Linear Technology has introduced the LTC3876, a dual output synchronous step-down DC/DC controller that generates the VDDQ supply voltage, the VTT bus termination voltage and the VTTR reference voltage for DDR1, 2 and 3 applications. The output of the first channel produces VDDQ and can be programmed from 2.5 to 1V at up to 25A. The output of the second channel produces VTT and offers good load regulation accuracy and efficiency, claims the company. An internal low-dropout regulator provides the precision ±1.2% VTTR reference. Both VTT and VTTR are programmed by an internal resistor divider equal to one-half the VDDQ supply and operate from 1.25 to 0.5V to support all DDR standards. The VTT supply offers symmetrical output current capability, with ±25A at VTT and ±50mA at VTTR. The controller has an input voltage range of 4.5 to 38V and operates between -40 and 125°C. The switching frequency is programmable up to 2MHz allowing the use of small external components, says the company. The two channels can be phase shifted at 0, 90, 180 or 270°. Additional features include output voltage tracking, programmable soft start, RSENSE or direct-current resistance current sense, remote VDDQ sensing and a power good output signal. For optimal thermal performance, the controller is available in 38pin, 5x7mm QFN and thin SSOP packages.
