STMicroelectronics SMA4F28A

Overview

SMA4F28A from STMicroelectronics is a unidirectional 400 W transient voltage suppression (TVS) diode designed for robust ESD and surge protection in DC power rails and signal lines. It features a 28 V stand-off voltage (VRM), 31.1–34.3 V breakdown voltage (VBR), 45.4 V clamping voltage (VCL) at 8.8 A (10/1000 µs), and operates up to 175 °C junction temperature - ideal for automotive body control modules and industrial I/O interfaces exposed to IEC 61000-4-2 level 4 surges.

For engineers reviewing the SMA4F28A datasheet, SMA4F28A pinout, SMA4F28A application, or SMA4F28A equivalent, key selection criteria include clamping performance under 8/20 µs surges (59 V @ 39 A), low leakage (≤1 µA at 85 °C), dynamic resistance (0.633 Ω), and compatibility with high-reliability reflow profiles per J-STD-020 MSL level 1.

Technical Context

The SMA4F28A employs planar silicon avalanche technology to deliver precise, repeatable clamping with minimal capacitance and leakage. Its unidirectional configuration enables asymmetric protection on positive-rail applications without reverse conduction path concerns.

It is characterized by a voltage temperature coefficient αT of 9.8 × 10⁻⁴ /°C, enabling predictable VBR and VCL drift over temperature, and supports high-power pulse handling up to 200 W at Tj = 175 °C - critical for under-hood automotive electronics and industrial PLC inputs.

Key Specifications

Pinout & Package

The SMA4F28A is housed in an industry-standard SMA (DO-214AC) flat package with matte tin-plated leads, compliant with IPC7531 footprint and JEDEC MO-136AA outline. Dimensions: D = 2.25–2.90 mm, E = 5.00–5.35 mm, E1 = 3.95–4.60 mm, L = 0.75–1.20 mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar transient suppression applications.

Compared with SMAJ28A and SMBJ28A, the SMA4F28A offers identical clamping performance in a smaller SMA footprint, superior thermal robustness at 175 °C, and tighter VBR tolerance - making it optimal for space-constrained, high-temperature automotive and industrial designs.

Availability

SMA4F28A is available at Aetrix Electronics and suitable for automotive body control modules, industrial PLC digital inputs, telecom power supply inputs, and smart meter communication interfaces requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for SMA4F28A 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 capabilities and broad IP portfolio.

The SMA4F Transil series targets high-reliability transient suppression in harsh-environment applications - engineered for low leakage, high junction temperature operation, and IEC/ISO-compliant surge immunity in automotive and industrial systems.

FAQ

What is the maximum clamping voltage of SMA4F28A under an 8/20 µs surge?

The SMA4F28A clamps to 59 V at 39 A for an 8/20 µs waveform, as specified in Table 2 of DS12542 Rev 1. This value is measured at T_amb = 25 °C and represents the peak voltage imposed on the protected circuit during standardized lightning-surge testing.

Can SMA4F28A be used in bidirectional configurations?

No - SMA4F28A is unidirectional only, with cathode marking indicating polarity-sensitive placement. For bidirectional protection, ST offers the SMA4F28CA variant; using SMA4F28A in reverse-biased mode risks permanent breakdown due to lack of symmetric avalanche structure.

Does SMA4F28A require derating at elevated ambient temperatures?

Yes - while rated for T_j up to 175 °C, its peak pulse power must be derated above 25 °C ambient. Figure 3 shows P_pp drops to ~200 W at T_j = 175 °C for 10/1000 µs pulses; design margins must account for thermal resistance and copper area per Figure 11.

Is SMA4F28A compliant with automotive AEC-Q200 stress testing?

No - SMA4F28A is not AEC-Q200 qualified. It meets IEC 61000-4-2, UL94 V0, and J-STD-020 MSL level 1, but lacks the extended temperature cycling, humidity bias, and mechanical shock validation required for automotive qualification. For AEC-Q200, consider ST's Automotive-grade SMxJ series.