the PCB, where the thermal landing is connected to the ground plane. If heat is still an issue, multi-layer boards with dedicated ground planes are recommended. Also, adding thermal vias with 0.3mm hole size and 1.2mm spacing between the vias (Refer to Figures 2 and 3) on the thermal landing would help transfer heat to the bottom GND plane of the PCB effectively. Component U1 C5 C1, C3, C11 D2 R1 R3 R11 R5, R6, R7, R8, R9, R10 JP1, JP2, JP3, JP4 JP5, JP6 P1 P2 P3, P5, P7, P9, P11 P4, P6, P8, P10, P12 Part Number Description AAT2428 UMK316BJ475KL-T GRM188R61C225KE15D LL4148-13 CRCW06036K04FKEA CRCW060310K0FKEA CRCW060312K1FKEA CRCW06030000Z0EA TSW-120-08-G-D TSW-120-08-G-D HRP10H-ND AWHW20G-0202-T-R 801-43-050-20-001000 802-10-064-20-001000 16 Channels White LED Driver Cap Cer 4.7μF 50V X5R 1206 Cap Cer 2.2μF 16V X5R 0603 Diode Switch 75V 500MW MINIMELF Res 6.04KΩ 1/10W 1% 0603 SMD Res 10KΩ 1/10W 1% 0603 SMD Res 12.1KΩ 1/10W 1% 0603 SMD Res 0Ω 1/10W 1% 0603 SMD Conn. Header 2 Pos, 2.54mm Conn. Header 4 Pos, 2.54mm Header 5x2-Pin, Dual Row, 2.54mm Header 10x2-Pin, Dual Row, 2.54mm Right Angle Conn Socket, 2.54mm Right Angle Header, 2.54mm Manufacturer Skyworks Taiyo Yuden Murata Diode Inc. Vishay Samtec, Inc. Assmann Mill-Max Table 3: AAT2428 Evaluation Board BOM. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202328A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 3, 2012 15 EVALUATION BOARD DATA SHEET EV191 Evaluation Board for the AAT2428 Sixteen-Channel White LED Driver Solutionwith LED Current and Timing Control Figure 24: AAT2428IDX (7mm × 7mm TDFN) Evaluation Board Layout – Top Layer. Figure 25: AAT2428IDX (7mm × 7mm TDFN) Evaluation Board Layout – Bottom Layer. 16 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202328A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 3, 2012 EVALUATION BOARD DATA SHEET EV191 Evaluation Board for the AAT2428 Sixteen-Channel White LED Driver Solutionwith LED Current and Timing Control Copyright © 2012 Skyworks Solutions, Inc. 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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 202328A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 3, 2012 17