DESCRIPTION

· The MCP1643 is a high-efficiency, fixed frequency, synchronous step-up converter designed for driving one LED with constant current from one and two-cell alkaline and NiMH/NiCd batteries.
· It features low-voltage technology enabling startup from a low 0.65V input without high-output voltage and load-current overshoot.
· Integrated low resistance N-Channel Boost switch and synchronous P-Channel switch enhance efficiency.
· Includes internal compensation and protection circuitry to minimize external components.
· Offers output overvoltage protection, thermal shutdown at +150°C, and two package options: MSOP-8 and 2x3 DFN-8.

FEATURES

· 1.6A typical peak input current limit and up to 550 mA LED load current.
· Operates with a low start-up voltage of 0.65V and can function down to 0.5V input voltage.
· Maximum input voltage < V LED < 5.0V and maximum output voltage of -5.0V with overvoltage protection.
· Low reference voltage (V FB = 120 mV) minimizes power loss on sense resistor.
· Features PWM mode operation at 1 MHz, internal synchronous rectifier, and internal soft-start (240 µs typical).
· Shutdown mode (EN = GND) ensures true load disconnect with a shutdown current of 1.2 µA.
· Dimming control via variable duty cycle PWM signal applied to the EN pin.

APPLICATIONS

· Suitable for one and two-cell alkaline and NiMH/NiCd portable LED lighting products.
· Ideal for LED flashlights, head lamps, rechargeable flashlights, and wall LED lamps with motion detectors.
· Used in LED supply for backlights and general LED constant current applications.