Linear LTC3775高效降压DC转换方案

Linear 公司的LTC3775是高效同步降压DC/DC控制器,输入电压从4.5V到38V,开关频率从250kHz 到1MHz,输出电压从0.6V 到 0.8VIN,主要应用在汽车电子系数,通信和工业设备电源以及点负载.本文介绍了LTC3775主要特性,方框图, 典型应用电路,包括5-26V输入,1.2V/12A输出; 8-36V输入,2.52V/10A输出和24V输入,12V/5A输出电路图.

The LTC3775 is a high efficiency synchronous step-down switching DC/DC controller that drives an all N-channel power MOSFET stage from a 4.5V to 38V input supply voltage. A patented line feedforward compensation circuit and a high bandwidth error amplifier provide very fast line and load transient response.

High step-down ratios are made possible by a low 30ns minimum on-time, allowing extremely low duty cycles MOSFET RDS(ON) current sensing maximizes efficiency.

Alternatively, a sense resistor can be used for higher current limit accuracy. Continuous monitoring of the voltages across the top and bottom MOSFETs allows cycle-by-cycle control of the inductor current, configurable by external resistors.

The soft-start function controls the duty cycle during start-up, providing a smooth output voltage ramp up. The operating frequency is user programmable from 250kHz to 1MHz and can be synchronized to an external clock.

LTC3775主要特性:

Wide VIN Range: 4.5V to 38V

Line Feedforward Compensation

Low Minimum On-Time: tON(MIN) < 30ns

Powerful Onboard MOSFET Drivers

Leading Edge Modulation Voltage Mode Control

±0.75%, 0.6V Reference Voltage Accuracy Over Temperature

VOUT Range: 0.6V to 0.8VIN

Programmable, Cycle-by-Cycle Peak Current Limit

Sense Resistor or RDS(ON) Current Sensing

Programmable Soft-Start

Synchronizable Fixed Frequency from 250kHz to 1MHz

Selectable Pulse-Skipping or Forced Continuous Modes of Operation

Low Shutdown Current: 14μA Typical

Thermally Enhanced 3mm x 3mm QFN Packag

LTC3775应用:

Automotive Systems

Telecom and Industrial Power Supplies

Point of Load Applications

图1.LTC3775典型应用电路

图2.LTC3775方框图

图3.LTC3775典型应用电路(5-26V输入,1.2V/12A输出,500kHz)


图4.LTC3775典型应用电路(8-36V输入,2.52V/10A输出,500kHz)


图5.LTC3775典型应用电路(24V输入,12V/5A输出,500kHz)