STMicroelectronics SM50T68AY

Overview

SM50T68AY from STMicroelectronics is an AEC-Q101-qualified unidirectional automotive TVS diode in SMC package, designed to clamp transient surges up to 93.6 V (clamping voltage at 10/1000 µs) with 419 A peak pulse current and 5000 W peak power (10/1000 µs). It features 0.2 µA max leakage at 25 °C, 175 °C max junction temperature, and is optimized for ISO 7637-2 Pulse 1/2a/3a/3b and ISO 10605 ESD protection in 12 V/24 V automotive power nets.

For engineers reviewing the SM50T68AY datasheet, SM50T68AY pinout, SM50T68AY application, or SM50T68AY equivalent, key selection criteria include clamping voltage under 10/1000 µs surge (93.6 V), low dynamic resistance (130 mΩ), unidirectional polarity, SMC package thermal performance, and compliance with ISO 16750 load-dump immunity requirements.

Technical Context

This TVS diode uses planar silicon technology to achieve stable breakdown behavior across -55 °C to +175 °C operating junction temperature, with temperature coefficient α_T = 10.4 × 10⁻⁴/°C for V_BR and V_CL. Its unidirectional configuration enables asymmetric clamping-forward conduction only during negative transients-making it suitable for battery-line protection where reverse polarity is not expected.

The device meets IEC 61000-4-2 (±30 kV air/contact), ISO 10605 (±30 kV), and ISO 7637-2 (Pulse 1: −150 V; Pulse 2a: +112 V; Pulse 3a: −220 V; Pulse 3b: +150 V) standards. Its 130 mΩ dynamic resistance ensures minimal voltage overshoot during fast 8/20 µs surges (121 A clamping at 419 A IPP), critical for safeguarding downstream DC-DC controllers and CAN transceivers.

Key Specifications

Pinout & Package

SM50T68AY is housed in a JEDEC-registered SMC (DO-214AB) surface-mount package with matte tin-plated leads. The package measures 7.75–8.15 mm × 5.55–6.25 mm × 2.45 mm max height and supports reflow per J-STD-020 MSL Level 1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ68A and SMA6J68A, SM50T68AY offers tighter VBR tolerance (±5% vs ±10%), lower clamping voltage (93.6 V vs ≥107 V), lower dynamic resistance (130 mΩ vs ≥175 mΩ), and explicit ISO 7637-2 Pulse 5b validation-enabling drop-in compliance in Tier 1 ECU designs without requalification.

Availability

SM50T68AY is available at Aetrix Electronics and suitable for engine control units, body control modules, ADAS camera interfaces, and electric power steering systems requiring stable component supply across automotive production lifecycles.

Supply support for SM50T68AY 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.

SM50T68AY belongs to the SM50TY series of planar automotive TVS diodes, engineered specifically for robust ISO 7637-2 and ISO 10605 compliance in harsh-temperature vehicle environments.

FAQ

What is the maximum clamping voltage of SM50T68AY under a 10/1000 µs surge?

The maximum clamping voltage is 93.6 V at 419 A peak pulse current for a 10/1000 µs waveform, measured at T_j = 25 °C. This value increases with junction temperature per α_T = 10.4 × 10⁻⁴/°C, reaching approximately 101.5 V at T_j = 125 °C.

Is SM50T68AY suitable for bidirectional signal line protection?

No. SM50T68AY is unidirectional (indicated by "AY" suffix) and conducts only in reverse bias. For bidirectional protection-such as on CAN_H/CAN_L lines-use SM50T68CAY, which features symmetrical clamping for both polarities and identical V_BR/V_CL ratings in either direction.

How does the 130 mΩ dynamic resistance impact circuit protection performance?

The 130 mΩ dynamic resistance directly determines voltage overshoot during fast transients: ΔV = R_D × I_PP. At 419 A, this contributes 54.5 V of resistive drop-critical for keeping total clamped voltage below 93.6 V. Lower R_D than alternatives (e.g., 175–180 mΩ) improves margin for 60 V-rated downstream ICs.

Can SM50T68AY be used in 24 V commercial vehicle applications?

Yes. With V_RM = 58 V and V_BR starting at 64.6 V, it provides adequate margin above 24 V nominal systems (including 28 V alternator regulation). Its 175 °C T_jmax and ISO 7637-2 Pulse 5b validation up to 87 V make it suitable for heavy-duty truck ECUs and off-highway equipment.