Why USB Type-C Cables Need Protection

USB 3.1 Superspeed+ is the updated interface standard that doubles the data rate to 10 Gbps – a 2x improvement of the previous generation USB 3.0 Superspeed. With a power delivery projected at 100 W, this new standard gives users enhanced data encoding for more efficient data transfer from higher throughput and improved I/O power efficiency.

In addition to the increased power capability and bandwidth achieved in this USB standard, the connector has been changed. The new USB Type-C™ connector features 24 pins in a smaller form factor to combine multiple connector functions into one.

A downside to the increased power is that the extremely tight pin spacing on the new connector can be a safety and fire hazard threat due to the possibility of thermal runaway at the connector. To remedy these threats, it is recommended that electronic equipment, connector and cable manufacturers integrate overcurrent and overtemperature protection into the Type-C connector.

Pin spacing at the Type-C connector is 0.50 mm leaving it susceptible to shorting. Small debris such as dust, sweat and water entering the connector could cause a full short. In order to prevent such events, Bourns has developed two solutions that can be easily designed into Type-C cables – Thermal Cutoff (TCO) devices and Polymeric Thermal Cutoff (P-TCO) devices.

k1982_tco_ptco_600x400Offering an effective overtemperature protection solution, Bourns® TCO devices, also known as mini-breakers, incorporate existing technology in such a way to enhance their protection capabilities. TCO devices have been proven to protect cables from damage from overheating by acting independently of any controller. Constructed with a bimetal switch and PTC in parallel, the Bourns® TCO family delivers the best features of both. Since a PTC latches and does not have a mechanical contact, it offsets the bimetal switch’s lack of latching providing a significant design advantage. Similarly, the bimetal switch enhances the TCO solution by providing a higher operating current and precise control.

An additional overtemperature protection solution, the Bourns® P-TCO family offers a combination of compact, surface mount packaging and ultra-low resistance delivering optimized thermal protection. It can be specifically calibrated to trip and go into a highly resistive state dependent on ambient temperature. P-TCO device trigger temperatures are specified at 85 °C at 3 A (±15 °C) and 100 °C at 2 A (±10 °C) with derating values for a wider temperature range.

Adding Bourns® TCO and P-TCO overtemperature devices in USB Type-C cable connectors provides an additional level of protection and safety that is not available in many cable designs today. The two solutions also give designers added cost, space and precise protection and activation benefits. Plus, TCO and P-TCO solutions allow USB Type-C manufacturers to create a more reliable cable design that provides vital network protection that encompasses the host, dock, hub and peripherals.  Users will appreciate the faster performance and power delivered from USB Type-C without the worry of overheating or risk of fire.

k1982_app_note_teaserFind out more about how TCO and P-TCO devices help protect USB Type-C cables in a helpful Bourns application note.

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