Evaluation Board for the AAT1282 2A Driver for High Intensity LED … · 2019-02-14 · L1 1µH 2.2µF C1 80.6k R1 FL1 VOUT FL2 0 JP1 0 JP2 47nF C3 5 IN 1 CT 6 SW OUT 8 2 EN 3 FLEN

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EV160EVALUATION BOARD DATA SHEET

Evaluation Board for the AAT1282 2A Driver for High Intensity LED Camera Flash

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202313A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 28, 2012

IntroductionThe AAT1282 EVAL board demonstrates the functionality of the AAT1282 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 2000mA (1000mA on each channel). Conversely, one flash LED may be driven with 2000mA by combining the two flash currents sinks to drive a single LED.

Through the I2C interface, the AAT1282 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 1 and 2. The actual board layout is also provided in Figures 3 and 4. For additional operation device details and I2C programming information, please consult the AAT1282 product datasheet.

Figure 1: AAT1282 Evaluation Board.

Getting Started

Power and IC EnableConnect an external power source (3.0V-4.2V, typical battery operating range) to the VIN and GND terminals. A jump-er labeled JP7 is inline with the VIN terminal; to turn power ON/OFF, place the jumper on JP7 to the “ON” position. The red LED1 should illuminate, indicating that power has been applied to the circuit.

There is an additional jumper labeled JP3 that enables the AAT1282. Once the AAT1282 is enabled, the super capacitor will be charged up, and the LEDs are in the off state.

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Preliminary Board Set-Up

LED Drive CurrentThe AAT1282 has been set up and tested to provide 1000mA maximum current for each current sink FLOUTA and FLOUTB. The maximum current sink current is set by R1 and has been set to 80.6kΩ for a maximum LED drive current of 1000mA. For maximum drive current level below 1000mA, R1 may be adjusted to a higher resistance value. Refer to the AAT1282 datasheet for a table of set resistor values to program a desired flash current other than 1000mA.

The two current sinks can be operated independently to provide up to 1000mA of LED drive control. The two current sinks may also be connected in parallel to sum the maximum LED drive current up to 2000mA for one flash LED.

Flash TimerThe maximum flash duration is set by the capacitor C3. The maximum flash time has been set to 600ms using a 47nF ceramic capacitor. C3 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:

C3 = 16nF ≈ 200msC3 = 31nF ≈ 400msC3 = 47nF ≈ 600msC3 = 74nF ≈ 1 sec.

Since the time out timer is a function of input voltage, the maximum time out time can vary over the specified 2.7V to 5.5V input voltage range. As input voltage increases, the time out function will decrease.

Current and Voltage MeasurementThe AAT1282 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 JP1 and JP2: LED current measurement point. To measure LED current, remove the 0Ω 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 FLOUT1 and FLOUT2 can be observed simultaneously.

• Super Capacitor SC1 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 opera-tion, it is suggested to use a current probe to observe the circuit input current. To measure the input current, remove the 0Ω 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.

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Jumpers JP1 and JP2: 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 2: Current and Voltage Measurement Points.

I2C Interface and ControlJP5 and JP6 allow probing and connection to the two I2C interface data lines, JP5 for SCL and JP6 for SDA. I2C interface data is programmed by the microcontroller U2 and its associated push button function switches SW1, SW2 and SW3. One may bypass the on-board controller and insert externally generated I2C commands by removing the jumpers on JP5 and JP6 and connecting the respective external SCL and SDA signals to the center contacts of JP5 and JP6.

Driving Flash LEDsThe AAT1282 evaluation board is initially set up to drive two flash LEDs with a maximum 1A current pulse. Since the AAT1282 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 2A of current.

To drive a single flash LED with 2A, remove either JP2 or FLOUT2. Place the single flash LED to be driven in the FLOUT1 position on the PCB. Connect the two AAT1282 current sink inputs in parallel by a short jumper wire soldered between the two PCB cathode pads of FLOUT1 and FLOUT2.

Remove JP2 Solder in place a jumper wire to connect FLOUT1 and FLOUT2 current sinks in parallel

Figure 3: Connecting Current Sinks in Parallel to Drive One Flash LED at High Current Levels.

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AAT1282 Evaluation Board User Interface FunctionalityThe user interface is provided by four push buttons: MMC, S.T., A/B, and FLEN. Definitions of the switch controls are given in Table 1. A summary of operational modes for each button is outlined in Table 2.

Button Description

MMCMovie Mode Control (SW1): Sets movie mode current. Each switch closure will incrementally decrease the movie mode current stating at 100% to 0% (off) in 16 steps. Refer to the AAT1282 datasheet for detailed explanations of movie mode operation.

S.T. Set Safety Time (SW2): Set Flash LED Safety timer. Each switch closure will decrease the flash safety timer in 16 steps. Refer to the AAT1282 datasheet for detailed explanations of movie mode operation.

A/B Flash A/B select (SW3): Toggles on/off each LED channel (FLOUT1, FLOUT2 both or Off) for movie / torch mode operation.

FLENManual 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 FLEN is released. A master system Reset (press SW1, SW2 and SW3 simultaneously) is required manually after each flash.

Reset Reset all data to the AAT1282: Pressing and releasing SW1, SW2 and SW3 simultaneously will reset all the registers of the AAT1282 and turn off the LEDs regardless of the present operational mode.

Table 1: Switch Control Definitions.

Button(s) Pushed Description

SW1 (MMC)

[Push/Release once per step] Movie mode LED current dimming control. Each switch closure will issue an I2C command to increment the data of the Movie Mode Current Register Bits There are 16 steps in this register to step movie mode current from full scale to off. (Refer to the AAT1282 product datasheet for additional information)

SW2 (S.T.)[Push/Release once] Increases the data in the Flash Safety Timer register bits and sends an I2C com-mand; as a result the Flash LEDs safety timer factor is decreased from the default setting by C3. (Refer to the AAT1282 product datasheet for additional information)

SW3 (A/B) [Push/Release once] Movie mode LED on/off control. Increments the data of the Enable Register Bits to select FLOUT1, FLOUT2, both or off.

SW4 (FLEN) [Push/Release once] Flash enable. Manually enables the AAT1282 boost converter, initiates a single flash pulse, and starts the flash timer.

SW1 + SW3 (F/M ratio)

[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 AAT1282 product datasheet for additional information)

SW1 + SW2 + SW3 [Push/Release once] Reset all registers to default.

Table 2: User Interface Functionality (Interface Between AAT1282 and the Microcontroller.)

C22.2µF

L1 1µH

2.2µFC1

80.6kR1

FL1

VOUT

FL2

0JP1

0JP2

47nFC3

IN5

CT1

SW6

OUT 8

EN2

FLEN3

PGND7

AGND4

SCL 9SDA 10FLB 11

FLGND 12FLA 13RSET 14

AAT1282 TDFN33-14

U1Enable

JP3

10k

R2

VCC

FLEN SDA

SCL

30.1kR12

30.1kR13

+ 1

Bal3

Gnd 2

SC1 0.55F

Figure 4: AAT1282 Evaluation Board Schematic.

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DC+

VDD1

GP52

GP43

GP34 GP2 5GP1 6GP0 7VSS 8

PIC12F675

U2 1µFC4

100kR9

330R3 12

345

0

FLENSW4

REDLED 1

12345

0Movie Mode ControlSW1

10KR6

GRNLED 2

330R4

DC-

0

JP8

JP4

10 kR8

SDAJP6

SCLJP5

MCUJP7

12 345

0Safety TimerSW2

10KR5

10kR10

10kR11

10KR7

1234 5

0A /B Control SW3

SCL SDAFLEN

VCC

Figure 5: AAT1282 Evaluation Board Microcontroller Section Schematic.

Figure 6: AAT1282 Evaluation Board Top Layer.

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Figure 7: AAT1282 Evaluation Board Bottom Layer.

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Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved.

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AAT1282 Evaluation Board Bill of Materials

Component Part Number Description ManufacturerU1 AAT1282IWO High Power 2A Flash Driver; TDFN33-14 package SkyworksU2 PIC12F675 8-bit CMOS, FLASH-based μC; 8-pin PDIP package Microchip

SW1 – SW4 PTS645TL50 Switch Tact, SPST, 5mm ITT IndustriesR1 Chip Resistor 80.6kΩ, 1%, 1/4W; 0402 VishayR9 Chip Resistor 100kΩ, 1%, 1/4W; 0603 Vishay

R2, R5 - R8, R10, R11 Chip Resistor 10kΩ, 5%, 1/4W; 0603 VishayR3, R4 Chip Resistor 330Ω, 5%, 1/4W; 0603 Vishay

R12, R13 Chip Resistor 30.1kΩ, 5%, 1/4W; 0805 VishayJP1, JP2, JP8 Chip Resistor 0Ω, 5% Vishay

C1, C2 GRM188R71A225KE15 2.2µF, 10V, X7R, 0603 MuRataC3 GRM155R71C473KA01 47nF, 10V, X7R, 0402 MuRataC4 GRM185R61A105KE36 1µF, 10V, X5R, 0603 MuRataL1 SD3812 1R0-R Drum Core, 1µH, 2.69A, 48mΩ 4x4x1.2mm Cooper Bussmann

FL1-FL2 * White Flash LED *SC1 HS206F 0.55F, 85mΩ CAP XXLED1 CMD15-21SRC/TR8 Red LED; 1206 Chicago Miniature LampLED2 CMD15-21VGC/TR8 Green LED; 1206 Chicago Miniature Lamp

JP3, JP4, JP5, JP6, JP7 PRPN401PAEN Conn. Header, 2mm zip Sullins Electronics

Table 3: AAT1282 Evaluation Board Component Listing.

* Lumileds LXCL-PWM1 or LXCL-PWF4, OSRAM LW F65G, or Seoul Semiconductor FCW401ZD based on availability from the manufacturer.

Documents

Evaluation Board for the AAT1282 2A Driver for High Intensity LED … · 2019-02-14 · L1 1µH 2.2µF C1 80.6k R1 FL1 VOUT FL2 0 JP1 0 JP2 47nF C3 5 IN 1 CT 6 SW OUT 8 2 EN 3 FLEN