EV-122 AAT3175 EVAL: High Efficiency 1X/1.5X/2X Charge Pump For White LED Flash Applications Introduction The AAT3175 EVAL board demonstrates the functionality of the AAT3175 and its application as a white LED flash driver. The AAT3175 is 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. The AAT3175 is programmable with AnalogicTech’s S2Cwire™ (Simple Serial Control™) serial interface and has four independent, constant current LED channels. LED constant current levels are set according to a 16level logarithmic scale. The device is able to achieve a flash current level of 300mA while requiring only 1µF capacitors. This document describes the evaluation board and its accompanying user interface. A brief “Getting Started” section is also included to help the user begin operating the evaluation board. A schematic of the complete circuit appears in Figure 1; Figures 2 and 3 depict the actual board layout. For additional information, please consult the AAT3175 product datasheet. Schematic DC+ DC- J1 DC+ U1 AAT3175 C1 1µF 1 2 3 4 5 6 C3 1µF D4 EN/SET C1+ C1VOUT C2+ D3 D2 D1 GND VIN C2- 12 11 10 9 8 7 JPx C4 1µF C2 1µF GND D1 GND R7 220 J2 R6 100K DC+ GND R3 R2 1K 1K DATA 0 2 4 SW3 1 3 5 FLASH 0 2 4 MOVIE 0 2 4 SW2 1 3 5 R1 1K C5 10µF U2 1 2 3 4 VDD GP5 GP4 GP3 PIC12F675 VSS GP0 GP1 GP2 8 7 6 5 VR4 POT 10K R4 330 SW1 1 3 5 GND R5 330 LED7 RED GND LED0 GRN GND GND Figure 1: AAT3175 Evaluation Board Schematic. EV-122.2005.10.1.0 1 EV-122 AAT3175 EVAL: High Efficiency 1X/1.5X/2X Charge Pump For White LED Flash Applications Getting Started The board has two terminals labeled DC- and DC+ for the input power supply connection. A jumper is inline with the supply bus for connecting/disconnecting power (J1). To apply power to the board, connect the supply by jumpering ON, MCU; the red LED7 should illuminate, indicating that power has been connected to the board. There is an additional jumper labeled ON SRL OFF, which provides access to EN/SET. For operation with the accompanying microcontroller and user interface, ensure that the jumper is in the ON SRL position. The user interface is provided by three buttons: DATA, FLASH, and MOVIE. The modes of operation are detailed in Table 1. The DATA button increments the data setting until reaching 16, at which point it wraps back to 1. Use the DATA button to set the current for flash and movie modes. As an example, pressing the DATA button 4 times will set the microcontroller to use 5 EN/SET edges for flash or movie (the default of 1, plus 4 gives 5). Pushing the FLASH button will release a flash pulse. The current level for the flash pulse is determined by the data setting. The duration of the flash pulse is determined by the trim pot VR4. The flash pulse duration can be set from 10ms to 2 seconds by adjusting VR4. The MOVIE button toggles the device on and off. The current level is also determined by the data setting. To reset the microcontroller, press all three buttons together and then release them. The data setting will be reset back to 1. To see the effect of each current level step, enable the device with the MOVIE button and then use the DATA button to traverse the 16 settings with the LED on. User Interface Functionality Button(s) Pushed1 DATA Description Increments through the 16 data settings. Hold down to auto-cycle. (Does not turn light on; just sets DATA.) FLASH Generate flash pulse. Current level determined by DATA setting. Duration determined by trim pot VR4 (adjustable from 10ms to 2 sec). MOVIE Toggle the device ON/OFF. Current level determined by DATA setting. CYCLE + UP + DOWN Reset. Table 1: User Interface Functionality. 1. The '+' sign indicates that these buttons are all pressed and released together. 2 EV-122.2005.10.1.0 EV-122 AAT3175 EVAL: High Efficiency 1X/1.5X/2X Charge Pump For White LED Flash Applications Printed Circuit Board Figure 2: AAT3175 Evaluation Board Top Layer (not to scale). Figure 3: AAT3175 Evaluation Board Bottom Layer (not to scale). EV-122.2005.10.1.0 3 EV-122 AAT3175 EVAL: High Efficiency 1X/1.5X/2X Charge Pump For White LED Flash Applications AAT3175 EVAL Component Listing Component Part Number U1 AAT3175 U2 PIC12F675 D1 R1-R3 C1-C4 J1, J2 LED0 LED7 C5 R4, R5 R6 R7 JPx JP7, JP8 VR4 SW1-SW3 Description LMFLC4500 Chip Resistor GRM188R61A105KA93D PRPN401PAEN CMD15-21UGC/TR8 CMD15-21SRC/TR8 GRM31CR70J106KA01L Chip Resistor Chip Resistor Chip Resistor Chip Resistor Chip Resistor EVN-5ESX50B14 PTS645TL50 High Efficiency 1X/1.5X/2X CP for White LED; TDFN33-12 Package 8-Bit CMOS, FLASH-based µC; 8-Pin PDIP Package 4-Die, 2-Pin, High Luminosity LED 1KΩ, 5%, 1/4W; 1206 1µF, 10V, X5R, 10%; 0603 Connecting Header, 2mm Zip Green LED; 1206 Red LED; 1206 10µF, 6.3V, X7R, 10%; 1206 330Ω, 5%, 1/4W; 1206 100KΩ, 5%, 1/4W; 1206 220Ω, 5%, 1/4W; 1206 0Ω, 5%; 0603 0Ω, 5%; 0805 10K POT; 3mm Squared SMD Switch Tact, SPST, 5mm Manufacturer AnalogicTech Microchip Lumimicro Vishay Murata Sullins Electronics Chicago Miniature Lamp Chicago Miniature Lamp Murata Vishay Vishay Vishay Vishay Vishay Panasonic-ECG 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-122.2005.10.1.0