STMicroelectronics SM4T47AY

Overview

SM4T47AY from STMicroelectronics is an AEC-Q101-qualified unidirectional automotive TVS diode in SMA package, designed to clamp transient surges up to 64.5 V (V_CL) at 6.2 A (I_PP, 10/1000 µs), with 400 W peak pulse power rating and 0.2 µA leakage at 25 °C. It protects CAN, LIN, and sensor supply lines in 12 V automotive systems against ISO 7637-2 Pulse 1 (−150 V), Pulse 2a (+112 V), and ISO 10605 ESD events.

For engineers reviewing the SM4T47AY datasheet, SM4T47AY pinout, SM4T47AY application, or SM4T47AY equivalent, this device is selected for high-reliability 12 V board-level surge protection where low leakage, 150 °C junction operation, and JEDEC-standard SMA footprint compatibility are required - especially in ADAS camera modules, body control units, and infotainment power rails.

Technical Context

The SM4T47AY uses planar silicon technology to achieve stable breakdown voltage (V_BR = 44.4–49.0 V) across temperature, with a positive temperature coefficient (α_T = 10⁻⁴/°C) enabling predictable clamping rise under thermal stress. Its dynamic resistance (R_D = 1.30 Ω) ensures low clamping overshoot during fast transients like 8/20 µs surges (I_PP = 27 A, V_CL = 84 V).

It complies fully with ISO 10605 (±30 kV air/contact discharge, C = 150/330 pF) and ISO 7637-2 (Pulse 1, 2a, 3a, 3b) for 12 V battery systems, and supports reflow soldering per IPC/JEDEC J-STD-020 with peak profile up to 245 °C.

Key Specifications

Pinout & Package

SMA package (DO-214AC): surface-mount, two-terminal, cathode-banded unidirectional configuration. Dimensions: D = 2.25–2.90 mm, E = 4.80–5.35 mm, L = 0.75–1.50 mm, weight = 72 mg. Complies with IPC 7531 footprint standards.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ47A and 1.5SMC47A, SM4T47AY delivers lower clamping voltage (64.5 V vs. ≥67 V), tighter V_BR distribution, and guaranteed AEC-Q101 qualification - making it optimal for next-generation automotive ECUs where signal integrity and qualification traceability are mandatory.

Availability

SM4T47AY is available at Aetrix Electronics and suitable for ADAS camera modules, CAN FD gateways, body control units, and infotainment USB power switches requiring stable component supply across automotive production lifecycles.

Supply support for SM4T47AY 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 vertical manufacturing and AEC-Q100/Q101 qualification infrastructure.

The SM4TxxAY series belongs to ST's automotive-grade transient voltage suppression portfolio, engineered specifically for robust 12 V board-level protection in harsh environments - emphasizing low leakage, high T_j, and full ISO 7637-2/10605 compliance.

FAQ

Is SM4T47AY bidirectional or unidirectional?

SM4T47AY is unidirectional: it clamps only positive transients relative to ground (anode grounded, cathode to protected line). Its marking "DUZY" and part suffix "AY" confirm unidirectional configuration per ST's ordering table. Bidirectional version is SM4T47CAY ("DBZY").

What is the maximum continuous reverse working voltage (V_RWM) for SM4T47AY?

V_RWM is 40 V - the maximum DC or RMS voltage that can be continuously applied without exceeding 1 µA leakage. This value is specified in Table 2 of DS6927 Rev 6 and aligns with its V_BR min of 44.4 V (10% margin above V_RWM).

Can SM4T47AY replace SMAJ47A in existing designs?

Yes, with verification: both use SMA package and share identical pinout and polarity. However, SM4T47AY offers lower V_CL (64.5 V vs. 67.0 V) and AEC-Q101 qualification - so replacement improves protection margin but requires validation of layout thermal relief and reflow profile compatibility.

Does SM4T47AY require derating at elevated ambient temperatures?

Yes: peak pulse power must be reduced above 25 °C ambient. Figure 3 in DS6927 shows PPP drops to ~320 W at 85 °C ambient (T_j = 125 °C assumed), based on thermal impedance and junction-to-ambient resistance. Layout copper area directly impacts achievable derating - see Figure 12 for R_th(j-a) vs. pad size.