Circuit & System Protection

High speed noise suppression

27 July 2005 Circuit & System Protection Infrastructure Government and Parastatal (Industry)

Picked up from internal clocks by transmission lines, and radiated by USB cables acting as transmitting antennas, the problems of radiated and conducted noise are well known. These problems are compounded by the usual solution, the ferrite bead, which increasingly distorts the signal waveform as speed rises to USB2.0 (high speed mode) levels.

Murata has performed extensive development in its EMI research centres with material and winding technologies to solve these problems. That solution is high coupling and high common-mode impedance at high frequencies with Murata's wirewound common mode choke coils. Design features include 100 MHz common mode impedance of 67 to 2200 Ω, rated current from 200 to 370 mA, rated voltage 50 V d.c, DWV of 125 V d.c. and 0,3 to 1,2 Ω maximum DC resistance.

As ever, exact choice of part depends on the application and conditions but generally, Murata recommends the DLW21H series for USB lines in PCs, LVDS lines, peripherals, and small items like digital cameras. Especially for USB2.0, it suggests DLM21HN900SQ2 for data lines. Because of 'End of Packet' issues, the company does not recommend impedance values above 90 Ω. For common mode noise suppression in high speed and high-density digital equipment, the DLW21S series is a good choice. Both types are in a standard 0805 format. The DLW31S series performs similar functions in a 1206 package, but includes the higher values.

These highly-coupled choke coils are part of a large range of Murata EMI filters for almost any situation.

Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

Varistors for automotive applications
Future Electronics Circuit & System Protection
TDK Corporation has announced the addition of two new varistors to its AVRH series for automotive applications where both are characterised by the high electrostatic discharge-withstanding voltage demanded to ensure the safe operation of safety-critical automotive functions.

Clearing the Static: The importance of ESD wrist straps
Actum Electronics Circuit & System Protection
ESD clothing plays a pivotal role in preventing that people do not charge the products that they are working with.

Clearing the Static: ESD clothing and footwear
Actum Electronics Circuit & System Protection
ESD clothing plays a pivotal role in preventing that people do not charge the products that they are working with.

Navigating South Africa's cybersecurity regulations
Sophos Information Security Infrastructure
[Sponsored] Data privacy and compliance are not just buzzwords; they are essential components of a robust cybersecurity strategy that cannot be ignored. Understanding and adhering to local data protection laws and regulations becomes paramount.

Creating a cybersecurity strategy in a world where threats never sleep
Information Security Infrastructure
[Sponsored Content] The boom of Internet of Things (IoT) technology and the chaos that surrounded the sudden shift to work-from-home models in 2020 kick-started the age of cybercrime. In that period, incidents rose by 600%, affecting every industry and showing no signs of slowing down.

Gallagher Security’s achieves SOC2 Type 2 recertification
Gallagher News & Events Integrated Solutions Infrastructure
Gallagher has achieved System and Organization Controls (SOC2 Type 2) recertification after a fresh audit of the cloud-hosted services of its integrated security solution, Command Centre. The recertification was achieved on 21 December 2023.

Single-phase EMC filters
RS South Africa Circuit & System Protection
TDK Corporation has expanded its portfolio of single-phase EMC filters for AC and DC applications up to 250 V and rated currents from 6 to 30 A.

Cyberattacks the #1 cause of business outages
Editor's Choice Information Security Infrastructure
The latest survey by Veeam Software shows that 92% of organizations will increase their spending on data protection by 2024 to achieve cyber resilience due to continued threats of ransomware and cyberattacks.

Nology races to end 2023
Editor's Choice News & Events Infrastructure
Nology ended 2023 with an event highlighting its various products and services to the local market, followed by a few laps around the Kyalami Indoor Karting track.

Cybersecurity integrated with data protection
Technews Publishing News & Events Infrastructure
Last year's VeeamOn Tour conference in South Africa was a smaller version of the annual global Veeam conference, aimed at the company's regional partners and customers.