1/3/2024 0 Comments Usb 2.0 opto rf isolator![]() USB peripherals are built using the block diagram shown in Figure 1. In most current designs the SIE and transceiver are integrated, making interface (2) inaccessible. There are three possible interfaces where a USB peripheral could be isolated: site 1, the USB bus itself site 2, the transceiver interface and site 3, the application interface. The D+ and D- signals are bidirectional, operating at a signaling rate of 12Mbps (83ns per bit cell). The V BUS wire provides 5V of power up to 500mA. The USB connector contains four wires: two to supply power (V BUS and GND) and two to move the USB data (D+ and D-). ![]() A 12Mbps device operates with enough bandwidth for useful data transfers, and employs a data rate that is manageable for designs that use inexpensive optocouplers. This article discusses optical isolation of a full-speed (12Mbps) USB connection. Two obvious isolation applications are medical, where PC-based instruments are attached to patients, and industrial, where large supply rail offsets can occur. If you need to electrically isolate a device that is to be connected to a PC, USB is a natural connection interface because of its extensive industry support. The Universal Serial Bus (USB) has become the standard way to connect peripherals to personal computers. The SPI interface can run at any speed and consists of simple, unidirectional signals. A USB controller that attaches to your embedded system using the SPI interface is easy to electrically isolate. ![]() ![]() USB's extensive industry support and simple structure (only four wires in a USB cable) make it a popular PC interface. If you must isolate a device that also connects to a PC, the USB interface is a natural choice. ![]()
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