The DC2665A (circa 2018) was replaced by the DC2665B (circa 2022) as the reference design/eval board for the LTM4626, LTM4638, and LTM4657 buck converters.
These two designs (DC2665A, DC2665B) are largely identical, except:
- The DC2665B also supports the LTM4657 (-C variant),
- There is additional output-side capacitance,
- There is additional input-side capacitance (particularly C29, the "fast" .022uF 0603), and
- The layout has changed significantly.
Item (1) is sensible and item (2) is explained by the revision history section in the DC2665B manual ("DC2665B-B replaces DC2665A-B for low HF VOUT ripple.")
I'm curious specifically about the input-side capacitance (3) and associated layout changes (4). Why was the EVB redesigned, and why was C29 added? I understand why fast capacitance is necessary at the input side and should have been present on the DC2665A, but I'm wondering if you can describe the actual impact its absence had on the DC2665A and whether this is the reason for the re-design.
