LinearLT3742稳压器控制方案

Linear公司的 LT3742是双输出100%占空比高电压输出降压DC/DC控制器，能驱动高边N沟功率MOSFET。输入电压可高达30伏，而关断电流仅为20μA，广泛应用在卫星和有线电视机顶盒，分布式电源稳压，汽车电子以及超大电容充电器。本文介绍了LT3742控制器的主要性能，方框图以及多种LT3742典型应用电路图。

LT3742: Dual Output 100% Duty Cycle High Output Voltage Step-Down or Current Source DC/DC Controller
The LT®3742 is a dual step-down DC/DC switching regulator controller that drives high side N-channel power MOSFETs. A 500kHz fixed frequency current mode architecture provides fast transient response with simple loop compensation components and cycle-by-cycle current limiting. The output stages of the two controllers operate 180° out of phase to reduce the input ripple current, minimizing the noise induced on the input supply, and allowing less input
capacitance.
An internal boost regulator generates a bias rail of VIN + 7V to provide gate drive for the N-channel MOSFETs allowing low dropout and 100% duty cycle operation. The LT3742 can be used for applications where both controllers need to operate independently, or where both controllers are used to provide a single higher current output.
主要特性：
■ Wide Input Voltage Range: 4V to 30V
■ Wide Output Voltage Range: 0.8V to VIN
■ Low Shutdown IQ: 20μA
■ Out-of-Phase Controllers Reduce Required Input
Capacitance and Power Supply Induced Noise
■ 0.8V ±1.5% Voltage Reference
■ 500kHz Current Mode Fixed Frequency Operation
■ Internal Boost Converter Provides Bias Rail for N-Channel MOSFET Gate Drive
■ Power Good Voltage Monitor for Each Output
■ Programmable Soft-Start
■ 24-Lead 4mm ??4mm ??0.75mm Package
主要应用：
■ Satellite and Cable TV Set-Top Boxes
■ Distributed Power Regulation
■ Automotive Systems
■ Super Capacitor Charger



图1。LT3742方框图



图2。LT3742典型应用电路图（1）



图4。LT3742典型应用电路图（2）



图4。LT3742典型应用电路图（3）



图5。LT3742典型应用电路图（4）



图6。LT3742典型应用电路图（5）