Electronic Design

Buck Controller Meets DDR1/DDR2/DDR3 Standards

The LTC3876 dual output synchronous step-down dc/dc controller generates the VDDQ supply voltage, VTT bus termination voltage, and the VTTR reference voltage for DDR1/DDR2/DDR3 and future standard memory applications. The output of the first channel produces VDDQ and can be programmed from 2.5V down to 1V up to 25A. The output of the second channel produces VTT. An internal LDO provides the precision ±1.2% VTTR reference. Both VTT and VTTR are programmable via an internal resistor divider equal to one-half the VDDQ supply and operate from 1.25V to 0.5V to support all DDR standards. The VTT supply offers symmetrical output current capability, with ±25A (sourcing/sinking) at VTT and ±50mA at VTTR. The LTC3876 operates from an input voltage range of 4.5V to 38V and switching frequency is programmable up to 2 MHz. Price is $2.94 each/1,000. LINEAR TECHNOLOGY CORP., Milpitas, CA. (800) 454-6327.

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