Dual 4MHz, ±3A Synchronous Buck Converter for DDR Termination

The LTC3618 is a dual synchronous step-down regulator using a current mode, constant-frequency architecture. It provides a complete DDR solution with an input voltage range from 2.25V to 5.5V.

The output of the first step-down regulator offers a high accuracy VDDQ supply. A buffered reference generates VTTR at 50% of VDDQIN and drives loads up to ±10mA. The second regulator generates the DDR termination voltage (VTT) equal to VTTR. Both regulators are capable of delivering ±3A of load current at 1MHz switching frequency.

The operating frequency is externally programmable up to 4MHz, allowing the use of small surface mount inductors. 0°, 90°, or 180° of phase shift between the two channels can be selected to minimize input current ripple. For switching noise-sensitive applications, the LTC3618 can be synchronized to an external clock up to 4MHz.

The LTC3618 is offered in leadless 24-pin 4mm × 4mm QFN and thermally enhanced 24-pin TSSOP packages.

APPLICATIONS

* DDR Memory

* Supports DDR, DDR2, and DDR3 Standards

* Tracking Supplies

* DDR Power Supply, Termination and Reference

* High Efficiency: Up to 94%

* Dual Outputs with ±3A Output Current Capability

* 2.25V to 5.5V Input Voltage Range

* ±1% Output Voltage Accuracy

* VTT Output Voltage Down to 0.5V

* Shutdown Current ≤1μA

* VTTR = VDDQIN/2, VFB2 = VTTR

* Adjustable Switching Frequency Up to 4MHz