STMicroelectronics SMA4F22A

Overview

SMA4F22A from STMicroelectronics is a unidirectional 400 W transient voltage suppression (TVS) diode designed for primary-level surge protection in DC power rails and signal lines. It features a 22 V stand-off voltage (VRM), 35.5 V clamping voltage at 11.2 A (10/1000 µs), 0.2 µA max leakage at 25 °C, and operates up to 175 °C junction temperature-enabling robust protection in automotive body electronics and industrial power supplies.

For engineers reviewing the SMA4F22A datasheet, SMA4F22A pinout, SMA4F22A application, or SMA4F22A equivalent, key selection criteria include clamping performance under IEC 61000-4-2 Level 4 (±25 kV contact / ±30 kV air), thermal derating above 25 °C, unidirectional polarity compatibility with DC-biased circuits, and SMA package footprint compliance with IPC7531.

Technical Context

The SMA4F22A employs planar silicon avalanche technology optimized for low leakage and high-temperature stability. Its breakdown voltage is specified at 24.4–27.0 V (min–max) with 9.6 × 10⁻⁴ /°C voltage temperature coefficient, enabling predictable VBR and VCL drift across –55 °C to +175 °C operation.

Clamping behavior is defined by dynamic resistance (RD = 0.444 Ω) and follows VCL = VBR(max) + RD × IPP, supporting precise overvoltage limiting during 8/20 µs (48.3 A) and 10/1000 µs (11.2 A) transients. Peak pulse power de-rates linearly from 400 W at 25 °C to 200 W at 175 °C per Figure 3.

Key Specifications

Pinout & Package

The SMA4F22A is housed in an industry-standard SMA (DO-214AC) flat plastic 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 unidirectional TVS diode applications.

Compared with SMAJ22A and SMBJ22A, the SMA4F22A delivers superior thermal robustness (175 °C Tj), lower clamping voltage (35.5 V), and verified performance across full automotive temperature range-making it optimal for compact, high-reliability DC rail protection where leakage and thermal margin are critical.

Availability

SMA4F22A is available at Aetrix Electronics and suitable for automotive body electronics, industrial PLC inputs, DC power supply outputs, and smart meter communication interfaces requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SMA4F22A 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 analog/mixed-signal portfolio.

The SMA4F series belongs to ST's Transil™ TVS diode product line, engineered specifically for high-reliability transient suppression in harsh-environment applications-emphasizing low leakage, high-temperature stability, and IEC 61000-4-2 compliance.

FAQ

What is the maximum clamping voltage of SMA4F22A under a 10/1000 µs surge?

The maximum clamping voltage is 35.5 V at 11.2 A for a 10/1000 µs waveform, measured at 25 °C ambient. This value increases with junction temperature per the αT coefficient (9.6 × 10⁻⁴ /°C), reaching approximately 37.2 V at 125 °C using the formula VCL(Tj) = VCL(25°C) × [1 + αT × (Tj − 25)].

Can SMA4F22A be used in bidirectional signal line protection?

No-SMA4F22A is strictly unidirectional and must be installed with cathode toward the protected line. For bidirectional protection (e.g., USB, RS-485), ST offers the SMA4F22AY variant or discrete back-to-back configurations; using SMA4F22A on AC-coupled or floating lines risks forward conduction and failure.

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

At 0.2 µA max leakage (25 °C), SMA4F22A draws less than 1.7 mC per year-equivalent to ~0.0005 % annual capacity loss in a 100 mAh coin cell. This enables multi-year operation in always-on sensors and remote monitors without measurable battery depletion from the TVS itself.

Is the SMA4F22A compatible with lead-free reflow soldering processes?

Yes-the device is qualified per J-STD-020 MSL Level 1 and supports ST's recommended reflow profile: peak temperature 240–245 °C for 2–3 seconds, ramp-up ≤3 °C/s, and cooling rate ≥−2 °C/s. Matte tin plating ensures reliable wetting and intermetallic formation without voiding or dewetting.