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Programmable Shielding Technique for High Speed, Sensitive Digital Signals

IP.com Disclosure Number: IPCOM000239076D
Publication Date: 2014-Oct-09
Document File: 4 page(s) / 155K

Publishing Venue

The IP.com Prior Art Database

Abstract

Present day electronic devices are very complex, accommodating lots of functionality but with low area and low power consumption. All these complex functions are generally achieved by doing more operations in less time (increasing the speed) and less data exchange and processing at that speed. As a result of high speed data transmission, lots of switching noise gets coupled with sensitive digital signals and data may become corrupted. To get rid of these capacitive coupled noise shielding of sensitive digital signal, is an obvious choice.

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Programmable Shielding Technique for High Speed, Sensitive Digital Signals

INTRODUCTION

Present day electronic devices are very complex, accommodating lots of functionality but with low area and low power consumption.  All these complex functions are generally achieved by doing more operations in less time (increasing the speed) and less data exchange and processing at that speed.  As a result of high speed data transmission, lots of switching noise gets coupled with sensitive digital signals and data may become corrupted. To get rid of these capacitive coupled noise shielding of sensitive digital signal, is an obvious choice.

BACKGROUND

There are two types of shielding techniques used in industry.  One is “static shielding” and the other is “dynamic shielding”.  In static shielding, the sensitive signal is shielded (surrounded) by some supply or ground.  As a result, switching and other noise affects the shield but not the signal being shielded.  In static shielding, the sensitive signal is now less coupled with noise but due to the presence of surrounding static signal, effective capacitive load of the signal may become higher, which in turn makes the signal rise and fall time higher.  That is, it become sluggish.  This is not good for high speed data communication.  In dynamic shielding, the same signal is fed to the shield so that the signal and the shield move in the same phase, so the above-mentioned capacitive load does not come into the picture. As a result, signal rise and fall time remains intact or better, but that improvement happens at the cost of power.  Examples of active and passive shielding are shown in Figure.1.

Figure. 1:  (a) Static or passive shielding (b) Active shielding

Problem Description and Motivation for Improvement

As discussed above, static shielding signal has to drive high capacitive load, which is extremely unsuitable for high speed applications.  On the other hand, active shielding is good for high speed applications but at the cost of power consumption.  In present complex applications, the data rate, and the clock rate change dynamically according to the application.  For example, in the case of gaming or video applications, the data and clock rates must be high while for simple email and any other simple applications, the data rate may be reduced by a huge fraction.  The SOC has to be designed for the worst case or for high speed applications.  Now, according to the high speed application, once one type of shielding is implemented then that cannot be changed so even for low speed applications the active shielded part will continue to consume power.  A...