LTC3649IFE#PBF part marking

Hello friends,

Can anyone help pls. What do the “IFE” symbols mean?
And why don’t they mark the “I” on the part?


I will submit an inquiry to verify


I have been told that the marking for LTC3649, LTC3649EFE#PBF, and the LTC3649IFE#PBF would be all the same marking “LTC3649” as shown on page 2 of the below-linked PDF.
LTC3649 (

Yes, and it’s interesting what does the “I” mean? and why don’t they mark it on the part?

The I vs. E calls out the temperature specifics of the part.

Note 5 from pdf page 4 of the datasheet:

The LTC3649E is guaranteed to meet specifications from 0°C to 85°C junction temperature. Specifications over the –40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls.
The LTC3649I is guaranteed over the full –40°C to 125°C operating junction temperature range. Note that the maximum ambient temperature consistent with these specifications is determined by specific operating conditions in conjunction with board layout, the rated package thermal impedance and other environmental factors.

Temperature grade is marked on the shipping container, not on the actual component itself.