Hi, what's the difference between the EY and the IY versions of the LTM4657?
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."