Ask any financial planner for retirement savings advice and the first answer you’ll get will always be the same: “It’s never too early to start planning for retirement.” Much the same advice is true for circuit designers responsible for incorporating circuit protection technologies into the designs of today’s increasingly compact wireless and wearable devices.
Effective circuit protection is essential to safeguarding both the device and the user. Without it, the device’s sensor circuits, battery-charging interfaces, buttons or data I/Os could be irreparably damaged by ESD. Planning for circuit protection is always better done sooner rather than later. However, it can be challenging to convince circuit designers that circuit protection is important from the beginning of the design process. Because they don’t perceive circuit protection as adding value to the end-product or enhancing the capabilities of the application, too many circuit designers ignore it until the end of the process when it’s time for EMC testing. At that point, discovering the board has insufficient ESD protection usually means expensive delays to the project schedule.
Considering ESD protection early in the design phase gives circuit designers the flexibility to choose the ideal protection device and select the optimal layout/location before their options become limited by other components, including transformers, common mode chokes and passives. If there’s insufficient time to do a complete ESD protection analysis during the early phase of the board layout, it’s usually possible to locate sockets at each I/O or location where ESD is expected to enter the application.
A variety of circuit protection options are available for protecting against ESD, but the best solution must take into account the circuit’s characteristics, cost and board implementation. For example, although a ferrite bead can be a low cost, marginally effective ESD solution for low-speed circuits, it is not appropriate for high-speed circuits like USB 2.0, USB 3.0, HDMI, etc. For these circuits, the inductance that will remediate the ESD pulse will also cause serious signal integrity issues. It would be better to use a low capacitance TVS diode or diode array (typically less than 1pF) in parallel with the data line to shunt the ESD transient away from the IC. This solution is ideal since the low capacitance will not interfere with the data signal transfer, while the clamping action of the TVS diode/diode array protects the IC.
Fortunately for circuit designers, a new tool is available that can simplify the process of identifying the ESD suppression device best suited to an application, which makes it far easier to incorporate circuit protection earlier in the board planning process. The Littelfuse iDesign™ Online Simulation and Product Selection Tool narrows down the ESD suppression device part number options available in just four steps. Circuit designers simply enter the system and device parameters, and then choose up to three devices for comparison. A built-in simulation tool allows evaluating an ESD device’s performance without the delay or expense of building and testing multiple board prototypes.
To learn more about how the easy to use iDesign online tool can help you incorporate circuit protection into your board design process earlier, view the Littelfuse iDesign Tutorial Videos. You can also register for FREE access to the iDesign online tool here.
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