Designing for ESD Protection: Essential Best Practices

Imagine you’re an architect tasked with designing a skyscraper. Every aspect, from the materials used to the structural framework, needs to be meticulously planned to withstand environmental stresses, ensuring the building stands tall and secure for decades. Designing electronic systems, particularly those involving sensitive components like touchscreens, involves a similar level of precision and foresight. One of the most pervasive threats to the longevity and reliability of electronic devices is electrostatic discharge (ESD). Just as an architect must consider wind and seismic forces, an engineer must account for ESD in their design to prevent catastrophic failures.   With experience covering over 25 years in the industry providing interactive smart displays, Amulet Technologies has a lot to share when it comes to the best practices for ESD protection, to ensure your designs remain robust and reliable.

Understanding ESD: The Invisible Threat

Electrostatic discharge is the sudden flow of electricity between two electrically charged objects, often caused by contact or a high-voltage differential. This phenomenon is common in our daily lives—we experience it as the slight shock when touching a doorknob after walking on a carpet. While these minor shocks are harmless to us, they can be devastating to electronic components. ESD can cause immediate damage or latent defects, leading to reduced reliability and eventual failure of electronic devices​​.

The Importance of Grounding 

One of the foundational strategies in ESD protection is proper grounding. Ensuring that all electronics and anything coming into contact with them are at the same electrical potential is crucial. This means grounding workstations, tools, and personnel. Wearing ESD wrist straps connected to a good earth ground, using ESD smocks, and ensuring work surfaces and flooring are properly grounded are all essential steps​​. Think of it as building a lightning rod system for your devices, directing any potential static discharge safely into the ground.

Circuit Design for ESD Protection

Designing circuits to withstand ESD events involves several key practices. One effective method is the use of decoupling capacitors. These components help filter out high-frequency noise and stabilize voltage levels, protecting sensitive parts of your circuit. Placing decoupling capacitors as close as possible to the supply voltage and ground pins minimizes the risk of noise and voltage spikes that could lead to ESD damage.  For example, decoupling capacitors are used across Amulet’s family of resistive displays, protecting the resistive touch controls lines from transmitting potentially damaging ESD introduced by a human touch.

Another critical element is the use of transient voltage suppressors (TVS) and zener diodes. These components act as protectors, clamping excessive voltage and preventing it from reaching sensitive areas of the circuit. For example, protecting the touch panel controller in a display system with TVS arrays can prevent visual anomalies caused by ESD. It’s like installing shock absorbers in a car, ensuring that sudden impacts don’t damage the vehicle’s delicate systems.

PCB Design: Creating Safe Pathways

The design of the printed circuit board (PCB) itself plays a pivotal role in ESD protection. One of the best practices is to create a low impedance path to ground, allowing any electrostatic discharge to flow directly to earth ground. Separating earth ground from digital signal ground is crucial to prevent ESD from finding alternate paths through sensitive circuitry.  In all the PCB designs for Amulet’s products, a separate ground plane is used that is not connected to signal ground.  The ground plane is connected to the chassis ground or earth ground when assembled into the final product.

Additionally, using thick ground traces and strategically placing TVS devices close to potential ESD entry points can significantly reduce parasitic inductance and improve ESD resilience. Imagine laying down well-marked, broad paths in a park to ensure visitors don’t trample the flower beds—proper PCB layout guides ESD away from sensitive areas, preserving the integrity of your design.

System-Level Design: Holistic Protection

Beyond individual components and circuit design, system-level considerations are essential for comprehensive ESD protection. Ensuring that the housing of the display module or other electronic devices provides a solid connection to earth ground is one such measure. This involves designing the enclosure to act as a shield, dissipating any electrostatic charge safely into the ground. Attaching wires from mounting screws to the chassis ground of the enclosure ensures that the entire system works together to mitigate ESD risk

Real-World Application: Implementing ESD Best Practices

Let’s delve into how these best practices come together in a real-world scenario. Imagine you’re designing a high-end industrial touchscreen interface. This device will be used in various environments, from cleanrooms to manufacturing floors, each with its own ESD challenges. Here’s how you might implement ESD protection based on the principles we’ve discussed:

Circuit Design: Integrate decoupling capacitors close to the power and ground pins of the touch controller. Use TVS diodes to protect the touch panel’s X+ and Y+ coordinates, ensuring they clamp any excessive voltages.

PCB Layout: Design the PCB with thick ground traces and separate digital signal grounds from earth grounds. Place TVS devices near connectors and potential ESD entry points.

System Enclosure: Design the device housing to include a solid earth ground connection, using mounting screws to tie the enclosure to the chassis ground. This creates a protective barrier that directs ESD away from sensitive internal components.

Conclusion: Building Resilient Designs

Incorporating these best practices for ESD protection is akin to constructing a fortress around your electronic systems. By grounding your devices, designing resilient circuits, optimizing PCB layouts, and considering system-level protection, you can significantly mitigate the risks posed by electrostatic discharge. These strategies not only enhance the durability and reliability of your designs but also ensure that your products perform flawlessly in diverse environments.

Amulet takes all the fore mentioned best practices and incorporates them into the design of all their products.  From the board level product like the GCC-2 to the high performance 7 inch capacitive smart module, high reliability and longevity remains a high priority.

As engineers, our goal is to create devices that stand the test of time, much like the architect who designs buildings to withstand the elements. By embracing these ESD protection best practices, you can build the foundation for robust, reliable, and long-lasting electronic systems. Remember, every detail matters, and taking the time to implement these measures will pay off in the longevity and performance of your products. Let’s continue to innovate with resilience at the forefront, ensuring our designs are ready to face the invisible threats of the modern world.

Author Bio: 

Johnny Gohata, Amulet’s marketing director and overall information guru.  With more than 35 years in the high-tech arena that is Silicon Valley, he started his career as an ASIC FAE, branching into sales and marketing for various start-ups, which ultimately landed him at Amulet Technologies. With a pioneering role in developing applications for smart displays, Johnny has mastered the art of converting complex problems into elegant and simple solutions.  In his free time, he likes to drive his Tesla, learn about artificial intelligence, and dabble in Python programming.