LT1425

Features:

No Transformer "Third Winding" or Optoisolator Required
±5% Accurate Output Voltage Without User Trims (See Circuit Below)
Resistor Programmable Output Voltage
Regulation Maintained Well Into Discontinuous Mode (Light Load)
Optional Load Compensation
Operating Frequency: 285kHz
Easily Synchronized to External Clock
Available in 16-Pin Narrow SO Package


Application

Isolated Flyback Switching Regulators
Ethernet Isolated 5V to 9V Converters
Medical Instruments
Isolated Telecom Supplies


Pinout




Specifications

Supply Voltage ......................................................... 20V
Switch Voltage ......................................................... 35V
SHDN, SYNC Pin Voltage............................................ 7V
RFB Pin Current......................................................... 2mA
Operating Junction Temperature Range
    Commercial .......................................................... 0°C to 100°C
    Industrial ............................................................. 40°C to 100°C
Storage Temperature Range ................................... 65°C to 150°C
Lead Temperature (Soldering, 10 sec)..................... 300°C


Description

The LT^®1425 is a monolithic high power switching regulator specifically designed for the isolated flyback topology. No "third winding" or optoisolator is required; the integrated circuit senses the isolated output voltage directly from the primary side flyback waveform. A high current, high efficiency switch is included on the die along with all oscillator, control and protection circuitry.

The LT1425 operates with input supply voltages from 3V to 20V and draws only 7mA quiescent current. It can deliver output power up to 6W with no external power devices. By utilizing current mode switching techniques, it provides excellent AC and DC line regulation.

The LT1425 has a number of features not found on other switching regulator ICs. Its unique control circuitry can maintain regulation well into discontinuous mode in most applications. Optional load compensation circuitry allows for improved load regulation. An externally activated shutdown mode reduces total supply current to 15A for standby operation.