Linear Technology Launches 15V Dual 3A Monolithic Step-Down Regulator
DDR1, DDR2, DDR3 memory operation

Linear Technology's LTC3634 is a high-efficiency dual-channel monolithic synchronous step-down regulator that provides power supply and bus termination rails for DDR1, DDR2, and DDR3 SDRAM controllers. Operating over an input voltage range of 3.6V to 15V, the LTC3634 is ideal for 5V and 12V intermediate bus systems as well as dual-cell lithium-ion applications. The LTC3634 features a unique constant frequency/on-time control, current-mode architecture, which is ideal for driving DDR applications from a 12V input supply at high switching frequencies. The termination voltage VTT is set to ½ of VDDQ down to 0.6V with +1.6% accuracy. By combining a monolithic design with a high switching frequency of 4MHz, the use of ultra-small, low-cost capacitors and inductors is possible, providing a very compact and high-efficiency solution for DDR power applications.

Each channel of the LTC3634 uses internal RDS(ON) switches of only 65mΩ and 130mΩ to provide efficiency as high as 95%. The two channels are driven 180 degrees out of phase to minimize both input and output capacitance. An on-chip buffer capable of driving a 10mA load provides a low-noise reference output (VTTR) even at VDDQ/2. Additional features include a power good voltage monitor, input overvoltage and overtemperature protection, and short-circuit protection.

The LTC3634EUFD is available in a 4mm x 5mm QFN-28 package, and the LTC3634EFE is available in a 28-pin TSSOP package. Prices start at $4.25 and $4.40 per unit, respectively, based on a quantity of 1,000. The industrial-grade versions LTC3634IUFD and LTC3634IFE are guaranteed to operate over a temperature range of -40°C to 125°C, and are priced at $4.72 and $4.89 per unit, respectively, based on a 1,000-unit supply. All versions are currently available for purchase.
For more information, please refer to www.linear.com/product/LTC3634 .

Photo Caption: 15V, Dual 3A Monolithic Synchronous Step-Down Converter for DDR Memory Power

Product Features: LTC3634

• Input voltage range of 3.6V to 15V
• VDDQ, VTT, VTTR outputs
• Maximum ±3A output current
• Up to 95% efficiency
• Selectable 90°/180° phase shift between channels
• Adjustable switching frequency: 500kHz ~ 4MHz
• 10mA buffer VTTR = VDDQ/2 = VTT reference
• +1.6% accurate VTTR at 0.75V
• Optimal VOUT range: 0.6V ~ 3V
• Current mode operation for excellent line & load transient response
• External clock synchronization
• Circuit short-circuit protection
• Input overvoltage & overheating protection
• Power Good status output
• 4mm × 5mm QFN-28 and thermally enhanced 28-pin TSSOP package