Designing Your PCB for Transient Voltage Suppression
PCBs in aircraft, near high voltage equipment, and with a weak grounding strategy are at serious risk of damage due to electrostatic discharge (ESD). When ESD occurs, a huge spike of current propagates through your board, causing damage to components and thermally sensitive components. There are a number of ways to protect your board from ESD. In addition to implementing the right grounding strategy, choosing the right components for suppressing ESD in your board will protect sensitive components from high currents. Altium Designer includes the tools you need to implement the right grounding strategy and includes the components you need to protect your board from ESD.
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If you use power strips for your home electronics, then you’re already aware of the surge protection they provide. In the event of a lightning strike, a short in your home electrical wiring, or after a major power outage, a surge protector will act as a voltage suppressor and dampen the voltage and current spike induced in your electronics protecting them from damage. Some surge protectors include a circuit breaker that will trip in the event of a power surge, completely blocking any harmful current spikes from damaging your electronics.
Not all PCBs will be part of a system that can be protected with a surge protector. While consumer electronics can connect to a surge protector on a 110 V or 220 V AC line, industrial electronics may connect to a variety of different power sources. These boards can also be subjected to discharge from a variety of sources beyond a surge in the power source. Boards near other high voltage systems with weak grounding can receive ESD that induces a large transient voltage in the circuitry and components. This causes serious damage to your components and ruins your board.
In aerospace, transient voltage suppression is required according to FAA standards, and power acceptability in avionics systems should be designed according to the CBEMA curve. Huge voltage and current spikes in aircraft can arise during lightning strikes, and critical electrical systems in airplanes must be designed to withstand these events.
There are several transient voltage suppression methods you can implement in your boards, involving either including specific components for protection or implementing the right grounding strategy. No matter which method you choose, you’ll need to work with design software that makes it easy to implement these protections at the PCB level. This goes beyond simply planning to use a surge protector or a circuit breaker to protect electronic equipment.
Perhaps the simplest method for a transient voltage suppressor and preventing damage to your sensitive circuits is to cut power from the circuit in the event of a spike. This is as simple as placing a circuit breaker on the line for your board. Once the current exceeds a certain threshold, the breaker will trip and power will be cut from the circuit.
While this is fine for preventing damage to your circuits due to power surges that cannot be suppressed with a surge protector, it does nothing to prevent ESD that travels directly to your board from an external source. You can place fuses and small circuit breakers directly on larger boards to protect sensitive circuits, but these elements are simply too large to include in smaller, modern boards that interface with high-performance components. Going further requires working with components specifically designed for transient voltage suppression.
Components for Transient Voltage Suppression
Components that provide a transient voltage suppressor can take on many forms. Arc contacts, filters, and solid-state semiconductor devices are all used for current spike protection in sensitive circuits. One popular semiconductor device for current suppression is the metal-oxide varistor. These devices are rated for a variety of transient voltage values and are easily included in a circuit as a through-hole component.
Another popular component for transient voltage suppression in sensitive circuits is a TVS diode. These diodes provide overvoltage protection by shunting excess current once the magnitude of a voltage or current spike exceeds the avalanche breakdown threshold of the diode. These components can respond much faster to overvoltage than varistor or older devices like gas discharge tubes.
Any surge protection device used for transient voltage suppression can be used in series with the load to attenuate the current that passes into nearby components. They can also be used in parallel with the load to divert the transient to a ground connection.
- ESD can arise from a number of external sources and is particularly important in telecom, power distribution, and avionics systems. Learn more about ESD and how you can add protection to your PCB.
- One useful component for suppressing ESD in your PCB is to place a TVS diode in your critical circuits. Learn more about choosing and placing TVS diodes in your PCB.
- Termination methods for traces and for impedance matching networks are useful outside of antenna design. Learn more about designing a grounding strategy to withstand ESD.
Searching and comparing components in your library with Altium Designer
Even if you use surge protection devices to bypass current spikes from sensitive circuits or suppress transient voltage using a filter, you can provide your circuit with excellent ESD protection when you use the right grounding strategy. Placing a connection back to chassis ground will send any dissipated currents back to earth or back to a bulky conductor, ensuring that any current spike in your system will not damage sensitive components.
Surge Protection with Components and Grounding
Using components by themselves is not a cure-all for ESD problems, and the same applies to proper grounding. Rather than only relying on components or grounding, you should opt to use both strategies to protect your circuits from current spikes due to ESD. Placing the components you need and defining a current sink back to earth takes the right PCB design software with an extensive components library and circuit modeling capabilities.
- Transient analysis is an excellent tool for determining the effectiveness of a filtration strategy for surge protection, or for assessing the effectiveness of a TVS diode in your PCB. Learn more about transient analysis in your PCB design software.
- Once you’ve designed your grounding strategy and completed your layout, you can verify its effectiveness and check for ground loops, potential thermal problems, and islands or peninsulas using a PDN analyzer.
- PDN analyzers can be complicated beasts, but they reveal a significant amount of information about your power distribution network in a single simulation output.
Example output from the PDN Analyzer in Altium Designer
Working with a complete PCB design software package will allow you to include surge protection or clamping voltage strategies in your circuit board within a single interface. You shouldn’t need to move between different schematic design, layout, and power analysis tools to design your board. Instead, all your critical tools should be placed in a single interface, giving you the power to implement the best circuit protection strategy for your PCB within a single program.
Altium Designer: The Best Design Tools in a Single Package
When your design, layout, and analysis tools are present in a single interface, you can identify design problems that may create vulnerability to ESD and correct them within a single program. No other PCB design software program offers the productivity and adaptability of Altium Designer.
- The rules-driven design engine in Altium Designer helps you spot design errors and ensures that all of your design features work together. Learn more about rules-driven design in Altium Designer.
- Unified design means that all your important design tools are placed in a single program that operates with a consistent workflow. Only Altium Designer creates this environment and places your schematic design, layout, component management, and analysis tools in a single program. Learn more about unified design and the integrated features in Altium Designer.
- Using components like TVS diodes for transient voltage suppression requires keeping an extensive components library and managing your supply chain. See how Altium Designer can help you manage your supply chain and your BOM.
With Altium Designer, your components libraries and layout tools are accessible within a single program. You won’t have to switch between programs to implement a grounding strategy or special components to suppress ESD in your PCB. Whether you work in aerospace, power generation, and distribution, or any other industry, Altium Designer has the tools you need to design for ESD protection and transient voltage suppression.
Working in a unified design environment might seem unfamiliar, but Altium will be there with resources to help you reach success. If you ever need help getting started or you are just looking for useful design tips, you can access an extensive knowledge base, webinars, and podcasts with design experts, the AltiumLive forum, and useful feature tutorials. Altium gives you all the resources you need to come up to speed quickly and reach design success.
No other design platform includes the important schematic design, component management, and layout features you need in a single program. Instead of using multiple programs with inconsistent workflow and separated features, you need to use the only integrated PCB design software that is adaptable to any application. Implement the ESD protection strategy and components your next device needs with Altium Designer.