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LTC3808 - No RSENSE, Low EMI, Synchronous DC/DC Controller with Output Tracking

The LTC3808 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.

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. For noise sensitive applications, the LTC3808 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 LTC3808 incorporates a novel spread spectrum frequency modulation technique.

The LTC3808 is available in the tiny footprint thermally enhanced DFN package or 16-lead SSOP package.

Protected by U.S. Patents including 5481178, 5929620, 6580258, 6304066, 5847554, 6611131, 6498466. Other Patents pending.

Features Programmable Output Voltage Tracking Sense Resistor Optional Spread Spectrum Modulation for Low Noise Constant Frequency Current Mode Operation for Excellent Line and Load Transient Response 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 True PLL for Frequency Locking or Adjustment (Frequency Range: 250kHz to 750kHz) Selectable Burst Mode®/Pulse Skipping/Forced Continuous Operation Auxiliary Winding Regulation Internal Soft-Start Circuitry Power Good Output Voltage Monitor Output Overvoltage Protection Micropower Shutdown: IQ = 9µA Tiny Thermally Enhanced Leadless (4mm × 3mm) DFN or 16-lead SSOP Package Typical Application

Applications One or Two Cell Lithium-Ion Powered Devices Notebook and Palmtop Computers, PDAs Portable Instruments Distributed DC Power Systems Packaging

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