基于LTC3614設計的4A 4MHz同步降壓電源技術

LTC3614是Linear公司的4A 4MHz同步降壓DC/DC轉換器,采用電流模式和固定頻率架構.無負載睡眠模式的電流為75uA,輸入電壓從2.25V到5.5V,100%占空比,工作頻率可編程到4MHz,允許使用小型SMT電感器.輸出電壓精度±1%,電壓可低至0.6V,效率高達95%,主要用在POL電源,分布電源,手提計算機電源,DDR存儲器電源和手持設備.本文介紹了LTC3614主要特性,方框圖以及多種應用電路.

DC-DC電源入門基礎下載：http://www.1cnz.cn/soft/70/2010/2010040872909.html

4A, 4MHz Monolithic Synchronous Step-Down DC/DC Converter

The LTC3614 is a low quiescent current monolithic synchronous buck regulator using a current mode, constant frequency architecture. The no-load DC supply current in sleep mode is only 75μA while maintaining the output voltage (Burst Mode operation) at no load, dropping to zero current in shutdown. The 2.25V to 5.5V input supply voltage range makes the LTC3614 ideally suited for single Li-Ion as well as fixed low voltage input applications. 100% duty cycle capability provides low dropout operation, extending the operating time in battery-powered systems.

The operating frequency is externally programmable up to 4MHz, allowing the use of small surface mount inductors. For switching-noise-sensitive applications, the LTC3614 can be synchronized to an external clock at up to 4MHz.

Forced continuous mode operation in the LTC3614 reduces noise and RF interference. Adjustable compensation allows the transient response to be optimized over a wide range of loads and output capacitors.

The internal synchronous switch increases efficiency and eliminates the need for an external catch diode, saving external components and board space. The LTC3614 is offered in a leadless 24-pin 3mm x ?5mm thermally enhanced QFN package.

LTC3614主要特性:

4A Output Current

2.25V to 5.5V Input Voltage Range

Low Output Ripple Burst Mode Operation: IQ = 75μA

±1% Output Voltage Accuracy

Output Voltage Down to 0.6V

High Efficiency: Up to 95%

Low Dropout Operation: 100% Duty Cycle

Programmable Slew Rate on SW Node Reduces Noise and EMI

Adjustable Switching Frequency: Up to 4MHz

Optional Active Voltage Positioning (AVP) with Internal Compensation

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

Programmable Soft-Start

Inputs for Start-Up Tracking or External Reference

DDR Memory Mode, IOUT = ±3A

Available in a 24-Pin 3mmx ?5mm QFN Thermally Enhanced Package

LTC3614應用:

Point-of-Load Supplies

Distributed Power Supplies

Portable Computer Systems

DDR Memory Termination

Handheld Devices

圖1.LTC3614方框圖

圖2.LTC3614 1.8V/4A降壓穩壓器電路圖

圖3.快速補償和改進瞬變響應2.25MHz通用降壓穩壓器電路圖

圖4.采用1MHz外接時鐘的主從跟蹤輸出電路圖