STMicroelectronics SMC30J40A

Overview

SMC30J40A from STMicroelectronics is a unidirectional transient voltage suppression (TVS) diode designed for high-energy surge protection in DC power lines and signal interfaces. It delivers 3000 W peak pulse power (10/1000 μs), clamps at 64.5 V (max) under 356 A surge current, and operates up to 175 °C junction temperature - enabling robust protection in industrial motor drives, telecom power supplies, and automotive body control modules.

For engineers reviewing the SMC30J40A datasheet, SMC30J40A pinout, SMC30J40A application, or SMC30J40A equivalent, key selection criteria include its 40 V standoff voltage (VRM), low 0.2 µA leakage at 25 °C, JEDEC-registered SMC package, and IEC 61000-4-2 ±30 kV ESD immunity - all critical for high-reliability overvoltage hardening in space-constrained, thermally demanding designs.

Technical Context

This planar-junction TVS diode uses silicon avalanche technology to provide fast response (<1 ns) to transients while maintaining low dynamic resistance (74.6 mΩ) and stable clamping across temperature. Its unidirectional polarity enables asymmetric protection on positive-rail DC systems without reverse conduction path concerns.

The device complies with IEC 61000-4-4 Level 4 (4 kV), exceeds IEC 61000-4-2 Level 4 (±30 kV air/contact discharge), and supports reflow soldering per J-STD-020 MSL Level 1 - confirming suitability for automated assembly in high-volume industrial and automotive electronics.

Key Specifications

Pinout & Package

SMC30J40A is housed in a JEDEC-registered SMC (DO-214AB) surface-mount package with matte tin-plated leads, optimized for thermal dissipation and automated placement. The package measures 7.75–8.15 mm × 5.55–6.25 mm × 2.45 mm max height and supports IPC-7531-compliant footprints.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMBJ40A and SAC30J40A, SMC30J40A uniquely combines 3000 W surge capability, 175 °C junction rating, and 64.5 V clamping - making it the only option qualified for high-energy, high-temperature deployments like industrial PLC I/O modules and automotive power distribution units.

Availability

SMC30J40A is available at Aetrix Electronics and suitable for industrial motor drives, telecom power supplies, automotive body control modules, and smart energy meter interfaces requiring stable component supply across extended product lifecycles.

Supply support for SMC30J40A 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 power management, analog, MEMS, and microcontroller technologies for industrial, automotive, and consumer markets.

The SMC30J TVS series targets high-reliability surge protection in harsh-environment electronics, emphasizing planar-junction robustness, low leakage, and extended temperature operation for mission-critical power and interface circuits.

FAQ

What is the maximum clamping voltage of SMC30J40A under a 356 A 10/1000 μs surge?

The maximum clamping voltage (VCL) is 64.5 V at 356 A for a 10/1000 μs waveform, measured at 25 °C ambient. This value increases with junction temperature at a coefficient of 10.1 × 10⁻⁴/°C, reaching ~70.2 V at 175 °C Tj - a critical design parameter for downstream voltage tolerance validation.

Can SMC30J40A be used in bidirectional signal line protection?

No - SMC30J40A is unidirectional and conducts only in reverse bias. For bidirectional protection (e.g., RS-485, USB), the complementary SMC30J40CA variant must be used. Mixing unidirectional and bidirectional types on the same line risks failure due to forward conduction during normal signal swing.

What is the thermal resistance (Rth j-a) of SMC30J40A on a standard FR4 PCB?

On a recommended footprint (5.11 mm × 8.19 mm copper pad per lead, 70 µm Cu thickness), Rth j-a is 120 °C/W for a single pulse. With 2 cm² total copper area under both leads, it improves to ~45 °C/W - enabling sustained operation at 175 °C junction temperature in forced-air-cooled industrial enclosures.

Does SMC30J40A meet automotive AEC-Q101 qualification?

No - SMC30J40A is not AEC-Q101 qualified. While it operates up to 175 °C and meets ISO 7637-2 surge test levels when applied correctly, STMicroelectronics does not list it in their AEC-Q101-certified TVS portfolio. For automotive safety-critical applications, AEC-Q101-qualified alternatives like SMAJ40A-Q or TPSC40A must be selected.