PSR Flyback DC-DC with 65-V, 1.5-A Integrated Power MOSFET

The LM25180 from Texas Instruments is a primary-side regulated (PSR) flyback converter with high efficiency over an input voltage range of 4.5V to 42V. 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.

Typical applications are expected to include isolated field transmitters and field actuators, multi-output rails for analog input modules, motor drive IGBT gate drive supplies, and building automation HVAC systems.

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 65-V power MOSFET provides output power up to 7W with enhanced headroom for line transients.

The LM25180 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.

The LM25180 flyback converter is available in a 8-pin, 4-mm × 4-mm, thermally-enhanced WSON package with 0.8-mm pin pitch.

Summary of features:
  • Designed for reliable and rugged applications
    • Wide input voltage range of 4.5 V to 42 V
    • Robust solution with only one component crossing the isolation barrier
    • ±1.5% total output regulation accuracy
    • Optional VOUT temperature compensation
    • 6-ms 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 65-V, 0.4-Ω power MOSFET
    • No opto-coupler or transformer auxiliary winding required for VOUT regulation
    • Internal loop compensation
    • Low EMI operation to meet CISPR 32
  • High efficiency PSR flyback operation
    • Quasi-resonant switching in boundary conduction mode (BCM) at heavy load
    • Low input quiescent current
    • External bias option for improved efficiency
Texas Instruments Incorporated
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