In electronic product development, ESD (Electrostatic Discharge) protection is an essential part. Here, we will briefly introduce some useful knowledge and techniques regarding ESD diodes in core board product development.

Introduction to ESD Diodes

ESD (Electrostatic Discharge Protection Devices), also known as Transient Voltage Suppression Diode Arrays (TVS Array), are components designed with multiple TVS chips or diodes arranged in various layouts to serve specific functions. They are mainly used for ESD protection in various communication interfaces, such as USB, HDMI, RS485, RS232, VGA, RJ11, RJ45, BNC, SIM, SD, and others.

Characteristics of ESD Diodes

1. Low capacitance: Junction capacitance is low, usually in the pF range;

2. Fast response time: Typically in the ps range;

3. Small package size: Miniaturized components save PCB space;

4. High flexibility: Parameters such as capacitance, package type, and surge current capacity can be designed according to application needs.

Guide to Selecting ESD Diodes

1. The breakdown voltage V_RWM of the ESD diode must be greater than or equal to the highest operating voltage in the circuit;
2. The choice of pulse peak current I_PP and maximum clamping voltage V_C should be based on the maximum surge current that may occur on the line. It is important to note that V_C should be less than the maximum peak voltage that the protected chip can withstand;
3. When protecting high-speed signals, attention should also be paid to the frequency or transmission rate of the transmitted signal. When the signal frequency or transmission rate is high, low-capacitance series ESD diodes should be selected;
4. ESD diodes can be unidirectional (A) or bidirectional (C). Choose based on the working signal. Unipolar signals can use unidirectional ESD or bidirectional ESD, while bipolar signals should use bidirectional ESD.

Basic Principles for Selection

1. For the ESD design of general peripheral serial ports, use general low-speed ESD diodes with a breakdown voltage of 3.3V and a clamping voltage of 12V. The junction capacitance is 100pF, which reduces peak voltage through a 100-ohm series resistor. The reference design is as follows:

Figure 1: ESD Design Reference for Embedded Core Board M3568 UART Port

2. For the ESD design of SDIO high-speed signals, use low-capacitance high-speed signal-specific ESD protection devices to ensure that the communication quality of SDIO is not affected. The reference design is as follows:

Figure 2: ESD Design Reference for Embedded Core Board M3568 SD/MMC

3. For the ESD design of HDMI high-speed signals, use HDMI-specific interface protection devices, which not only provide ESD protection but also isolate and level-shift the EDID signal. The reference design is as follows:

Figure 3: ESD Design Reference for Embedded Core Board M3568 HDMI

Summary of ESD Protection Design

ESD diodes are widely used for ESD protection in communication lines and I/O ports of electronic products in various fields including communication, security, industrial, automotive, consumer products, and smart wearable devices. By purchasing ZhiYuan Electronics’ embedded core board products, you can obtain comprehensive and reliable hardware design references and supporting software drivers. The evaluation boards provided by ZhiYuan Electronics have undergone rigorous EMC testing and can provide test reports. Additionally, ZhiYuan Electronics offers thoughtful technical support services, such as schematic checks, assistance with troubleshooting, and custom solutions for special requirements, helping you overcome any obstacles in product development.