STMicroelectronics BZW50-39

Overview

BZW50-39 from STMicroelectronics is a unidirectional transient voltage suppression (TVS) diode designed for high-energy surge protection in power supply and interface lines. It delivers 5000 W peak pulse power (10/1000 µs), clamps at 69.4 V (max) under 72 A surge, and operates up to 175 °C junction temperature-ideal for industrial SMPS input stages and telecom line protection.

For engineers reviewing the BZW50-39 datasheet, BZW50-39 pinout, BZW50-39 application, or BZW50-39 equivalent, key selection criteria include clamping voltage vs. surge current, temperature coefficient of breakdown voltage (10.1 × 10⁻⁴ /°C), dynamic resistance (0.299 Ω), leakage current ≤5 µA at 39 V, and R6 package thermal performance on FR4 PCBs.

Technical Context

The BZW50-39 employs planar junction technology to achieve low leakage (<5 µA at VRM = 39 V) and stable VBR (43.3 V min, 43.3 V typ at 1 mA) across –55 °C to +175 °C. Its unidirectional configuration provides forward conduction path during negative transients while blocking reverse DC bias up to 39 V.

Clamping behavior is defined by dynamic resistance (0.299 Ω) and temperature-dependent VCL (αT = 10.1 × 10⁻⁴ /°C), enabling accurate overvoltage prediction under real-world surge conditions (e.g., IEC 61000-4-4 level 4, 4 kV). The device sustains 5000 W (10/1000 µs) and up to 3700 W at Tj = 175 °C.

Key Specifications

Pinout & Package

The BZW50-39 is housed in the axial-leaded R6 package (DO-201AD), featuring two terminals: anode and cathode. Cathode is marked by a band on the body. Lead finish is matte tin plating, compliant with J-STD-002 and RoHS.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar transient voltage suppression applications.

Compared with SMBJ39A and P6KE39A, BZW50-39 offers 8.3× higher peak power rating, verified 30 kV ESD immunity, and guaranteed 175 °C operation-making it the only option qualified for high-reliability industrial and telecom surge protection where sustained energy dissipation and thermal stability are critical.

Availability

BZW50-39 is available at Aetrix Electronics and suitable for industrial SMPS input protection, telecom line interface, automotive body control modules, and PLC analog input protection requiring stable component supply and long-term lifecycle support.

Supply support for BZW50-39 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 microcontrollers, power devices, sensors, and analog ICs for industrial, automotive, and consumer markets.

The BZW50 series belongs to ST's high-power TVS diode product line, engineered specifically for robust, high-temperature surge protection in mission-critical power conversion and communication infrastructure applications.

FAQ

What is the maximum clamping voltage of BZW50-39 under a 10/1000 µs surge?

The maximum clamping voltage (VCL) of BZW50-39 is 69.4 V when subjected to a 72 A peak pulse current with a 10/1000 µs waveform at 25 °C. This value increases with junction temperature at a rate of 10.1 × 10⁻⁴ /°C, so thermal design must account for elevated Tj in high-power applications.

Is BZW50-39 suitable for bidirectional surge protection?

No-BZW50-39 is unidirectional. For bidirectional protection, use the BZW50-39B variant, which features symmetrical clamping in both polarities and identical electrical ratings except for polarity-independent behavior. The "B" suffix denotes bidirectional construction.

How does the R6 package affect thermal performance on a standard PCB?

Mounted on FR4 with 70 µm copper, the R6 package achieves a thermal resistance (Rth j-a) of ~40 °C/W with 2 cm² copper area per lead. At 175 °C junction temperature, this allows sustained 3700 W surge capability-significantly higher than typical SMB or SMC packages due to superior heat spreading via axial leads.

Does BZW50-39 meet IEC 61000-4-5 requirements?

BZW50-39 is rated for 5000 W (10/1000 µs), matching the energy level of IEC 61000-4-5 combination wave (1.2/50 µs voltage, 8/20 µs current) at medium coupling. While not explicitly tested to IEC 61000-4-5 in the datasheet, its 60 kW rating at 8/20 µs and UL 497B listing confirm suitability for primary-level protection in systems complying with that standard.