Taiwan Semiconductor Corporation SMAJ30C

Overview

SMAJ30C from Taiwan Semiconductor is a unidirectional 30V stand-off transient voltage suppressor (TVS) diode in DO-214AC (SMA) package, rated for 400W peak pulse power (10/1000μs), 53.5V clamping voltage at 7.5A peak impulse current, and operating junction temperature up to +150°C. It protects DC/DC converters, SMPS outputs, and automotive lighting circuits against ESD and load dump transients.

For engineers reviewing the SMAJ30C datasheet, SMAJ30C pinout, SMAJ30C application, or SMAJ30C equivalent, this page delivers verified electrical parameters, bidirectional capability context (C suffix), DO-214AC mechanical interface details, and direct alternatives with clamping and leakage differences critical for overvoltage protection design.

Technical Context

The SMAJ30C is a unidirectional TVS diode with glass-passivated junction and fast response time (<1.0 ps from 0 V to V_BR min). Its breakdown voltage is specified at 33.3–40.7 V with 1 mA test current, and it maintains <1 μA reverse leakage at 30 V working stand-off voltage.

It meets ISO 7637-2 Pulse 1/2a/2b/3a/3b for automotive transient immunity and is rated for 150°C maximum junction temperature. The device uses a single-die configuration in a moisture-sensitive level 1 (J-STD-020) package with matte tin-plated leads.

Key Specifications

Pinout & Package

DO-214AC (SMA) package: molded epoxy case meeting UL 94V-0, cathode band marked on body, matte tin-plated leads, polarity as marked. Weight ≈ 0.060 g.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ30C, SMAJ30A offers tighter breakdown control and lower clamping for precision rails, while SMBJ30C provides 50% higher pulse power in a larger footprint-enabling trade-offs between layout density, thermal margin, and transient severity coverage.

Availability

SMAJ30C is available at Aetrix Electronics and suitable for automotive lighting, on-board DC/DC converters, and industrial adapters requiring stable component supply, full traceability, and lifecycle continuity.

Supply support for SMAJ30C 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

Taiwan Semiconductor Corporation (TSC) is a vertically integrated semiconductor manufacturer specializing in discrete power devices, TVS diodes, and rectifiers for automotive, industrial, and consumer markets.

The SMAJ series was designed specifically for surface-mount transient suppression in space-constrained, high-reliability applications-emphasizing fast response, low leakage, and AEC-Q200-aligned robustness without requiring derating at elevated ambient temperatures.

FAQ

What does the "C" suffix indicate in SMAJ30C?

The "C" suffix in SMAJ30C denotes a unidirectional configuration, meaning it functions as a single-polarity TVS diode with anode and cathode terminals. Unlike "CA" parts, SMAJ30C has asymmetric conduction: it blocks voltage up to 30 V in reverse bias and clamps transients only when the cathode is more positive than the anode. This matches standard DC rail protection topology and is confirmed in the device's polarity marking and electrical specifications table.

Is SMAJ30C suitable for ISO 7637-2 Pulse 5a (load dump) protection?

SMAJ30C is rated for 400W peak pulse power with a 10/1000μs waveform and meets ISO 7637-2 Pulse 1/2a/2b/3a/3b-but not Pulse 5a (load dump), which requires sustained energy handling beyond its non-repetitive rating. For Pulse 5a, a higher-energy device like 5.0SMDJ33C (5000W) or hybrid TVS-MOV solutions is required. SMAJ30C is appropriate for lower-energy transients such as switching noise and ESD.

What is the maximum steady-state power dissipation for SMAJ30C?

The maximum steady-state power dissipation (P_D) for SMAJ30C is 1 W at T_A = 25°C, as specified in the Absolute Maximum Ratings table. This value decreases linearly with rising ambient temperature per the Pulse Derating Curve (Fig.2), reaching zero at approximately 150°C. It is not intended for continuous power dissipation but for transient energy absorption only.

Does SMAJ30C have a defined junction capacitance value?

No junction capacitance (C_J) value is published for SMAJ30C in the provided documentation. While Fig.3 shows a generic C_J vs. V_BR curve for the SMAJ family, no specific capacitance figure is assigned to SMAJ30C at any bias voltage. For high-frequency signal line protection where C_J matters, consult TSC's application notes or measure using 1 MHz, 50 mV_p-p test conditions per Figure 3 methodology.

How is polarity identified on the SMAJ30C DO-214AC package?

Polarity on the SMAJ30C is indicated by a cathode band printed on the body of the DO-214AC (SMA) package. Per the Marking Diagram (Page 6), the band corresponds to the cathode terminal, which must be connected to the line being protected (e.g., 30V rail), while the anode connects to ground. This marking is consistent across all unidirectional SMAJ-C variants and aligns with JEDEC-standard SMA orientation.