Diodes Incorporated SMF4L45A-7

Overview

SMF4L45A-7 from Diodes Incorporated is a unidirectional 400W surface-mount transient voltage suppressor (TVS) designed for robust overvoltage protection in power rails and I/O lines. It features a 45V working peak reverse voltage (VRWM), 50–55.3V breakdown voltage range (VBR), and clamps transients to ≤72.7V at 5.5A peak surge current, making it suitable for automotive battery line protection and industrial sensor interface circuits.

For engineers reviewing the SMF4L45A-7 datasheet, SMF4L45A-7 pinout, SMF4L45A-7 application, or SMF4L45A-7 equivalent, key selection criteria include clamping voltage margin vs. system rail tolerance, 1.0ns unidirectional response time, DO-219AA package thermal resistance (RθJA = 96°C/W), and compliance with IEC61000-4-2 ±30kV ESD immunity.

Technical Context

This TVS diode operates as a voltage-clamped shunt protector: under normal bias (≤45V), it presents <0.5µA leakage; during transient events exceeding VBR (50–55.3V), it avalanches to limit voltage across protected circuitry. Its unidirectional polarity-marked by cathode band-enables DC-biased rail protection without reverse conduction path concerns.

The device uses silicon avalanche junction technology optimized for fast turn-on (<1.0ns) and high-energy absorption (400W, 10/1000µs waveform). Thermal design relies on low RθJC (18°C/W) and RθJS (70°C/W), requiring minimal PCB copper area for 1.0W steady-state dissipation in ambient up to +175°C.

Key Specifications

Pinout & Package

Package: DO-219AA - ultra-compact surface-mount molded plastic case (2.80mm × 1.90mm footprint, 3.80mm height), RoHS-compliant matte tin finish on copper alloy lead frame, moisture sensitivity level 1.

Key Features

Applications

Availability

SMF4L45A-7 is available at Aetrix Electronics and suitable for automotive battery management, LIN bus interfaces, industrial sensor power rails, and USB-C VBUS protection requiring stable component supply across production lifecycles.

Supply support for SMF4L45A-7 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 semiconductor company specializing in discrete, analog, and mixed-signal solutions, with manufacturing certified to IATF 16949 and product qualification to AEC-Q101 standards.

The SMF4L series belongs to Diodes' high-reliability TVS portfolio, engineered specifically for automotive and industrial applications demanding robust ESD/surge immunity in ultra-small DO-219AA packages.

FAQ

What is the polarity configuration of SMF4L45A-7?

SMF4L45A-7 is a unidirectional TVS diode, indicated by the cathode band marking on the DO-219AA package. It conducts only when the cathode is biased positive relative to the anode, making it suitable for DC power rail protection where reverse voltage is not expected.

How does SMF4L45A-7 compare to SMAJ45A in terms of package and thermal performance?

SMF4L45A-7 uses DO-219AA (2.80mm × 1.90mm), while SMAJ45A uses DO-214AC (4.5mm × 2.7mm). The smaller DO-219AA yields higher power density but requires tighter thermal layout: RθJA is 96°C/W vs. ~60°C/W for SMAJ45A on identical PCBs, necessitating careful copper area allocation.

Can SMF4L45A-7 be used in bidirectional signal lines like RS-485?

No - SMF4L45A-7 is unidirectional only. For bidirectional data lines, the bi-directional variant SMF4L45CA must be selected, which has symmetrical clamping in both polarities and no cathode band marking.

What is the maximum allowable PCB trace length between SMF4L45A-7 and protected IC?

To preserve <1.0ns response, PCB trace inductance must be minimized: total loop inductance should remain ≤5nH. This typically limits trace length to ≤8mm with 0.25mm width and ground plane beneath, verified via TDR measurement in high-speed automotive designs.