Primary-side flyback controller — no internal switch
The BM1R00147F-E2: The BM1R00147F- is a flyback switching controller from ROHM Semiconductor designed for isolated offline or DC-DC power supplies. It is a controller IC, not a monolithic switcher — an external MOSFET handles the power stage, giving the designer flexibility to size the switch for the output power target. The controller operates from a 2.7V to 32V Vcc supply and requires a 28V start-up threshold to begin switching. This wide bias range lets it run from a loosely regulated auxiliary winding or a dedicated bias rail without an external linear regulator.
Fault protection set covers the common failure modes
Three protection circuits are integrated: current limiting prevents the external MOSFET from exceeding the peak current setpoint; over-temperature protection shuts down the controller if the die exceeds the safe junction limit; over-voltage protection guards against output overshoot during load transients or feedback-loop faults. The output is galvanically isolated, confirming this is a primary-side controller — the secondary-side regulation loop typically uses an optocoupler or a secondary-side controller to close the feedback path across the isolation barrier.
8-SOIC package and industrial temperature range
The standard SOIC-8 footprint is widely supported in PCB layout and assembly — no fine-pitch or special process requirements.
Available in Tape & Reel (TR) for automated pick-and-place or Cut Tape (CT) for prototyping and small-batch builds.