Introduction

　　The LT?3750 is a current mode fl yback controller optimized to easily and effi ciently provide a controlled current to charge just about any capacitive energy storage device. The LT3750’s simple but fl exible feature set allows it to handle a wide variety of charging needs. These include large high voltage capacitors for professional photofl ash equipment and emergency beacons， small capacitors that are charged and discharged thousands of times a second， and batteries for long term energy needs.

　　Safe， Small and Flexible

　　All of the control and feedback functions of the LT3750 are referred to the charger’s input. The target voltage is set by just two resistors in a simple， low voltage network that monitors the fl yback voltage of the transformer. When charging a capacitor to a high voltage， there is no need to connect any components to the hazardously high output potential. The charging current is a triangle wave whose amplitude is set by an external sense resistor and the fl yback transformer turns ratio.

　　The LT3750 operates in boundary mode， at the edge of continuous and discontinuous conduction， which signifi cantly reduces switching losses. This in turn allows for high frequency operation， and a correspondingly small fl yback transformer size. The LT3750 is itself tiny， available in a 10-lead MSOP package.

　　The LT3750 is also compatible with a wide range of control circuitry. It is equipped with a simple interface consisting of a CHARGE command input bit and an open-drain DONE status fl ag. Both of these signals are compatible with most digital systems， yet tolerate voltages as high as 24V. The LT3750 operates from 3V to 24V DC.