SZESD9901MX2WT5G ESD Protection Diode Specifications and Applications

ElecSuppliers Part Number GuideSep 26, 2026

SZESD9901MX2WT5G is an automotive-qualified ESD protection device from onsemi designed for high-speed automotive data networks. It is intended to protect sensitive electronic circuits from electrostatic discharge, surge events, and other transient disturbances.

The device is designed for OPEN Alliance 100/1000BASE-T1 Ethernet and other high-speed data network applications. Its low capacitance helps reduce the impact of the protection device on high-speed signal integrity.

The part uses an extremely compact X2DFNW2 package measuring approximately 1.00 mm × 0.60 mm × 0.37 mm, making it suitable for space-constrained automotive PCB designs.

SZESD9901MX2WT5G Electrical Characteristics

SZESD9901MX2WT5G is a bidirectional ESD protection device with a maximum working reverse voltage of 25V. Its typical maximum capacitance is approximately 2.6pF.

The device has a high trigger voltage of at least 100V, helping it remain inactive during normal signal operation while responding to high-voltage transient events.

The maximum peak pulse current is specified at 2.2A for an 8/20µs pulse. The device is also specified for high-level ESD protection under the applicable test conditions.

SZESD9901MX2WT5G ESD Protection

ESD events can introduce high-voltage pulses into automotive communication interfaces through connectors, wiring harnesses, and other exposed signal paths. Without appropriate protection, these transients can damage the Ethernet PHY or cause system malfunction.

SZESD9901MX2WT5G provides a shunt protection path for transient energy. Under normal operating conditions, its low leakage and low capacitance allow the high-speed data signal to pass with limited loading.

During an ESD or transient event, the protection device conducts and limits the voltage applied to the protected circuit.

SZESD9901MX2WT5G Automotive Ethernet

100BASE-T1 and 1000BASE-T1 Ethernet are increasingly used for communication between automotive electronic control units, sensors, cameras, domain controllers, and other vehicle systems.

These networks require protection devices that can withstand automotive transient environments without significantly degrading the high-speed data channel.

SZESD9901MX2WT5G is designed specifically for this type of application. Its single-line bidirectional configuration allows it to be placed directly on the automotive Ethernet signal path.

SZESD9901MX2WT5G Capacitance

Low capacitance is important for high-speed automotive Ethernet because additional capacitance on the signal line can affect signal rise time, impedance, insertion loss, and overall communication performance.

SZESD9901MX2WT5G has a maximum capacitance of approximately 2.6pF according to onsemi product information.

When selecting an ESD protection device for a high-speed network, engineers should evaluate the capacitance together with the complete PCB transmission line and PHY interface rather than considering the protection component independently.

SZESD9901MX2WT5G Package

SZESD9901MX2WT5G uses the X2DFNW2 package. The nominal package dimensions are 1.00 mm × 0.60 mm × 0.37 mm with a 0.65 mm terminal pitch.

The package includes wettable flank construction, which can improve solder-joint visibility during automated optical inspection. This feature is particularly useful for automotive electronics manufacturing where automated inspection and process control are important.

The extremely small package also allows the protection device to be placed close to the connector or PHY interface without consuming significant PCB area.

SZESD9901MX2WT5G Automotive Qualification

The SZ prefix identifies the automotive and other applications requiring additional site and change-control requirements. SZESD9901MX2WT5G is AEC-Q101 qualified and PPAP capable.

This makes the device suitable for automotive electronic systems where component qualification, production traceability, and manufacturing process control are important.

The device is also specified as lead-free, halogen-free and RoHS compliant.

SZESD9901MX2WT5G Operating Temperature

The specified operating junction temperature range is -55°C to +150°C. This provides a wide temperature margin for automotive electronics operating under demanding environmental conditions.

The actual PCB temperature should still be evaluated as part of the complete system design. Thermal conditions can vary significantly depending on the location of the ECU, enclosure, airflow, nearby power devices, and vehicle operating environment.

SZESD9901MX2WT5G Applications

SZESD9901MX2WT5G is designed for automotive high-speed data networks. Typical applications include 100BASE-T1 Ethernet, 1000BASE-T1 Ethernet, in-vehicle networking, automotive gateways, electronic control units, automotive cameras, sensors, domain controllers, and other high-speed vehicle communication systems.

It can be placed on the connector side of the Ethernet transceiver PHY to provide protection against external transient events entering the communication interface.

SZESD9901MX2WT5G PCB Design

The placement of an ESD protection device is important in high-speed automotive Ethernet designs. The protection component should generally be positioned close to the point where the transient can enter the PCB.

Short connections between the external connector, protection device, and protected circuit can help reduce parasitic inductance during a fast transient event.

At the same time, the high-speed differential signal path must maintain appropriate impedance and routing symmetry. Engineers should follow the recommended PCB layout and signal-integrity practices for the Ethernet interface.

SZESD9901MX2WT5G Surge Protection

Automotive electrical systems can experience transient events beyond conventional ESD pulses. ISO 7637-2 and ISO 7637-3 address several types of electrical disturbances encountered in vehicle environments.

SZESD9901 is designed for automotive transient protection and is specified for relevant automotive electrical transient requirements, including jumpstart, load dump, and applicable ISO 7637 pulse conditions.

The complete protection strategy should still consider the vehicle power architecture, Ethernet interface, common-mode protection, grounding, and other transient protection devices.

SZESD9901MX2WT5G Sourcing

When sourcing SZESD9901MX2WT5G, buyers should verify the complete onsemi part number because similar SZESD9901 devices may use different package configurations or ordering codes.

The exact part number identifies the X2DFNW2 package and tape-and-reel ordering configuration. Procurement specifications should include the manufacturer, complete part number, quantity, packaging requirements, delivery schedule, and applicable automotive quality requirements.

For automotive production programs, buyers should also confirm AEC-Q101 qualification and PPAP requirements where applicable.

SZESD9901MX2WT5G for Automotive Ethernet

SZESD9901MX2WT5G provides compact transient protection for high-speed automotive Ethernet interfaces. Its bidirectional operation, approximately 2.6pF maximum capacitance, 25V working voltage, high trigger voltage, automotive qualification, and ultra-small X2DFNW2 package make it suitable for modern in-vehicle networking designs.

For new automotive Ethernet designs, engineers should evaluate the ESD protection device together with the connector, PCB transmission line, Ethernet PHY, common-mode behavior, and vehicle-level transient requirements to ensure reliable communication and protection performance.