LT3470AED / U7090 / U6990 Buck Regulator Controller IC
This is the PP3V42_G3H regulator IC for many model Macbooks. It turns either 18v, 16v, 12v, or 8v into 3.42v. It commonly dies on Macbook Airs and the 820-2879 macbook Pro because it is on the edge, where water most commonly seeps in.
U6990 on older Macbook Airs & Retinas
U7090 on 2013-2016 Macbook Airs & Retinas
QFN - 8 Pin