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Dual Synchronous Buck Controller Provides DDR Power Solution

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 (double data rate 1), 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 at up to 25A. The output of the second channel produces VTT and offers good load regulation accuracy. An internal low drop out 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 operates from an input voltage range of 4.5 to 38V. The switching frequency is programmable up to 2MHz and for noise-sensitive applications, it can be synchronised to an external clock. The two channels can be phase shifted at 0°, 90°, 180° or 270° to accommodate multi-phase applications with multiple ICs. The controller utilises a controlled on-time valley current mode architecture. Additional features include output voltage tracking, programmable soft start, RSENSE or DCR current sense, remote VDDQ sensing and a power good output signal. For optimal thermal performance, the controller is available in 38pin thermally enhanced 5x7mm QFN and thin-shrink small outline packages. This device is guaranteed for operation from -40 to 125°C.