Adjustable Frequency Current Mode Flyback DC/DC Controller

The LTC3805 is a current mode controller for flyback DC/DC converters designed to drive an N-channel MOSFET in high input and output voltage converter applications. Operating frequency and slope compensation can be programmed by external resistors. Programmable overcurrent sensing protects the converter from short-circuits. Soft-start can be programmed using an external capacitor and the soft-start capacitor also programs an automatic restart feature.

The LTC3805 provides ±1.5% output voltage accuracy and consumes only 360μA of quiescent current during normal operation and only 40μA during micropower startup. Using a 9.5V internal shunt regulator, the LTC3805 can be powered from a high VIN through a resistor or it can be powered directly from a low impedance DC voltage of 9V or less.

The LTC3805 is available in the 10-lead MSOP package and the 3mm × 3mm DFN package.

Turn On Voltage

LTC3805

8.4V

LTC3805-5

4.5V

Applications

* Telecom Power Supplies

* 42V and 12V Automotive Power Supplies

* Isolated Electronic Equipment

* VIN and VOUT Limited Only by External Components

* Adjustable Slope Compensation

* Adjustable Overcurrent Protection with Automatic Restart

* Adjustable Operating Frequency (70kHz to 700kHz) with One External Resistor

* Synchronizable to an External Clock

* ±1.5% Reference Accuracy