Isolated Flyback Switching Regulators

The LT1425 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 15µA for standby operation.

Applications

* Isolated Flyback Switching Regulators

* Ethernet Isolated 5V to -9V Converter

* Medical Instruments

* Isolated Telecom Supplies

* No Transformer "Third Winding" or Optoisolator Required

* ±5% Accurate Output Voltage Without User Trims

* 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