STMicroelectronics SMC50J85A

Overview

SMC50J85A from STMicroelectronics is a unidirectional 5000 W transient voltage suppression (TVS) diode designed for high-energy surge protection in DC power rails and signal lines. It features a standoff voltage (VRM) of 85 V, clamping voltage (VCL) of 137 V at 1000 A (8/20 µs), dynamic resistance (RD) of 275 mΩ, and operates up to 175 °C junction temperature - enabling robust protection in industrial SMPS, telecom power supplies, and automotive body electronics.

For engineers reviewing the SMC50J85A datasheet, SMC50J85A pinout, SMC50J85A application, or SMC50J85A equivalent, key selection criteria include its 85 V working voltage, sub-0.2 µA leakage at 25 °C, JEDEC-registered SMC package compatibility, and IEC 61000-4-2 ±30 kV ESD immunity - critical for high-reliability front-end protection where low leakage and thermal stability are mandatory.

Technical Context

The SMC50J85A employs planar silicon avalanche technology optimized for fast response (<1 ns) to ESD and electrical overstress events. Its unidirectional configuration provides asymmetric clamping with cathode-anode polarity, supporting DC-biased lines where reverse conduction must be blocked.

It delivers 5000 W peak pulse power (10/1000 µs) and up to 178 kW (8/20 µs), with VBR specified at 95–105 V (min–max) and temperature coefficient αT = 10.6 × 10⁻⁴ /°C - enabling accurate clamping voltage prediction across –55 °C to +175 °C operating range.

Key Specifications

Pinout & Package

The SMC50J85A is housed in a JEDEC-registered SMC (DO-214AB) surface-mount package with matte tin-plated leads, compatible with IPC-7531 footprint and J-STD-020 MSL Level 1 handling. The package measures 7.75–8.15 mm × 5.55–6.25 mm × 2.45 mm max height and supports reflow per ST's 240–245 °C peak profile.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMBJ85A and SAC50-85, the SMC50J85A uniquely balances 5000 W surge capacity, 0.2 µA leakage, and unidirectional polarity - making it optimal for high-reliability 85 V DC rail protection where thermal stability and minimal standby loss are non-negotiable.

Availability

SMC50J85A is available at Aetrix Electronics and suitable for industrial SMPS input protection, automotive body control modules, telecom DC distribution, and renewable energy inverter DC link applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for SMC50J85A 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, designing and manufacturing analog, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The SMC50J TVS series targets high-reliability surge protection in space-constrained, thermally demanding environments - specifically engineered for 5000 W transient suppression in SMC packages with extended temperature and low-leakage performance.

FAQ

What is the maximum clamping voltage of SMC50J85A under a 1000 A 8/20 µs surge?

The maximum clamping voltage (VCL) is 137 V at 1000 A for an 8/20 µs waveform, measured at Tj = 25 °C. This value increases with junction temperature per αT = 10.6 × 10⁻⁴ /°C, reaching ~145 V at 125 °C - a critical factor for margin analysis in high-ambient designs.

Can SMC50J85A be used in bidirectional signal lines like RS-485?

No - SMC50J85A is unidirectional and conducts only when cathode-to-anode voltage exceeds VBR. For bidirectional lines, ST offers the SMC50J85CA variant (marked EDZ with cathode bar omitted), which provides symmetrical clamping for AC-coupled or differential signals.

How does the 0.2 µA leakage current impact low-power battery-operated systems?

At 0.2 µA maximum leakage at 85 V and 25 °C, the SMC50J85A contributes negligible drain - less than 1.7 µW - making it suitable for always-on battery-backed systems such as smart meters or remote sensors where annual self-discharge must stay below 1%.

Is the SMC50J85A compliant with lead-free soldering standards?

Yes - it features matte tin-plated leads and is qualified for lead-free reflow per J-STD-020 MSL Level 1, with a peak temperature rating of 240–245 °C. The recommended profile includes 60–90 seconds above 217 °C and controlled ramp rates to prevent package cracking.