IoT (Internet of Things) refers to the access control system that can be connected to network and remotely controlled through the internet. In an IoT-based smart home system, some sensor-embedded devices are used to gather environmental data for the system to process and analyze. Then the system can identify and automatically take corresponding actions to improve comfort, increase efficiency and optimize energy usage. A smart home system – for example, the cloud-based home automation – is generally the integration of three components: the terminal units (sensors, devices and actuators), Edge Gateway, and the cloud computing and storage system. At present, an additional central control device is usually added to the smart home system available on the market after the installation of peripheral equipments to form an internal network. Through this central control device, it is able to connect to the cloud server via home modem/router for setting up the whole system.
When setting up the home automation, it is usually made DIY by consumers. Therefore, one of the most common issues that the consumers will encounter is various external interferences, and ESD (Electrostatic Discharge) is a common destructive interference. Although the chips have been tested by ESD test standard in factory before shipment, but it is component-level ESD testing (ANSI/ESDA/JEDEC JS-001-2017) used to simulate the ESD events that happen in a well-controlled manufacturing and assembly environment. In contrast with the component-level simulation, ESD is a much more complex issue in real-world cases. The level of static buildup can vary depending on operating environment or end-user’s clothing and objects carried. The level rating is normally described as system-level discharge (IEC 61000-4-2). IEC 61000-4-2 standard is used to simulate the more powerful and destructive ESD strikes. If such energy delivered to a device without sufficient ESD protection during the strike, it may lead the system to run into abnormal situation or cause damage to the internal circuit and chip, which influence consumer experience.
How to solve ESD problem?
At the product design stage, engineers install TVS (Transient Voltage Suppressor) diodes as ESD protection to prevent damage to the circuit. TVS diode is a passive component to provide protection and suppress sudden high-voltage spikes. Compared with traditional protection components such as Zener diodes and the varistor, TVS diode offers higher flexibility to address a variety of applications, and is more stable with greater protection. For this reason, TVS diodes are widely used by hardware engineers to protect products from damage and interference.
During the design, TVS diodes should be placed right behind the external interface (I/O Ports, i.e. USB, Audio Jack, Power Jack and RJ45), where are the direct connections to external ports from internal circuit. Upon an extremely high level of external surges enters the system, TVS diodes will be able to quickly react to voltage spikes and clamp the voltage to prevent devices from being interfered by the surges. As for the comparison between different types of TVS diodes, the closer the clamping voltage is to the normal operating voltage, the more effective the protection.
In addition to the external interface, TVS diodes are also required for some system designs of human interaction with portable devices, such as touch panel and button, where the static electricity generated by human body may go into the system through these interactive modules. Adding TVS diodes near the edge between the PCB and these modules are needed for this type of system design to enhance performance stability.
In a smart home system, some devices are powered by batteries only. In this case, energy consumption becomes an important factor to be taken into consideration during setting up, and it makes some engineers hesitate to adding TVS diodes. However, since TVS diode is a passive component, it does not work under normal operating conditions and has very low leakage current (as low as nA range at operating voltage). It reacts only when an external ESD strike enters exceeding its Vbr (breakdown voltage).Once the ESD strike ceases, TVS diode will returns to inactive state until the next ESD event.
Compared with traditional protection components like varistor, TVS diode is a semiconductor component made through circuit design and semiconductor manufacturing process, which can be specifically designed and characterized for various applications. Taking the products of Amazing Microelectronic Corp. as an example: a low-capacitance TVS diode (AZ5B75-01B, 0.1pF) is suitable for use in antenna application; array TVS diode (AZ1143-04F, 4 channel) is suitable for multi-channel signal lines; a TVS diode with low operating voltage (AZ6118-01F, Vrwm=1.8V) is suitable for the use in low-voltage system, and a TVS diode with ultra-low clamping voltage (AZ5B0S-01F, 5.5V@8kV ESD) is suitable for sensitive signal line.
With over 15 years experience in TVS diode research, development and manufacturing industry, Amazing Microelectronic Corp. offers a complete range of protection for various applications. The following figure shows the Transient Voltage Suppression protection solutions provided by the Amazing Microelectronic Corp. for IoT Home Automation.
