Vishay General Semiconductor - Diodes Division SMAJ20A-M3/5A

Overview

SMAJ20A-M3/5A from Vishay General Semiconductor is a unidirectional surface-mount transient voltage suppressor (TVS) diode in SMA (DO-214AC) package, designed for clamping fast-rising ESD and surge transients on power and signal lines. It features 20 V stand-off voltage (VWM), 22.2–24.5 V breakdown voltage (VBR) at 1 mA, 32.4 V maximum clamping voltage (VC) at 12.3 A peak pulse current (IPPM), and 400 W peak pulse power (10/1000 μs waveform).

For engineers reviewing the SMAJ20A-M3/5A datasheet, SMAJ20A-M3/5A pinout, SMAJ20A-M3/5A application, or SMAJ20A-M3/5A equivalent, key selection criteria include clamping performance under 12.3 A surge, thermal resistance (RθJA = 120 °C/W), unidirectional polarity marking, halogen-free RoHS compliance (M3 suffix), and suitability for automotive-grade designs when paired with AEC-Q101-qualified variants.

Technical Context

The SMAJ20A-M3/5A operates as a silicon avalanche diode that enters breakdown when reverse voltage exceeds its VBR range (22.2–24.5 V), limiting transient energy by shunting excess current to ground. Its glass-passivated junction ensures stable leakage (<1.0 μA at 20 V) and fast response time (<1.0 ns), critical for protecting downstream ICs from ESD per IEC 61000-4-2.

Thermally, it relies on PCB copper pad area (0.2" × 0.2") for heat dissipation, with RθJL = 30 °C/W to lead and rated for TJ up to +150 °C. The M3 suffix confirms halogen-free, RoHS-compliant construction meeting JESD201 Class 2 whisker resistance and MSL Level 1 reflow compatibility (260 °C peak).

Key Specifications

Pinout & Package

Package: SMA (DO-214AC), surface-mount, low-profile case with matte tin-plated leads solderable per J-STD-002. Cathode indicated by band marking on unidirectional devices.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ20A-M3/5A, the E3 variant offers identical protection performance at lower cost for non-automotive use, while the HE3 variant adds AEC-Q101 validation and wider temperature assurance-neither is pin-compatible with SMAJ20A-M3/5A in terms of qualification status, though all share identical SMA package and pinout.

Availability

SMAJ20A-M3/5A is available at Aetrix Electronics and suitable for automotive power rail protection, industrial sensor interface hardening, consumer USB VBUS safeguarding, and telecom line driver surge suppression requiring stable component supply and halogen-free compliance.

Supply support for SMAJ20A-M3/5A 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

Vishay General Semiconductor is a global leader in discrete semiconductors, specializing in diodes, MOSFETs, optoelectronics, and passive components with emphasis on reliability and application-specific performance.

The SMAJ series is engineered for robust transient suppression in harsh environments-designed to meet IEC 61000-4-2/4-5 standards and support automotive, industrial, and telecom infrastructure where repeatable clamping and long-term stability are critical.

FAQ

What is the clamping voltage of SMAJ20A-M3/5A at its rated peak pulse current?

The SMAJ20A-M3/5A exhibits a maximum clamping voltage (VC) of 32.4 V when subjected to its rated peak pulse current (IPPM) of 12.3 A under the standardized 10/1000 μs waveform. This value is measured per Figure 1 in Vishay document 88390 and defines the upper voltage limit imposed on protected circuitry during surge events. Maintaining VC below 33 V ensures compatibility with 3.3 V and 5 V logic interfaces commonly found in microcontrollers and communication ICs.

Is SMAJ20A-M3/5A suitable for automotive applications?

SMAJ20A-M3/5A is a commercial-grade, halogen-free TVS diode and is not AEC-Q101 qualified. For automotive use, Vishay offers the SMAJ20AHM3_A/I variant, which shares identical electrical specs and SMA packaging but includes full AEC-Q101 qualification and extended temperature validation. Engineers must select HM3-suffixed versions-not M3-for under-hood or safety-critical vehicle systems.

What does the "M3" suffix indicate in SMAJ20A-M3/5A?

The "M3" suffix in SMAJ20A-M3/5A denotes halogen-free, RoHS-compliant construction meeting JESD201 Class 2 whisker resistance and MSL Level 1 reflow compatibility (260 °C peak). It distinguishes this variant from the E3 (RoHS-compliant, non-halogen-free) and HM3/HE3 (AEC-Q101 qualified) families. The M3 designation confirms compliance with environmental regulations without sacrificing surge performance or thermal reliability.

How does SMAJ20A-M3/5A compare to SMAJ15A-M3/5A in terms of voltage rating and application scope?

SMAJ20A-M3/5A has a 20 V stand-off voltage (VWM) and 22.2–24.5 V breakdown range, making it appropriate for 12 V–24 V systems like automotive power rails and industrial 24 V PLCs. In contrast, SMAJ15A-M3/5A (VWM = 15 V) targets lower-voltage domains such as 5 V USB VBUS or 3.3 V I/O protection. Their clamping voltages differ-32.4 V vs. 24.4 V-so substituting one for the other requires verifying that the protected IC's absolute maximum rating accommodates the higher VC.

What is the thermal resistance and maximum junction temperature of SMAJ20A-M3/5A?

SMAJ20A-M3/5A has a typical junction-to-ambient thermal resistance (RθJA) of 120 °C/W when mounted on 0.2" × 0.2" copper pads, and a maximum junction temperature (TJ max.) of +150 °C. These values define its power derating curve: at 75 °C ambient, its 3.3 W steady-state power dissipation drops to ~1.7 W. Designers must ensure adequate PCB copper area and avoid enclosure hotspots to maintain reliable long-term operation within this thermal envelope.