EVALUATION BOARD DATASHEET EV-184 AHK1421 EVAL : S2Cwire Controlled, Serial LED Boost Driver Introduction The AHK1421 evaluation board demonstrates functionality of the AHK1421 and its application as a white LED backlight driver under AnalogicTech’s S2Cwire serial digital interface control. The AHK1421 is a high frequency, high efficiency, constant-current boost converter driving six white LEDs in series configuration. The input voltage is 2.7V to 5.5V, which is ideal for portable devices powered by single-cell lithium-ion/ polymer (Li-ion) batteries. The maximum LED current is set by an external resistor from 10 to 31mA. The AHK1421 is programmable with the S²Cwire interface, using an onboard microcontroller which is capable of brightening and dimming the LEDs in 32 discrete steps. This document describes the evaluation board and its accompanying user interface. A brief “Getting Started” section is included to help the user to begin operating the evaluation board. Board Pictures (a) Top (b) Bottom Figure 1: AHK1421 Evaluation Board EV-184.2011.05.1.0 www.analogictech.com 1 EVALUATION BOARD DATASHEET EV-184 AHK1421 EVAL : S2Cwire Controlled, Serial LED Boost Driver Board Schematic LX DS1 L1 VOUT 10µH U1 J1 AHK1421ICA 6 DC+ 3 2 1 2.7~5.5V J2 DC- VIN CIN 2.2µF LX OUT EN/SET 4 GND FB 1 D1 D2 5 COUT 2.2µF D3 D4 3 D5 D6 2 RFB 12.5 AHK1421 White LED Driver R4 51k V_MCU EN/SET R7 R8 R9 1k 1k 1k UP S2Cwire Microcontroller 1 2 3 4 U2 PIC12F675 VDD GP5 GP4 GP3 VSS GP0 GP1 GP2 C1 0.1µF 8 7 6 5 R5 1k LED1 Red R6 330 LED2 Green DOWN CYCLE Figure 2: AHK1421 Evaluation Board Schematic 2 www.analogictech.com EV-184.2011.05.1.0 EVALUATION BOARD DATASHEET EV-184 AHK1421 EVAL : S2Cwire Controlled, Serial LED Boost Driver Getting Started Setup (Figure 3) 1. Connect an input power source (to supply between 2.7V and 5.5V) to the board by placing the jumper, J1 on the left (Connects DC+ power to AHK1421). 2. Connect the DC+ power to the microcontroller VDD by using the jumper V_MCU. 3. Connect the EN/SET jumper to connect the microcontroller GPIOs to the AHK1421 EN/SET pins. 4. After all jumpers are in the correct position, apply power between 2.7V and 5.5V to the DC+ and DC- terminals to power on the AHK1421 (U1) and microcontroller (U2). The red LED (LED1) will illuminate when the microcontroller is powered. The green LED (LED2) will flicker when the three buttons to transfer S²C wire data for AHK1421 are operated. 5. Use the UP, DOWN and CYCLE buttons to vary the brightness of the 6 white LEDs using the EN/SET serial data S2Cwire interface Figure 3: AHK1421 Evaluation Board Measurement Configuration S2Cwire Control Short the EN/SET jumper to receive S2Cwire data generated by the microcontroller according to the status of the three buttons. The AHK1421 records the number of rising edges which control output current in EN/SET pin and change the value of output current from 20mA to 0.4mA when RFB is 12.5Ω •• UP button: The UP button increments the number of EN/SET rise edges from 1 to 32 each time this button is pushed. By holding down the button for more than 0.6 seconds, the microcontroller enters auto-increment mode. The LED will dim and wrap back after S2C wire data reaches 32. •• DOWN button: The DOWN button decrements the number of EN/SET rise edges from 32 to 1 each time this button is pushed. By holding down the button for more than 0.6 seconds, the microcontroller enters auto-decrement mode. The LED will brighten and wrap back after S2Cwire data reaches 1. •• CYCLE button: The button increments or decrements the number of EN/SET edges automatically and cyclically after a single push according to the previous EN edges up or down event. •• UP+DOWN+CYCLE button: EN/SET is set to 0V and the AHK1421 is shut down. All white LEDs are turned off. EV-184.2011.05.1.0 www.analogictech.com 3 EVALUATION BOARD DATASHEET EV-184 S2Cwire Controlled, Serial LED Boost Driver ILED (mA) AHK1421 EVAL : 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 S2Cwire Data Figure 4: S2Cwire Dimming Control at Maximum LED Current (20mA max) User Interface Functionality Button(s) UP DOWN CYCLE UP+DOWN+CYCLE Action Effect Increment the number of EN/SET edge; Toggles through the available dimming level settings for the backlighting section. Auto-increment the number of EN/SET edges up to 32 then wrap back to 1. Decrement the number of EN/SET edge; Toggles through the available brightness level settings for the backlighting section. Auto-decrement the number of EN/SET edges down to 1 then wrap back to 32 Push/Release once Push Hold 0.6 sec.+ Push/Release once Push Hold 0.6 sec.+ Push/Release once or Push Hold 0.6 sec.+ Push All Three and Hold Auto-cycle in direction last set Shut down Table 1: User Interface Functionality 4 www.analogictech.com EV-184.2011.05.1.0 EVALUATION BOARD DATASHEET EV-184 AHK1421 EVAL : S2Cwire Controlled, Serial LED Boost Driver Functional Testing and Evaluation Operational Waveform Figure 5 shows the waveform controlled by S2Cwire at 3.6V VIN when the code changes from 32 to 1.The ILED changes from 0.4mA (2% IMAX) to 20mA (IMAX). Channel Signal 1 2 3 4 VOUT EN/SET ILED IIN Figure 5: Operational Waveform under S²Cwire Control. Start up Figure 6 shows the AHK1421 startup waveform after adding rising edge on EN/SET. Soft start control makes the input current rise slowly. Channel Signal 1 2 3 4 SW VOUT ILED IIN Figure 6: Start Up Waveform. EV-184.2011.05.1.0 www.analogictech.com 5 EVALUATION BOARD DATASHEET EV-184 AHK1421 EVAL : S2Cwire Controlled, Serial LED Boost Driver Efficiency Curves Figure7 shows that the maximum efficiency is about 85% under 4.2V input voltage. Consult the AHK1421 product datasheet about the external diode selection. 90 88 86 84 82 80 Efficiency (%) 78 VIN = 3.6V 76 74 72 VIN = 4.2V 70 68 66 64 62 60 58 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 ILED (mA) Figure 7: Efficiency Curve Waveforms. 6 www.analogictech.com EV-184.2011.05.1.0 EVALUATION BOARD DATASHEET EV-184 AHK1421 EVAL : S2Cwire Controlled, Serial LED Boost Driver Printed Circuit Board (a) Top (b) Bottom Figure 8: AHK1421 Evaluation Board (not to Scale) AHK1421 EVAL Board Component Listing Component Part Number Description U1 AHK1421ICA U2 R6 RFB R5, R7, R8, R9 R4 CIN COUT C1 D1, D2, D3, D4, D5, D6 PIC12F675 GRM188R60J225KE01 GRM21BR61H225KA73L GRM188R71C104K RS-0805UW DS1 SS14L L1 LED1 LED2 CYCLE, UP, DOWN CDRH2D14-100 0805KRCT 0805KGCT 6*6*5 Chip RES S2C controlled, serial LED boost driver IC, TSOT23-6 8-bit CMOS, FLASH-Based uC;SOIC-8 RES 330Ω 1/4W 1% 0603 SMD RES 12.5Ω 1/4W 1% 0603 SMD RES 1KΩ 1/4W 1% 0603 SMD RES 51KΩ 1/4W 1% 0603 SMD Cap 2.2μF 0603 X5R 10V 10% Cap 2.2μF 0805 X7R 50V 10% Cap 0.1uF 0603 X7R 16V 10% 20mA White LED 0805 1.0AMP.Surface Mount Schottky Barrier Rectifiers POWER INDUCTOR 10μH SMD Red LED 0805 Green LED 0805 12V 50mA Push button Manufacturer AnalogicTech Microchip Yageo Murata Realstar TSC Sumida HB E-LT Table 2: AHK1421 Evaluation Board Bill of Materials. EV-184.2011.05.1.0 www.analogictech.com 7 EVALUATION BOARD DATASHEET EV-184 AHK1421 EVAL : S2Cwire Controlled, Serial LED Boost Driver Advanced Analogic Technologies, Inc. 3230 Scott Boulevard, Santa Clara, CA 95054 Phone (408) 737-4600 Fax (408) 737-4611 © 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. 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All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders. 8 www.analogictech.com EV-184.2011.05.1.0