STMicroelectronics SM15T68AY

Overview

SM15T68AY from STMicroelectronics is a unidirectional automotive-grade transient voltage suppression (TVS) diode in SMC package, designed for ISO 7637-2 pulse protection in 12 V/24 V vehicle systems. It features a 68 V breakdown voltage (V_BR = 68 V), 92 V clamping voltage (V_CL) at 16.3 A (10/1000 µs), 1500 W peak pulse power, and AEC-Q101 qualification for under-hood reliability.

For engineers reviewing the SM15T68AY datasheet, SM15T68AY pinout, SM15T68AY application, or SM15T68AY equivalent, key selection criteria include clamping performance at 16.3 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 diode uses planar silicon technology to achieve low dynamic resistance (R_D = 1.26 Ω) and stable V_BR over temperature (α_T = 10.4 × 10⁻⁴/°C). Its unidirectional configuration provides asymmetric clamping-forward conduction only during negative transients-making it suitable for protecting positive-rail electronics against load dump and inductive switching events.

The device operates across −55 °C to +150 °C junction temperature, with thermal impedance optimized for FR4 PCBs using the IPC7531-recommended footprint. Its 1.26 Ω dynamic resistance ensures predictable V_CL rise under surge: V_CL(max) = V_BR(max) + R_D × I_PP, validated per IEC 61000-4-4 Level 4 (4 kV) and ISO 10605 test conditions.

Key Specifications

Pinout & Package

SM15T68AY is housed in an SMC (DO-214AB) plastic package with two terminals: Cathode (marked end) and Anode. The package meets JEDEC registered outline standards and supports reflow soldering per J-STD-020 MSL Level 1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ68A and 1.5KE68A, SM15T68AY delivers 3.75× higher peak power, 18–20 V lower clamping at rated current, AEC-Q101 qualification, and SMC packaging optimized for automated manufacturing and thermal performance in automotive environments.

Availability

SM15T68AY is available at Aetrix Electronics and suitable for engine control units, LIN bus nodes, body control modules, and ADAS camera power supplies requiring stable component supply across automotive production lifecycles.

Supply support for SM15T68AY 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 discrete technologies with vertical manufacturing capabilities.

The SM15TxxAY series belongs to ST's automotive-grade TVS portfolio, engineered specifically for robust transient suppression in 12 V/24 V vehicle electrical systems per ISO 7637-2 and ISO 10605 standards.

FAQ

What is the maximum clamping voltage of SM15T68AY under a 10/1000 µs surge?

The maximum clamping voltage is 92 V at 16.3 A for a 10/1000 µs waveform, measured at T_amb = 25 °C. This value increases with junction temperature per the coefficient α_T = 10.4 × 10⁻⁴/°C, reaching ~98 V at T_j = 125 °C using V_CL(T_j) = V_CL(25 °C) × [1 + α_T × (T_j − 25)].

Is SM15T68AY suitable for protecting CAN FD interfaces?

No - SM15T68AY is not recommended for CAN FD data lines due to its 100+ pF junction capacitance at low reverse bias, which would distort >2 Mbps signaling. It is intended for power rail and low-speed signal protection (e.g., LIN, analog sensors), not high-speed differential buses.

How does the SMC package of SM15T68AY improve thermal performance versus SMA?

The SMC package offers 30% larger copper pad area and 25% lower R_th(j-a) than SMA when mounted on IPC7531-compliant FR4, enabling 1250 W surge handling at T_j = 150 °C. Its 7.75–8.15 mm body width improves mechanical stability during thermal cycling versus smaller SMA outlines.

Does SM15T68AY require external series impedance for optimal protection?

Yes - a series ferrite bead or small resistor (1–10 Ω) is recommended between the TVS and protected IC to limit di/dt and prevent oscillation during fast transients. This improves clamping effectiveness for 8/20 µs surges and reduces parasitic ringing that could compromise downstream logic thresholds.