Issue link: https://resources.mouser.com/i/1437732
17 littelfuse.com LEARN MORE Littelfuse setP™ Temperature Indicators The close confines of a USB-C connector can also make it challenging to fit a protection device inside. Polymeric positive temperature coefficient (PPTC) devices suitable for protecting 60W chargers typically have a 1210 (3.2mm × 2.5mm) footprint, and mini-breakers are often even bigger. PPTCs and mini-breakers meant to protect 100W would need to be even more significant. Also, mini- breakers have relatively weak mechanical structures. The cable assembly process can deform the bi-metal materials from which they're constructed, which would prevent them from protecting against a heating fault. PolySwitch setP™ Digital Temperature Indicators One way to address these disadvantages is to place a different type of protection device in the communication channel (CC) of the USB-C connector rather than on the V BUS line. One of the latest devices developed to protect USB-C cables against over-temperature conditions is the compact (2.0mm × 1.2mm) PolySwitch setP digital temperature indicator (Figure 2). The setP device senses a temperature increase and then alerts the system to shut down the power flow. Here's how it works: A setP digital temperature indicator is placed on the connector's CC line, and when it senses temperatures higher than 100°C, it switches from a low-resistance state to a high-resistance state. This heightened resistance causes the voltage on the CC line to increase beyond the value defined by the USB Implementers Forum (USB-IF) to determine whether the source and sink are detached. The charging system assumes that the cable has become detached because the voltage is higher than the value outlined in the specification, so the charging system turns off the power through the V BUS line. This prevents the connector, cable, and device from being charged from overheating. Once the user disconnects the cable and removes the connector's debris, the cable can resume normal operation. With a compact 0805 (2.0mm × 1.2mm) footprint, setP devices are at least 30 percent smaller than most other solutions used for this application in the past. Their rigid physical structure also allows them to withstand modern cable assembly and molding operations reliably. They're well-suited for use in USB-C charging cables, USB Power Delivery charging cables, and chargers with captive USB-C cables. Conclusion USB-C cables offer owners a fast, uncomplicated way to recharge mobile devices and transfer data. With the development of a new solution for temperature indication, they can be confident that the process will remain safer. ■ Figure 2: PolySwitch setP digital temperature indicators help protect USB-C plugs from overheating. They are designed to the specifications of USB-C and help protect even the highest levels of USB Power Delivery. (Source: Mouser Electronics)