The MCP1643-I/MS is a low start-up voltage synchronous boost LED Constant Current Regulator optimized to drive one LED with constant current that operates from one and two-cell alkaline and NiMH/NiCd batteries. The compact high-efficiency fixed frequency step-up converter can also drive two red/green/yellow series connection LEDs. Low-voltage technology allows the regulator to start-up without high-output voltage and load-current overshoot from a low 0.65V input. High efficiency is accomplished by integrating the low resistance N-channel boost switch and synchronous P-channel switch. All compensation and protection circuitry are integrated to minimize external components. The internal feedback (VFB) voltage is set to 120mV for low power dissipation when sensing and regulating LED current. The device features an output over-voltage protection that limits the output voltage to 5V typical, in case the LED fails or output load is disconnected.
● Maximum input voltage <VLED <5V
● Over-voltage protection
● Minimal power loss on sense resistor
● Pulse-width modulation mode operation
● Internal synchronous rectifier
● Internal compensation
● Inrush current limiting
● Internal soft-start
● Shutdown - True load disconnect
● Dimming control by variable duty cycle
● Over-temperature protection
