Diodes Incorporated SMAJ18A-13-F

Overview

SMAJ18A-13-F from Diodes Incorporated is a unidirectional 400W surface-mount transient voltage suppressor (TVS) diode designed for primary overvoltage protection in DC power lines and signal interfaces. It features a 18V reverse standoff voltage (VRWM), 20.0–22.1V breakdown voltage (VBR), 29.2V max clamping voltage (VC) at 13.7A peak pulse current (IPP), and SMA package with cathode band polarity indicator.

For engineers reviewing the SMAJ18A-13-F datasheet, SMAJ18A-13-F pinout, SMAJ18A-13-F application, or SMAJ18A-13-F equivalent, key selection criteria include clamping performance under 8.3ms surge, unidirectional polarity handling, RoHS-compliant lead-free plating, and compatibility with automated SMT assembly on industrial and automotive PCBs.

Technical Context

This TVS diode operates as a fast-acting shunt protector, triggering when transient voltage exceeds its 18V standoff threshold and clamping to ≤29.2V within picoseconds. Its glass-passivated junction ensures stable VBR tolerance (±5%) and low leakage (<5µA at VRWM).

Designed for single-pulse transients per JEDEC standards, it sustains 400W peak pulse power (8.3ms half-sine), supports 40A non-repetitive forward surge current, and maintains operation across –55°C to +150°C junction temperature range - suitable for harsh-environment deployments.

Key Specifications

Pinout & Package

Two-terminal SMA package: anode and cathode terminals aligned along body axis, with molded plastic case (UL 94V-0), matte tin-plated leads, and visible cathode band marking for unidirectional polarity identification.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ18A-13-F, SMAJ18A-TP offers identical protection in alternate packaging, while SMCJ18A-13-F delivers greater surge capacity in a physically incompatible SMC outline - making the original SMAJ18A-13-F optimal for space-constrained, cost-sensitive 400W-class designs.

Availability

SMAJ18A-13-F is available at Aetrix Electronics and suitable for industrial PLC I/O protection, automotive body control modules, and DC power supply input stages requiring stable component supply and full traceability.

Supply support for SMAJ18A-13-F 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, headquartered in Plano, Texas, with design, manufacturing, and sales operations across Asia, Europe, and North America.

The SMAJ series belongs to Diodes' transient voltage suppression portfolio, engineered specifically for high-reliability, surface-mount overvoltage protection in automotive, industrial, and communications infrastructure applications.

FAQ

What is the maximum clamping voltage for SMAJ18A-13-F under standard test conditions?

The maximum clamping voltage (VC) is 29.2V at 13.7A peak pulse current (IPP), measured using an 8.3ms half-sine waveform per IEC 61000-4-5. This value is guaranteed across the full operating temperature range (–55°C to +150°C) and represents the upper limit of voltage seen by downstream circuitry during a surge event.

Is SMAJ18A-13-F suitable for bidirectional signal line protection?

No - SMAJ18A-13-F is unidirectional, indicated by the absence of "C" in its part number. For bidirectional protection (e.g., AC lines or differential buses), use SMAJ18CA-13-F, which has symmetrical clamping in both polarities and no cathode band marking.

Does this TVS diode require derating at elevated ambient temperatures?

Yes - peak pulse power must be derated linearly above +25°C ambient, following the curve in Figure 1 of DS19005. At +75°C, rated pulse power drops to ~75% of 400W (≈300W), and at +125°C, it falls to ~40% (≈160W), based on thermal resistance and junction-to-ambient characteristics of the SMA package.

How does the SMAJ18A-13-F compare to older P6KE18A in terms of PCB assembly compatibility?

SMAJ18A-13-F uses the surface-mount SMA package (4.0–4.6mm length), whereas P6KE18A is through-hole DO-15 (9.5mm length). They are not footprint-compatible. SMAJ18A-13-F supports modern high-speed reflow assembly, eliminates manual insertion, and reduces board area by >60%, but requires verified stencil design for optimal solder joint reliability.