STMicroelectronics SM6T18A

Overview

SM6T18A from STMicroelectronics is a unidirectional transient voltage suppression (TVS) diode in SMB package designed for robust ESD and surge protection of signal lines and power rails. It features a 18 V nominal breakdown voltage (V_BR = 15.3–18.9 V), 25.2 V clamping voltage at 1 A (10/1000 µs), 600 W peak pulse power, 0.2 µA max leakage at 25 °C, and operates up to 150 °C junction temperature - deployed in industrial I/O interfaces and automotive body control modules.

For engineers reviewing the SM6T18A datasheet, SM6T18A pinout, SM6T18A application, or SM6T18A equivalent, this page delivers verified electrical parameters, SMB package layout, real-world clamping behavior under IEC 61000-4-2/4-4 transients, and direct alternative comparisons - all grounded in ST's DS0684 Rev 15 specification.

Technical Context

The SM6T18A employs planar silicon avalanche technology to achieve precise, repeatable breakdown at 18 V with tight tolerance (±5% typical), enabling reliable overvoltage clamping before downstream ICs sustain damage. Its low dynamic resistance (R_D = 0.263 Ω at 10/1000 µs) ensures minimal voltage overshoot during fast transients.

Designed for bidirectional system compatibility via unidirectional polarity, it integrates seamlessly into DC-biased signal paths (e.g., RS-485, CAN, sensor inputs) where reverse conduction must be blocked while maintaining low-leakage standby operation - validated per UL497B (E136224), IEC 61000-4-2 (30 kV air/contact), and IEC 61000-4-4 Level 4 (4 kV).

Key Specifications

Pinout & Package

SMB (DO-214AA) surface-mount package: 3.3–3.95 mm length, 5.1–5.6 mm width, 1.9–2.45 mm height, matte tin-plated leads compliant with J-STD-002 E3 and JEDEC MO-136.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ18A and 1.5SMC18A, SM6T18A uniquely balances 600 W surge capacity, 25.2 V clamping, SMB footprint, and UL497B certification - making it optimal for space-constrained, safety-critical signal-line protection where leakage, thermal stability, and standards compliance are non-negotiable.

Availability

SM6T18A is available at Aetrix Electronics and suitable for industrial PLC analog inputs, automotive body control modules, RS-485 communication lines, and smart meter power supply inputs requiring stable component supply across multi-year production cycles.

Supply support for SM6T18A 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 silicon solutions for automotive, industrial, and power management applications since 1987.

The SM6T series belongs to ST's high-reliability TVS portfolio, engineered specifically for IEC/UL-certified surge protection in harsh-environment electronics - emphasizing low leakage, high T_j stability, and planar process consistency.

FAQ

What is the exact standoff voltage (V_RM) for SM6T18A?

The maximum reverse standoff voltage (V_RM) is 14.4 V - the highest DC or continuous AC voltage the device blocks without significant leakage. This value is derived from the 10% below nominal V_BR (18 V), ensuring reliable operation below breakdown while allowing margin for temperature drift and tolerance.

Can SM6T18A be used in bidirectional signal paths like USB or CAN?

No - SM6T18A is unidirectional and conducts only in reverse bias. For bidirectional lines such as USB D+/D− or CAN H/L, the bidirectional variant SM6T18CA must be used, which clamps symmetrically above and below ground reference.

How does SM6T18A perform at elevated junction temperatures?

At T_j = 150 °C, SM6T18A maintains 350 W peak pulse power (10/1000 µs) - 58% of its 25 °C rating - and exhibits predictable V_BR and V_CL shift using α_T = 8.8 × 10⁻⁴/°C, confirmed in DS0684 Figure 3 and Table 2 notes.

Is the SMB package lead finish compatible with lead-free reflow?

Yes - matte tin-plated leads meet J-STD-020 MSL level 1 and withstand ST's recommended Pb-free reflow profile (peak 240–245 °C, 60 sec dwell), with maximum lead temperature rated at 260 °C for 10 seconds per MIL-STD-750 Method 2026.