STMicroelectronics BZW50-33B

Overview

BZW50-33B from STMicroelectronics is a bidirectional transient voltage suppression (TVS) diode designed for high-energy surge protection in power lines and signal interfaces. It delivers 5000 W peak pulse power (10/1000 µs), clamps at 59 V (max) under 85 A surge, and operates up to 175 °C junction temperature-enabling robust protection in industrial motor drives and telecom power supplies.

For engineers reviewing the BZW50-33B datasheet, BZW50-33B pinout, BZW50-33B application, or BZW50-33B equivalent, key selection criteria include clamping voltage consistency across temperature, bidirectional symmetry for AC-coupled circuits, low dynamic resistance (0.218 Ω), and compliance with IEC 61000-4-2 (30 kV contact/air) and IEC 61000-4-4 level 4 (4 kV).

Technical Context

The BZW50-33B uses planar silicon junction technology optimized for low leakage (<5 µA at 33 V) and stable breakdown behavior over temperature (α_T = 10 × 10⁻⁴/°C). Its bidirectional structure ensures symmetrical clamping in both polarities without external polarity management.

It supports high-reliability operation under repeated surges due to its 175 °C maximum junction temperature rating and thermal impedance profile suited for FR4 PCBs with standard copper area-enabling sustained performance in high-ambient environments like base station power modules and railway signaling interfaces.

Key Specifications

Pinout & Package

Supplied in R6 axial-leaded package (JEDEC DO-201AD), with cathode identification via molded band (bidirectional version has no polarity marking; terminals are symmetric).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMBJ33CA and 1.5KE33CA, BZW50-33B offers superior thermal robustness (175 °C vs. ≤150 °C), lower leakage (5 µA vs. ≥50 µA), and tighter clamping (59 V vs. ≥64.8 V), making it optimal for high-reliability 48–110 V DC systems requiring long-term stability.

Availability

BZW50-33B is available at Aetrix Electronics and suitable for industrial motor drives, telecom power feeds, AC/DC SMPS inputs, and railway signaling interfaces requiring stable component supply across extended product lifecycles.

Supply support for BZW50-33B 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, delivering innovative solutions across automotive, industrial, power, and analog markets since 1987.

The BZW50 series belongs to ST's high-power TVS diode portfolio, engineered specifically for industrial-grade surge immunity in harsh-environment power conversion and communication infrastructure.

FAQ

What is the maximum clamping voltage of BZW50-33B under a 10/1000 µs surge?

The maximum clamping voltage is 59 V when subjected to an 85 A peak pulse current with a 10/1000 µs waveform at 25 °C. This value increases linearly with junction temperature at a coefficient of 10 × 10⁻⁴/°C, reaching approximately 62.5 V at 175 °C junction temperature.

Is BZW50-33B suitable for AC line protection?

Yes-its bidirectional construction allows direct placement across AC mains or transformer secondaries without polarity concerns. It meets IEC 61000-4-4 level 4 (4 kV) and withstands repetitive surges up to 5000 W, making it appropriate for Class II AC/DC adapter inputs and isolation barrier protection.

How does the R6 package affect thermal performance compared to SMD alternatives?

The R6 axial package provides superior thermal mass and PCB heat spreading versus SMD packages like SMA or SMB. With a thermal resistance of ~40 °C/W on 1 cm² copper per lead (per Figure 12), it sustains higher average power dissipation during burst-mode operation than surface-mount equivalents rated for the same peak power.

Does BZW50-33B require derating above 25 °C ambient?

Yes-peak pulse power must be derated above 25 °C ambient per Figure 3. At 100 °C ambient, maximum PPP drops to ~3700 W for V_BR ≥ 36 V devices. Derating follows the curve in DS0662 Rev 8 page 3, and junction temperature must remain ≤175 °C under worst-case surge repetition and PCB layout conditions.