PAM2805AF

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PAM2805 Document number: DSxxxxx Rev. 1 - 0 1 of 9 www.diodes.com July 2013 © Diodes Incorporated PAM2805 A Product Line of Diodes Incorporated 3-MODES/ 3W WLED DRIVER WITH 1 OR 2 CELL BATTERY Description The PAM2805 is a step-up DC-DC WLED driver with 3 modes cycling function (100% brightness,25% brightness and 8.5Hz blinking). The unique 3 modes cycling function can eliminate the needs of extra functional MCU or IC. The PAM2805 can deliver up to 750mA output current by setting an external resistor. The PAM2805 switches at a 1.0MHz constant frequency, allowing for the use of small value external inductor and ceramic capacitors. A low 95mV feedback voltage reduces the power loss in the RS for better efficiency. With its internal 2A, 100mΩ device can provide high efficiency even at heavy load. The PAM2805 is available in TSOT26 package. Features  3 Modes Cycling Function: Bright Dimming Blinking Power Off <5S Power Off <5S Power Off <5S  Reset to Bright Mode if Power Off time More Than 5S  Adjustable Output Current: Up to 750mA  8.5Hz Blinking Mode  Low Start-Up Voltage: 0.9V(typ)  Low SW on Resistance: 100mΩ  Over Temperature Protection  Over Voltage Protection  TSOT26 Package  Pb-Free Package Pin Assignments Applications  White LED Torch (Flashlight) Typical Applications Circuit ILED + 95mV/RS Top View TSOT26

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PAM2805 Document number: DSxxxxx Rev. 1 - 0 2 of 9 www.diodes.com July 2013 © Diodes Incorporated PAM2805 A Product Line of Diodes Incorporated Pin Description Pin Number Pin Name Function 1 VIN Input Voltage 2 GND Power Ground 3 BLK Connect A 1µF CAP for blinking 4 FB Feedback 5 VOUT Output Voltage 6 SW Connected to an internal NMOS switch Block Diagram Absolute Maximum Ratings (@TA = +25°C, unless otherwise specified.) These are stress ratings only and functional operation is not implied. Exposure to absolute maximum ratings for prolonged time periods may affect device reliability. All voltages are with respect to ground. Parameter Rating Unit Supply Voltage 6 V Output Voltage 6 Storage Temperature Range -65 to +150 °C Lead Temperature (Soldering, 5 sec) 300 Recommended Operating Conditions (@TA = +25°C, unless otherwise specified.) Parameter Rating Unit Operation Temperature Range -40 to +85 °C Junction Temperature Range -40 to +125

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PAM2805 Document number: DSxxxxx Rev. 1 - 0 3 of 9 www.diodes.com July 2013 © Diodes Incorporated PAM2805 A Product Line of Diodes Incorporated Thermal Information Parameter Symbol Package Max Unit Thermal Resistance (Junction to Case) θJC TSOT26 130 °C/W Thermal Resistance (Junction to Ambient) θJA TSOT26 250 Internal Power Dissipation @ TA = 25°C PD TSOT26 400 mW Electrical Characteristics (@TA = +25°C, L = 2.2µH, CIN = 10µF, COUT = 10µF, CBLK = 1µF, VF = 3.4V unless otherwise specified.) Parameter Symbol Test Conditions Min Typ Max Units Input Voltage Range VIN 0.9 VF -0.2 (Note 1) V Feedback Voltage VFB 90 95 100 mV Start-Up Voltage VSTART VIN: 0V →3V, ILED = 200mA 0.9 V Hold Voltage VHOLD VIN: 3V → 0V, ILED: 750mA → 100mA 0.7 V Oscillator Frequency fOSC 0.85 1.0 1.15 MHz Over Temperature Shutdown OTS 150 °C Over Temperature Hysteresis OTH 30 °C Maximum Output Current Range IO(MAX) VIN = 2.4V 750 mA Quiescent Current IQ ILED = 0mA, VO = 3.4V, Device Switching at 1MHz 1 3 mA Switch On Resistance RDS(ON) VO = 3.4V 0.1 Ω Current Limit ILIM VO = 3.4V 2 A Over Voltage Protection (VOUT) VOVP 4.5 V Blinking Frequency FBLK CBLK = 1µF 8.5 10 Hz Note: 1. VF ---LED forward voltage

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PAM2805 Document number: DSxxxxx Rev. 1 - 0 4 of 9 www.diodes.com July 2013 © Diodes Incorporated PAM2805 A Product Line of Diodes Incorporated Typical Performance Characteristics (@TA = +25°C, L = 2.2µF, CIN = 10µF, COUT = 10µF, CBLK = 1µF, unless otherwise specified.)

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PAM2805 Document number: DSxxxxx Rev. 1 - 0 5 of 9 www.diodes.com July 2013 © Diodes Incorporated PAM2805 A Product Line of Diodes Incorporated Typical Performance Characteristics (cont.) (@TA = +25°C, L = 2.2µF, CIN = 10µF, COUT = 10µF, CBLK = 1µF, unless otherwise specified.)

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PAM2805 Document number: DSxxxxx Rev. 1 - 0 6 of 9 www.diodes.com July 2013 © Diodes Incorporated PAM2805 A Product Line of Diodes Incorporated Application Information Inductor Selection The PAM2805 can use small value inductors due to its switching frequency of 1 MHz. The value of inductor will focus in the range of 2.2µH to 4.7µH for most PAM2805 applications. In typical high current white LED applications, it is recommended to use a 4.7µH inductor. The inductor should have low DCR (DC resistance) to minimize the I2R 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 PAM2805. For good input decoupling, Low ESR (equivalent series resistance) capacitors should be used at the input. At least 2.2µF input capacitor is recommended for most applications. A minimum output capacitor value of 6.8µF is recommended under normal operating conditions, while a 10µF-22µF capacitor may be required for higher power LED current. A reasonable value of the output capaci tor 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 PAM2805 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 PAM2805. 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. SS22 is recommended Schottky diode for rectifier. LED Current Setting The LED current is set by the single external Rs resistor connected to the FB pin as shown in the typical application circuit on Page 1. The typical FB reference is internally regulated to 95mV. The LED current is 95mV/R1. It's recommended to use a 1% or better precision resistor for the better LED current accuracy. The formula for RS selection is shown as follows:     V3VatmAI/mV95R INLEDS  Typically, for 1W(330mA) and 3W(750mA) LED light applications, the RS are 0.288Ω and 0.127Ω respectively. 3 Modes Cycling The PAM2805 has three modes: 100% brightness, 25% brightness and blinking (typical 8.5Hz). The mode change is triggered by power on/off actions and cycles in the following sequence: bright, dimming, blinking and back to bright mode. The PAM2805 will reset to the bright mode after being power off for more than 5 seconds. Low Voltage Start-Up and Soft-Start The PAM2805 has a build-in low voltage startup circuit for the best battery life solution. It can start up at 0.9V VIN typically when the preset LED current is 200mA. The soft-start function is made by clamping the output voltage of error amplifier with another voltage source which increases slowly from zero to near VIN dur ing the soft-start period. Therefore, the duty cycle of the PWM will be increased from zero to maximum in this period. The charging time of the inductor will be limited by the smaller duty so that the inrush current can be reduced to an acceptable value. Over Voltage Protection The output voltage of PAM2805 is monitored by Over Voltage Protection circuit. Once VOUT goes over VOVP, typically 4.5V, the power NMOS is turned off and SW pin stops switching. Then, the VOUT is clamped to around VOVP. Over Current Protection The inductor current during charging period is detected by a current sensing circuit. When the value is larger than current limiting ILIM, the power NMOS is turned off so that the inductor will be forced to leave charging stage and enter discharging stage. Therefore, the inductor peak current will not exceed ILIM, whose minimum value is 2A.

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PAM2805 Document number: DSxxxxx Rev. 1 - 0 7 of 9 www.diodes.com July 2013 © Diodes Incorporated PAM2805 A Product Line of Diodes Incorporated Application Information PCB Layout Guidelines As for all switching power supplies, the layout and components placement of the PAM2805 is an important step in the design; especially at high peak currents 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 switch pin by using wide and short traces for the main current path; the current sense resistor should be placed as close as possible between the ground pin and feedback pin. Ordering Information Part Number Marking Package Type Standard Package PAM2805AF ECXYW TSOT26 3000 Units/Tape&Reel Marking Information Top View TSOT26

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PAM2805 Document number: DSxxxxx Rev. 1 - 0 8 of 9 www.diodes.com July 2013 © Diodes Incorporated PAM2805 A Product Line of Diodes Incorporated Package Outline Dimensions (All dimensions in mm.) TSOT26