Non-isolated buck PWM controller with integrated 730V MOSFET
The ROHM BM2PDA1Y-Z is a non-isolated PWM DC/DC converter IC designed for buck (step-down) topologies. It integrates a 730V breakdown MOSFET and a PWM controller in a single 7-lead DIPK through-hole package, simplifying the primary-side power stage for offline converters. Switching at 65 kHz, the part includes a full suite of fault protections: current limiting, over-load, over-voltage, and over-temperature shutdown. A soft-start feature reduces inrush stress on the output capacitor and load during power-up. The supply range (Vcc/Vdd) spans 11.1V to 26V, with a startup threshold of 9.3V. This allows direct biasing from a rectified auxiliary winding or a low-voltage rail. The duty cycle is limited to 40%, typical for a buck converter operating in continuous conduction mode.
Industrial temperature grade and protection suite
The integrated over-temperature protection shuts down the converter if the die exceeds the safe junction limit, providing a fail-safe in high-ambient or stalled-fan scenarios. The 730V breakdown MOSFET handles rectified mains with margin for line transients. The 65 kHz switching frequency is a common choice that balances transformer/inductor size against EMI filter cost.