EV-115 AAT2805 EVAL: Dual High Efficiency Charge Pump For White LED and Flash Applications Introduction The AAT2805 EVAL board demonstrates the functionality of the AAT2805 and its application as a white LED backlight driver with flash capability. The backlighting section of the AAT2805 uses a low-noise, constant frequency charge pump DC/DC converter with tri-mode load switch (1X), fractional (1.5X) and doubling (2X) conversion to maximize efficiency and operate over a wide input voltage range. Dedicated to the flash section is a low-noise, constant frequency doubling (2X) charge pump that is capable of delivering 300mA of pulsed current. The backlighting section is programmable with the AS2Cwire™ (Advanced Simple Serial Control™) serial interface and is capable of driving up to four independent LED channels. LED constant current levels are set from a 16-level logarithmic scale, and four additional low current settings are available down to 50µA. This document describes the evaluation board and its accompanying user interface. In addition, a brief Getting Started section is included to help the user begin operating the evaluation board. A schematic of the complete circuit is shown in Figure 1, and the actual board layout is given in Figures 2 and 3. For additional information, please consult the AAT2805 product datasheet. Schematic DC+ DC- J1 C5 1µF GND D1 D2 D3 D4 C3 1µF JPx C6 1µF R4 1Ω GND GND AAT9513 EN3 R5 20Ω C2 1µF C3EN_FL C3+ C2VOUT_FL C2+ VIN VOUT_BL D4 C1D3 C1+ D2 EN/SET D1 GND Flash LED D0 U1 AAT2805 C4 1µF C1 1µF GND GND U2 LT MV GND DC+ FL R3 R2 R1 1kΩ 1kΩ 1kΩ LIGHT 0 2 4 SW3 1 3 5 MOVIE 0 2 4 FLASH 0 2 4 1 2 3 4 SW2 1 3 5 C7 10µF U3 VDD GP5 GP4 GP3 VSS GP0 GP1 GP2 PIC12F675 SW1 8 R6 330Ω 7 6 LED7 RED 5 GND GND 1 3 5 GND Figure 1: Evaluation Board Schematic. EV-115.2005.06.1.0 1 EV-115 AAT2805 EVAL: Dual High Efficiency Charge Pump For White LED and Flash Applications Getting Started In most cases, the board ships mounted onto a battery pack. The battery pack holds three AAA size, conventional alkaline batteries. A jumper is inline with the battery supply for connecting/disconnecting power. There are three other jumpers labeled LT, MV, and FL. They provide access to EN/SET, EN_FL, and EN3, respectively. To apply power to the board, connect the supply by jumpering ON, MCU. The red LED7 should illuminate, indicating that power has been connected. Ensure that LT, MV, and FL are jumpered so that the microcontroller can control the parts. The user interface is provided by three buttons. The buttons are LIGHT, MOVIE, and FLASH. The modes of operation are detailed in Table 1. Each button handles a particular function. The LIGHT button controls the backlight section. When the LIGHT button is held down, the MCU will auto-cycle through the available brightness level settings after a short delay. The MOVIE button toggles on/off the movie mode illumination. The FLASH button provides a flash pulse and a red-eye reduction function. When the FLASH button is held down, red-eye reduction mode will be entered after a short delay. Button(s) Pushed1 LIGHT MOVIE FLASH LIGHT + FLASH LIGHT + MOVIE MOVIE + FLASH LIGHT + MOVIE + FLASH Description Increment the number of EN/SET edges. Toggles through the available brightness level settings for the backlighting section. If held down, auto-cycle through the settings. Toggle on/off movie mode illumination. Press once to produce a ~300ms flash pulse. Hold down to produce a sequence of red-eye reduction pulses. Decrement the number of EN/SET edges. Toggles through the available brightness level settings for the backlighting section. If held down, auto-cycle through the settings. Increment the address. Cycles through addresses 1, 2, and 3 (i.e., main/sub, main-only, sub-only). Switch to the next current level scale. Cycles through the 20mA, 30mA, 15mA, and Low Current scales. Reset. All enable lines are pulled low. Table 1: User Interface Functionality. 1. The + sign indicates that the specified buttons are all pressed and released together. 2 EV-115.2005.06.1.0 EV-115 AAT2805 EVAL: Dual High Efficiency Charge Pump For White LED and Flash Applications Printed Circuit Board Figure 2: Top Layer (not to scale). Figure 3: Bottom Layer (not to scale)1. 1. When removing the microcontroller or jumpers, the enable lines can be kept from floating by inserting 100kΩ pull-down resistors into the R7, R8, and R9 positions, which are available on the bottom layer. EV-115.2005.06.1.0 3 EV-115 AAT2805 EVAL: Dual High Efficiency Charge Pump For White LED and Flash Applications AAT2805 EVAL Component Listing Component Part Number U1 AAT2805 U2 AAT9513 U3 PIC12F675 D1-D4 D0 R1-R3 C1-C6 C7 R4 R5 R6 JP1 JPx LED7 J1, MV, LT, FL SW1-SW3 Description LW M673 LMFLC4500 Chip Resistor ECJ-1VB1A105K GRM31CR70J106KA01L Chip Resistor Chip Resistor Chip Resistor Chip Resistor Chip Resistor CMD15-21SRC/TR8 PRPN401PAEN PTS645TL50 Manufacturer Dual High Efficiency Charge Pump for AnalogicTech Backlight and Flash; TDFN44-16 Package 65mΩ, N-Channel Power MOSFET; AnalogicTech SC70JW-8 Package 8-Bit CMOS, FLASH-Based µC; Microchip 8-Pin PDIP Package Mini-TOPLED White LED; SMT Package OSRAM Flash White LED; 4-Chip Package Lumimicro 1kΩ, 5%, 1/4W; 1206 Vishay 1µF, 10V, X5R, 10%; 0603 Panasonic-ECG 10µF, 6.3V, X7R, 10%; 1206 Murata 1Ω, 5%, 1/8W; 0805 Vishay 20Ω, 5%, 1/8W; 0805 Vishay 330Ω, 5%, 1/4W; 1206 Vishay 0Ω, 5%; 0805 Vishay 0Ω, 5%; 0603 Vishay Red LED; 1206 Chicago Miniature Lamp Connecting Header, 2mm Sullins Electronics Switch Tact, SPST, 5mm ITT Industries Table 2: Component Listing. AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. AnalogicTech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with AnalogicTech’s standard warranty. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed. Advanced Analogic Technologies, Inc. 830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737-4600 Fax (408) 737-4611 4 EV-115.2005.06.1.0