Currently, hardware designers of high-speed interfaces are commonly caught in a protection dilemma. When implementing ESD protection for high-speed devices such as 5G communication modules, Wi-Fi 7 routers, USB4, and Thunderbolt, conventional TVS devices—although meeting surge discharge requirements—often cause issues such as signal eye diagram closure and deteriorated antenna VSWR after installation, severely degrading signal transmission performance. Engineers are forced to choose between two options: sacrificing protection and risking chip damage, or sacrificing signal integrity to retain protection. In one project, an ESD device with high junction capacitance was selected, causing eye diagram closure that delayed certification for months. In another, a product with excessively high clamping voltage resulted in persistently high failure rates of terminal chips, ultimately leading to a large-scale recall. The core of the problem lies in the parasitic junction capacitance of protection devices. USB 3.1 requires capacitance below 0.5pF, while ultra-high-frequency links such as RF antennas and 5G millimeter-wave have tightened the requirement to the 0.05pF level. Conventional TVS devices generally have junction capacitance above 0.5pF, which, when connected in parallel to signal lines, effectively forms a low-pass filter that attenuates high-frequency components and disrupts impedance matching, ultimately causing data errors.

To address this challenge, Shanghai Leiditech has launched the PESD series of ultra-low capacitance polymer ESD devices, with typical capacitance as low as 0.05pF, response time <1ns, and ESD protection up to ±25kV. Under normal conditions, the device exhibits extremely high impedance, appearing nearly "transparent" to the signal; when an ESD event occurs, it rapidly switches to a low-impedance discharge path, providing transparent protection. Against the backdrop of declining native ESD capability in advanced process nodes (28nm and below, with HBM standards dropping from 2kV to 1kV), the PESD series has become the optimal choice for balancing signal integrity and chip safety.

I. Leiditech Ultra-Low Capacitance ESD Devices - PESD Series: Core Advantages and Model Matrix

Core product advantages:

1. Extremely ultra-low parasitic capacitance: Typical junction capacitance of only 0.05pF, far superior to conventional low-capacitance TVS devices (0.1~3pF). In ultra-high-speed transmission scenarios from 10Gbps to 40Gbps, signal eye diagrams show no significant degradation.

2. Nanosecond transparent ESD discharge: Response time <1ns, quickly turning on when an ESD event occurs, without interfering with high-frequency signal transmission throughout the process.

3. Full specification coverage for multiple scenarios: Operating voltage coverage from 3.3V to 36V, available in all mainstream SMD packages (0201/0402/0603/2510), with both unidirectional and bidirectional options.

4. High-level ESD protection capability: Supports air discharge of ±25kV and contact discharge of ±15kV, easily meeting stringent system-level ESD test standards (air ±15kV, contact ±8kV).

Complete model parameters are as follows:

II. Typical Application Examples

Based on Leiditech's actual test data and rectification case studies, the ultra-low capacitance (0.05pF) ESD devices are primarily applied in the following three high-risk scenarios:

1、RF antennas and millimeter-wave communication（RF Antenna & mmWave）

This is the area where 0.05pF ESD devices truly excel. On GPS, Wi-Fi 6E/7, 5G millimeter-wave, and NFC antenna ports, any parallel capacitance can cause frequency deviation (detuning) and reduced antenna efficiency.

Application solution: At the antenna switch or PA (power amplifier) output, select components such as the PESD2442U005 (24V operating voltage, 0402 package) or PESD0521U005 (5V, 0201 micro package) for ground-referenced protection.

Effect: Thanks to the extremely low capacitance, the antenna's S11 parameters (return loss) and radiation performance are almost unaffected, while effectively preventing human-body ESD from damaging the expensive RF front-end chip.

2、Ultra-high-speed data interfaces（USB4 / Thunderbolt / HDMI 2.1）

As USB4 and Thunderbolt 4 transmission rates surge to 40Gbps, signal tolerance for parasitic capacitance has dropped to 0.1pF or even lower.

Application solution: On the TX/RX differential pairs of the Type-C interface, conventional low-capacitance TVS can cause eye diagram closure. Using Leiditech's PESD series (e.g., 0.05pF version) ensures signal integrity.

Effect: Meets strict compliance tests such as USB-IF requirements, passes eye mask testing, and provides ±30kV ESD protection to prevent electrostatic damage during hot-plugging.

3、High-speed camera and display interfaces（MIPI / LVDS）

The MIPI interfaces (D-PHY/C-PHY) of smartphone cameras and displays are operating at increasingly higher data rates.

Application solution: Within limited PCB space (e.g., 0201 or 0402 packages), use models such as PESD0542U005 to protect the data lines.

Effect: Resolves issues such as "snow noise" in high-pixel camera transmission or display anomalies, eliminating image stuttering caused by ESD interference.

III. Core Considerations for Ultra-Low Capacitance ESD Selection

When selecting 0.05pF-class PESD devices, it is essential to distinguish the technology path and match electrical parameters to avoid performance and reliability issues caused by incorrect selection:

1. Distinguish device technology paths: Conventional low-capacitance TVS devices on the market are mostly silicon-based PN junction structures, which, due to physical limitations, have difficulty achieving both low leakage current and ultra-low capacitance below 0.1pF. Polymer PESD relies on voltage-triggered nonlinear resistance based on a nano-conductive network, and is currently the only mature solution that can stably achieve 0.05pF-class capacitance. It should be prioritized for high-frequency signal protection.

2. Match rated working voltage: The device VRWM (rated working voltage) must be greater than or equal to the normal working voltage of the line. For example, for a 3.3V signal line, choose a 3.3V or 5V-rated PESD to prevent leakage and signal distortion under normal conditions.

3. Verify clamping voltage Vc: Although PESD has outstanding capacitance advantages, its clamping voltage under the same discharge current is generally higher than that of high-power silicon-based TVS. Always check the device's Vc parameter to ensure the clamping voltage is lower than the maximum withstand voltage of the protected chip, to prevent the chip from being damaged by overvoltage during an ESD event.

4. Distinguish signal line and power port protection: PESD is primarily designed for ESD protection on high-speed signal lines (RF, USB, HDMI, MIPI, etc.), with lower energy tolerance and surge capability compared to high-power TVS. For device VBUS power ports with high current surge and EOS risks, Leiditech's SD series, SMAJ/SMBJ/SMCJ series dedicated power TVS devices should be used in combination for coordinated protection.

As communication, consumer electronics, and high-definition imaging equipment continue to evolve toward higher speeds and frequencies, RF, high-speed data, and imaging links impose dual mandatory requirements on ESD protection: "ultra-low capacitance and high ESD withstand capability." Leveraging its industry-leading ultra-low parasitic capacitance characteristics, Leiditech's 0.05pF polymer PESD series provides a transparent ESD protection barrier without compromising RF or high-speed signal transmission quality. Suitable for various high-frequency sensitive circuits, it helps avoid mass-production risks such as certification failures and product recalls from the outset, offering a highly reliable standardized ESD protection solution for hardware R&D.