PCB Design Requirements
Thought for 2 mins 18 sec
I inspected the live DRC airwire report and mapped the flagged IDs back to the layout components.
Airwire findings
Table
- The airwire checker reported pads tied to IDs
39ce6c47and21b6c03f. - In the PCB layout, those IDs map to:
- The schematic confirms the only pads on those components are:
Flux’s DRC output is exposing the flagged pad/component IDs, but not the full airwire pair geometry in the review text itself. So I can identify the three unresolved pads confidently, but the review output does not explicitly name the opposite endpoint of each unrouted connection.
So the practical read is:
List all airwires
Show first airwire
Check missing footprints
Thought
nets {
net GND = GND:GND, J4:1, J1:1, J3:1, D1:A, C1:2, C2:P2;
net VIN = C2:P1, J2:1, C1:1, D1:K;
}
Refine this doc
Ask about this doc
Automotive inline protection design choices
- Replacing the previous 555 demo content with an inline automotive protection PCB.
- Selected topology: VIN+ enters the board, immediately encounters a TVS shunt path to ground and local input capacitors, then passes through a series inductor to VOUT+.
- The protection/filter node is intentionally on the input side so surge current is clamped before it reaches the downstream controller.
- Layout priority is minimizing the VIN+-TVS-GND loop and keeping the capacitor return path into the ground plane short and low inductance.
- A 2-layer board is appropriate because this is a simple low-speed power filter/protection design. Bottom copper will be used as a solid ground plane; top copper will carry the heavy current path.
- The board outline will be kept short and inline, but widened enough to fit a high-current inductor and electrolytic capacitor while preserving wide copper.
- For current handling, wide copper pours and large wire-entry plated holes will be used rather than small connectors.
- Preferred component set:
- SMBJ24A-class unidirectional TVS in SMBJ package
- 470uF to 1000uF, 35V or higher electrolytic bulk capacitor
- 100nF, 50V ceramic capacitor
- Low-DCR power inductor/choke rated for at least 10A continuous
- If an explicitly automotive-qualified AEC-Q101 TVS is not available in-library, use the closest in-stock SMBJ24A-class part and preserve the package/footprint and electrical class for later substitution.
Direct-solder wire pad redesign for J1 and J2
- J1 and J2 are repurposed from terminal blocks into direct-solder wire attachment points for 16 AWG harness leads.
- Mechanical target for the wire pads: plated through-hole approximately 1.8 mm finished hole with approximately 4.2 mm copper pad diameter to accept stripped 16 AWG conductors and create stronger annular support.
- Solder mask expansion target at the wire pads: approximately 0.2 mm to encourage full solder wetting and visible fillet inspection.
- Strain relief intent: use the plated termination holes as the electrical anchor and document the need for nearby lashing, adhesive, or enclosure-supported harness retention because only limited footprint-level mechanical modification is available in-project.
- Electrical topology remains unchanged: J1 VIN+ feeds the protected VIN node, J1 GND feeds the ground return, L1 remains in series from VIN to VOUT, and J2 carries VOUT and GND to the harness exit.
- Layout rule target for the main current path is 2.54 mm (100 mil) preferred width on the top layer, with the bottom layer maintained as a solid ground reference where practical.
- The wire-interface redesign prioritizes robustness and manufacturability over minimizing every millimeter of area.
Automotive inline protection design choices
Direct-solder wire pad redesign for J1 and J2
