100Vin, 5W out regulator uses primary-side control

September 19, 2016 // By Graham Prophet
LT8303 is a monolithic flyback regulator in a TSOT-23 package that simplifies the design of isolated DC/DC converters. By sampling the isolated output voltage directly from the primary-side flyback waveform, the part requires no opto-isolator, LT1431 or third winding for regulation.

The LT8303 operates over a 5.5V to 100V input voltage range, has a 0.45A/150V integrated DMOS power switch and delivers up to 5W, suiting it for a range of telecom, datacom, automotive, industrial, medical and military applications. The output voltage is set with one external resistor and the transformer turns ratio. Several off-the-shelf transformers are identified in the data sheet. 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, 70 µA 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. Pricing starts at $3.15 (1000).

 

Linear Technology; www.linear.com/product/LT8303