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.

Applications

* Bus Termination: DDR/QDR Memory, SSTL, HSTL,...

* Servers, RAID Systems

* Distributed Power Systems

* Synchronous Buck with General Purpose Boost

* 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