Features

• 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
• V_TT Output Voltage Down to 0.5V
• Shutdown Current ≤1μA
• VTTR = VDDQIN/2, V_FB2 = VTTR
• Adjustable Switching Frequency Up to 4MHz
• Internal or External Compensation
• Selectable 0°/90°/180° Phase Shift Between Channels
• Internal or External Soft-Start for V_DDQ, Internal Soft-Start for V_TT
• Power Good Status Outputs
• Low Profile 4mm × 4mm QFN-24 and TSSOP-24 Packages

Typical Application

Description

The LTC®3618 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 V_DDQ supply. A buffered reference generates VTTR at 50% of VDDQIN and drives loads up to ±10mA. The second regulator generates the DDR termination voltage (V_TT) 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.