STMicroelectronics SMBJ15A-TR

Overview

SMBJ15A-TR from STMicroelectronics is a unidirectional transient voltage suppression (TVS) diode designed for primary-level surge protection on DC power rails and signal lines. It features a 15 V standoff voltage (VRM), 24.4 V clamping voltage at 25.1 A (10/1000 µs), 600 W peak pulse power rating, and operates up to 150 °C junction temperature - deployed in industrial power supplies and automotive body control modules to safeguard MOSFETs and microcontrollers against IEC 61000-4-4 level 4 surges.

For engineers reviewing the SMBJ15A-TR datasheet, SMBJ15A-TR pinout, SMBJ15A-TR application, or SMBJ15A-TR equivalent, key selection criteria include clamping voltage margin vs. protected IC V_DS/V_CC, leakage current at elevated temperature, thermal resistance under PCB copper constraints, and UL497B recognition for isolated loop compliance.

Technical Context

This TVS diode uses planar silicon junction technology to achieve low leakage (0.2 µA at 25 °C, 1 µA at 85 °C) and stable clamping performance across its −55 °C to +150 °C operating junction range. Its unidirectional configuration provides forward conduction path during negative transients while blocking reverse DC bias up to 15 V.

The device delivers 24.4 V clamping at 25.1 A (10/1000 µs) with dynamic resistance of 0.236 Ω, enabling fast response (<1 ns) and predictable voltage limiting during ESD (IEC 61000-4-2, ±30 kV contact/air) and surge events (IEC 61000-4-4, 4 kV). Its SMB package supports IPC7531-compliant footprint and JEDEC-registered outline.

Key Specifications

Pinout & Package

Supplied in the industry-standard SMB (DO-214AA) surface-mount package, measuring 3.30–3.95 mm × 5.10–5.60 mm × 1.90–2.45 mm (L × W × H), with matte tin-plated leads compliant with J-STD-020 MSL Level 1 and JESD 22-B102 E3 solderability standards.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMBJ15CA-TR, SMBJ15A-TR offers tighter unidirectional clamping and lower capacitance for DC rail protection; versus SMAJ15A-TR, it delivers 50% higher surge energy handling and 3.3 V lower clamping - critical for 24 V systems with narrow voltage margins.

Availability

SMBJ15A-TR is available at Aetrix Electronics and suitable for industrial power supplies, automotive body control modules, telecom interface isolation, and smart meter auxiliary supplies requiring stable component supply across multi-year production cycles.

Supply support for SMBJ15A-TR 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 intelligent power, sensing, and control solutions for automotive, industrial, and consumer markets.

The SMBJ series belongs to ST's high-reliability TVS portfolio, engineered specifically for robust transient suppression in harsh-environment applications where long-term stability, low leakage, and agency-certified safety are non-negotiable.

FAQ

What is the maximum allowable PCB copper area under each SMBJ15A-TR lead to achieve R_th(j-a) ≤ 40 °C/W?

Per Figure 12 in DS1283 Rev 14, a total copper area of ≥2.5 cm² (1.25 cm² per lead) on FR4 board with 70 µm Cu thickness achieves R_th(j-a) ≈ 40 °C/W for single-pulse conditions. This enables sustained 600 W surge dissipation without exceeding 150 °C junction temperature when ambient is ≤85 °C.

Does SMBJ15A-TR meet IEC 61000-4-2 level 4 for both contact and air discharge?

Yes - SMBJ15A-TR exceeds IEC 61000-4-2 level 4 with 30 kV contact and 30 kV air discharge ratings (C = 150 pF, R = 330 Ω), verified per Table 1 and Figure 9 in DS1283. Its low leakage and planar junction ensure repeatable performance across >10,000 ESD strikes without parameter shift.

How does SMBJ15A-TR's clamping voltage change at 125 °C junction temperature?

Using α_T = 8.8 × 10⁻⁴ /°C from Table 2, V_CL at 125 °C = 24.4 V × [1 + 0.00088 × (125 − 25)] = 26.5 V. This 8.6% increase remains within safe margin for 36 V-rated ICs and is fully characterized in ST's thermal derating curves (Figure 3).

Can SMBJ15A-TR be used in parallel to increase surge current handling?

No - parallel connection is not recommended due to mismatch in V_BR (±0.9 V tolerance) causing current imbalance. At 25.1 A total, one device may conduct >80% of surge current, risking thermal runaway. Use a single higher-power device (e.g., 1.5KE15A) or staged protection instead.