Taiwan Semiconductor Corporation SMA4F40AH

Overview

SMA4F40AH from Taiwan Semiconductor is a unidirectional 400W surface-mount transient voltage suppressor (TVS) diode with a 40 V working stand-off voltage, 44.7–49.4 V breakdown voltage at 1 mA, and 64.9 V maximum clamping voltage at 6.2 A peak pulse current. It is AEC-Q101 qualified and designed for automotive power rail protection in BLDC motor drives and battery management systems.

For engineers reviewing the SMA4F40AH datasheet, SMA4F40AH pinout, SMA4F40AH application, or SMA4F40AH equivalent, key selection criteria include its 400 W 10/1000 µs peak pulse power rating, ±0.095%/°C V_BR temperature coefficient, UL 94V-0 mold compound, and Thin SMA package compatibility with J-STD-002 solderability requirements.

Technical Context

The SMA4F40AH operates as a unidirectional avalanche diode, leveraging glass-passivated junction technology to achieve stable breakdown behavior across –55°C to +175°C junction temperature range. Its thermal design relies on low R_θJL = 20°C/W and R_θJC = 16°C/W, enabling effective heat transfer from junction to lead and case when mounted on a 5 mm × 5 mm copper pad PCB.

It delivers 64.9 V clamping voltage under 6.2 A 10/1000 µs impulse, limiting transient overvoltage during load dump or inductive switching events. With 1 µA max reverse leakage at 40 V and 3.5 V forward voltage at 25 A, it supports robust DC blocking and low-loss conduction during fault conditions.

Key Specifications

Pinout & Package

Package: Thin SMA - Surface-mount package with cathode band marking, matte tin-plated leads, UL 94V-0 molding compound, and 0.030 g mass. Compliant with JESD201 Class 2 whisker testing and J-STD-020 moisture sensitivity level 1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ40A and SMBJ40A, the SMA4F40AH offers identical electrical clamping performance in a thinner, AEC-Q101-qualified Thin SMA package-making it optimal for space-constrained automotive modules where qualification and profile height are decisive.

Availability

SMA4F40AH is available at Aetrix Electronics and suitable for BLDC motor drives, battery management systems, automotive lighting, and switching mode power supplies requiring stable component supply with automotive-grade reliability and thin-profile packaging.

Supply support for SMA4F40AH 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 analog and discrete semiconductor manufacturer headquartered in Hsinchu, Taiwan, serving automotive, industrial, and consumer markets since 1979.

The SMA4FxxAH series is part of TSC's AEC-Q101-qualified TVS portfolio, engineered specifically for high-reliability transient suppression in automotive power distribution networks and electric vehicle subsystems.

FAQ

What is the clamping voltage of the SMA4F40AH under peak pulse conditions?

The SMA4F40AH has a maximum clamping voltage (V_C) of 64.9 V at 6.2 A peak pulse current with a 10/1000 µs waveform. This value is measured per JEDEC standards and defines the upper voltage limit imposed on protected circuitry during surge events. The SMA4F40AH maintains this clamping performance across its rated junction temperature range of –55°C to +175°C, making it suitable for under-hood automotive deployment where thermal stability is critical.

Is the SMA4F40AH suitable for automotive applications?

Yes, the SMA4F40AH is AEC-Q101 qualified and explicitly designed for automotive use. Its glass-passivated junction, –55°C to +175°C operating range, UL 94V-0 molding compound, and JESD201 Class 2 whisker resistance meet stringent automotive reliability requirements. The SMA4F40AH is deployed in BLDC motor drives, lighting modules, and battery management systems where transient immunity and long-term stability are mandatory.

What is the reverse leakage current specification for the SMA4F40AH at its working voltage?

The SMA4F40AH exhibits a maximum reverse leakage current (I_R) of 1 µA at its 40 V working stand-off voltage (V_WM) and 25°C ambient temperature. This low leakage ensures minimal power loss in always-on automotive circuits such as battery monitoring paths or sensor bias rails. The specification is guaranteed per datasheet Table "ELECTRICAL SPECIFICATIONS" and remains valid across the full operating temperature range when derated per thermal curves.

Does the SMA4F40AH have a unidirectional or bidirectional configuration?

The SMA4F40AH is a unidirectional transient voltage suppressor, indicated by its single cathode band marking and specified forward voltage (V_F = 3.5 V at 25 A). It conducts only during positive overvoltage events on the cathode side and blocks reverse current up to –40 V. This configuration is ideal for DC power rail protection where polarity is fixed, such as 40 V battery feeds or regulated auxiliary supplies.

What is the thermal resistance from junction to ambient for the SMA4F40AH?

The SMA4F40AH has a junction-to-ambient thermal resistance (R_θJA) of 62°C/W when mounted on a standard 5 mm × 5 mm copper pad test board. This value assumes natural convection and is used to calculate steady-state junction temperature rise under continuous power dissipation. For accurate thermal modeling, designers must account for actual PCB copper area, airflow, and adjacent heat sources-since R_θJA is highly layout-dependent.