42 V synchronous buck controller in a 5.5x3.5 mm QFN
The LM25149RGYR: Switching frequency is programmable from 100 kHz to 2.2 MHz, with a clock-sync input for spreading the EMI spectrum or locking to a system clock. The 100% duty-cycle capability means the output can stay in regulation through input dips down to the output voltage plus headroom.
Junction temperature and control feature set
Rated for a junction temperature range of -40°C to 150°C, this controller can sit on a hot power-stage PCB in an engine bay or an industrial enclosure without derating. The 150°C TJ ceiling is the absolute limit — the actual operating ambient depends on the thermal impedance of the 24-VQFN (5.5x3.5 mm) pad to the board copper. Control features include current limit, enable, frequency control, power-good flag, programmable soft-start, and a ramp compensation pin. The power-good output is open-drain — it pulls low when the output is outside regulation, which simplifies sequencing with downstream POL converters.
Sourcing and lifecycle reality
Texas Instruments lists the LM25149RGYR as active product. The package is supplied in Tape & Reel or Cut Tape options — the 24-VFQFN with exposed pad requires a solder-paste stencil aperture that covers the centre thermal pad for proper solder-joint reliability under the 150°C junction limit.