The Pi 4 is power-hungry compared to its predecessors. The schematic reveals the complexity required to turn a 5V input into the various voltages needed by the BCM2711 processor.
Look for the PMD (Power Management Integrated Circuit). You will see a complex network of switching regulators that step down voltage for the CPU core, the SDRAM, and the IO ports. Understanding this section is crucial if you are trying to power the Pi via the GPIO header rather than the USB-C port, as it helps you understand the current requirements and protection circuits (like the infamous "USB-C issue" present in early revisions). Raspberry Pi 4 Model B Full Schematic
The most distinct change in the Pi 4 schematic compared to its predecessors is the complete overhaul of the power delivery network. The Pi 4 is power-hungry compared to its predecessors
This is the most complex section. The Pi 4 requires multiple voltage rails: 3.3V, 1.8V, 1.1V (Core), 0.8V (DDR4), and 5V (USB/VGA). You will see a complex network of switching
Key Components on these pages:
The Pi 4 uses LPDDR4 SDRAM, which is significantly faster than the SDRAM on the Pi 3. On the schematic, you can see the address and data buses connecting the processor to the RAM chip.
What makes this interesting is the sheer density of connections. High-speed memory routing requires precise impedance matching and length tuning—something you can't see on the schematic, but the number of lines gives you an appreciation for the engineering required to prevent signal integrity issues.