onsemi SA28AG

Overview

SA28AG from onsemi is a unidirectional 500 W peak power MiniMOSORB Zener transient voltage suppressor (TVS) designed to protect sensitive electronics against high-energy transients. It features a 28 V working peak reverse voltage (VRWM), 45.4 V clamping voltage at 11 A peak pulse current, and sub-1 ns response time. It is commonly deployed in industrial power supplies and communication interface circuits requiring robust surge immunity.

For engineers reviewing the SA28AG datasheet, pinout, applications, or equivalent options, key selection criteria include clamping performance under 10/1000 µs surge waveforms, UL 497B certification for isolated loop protection, low zener impedance, ESD tolerance >16 kV (HBM), and axial leaded Surmetic package compatibility with through-hole assembly processes.

Technical Context

The SA28AG operates as a unidirectional Zener-based TVS diode, activated only during reverse overvoltage events above its 31.1–34.4 V breakdown range. Its clamping action limits transient-induced voltage excursions to ≤45.4 V at 11 A, enabling reliable protection of downstream ICs such as RS-485 transceivers or microcontroller I/O rails.

It leverages onsemi's proprietary Surmetic axial-leaded package (Case 59AA) with void-free thermosetting plastic encapsulation, rated for 260°C soldering at 10 seconds, and features a cathode band polarity indicator. Thermal resistance from junction-to-lead is 33.3°C/W, supporting steady-state dissipation up to 3.0 W at 25°C ambient.

Key Specifications

Pinout & Package

SA28AG is housed in an axial-leaded Surmetic plastic package (Case 59AA), featuring a cathode band marking and lead diameter 0.71–0.86 mm. Mounting position is unrestricted; leads are solderable per J-STD-001.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ28A and P6KE28A, SA28AG uniquely combines UL 497B certification, axial-leaded manufacturability, and optimized clamping for 24 V industrial systems-making it the preferred choice for safety-certified, high-reliability through-hole deployments.

Availability

SA28AG is available at Aetrix Electronics and suitable for industrial power supplies, RS-485 communication interfaces, and medical equipment DC adapters requiring stable component supply and full regulatory traceability.

Supply support for SA28AG 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient silicon solutions for automotive, industrial, cloud, and IoT applications.

The SA28AG belongs to the SA5.0A Series MiniMOSORB TVS family, engineered specifically for high-surge, low-clamping protection of voltage-sensitive components in harsh industrial and communications environments.

FAQ

What is the clamping voltage of SA28AG at its rated peak pulse current?

The SA28AG clamps to a maximum of 45.4 V when subjected to its specified peak pulse current of 11 A, measured using the standard 10/1000 µs double-exponential waveform. This value is guaranteed across temperature and ensures downstream circuitry remains below destructive voltage thresholds during surge events. The SA28AG maintains this performance consistently due to its low zener impedance and tight VBR distribution.

Does SA28AG meet UL 497B requirements for isolated loop protection?

Yes, SA28AG is explicitly listed under UL 497B (File #E210057, QVGQ2 category) for isolated loop circuit protection. This certification covers rigorous testing including strike voltage breakdown, endurance conditioning, dielectric withstand, and discharge performance. The SA28AG's qualification applies directly to its SA5.0A Series family designation and is documented in the official onsemi UL recognition summary.

What is the thermal resistance and steady-state power rating of SA28AG?

The SA28AG has a junction-to-lead thermal resistance (R_JL) of 33.3°C/W and a steady-state power dissipation rating of 3.0 W at 25°C ambient with 3/8-inch lead length. Derating follows the curve in Figure 5, reducing to zero at 150°C lead temperature. This allows reliable operation in enclosed industrial enclosures where airflow is limited and ambient temperatures may exceed 70°C.

Is SA28AG compatible with lead-free soldering processes?

Yes, SA28AG is supplied in a Pb-free Surmetic axial package qualified for lead-free reflow and hand-soldering. Its leads withstand 260°C for 10 seconds at 1/16 inch from the case body, meeting J-STD-020 and IPC-J-STD-001 requirements. The "G" suffix in SA28AG explicitly denotes this Pb-free construction, and no special pre-conditioning or flux selection is required beyond standard RoHS-compliant practices.

How does SA28AG differ from SA24AG or SA30AG in terms of voltage ratings?

SA28AG is specifically rated for 28 V VRWM, with VBR spanning 31.1–34.4 V and VC = 45.4 V @ 11 A. In contrast, SA24AG has VRWM = 24 V (VBR = 26.7–29.5 V, VC = 38.9 V), while SA30AG has VRWM = 30 V (VBR = 33.3–36.8 V, VC = 48.4 V). These discrete voltage steps allow precise matching to system operating voltages-SA28AG targets 24 V nominal rails with headroom, avoiding premature clamping or insufficient protection.