onsemi SA120AG

Overview

SA120AG from onsemi is a unidirectional 500 W peak power MiniMOSORB Zener transient voltage suppressor (TVS) designed for clamping high-energy transients in DC power rails and signal lines. It features a 120 V working peak reverse voltage (VRWM), 199 V minimum breakdown voltage (VBR) at 1 mA, 275 V maximum clamping voltage (VC) at 3.1 A peak pulse current (IPP), and sub-1 ns response time. It is used in industrial power supplies and telecom interface protection where robust overvoltage immunity is required.

For engineers reviewing the SA120AG datasheet, pinout, applications, or equivalent options, key selection criteria include VRWM ≥ system operating voltage, VC margin relative to protected IC absolute maximum ratings, UL 497B recognition for isolated loop compliance, and axial leaded Surmetic package thermal derating above 50°C.

Technical Context

The SA120AG operates as a unidirectional Zener-clamp TVS diode, conducting only during negative transients relative to its cathode-banded polarity. Its clamping action begins at VBR = 189–209 V (tested at IT = 1 mA), with VC = 275 V measured at IPP = 3.1 A under 1.0 ms 8.3 ms half-sine surge waveform per Figure 4.

Thermal performance is defined by RJL = 33.3°C/W junction-to-lead resistance and steady-state power dissipation PD = 3.0 W at TL ≤ 25°C, derated linearly to 30 mW/°C above TL = 50°C. It meets UL 497B for isolated loop circuit protection and exhibits ESD robustness >16 kV HBM.

Key Specifications

Pinout & Package

SA120AG is housed in ON Semiconductor's Surmetic axial-leaded plastic package (Case 59AA), featuring corrosion-resistant leads solderable at 260°C for 10 seconds at 1/16″ from case. Polarity is marked by a cathode band; anode and cathode terminals are axially oriented with no internal die bonding variation across SA-series variants.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ120A and SMF120A, SA120AG delivers higher surge robustness (500 W vs. 400 W/200 W), tighter clamping (275 V vs. 291 V/312 V), and UL 497B certification-making it the only option qualified for safety-critical isolated loop protection in industrial and medical systems.

Availability

SA120AG is available at Aetrix Electronics and suitable for industrial power supplies, telecom line interfaces, medical equipment input stages, and process control sensor buses requiring stable component supply and long-lifecycle support.

Supply support for SA120AG 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 power management, analog, sensors, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The SA5.0A Series-including SA120AG-is part of onsemi's MiniMOSORB transient voltage suppressor family, engineered specifically for high-reliability overvoltage protection in harsh industrial and telecom environments where UL 497B compliance and 500 W surge capability are mandatory.

FAQ

What is the maximum clamping voltage of SA120AG under standard test conditions?

The SA120AG has a maximum clamping voltage (VC) of 275 V when subjected to a peak pulse current (IPP) of 3.1 A using the 1.0 ms waveform defined in Figure 4 of the datasheet. This value ensures downstream components rated for ≤300 V absolute maximum will remain within safe operating limits during surge events. The SA120AG maintains this clamping performance across its full operating temperature range of −55°C to +150°C.

Does SA120AG meet UL 497B requirements for isolated loop protection?

Yes, SA120AG is explicitly covered under onsemi's UL 497B recognition (File #E210057, QVGQ2 category) for protector-class applications. This certification confirms successful completion of Strike Voltage Breakdown, Endurance Conditioning, Dielectric Withstand, and Discharge tests-not merely flammability compliance. The SA120AG is approved for use in isolated loop circuits where safety-critical transient suppression is mandated, such as medical and industrial control systems.

What is the thermal derating behavior of SA120AG above 25°C lead temperature?

SA120AG's steady-state power dissipation (PD) is rated at 3.0 W up to TL = 25°C, then derated linearly at 30 mW/°C above that point, reaching zero at TL = 125°C (per Figure 5). For example, at TL = 75°C, PD = 3.0 W − (50 × 0.03) = 1.5 W. This derating applies only to continuous power; the 500 W peak pulse rating remains valid per Figure 1 as long as pulse repetition is limited per Figure 2.

How does the SA120AG differ from SA120A without the "G" suffix?

The "G" suffix in SA120AG denotes a Pb-free Surmetic axial package compliant with RoHS Directive 2011/65/EU. Electrically and thermally, SA120AG is identical to SA120A; the only difference is lead finish and packaging material. Both share identical VRWM (120 V), VBR (189–209 V), VC (275 V), and UL 497B certification. SA120AG is the default offering for new designs requiring lead-free compliance.

Can SA120AG be used in bidirectional protection configurations?

No, SA120AG is a unidirectional TVS diode intended for clamping only in the reverse direction (cathode positive relative to anode). It does not provide symmetrical clamping for AC or bipolar transients. For bidirectional protection, onsemi offers the CA-series counterparts (e.g., SA120CA), which integrate two opposing Zener diodes in series. Using SA120AG in a bidirectional configuration would leave the forward direction unprotected above ~1.5 V.