In the previous article, we discussed the hazards and testing standards of ESD. This time, we will focus on the "main force of protection" - ESD protection diodes (also known as TVS diodes). How exactly does this seemingly simple component manage to dissolve kilovolt-level static electricity into nothingness in an instant? What unique designs does the ESD protection diode of Leiditech Electronics have? As a deep-rooted player in the ESD industry, Shanghai Leiditech has accumulated rich technical experience in anti-static dedicated devices. Now, let's take a detailed look at it for you.

1、From diode fundamentals to ESD protection-specific devices

Diodes are familiar faces in electronic circuits, and their core characteristic is "unidirectional conduction". However, ESD protection diodes are fundamentally different from ordinary diodes (such as rectifier diodes) - they are "special forces" specifically designed for "transient voltage suppression". The EMC guy from Leiditech often says that the core of the design of such dedicated devices is to "precisely apply force without adding interference" at critical moments.

1.1. "Family Classification" of diodes

• P-N junction diode: Composed of a P-type semiconductor (with multiple holes) and an N-type semiconductor (with multiple electrons), it conducts in the forward direction and cuts off in the reverse direction. Excessive reverse voltage can cause breakdown.

• • Schottky diode (SBD) : When metal and semiconductor come into contact to form a junction, it has a low conduction voltage and high speed, but its reverse breakdown voltage is relatively low.ESD protection diodes are an "upgraded version" of P-N junction diodes, optimized based on the principle of voltage stabilizing diodes, with a focus on enhancing "fast response during reverse breakdown" and "high current carrying capacity". This is also the key technical direction that Shanghai Leiditech has been focusing on for many years.

2、The "Working Wisdom" of ESD Protection Diodes

The core design goal of the ESD protection diode of Leidtech Electronics is: to remain "invisible" and not interfere with the circuit under normal circumstances, and to "strike instantly" and provide shunt protection when ESD strikes. How exactly can it be achieved? Through process optimization and structural innovation, Shanghai Leidtech has made this "offensive and defensive switching" more precise and efficient.

2.1. When working normally: As quiet as an "insulator"

When there is no ESD impact in the circuit, the ESD protection diode (with the cathode connected to the signal line and the anode grounded) is in a "reverse bias" state - the voltage across it is lower than the reverse breakdown voltage (VBR). At this time, it acts like a high resistor and hardly affects signal transmission.

However, there are two parameters that can affect signal quality and are also the key optimization directions of Leiditech:

• Total capacitance (CT) : When a diode cuts off, the "depletion region" of the P-N junction acts like a small capacitor. High-frequency signals (such as 5G, Thunderbolt) will be "absorbed" by this capacitor, resulting in signal attenuation. Through a special process, Leiditech has reduced the CT of its high-frequency series of polymer products to below 0.1pF, perfectly adapting to high-speed signals. This indicator has also been repeatedly verified by Leiditech's EMC team members in practical tests.

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  • Reverse leakage current (IR) : The tiny current flowing under normal voltage. Excessive IR will increase the power consumption of the circuit. The IR of Leiditehc products under VRWM (Maximum Reverse Operating Voltage) is usually ≤0.5μA, making them friendly to low-power devices.

  2.2. During ESD impact: It diverts quickly like a "safety valve"

  When an ESD pulse strikes (such as when plugging or unplugging an interface), the signal line voltage will instantly soar to several thousand volts. At this point, the ESD protection diode will:

  • Rapid breakdown conduction: When the voltage exceeds VBR, the diode enters an "avalanche breakdown" state, with a sudden drop in resistance (dynamic resistance RDYN is as low as a few ohms), directing most of the ESD current to ground (GND).
  • The clamping voltage (VC) is low enough: The voltage (VC) across the diode when it is conducting must be lower than the withstand voltage of the protected chip (for example, if the chip withstand voltage is 20V, VC should be ≤18V). Through the optimization of chip structure, Leiditech Electronics has made its VC level 15% to 20% lower than the industry average, providing more reliable protection. Leiditech EMC guys often refer to this advantage as "adding an extra layer of safety margin to the chip".
  • Bidirectional protection design: For cross-ground signals (such as audio lines and differential signals), Shanghai Leiditech’s bidirectional ESD protection diodes can simultaneously absorb positive and negative ESD pulses without the need for additional design.

  3、The three core advantages of Leiditech ESD protection diodes

  With years of technological accumulation, Shanghai Leiditech has endowed its ESD protection diodes with three core advantages, covering the full range of scenarios from low frequency to high frequency and from ordinary devices to high-end terminals:

  1. Fast response speed: From cut-off to conduction, it only takes sub-nanoseconds (<1ns), which is over 100 times faster than traditional varistors. It can intercept the "first peak" of ESD pulses, which is also the key reason why Leiditech Electronics is compatible with high-speed interfaces such as 5G and Thunderbolt.
  2. Controllable capacitance value: Covering the entire series from 0.05pF (high frequency) to 100pF (low frequency), it meets the requirements of different rate interfaces such as USB 3.2 and HDMI 2.1. The EMC delivery person of Leiditech will precisely recommend the corresponding capacitance value model based on the customer's signal rate.
  3. High consistency: The parameter deviation of VBR and VC in batch production is ≤±5%, avoiding unstable protection effects caused by component differences. Shanghai Leiditech's strict quality control system ensures that each component meets the design standards.

  Summary

  The core of an ESD protection diode is "balance" - it must not interfere with signals under normal operating conditions while also quickly and efficiently diverting ESD when it strikes. Through the triple optimization of materials, structure and process, Shanghai Leiditech has always adhered to the orientation of practical needs, making this "balance" more precise and reliable.

   

  In the next article, the EMC guy from Leiditech will move on to the practical part: teaching you how to choose the right model based on circuit requirements and the "pitfall avoidance guide" when laying out the circuit board to maximize the protection effect ~

   

  Shanghai Leiditech Electronics is committed to becoming a leading brand in electromagnetic compatibility solutions and component supply, offering products such as ESD, TVS, TSS, GDT, MOV, MOSFET, Zener, inductors, etc. Leiditech has an experienced R&D team that can provide personalized customization services based on customer needs and offer the most superior solutions to customers.