EV-130 AAT1231 EVAL: Step-Up DC/DC Converter for White LED Backlight Applications

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Caren Paul
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1 for White Backlight Applications Introduction The AAT2 is a high frequency, high efficiency constant current boost converter driving up to six white s in series or up to twelve white s in parallel/series configuration. The input voltage is 2.7V to.v, which is ideal for portable devices powered by single-cell lithium-ion/polymer (Li-ion) batteries. With over-voltage protection and dynamically-programmable voltage control via AnalogicTech s patented Simple Serial Control (S 2 Cwire ) interface, the AAT2 is an ideal choice for white backlight applications. The AAT2 evaluation board provides a platform for test and evaluation of the AAT2 for white backlight applications driving six s. The AAT2 is programmable with the S 2 Cwire interface, using an onboard microcontroller which is capable of brightening and dimming the s in 26 discrete steps. The SELECT logic signal from the microcontroller provides a stepped load from.x to.0x of nominal output current, depending on the S 2 Cwire data register (default =.0x). 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. The board layout is also provided. For additional information, please refer to the AAT2 product datasheet. Schematic VCC R8 0 D7 RED Up Down Select SW SW2 SW R7 K R6 K R K 2 U2 VDD GP GP GP PIC2F67 VSS 8 GP0 7 GP 6 GP2 C µf R9 0 D8 GREEN (Select indicator) R 0K DC- DC+ J2 J L DS Schottky VOUT 2 J VCC JP C 2.2µF U VIN LIN 2 2 EN OVP SEL FB 0 VP N/C 6 SW PGND GND 9 8 SW 7 AAT2 2.2µH R D6 R2 226K R 2K D D D2 D D C2 2.2µF 0.Ω Figure : AAT2 Evaluation Board Schematic with Six White s and Microcontroller. EV

2 for White Backlight Applications Getting Started The ballast resistor (R) is set to 0.Ω on the evaluation board. This sets the maximum current to 20mA. I = V FB R Over-voltage protection is set to the maximum operation voltage (2V) to protect the IC from damage. There are three () buttons on the evaluation board. The modes of operation are detailed in Table. Each button controls a particular function. The SW (Up) button increments the number of EN/SET edges, and the AAT2 increases the FB pin voltage according to Table 2. By holding down the Up button for more than. seconds, the microcontroller enters auto-increment mode. The SW2 (Down) button decrements the number of EN/SET edges and the AAT2 decreases the FB pin voltage. By holding down the Down button for more than. seconds, the microcontroller enters auto-decrement mode. The SW (Select) button toggles High/Low on the SEL pin. A green (D8) indicates the status on the SEL pin. If the green turns ON, the SEL pin is set to High. If the green turns off, the SEL pin is set to Low. Figure 2 details the nominal current levels for SEL=High and SEL=Low settings with R=0.Ω. 2 Current (ma) 20 0 (Default) SEL = HIGH SEL = LOW S 2 Cwire Data Register Figure 2: Programming Current with R BALLAST = 0.Ω. Upon initial power-up and prior to S 2 Cwire programming, the default FB pin voltage is set at 0.V/0.V depending on the SEL pin logic level. The red (D7) should illuminate, indicating that power has been connected to the evaluation board. 2 EV

3 for White Backlight Applications User Interface Functionality Button(s) Pushed SW (Up) SW2 (Down) SW (Select) Description [Push/Release once] Increment the number of EN/SET edges. Toggles through the available brightness level settings for the backlighting section. [Holding. sec.+] Auto-increment one voltage level per second. [Push/Release once] Decrement the number of EN/SET edges. Toggles through the available dimming level settings for the backlighting section. [Holding. sec.+] Auto-decrement one voltage level per second. [Push/Release once] Toggles the SEL logic pin High/Low. Table : User Interface Functionality. Rising Clock SEL = Low SEL = High Edges/Data Reference Current (ma); Reference Current (ma); Register Voltage (V) R BALLAST = 0.Ω Voltage (V) R BALLAST = 0.Ω 0. (default).2 0. (default) Table 2: AAT2 S 2 Cwire Reference Feedback Voltage Control Settings with R BALLAST = 0.Ω (Assume Nominal Values). EV

4 for White Backlight Applications Printed Circuit Board Figure : AAT2 Evaluation Board Top Layer (not to scale). Figure : AAT2 Evaluation Board Bottom Layer (not to scale). EV

5 for White Backlight Applications AAT2 EVAL Component Listing Component Part Number Description Manufacturer U AAT2 Step Up DC-DC Converter for White AnalogicTech Backlight Applications; TSOPJW-2 Package U2 PIC2F67 8-bit CMOS, FLASH-Based µc; 8-Pin Microchip PDIP Package SW - SW PTS6TL0 Switch Tact, SPST, mm ITT Industries R Chip Resistor 0.Ω, %, /W; 060 Vishay R2 Chip Resistor 226kΩ, %, /W; 060 Vishay R Chip Resistor 2.kΩ, %, /W; 060 Vishay R Chip Resistor 0kΩ, %, /W; 060 Vishay R, R6, R7 Chip Resistor kω, %, /W; 080 Vishay R8, R9 Chip Resistor 0Ω, %, /W; 080 Vishay JP Chip Resistor 0Ω, %, 080 Vishay C GRM88R60J22KE0 2.2µF, 0V, XR, 060 MuRata C2 GRM2BR7E22KA7 2.2µF, 2V, X7R, 080 MuRata C GRM26R6A0KA0 µf, 0V, XR, 080 MuRata L SD8-2R2 2.2µH, Core Shield Cooper Electronics; Coiltronics DS BAT2W Schottky Diode; V R = 0V, I FM = 0.2A Diodes, Inc. SOD-2 D-D6 LW M67 White Hyper-Bright OSRAM D7 CMD-2SRC/TR8 Red ; 206 Chicago Miniature Lamp D8 CMD-2VGC/TR8 Green ; 206 Chicago Miniature Lamp J, J2, J PRPN0PAEN Connecting Header, 2mm Zip Sullins Electronics Table : AAT2 Evaluation Board Component Listing. EV

6 for White Backlight Applications Advanced Analogic Technologies, Inc. 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. Customers are advised 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. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders. Advanced Analogic Technologies, Inc. 80 E. Arques Avenue, Sunnyvale, CA 908 Phone (08) Fax (08) EV

7 Form#: FM-QA-00 Rev. 0

EV-110 AAT1157 EVAL 1MHz 1.4A Buck Regulator

EV-110 AAT1157 EVAL 1MHz 1.4A Buck Regulator Introduction The AAT1157 evaluation board demonstrates performance, along with the suggested size and placement of external components, for the AAT1157 integrated buck regulator. The external components