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| Question | Answer |
|---|---|
| In 4 layers, which is the best suggested stackup? | For a 4-layer PCB, the most commonly recommended stack-up is: Signal Layer – Ground Plane – Power Plane – Signal Layer. |
| Regarding guard traces, if they’re connected to ground, why not just extend the ground plane where the trace guards would be? Or is this in cases where dimensional constraints are limiting the surface area of the ground plane? | Yes, that is correct. If there is enough board space, extending the ground plane is generally the better approach because it provides a more continuous return path and improved shielding. However, in areas with routing congestion or dimensional constraints, implementing grounded guard traces can be a practical alternative. Guard traces help reduce crosstalk and EMI when extending the ground plane is not feasible. |
| What is your opinion on separating analog ground plane & digital ground plane? | Separating analog and digital ground planes depends heavily on the circuit architecture, component placement, and signal routing requirements. In general, we try to keep analog and digital sections separated to minimize noise coupling. We also avoid overlapping analog and digital ground regions on adjacent layers whenever possible. Digital signals should reference the digital ground plane, while analog signals should reference the analog ground plane to maintain clean return current paths. Typically, the analog and digital grounds are connected at a single point, usually near the source or converter interface, to prevent unwanted ground loops and reduce noise interference between the two domains. |
| Does Sierra circuits have any resources for getting UL or other certifications after pcb manufacture? | If any type of certification, such as UL certification, is required, the PCB project must be planned and set up from the beginning to meet those certification requirements. Certification is not typically applied after the boards have already been manufactured. If the customer requires UL certification for their product, it is best to contact UL directly so the project scope can be properly defined and assigned to the appropriate certification team. Sierra Circuits can support manufacturing requirements related to certified builds when those requirements are specified during the initial project setup. |
| I have to design an analog sensor circuit to operate very close to an arc welder. Can I shield analog signal lines by surrounding the signal line with grounds? | The solution depends on the level of noise generated by the arc welder, including voltage surges, conducted noise, and EMI radiation. Surrounding sensitive analog signal lines with grounded shielding can help reduce noise coupling, but additional protection methods are usually required in such harsh environments. Sensitive analog circuitry should be carefully protected using suitable surge protection devices, proper grounding techniques, and effective EMI shielding methods. Good PCB design practices are also critical, including: Using a well-designed stack-up with solid ground planes Routing sensitive traces as short as possible Sandwiching signal traces between ground planes when feasible Keeping sensitive traces away from board edges Minimizing the number of vias in critical signal paths Separating noisy and sensitive circuits appropriately The overall effectiveness will depend on the specific welding environment, operating frequencies, and proximity of the analog circuitry to the arc welder. |