Linear Technology introduces the LT3825, a synchronous flyback DC/DC controller for 10W to 60W or up to 12A output isolated power supplies. The вумшсу is a current mode controller that regulates the output voltage based on sensing secondary voltage via a transformer winding. This allows for tight output regulation without the use of an optoisolator, improving dynamic response and system reliability. For example, the LT3825 is used to convert an input supply of 36V-72V to an isolated output of 3.3V at 12A with up to 90% efficiency and mere 0.009% regulation. Applications include isolated power supplies in telecom, medical, industrial and instrumentation systems.

The LT3825 has a unique feedback amplifier that eliminates the need for an optoisolator by sampling a transformer winding voltage during flyback period and using this voltage to precisely regulate the output voltage. A programmable primary gate delay function eliminates multiple discrete components from the circuit and optimizes MOSFET switching time and transformer selection. To further simplify the design, the chip allows its switching frequency to be adjusted from 50kHz to 250kHz with a capacitor. The IC can also be synchronized to an external oscillator. The LT3825 is rated for operation from -40°C to 125°C and is offered in a thermally enhanced 16-lead TSSOP. 1,000-piece price is set at $3.10 each.