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These cookies ensure basic functionalities and security features of the website, anonymously. Necessary cookies are absolutely essential for the website to function properly. “Removing Ground Noise in Data Transmission Systems,”Thomas Kugelstadt, Texas Instruments, SLLA268, October 2007.
DIGITAL ISOLATOR APPLICATION NOTES HOW TO
While at first this might appear to be a design limitation, Figure 3 shows how to isolate a variety of digital and analog interfaces all having in common that the isolator is placed in the single-ended, 3V/5V section of the isolated interface.įigure 3: Digital isolators must be placed within the single-ended section of an isolated interface.įor more information on digital isolators please refer to the application literature in the reference section. Because their design utilizes 3V/5V, high-speed CMOS technology, they do not conform to any specific interface standard, but are designed to isolate digital, single-ended data lines only. SiO 2 has the least aging effect, thus, extending the life expectancy of capacitive isolators well beyond those of competing technologies.įigure 2: Internal construction of a digital, capacitive isolator.ĭigital isolators are available as single-, dual-, triple-, and quad-channel devices for unidirectional and bidirectional operation. Its inter-level dielectric is a 16 μm level of silicon dioxide (SiO 2 ), one of the most robust isolation materials. Internal construction of the isolator consists of a transmitter and a receiver chip, with the isolation barrier being provided through a small high-voltage capacitor ( Figure 2 ). While there are a wide variety of isolation technologies such as optocouplers, inductive isolators, giant magnetoresistance (GMR) isolators, and capacitive isolators, the digital, capacitive isolator has proven to be the most reliable solution for harsh, industrial environments. Hence, modern isolator design is focused mainly on digital isolators. The easiest and least-expensive approach to signal isolation, however, lies in the digital domain. Today’s data acquisition and data transmission systems often require isolating multiple signal channels, i.e., for data and control signals. Their small bandwidth, high power-consumption, and single-channel design present significant limitations to modern electronic designs.
Therefore, breaking ground loops through galvanic isolation not only prevents loop currents, but also presents the most reliable method of dealing with high ground potential differences.Įarly isolation techniques used standard transformers and analog isolation amplifiers. These ground loop currents then induce voltages into transmission signal wires, causing signal distortion and possible data errors. Ground loop currents can be extremely high, because they connect different ground potentials via low-impedance wire ( Figure 1 ).įigure 1: Eliminating ground loops through galvanic isolation. When providing a direct connection between the transmitter ground and a remote receiver ground, for example by the means of a ground wire, an unintentional ground loop is created. Remote-located power sources, however, can experience large ground-potential differences due to multiple, non-standardized, earthing techniques, which are also the cause for multiple ground paths.
Thus, remote-located nodes draw their supply from different points in the electrical installation system. The various nodes of a communication network commonly use local grounds as their reference potential. While the first case is easily understandable, the second one requires some further explanation.
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