Introduction The AAT8 EVAL board demonstrates the functionality of the AAT8 and its application as a high current white LED flash driver. The device provides 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 and delivered for combined drive current of ma (ma on each channel). Conversely, one flash LED may be driven with ma by combining the two flash currents sinks to drive a single LED. Through the I C interface, the AAT8 can be programmed with different movie mode currents, flash safety timer, individual channel On/Off and flash mode to movie mode ratio. This document describes the evaluation board and its accompanying user interface. In addition, a brief Getting Started section which has been included to help the user begin operating the evaluation board. A schematic of the complete circuit is shown in Figures and. The actual board layout is also provided in Figures and 4. For additional operation device details and I C programming information, please consult the AAT8 product datasheet. Figure : AAT8 Evaluation Board. Getting Started Power and IC Enable Connect an external power source (.V-4.V, typical battery operating range) to the VIN and GND terminals. A jumper labeled JP7 is inline with the VIN terminal; to turn power ON/OFF, place the jumper on JP7 to the ON position. The red LED should illuminate, indicating that power has been applied to the circuit. There is an additional jumper labeled JP that enables the AAT8. Once the AAT8 is enabled, the super capacitor will be charged up, and the LEDs are in the off state.
Preliminary Board Set-Up LED Drive Current The AAT8 has been set up and tested to provide ma maximum current for each current sink FLOUTA and FLOUTB. The maximum current sink current is set by R and has been set to 8.6kΩ for a maximum LED drive current of ma. For maximum drive current level below ma, R may be adjusted to a higher resistance value. Refer to the AAT8 datasheet for a table of set resistor values to program a desired flash current other than ma. The two current sinks can be operated independently to provide up to ma of LED drive control. The two current sinks may also be connected in parallel to sum the maximum LED drive current up to ma for one flash LED. Flash Timer The maximum flash duration is set by the capacitor C. The maximum flash time has been set to 6ms using a 47nF ceramic capacitor. C may be adjusted to increase or decrease the maximum full current flash time. The approximate flash time can be set by the following capacitor values: C = 6nF ms C = nf 4ms C = 47nF 6ms C = 74nF sec. Since the time out timer is a function of input voltage, the maximum time out time can vary over the specified.7v to 5.5V input voltage range. As input voltage increases, the time out function will decrease. Current and Voltage Measurement The AAT8 evaluation board has been designed with several jumpers that may be removed to measure system input and LED drive currents. The use of an oscilloscope and current probes are strongly suggested for measuring LED flash current due to the transient nature of this measurement and to reduce measurement errors induced by placing an ammeter in the circuit. Jumpers JP and JP: LED current measurement point. To measure LED current, remove the Ω jumpers and replace with a short loop of wire that is large enough in diameter to connect an oscilloscope current probe. If two current probes are available, the LED flash current for FLOUT and FLOUT can be observed simultaneously. Super Capacitor SC voltage may be monitored by using an oscilloscope or multimeter. The super cap voltage can be probed at the capacitor positive terminal or on the anode side of either flash LED. Jumper JP8: Input supply voltage and current can be monitored at JP8. Due to the transient nature of circuit operation, it is suggested to use a current probe to observe the circuit input current. To measure the input current, remove the Ω jumper at JP8 and replace with a short wire loop to connect an oscilloscope current probe. The input supply voltage may be probed at JP8 with either an oscilloscope or multimeter.
Jumpers JP and JP: Remove and replace with a short loop of wire to measure LED current with a current probe Jumper JP8: Remove and replace with a short loop of wire to measure input current with a current probe Figure : Current and Voltage Measurement Points. I C Interface and Control JP5 and JP6 allow probing and connection to the two I C interface data lines, JP5 for and JP6 for. I C interface data is programmed by the microcontroller U and its associated push button function switches SW, SW and SW. One may bypass the on-board controller and insert externally generated I C commands by removing the jumpers on JP5 and JP6 and connecting the respective external and signals to the center contacts of JP5 and JP6. Driving Flash LEDs The AAT8 evaluation board is initially set up to drive two flash LEDs with a maximum A current pulse. Since the AAT8 integrated current sinks operate with independent reference circuits, they may be used separately to drive two flash LEDs or they may be combined to power a single LED with up to A of current. To drive a single flash LED with A, remove either JP or FLOUT. Place the single flash LED to be driven in the FLOUT position on the PCB. Connect the two AAT8 current sink inputs in parallel by a short jumper wire soldered between the two PCB cathode pads of FLOUT and FLOUT. Remove JP Solder in place a jumper wire to connect FLOUT and FLOUT current sinks in parallel Figure : Connecting Current Sinks in Parallel to Drive One Flash LED at High Current Levels.
AAT8 Evaluation Board User Interface Functionality The user interface is provided by four push buttons: MMC, S.T., A/B, and. Definitions of the switch controls are given in Table. A summary of operational modes for each button is outlined in Table. Button MMC S.T. A/B Reset Description Movie Mode Control (SW): Sets movie mode current. Each switch closure will incrementally decrease the movie mode current stating at % to % (off) in 6 steps. Refer to the AAT8 datasheet for detailed explanations of movie mode operation. Set Safety Time (SW): Set Flash LED Safety timer. Each switch closure will decrease the flash safety timer in 6 steps. Refer to the AAT8 datasheet for detailed explanations of movie mode operation. Flash A/B select (SW): Toggles on/off each LED channel (FLOUT, FLOUT both or Off) for movie / torch mode operation. Manual Flash Enable (SW4): Initiates a flash from movie mode or an off state, it is returned to the off state after the timer is reached or after the is released. A master system Reset (press SW, SW and SW simultaneously) is required manually after each flash. Reset all data to the AAT8: Pressing and releasing SW, SW and SW simultaneously will reset all the registers of the AAT8 and turn off the LEDs regardless of the present operational mode. Table : Switch Control Definitions. Button(s) Pushed SW (MMC) SW (S.T.) SW (A/B) SW4 () SW + SW (F/M ratio) SW + SW + SW Description [Push/Release once per step] Movie mode LED current dimming control. Each switch closure will issue an I C command to increment the data of the Movie Mode Current Register Bits There are 6 steps in this register to step movie mode current from full scale to off. (Refer to the AAT8 product datasheet for additional information) [Push/Release once] Increases the data in the Flash Safety Timer register bits and sends an I C command; as a result the Flash LEDs safety timer factor is decreased from the default setting by C. (Refer to the AAT8 product datasheet for additional information) [Push/Release once] Movie mode LED on/off control. Increments the data of the Enable Register Bits to select FLOUT, FLOUT, both or off. [Push/Release once] Flash enable. Manually enables the AAT8 boost converter, initiates a single flash pulse, and starts the flash timer. [Push/Release once] Increment the data of Flash to Movie Mode Current Ratio Register Bits, but the Flash to Movie Mode Current Ratio is decreased. (Refer to the AAT8 product datasheet for additional information) [Push/Release once] Reset all registers to default. Table : User Interface Functionality (Interface Between AAT8 and the Microcontroller.) VOUT R JP JP VCC k Enable JP L µh 4 5 6 7 U CT EN AGND IN SW PGND RSET FLA FLGND FLB OUT 4 9 8 FL FL R.k R.k SC.55F Bal + Gnd C.µF C 47nF AAT8 TDFN-4 R 8.6k C.µF Figure 4: AAT8 Evaluation Board Schematic. 4
DC+ DC- VCC JP7 MCU JP8 Movie Mode Control Safety Timer A/B Control 4 5 4 5 4 5 SW SW SW R5 K R6 K R7 K 4 U VDD VSS GP5 GP GP4 GP GP GP PICF675 8 7 6 5 C4 µf R4 LED GRN R 4 5 LED RED R8 k SW4 JP4 R9 k JP5 R k JP6 R k Figure 5: AAT8 Evaluation Board Microcontroller Section Schematic. Figure 6: AAT8 Evaluation Board Top Layer. 5
Figure 7: AAT8 Evaluation Board Bottom Layer. 6
AAT8 Evaluation Board Bill of Materials Component Part Number Description Manufacturer U AAT8IWO High Power A Flash Driver; TDFN-4 package Skyworks U PICF675 8-bit CMOS, FLASH-based μc; 8-pin PDIP package Microchip SW SW4 PTS645TL5 Switch Tact, SPST, 5mm ITT Industries R Chip Resistor 8.6kΩ, %, /4W; 4 Vishay R9 Chip Resistor kω, %, /4W; 6 Vishay R, R5 - R8, R, R Chip Resistor kω, 5%, /4W; 6 Vishay R, R4 Chip Resistor Ω, 5%, /4W; 6 Vishay R, R Chip Resistor.kΩ, 5%, /4W; 85 Vishay JP, JP, JP8 Chip Resistor Ω, 5% Vishay C, C GRM88R7A5KE5.µF, V, X7R, 6 MuRata C GRM55R7C47KA 47nF, V, X7R, 4 MuRata C4 GRM85R6A5KE6 µf, V, X5R, 6 MuRata L SD8 R-R Drum Core, µh,.69a, 48mΩ 4x4x.mm Cooper Bussmann FL-FL * White Flash LED * SC HS6F.55F, 85mΩ CAP XX LED CMD5-SRC/TR8 Red LED; 6 Chicago Miniature Lamp LED CMD5-VGC/TR8 Green LED; 6 Chicago Miniature Lamp JP, JP4, JP5, JP6, JP7 PRPN4PAEN Conn. Header, mm zip Sullins Electronics Table : AAT8 Evaluation Board Component Listing. * Lumileds LXCL-PWM or LXCL-PWF4, OSRAM LW F65G, or Seoul Semiconductor FCW4ZD based on availability from the manufacturer. Copyright Skyworks Solutions, Inc. All Rights Reserved. Information in this document is provided in connection with Skyworks Solutions, Inc. ( Skyworks ) products or services. These materials, including the information contained herein, are provided by Skyworks as a service to its customers and may be used for informational purposes only by the customer. Skyworks assumes no responsibility for errors or omissions in these materials or the information contained herein. Skyworks may change its documentation, products, services, specifications or product descriptions at any time, without notice. Skyworks makes no commitment to update the materials or information and shall have no responsibility whatsoever for conflicts, incompatibilities, or other difficulties arising from any future changes. No license, whether express, implied, by estoppel or otherwise, is granted to any intellectual property rights by this document. Skyworks assumes no liability for any materials, products or information provided hereunder, including the sale, distribution, reproduction or use of Skyworks products, information or materials, except as may be provided in Skyworks Terms and Conditions of Sale. THE MATERIALS, PRODUCTS AND INFORMATION ARE PROVIDED AS IS WITHOUT WARRANTY OF ANY KIND, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHERWISE, INCLUDING FITNESS FOR A PARTICULAR PURPOSE OR USE, MERCHANTABILITY, PERFORMANCE, QUALITY OR NON-INFRINGEMENT OF ANY INTELLECTUAL PROPERTY RIGHT; ALL SUCH WARRANTIES ARE HEREBY EXPRESSLY DIAIMED. SKYWORKS DOES NOT WARRANT THE ACCURACY OR COMPLETENESS OF THE INFORMATION, TEXT, GRAPHICS OR OTHER ITEMS CONTAINED WITHIN THESE MATERIALS. SKYWORKS SHALL NOT BE LIABLE FOR ANY DAMAGES, IN- CLUDING BUT NOT LIMITED TO ANY SPECIAL, INDIRECT, INCIDENTAL, STATUTORY, OR CONSEQUENTIAL DAMAGES, INCLUDING WITHOUT LIMITATION, LOST REVENUES OR LOST PROFITS THAT MAY RESULT FROM THE USE OF THE MATERIALS OR INFORMATION, WHETHER OR NOT THE RECIPIENT OF MATERIALS HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. Skyworks products are not intended for use in medical, lifesaving or life-sustaining applications, or other equipment in which the failure of the Skyworks products could lead to personal injury, death, physical or environmental damage. Skyworks customers using or selling Skyworks products for use in such applications do so at their own risk and agree to fully indemnify Skyworks for any damages resulting from such improper use or sale. Customers are responsible for their products and applications using Skyworks products, which may deviate from published specifications as a result of design defects, errors, or operation of products outside of published parameters or design specifications. Customers should include design and operating safeguards to minimize these and other risks. Skyworks assumes no liability for applications assistance, customer product design, or damage to any equipment resulting from the use of Skyworks products outside of stated published specifications or parameters. Skyworks, the Skyworks symbol, and Breakthrough Simplicity are trademarks or registered trademarks of Skyworks Solutions, Inc., in the United States and other countries. Third-party brands and names are for identification purposes only, and are the property of their respective owners. Additional information, including relevant terms and conditions, posted at www.skyworksinc.com, are incorporated by reference. 7