onsemi SA51AG

Overview

SA51AG from onsemi is a unidirectional 500 W peak power MiniMOSORB Zener transient voltage suppressor (TVS) designed to protect voltage-sensitive circuits from high-energy transients. It features a 51 V working peak reverse voltage (VRWM), 82.4 V clamping voltage at 6.1 A peak pulse current, <1 µA leakage above 8.5 V, <1 ns response time, and UL 497B recognition for isolated loop circuit protection - used in industrial power supplies and medical equipment surge protection.

For engineers reviewing the SA51AG datasheet, pinout, applications, or equivalent options, key selection criteria include VRWM ≥ system DC operating voltage, clamping voltage margin relative to protected IC V_MAX, surge current capability under 1 ms pulses, thermal derating at elevated lead temperatures, and UL 497B compliance for safety-critical signal line protection.

Technical Context

The SA51AG operates as a unidirectional Zener-based TVS diode, conducting only during reverse overvoltage events while remaining high-impedance under normal bias. Its clamping action begins at breakdown voltage (V_BR = 56.7–62.7 V @ 1 mA), limiting transient energy with low zener impedance and fast carrier response.

It is rated for 500 W nonrepetitive peak power per 1.0 ms pulse (Figure 4 waveform), with thermal derating to 3.0 W steady-state power at T_L ≤ 25°C and 30 mW/°C above 50°C. The axial Surmetic package (Case 59AA) provides void-free thermoset plastic encapsulation and Pb-free leads solderable at 260°C for 10 seconds.

Key Specifications

Pinout & Package

SA51AG uses an axial-leaded Surmetic package (Case 59AA), with cathode identified by a polarity band. Leads are tin-plated copper, corrosion-resistant, and solderable at 260°C for 10 seconds at 1/16″ from case. Mounting position is unrestricted.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMBJ51A and P6KE51A, SA51AG uniquely combines UL 497B recognition, 500 W surge capability in axial form, and <1 µA leakage - making it preferred for safety-certified medical and telecom signal line protection where regulatory compliance and low standby current are critical.

Availability

SA51AG is available at Aetrix Electronics and suitable for industrial power supplies, medical equipment signal conditioning, and telecom interface protection requiring stable component supply and long-term lifecycle support.

Supply support for SA51AG 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, analog, sensing, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The SA5.0A Series was engineered specifically for high-reliability transient suppression in harsh environments - targeting communication infrastructure, process controls, and safety-critical medical systems where UL 497B compliance and robust surge handling are mandatory.

FAQ

What is the clamping voltage of SA51AG at its rated peak pulse current?

The SA51AG has a maximum clamping voltage (V_C) of 82.4 V at its rated peak pulse current (I_PP) of 6.1 A, measured per the 1.0 ms nonrepetitive pulse waveform defined in Figure 4 of the datasheet. This value ensures predictable overvoltage limiting during surge events and must be compared directly against the absolute maximum voltage rating of downstream components protected by the SA51AG.

Is SA51AG certified for safety-critical applications like medical equipment?

Yes, SA51AG carries UL 497B recognition (File #E210057) for isolated loop circuit protection, validating its use in patient-connected medical devices and other safety-critical systems. This certification covers tests including strike voltage breakdown, endurance conditioning, and dielectric withstand - distinguishing it from generic TVS diodes lacking such qualification.

What is the maximum steady-state power dissipation for SA51AG at 25°C lead temperature?

At a lead temperature (T_L) of 25°C, SA51AG is rated for 3.0 W steady-state power dissipation. This rating decreases linearly at 30 mW/°C above 50°C, as shown in Figure 5. Designers must calculate actual lead temperature rise based on PCB copper area and ambient conditions to avoid exceeding this limit during continuous fault conditions.

Does SA51AG have a Pb-free package, and what is its soldering profile?

Yes, the "G" suffix in SA51AG denotes a Pb-free Surmetic axial package. The maximum lead temperature for soldering is 260°C at a distance of 1/16 inch from the case for 10 seconds. All external surfaces are corrosion-resistant, and leads are readily solderable - consistent with J-STD-020 moisture sensitivity level 1 requirements.

How does the breakdown voltage range of SA51AG compare to its working peak reverse voltage?

SA51AG has a specified working peak reverse voltage (VRWM) of 51 V and a breakdown voltage (V_BR) range of 56.7–62.7 V at 1 mA test current. This 5.7–11.7 V margin ensures reliable blocking of normal operating voltages while guaranteeing conduction onset before reaching damaging levels - a key design parameter verified per Note 4 on page 3 of the SA5.0A/D datasheet.