ADA4077-2 VOS differences between MSOP and SOIC Packages

Q 

Why a difference in VOS specs between the MSOP and SOIC?

 

A 

ADA4077-2 has a “B” grade (SOIC package only) and an “A “grade in SOIC and MSOP
package.  The difference between different grades is Vos parameter. Grade B has
a VOS specs of 35uV and
A grade has 50uV for SOIC and 90uv for MSOP package. Package stress testing, in
particular Solder Heat Resistance (SHR), during characterization and
qualification causes the tight electrical distribution of Vos to shift
slightly. This is one of the main reasons for spec differences between
packages. This shift in Vos is worse for smaller packages such as MSOP. SHR
testing is performed to different rating levels and ADI’s QA requirement is
MSL1. This stringent requirement is a big reason for spec differences.

The closest part in performance for Vos is OPA2277 which has a narrower temp
range of specification (-40C to +85C) and a more relaxed moisture sensitivity
level rating, MSL3. This level exposes the part to 30C/60% relative humidity
while the required ADI’s MSL1 subjects the ADA4077-2 to 85C/85% relative
humidity per IPC/JEDEC's J-STD-20. This stricter level of characterization
testing guarantees ADA4077-2’s datasheet specification when the parts are
soldered on a board in customer applications.