STMicroelectronics SM15T33AY

Overview

SM15T33AY from STMicroelectronics is a unidirectional automotive-grade transient voltage suppressor (TVS) diode in SMC package, designed for ISO 7637-2 pulse protection in 12 V vehicle systems. It features a 33 V nominal breakdown voltage (V_BR = 28.2–34.7 V), 45.7 V clamping voltage at 169 A (8/20 µs), 1500 W peak pulse power (10/1000 µs), and AEC-Q101 qualification for under-hood applications including engine control units and body electronics.

For engineers reviewing the SM15T33AY datasheet, SM15T33AY pinout, SM15T33AY application, or SM15T33AY equivalent, key selection criteria include clamping performance at 169 A surge current, low leakage (<0.2 µA @ 25 °C), junction temperature capability up to +150 °C, and compliance with ISO 10605 (±30 kV ESD) and ISO 7637-2 (Pulse 1/2a/3a/3b).

Technical Context

This TVS operates as a unidirectional clamping device in reverse-biased configuration, leveraging planar silicon technology to achieve stable V_BR drift (α_T = 9.8 × 10⁻⁴/°C) and low dynamic resistance (R_D = 0.333 Ω). Its design targets fast response to sub-microsecond transients while maintaining <1 µA leakage at 85 °C ambient.

The device meets stringent automotive reliability requirements: UL94 V0 flammability rating, J-STD-020 MSL Level 1, and JEDEC-registered SMC outline. It is optimized for PCB mounting on FR4 with 70 µm copper, delivering R_th(j-a) ≈ 100 °C/W with recommended 3.14 cm² copper area per lead.

Key Specifications

Pinout & Package

SM15T33AY uses the standard SMC (DO-214AB) package: molded epoxy body, matte tin-plated leads, 2-terminal unidirectional configuration. Dimensions: L = 0.75–1.50 mm, D = 5.55–6.25 mm, E = 7.75–8.15 mm, E1 = 6.60–7.15 mm, b = 2.90–3.20 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ33A and 1.5KE33A, SM15T33AY delivers automotive-grade reliability in SMT format with superior clamping (45.7 V vs. 53.3 V), lower leakage (0.2 µA vs. 5 µA), and validated AEC-Q101 performance-critical for functional safety-critical power domains.

Availability

SM15T33AY is available at Aetrix Electronics and suitable for engine control units, body control modules, ADAS camera power supplies, and CAN bus physical layer protection requiring stable component supply across automotive production lifecycles.

Supply support for SM15T33AY 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, specializing in automotive, industrial, and power management solutions with over 45 years of analog and protection device expertise.

The SM15TxxAY series belongs to ST's automotive TVS portfolio, engineered specifically for robust transient suppression in 12 V/24 V vehicle networks-prioritizing low clamping, high-temperature stability, and AEC-Q101 compliance over generic surge ratings.

FAQ

What is the maximum clamping voltage of SM15T33AY under a 169 A 8/20 µs surge?

The maximum clamping voltage (V_CL) is 45.7 V at 169 A for an 8/20 µs waveform, measured at T_amb = 25 °C. This value increases with junction temperature at a rate defined by α_T = 9.8 × 10⁻⁴/°C, reaching approximately 48.2 V at T_j = 125 °C per the V_CL vs. T_j formula in DS6928.

Is SM15T33AY compatible with lead-free reflow soldering processes?

Yes-SM15T33AY uses matte tin-plated leads compliant with J-STD-020 MSL Level 1 and supports ST's recommended reflow profile: peak temperature 240–245 °C for 60–90 seconds, ramp rates ≤3 °C/s, and cooling rate ≥2 °C/s. The package withstands up to 260 °C for 10 s during hand soldering.

How does SM15T33AY differ from the bidirectional SM15T33CAY variant?

SM15T33AY is unidirectional (anode-cathode polarity), intended for DC line protection like power rails; SM15T33CAY is bidirectional (symmetrical V_BR), used for AC or differential signal lines such as LIN or USB. Their V_BR, V_CL, and I_PP values are identical, but CAY has dual avalanche paths and different marking (BETY vs. METY).

Can SM15T33AY protect against ISO 7637-2 Pulse 1 (load dump) in a 12 V system?

Yes-it is explicitly rated for ISO 7637-2 Pulse 1 (V_S = −150 V) and tested per the standard. With its 1500 W peak pulse power rating and 45.7 V clamping, it limits induced voltage on protected lines to safe levels during sustained load dump events, provided layout follows ST's recommended copper area (≥3.14 cm² per lead) for thermal management.