Silencing EMI at the Source

Proactively designing for quiet electronic applications is significantly less costly than retroactively stamping out unwanted electromagnetic interference (EMI) after failing electromagnetic compatibility (EMC) testing.

It's widely estimated that as many as 50% of applications fail EMC testing the first time around. Retesting fees, board spins, lab time, and project delays can easily add up to $10,000 or more, along with the costs of manufacturing and distribution delays. A good rule of thumb to follow: The best EMC fixes happen before the first prototype.

Designers can reduce uncertainty and guesswork by selecting components from a single, well-curated EMC product line such as that offered by Würth Elektronik. The company's comprehensive portfolio of over 5,000 EMC components includes ferrites, inductors, capacitors, absorbers, shielding materials, and more, all designed and tested to work well together.

With the ongoing demand for miniaturization, EMC is increasingly becoming an issue. IoT sensor nodes, for example, are increasingly common in smart homes, industrial, medical, and agricultural environments, but are prone to EMI.

IoT sensors rely on small printed circuit boards, dense layouts, switch-mode power supplies, microcontrollers, and integrated wireless radios, virtually guaranteeing a hubbub of potential noise. A tiny board may incorporate DC/DC converters, antennas, and high-speed signals—all competing to disrupt signal integrity.

Curated EMI solutions, such as Würth’s WE-EMIP patches and matched ferrite arrays, can help bring order to potential chaos by reducing emissions, preserving signal integrity, and enabling smoother paths to compliance.

Design guidelines

Envision an environmental sensor that transmits data over a Bluetooth Low Energy (BLE) radio. The wrong switching regulator can radiate noise. The BLE antenna is sensitive to interference, and digital communication lines can emit EMI through power rails.

Here's a simplified guide on how Würth components might be implemented in an EMC-ready design:

• Würth’s WE-CBF chip ferrites can be placed in series with power supply lines—typically at the input and output of the buck regulator—to attenuate high-frequency switching noise. This helps suppress conducted EMI to keep power rails clean and limit emissions through PCB traces or cables.
• Decoupling and bulk capacitors can be paired with ferrites to smooth transients on VCC and reduce ripple. The Würth Elektronik 860040573003 aluminum electrolytic capacitor is designed to suppress EMI and radio frequency interference (RFI), providing stable operation in power supplies, home appliances, smart meters, and IoT devices requiring reliable line filtering.
• The 371001 WE-EMIP EMI Absorber Patch (Figure 1) can be applied directly over or near noisy components such as switching regulators or BLE system-on-chip (SoC) modules to absorb radiated EMI, and isolate antennas and sensitive circuitry from localized interference.

Figure 1: Würth’s WE-EMIP patch provides an easy-to-apply way to isolate sensitive components from EMI. (Image source: Würth Elektronik)

• A common-mode choke like the WE-CMB HC series 74482210002 can suppress noise on the AC mains input for uses such as preventing smart home devices from polluting the supply grid or ensuring clean power in electrically noisy industrial environments.
• EMI-sensitive components, such as MCUs, SoCs, wireless modules, and clock oscillators, can be shielded using a 14.12 mm x 14.12 mm x 2.00 mm surface-mounted, tin-plated steel cover like the WE-SHC series 3600213120S (Figure 2) for compact embedded applications. 

Figure 2: Würth's WE-SHC series 3600213120S shields EMI-sensitive components in a compact, surface-mounted enclosure. (Image source: Würth Elektronik)

Würth Elektronik’s range of circuit protection varistors guard against voltage transients from lightning strikes or ESD events. Designers can also take advantage of Würth’s filter choke inductors for differential-mode suppression. Also available are filter design kits that incorporate curated assortments of passive components, like ferrites, chokes, and capacitors. These are tailored for EMI suppression across various use cases, providing designers with practical, hands-on methods to prototype and evaluate EMC solutions.

The company also offers complementary components that can streamline the development of compact, connected environmental sensors. These include pre-certified radio modules for cellular IoT, Wi-Fi, and Bluetooth connectivity, as well as MEMS-based temperature and humidity sensors to provide reliable, low-power data acquisition in a small form factor.

Conclusion

Würth Elektronik components form a comprehensive toolkit for building robust, EMC-compliant applications tailored to the demands of modern IoT and electronic systems. These components address key challenges such as EMI suppression and voltage transient protection while enhancing the reliability and performance of compact, connected environmental sensors. The company's extensive EMC catalog and design kits provide designers with a curated one-stop shop to meet their needs.