PPTC (self-recovery fuse), we all know that it is a wide range of applications, often in a number of portable computers, automotive electronics, communications interfaces and electronic industrial control and other equipment as a current-limiting protection, of course, the self-recovery fuse is also known to us in the overcurrent protection devices used in the wider use of a device product.
So, it can provide to the protective effect is actually how to realize? Today, Youen editorial from the communication interface this application scenario to give you an example of introduction.
Our common communication interface RS232, RS485, etc., these two are more popular in the market communication interface, especially RS485, it is in the communication rate of 100kbps, the communication distance can reach more than 1200 meters, but also has a better signal-to-noise ratio, while the price is also more advantageous.
However, due to its long-term exposure to the outdoors, the environment is complex, and its own operating voltage is only 5V, so in the face of ESD and lightning strikes, easy to be damaged, therefore, how to solve the ESD and lightning surge, has become a top priority.
After UEN Semiconductor engineers continue to conduct experimental testing and ESD static rectification process, we found that, in the face of such products, PPTC self-recovery fuses play a key role.
Recoverable fuse is composed of polymer matrix and make it conductive carbon black particles, is a positive temperature coefficient of polymer thermistor, in the RS-485 communication interface applications can be used in the resistance value of 1.35 Ω to 6.5 Ω, the non-operating current of 100mA to 200mA of the fuse. It is from a large degree, is a substitute for the current fuse, in the flow of normal operating current, its resistance value is very small, depending on a wire, but when the circuit is flowing through the current is 2 times the normal operating current or more than 2 times the current, its resistance value will become large, and then play a role in limiting the protection of the current, when the power supply is disconnected, the disappearance of the overcurrent, the fuse will be restored to the factory's low resistance value.
Therefore, for RS-485 this kind of communication interface, PPTC self-recovery fuse can fully play its current limiting role, to protect it, so it can be seen that it is very suitable.