STMicroelectronics SM4T47CAY

Overview

SM4T47CAY from STMicroelectronics is a bidirectional automotive-grade transient voltage suppression (TVS) diode designed for ISO 7637-2 and ISO 10605 surge/ESD protection in 12 V vehicle power networks. It features a 47 V nominal breakdown voltage (V_BR = 44.4–49 V), 64.5 V maximum clamping voltage (V_CL) at 6.2 A (10/1000 µs), 400 W peak pulse power, and AEC-Q101 qualification for under-hood reliability.

For engineers reviewing the SM4T47CAY datasheet, SM4T47CAY pinout, SM4T47CAY application, or SM4T47CAY equivalent, key selection criteria include bidirectional polarity, low leakage (≤1 µA @ 85 °C), SMA package compatibility with IPC 7531 footprints, and compliance with ISO 7637-2 Pulse 1 (−150 V), Pulse 2a (+112 V), Pulse 3a (−200 V), and Pulse 3b (+150 V).

Technical Context

The SM4T47CAY employs planar junction technology to achieve stable high-temperature operation up to T_j = 150 °C and ultra-low reverse leakage-critical for long-term reliability in automotive infotainment and body control modules. Its bidirectional structure enables symmetric clamping for both positive and negative transients without external polarity management.

Clamping performance is defined by dynamic resistance (R_D = 1.30 Ω) and temperature coefficient α_T = 10.1 × 10⁻⁴/°C, enabling accurate V_CL prediction across operating junction temperatures using V_CL(T_j) = V_CL(25 °C) × [1 + α_T(T_j − 25)]. It meets UL94 V0 flammability and JEDEC-standard SMA mechanical outlines.

Key Specifications

Pinout & Package

SMA (DO-214AC) package: single-body, two-terminal surface-mount device with cathode band marking; dimensions per JEDEC MS-013 (A2 = 0.05–0.20 mm, b = 1.25–1.65 mm, D = 2.25–2.90 mm, E = 4.80–5.35 mm, E1 = 3.95–4.60 mm, L = 0.75–1.50 mm).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMBJ47CA and 1.5KE47CA, SM4T47CAY offers AEC-Q101 qualification, SMA footprint compatibility with high-density automotive PCBs, and lower clamping voltage (64.5 V vs. 77 V), making it optimal for protecting modern low-voltage automotive ICs where voltage headroom is constrained.

Availability

SM4T47CAY is available at Aetrix Electronics and suitable for automotive ECU power protection, infotainment interface ESD hardening, and ADAS camera supply stabilization requiring stable component supply across extended temperature and lifecycle requirements.

Supply support for SM4T47CAY 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 broad IP portfolio.

The SM4Txx series belongs to ST's automotive-qualified TVS portfolio, engineered specifically for robust transient immunity in 12 V vehicle electrical architectures per ISO 7637-2 and ISO 10605.

FAQ

What does the 'CAY' suffix indicate in SM4T47CAY?

The 'CAY' suffix denotes a bidirectional TVS diode in SMA (DO-214AC) package. 'C' specifies bidirectional polarity, 'A' indicates automotive grade (AEC-Q101 qualified), and 'Y' identifies the specific marking code (DBZY per Table 6). This distinguishes it from unidirectional 'AY' variants like SM4T47AY.

Can SM4T47CAY replace SM4T47AY in a circuit?

No-SM4T47CAY is bidirectional while SM4T47AY is unidirectional. Substituting them requires verifying circuit topology: unidirectional devices require correct anode/cathode orientation relative to DC bias, whereas bidirectional types protect AC or floating lines without polarity constraints. Reverse substitution may cause short-circuit or failed protection.

What is the maximum allowable printed circuit board copper area for optimal thermal performance?

Per Figure 12 in DS6927, thermal resistance R_th(j-a) drops from ~4.5 °C/W (no added copper) to ~1.5 °C/W with 3 cm² of 70 µm copper under each lead. ST recommends ≥2 cm² per pad on FR4 PCBs to maintain T_j ≤150 °C during repeated 400 W pulses.

Does SM4T47CAY meet ISO 16750-2 for automotive environmental testing?

SM4T47CAY is AEC-Q101 qualified and tested per ISO 7637-2 and ISO 10605, but ISO 16750-2 covers broader environmental stress (e.g., temperature cycling, humidity, corrosion). While its construction supports those conditions, formal ISO 16750-2 certification is not claimed in DS6927-designers should validate full environmental compliance at system level.