Linear LT3682低功耗降压稳压电源方案

Linear 公司的LT3682是可调开关频率(250kHz到2.2MHz)的低功耗降压稳压电源器,输入电压可高达36V.器件集成了高效0.5欧姆的开关,升压二极管和必须的振荡器,控制和逻辑电路.采用电流模式以得到快速的瞬态响应和良好的回路稳定性. LT3682的工作电压从3.6V到36V,瞬态电压可达60V,输出波纹小于15mVp-p,广泛用于汽车电子电池调整和娱乐系统,工业电源和手提产品电源.本文介绍了LT3682的主要特性,方框图以及输出电压分别为
5V,3.3V和1.8V的转换器电路图.

The LT3682 is an adjustable frequency (250kHz to 2.2MHz) monolithic buck switching regulator that accepts input voltages up to 36V. A high efficiency 0.5Ω switch is included on the device along with a boost diode and the necessary oscillator, control, and logic circuitry. Current mode topology is used for fast transient response and good loop stability. A SYNC pin allows the user to synchronize the part to an external clock, and to choose between Low Ripple Burst Mode operation and standard PWM operation.

The Low Ripple Burst Mode maintains high efficiency at low output currents while keeping output ripple below 15mV in typical applications. Shutdown reduces input supply current to less than 1μA while a resistor and capacitor on the RUN/SS pin provide a controlled output voltage ramp (soft-start). A power good flag signals when VOUT reaches 90% of the programmed output voltage.

Protection circuitry senses the current in the power switch and external Schottky catch diode to protect the LT3682 against short-circuit conditions. Frequency foldback and
thermal shutdown provide additional protection.
The LT3682 is available in a 12-Pin 3mmx3mm DFN with exposed pad for low thermal resistance.

LT3682主要特性:
Wide Input Range:
Operation from 3.6V to 36V
Overvoltage Lockout Protects Circuits through
60V Transients
1A Output Current
n Low Ripple Burst Mode  Operation
IQ = 75μA at 12VIN to 3.3VOUT
Output Ripple < 15mVP-P
Adjustable Switching Frequency: 250kHz to 2.2MHz
Short-Circuit Protected
Synchronizable Between 300kHz and 2.2MHz
0.8V Feedback Reference Voltage
Output Voltage 0.8V to 20V
Soft-Start Capability
Power Good Flag
Small 12-Pin Thermally Enhanced 3mm x&#61472;3mm DFN Package

应用:
Automotive Battery Regulation
Automotive Entertainment Systems
Industrial Supplies
Power for Portable Products
Distributed Supply Regulation




图1. LT3682方框图
TYPICAL APPLICATION



图2.输出5V降压转换器电路图



图3.输出3.3V降压转换器电路图



图4.输出1.8V降压转换器电路图