A set-top box is a device that connects a television to an external signal source. In order to obtain more data sources, the device can generally provide many types of options, generally supporting USB HDMI、 Ethernet interface, hard disk interface, etc. Because various data type interfaces are susceptible to various fault states such as overvoltage, overcurrent, ESD static electricity, etc. during hot plugging, corresponding protection should be added at the input end of the interface in the product design process to ensure product reliability.