I am designing a custom PCB to replace the internal lithium-ion battery of a Google Pixel 3a (G020E/G020G). The goal is to convert the phone into a permanent "desktop PC" that runs indefinitely on wall power without the risk of battery swelling or thermal shutdown.

Technical Specifications

• Input: $5\text{V}$ DC via USB-C (Power Only).

• Regulation: Stepping down $5\text{V}$ to a stable $4.2\text{V}$ (simulating a fully charged Li-ion cell).

• Target IC: TPS62130 (or similar $3\text{A}$ Buck Converter) to handle high-current CPU spikes during Android boot.

• BSI/ID Logic: Integrating a $10\text{k}\Omega$ pull-down resistor on the Battery Status Indicator (BSI) pin to bypass the phone's "Battery Not Found" and temperature sensors.

• Connector: 3-Pin FPC Battery Connector (Pixel 3 series compatible).

Seeking Help With:

1. Schematic Review: Ensuring the buck converter circuit has enough output capacitance ($100\mu\text{F}+$) to prevent reboots during peak power draw.

2. Trace Width: Advice on copper weight ($1\text{oz}$ vs $2\text{oz}$) and trace width for the $4.2\text{V}$ rail to minimize voltage drop.

3. Heat Dissipation: Best practices for thermal vias to keep the buck converter cool inside the phone chassis.