SMCJ140(C)

Overview

The SMCJ140(C) is a surface-mount TVS diode in the popular SMC (DO-214AB) package. It's designed to protect sensitive electronic components from damaging voltage transients caused by electrostatic discharge (ESD), lightning, and other surge events. As part of the SMCJ series, it offers robust protection with a 1500W peak pulse power rating. This diode is particularly valued in industrial and automotive applications where reliable surge protection is critical. Its compact size makes it suitable for high-density PCB designs while maintaining excellent transient suppression capabilities. The (C) suffix typically indicates tighter parameter tolerances or special screening for critical applications.

Structure and Working Principle

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The SMCJ140(C) consists of a silicon avalanche diode structure in a surface-mount package. When the voltage across the diode exceeds its breakdown voltage (140V in this case), it rapidly conducts, clamping the voltage to a safe level. The device remains in high-impedance state during normal operation. The internal structure features a large junction area to handle high transient currents. The DO-214AB (SMC) package provides good thermal characteristics while maintaining a small footprint (6.9mm × 5.5mm). This construction allows the diode to absorb significant transient energy without damage to itself or the protected circuit.

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Key Features

The SMCJ140(C) offers a standoff voltage of 140V with a typical breakdown voltage of 155.4V. Its peak pulse current rating of 10.1A (8/20μs waveform) and low clamping voltage make it effective for protecting sensitive ICs. The diode responds to transients in picoseconds, providing nearly instantaneous protection. Additional features include a wide operating temperature range (-55°C to +150°C) and excellent stability over time. The device is lead-free and RoHS compliant, meeting current environmental regulations. Its bidirectional version (common for TVS diodes) protects against both positive and negative voltage transients.

Application Areas

Primary applications include industrial control systems, automotive electronics, telecommunications equipment, and power supplies. It's commonly used to protect data lines, power buses, and I/O ports in these systems. The 140V rating makes it suitable for 24V-48V DC systems with appropriate design margins. In automotive applications, the SMCJ140(C) protects against load dump transients and other voltage spikes common in vehicle electrical systems. Industrial uses include PLCs, motor drives, and measurement equipment where electrical noise and surges are prevalent. The diode is also found in consumer electronics that require robust ESD protection.

Maintenance and Precautions

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While TVS diodes are generally maintenance-free, proper installation is crucial for reliable operation. The SMCJ140(C) should be placed as close as possible to the protected line's entry point on the PCB. Adequate trace width is necessary to handle surge currents without excessive voltage drop. Designers should ensure the diode's working voltage exceeds the normal operating voltage of the protected circuit. Thermal considerations are important in high-surge environments - multiple devices may be needed for very high energy transients. The diode should not be used outside its specified voltage and temperature ratings.

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B2B Procurement Guide

When procuring SMCJ140(C) diodes in bulk, verify the manufacturer's qualifications and product traceability. Major manufacturers include Littelfuse, Vishay, and STMicroelectronics. Consider requesting samples for testing before large orders. Lead times can vary from 4-12 weeks depending on market conditions, so plan accordingly. For critical applications, specify automotive-grade (AEC-Q101 qualified) or industrial-grade versions as needed. Purchasing through authorized distributors helps ensure genuine components and reliable supply chains. Volume pricing typically starts at quantities of 1,000 pieces.