MacBook Power On Sequences & PPBUS_GH3 voltage

          MacBook Power On Sequences &                               PPBUS_GH3 voltage

This article is for MacBook logic board component-level repair professionals, written by IT-Tech Online, the MacBook repair specialist in Melbourne, Australia.

Next article:   MacBook SMC Circuits and PPBUS_G3H voltage adjustment.

We will discuss the early stage of MacBook power-on sequences here. It covers the creation of PP3V42_G3H  and PPBUS_G3H power rails and their normal voltages. At this level, in order to discuss in greater detail, we need to make use of Apple schematic diagrams, here we will be taking the 820-3437 MacBook Air 2013 A1466 Intel Haswell CPU logic board as an example.

1. PP3V42_G3H power rail creation.

The always-on 3.42V power rail PP3V42_G3H can be created directly from an internal battery or Magsafe charger shown as below:

File name : 2015-Macbook-Air-A1466-PP3V42-circuit.pdf