Linear公司的LTC3639是一款具有內部高邊側控制及同步功率開的高效降壓DC-DC穩壓器，在沒有負載的情況下僅有12uA典型功率損耗。LTC3639能夠支持100mA的負載電流，可編程的峰值電流限制提供優化效率、減少紋波和器件尺寸的特性。LTC3639具有寬的輸入電壓范圍：4V-150V，使其可以工作在輸入電壓比較惡劣的方面。本文首先介紹芯片的簡介、特性、內部框圖及應用領域，并給出相應設計方案的設計原理圖、元器件列表及PCB元件布局圖。
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應用：
■Industrial Control Supplies
■Medical Devices
■Distributed Power Systems
■Portable Instruments
■Battery-Operated Devices
■Automotive
■Avionics
圖1. LTC3639內部方框圖
LTC3639方案介紹：
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方案原理圖：
圖2. LTC3639方案原理圖
LTC3639方案材料清單：
PCB元件布局圖：
