STMicroelectronics SM50T56AY

Overview

SM50T56AY from STMicroelectronics is an AEC-Q101-qualified unidirectional automotive TVS diode in SMC package, designed to clamp transient overvoltages up to 77.4 V (10/1000 µs) with 5000 W peak pulse power and 286 A peak pulse current. It features 56 V nominal breakdown voltage, 0.2 µA max leakage at 25 °C, and operates up to 175 °C junction temperature-deployed in engine control units and battery management systems for ISO 7637-2 Pulse 1/2a/3a/3b surge suppression.

For engineers reviewing the SM50T56AY datasheet, SM50T56AY pinout, SM50T56AY application, or SM50T56AY equivalent, key selection criteria include clamping voltage (77.4 V @ 10/1000 µs), dynamic resistance (92.8 mΩ), thermal robustness (Tj max = 175 °C), and compliance with ISO 10605 (±30 kV ESD), IEC 61000-4-2 (±30 kV), and ISO 7637-2 (Pulse 1: −150 V).

Technical Context

This unidirectional TVS diode uses planar silicon technology to achieve low leakage (0.2 µA at VRM = 48 V) and stable VBR drift (αT = 10.3 × 10⁻⁴ /°C). Its clamping behavior follows VCL = VBRmax + RD × IPP, enabling predictable overvoltage protection during fast transients like ISO 7637-2 Pulse 3b (+150 V).

The device meets automotive-grade reliability requirements: MSL Level 1 per J-STD-020, JEDEC-registered SMC outline, matte tin lead finish, and full qualification to AEC-Q101. It supports high-temperature PCB layouts with thermal impedance of 100 °C/W (single pulse, FR4, 70 µm Cu) and load dump immunity up to 87 V (ISO 16750-2 Test B).

Key Specifications

Pinout & Package

SM50T56AY is housed in a JEDEC-registered SMC (DO-214AB) surface-mount package with matte tin-plated leads. The package measures 5.55–6.25 mm (D) × 7.75–8.15 mm (E) × 1.90–2.45 mm (A1) and weighs 264 mg.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ56A and 1.5KE56A, SM50T56AY delivers 12.5× higher peak pulse power (5000 W vs. 400 W/1500 W), AEC-Q101 qualification, SMC surface-mount compatibility, and lower clamping voltage (77.4 V vs. ≥93.6 V), making it the sole choice for production automotive power rail protection.

Availability

SM50T56AY is available at Aetrix Electronics and suitable for engine control units, body control modules, ADAS camera power supplies, and electric power steering systems requiring stable component supply across extended temperature and high-reliability automotive programs.

Supply support for SM50T56AY 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, designing and manufacturing microcontrollers, power devices, sensors, and analog ICs for automotive, industrial, and consumer markets.

SM50T56AY belongs to the SM50TY series of automotive-grade TVS diodes engineered specifically for ISO 7637-2 and ISO 10605 compliance in harsh-temperature vehicle subsystems-including powertrain, chassis, and ADAS domains.

FAQ

What is the maximum clamping voltage of SM50T56AY under a 10/1000 µs surge?

The maximum clamping voltage is 77.4 V at 286 A for a 10/1000 µs waveform, measured at T_j = 25 °C. This value increases with junction temperature per α_T = 10.3 × 10⁻⁴ /°C, reaching ~82.5 V at 150 °C using the formula V_CL(T_j) = V_CL(25 °C) × [1 + α_T × (T_j − 25)].

Is SM50T56AY suitable for bidirectional signal line protection?

No-SM50T56AY is unidirectional and intended for DC power rail protection (e.g., 12 V battery lines). For bidirectional data lines like CAN or LIN, ST offers the complementary SM50T56CAY variant, which provides symmetrical clamping for both polarities and is marked with a cathode bar distinction.

How does SM50T56AY perform under ISO 7637-2 Pulse 1 (−150 V)?

Per Figure 13 in DS13895, SM50T56AY clamps Pulse 1 (−150 V, 50 Ω source, 12 V battery) to ≤−75 V at the protected node, limiting energy dissipation to within its 5000 W rating. Its low dynamic resistance (92.8 mΩ) ensures rapid response and prevents voltage overshoot beyond system-level tolerances.

What reflow profile should be used for SM50T56AY soldering?

ST recommends the J-STD-020-compliant reflow profile with peak temperature of 240–245 °C for ≤3 seconds, ramp-up rate ≤3 °C/s, and time above 210 °C limited to 60–90 seconds. The device is MSL Level 1-no dry pack or baking required prior to assembly.