Laptop Motherboard — Layer 2.1 to 2.9: Topological Interconnect Map

12L PCB • 0.8mm • 3oz copper 85-100Ω diff

Hover components for names • Toggle layers left • Click layer to solo • Full Stack shows density of 12-layer PCB

2.1 POWER TREE

Water mains: 19V is high-pressure main, VRMs are pressure-reducing stations.

What it does

Distributes energy from adapter/battery. Charger creates 19V system rail, then bucks to 3.3V/5V always-on, then CPU VRM (0.7–1.3V @ 100A), GPU VRM, and PMIC rails for DDR and SoC. ~240 decoupling MLCCs keep ripple <15mV.

Key components

BQ25700 Charger, 6-phase RAA220 + 6x 220nH, 4-phase GPU, SY8288 3.3V/5V, 5x PMIC LDOs, 240× 10-22µF MLCC, sense Rs (1mΩ)

Failure modes

High-side FET short → 19V to CPU (dead). Open inductor → phase imbalance, thermal shutdown. Missing MLCC → Vdroop reboots. Corrosion on battery sense → false readings.

Design rule

Keep power loops < 3mm². Place caps within 2mm of load. 19V and GND pours on layers 2 & 11 form sandwich.

Layer density Single layer active