In today’s fast-paced world of technology, making sure printed circuit boards (PCBs) work efficiently is more important than ever. Among the many components in a PCB, the guard ring is often overlooked, but it serves a crucial purpose in safeguarding the circuit from unwanted electromagnetic interference.
A PCB guard ring is a copper wire used to protect the circuit from losing voltage or current to other nearby conductors. Its job is to encircle the circuit and prevent voltage or current leaks, especially in AC circuits. This simple wire connects to a low-impedance voltage source to keep the circuit closed. When the current in the guard ring equals the circuit’s current, it prevents any leaks and ensures everything runs smoothly.
Despite its simplicity, PCB guard rings play a critical role in keeping the circuit stable and intact. They help maintain efficiency by preventing signal loss and interference.
Role in PCB Design
As PCBs become more complex, various signals, including AC, travel along the board’s surface traces and vias. Precise readings are essential in some applications to avoid misdiagnosis. Although low-voltage components typically don’t need shielding, even tiny leaks in current can disrupt readings and affect the output.
Guard Ring vs. Guard Trace
When working on PCB design, you have various ways to shield sensitive traces and nodes from interference and stray currents. One of these methods is the guard trace, which is different from the guard ring. While the guard ring encircles a node, the guard trace is a copper conductor positioned parallel between two copper traces.
The guard trace is used to protect a sensitive trace from any potential interference caused by a high-speed signal. In contrast, the guard ring is used to safeguard a node from stray currents. It’s important to understand the distinction between these two methods so you can select the most suitable one for your particular PCB design requirements.
Designing Effective PCB Guard Rings
To design effective PCB guard rings, you should consider a few factors. First, encircle the high-impedance input node(s) with the guard ring. Connect the ring to the right nodes based on potential polarity. Minimizing the thermocouple effect (a high current source) and avoiding other metal types crossing the ring are essential.
EMI (Electromagnetic Interference) from nearby traces and conductive elements can affect the guard ring’s performance. Maintaining adequate clearance and creepage, and following guidelines, are crucial to ensure the guard ring works optimally and provides the necessary protection.
PCB Guard Ring and EMI
EMI can disrupt circuits, causing malfunction or inaccurate results. To combat this, consider all components and their interference levels, which can range from 50 kHz to 50 MHz. Guard traces are an effective method to reduce EMI by shielding sensitive traces from high-speed signals that cause interference. Eliminating crosstalk can significantly improve circuit performance.
A PCB guard ring is crucial for maintaining a low-voltage circuit’s optimal function by preventing current leaks. Its placement on the PCB matters, so working with a capable PCB manufacturer ensures the circuit design’s success. Paying attention to every detail is the key to achieving your desired results.
source: https://www.myemssolutions.com/pcb-guard-ring-everything-you-need-to-know/
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