LTM4657Recommended for New Designs
The LTM4657 is a complete 8A step-down switching mode µModule (micromodule) regulator in a tiny 6.25mm × 6.25mm × 3.87mm BGA package. Included in the package...
Datasheet LTM4657 on Analog.com
OK, I found the answer on the Datasheet. The LTC3644 Datasheet has the same information: : "The LTC3644/LTC3644-2 is tested under pulsed load conditions such that TJ ≈ TA. The LTC3644E is guaranteed to meet specified performance from 0°C to 85°C. Specifications over the –40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LTC3644I is guaranteed over the –40°C to 125°C operating junction temperature range."
