Technology Edge

June 2009 Edition

The Technology Edge is a monthly online technical publication that features articles written by National Semiconductor's Engineers. These articles discuss National products, applications and techniques for solving your analog and mixed-signal design challenges, as well as other pertinent technical information.

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AN-1973: Benefits and Challenges of High-Frequency Regulators

Overview: Space constraints exist in many electronic designs. Beyond portable handsets, applications such as industrial instrumentation, point-of-sale terminals, and portable medical devices also have board space and height restrictions. Switching regulators with high switching frequency present an engineer working on a space-constrained design with an effective means to minimize solution size. National Semiconductor’s newest high-frequency regulators offer a combination of high switching frequency and ease of use, thereby reducing solution size and complexity. Besides solution size, a well-designed high switching frequency regulator has the advantage of a faster transient response and reduced output voltage ripple.

There are a few considerations to keep in mind when using a high switching frequency regulator in a design. Careful layout must be considered to reduce EMI and improve the performance of the device. Also, the IC packaging selection and printed circuit board layout must be considered for dissipating heat in smaller spaces.

AN-1881: Improving Electromagnetic Noise Immunity in Serial Communications Systems

Overview: Electronic communications devices that operate in environments with a high level of electromagnetic noise require special consideration and testing to ensure the continuous delivery of uncorrupted data. Communication devices are susceptible to data interruption and corruption in industrial, automotive, telecommunication, medical and test lab environments, to name just a few. Demonstrating compliance with international immunity testing standards helps to ensure robust communications in noisy electromagnetic environments. This article provides key recommendations for implementing serial communication systems that exceed Electro-technical Commission (IEC) immunity test standards. To provide an example of highly reliable serial communications system implementation and testing, National Semiconductor’s DP83640 Ethernet physical layer device was tested for IEC immunity test compliance. Results from these tests are included for reference. The scope of this article is restricted to communication signals; immunity issues related to AC and DC power supply signals are not included.