LTC3717-1

U U LTC3717-1 Wide Operating Range, No RSENSETM Step-Down Controller for DDR/QDR Memory Termination FEATURES s VOUT = 1/2 VREF s Adjustable and Symmetrical Sink/Source Current Limit up to 20A s True Current Mode Control with Optional Use of Sense Resistor s VON and ION Pins Allow Constant Frequency Operation During Input and Output Voltage Changes s ±0.65% Output Voltage Accuracy s Up to 97% Efficiency s Ultrafast Transient Response s 2% to 90% Duty Cycle at 200kHz s tON(MIN) ≤ 100ns s Stable with Ceramic COUT s Power Good Output Voltage Monitor s Wide VIN Range: 4V to 36V s Adjustable Switching Frequency up to 1.5MHz s Output Overvoltage Protection s Optional Short-Circuit Shutdown Timer s Available in a 5mm × 5mm QFN Package U APPLICATIO S s Bus Termination: DDR and QDR Memory, SSTL, HSTL, ... s Notebook Computers, Desktop Servers s Tracking/Margining Power Supply DESCRIPTIO The LTC®3717-1 is a synchronous step-down switching regulator controller for double data rate (DDR) and Quad Data RateTM (QDRTM) memory termination. The controller uses a valley current control architecture to deliver very low duty cycles with or without a sense resistor. Operating frequency is selected by an external resistor and is compensated for variations in VIN and VOUT. Forced continuous operation reduces noise and RF interference. Output voltage is internally set to half of VREF, which is user programmable. Fault protection is provided by an output overvoltage comparator and optional short-c...