Linear LTC3803-5反激开关电源控制方案

Linear公司的LTC3803-5是恒频电流模式反激开关电源控制器,输入电压可低至5V,输出电压精度±1.5%,静态电流仅为240uA,工作温度从-40度C到150度C,可用于12V和42V汽车电源,通信电源,以太网供电(PoE)和家用电源.本文介绍了LTC3803-5的主要特性,方框图以及典型应用电路,包括宽输入双输出转换器电路图, 2W通信用电源转换器和4:1输入3.3V输出隔离反激DC/DC转换器电路图.

The LTC3803-5 is a constant frequency current mode flyback controller optimized for driving 4.5V and 6V rated N-channel MOSFETs in high input voltage applications. The
LTC3803-5 operates from inputs as low as 5V. Constant frequency operation is maintained down to very light loads, resulting in less low frequency noise generation over a wide range of load currents. Slope compensation can be programmed with an external resistor.

The LTC3803-5 provides ±1.5% output voltage accuracy and consumes only 240μA of quiescent current. Groundreferenced current sensing allows LTC3803-5-based converters to accept input supplies beyond the LTC3803-5’s absolute maximum VCC. For simplicity, the LTC3803-5 can be powered from a high VIN through a resistor, due to its internal 8V shunt regulator. An internal undervoltage lockout shuts down the IC when the input voltage falls below 3.2V, guaranteeing at least 3.2V of gate drive to the external MOSFET.

The LTC3803-5 is available in a low profi le (1mm) 6-lead SOT-23 (ThinSOT) package.

LTC3803-5主要特性:

VIN and VOUT Limited Only by External Components

4.8V Undervoltage Lockout Threshold

Operating Junction Temperature from –40℃ to 150℃

Adjustable Slope Compensation

Internal Soft-Start

Constant Frequency 200kHz Operation

±1.5% Reference Accuracy

Current Mode Operation for Excellent Line and Load Transient Response

No Minimum Load Requirement

Low Quiescent Current: 240μA

Low Profi le (1mm) SOT-23 Package

LTC3803-5应用:

42V and 12V Automotive Power Supplies

Telecom Power Supplies

Auxiliary/Housekeeping Power Supplies

Power Over Ethernet



图1.LTC3803-5方框图



图2.LTC3803-5典型应用电路



图3. 采用LTC3803-5的宽输入双输出转换器电路图



图4.采用LTC3803-5的2W通信用电源转换器



图4.4:1输入3.3V输出隔离反激DC/DC转换器