Linear LT3972高效2.4A DC-DC转换方案

Linear公司的LT3972是高效2.4MHz 2.4A降压DC/DC转换器,输入电压高达33V(最大62V),输出电压从0.79V到30V.器件还集成了高效95mΩ的开关以及升压Schottky二极管和所需的振荡器,控制和逻辑电路.采用恒流拓扑具有块速瞬态特性和良好的回路稳定,广泛用于汽车电池调整,分布式电源,工业电源和墙壁变压器稳压.本文介绍了LT3972主要特性,方框图,以及典型应用电路,包括5V,3.3V, 2.5V, 12V,1.8V以及5V 2MHz降压转换器电路.

The LT3972 is an adjustable frequency (200kHz to 2.4MHz) monolithic buck switching regulator that accepts input voltages up to 33V (62V Maximum). A high efficiency 95mΩ switch is included on the die along with a boost Schottky diode and the necessary oscillator, control, and logic circuitry. Current mode topology is used for fast transient response and good loop stability. Low ripple Burst Mode operation maintains high efficiency at low output currents while keeping output ripple below 15mV in a typical application. In addition, the LT3972 can further enhance low output current efficiency by drawing bias current from the output when VOUT is above 3V.

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 91% of the programmed output voltage. The LT3972 is available in 10-Pin MSOP and 3mm x3mm DFN packages with exposed pads for low thermal resistance.

LT3972主要特性：

■ Wide Input Range:

Operation from 3.6V to 33V

Over-Voltage Lockout Protects Circuits Through 62V Transients

■ 3.5A Maximum Output Current

■ Low Ripple (<15mVP-P) Burst Mode Operation:IQ= 75μA at 12VIN to 3.3VOUT

■ Adjustable Switching Frequency: 200kHz to 2.4MHz

■ Low Shutdown Current: IQ < 1μA
■ Integrated Boost Diode

■ Synchronizable Between 250kHz to 2MHz

■ Power Good Flag

■ Saturating Switch Design: 95mΩ On-Resistance

■ Output Voltage: 0.79V to 30V

■ Thermal Protection

■ Soft-Start Capability

■ Small 10-Pin Thermally Enhanced MSOP and(3mmx3mm) DFN Packages

LT3972应用：

■ Automotive Battery Regulation

■ Distributed Supply Regulation

■ Industrial Supplies

■ Wall Transformer Regulation

图1.LT3972方框图


图2.LT3972 5V降压转换器电路

图3.LT3972 3.3V降压转换器电路

图4.LT3972 2.5V降压转换器电路

图5.LT3972 5V 2MHz降压转换器电路

图6.LT3972 12V降压转换器电路

图7.LT3972 1.8V降压转换器电路