STMicroelectronics SM30T28AY

Overview

SM30T28AY from STMicroelectronics is an AEC-Q101-qualified unidirectional transient voltage suppression (TVS) diode in SMC package, designed for automotive power-line surge protection. It delivers 3000 W peak pulse power (10/1000 µs), clamps at 38.9 V (max) under 77 A surge current, and operates up to 175 °C junction temperature - enabling robust protection of 12 V/24 V battery-fed ECUs against ISO 7637-2 Pulse 1 (−150 V), Pulse 2a (+112 V), Pulse 3a (−220 V), and Pulse 3b (+150 V).

For engineers reviewing the SM30T28AY datasheet, SM30T28AY pinout, SM30T28AY application, or SM30T28AY equivalent, this device supports high-reliability automotive circuit protection where low leakage (0.2 µA @ 25 °C), tight V_BR tolerance (26.7–29.5 V), and stable dynamic resistance (31.1 mΩ) are critical for ESD immunity (±30 kV contact/air per ISO 10605) and long-term thermal stability.

Technical Context

The SM30T28AY employs planar silicon avalanche technology to achieve precise breakdown voltage control and minimal parameter drift over temperature (α_T = 10 × 10⁻⁴/°C). Its unidirectional configuration provides asymmetric clamping optimized for DC-biased automotive bus lines, with reverse stand-off voltage (V_RWM) of 24 V and guaranteed breakdown at 26.7 V (min) at 1 mA.

Thermal performance is validated per JEDEC JESD51-14 standards, supporting continuous operation at T_j = 175 °C and peak pulse dissipation up to 3000 W at ambient-start conditions. The device meets IEC 61000-4-4 Level 4 (4 kV), ISO 10605 (±30 kV), and ISO 7637-2 compliance without external biasing or auxiliary components.

Key Specifications

Pinout & Package

SM30T28AY is housed in a JEDEC-standard SMC (DO-214AB) surface-mount package with matte tin-plated leads, compatible with IPC-7531 footprint and reflow profiles per J-STD-020 MSL Level 1. The two-terminal device has no polarity marking on cathode side per standard SMC orientation; cathode is identified by band marking (3AAEY) per Table 6.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ28A and TPSMD28A, SM30T28AY offers superior surge robustness (3000 W vs. 400 W / 3300 W), tighter clamping (38.9 V vs. 48.4 V / 42.5 V), and lowest dynamic resistance (31.1 mΩ), making it the optimal choice for safety-critical automotive power rails requiring zero-failure field performance.

Availability

SM30T28AY is available at Aetrix Electronics and suitable for engine control units, body control modules, ADAS camera power supplies, and electric power steering systems requiring stable component supply across extended automotive product lifecycles (15+ years).

Supply support for SM30T28AY 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, delivering intelligent power, analog, MEMS, and microcontroller solutions for automotive, industrial, and consumer markets.

SM30T28AY belongs to the SM30TY series of automotive-grade TVS diodes engineered specifically for ISO 7637-2 and ISO 10605 compliance in harsh-temperature vehicle subsystems - emphasizing low leakage, high junction temperature capability, and planar process consistency.

FAQ

What is the maximum clamping voltage of SM30T28AY under a 10/1000 µs surge?

The maximum clamping voltage (V_CL) is 38.9 V at 77 A peak pulse current for a 10/1000 µs waveform, measured at T_amb = 25 °C. This value increases linearly with junction temperature at α_T = 10 × 10⁻⁴/°C, reaching approximately 41.2 V at T_j = 150 °C per the V_CL vs. T_j formula in DS8599 Section 1.1.

Is SM30T28AY suitable for bidirectional signal line protection?

No - SM30T28AY is a unidirectional TVS diode intended for DC-biased power rails (e.g., battery inputs, DC-DC converter inputs). For bidirectional signal protection such as CAN or LIN buses, the pin-compatible SM30T28CAY variant must be used, which provides symmetrical clamping for both polarities.

How does the 0.2 µA leakage current impact battery-powered automotive modules?

At 0.2 µA maximum reverse leakage (measured at V_RWM = 24 V and 25 °C), SM30T28AY contributes negligible drain to always-on vehicle subsystems - less than 1.7 mAh/year per device. This enables multi-year quiescent current budgets in telematics control units and remote keyless entry receivers without compromising ESD robustness.

What PCB layout practices maximize thermal performance for SM30T28AY?

To maintain T_j ≤ 175 °C under repeated surges, use the recommended IPC-7531-compliant footprint with ≥3.14 cm² copper area under each lead (per Figure 12), 70 µm Cu thickness, and FR4 substrate. Avoid thermal isolation; connect both pads directly to internal ground/power planes using ≥4 thermal vias per pad (0.3 mm diameter, 0.8 mm pitch) to reduce R_th(j-a) to ≤45 °C/W.