原标题：Linear LT3958输出可正可负DC-DC电源转换方案

　　Linear 公司的LT3958是宽输入电压(5V-80)，电流模式，输出可正可负DC-DC电源转换器，可配置成升压，反激，SEPIC或反相转换器。LT3958集成了84V/3.3A N沟功率MOSFET和7.2V LDO稳压器，可编开关频率100kHz到1MHz，能和外部时钟同步，主要用在汽车，通信和工业领域。本文介绍了LT3958主要特性，方框图，以及多种应用电路图。

　　The LT3958 is a wide input range, current mode, DC/DC converter which is capable of generating either positive or negative output voltages. It can be configured as either a boost, flyback, SEPIC or inverting converter. It features an internal low side N-channel power MOSFET rated for 84V at 3.3A and driven from an internal regulated 7.2V supply. The fixed frequency, current-mode architecture results in stable operation over a wide range of supply and output voltages.

　　The operating frequency of LT3958 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 minimum operating supply voltage of 5V, and a low shutdown quiescent current of less than 1μA, make the LT3958 ideally suited for battery-powered systems. The LT3958 features soft-start and frequency foldback functions to limit inductor current during start-up.

　　LT3958主要特性:

　　Wide Input Voltage Range: 5V to 80V

　　Single Feedback Pin for Positive or Negative Output Voltage

　　Internal 3.3A/84V Power Switch

　　Current Mode Control Provides Excellent Transient Response

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

　　Synchronizeable to an External Clock

　　Low Shutdown Current < 1μA

　　Internal 7.2V Low Dropout Voltage Regulator

　　Programmable Input Undervoltage Lockout with Hysteresis

　　Programmable Soft-Start

　　Thermally Enhanced QFN (5mm 6mm) Package

　　LT3958应用:

　　Automotive

　　Telecom

　　Industrial

　　图1。LT3958用作SEPIC转换器的方框图

　　图2。LT3958高效率转换器电路图

　　图3。LT3958用作48V输出升压转换器电路图

　　图4。LT3958用作高压反激电源

　　图5。LT3958用作12V输出SEPIC转换器电路图

　　图6。LT3958用作-12V输出反相转换器电路图