A8133 HIGH EFFICIENCY, HIGH POWER WHITE LED DRIVER 1MHz FREQUENCY, INTERNAL 2A MOSFET SWITCH

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1 DESCRIPTION The is a boost DC-DC converter that delivers a regulated output current. The switches at a 1.0MHz constant frequency, allowing for the use of small value external inductor and ceramic capacitors. The features to drive high power white LEDs up to 1A from two AA batteries. The LED current can be programmed by the external current sense resistor, which connected between the feedback pin (FB) and ground. A low 95mV feedback voltage reduces the power loss in the sense resistor for better efficiency. The can provide high efficiency even at heavy load with its internal 2A, 100mΩ NMOS switch. LED dimming can be done by using a DC voltage applied to the FB pin and a pulse width modulation (PWM) signal applied to the FB pin or SHDN pin. During the shutdown mode, the feedback resistor and the load are completely disconnected and the current consumption is reduced to less than 1uA. FEATURES High efficiency: up to 90% Internal 2A MOSFET Switch 1.0MHz Switching Frequency Uses Small, Low Profile External Components Low Start-Up Voltage: 0.9V Low RDS(ON): 100mΩ (TYP.) LED Disconnect During Shutdown Open LED Protection Over Temperature Protection Available in SOT-26 package APPLICATION High Power LED Constant Current Source Constant Voltage Flash for DSC, Mobile phone, PDA Flashlight for WLED Torch and Lamp Typical Application The is available in SOT-26 package. ORDERING INFORMATION Package Type Part Number SOT-26 E6 E6R-XXX E6VR-XXX XXX: Feedback Voltage 095=95mV (Typical) Note V: Green Package R: Tape & Reel AiT provides all Pb free products Suffix V means Green Package WLED Current Rs 1W 350mA 0.27Ω 3W 750mA 0.12Ω REV1.2 - JAN 2007 RELEASED DEC 2008 REVISED

2 PIN DESCRIPTION Top View Pin # Symbol Function 1 SW Switch 2 GND Ground 3 FB Feedback 4 SHDN Shutdown 5 VOUT Output 6 VIN Input REV1.2 - JAN 2007 RELEASED DEC 2008 REVISED

3 ABSOLUTE MAXIMUM RATINGS Input Voltage -0.3 to 6V SW Voltage -0.3 to 6V SHDN, FB Voltage -0.3 to 6V Output Voltage -0.3 to 6V Junction Temperature -40 ~+125 Ambient Temperature Range -40 ~+85 Thermal Resistance (Junction to Case) 130 /W Thermal Resistance (Junction to Ambient) 250 /W Internal Power Dissipation (θjc) 400 mw Operating Temperature Range (θja) -40 to 85 Storage Temperature range (PD) -65 to 125 Lead Temperature (soldering, 10seconds), 300 Stresses above may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or any other conditions beyond those indicated in the Electrical Characteristics are not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. REV1.2 - JAN 2007 RELEASED DEC 2008 REVISED

4 ELECTRICAL CHARACTERISTICS (VIN=3.6V, VOUT=1.8V, Normal Process Corner, TA=27 ; unless otherwise specified.) Symbol Parameter Conditions Min Typ Max Unit VFB Feedback Voltage mv FOSC Oscillator Frequency MHZ VSH SHDN Input High VIN = 1.8V 1.0 V VSL SHDN Input Low VIN = 1.8V 0.4 V OTS Over Temperature Shutdown 150 OTH Over Temperature Hysteresis 15 VIN Input Voltage Range 0.9 VF-0.2 (Note1) V VOUT Output Current Range 750 ma IQ ILED = 0mA, VOUT = 3.4V, Quiescent Current 1 3 ma Device Switching at 1MHZ ISD Shutdown Current Shutdown mode 1 ua RDSON Switch on Resistance VOUT = 3.4V 0.13 Ω ILIM Current Limit VOUT = 3.4V 2 A Note1: VF the LED forward voltage REV1.2 - JAN 2007 RELEASED DEC 2008 REVISED

5 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25, L= 2.2uH, CIN = 10u, COUT = 10uF 1. LED Power Efficiency vs. Input Voltage 2. DC Input Current vs. Input Voltage 3. LED Current vs. Input Voltage 4. LED Power Efficiency vs. LED Current 5. Feedback Voltage vs. Temperature LED = 350mA 6. Feedback Voltage vs. Input Voltage LED = 350mA REV1.2 - JAN 2007 RELEASED DEC 2008 REVISED

6 7. Switching Waveform 8. Start-Up Waveform 9. Over Voltage Protection REV1.2 - JAN 2007 RELEASED DEC 2008 REVISED

7 BLOCK DIAGRAM REV1.2 - JAN 2007 RELEASED DEC 2008 REVISED

8 DETAILED INFORMATION Inductor Selection The can use small value inductors due to its switching frequency of 1 MHZ. The value of inductor focuses in the range of 1.5uF to 4.7uH for most applications. In typical high current white LED applications, it is recommended to use a 4.7uH inductor. The inductor should have low DCR (DC resistance) to minimize the I 2 R power loss, and it requires a current rating of 2A to handle the peak inductor current without saturating. Capacitor Selection An input capacitor is required to reduce the input ripple and noise for proper operation of the. For good input decoupling, low ESR (equivalent series resistance) capacitors should be used at the input. At least 2.2uF input capacitor is recommended for most application. A minimum output capacitor value of 4.7uF is recommended under normal operating conditions, while a 10uF-22uF capacitor may be required for higher power LED current. A reasonable value of the output capacitor depends on the LED current. The ESR of the output capacitor is the important parameter to determine the output voltage ripple of the converter, so low ESR capacitors should be used at the output to reduce the output voltage ripple. The small size of ceramic capacitors is an excellent choice for applications. The X5R and X7R types are preferred because they maintain capacitance over wide voltage and temperature ranges. Diode Selection It s indispensable to use a Schottky diode rated at 2A with the. Using a Schottky diode with a lower forward voltage drop is better to improve the power LED efficiency, and its voltage rating should be greater than the output voltage. REV1.2 - JAN 2007 RELEASED DEC 2008 REVISED

9 LED Dimming Control Dimming Control Using a DC Voltage to FB Pin. One method for dimming the LEDs is to apply a variable DC voltage through a resistor to the FB pin of the. The dimming control with a DC voltage is shown in the Fig 1. The DC voltage artificially raises the FB pin voltage, with the DC voltage increasing, the voltage across R2 increases and the voltage Rs decreases, which therefore lowers the LED current. The values of resistor R1 and R2 should be large enough to make the current from the DC source much smaller than the LED current while much larger than the FB leakage current. When VDC ranges from 0V to 2V, the resistors in the figure will set the LED current from 0mA to 350mA. Fig 1. Dimming Control Using a DC Voltage to FB Pin Dimming Control Using a PWM signal to FB Pin. By using the PWM signal to FB pin as shown in the Fig 2., the LED turns on or off and its current operates at either 0mA or the set maximum current. The PWM signal can be considered as an adjustable DC voltage. As the PWM duty cycle increases, the LED current decreases. Typically, the PWM frequency ranges from 5KHZ to 40KHZ. Fig 2. Dimming Control Using a PWM signal to FB Pin REV1.2 - JAN 2007 RELEASED DEC 2008 REVISED

10 Dimming Control Using a PWM signal to SHDN Pin. With the PWM signal applied to the SHDN pin of the, the LED turns on or off. When the SHDN pin is high, the LED turn on and its current is at the set maximum current; when the SHDN pin is low, the LED turn off and its current turns to 0mA. The average LED current increase proportionally with the PWM duty cycle. A0% duty cycle produces 0mA of LED current; a 100% duty cycle corresponds to the set maximum current. The magnitude of the PWM signal should be higher than the SHDN input high (VSH). The typical frequency of the PWM signal ranges from 100HZ to 1KHZ. Fig 3. and Fig 4. shows the LED current with the PWM duty cycle set to 50% and the PWM frequency set respectively to 100HZ and 1KHZ. Fig 5. shows the LED current versus the PWM duty cycle, setting the PWM frequency 100HZ Fig 3. Dimming Control Using a PWM Signal to SHDN Pin, 100Hz Fig 4. Dimming Control Using a PWM Signal to SHDN Pin, 1KHz REV1.2 - JAN 2007 RELEASED DEC 2008 REVISED

11 Fig 5. LED Current vs. Duty Cycle LED Dimming Example 1. Capacitor C1 is optional. 2. The LED Current can be adjusted by adjusting the variable resistor R For setting the LED Current Between 0mA to 30mA, the value of R1 to R10 should be 2.2Ω. REV1.2 - JAN 2007 RELEASED DEC 2008 REVISED

12 PCB Layout Guidelines See Fig 6. typical application, as for all switching power supplies, the layout and components placement of the is an important step in the design; especially at high peak current and high switching frequencies. The input capacitor and output capacitor should be placed respectively as close as possible to the input pin and output pin of the IC; the inductor and schottky diode should be placed as close as possible to the main current path; the current sense resistor should be placed as close as possible between the ground pin and feedback pin. Fig 6. Typical Application REV1.2 - JAN 2007 RELEASED DEC 2008 REVISED

13 PACKAGE INFORMATION Dimension in SOT-26 Package (Unit: mm) Tape Dimension Reel Dimension REV1.2 - JAN 2007 RELEASED DEC 2008 REVISED

14 IMPORTANT NOTICE AiT Semiconductor Inc. (AiT) reserves the right to make changes to any its product, specifications, to discontinue any integrated circuit product or service without notice, and advises its customers to obtain the latest version of relevant information to verify, before placing orders, that the information being relied on is current. AiT Semiconductor Inc.'s integrated circuit products are not designed, intended, authorized, or warranted to be suitable for use in life support applications, devices or systems or other critical applications. Use of AiT products in such applications is understood to be fully at the risk of the customer. As used herein may involve potential risks of death, personal injury, or servere property, or environmental damage. In order to minimize risks associated with the customer's applications, the customer should provide adequate design and operating safeguards. AiT Semiconductor Inc. assumes to no liability to customer product design or application support. AiT warrants the performance of its products of the specifications applicable at the time of sale. REV1.2 - JAN 2007 RELEASED DEC 2008 REVISED