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15 2024-08

　　RS485 communication interface application self recovery fuse

　　PPTC (Self Recovering Fuse), as we all know, has a wide range of applications and is often used as a current limiting protection device in portable computers, automotive electronics, communication interfaces, and electronic industrial control equipment. Of course, self recovering fuses are also one of the most widely used overcurrent protection devices we currently know of.

　　So, how is the protective effect it can provide actually achieved?

　　Our common communication interfaces include RS232, RS485, etc., both of which are popular communication interfaces in the market, especially RS485. When the communication speed is 100kbps, its communication distance can reach over 1200 meters, and it also has a good signal-to-noise ratio. At the same time, its price is also relatively advantageous.

　　However, due to its long-term exposure to outdoor environments and complex working voltage of only 5V, it is prone to damage when facing ESD and lightning strikes. Therefore, how to solve ESD and lightning surge has become a top priority. When facing such products, PPTC self-healing fuses play a crucial role.

　　A self-healing fuse is composed of a polymer matrix and carbon black particles that make it conductive. It is a positive temperature coefficient polymer thermistor that can be used in RS-485 communication interface applications with a resistance value of 1.35 Ω to 6.5 Ω and a non operating current of 100mA to 200mA. To a large extent, it can replace current fuses. When normal operating current flows through it, its resistance value is very small and can be seen as a wire. However, when the current flowing through the circuit is twice or more than the normal operating current, its resistance value will increase, thereby playing a role in current limiting protection. When the power supply is disconnected and the overcurrent disappears, the fuse will return to its factory low resistance value.

　　Therefore, for RS-485 communication interface, PPTC self recovery fuse can fully play its current limiting role and provide protection, which shows that it is very suitable.