Flyback regulator simplifies isolated DC-DC converter designs

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By Nick Flaherty

By sampling the isolated output voltage directly from the primary-side flyback waveform, the LT8303 requires no opto-isolator, LT1431 or third winding for regulation. The device operates over a 5.5V to 100V input voltage range, has a 0.45A/150V integrated DMOS power switch and delivers up to 5 watts of output power, making it well suited for a wide range of telecom, datacom, automotive, industrial, medical and military applications.

The output voltage is set with only one external resistor and the transformer turns ratio. Several off-the-shelf transformers, identified in the data sheet, can be used for numerous applications. The LT8303 operates in boundary mode, which is a variable frequency current mode control switching scheme, typically resulting in ±5% output voltage regulation over the full line, load and temperature range. Boundary mode enables the use of a smaller transformer compared to equivalent continuous conduction mode designs. The high level of integration and the use of low ripple Burst Mode operation result in a simple to use, low component count and high efficiency application solution for isolated power delivery.

Additional features include output short-circuit protection, 70µA no load operating quiescent current, internal loop compensation, accurate enable and undervoltage lockout with hysteresis.

Extended and industrial versions operate over a junction temperature range of –40°C to 125°C and pricing starts at $3.15 each in 1000-piece quantities.

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