Date: 05/08/2010

Isolated monolithic flyback switching regulator to simplify DC/DC converter design

Linear Technology has released the LT3575, an isolated monolithic flyback switching regulator. The main problem faced by such devices generally is to communicate information related to output voltage on the isolated secondary side of the transformer to the primary. Traditionally opto-isolators or extra transformer windings are used for this purpose. This switching regulator eliminates the use of opto-isolator, third winding or signal transformer required for feedback in the LT3575. The output voltage is sensed from the primary-side flyback pulse waveforms.

The LT3575 operates over an input voltage range of 3V to 40V and delivers up to 14 Watts of output power. A 2.5A, 60V NPN power switch is integrated along with all control logic. It is therefore suitable for wide variety of industrial, medical, telecom, datacom and automotive applications.

The LT3575 operates in boundary mode, which is a variable frequency current-mode control switching scheme, typically resulting in +/-5% regulation over the full line, load and temperature range. In the boundary mode control method the part operates in the boundary between continuous conduction mode and discontinuous conduction mode. The output voltage is set by two external resistors and the transformer turns ratio.

Additional features include an onboard low dropout regulator for IC power, programmable soft-start, undervoltage lockout, adjustable current limit and output voltage temperature compensation.

Package: small thermally enhanced TSSOP-16

Operating temperature range: -40°C to 125°C.

Prices: Starts at each US$3.50 for 1000-piece quantities.