High-voltage isolated monolithic flyback regulator eliminates optocoupler

February 24, 2011 // By Paul Buckley
Linear Technology Corporation has introduced a high voltage isolated monolithic flyback regulator that simplifies the design of an isolated DC/DC converter. No optocoupler, third winding or signal transformer is required for feedback since the output voltage is sensed from the primary-side flyback signal.

The LT3512 operates over a 4.5 V to 100 V input voltage range, has a 420 mA, 150 V power switch and delivers up to 4.5 watts of output power, making it well suited for a wide variety of telecom, datacom, automotive, industrial and medical applications.

The LT3512 operates in a boundary mode, a current-mode control switching scheme, resulting in better than ±5% regulation over the full line, load and temperature range. Boundary mode, also known as critical conduction mode, permits the use of a smaller transformer compared to equivalent continuous conduction mode designs. The output voltage is easily set by two external resistors and the transformer turns ratio. Several transformers identified in the data sheet can be used for a variety of applications. The high level of integration results in a simple, clean, tightly regulated application solution to the traditional challenge of isolated power delivery.

Availability and Pricing

The LT3512 is available in a small MSOP-16 package with 4 pins removed for additional high voltage pin spacing. In addition to the extended and industrial versions that operate over a junction temperature range from -40°C to 125°C, a high temperature automotive grade is available that operates from -40°C to 150°C.  Pricing starts at $3.15 each in 1000-piece quantities.

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