STMicroelectronics SM15T27AY

Overview

SM15T27AY from STMicroelectronics is an AEC-Q101-qualified unidirectional automotive TVS diode in SMC package, designed to clamp transient surges up to 48.3 A (8/20 µs) with a clamping voltage of 37.5 V at 25 °C and 40 Ω dynamic resistance. It provides ISO 7637-2 Pulse 1 (−150 V), Pulse 2a (+112 V), Pulse 3a (−220 V), and Pulse 3b (+150 V) protection for 12 V battery systems, and meets IEC 61000-4-2 ±30 kV ESD immunity (150 pF/330 Ω and 330 pF/330 Ω).

For engineers reviewing the SM15T27AY datasheet, SM15T27AY pinout, SM15T27AY application, or SM15T27AY equivalent, this device is selected for high-reliability automotive power line surge suppression where low leakage (0.2 µA @ 25 °C), high junction temperature operation (up to +150 °C), and stable clamping under repeated transients are critical.

Technical Context

The SM15T27AY uses planar silicon technology to achieve low leakage current and high thermal stability across −55 °C to +150 °C junction temperature range. Its unidirectional configuration enables asymmetric clamping-forward conduction during negative transients and reverse avalanche clamping during positive overvoltage events on battery-fed lines.

It delivers 1500 W peak pulse power (10/1000 µs) at 25 °C, derating to 1250 W at T_j = 150 °C per Figure 3. The device complies with ISO 10605 (±30 kV contact/air), IEC 61000-4-4 Level 4 (±4 kV), and full ISO 7637-2 automotive surge test profiles-making it suitable for CAN, LIN, and sensor supply line protection in ECUs and body control modules.

Key Specifications

Pinout & Package

SM15T27AY is housed in an SMC (DO-214AB) surface-mount package with two terminals: Cathode (K) and Anode (A). The package measures 5.55–6.25 mm × 7.75–8.15 mm × 2.45 mm max height and features matte tin-plated leads compliant with J-STD-002, JESD 22-B102 E3, and IPC7531 footprint standards.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ24A and 1.5KE27A, SM15T27AY uniquely combines AEC-Q101 qualification, SMC surface-mount compatibility, 0.2 µA leakage, and full ISO 7637-2 Pulse 1–3b compliance-making it the sole choice for production automotive power line protection where reliability and regulatory traceability are mandatory.

Availability

SM15T27AY is available at Aetrix Electronics and suitable for automotive ECU power inputs, ADAS radar modules, body control units, and camera system power rails requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for SM15T27AY 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 automotive, industrial, and power management solutions with vertical manufacturing and rigorous quality certification.

SM15T27AY belongs to ST's automotive-grade TVS diode portfolio, engineered specifically for robust transient suppression in 12 V and 24 V vehicle networks-prioritizing AEC-Q101 reliability, ISO 7637-2 compliance, and thermal resilience in space-constrained SMC packages.

FAQ

What is the maximum clamping voltage of SM15T27AY under ISO 7637-2 Pulse 1 conditions?

The SM15T27AY clamps to ≤37.5 V at 10/1000 µs with 40 A peak current, and its dynamic resistance of 0.228 Ω ensures consistent clamping even under Pulse 1 (−150 V) stress. Measured V_CL remains within specification across −40 °C to +125 °C ambient, verified per DS6928 Rev 6 test data.

Can SM15T27AY replace bidirectional TVS diodes like SM15T27CAY in automotive applications?

No-SM15T27AY is unidirectional and only protects against positive transients on the cathode side; it cannot suppress negative-going surges on signal lines requiring symmetrical clamping. Bidirectional SM15T27CAY must be used for LIN/CAN data lines or AC-coupled sensors where polarity reversal occurs.

Does SM15T27AY require external heat sinking for 1500 W pulse handling?

No-its SMC package achieves R_th(j-a) ≈ 100 °C/W on standard FR4 PCB with 3.14 cm² copper area per lead (per Figure 12), and thermal impedance drops further with recommended footprint (Figure 18). At 1500 W for 1 ms, junction temperature rise stays within 150 °C limit without added heatsink.

How does SM15T27AY perform at elevated junction temperatures above 125 °C?

At T_j = 150 °C, SM15T27AY maintains 1250 W peak pulse power (10/1000 µs), and its V_BR shifts predictably per α_T = 9.6 × 10⁻⁴/°C (Table 2). Clamping voltage increases linearly with temperature, enabling accurate system-level margin analysis using Equation 2 in DS6928.