High Efficiency Synchronous Step-Down Switching Regulator

The LTC1735 is a synchronous step-down switching regulator controller that drives external N-channel power MOSFETs using a fixed frequency architecture. Burst Mode operation provides high efficiency at low load currents. The precision 0.8V reference is compatible with future generation microprocessors. OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values.

The operating frequency (synchronizable up to 500kHz) is set by an external capacitor allowing maximum flexibility in optimizing efficiency. A forced continuous control pin reduces noise and RF interference and can assist secondary winding regulation by disabling Burst Mode operation when the main output is lightly loaded.

Protection features include internal foldback current limiting, output overvoltage crowbar and optional short-circuit shutdown. Soft-start is provided by an external capacitor that can be used to properly sequence supplies. The operating current level is user-programmable via an external current sense resistor. Wide input supply range allows operation from 4V to 30V (36V maximum).

Features

LTC1735

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LTC1735-1

Power Good

Applications

* Notebook and Palmtop Computers, PDAs

* Cellular Telephones and Wireless Modems

* DC Power Distribution Systems

* Synchronizable/Programmable Fixed Frequency

* OPTI-LOOP™ Compensation Minimizes COUT

* ±1% Output Voltage Accuracy

* Dual N-Channel MOSFET Synchronous Drive

* Wide VIN Range: 4V to 36V Operation

* VOUT Range: 0.8V to 6V

* Internal Current Foldback

* Output Overvoltage Crowbar Protection

* Latched Short-Circuit Shutdown Timer with Defeat Option