3 A point-of-load buck in a 3x3 mm QFN
The ST1S31PUR is a synchronous step-down regulator from STMicroelectronics that delivers 3 A continuous output from a 2.8 V to 5.5 V input rail — the sweet spot for 3.3 V and 5 V intermediate buses in space-constrained designs. Switching at 1.5 MHz lets the designer use a small inductor and ceramic output capacitors, keeping the total solution footprint tight around the 8-QFN (3x3 mm) package. The adjustable output voltage range from 0.8 V up to the input rail covers the common core and I/O voltages for FPGAs, SoCs, and MCUs.
Junction temperature range and synchronous rectification
Rated for a junction temperature range of -40°C to 150°C, this regulator is qualified for automotive under-hood and industrial environments where ambient temperatures push beyond 85°C — the 150°C TJ ceiling gives margin for self-heating at full load. The integrated synchronous rectifier eliminates the external Schottky catch diode, reducing BOM count and board area while improving efficiency at lower output voltages. The exposed pad on the 8-VDFN package (supplier device package 8-QFN 3x3 mm) must be soldered to a thermal land on the PCB with adequate vias to the ground plane — the datasheet layout recommendation on page 7 shows the via pattern and copper area needed to keep the junction below 150°C at 3 A.
Active production and sourcing posture
STMicroelectronics lists the part as ROHS3 compliant, meeting the current EU RoHS exemption rules.