Linear LT3757电流模式DC-DC转换方案

Linear公司的 LT3757是宽输入电压电流模式DC/DC转换控制器,能产生正或负向电压.LT3757的输入电压从表面上看2.9V到40V,用外接电阻可编程工作频率从100kHz到1Mz,能和外接时钟同步,输出电压保护,关断电流小于1uA ,内部有7.2V低压降稳压器,可编程输入欠压锁定和软起动,主要用于汽车电子和工业,通信电源和手提设备电源.本文介绍了LT3757主要特性,方框图以及典型应用电路,包括高效升压转换器, 3.3V输入,5V/10A输出升压转换器, 8-16V输入24V/2A输出升压转换器, 高压反激电源电路,以及5.5V-36V输入,12V/2A输出SEPIC转换器和非绝缘的反相SLIC电源.

The LT3757 is a wide input range, current mode, DC/DC controller which is capable of generating either positive or negative output voltages. It can be configured as either a boost, flyback, SEPIC or inverting converter. The LT3757 drives a low side external N-channel power MOSFET from an internal regulated 7.2V supply. The fi xed frequency,current-mode architecture results in stable operation over a wide range of supply and output voltages.

The operating frequency of LT3757 can be set with an external resistor over a 100kHz to 1MHz range, and can be synchronized to an external clock using the SYNC pin.

A low minimum operating supply voltage of 2.9V, and a low shutdown quiescent current of less than 1μA, make the LT3757 ideally suited for battery-operated systems.

The LT3757 features soft-start and frequency foldback functions to limit inductor current during start-up and output short-circuit.

The device is available in a small 10-lead DFN (3mmx 3mm) or MSOP package.

LT3757主要特性:

Wide Input Voltage Range: 2.9V to 40V

Positive or Negative Output Voltage Programming with a Single Feedback Pin

Current Mode Control Provides Excellent Transient Response

Programmable Operating Frequency (100kHz-1MHz) with One External Resistor

Synchronizable to an External Clock

Output Overvoltage Protection

Low Shutdown Current < 1μA

Internal 7.2V Low Dropout Voltage Regulator

Programmable Input Undervoltage Lockout with Hysteresis

Programmable Soft-Start

Small 10-Lead DFN (3mm x3mm) and Thermally Enhanced 10-Pin MSOP Packages

LT3757应用:

Automotive and Industrial Boost, Flyback, SEPIC and Inverting Converters

Telecom Power Supplies

Portable Electronic Equipment

图1.用作SEPIC转换器的LT3757方框图

图2.LT3757高效升压转换器

图3. 3.3V输入,5V/10A输出升压转换器

图4.8-16V输入24V/2A输出升压转换器

图5.高压反激电源电路

图6.5.5V-36V输入,12V/2A输出SEPIC转换器

图7.5-12V输入,+/-12V 0.2A输出SEPIC转换器


图8.非绝缘反相SLIC电源