STMicroelectronics SM6T27A

Overview

SM6T27A from STMicroelectronics is a unidirectional 600 W transient voltage suppression diode in SMB package, designed for IEC 61000-4-2 ESD (30 kV air/contact) and IEC 61000-4-4 surge (4 kV) protection of signal lines and power rails in industrial SMPS and high-reliability equipment. It features 27 V breakdown voltage (V_BR = 23.1–28.4 V), 37.5 V clamping voltage at 16 A (10/1000 µs), and low leakage (0.2 µA @ 25 °C).

For engineers reviewing the SM6T27A datasheet, SM6T27A pinout, SM6T27A application, or SM6T27A equivalent, this page delivers verified electrical parameters, SMB package layout, real-world clamping behavior under 10/1000 µs and 8/20 µs transients, thermal derating curves up to 150 °C junction temperature, and direct alternatives with documented V_BR, V_CL, and R_D differences.

Technical Context

The SM6T27A employs planar silicon junction technology optimized for low leakage and stable operation up to T_j = 150 °C, enabling long-term reliability in high-temperature SMPS and industrial control environments. Its dynamic resistance (R_D = 0.569 Ω) and fast response time ensure precise clamping during sub-microsecond ESD events.

It operates as a unidirectional shunt protector: reverse-biased during normal operation (I_R ≤ 0.2 µA at V_RM = 23.1 V), then avalanches into low-impedance conduction when V_PP exceeds V_BR, limiting voltage across protected circuitry to ≤37.5 V at 16 A peak pulse current.

Key Specifications

Pinout & Package

The SM6T27A is housed in an SMB (DO-214AA) surface-mount package measuring 3.30–3.95 mm × 5.10–5.60 mm × 2.45 mm max height, with matte tin-plated leads compliant with J-STD-002 and IPC7531 footprint standards.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SM6T27A, SMBJ27A and P6SMB27A offer higher V_BR and V_CL, reducing false triggering in noisy 24 V systems but increasing risk of overvoltage damage to downstream ICs; SM6T27A's lower V_CL and R_D provide superior protection for sensitive analog and logic circuits at the cost of tighter V_BR tolerance.

Availability

SM6T27A is available at Aetrix Electronics and suitable for industrial motor drives, telecom power supplies, automotive body control modules, and industrial PLC I/O modules requiring stable component supply across multi-year production cycles.

Supply support for SM6T27A 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 microcontrollers, power devices, sensors, and analog ICs for industrial, automotive, and consumer markets.

The SM6T series belongs to ST's transient protection portfolio, engineered specifically for high-reliability ESD and surge immunity in industrial power conversion and harsh-environment signal conditioning applications.

FAQ

What is the maximum clamping voltage of SM6T27A under a 10/1000 µs surge?

The SM6T27A clamps to a maximum of 37.5 V at 16 A peak pulse current under 10/1000 µs waveform, as specified in Table 2 of DS0684 Rev 15. This value is measured at T_amb = 25 °C and remains valid up to T_j = 150 °C using the temperature coefficient α_T = 9.6 × 10⁻⁴/°C.

Is SM6T27A suitable for bidirectional signal lines like RS-485?

No - SM6T27A is unidirectional and must be used with cathode toward the protected line and anode to ground. For bidirectional lines, the SM6T27CA variant is required, which provides symmetrical clamping in both polarities and is marked with 'MP' on the device body per Table 6.

How does SM6T27A compare to SMAJ27A in terms of surge capability?

SM6T27A delivers 600 W (10/1000 µs) vs. SMAJ27A's 400 W, and supports higher junction temperature (150 °C vs. 125 °C). Its lower R_D (0.569 Ω vs. ~0.9 Ω) yields tighter clamping, making it preferable for protecting low-voltage logic and precision analog circuits in thermally demanding applications.

What PCB footprint standard does SM6T27A follow?

SM6T27A uses the JEDEC registered SMB (DO-214AA) outline with IPC7531-compliant pad dimensions: 1.62 mm × 2.60 mm pads spaced 5.84 mm center-to-center, as shown in Figure 14 of DS0684. Thermal relief and copper pour under the device improve power dissipation during repetitive surges.