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LTC3718 - Low Input Voltage, DC/DC Controller for DDR/QDR Memory Termination

The LTC3718 is a high current, high efficiency synchronous switching regulator controller for DDR and QDR™ memory termination. It operates from an input as low as 1.5V and provides a regulated output voltage equal to (0.5)VIN. The controller uses a valley current control architecture to enable high frequency operation with very low on-times without requiring a sense resistor. Operating frequency is selected by an external resistor and is compensated for variations in VIN and VOUT. The LTC3718 uses a pair of standard 5V logic level N-channel external MOSFETs, eliminating the need for expensive P-channel or low threshold devices.

Forced continuous operation reduces noise and RF interference. Fault protection is provided by internal foldback current limiting, an output overvoltage comparator and an optional short-circuit timer. Soft-start capability for supply sequencing can be accomplished using an external timing capacitor. OPTI-LOOP® compensation allows the transient response to be optimized over a wide range of loads and output capacitors.

OPTI-LOOP is a registered trademark of Linear Technology Corporation. No RSENSE is a trademark of Linear Technology Corporation. QDR RAMs and Quad Data Rate RAMs comprise a new family of products developed by Cypress Semiconductor, IDT and Micron Technology, Inc.

Features Very Low VIN(MIN): 1.5V Ultrafast Transient Response True Current Mode Control 5V Drive for N-Channel MOSFETs Eliminates Auxillary 5V Supply No Sense Resistor Required Uses Standard 5V Logic-Level N-Channel MOSFETs VOUT(MIN): 0.4V VOUT Tracks 1/2 VIN or External VREF Symmetrical Source and Sink Output Current Limit Adjustable Switching Frequency tON(MIN) <100ns Power Good Output Voltage Monitor Programmable Soft-Start Output Overvoltage Protection Optional Short-Circuit Shutdown Timer Small 24-Lead SSOP Package Typical Application

Applications Bus Termination: DDR/QDR Memory, SSTL, HSTL,... Servers, RAID Systems Distributed Power Systems Synchronous Buck with General Purpose Boost Packaging

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