Although ESD diodes are protective devices, they have their own "limits" and can also fail in harsh application scenarios.The scenarios most likely to cause ESD diode failure fall into three main categories. The first is a "high-frequency repetitive ESD discharge environment"—such as industrial touch screens, USB ports that require frequent plugging and unplugging, and metal housing buttons. In these scenarios, the ESD diode faces not a single large surge, but hundreds or even thousands of repeated moderate-level electrostatic discharges. The energy accumulates gradually, the PN junction degrades over time, and ultimately the protective device turns into a conductive short circuit. The second is a "high-temperature plus ESD superimposed environment," such as automotive center consoles, BMS, and devices with high-density PCB layouts. As the temperature increases, the ESD diode's withstand capability drops noticeably, and an electrostatic discharge of the same intensity is more likely to cause thermal damage under high temperatures. The third is a humid environment—moisture and contaminants form leakage paths on the PCB surface, causing the electrostatic discharge to no longer be uniformly distributed and making it easy to burn through the PN junction.
Simply put, ESD diodes and TVS diodes are essentially both semiconductor transient suppression devices, but each has its own "area of expertise". ESD diodes are specifically designed for electrostatic discharge scenarios — extremely fast response time (picosecond level), very low junction capacitance (typically only 0.5–3 pF), and ultra-compact packaging, making them ideal for high-speed signal interfaces such as USB, HDMI, and USB-C. Their job is to quickly discharge static electricity generated by human or equipment contact to ground, protecting downstream chips from damage.
Many engineers, when selecting components, first look at the device's specified ESD rating — for example, "withstands ±15kV air discharge" — assuming that a higher value means better protection. However, in practical applications, failures often occur: even when using an ESD diode with a supposedly high rating, the device still gets punctured by surges in the field, and the chip burns out as well.The key issue is that the ESD voltage rating is only one dimension, not a universal indicator. It shows the device's tolerance under standard ESD testing, but does not represent its clamping performance, surge current capability, or compatibility with high-speed signals. For instance, some ESD diodes may have a high ESD withstand voltage, but their "clamping voltage" after turn‑on is too high, meaning the protected chip can still be damaged by residual voltage spikes. In other cases, the parasitic capacitance of the device is too large at high frequencies, causing a USB 3.0 interface to run at only USB 2.0 speeds.
Electrostatic discharge is actually everywhere. When a person walks in a dry environment, their body can accumulate several thousand volts of static electricity. When you plug or unplug a USB interface or touch a device button, these static charges are instantly discharged onto the circuit board. One such small pulse may not kill the device on the spot, but if repeated hundreds or thousands of times, the tiny internal structures of the chip will be gradually damaged, eventually leading to degraded performance or complete failure.So how can you tell if the ESD protection is the problem? Watch for these signs: product repair returns are concentrated on interface‑related failures; the failure rate of the same model increases significantly during dry seasons (autumn and winter); or the returned chips show obvious "breakdown points". If your product frequently experiences these issues, it is very likely that the ESD protection selection is inadequate.
TVS (Transient Voltage Suppression) is a voltage limiting protection device that functions similarly to a varistor. It also utilizes the nonlinear characteristics of the device to clamp overvoltage to a lower voltage value to protect the downstream circuit. The tolerance is expressed in watts (W). Based on the excellent characteristics of TVS tubes, bidirectional TVS is suitable for AC circuits and can absorb high-power pulses that occur instantaneously in both positive and negative directions.
Transient voltage suppressor, abbreviated as TVS, is a high-efficiency protective device in the form of a diode. When the TVS diode is subjected to transient high-energy impact, it can quickly respond (in the order of P seconds) to transform the high impedance between its two poles into low impedance, absorb surge power of up to several kilowatts, stabilize the voltage between the two poles at a safe value,
