Signal Transmission On the primary side, the incoming USB 2.0 high-speed traffic from the USB-C connector is received by ISOUSB211. Across the gap, there's a ISOUSB211 ASIC for isolated USB signal transmission, an isolated DCDC converter module for power transmission, and two Y-capacitors for EMI suppression. Both sides have independent power and ground planes, and are separated by a 6.4-millimeter gap. Theory of Operation The single-board PCB is physically separated into the primary (host) side and secondary (device) side with an isolation barrier in between. The 1000+ V dielectric withstand voltage represents a measure of immunity to transient voltages, not a voltage for continuous operation. The operating voltage should stay within the Safety Extra-Low Voltage limit (42.4 VRMS, or 60 VDC). It should be clear that this development board, while it indeed has a dielectric withstand voltage of more than 1000 volts, it's not designed, not tested, and should not be used for safety-critical purposes. Warning In industrial and medical applications, galvanic isolation is used to protect equipment and human lives from hazards. Creepage & Clearance: 6.4 mm Insulation Type: Functional Insulation Maximum Operating Voltage: 42.4 VRMS, 60 VDC. Board Specifications Dielectric Withstand Voltage: at least 1000 VDC (likely 3000 VDC, tests needed). This project is a development board design for the ISOUSB211 ASIC, to facilitate hardware evaluation and experiments by other developers in the community, hopefully to help solving your USB problems in your systems. Currently, the chip is in the pro-production preview stage, but the engineering sample chip, XISOUSB211, is already available for purchase. In November 2020, Texas Instruments have released the first 480 Mbps High-Speed USB isolation ASIC to the open market - ISOUSB211. The USB 3.0 fiber optics + VL670 ASIC for 3.0 to 2.0 translation solution, or the CH317 Ethernet extension ASIC solution, which I both described in this thread, are examples of these limitations. Previously, the available isolators are either expensive (FPGA-based solutions), difficult to buy (ASIC isolators unavailable on the open market), inconvenient to use (USB over CAT-5 or fiber optics, which requires a receiver and a transmitter), or with many compatibility problems due to technical limitations in the solution, or a combination of these problems. Nevertheless, high-speed USB is required in many applications, such as high-speed data converters, software-defined radios, or logic analyzers. Unfortunately, although USB 2.0 isolators for Low Speed (1.5 Mbps) and Full Speed (12 Mbps) are readily available, there are few isolators for High-Speed USB (480 Mbps) interfaces due to the complexity of its protocol. The best practice is to "float" the device-under-test instead of the scope itself, which is accomplished by a USB isolator. To overcome this problem, engineers often "cheat" by disconnecting the protective ground to "float the scope", but it creates a safety hazard and makes the oscilloscope unsafe - a fault within the oscilloscope can energize its entire chassis. In this case, one cannot make a measurement between two arbitrary points in the circuit - connecting the "ground" of the oscilloscope probe to a voltage source is effectively a short circuit. The signal ground of an oscilloscope input is usually connected to AC mains ground for safety, and the device-under-test (such as a USB gadget) is often also referenced to ground. * Finally, in hardware development, galvanic isolation allows engineers to make a floating measurement without compromising safety. The most common example is a "ground loop" in audio and video systems, but amateur radio operators with cheap, low-EMI-immunity USB software defined radios can potentially find reliefs from noise as well. * Next, galvanic isolation is useful to stop unwanted conductive electromagnetic interference between the computer, the USB device, and their power supplies. It can be used by embedded system developers and hardware hackers to protect their computers from unexpected faults during development or experiments - the most infamous example is the USB Killer, but more practical examples include a short circuit from +12 V to +5 V, or a back-EMF from an electric motor or inductor, which may create a brief transient of several hundreds volts. * First, galvanic isolation protects the computer from destruction by high voltage transients and faults. Often, implementing galvanic isolation (electrical isolation) is desirable. Quote Motivation USB 2.0 is one of the most commonly used data interfaces.
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