High Efficiency Synchronous Step-Down Switching Regulator

The LTC1735-1 is a synchronous step-down switching regulator controller optimized for CPU power. 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. The output voltage is monitored by a power good window comparator that indicates when the output is within 7.5% of its programmed value, conforming to Intel Mobile CPU Specifications.

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 3.5V to 30V (36V maximum).

Pin defeatable Burst Mode™ operation provides high efficiency at low load currents while 99% duty cycle provides low dropout operation.

Features

LTC1735

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LTC1735-1

Power Good

Applications

* Notebook and Palmtop Computers, PDAs

* Power Supply for Mobile Pentium® III Processor with SpeedStep™ Technology

* Cellular Telephones and Wireless Modems

* Dual N-Channel MOSFET Synchronous Drive

* Programmable/Synchronizable Fixed Frequency

* VOUT Range: 0.8V to 7V

* Wide VIN Range: 3.5V to 36V Operation

* Very Low Dropout Operation: 99% Duty Cycle

* OPTI-LOOP™ Compensation Minimizes COUT

* ±1% Output Voltage Accuracy