Linear公司的LTC3639是一款具有内部高边侧控制及同步功率开的高效降压DC-DC稳压器，在没有负载的情况下仅有12uA典型功率损耗。LTC3639能够支持100mA的负载电流，可编程的峰值电流限制提供优化效率、减少纹波和器件尺寸的特性。LTC3639具有宽的输入电压范围：4V-150V，使其可以工作在输入电压比较恶劣的方面。本文首先介绍芯片的简介、特性、内部框图及应用领域，并给出相应设计方案的设计原理图、元器件列表及PCB元件布局图。

The LTC3639 is a high efficiency step-down DC/DC regulator with internal high side and synchronous power switches that draws only 12μA typical DC supply current while maintaining a regulated output voltage at no load.

The LTC3639 can supply up to 100mA load current and features a programmable peak current limit that provides a simple method for optimizing efficiency and for reducing output ripple and component size. The LTC3639’s combination of Burst Mode operation, integrated power switches, low quiescent current, and programmable peak current limit provides high efficiency over a broad range of load currents.

With its wide input range of 4V to 150V and programmable overvoltage lockout, the LTC3639 is a robust regulator suited for regulating from a wide variety of power sources. Additionally, the LTC3639 includes a precise run threshold and soft-start feature to guarantee that the power system start-up is well-controlled in any environment. A feedback comparator output enables multiple LTC3639s to be connected in parallel for higher current applications.

The LTC3639 is available in a thermally enhanced high voltage-capable 16-lead MSE package with four missing pins.

LTC3639主要特性：

■ Wide Operating Input Voltage Range: 4V to 150V
■ Synchronous Operation for Highest Efficiency
■ Internal High Side and Low Side Power MOSFETs
■ No Compensation Required
■Adjustable 10mA to 100mA Maximum Output Current
■Low Dropout Operation: 100% Duty Cycle
■Low Quiescent Current: 12μA
■Wide Output Range: 0.8V to VIN
■0.8V ±1% Feedback Voltage Reference
■Precise RUN Pin Threshold
■Internal or External Soft-Start
■Programmable 1.8V, 3.3V, 5V or Adjustable Output
■Few External Components Required
■Programmable Input Overvoltage Lockout
■Thermally Enhanced High Voltage MSOP Package

LTC3639应用：

■Industrial Control Supplies
■Medical Devices
■Distributed Power Systems
■Portable Instruments
■Battery-Operated Devices
■Automotive
■Avionics

 
图1. LTC3639内部方框图

LTC3639方案介绍：

Demonstration circuit 1901A is a 150V input, 100mA output DC/DC power supply featuring the LTC3639. The IC operates in a high efficiency Burst Mode® operation and includes internal high and low side power MOSFETs. The board will accept an input voltage between 4V and 150V, and provide jumper selected output voltages of 1.8V, 3.3V, 5V and an option for additional voltages. The IC includes internal soft-start and a provision for increasing soft-start time.

Included on the board is an ON/OFF jumper that can also be configured as a precision undervoltage lockout. Additional PC pads are included for programming current limit to optimize efficiency and for reducing output voltage ripple and reducing component size. A terminal (FBO) is included to allow multiple boards to be paralleled for higher output current.

Output voltage between 800mV and VIN can be programmed using optional resistors. (Higher voltage rating output capacitors may be required.)

LTC3639方案原理图：



图2. LTC3639方案原理图

LTC3639方案材料清单：



PCB元件布局图：