LT1725 General Purpose Isolated Flyback Controller

The LT®1725 is a monolithic switching regulator controller specifically designed for the isolated flyback topology. It drives the gate of an external MOSFET and is generally powered from a third transformer winding. These features allow for an application input voltage limited only by external power path components. The third transformer winding also provides output voltage feedback information, such that an optoisolator is not required. Its gate drive capability coupled with a suitable external MOSFET can deliver load power up to tens of watts.

The LT1725 has a number of features not found on most other switching regulator ICs. By utilizing current mode switching techniques, it provides excellent AC and DC line regulation. Its unique control circuitry can maintain regulation well into discontinuous mode in most applications. Optional load compensation circuitry allows for improved load regulation. An optional undervoltage lockout pin halts operation when the application input voltage is too low. An optional external capacitor implements a soft-start function. A 3V output is available at up to several mA for powering primary side application circuitry

产品特点 Features

Drives External Power MOSFET with External ISENSE Resistor
Application Input Voltage Limited Only by External Power Components
Senses Output Voltage Directly from Primary Side Winding—No Optoisolator Required
Accurate Regulation Without User Trims
Regulation Maintained Well into Discontinuous Mode
Switching Frequency from 50kHz to 250kHz with External Capacitor
Available in 16-Pin SO and SSOP Packages
Optional Load Compensation
Optional Undervoltage Lockout

参数

应用

Telecom Isolated Converters
Offline Isolated Power Supplies
Instrumentation Power Supplies

典型应用图

LT1725 订购信息和价格参考Package Variations and Pricing

器件型号	封装	引脚	温度	价格 (以 1 ~ 99 片为批量)	价格 (以 1000 片为批量) *
LT1725CGN	SSOP	16	C	$3.55	$3.00
LT1725CGN#PBF	SSOP	16	C	$3.55	$3.00
LT1725CGN#TR	SSOP	16	C		$3.06
LT1725CGN#TRPBF	SSOP	16	C		$3.06
LT1725CS	SO	16	C	$3.43	$2.90
LT1725CS#PBF	SO	16	C	$3.43	$2.90
LT1725CS#TR	SO	16	C		$2.96
LT1725CS#TRPBF	SO	16	C		$2.96
LT1725IGN	SSOP	6	I	$4.14	$3.50
LT1725IGN#PBF	SSOP	6	I	$4.14	$3.50
LT1725IGN#TR	SSOP	16	I		$3.56
LT1725IGN#TRPBF	SSOP	16	I		$3.56
LT1725IS	SO	16	I	$4.03	$3.40
LT1725IS#PBF	SO	16	I	$4.03	$3.40
LT1725IS#TR	SO	16	I		$3.46
LT1725IS#TRPBF	SO	16	I		$3.46

LT1725 数据手册及相关资料下载

数据手册(英文) : LT1725 - General Purpose Isolated Flyback Controller.PDF
设计要点 (英文) : DN260 - Isolated Flyback Converter Regulates Without an Optocoupler.PDF
设计要点 (英文) : DN338 - Power over Ethernet Isolated Power Supply Delivers 11.5W at 90% Efficiency.PDF
可靠性数据 : R387 Reliability Data .PDF