LT3573 simplifies design of flyback converters

Linear Technology has introduced the LT3573, an isolated monolithic flyback switching regulator with an integrated 1.25A NPN power switch.

The LT3573 simplifies the design of a flyback converter since it does not require a third winding or opto-isolator and can sense the output voltage directly from the primary side flyback waveform.

The LT3573 operates over an input voltage-range of 3 to 40V at output power levels up to 7W and can be used in a variety of industrial, medical, datacom and automotive applications requiring isolated power, including marine electronics, low power PoE and VoIP telephone interfaces.

The LT3573 operates in boundary mode, which is a variable-frequency current mode switching scheme, resulting in a total regulation band of +/- three per cent over a wide input-voltage range and output load-current in a typical application.

Boundary-mode operation also permits the use of a smaller transformer when compared with equivalent continuous conduction mode designs.

The output voltage is easily set by two external resistors.

The LT3573's additional features include an onboard LDO for third winding powering, programmable soft start, under-voltage lockout, adjustable current limit and output-voltage temperature compensation.

The LT3573 is available in a small thermally enhanced MSOP-16 package and is offered in an extended and industrial operating junction temperature range at -40 to 125C.

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