The LTC3615IFE#PBF from Analog Devices is a dual-channel synchronous step-down (buck) regulator delivering 3 A per output from a 2.25 V to 5.5 V input rail. Each output is adjustable down to 0.6 V, and the switching frequency spans 400 kHz to 4 MHz — wide enough to let you pick between small inductors (high frequency) and better efficiency (lower frequency). The 24-TSSOP with exposed pad pulls heat into the PCB plane; for two 3 A rails in that footprint, the thermal design needs a decent copper pour underneath.
The 150°C TJ max also gives headroom in a hot enclosure — useful if the regulator sits near a processor or in a sealed motor-drive compartment.
Synchronous rectification and external compensation
The part does require external compensation (loop stability components); it is not a fixed-frequency, internally-compensated part. Plan for a few passives around the feedback and compensation pins.