STMicroelectronics SMC30J18A

Overview

SMC30J18A from STMicroelectronics is a unidirectional transient voltage suppression (TVS) diode designed for high-energy surge protection in DC power rails and signal lines. It delivers 3000 W peak pulse power (10/1000 μs), clamps at 29.2 V (max) under 103 A surge current, and features low leakage (0.2 µA at 25 °C) and high junction temperature rating (175 °C). It is used in industrial power supplies and telecom interface circuits requiring IEC 61000-4-2 (±30 kV contact/air) and IEC 61000-4-4 (4 kV level 4) compliance.

For engineers reviewing the SMC30J18A datasheet, SMC30J18A pinout, SMC30J18A application, or SMC30J18A equivalent, this device is selected for robust ESD and EOS protection where low dynamic resistance (21.4 mΩ), stable clamping voltage across temperature, and JEDEC-standard SMC package compatibility are critical design requirements.

Technical Context

The SMC30J18A employs planar silicon avalanche technology to achieve precise breakdown at 18 V (V_BR min = 20 V, typ = 21.1 V, max = 22.2 V), enabling fast response (<1 ns) to transients while maintaining low capacitance (≈100 pF at 0 V, decreasing with reverse bias). Its unidirectional configuration supports DC-biased lines without forward conduction during normal operation.

Thermal performance is optimized for high-reliability applications: maximum junction temperature is 175 °C, thermal resistance R_th(j-a) drops to <100 °C/W with ≥3 cm² copper area per lead, and it withstands reflow up to 245 °C per J-STD-020 MSL Level 1. Dynamic resistance (R_D = 21.4 mΩ) ensures minimal voltage overshoot under high-current surges.

Key Specifications

Pinout & Package

SMC30J18A uses the industry-standard SMC (DO-214AB) surface-mount package: 7.75–8.15 mm length × 5.55–6.25 mm width × 2.45 mm height, matte tin-plated leads, JEDEC-registered outline, IPC-7531 compliant footprint. Thermal pad area under each lead directly impacts R_th(j-a); recommended copper area ≥3.14 cm² per lead.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar unidirectional TVS diode applications.

Compared with SMBJ18A and 1.5KE18A, SMC30J18A provides 5× higher surge power handling than SMBJ18A and superior manufacturability versus 1.5KE18A, making it the optimal choice for modern SMT-based industrial and telecom systems requiring certified 4 kV EFT and ±30 kV ESD immunity.

Availability

SMC30J18A is available at Aetrix Electronics and suitable for industrial power supplies, telecom interface protection, automotive body control modules, and smart metering systems requiring stable component supply, full traceability, and long-term lifecycle support.

Supply support for SMC30J18A includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in automotive, industrial, and power management solutions with vertical manufacturing capabilities and broad IP portfolio.

SMC30J18A belongs to ST's SMC30JxxA TVS diode family, engineered specifically for high-reliability DC rail protection in harsh environments where extended temperature operation, low leakage, and certified surge immunity are mandatory.

FAQ

What is the maximum surge current SMC30J18A can handle?

SMC30J18A sustains 103 A peak pulse current under the standard 10/1000 μs waveform, corresponding to its 3000 W peak pulse power rating at 25 °C ambient. Derating applies above 25 °C per Figure 3 in DS8598; at 125 °C, maximum PPP drops to ~1800 W.

Is SMC30J18A RoHS and REACH compliant?

Yes - SMC30J18A is manufactured in ST's ECOPACK2-compliant facilities, meeting RoHS Directive 2011/65/EU and REACH Regulation (EC) No. 1907/2006. Lead finish is matte tin, and halogen-free packaging is standard per ST's environmental policy.

Can SMC30J18A be used in bidirectional configurations?

No - SMC30J18A is unidirectional only. For bidirectional protection at 18 V standoff, use SMC30J18CA (marked "3BAJ"), which has symmetrical breakdown in both polarities and identical power ratings but different leakage behavior under reverse bias.

What is the recommended PCB footprint for thermal reliability?

ST recommends a minimum 3.14 cm² (≈1.54″ × 1.54″) copper area under each lead, using internal/external layers connected via ≥4 thermal vias per pad (0.3 mm diameter, 0.8 mm spacing). This achieves R_th(j-a) ≈ 90 °C/W, critical for sustained 175 °C operation.