Linear LTC3855双路多相降压电源控制方案

Linear 公司的LTC3855是双路PolyPhase多相电流模式同步降压开关电源控制器,能驱动所有的N沟功率MOSFET.效率高达95%, RSENSE 或 DCR电流检测,输出电压精度±0.75% 0.6V,可锁相固定频率250kHz 到770kHz,可用于计算机系统,通信系统,工业和医疗设备,DC电源分布系统.本文介绍LTC3855主要特性,功能方框图, 高效双路1.2V/40A电源, 带NTC温度补偿DCR检测的2.5V/15A和1.8V/15A电源, 小型双相0.9V/50A电源等多种电源电路.

The LTC®3855 is a dual PolyPhase® current mode synchronous step-down switching regulator controller that drives all N-channel power MOSFET stages. It includes a high speed differential remote sense amplifier. The maximum current sense voltage is programmable for either 30mV, 50mV or 75mV, allowing the use of either the inductor DCR or a discrete sense resistor as the sensing element.

The LTC3855 features a precision 0.6V reference and can produce output voltages up to 12.5V. A wide 4.5V to 38V input supply range encompasses most intermediate bus voltages and battery chemistries. Power loss and supply noise are minimized by operating the two controller output stages out of phase. Burst Mode® operation, continuous or pulse-skipping modes are supported.

The LTC3855 can be configured for up to 12-phase operation, has DCR temperature compensation, two power good signals and two current limit set pins. The LTC3855 is available in low profile 40-pin 6mm × 6mm QFN and 38-lead exposed pad FE packages.

LTC3855主要特性:

Dual,180°Phased Controllers Reduce Required Input Capacitance and Power Supply Induced Noise

High Efficiency: Up to 95%

RSENSE or DCR Current Sensing

Programmable DCR Temperature Compensation

±0.75% 0.6V Output Voltage Accuracy

Phase-Lockable Fixed Frequency 250kHz to 770kHz

True Remote Sensing Differential Amplifier

Dual N-Channel MOSFET Synchronous Drive

Wide VIN Range: 4.5V to 38V

VOUT Range: 0.6V to 12.5V without Differential Amplifier

VOUT Range: 0.6V to 3.3V with Differential Amplifier

Clock Input and Output for Up to 12-Phase Operation

Adjustable Soft-Start or VOUT Tracking

Foldback Output Current Limiting

Output Overvoltage Protection

40-Pin (6mmx6mm) QFN and 38-Lead FE Packages

LTC3855应用:

Computer Systems

Telecom Systems

Industrial and Medical Instruments

DC Power Distribution System

图1.LTC3855功能方框图

图2.采用电阻来检测电流

图3.采用电感DCR来检测电流

图4.高效双路1.8V/1.2V降压转换器


图5.推荐PCB布局方框图

图6.高效双路 400kHz 1.8V/1.2V降压转换器

图7.带NTC温度补偿DCR检测的2.5V/15A和1.8V/15A电源( fSW = 350kHz)

图8. 1.8V/15A和1.2V/15A电源( fSW = 400kHz)

图9.高效双路1.2V/40A电源(fSW = 250kHz)

图10.带DCR检测的高效双相1.2V/40A电源(fSW = 250kHz)

图11.小型双相0.9V/50A电源(fSW = 400kHz)

图12.带辅助3.3V/5A轨的三相1V/50A电源(fSW = 400kHz)

图13.带检测电阻的3.3V/5A, 5V/5A转换器

图14.带DCR检测的12V/6A, 5V/10A电源(fSW = 250kHz)