Linear Announces The LTC3634 Synchronous Buck Regulator Used in DDR Memory Power Supply

The LTC3634 is ideal for cell Li-Ion applications as well as 5V and 12V intermediate bus systems because of its 3.6V to 15V working input voltages.

The LTC3634 incorporates a unique constant frequency/controlled on-time, current mode architecture, which is ideal for powering DDR applications from a 12V input supply at high switching frequencies. Its termination voltage, VTT, is set to ½ of VDDQ down to 0.6V with accuracy of ±1.6%. The combination of a monolithic design and switching frequencies as high as 4MHz, which enable the use of tiny, low cost capacitors and inductors, provides a very compact, high efficiency solution for DDR power applications.

Each channel of the LTC3634 uses internal switches with RDS(ON) of only 65mOhms and 130mOhms to deliver efficiencies as high as 95%. The two channels run 180 degrees out of phase, minimizing the size of both input and output capacitance. An on-chip buffer capable of driving a 10mA load provides a low noise reference output (VTTR) also at VDDQ/2. Additional features include power good voltage monitors, input overvoltage and over temperature protection, and short circuit protection. 

The LTC3634EUFD uses a 4mm x 5mm QFN-28, while LTC3634EFE is available in a 28-lead TSSOP package. Prices of both prices are at $4.25 and $4.40 each in 1,000-piece quantities. Industrial grade versions, the LTC3634IUFD and LTC3634IFE, are guaranteed to operate over the -40°C to 125°C operating junction temperature range and are priced at $4.72 and $4.89 each, respectively, in 1,000-piece quantities.

Its features:

1. 3.6V to 15V Input Voltage Range

2. VDDQ, VTT, VTTR Outputs

3. Up to ±3A Output Current

4. Up to 95% Efficiency

5. Selectable 90°/180° Phase Shift Between Channels

6. Adjustable Switching Frequency:500kHz to 4MHz

7. 10mA BufferedVTTR = VDDQ/2 = VTT Reference

8. ± 1.6% Accurate VTTR at 0.75V 

9.Optimal VOUT Range: 0.6V to 3V

10. Current Mode Operation for Excellent Line & Load Transient Response

11. External Clock Synchronization

12. Short-Circuit Protected

13. Input Overvoltage & Overtemperature Protection

14. Power Good Status Outputs

15. Available in (4mm x 5mm) QFN-28 & Thermally Enhanced 28-Lead TSSOP Packages

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