原标题：Linear LTC3615双路3A同步稳压方案

　　Linear公司的LTC3615是双路3A同步降压稳压器,采用电流模式固定频率架构.输入电压2.25V-5.5V,输出电流2x3A,效率高达94%,输出电压低至0.6V,输出电压精度±1%,可调整开关频率高达4MHz,主要用作点负载电源,分布式电源,手提计算机电源,DDR存储器电源和手持设备.本文介绍了LTC3615主要特性, 方框图以及多种典型应用电路.

　　The LTC®3615 is a dual 3A synchronous step-down regula­tor using a current mode, constant-frequency architecture. The DC supply current is only 130μA (Burst Mode operation at no-load) while maintaining the output voltages, drop­ping to zero current in shutdown. The 2.25V to 5.5V input supply range makes the LTC3615 ideally suited for single Li-Ion applications. 100% duty cycle capability provides low dropout operation, which extends operating time in battery-operated systems.

　　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 and output voltage ripple in a single 6A output configuration. Programmable slew rate limiting reduces EMI, and external synchronization can be applied up to 4MHz.

　　The internal synchronous switches increase efficiency and eliminate the need for external catch diodes, saving external components and board space.

　　The LTC3615 is offered in leadless 24-pin 4mm × 4mm QFN and thermally enhanced 24-pin TSSOP packages.

　　LTC3615主要特性:

　　High Efficiency: Up to 94%

　　Dual Outputs with 2 × 3A Output Current Capability

　　Low Output Ripple Burst Mode® Operation: IQ = 130μA

　　2.25V to 5.5V Input Voltage Range

　　±1% Output Voltage Accuracy

　　Output Voltages Down to 0.6V

　　Programmable Slew Rate at Switch Pins

　　Low Dropout Operation: 100% Duty Cycle

　　Shutdown Current ≤1μA

　　Adjustable Switching Frequency Up to 4MHz

　　Internal or External Compensation

　　Selectable Pulse-Skipping/Forced Continuous/Burst Mode Operation with Adjustable Burst Clamp

　　Optional Active Voltage Positioning (AVP) with Internal Compensation

　　Selectable 0°/90°/180° Phase Shift Between Channels

　　Fixed Internal and Programmable External Soft-Start

　　Accurate Start-Up Tracking Capability

　　DDR Memory Mode IOUT = ±1.5A

　　Available in 4mm × 4mm QFN-24 and TSSOP-24 Packages

　　LTC3615应用:

　　Point-of-Load Supplies

　　Distributed Power Supplies

　　Portable Computer Systems

　　DDR Memory Termination

　　Handheld Devices

　　图1.LTC3615方框图

　　图2.LTC3615典型应用电路

　　图3.LTC3615应用电路:通路1软起动和补偿由外部编程, 通路软起动和补偿由内部编程

　　图4.LTC3615外部补偿应用电路

　　图5.LTC3615 DDR存储器应用电路

　　图6.LTC3615主从应用电路