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LTC3809 - No Rsense, Low EMI, Synchronous DC/DC Controller

The LTC3809 is a synchronous step-down switching regulator controller that drives external complementary power MOSFETs using few external components. The constant frequency current mode architecture with MOSFET VDS sensing eliminates the need for a current sense resistor and improves efficiency.

For noise sensitive applications, the LTC3809 can be externally synchronized from 250kHz to 750kHz. Burst Mode is inhibited during synchronization or when the SYNC/ MODE pin is pulled low to reduce noise and RF interference. To further reduce EMI, the LTC3809 incorporates a novel spread spectrum frequency modulation technique.

Burst Mode operation provides high efficiency operation at light loads. 100% duty cycle provides low dropout operation, extending operating time in battery-powered systems.

The switching frequency can be programmed up to 750kHz, allowing the use of small surface mount inductors and capacitors.

The LTC3809 is available in the tiny footprint thermally enhanced DFN and 10-lead MSOP packages.

Features No Current Sense Resistor Required Selectable Spread Spectrum Frequency Modulation for Low Noise Operation Constant Frequency Current Mode Operation for Excellent Line and Load Transient Response True PLL for Frequency Locking or Adjustment (Frequency Range: 250kHz to 750kHz) Wide VIN Range: 2.75V to 9.8V Wide VOUT Range: 0.6V to VIN 0.6V ±1.5% Reference Low Dropout Operation: 100% Duty Cycle Selectable Burst Mode/Pulse Skipping/Forced Continuous Operation Auxiliary Winding Regulation Internal Soft-Start Circuitry Output Overvoltage Protection Micropower Shutdown: IQ = 9µA Tiny Thermally Enhanced Leadless (3mm × 3mm) DFN and 10-lead MSOP Packages Typical Application

Applications 1- or 2-Cell Lithium-Ion Powered Devices Portable Instruments Distributed DC Power Systems Packaging

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