Providing complete DDR power solutions and complying with DDR1/DDR2/DDR3 standards

December 21, 2011 – Linear Technology (Country Manager: Hong Sa-kwak) announced the release of a high-efficiency dual-output synchronous step-down DC/DC controller (Product Name: LTC3876). This product generates VDDQ supply voltage, VTT bus termination voltage, and VTTR reference voltage for DDR1/DDR2/DDR3 as well as future standard memory applications. The output of the primary channel generates VDDQ and can be programmed to provide 25A within a range of 2.5V to as low as 1V. The output of the secondary channel generates VTT and is characterized by providing superior load regulation accuracy and efficiency. An internal LDO provides a precision ±1.2% VTTR reference. Both VTT and VTTR are programmed by an internal resistor divider equivalent to half the VDDQ supply and operate from 1.25V to 0.5V to support all DDR standards. The VTT supply provides symmetric output current functionality, offering ±25A (sourcing/sinking) at VTT and ±50mA at VTTR.
The LTC3876 operates over an input voltage range of 4.5V to 38V. The switching frequency is programmable up to 2MHz, enabling the use of ultra-small external components. For noise-sensitive applications, the LTC3876 switching frequency can be synchronized with an external clock. The two channels can be phase-shifted at 0°, 90°, 180°, or 270°, reducing the number of input filter components and accommodating multi-phase applications composed of multiple ICs. The LTC3876 utilizes a controlled on-time valley current mode architecture. Additionally, it features functions such as output voltage tracking, programmable soft start, RSENSE or DCR current sensing, remote VDDQ sensing, and a power good output signal.
For optimal thermal performance, the LTC3876 is available in 38-pin thermally enhanced 5mm x 7mm QFN and TSSOP packages. The device is guaranteed to operate over a temperature range of -40° to 125°C. Pricing starts at $2.94 per unit for 1,000-piece orders. For more information, visit www.linear.com/product/LTC3876 .

Image Caption: Dual buck controller for DDR1/DDR2/DDR3 standards

Product Features: LTC3876

• High-efficiency synchronous operation: Up to 94%
• Dual output controller capable of up to 24A current
• Wide input operating voltage range: 4.5V ~ 38V
• VDDQ Output Voltage Range: 1V ~ 2.5V
• VTT Output Voltage Range: 0.5V ~ 1.25V
• ± 1.2% output voltage accuracy
• Selectable fixed operating frequency from 200kHz to 2MHz
• Synchronization with an external clock possible
• Programmable soft start or tracking
• Selectable 0°/90°/180°/270° phase shift between channels
• Low-profile 38-pin 5mm x 7mm QFN & TSSOP package