New Industry Products

65Vin PSR Flyback DC-DC Converter IC with 100V / 0.75A Integrated MOSFET

April 22, 2020 by Paul Shepard

The LM5181 from Texas Instruments (TI) is a primary-side regulated (PSR) flyback dc-dc converter IC with high efficiency over a wide input voltage range of 4.5V to 65V. The isolated output voltage is sampled from the primary-side flyback voltage, eliminating the need for an optocoupler, voltage reference, or third winding from the transformer for output voltage regulation.

TI also offers the LM5181-Q1 dc-dc converter IC, AEC-Q100-qualified for automotive applications with an automotive qualified device temperature grade 1: -40°C to 125°C ambient temperature range

The high level of integration results in a simple, reliable and high-density design with only one component crossing the isolation barrier. Boundary conduction mode (BCM) switching enables a compact magnetic solution and better than ±1.5% load and line regulation performance. An integrated 100-V power MOSFET provides output power up to 4 W with enhanced headroom for line transients.

The LM5181 flyback dc-dc converter is available in an 8-pin, 4mm × 4mm, thermally-enhanced WSON package with 0.8-mm pin pitch.

The LM5181 dc-dc converter simplifies implementation of isolated dc-dc supplies with optional features to optimize performance for the target end equipment. The output voltage is set by one resistor, while an optional resistor improves output voltage accuracy by negating the thermal coefficient of the flyback diode voltage drop.

Additional features include an internally-fixed or externally-programmable soft start, optional bias supply connection for higher efficiency, precision enable input with hysteresis for adjustable line UVLO, hiccup-mode overload protection, and thermal shutdown protection with automatic recovery.


  • Designed for reliable and rugged applications
    • Wide input voltage range of 4.5V to 65V with operation down to 3.5V after start-up
    • Robust solution with only one component crossing the isolation barrier
    • ±1.5% total output regulation accuracy
    • Optional VOUT temperature compensation
    • 6ms internal or programmable soft start
    • Input UVLO and thermal shutdown protection
    • Hiccup-mode overcurrent fault protection
    • -40°C to +150°C junction temperature range
  • Integration reduces solution size and cost
    • Integrated 100V, 0.4Ω power MOSFET
    • No opto-coupler or transformer auxiliary winding required for VOUT regulation
    • Internal loop compensation
  • High-efficiency PSR flyback operation
    • Quasi-resonant MOSFET turn-off in BCM
    • Low input quiescent current
    • External bias option for improved efficiency
    • Single- and multi-output implementations
  • Ultra-low conducted and radiated EMI signatures
    • Soft switching avoids diode reverse recovery
    • Optimized for CISPR 32 EMI requirements