STMicroelectronics SMA6F8.5AY

Overview

SMA6F8.5AY from STMicroelectronics is an AEC-Q101-qualified unidirectional automotive TVS diode in SMA Flat package, designed to clamp transient overvoltages up to 14.4 V (10/1000 µs) at 41.7 A peak pulse current while maintaining low leakage (1 µA @ 85 °C) and operating up to 175 °C junction temperature. It delivers 600 W peak pulse power (10/1000 µs) and exceeds ISO 10605 ESD immunity (±30 kV contact/air) for robust protection of 12 V automotive power rails.

For engineers reviewing the SMA6F8.5AY datasheet, SMA6F8.5AY pinout, SMA6F8.5AY application, or SMA6F8.5AY equivalent, key selection criteria include clamping voltage at rated IPP, VRM standoff (8.5 V), thermal derating above 25 °C, and compatibility with ISO 7637-2 Pulse 1/2a/3a surge waveforms in battery-supplied ECUs.

Technical Context

This device uses planar silicon technology to achieve stable VBR (9.4–10.4 V), low dynamic resistance (0.096 Ω at 10/1000 µs), and high junction temperature capability (Tj max = 175 °C), enabling reliable operation in under-hood environments where thermal cycling and long-term stability are critical.

Its unidirectional configuration supports DC-biased lines such as automotive LIN bus, sensor supply rails, and body control module inputs, with clamping behavior defined by VCL–IPP relationship and validated against ISO 7637-2 pulses (Pulse 1: −150 V; Pulse 2a: +112 V; Pulse 3a/b: ±220 V/±150 V).

Key Specifications

Pinout & Package

The SMA6F8.5AY is housed in a flat, surface-mount SMA Flat package (JEDEC DO-214AC), measuring 2.90 mm × 5.35 mm × 1.10 mm (L × W × H), with matte tin-plated leads and IPC7531-compliant footprint. Its two-terminal construction supports automated placement and reflow soldering per J-STD-020 MSL Level 1 profile.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMA6F8.0AY and SMA6F9.0AY, the SMA6F8.5AY provides optimal balance for standard 12 V automotive systems: its 8.5 V VRM avoids false triggering during cold-crank dips (~6–7 V), while its 14.4 V clamping voltage protects common 16 V-rated LDOs and microcontrollers without excessive voltage margin loss.

Availability

SMA6F8.5AY is available at Aetrix Electronics and suitable for engine control units, LIN bus nodes, automotive camera modules, and body control module sensor interfaces requiring stable component supply across automotive production lifecycles.

Supply support for SMA6F8.5AY 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 broad manufacturing and R&D infrastructure.

The SMA6FY series belongs to ST's automotive-grade Transil TVS portfolio, engineered specifically to meet stringent ISO 7637-2 and ISO 10605 requirements for electronic control units in passenger vehicles and light commercial applications.

FAQ

What is the maximum clamping voltage of SMA6F8.5AY under a 10/1000 µs surge?

The maximum clamping voltage is 14.4 V at 41.7 A peak pulse current for a 10/1000 µs waveform, measured at T_amb = 25 °C. This value increases with junction temperature per the α_T coefficient (7.3 × 10⁻⁴/°C), reaching ~15.2 V at T_j = 125 °C based on datasheet Figure 5 interpolation.

Can SMA6F8.5AY be used in 24 V automotive systems?

No - its 8.5 V standoff voltage (VRM) is optimized for 12 V nominal systems. In 24 V applications, it would conduct continuously during normal operation due to battery voltage exceeding VRM. For 24 V rails, ST recommends SMA6F22AY (VRM = 22 V) or SMA6F24AY (VRM = 24 V), both qualified to the same AEC-Q101 and ISO standards.

How does the SMA Flat package improve thermal performance versus standard SMA?

The SMA Flat variant reduces package height to 1.10 mm and features optimized leadframe geometry, lowering thermal resistance junction-to-ambient (R_th(j-a)) by up to 30% compared to legacy SMA packages when mounted on 1 cm² copper pads. Figure 11 shows R_th(j-a) = 120 °C/W at 1 cm², enabling higher sustained power handling in compact layouts.

Is SMA6F8.5AY compatible with lead-free reflow processes?

Yes - it is qualified for lead-free soldering per J-STD-020 MSL Level 1, with a maximum peak reflow temperature of 245 °C and a 60-second liquidus duration. The matte tin plating ensures reliable wetting, and the recommended profile (Figure 24) specifies ramp rates ≤3 °C/s and cooling ≥2 °C/s to prevent delamination or voiding.