H-grade and military MP-grade versions of Linear Technology’s LTC3615 and LTC3615-1 4-MHz synchronous buck regulators operate in −40 to +150°C and −55 to +150°C temperature ranges, respectively. The LTC3615’s internal switches (RDS(ON) of 55 mΩ and 75 mΩ) produce up to 3 A of continuous output current from each channel, delivering efficiencies up to 94%. Output voltage ranges from 0.6 V to millivolts below VIN. Its 2.25- to 5.5-V input voltage suits it for single-cell Li-ion applications and 3.3- and 5-V intermediate bus systems. User-programmable switching frequency ranges from 400 kHz to 4 MHz. The LTC3615 offers selectable 0°/90°/180° phase shift; the LTC3615-1 offers 140°/180° phase shift between channels. Burst Mode operation reduces no-load quiescent current to 130 µA; an adjustable Burst Mode clamp lets designers optimize light load efficiency. The regulator can be configured to run in pulse-skipping or forced continuous modes to reduce noise to the lowest possible levels. Inputs are available for tracking capability as well as a DDR memory mode in which the device can source/sink ±1.5 A. Packaging options include a 4- by 4-mm QFn-24 and 24-lead, thermally enhanced TSSOP.