MCP1643 1 MHz Low Start-up Voltage Synchronous Boost LED Constant Current Regulator Features Description 1.6A Typical Peak Input Current Limit MCP1643 is a compact, high-efficiency, fixed frequency, synchronous step-up converter optimized to Up to 550 mA LED Load Current drive one LED with constant current, that operates from Low Start-up Voltage: 0.65V (typical, 25 mA LED one and two-cell alkaline and NiMH/NiCd batteries. Current) The device can also drive two red/green/yellow series Low Operating Input Voltage: down to 0.5V connection LEDs. Maximum Input Voltage < V <5.0V LED Low-voltage technology allows the regulator to start up Maximum Output Voltage: without high-output voltage and load-current overshoot -5.0V from a low 0.65V input. High efficiency is accomplished - Overvoltage Protection by integrating the low resistance N-Channel Boost switch and synchronous P-Channel switch. All Low Reference Voltage: compensation and protection circuitry are integrated to -V = 120 mV FB minimize external components. - Minimal Power Loss on Sense Resistor The internal feedback (V ) voltage is set to 120 mV for FB Pulse-Width Modulation Mode Operation (1 MHz) low power dissipation when sensing and regulating Internal Synchronous Rectifier LED current. A single resistor sets the constant current Internal Compensation output that drives the LED load. Inrush Current Limiting The device features an output overvoltage protection Internal Soft-Start (240 s typical) that limits the output voltage to 5.0V typical, in case the Shutdown (EN = GND): LED fails or output load is disconnected. - True Load Disconnect The LED will either be turned OFF or turned ON using - Dimming Control by Variable Duty Cycle the enable input. A True Output Load Disconnect mode Shutdown Current: 1.2 A (typical) provides input-to-output isolation while Shutdown (EN = GND) by removing the normal boost regulator Overtemperature protection diode path from input to output. Shutdown state Packages: consumes 1.2 A from input at room temperature. - MSOP-8 The LED can be turned on and off with a variable duty - 2x3 DFN-8 cycle pulse-width modulation (PWM) signal applied to the EN pin for dimming applications. Applications The device also features a thermal shutdown at One and Two Cell Alkaline and NiMH/NiCd +150C, with +25C hysteresis. Portable LED Lighting Products Two package options, MSOP-8 and 2x3 DFN-8, are LED Flashlight and Head Lamps available. Rechargeable Flashlights Package Types Wall LED Lamps with Motion Detectors MCP1643 MCP1643 LED supply for backlights MSOP-8 2x3 DFN* General LED constant current applications V EN 1 8 IN EN 1 8 V IN V 2 7 S S EP V FB GND 2 7 GND FB 9 NC P 3 6 GND NC 3 P 6 GND V 4 5 SW OUT V 4 SW 5 OUT * Includes Exposed Thermal Pad (EP), see Table 3-1. 2013 Microchip Technology Inc. DS20005208A-page 1MCP1643 Typical Applications L 1 4.7 H 0.12V I = ----------------- LED R SET C I =25mA LED IN SW 4.7...10 F V OUT LED V IN C OUT MCP1643 + 4.7 F V FB R SET 4.7 EN GND - ON L 1 OFF 4.7 H WHITE LED I =360 mA C LED IN SW 4.7...10 F V OUT V IN R C EN OUT MCP1643 + 1M 20 F V FB R SET 0.33 EN - GND ON/OFF + - R Minimum and Maximum Limits for I in Regulation, with 6% Tolerance SET LED 10 1000 I LED MAX I LED MAX R for I SET LED MIN 1 100 R for I SET LED MAX I LED MIN WHITE LED I LED MIN o T = +25 C A 0.1 10 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3 Input Voltage (V) DS20005208A-page 2 2013 Microchip Technology Inc. ALKALINE R () SET NIMH 1.2V NIMH 1.2V LED Current (mA)