EV-127 AAT3172 EVAL: High Current LED Flash Driver Charge Pump IC Introduction The AAT3172 EVAL board demonstrates the functionality of the AAT3172 and its application as a high current white LED flash driver. The device consists of a tri-mode charge pump with load switch (1X), fractional (1.5X), and doubling (2X) conversion modes to provide excellent efficiency for both flash and movie modes. Two LED channels are provided with excellent current matching. By utilizing the two LED channels, better light efficiency can be achieved with two LEDs as opposed to one. The charge pump is designed to deliver 600mA total LED drive current. Through the Advanced Simple Serial Control™ interface (AS2Cwire™), an additional constant voltage mode is available. Constant voltage mode produces a regulated 4.5V output that is capable of driving loads up to 100mA. In addition to driving LEDs for flash applications, other loads such as keypad lighting can also be powered from the 4.5V output. 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. The actual board layout is also provided. For additional information, please consult the AAT3172 product datasheet. Schematic DC- DC+ J1 DC+ C4 4.7µF GND U1 AAT3172 C1 1µF 1 VIN C1+ C1GND F1 F2 2 3 4 5 6 VIN VOUT C2+ C2N/C EN/SET 12 11 10 C3 2.2µF 9 8 C2 1µF 7 GND GND D1 D2 Uses a single flash LED: Lumileds LXCL-PWF1 or Lumimicro LMPTWH556S, not both R6 100K J2 GND DC+ R7 220K R3 R2 R1 1K 1K 1K DATA FLASH MOVIE GND 0 2 4 0 2 4 0 2 4 SW3 1 3 5 2 3 4 SW2 1 3 5 SW1 1 3 5 U2 1 VDD GP5 GP4 GP3 PIC12F675 VSS GP0 GP1 GP2 VR4 POT10K 8 7 C7 1µF 6 R5 330K LED7 RED 5 R4 330K GND GND LED0 GRN GND Figure 1: AAT3172 Evaluation Board Schematic. EV-127.2006.04.1.0 1 EV-127 AAT3172 EVAL: High Current LED Flash Driver Charge Pump IC Getting Started In most cases, the board ships mounted onto a battery pack. The battery pack holds three AAA size, conventional alkaline batteries. When no battery pack is present, external power can be applied to the DC+ and DCterminals. A jumper labeled J1 is inline with the battery supply terminal DC+ for connecting/disconnecting power. To apply power to the board, connect the supply by jumpering ON, MCU. The red LED7 should illuminate, indicating that power has been connected. There is an additional jumper labeled J2 that provides access to the EN/SET pin of the AAT3172. Ensure that ON SRL is also jumpered so that the microcontroller is connected to the EN/SET pin. The user interface is provided by three buttons: DATA, FLASH, and MOVIE. The modes of operation are detailed in Table 1. The FLASH button generates a flash pulse. By default, the FLASH button generates a pulse at full current. The MOVIE button toggles on/off movie mode illumination. The DATA button is used to set different current levels. When the DATA button is held down, the MCU will auto-cycle through the available brightness level settings after a short delay. Some functions require that multiple buttons are pressed and released together. User Interface Functionality Button(s) Pushed1 Description DATA Increments through the 16 data settings. Hold down to auto-cycle (does not turn LED on, just sets data). FLASH2 Generate flash pulse. Current level determined by DATA and HI/LO settings (defaults to HI scale, DATA 1). Trim-pot VR4 sets duration. MOVIE Toggle on/off movie mode illumination. Current level determined by DATA and HI/LO settings. Leave on to see effects of changing DATA and HI/LO settings. DATA + MOVIE FLASH + MOVIE DATA + FLASH + MOVIE Independent channel control; increment through addresses 0, 1, 2. HI/LO register control. Toggle through the four HI/LO register settings. Reset, shutdown. Table 1: User Interface Functionality. 1. The '+' sign indicates that these buttons are all pressed and released together. 2. Flash pulse duration is adjustable from 10ms to 2 seconds. Rotate trim-pot VR4 clockwise to reduce the duration. 2 EV-127.2006.04.1.0 EV-127 AAT3172 EVAL: High Current LED Flash Driver Charge Pump IC Printed Circuit Board Figure 2: AAT3172 Evaluation Board Top Layer (not to scale). Figure 3: AAT3172 Evaluation Board Bottom Layer (not to scale). EV-127.2006.04.1.0 3 EV-127 AAT3172 EVAL: High Current LED Flash Driver Charge Pump IC AAT3172 EVAL Component Listing Component Part Number Description U1 AAT3172 U2 PIC12F675 Tri-mode High Efficiency Charge Pump for AnalogicTech White LED Flash; TDFN33-12 Package 8-Bit CMOS, FLASH-Based µC; Microchip 8-Pin PDIP Package High Brightness Flash LED Lumileds 1K, 5%, 1/4W; 1206 Vishay 1µF, 10V, X5R, 10%; 0603 Murata 2.2µF, 10V, X5R, 10%; 0603 Murata 4.7µF, 6.3V, X5R, 10%; 0603 Murata 1µF, 10V, X5R, 10%; 1206 Murata 330K, 5%, 1/4W; 1206 Vishay 100K, 5%, 1/4W; 1206 Vishay 220K, 5%, 1/4W; 1206 Vishay 10K POT; 3mm Squared SMD Panasonic-ECG Green LED; 1206 Chicago Miniature Lamp Red LED; 1206 Chicago Miniature Lamp Connecting Header, 2mm Sullins Electronics Switch Tact, SPST, 5mm ITT Industries D1 R1 - R3 C1 - C2 C3 C4 C7 R4 - R5 R6 R7 VR4 LED0 LED7 J1 - J2 SW1 - SW3 LXCL-PWF1 Chip Resistor GRM18 GRM18 GRM18 GRM31 Chip Resistor Chip Resistor Chip Resistor EVN-5ESX50B14 CMD15-21UGC/TR8 CMD15-21SRC/TR8 PRPN401PAEN PTS645TL50 Manufacturer Table 2: Component Listing. © Advanced Analogic Technologies, Inc. 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