Get High-Speed USB Port Protection for Industrial Voltages

June 5, 2018

Christine Young By: Christine Young
Blogger, Maxim Integrated 


Because it provides fast communications, USB is being quickly adopted for industrial applications such as real-time diagnostics of factory equipment, programming and service ports on programmable logic controllers (PLCs), and camera vision systems. Compared to legacy RS-232 connectors, USB provides a faster solution that is also 5x smaller, ideal for automated factory environments where speed and increasingly smaller footprints are desirable.

An important consideration for these applications is, USB ports do require protection from overvoltage and overcurrent, which can damage the host and device sides. The ports should be protected from faults and incorrectly wired 24V AC/40V DC power supplies. All signals, such as VBUS/GND and D+/D-, must be protected. At the same time, these ports are expected to support high-speed data rates up to 480Mbps.

Some designers have attempted to address this by implementing highly complex discrete solutions, which supports only low-speed and full-speed USB (1.5 and 12Mbps). Discrete architectures can require up to 40 components. Over-voltage and current-limiting is another option and is available to protect up to 40V, though it protects only the power lines, not the communications lines. Still others have turned to isolated USB ICs. However, this approach also doesn’t support high-speed USB, it’s expensive, and the chips are relatively large (and with isolated USB options, if a big common-mode shift occurs, communication can still occur when there's a fault.)

Automated chocolate factoryAutomated factories, even those that produce chocolate, have PLCs where USB port protection is essential.

A solution that is capable of providing high levels of port protection is needed, as there hasn’t been a high-speed USB port protection solution on the market that protects data and power lines from 24V AC/40V DC powered industrial equipment.

Protection Via a Smaller, Simpler Design

Maxim's new MAX22505 +/-40V high-speed USB port protector protects data and power lines from 24V AC and 40V DC powered industrial equipment. The device is the market’s only solution to provide high-speed USB port protection (480Mbps) for industrial voltages, ensuring robust communications in harsh environments cost-effectively and in a smaller, simpler design compared to alternative solutions. The device supports the most often used USB operation speeds, 1.5Mbps (low), 12Mbps (full), and 480Mbps (high), with no configuration changes. When the chip detects a fault, the switch opens up and doesn’t allow continued communications, thus protecting the host or device from damage. Compared to a discrete architecture, the MAX22505 requires at least 50% fewer external components. It’s 120mm2 solution size is 50% smaller than discrete solutions.

Applications that can benefit from the robust communications that the MAX22505 can ensure include building automation, in-flight entertainment, industrial PCs/PLCs, and fault-protected USB cables. An evaluation kit, MAX22505EVKIT, is available for you to assess the chip.