Linear公司的 LTC3608是高效单片同步降压DC/DC转换器,它采用恒流单次计时器模式架构,输入电压从4V到18V,输出电流高达8A..内部采用同步功率开关,从而增加了效率,也不需要外接肖特基二极管. LTC3608广泛应用在点负载(POL)稳压和电源配电系统.本文介绍了LTC3608的主要特性,方框图以及典型的应用电路与LTC3608 布局图.本文还介绍了几种设计案例,提供了详细的电路图和元件数值.

The LTC 3608 is a high effi ciency, monolithic synchronous step-down DC/DC converter that can deliver up to 8A output current from a 4V to 18V (20V maximum) input supply. It uses a valley current control architecture to deliver very low duty cycle operation at high frequency with excellent transient response. The operating frequency is selected by an external resistor and is compensated for variations in VIN and VOUT.

The LTC3608 can be confi gured for discontinuous or forced continuous operation at light load. Forced continuous operation reduces noise and RF interference while discontinuous mode provides high effi ciency by reducing switching losses at light loads.

Fault protection is provided by internal foldback current limiting, an output overvoltage comparator and an optional short-circuit shutdown timer. Soft-start capability for supply

sequencing is accomplished using an external timing capacitor. The regulator current limit is user programmable.

A power good output voltage monitor indicates when the output is in regulation. The LTC3608 is available in a compact 7mm X8mm QFN package.

主要特性:

8A Output Current

Wide VIN Range = 4V to 18V

Internal N-Channel MOSFETs

True Current Mode Control

Optimized for High Step-Down Ratios

tON(MIN) ≤ 100nsec

Extremely Fast Transient Response

Stable with Ceramic COUT

±1% 0.6V Voltage Reference

Power Good Output Voltage Monitor

Adjustable On-Time/Switching Frequency

Adjustable Current Limit

Programmable Soft-Start

Output Overvoltage Protection

Optional Short-Circuit Shutdown Timer

Low Shutdown IQ: 15μA

Available in a 7mm 8mm 52-Lead QFN Package

应用:

Point of Load Regulation

Distributed Power Systems

图1. LTC3608方框图

图2. LTC3608典型应用电路图

图3. LTC3608次级输出回路和EXTVCC连接图

图4.LTC3608设计案例: 5V-18V 输入,输出2.5V/8A ,550kHz

图5.LTC3608 布局图

图6.LTC3608设计案例: 3.6V 输入,输出215V/8A ,750kHz

图7.LTC3608设计案例: 5V-18V 输入,输出1.2V/8A ,550kHz

图8.LTC3608设计案例: 5V-18V 输入,输出1.8V/8A ,全陶瓷电容,1MHz

图9.LTC3608设计案例: 14V-18V 输入,输出12V/5A ,500kHz

详情请见:

http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1042,C1032,C1064,P85693,D26585