The use of the Universal Serial Bus (USB) has grown in industrial applications: for software uploads and configuration, diagnostics, maintenance, and connecting peripheral modules such as Wi-Fi routers, display screens, and human-machine interface (HMI) modules.
Since USB was primarily defined as a consumer electronics interface it is not inherently capable of handling large noise disturbances, ground bounce and ground potential differences that are common in industrial applications. In some applications, such as Uninterrupted Power Supply (UPS), controllers with the USB interface are on the high-voltage or ‘hot’ side, needing protective isolation to the USB connector. System designers also worry that any faults or ESD events on the exposed USB connector could interfere with the functionality of the industrial equipment. Due to these reasons, galvanically isolating the USB interface has become necessary in a broad spectrum of applications including factory automation, motor drives, medical equipment, power delivery, e-meters and data concentrators, in-flight entertainment and gaming consoles.
In this application brief, we discuss new isolated USB solutions from Texas Instruments, and their benefits over existing solutions.
Texas Instruments’ ISOUSB211 and ISOUSB111 devices are isolated USB repeaters that are compliant to USB 2.0 standard. Both devices offer basic and reinforced versions, with isolation rating up-to 5.7 kVRMS, surge test voltage up to 12.8 kV, and working voltage up to 1.5 kVRMS.
ISOUSB211 supports High Speed (HS, 480 Mbps) operation in addition to Full Speed (FS, 12 Mbps) and Low Speed (LS, 1.5 Mbps) modes and has the following benefits vs. existing solutions:
ISOUSB111 supports LS and FS modes for applications that do not need high bandwidth, with the following advantages over the current solutions:
EMC performance is a key care in industrial applications. Figure 1-4 shows the comparison of ISOUSB111 emissions performance with an equivalent competition device. The test setup was communication between a PC and a USB drive through ISOUSB111 and a 1 meter cable. ISOUSB111 has more than 20 dB lower emissions than competition and easily meets the CISPR32 Class B limit, while the competing device shows emissions higher than the limit.
Figure 1-5 shows ISOUSB211 emissions performance. The test setup was communication between a PC and a USB drive through ISOUSB211 and a 1 meter cable. ISOUSB211meets the CISPR32 Class B limit with margin. The noise peaking around 80 MHz is coming from isolated power converter included on the ISOUSB211EVM and not from ISOUSB211.
Figure 1-6 shows a summary of the ISOUSB211 and ISOUSB111 comparisons with competition that were discussed in the preceding sections.