100V flyback regulator operates at 150°C junction temperature

March 07, 2017 // By Graham Prophet
Delivering up to 24W and producing up to a 1 kV output voltage, and operating in configurations that do not require opto-isolators, the H-grade versions of Linear Technology’s LT8304/-1 monolithic flyback regulators offer guaranteed operation for junction temperatures as high as 150°C.

By sampling the isolated output voltage directly from the primary-side flyback waveform, the part requires no opto-coupler or third winding for regulation. The LT8304 operates over a 3V to 100V input voltage range, has a 2A/150V integrated DMOS power switch and delivers up to 24W, making it well suited for a wide variety of automotive, industrial, medical and military applications. The new LT8304-1 version is tailored for high output voltages up to 1 kV.


These devices operate in boundary mode, which is a variable frequency current mode control switching scheme, typically resulting in better than ±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. Several off-the-shelf transformers, identified in the data sheet, can be used for numerous applications. 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 solution for isolated power delivery.


Additional features include output short-circuit protection, 116 µA no-load operating quiescent current, accurate enable and undervoltage lockout with hysteresis, internal soft-start and loop compensation, along with output diode temperature compensation. The part operates over a –40°C to 150°C junction temperature range and is available in a small thermally enhanced SO-8 package from $3.55 (1000).


Liner Technology; www.linear.com/product/LT8304