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LT3740 - Wide Operating Range, Valley Mode, No RSENSE Synchronous Step-Down Controller

The LT3740 is a synchronous step-down switching regulator controller that drives N-channel power MOSFET stages. The controller uses valley current mode architecture to achieve very low duty cycles with excellent transient response without requiring a sense resistor.

The LT3740 includes an internal step-up converter to provide a bias 7.8V higher than the input voltage for the drive. This enables the part to work from an input voltage as low as 2.2V.

The XREF pin is an external reference input that allows the user to override the internal 0.8V feedback reference with any lower value, allowing full control of the output voltage during operation, output voltage tracking or soft-start.

The LT3740 has three current limit levels that can be chosen by connecting the RANGE pin to ground, open, and input respectively.

Features Wide VIN Range: 2.2V to 22V Internal Boost Provides 6V Gate Drive For VIN Down to 2.2V No Sensing Resistor Required Dual N-Channel MOSFET Synchronous Drive Valley Current Mode Control Optimized for High Step-Down Ratio Power Good Output Voltage Monitor 0.8V Reference Three Pin-Selected Current Limit Levels Constant Switching Frequency: 300kHz Programmable Soft-Start Output Voltage Tracking Available in 16-Pin 5mm × 3mm DFN Typical Application

Applications Notebook and Palmtop Computers, PDA Portable Instruments Distributed Power Systems Packaging

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