Taiwan Semiconductor Corporation SMA4S56AH

Overview

SMA4S56AH from Taiwan Semiconductor is a unidirectional 400W surface-mount transient voltage suppressor (TVS) diode with a 56V working stand-off voltage, 62.6–69.2V breakdown voltage at 1mA, and 90.9V clamping voltage at 4.4A peak pulse current; used for overvoltage protection in automotive BLDC motor drives and battery management systems.

For engineers reviewing the SMA4S56AH datasheet, SMA4S56AH pinout, SMA4S56AH application, or SMA4S56AH equivalent, key selection criteria include unidirectional polarity, SOD-128 package thermal performance (R_θJL = 20°C/W), 175°C max junction temperature, and AEC-Q101 qualification for automotive reliability.

Technical Context

This TVS diode operates as a unidirectional clamping device, activated when reverse voltage exceeds V_BR (62.6–69.2V), limiting transient energy to 400W under 10/1000µs waveform. Its glass-passivated junction ensures stable leakage (<1µA at 56V) and low temperature coefficient (0.095%/°C).

Designed for PCB-level surge suppression, it delivers 90.9V clamping at 4.4A IPPM with 3.5V forward voltage at 25A, and achieves thermal dissipation via low R_θJC (16°C/W) and R_θJL (20°C/W) on a 5mm × 5mm copper pad.

Key Specifications

Pinout & Package

Package: SOD-128 - Surface-mount flat lead package with cathode band marking, 0.028g weight, UL 94V-0 molding compound, matte tin-plated leads compliant with J-STD-002 solderability.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ56A and 1.5SMC56A, SMA4S56AH offers superior thermal performance (R_θJL = 20°C/W vs. ≥25°C/W), tighter V_BR tolerance, and AEC-Q101 certification-making it optimal for space-constrained, thermally demanding automotive modules.

Availability

SMA4S56AH is available at Aetrix Electronics and suitable for BLDC motor drives, battery management systems, automotive lighting control, and on-board charger input stages requiring stable component supply with automotive-grade qualification.

Supply support for SMA4S56AH 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 with global distribution and AEC-Q101 validation capabilities.

The SMA4SxxAH series was developed specifically for automotive and industrial DC power rail protection, emphasizing high surge robustness, thermal stability, and surface-mount manufacturability in compact SOD-128 packaging.

FAQ

What is the maximum clamping voltage of the SMA4S56AH under standard test conditions?

The SMA4S56AH has a maximum clamping voltage (V_C) of 90.9 V when subjected to a 10/1000 µs peak pulse current of 4.4 A. This value is measured at T_A = 25°C and defines the upper voltage limit imposed on protected circuitry during transient events. The SMA4S56AH maintains this clamping performance across its specified operating temperature range, making it suitable for automotive environments where voltage excursions must be tightly controlled.

Is the SMA4S56AH suitable for bidirectional transient suppression?

No, the SMA4S56AH is a unidirectional TVS diode and is not designed for bidirectional suppression. Its electrical characteristics-including breakdown voltage, clamping behavior, and leakage current-are specified only for reverse-biased operation. For bidirectional protection, a dedicated bidirectional part such as SMA4S56AY (if offered) or a paired configuration would be required. The SMA4S56AH's marking and cathode band indicate strict polarity-dependent installation.

Does the SMA4S56AH meet automotive reliability standards?

Yes, the SMA4S56AH is AEC-Q101 qualified, confirming compliance with stress tests including high-temperature reverse bias, temperature cycling, and electrostatic discharge. It also meets J-STD-020 moisture sensitivity level 1 and JESD201 class 2 whisker resistance. These qualifications validate its suitability for under-hood and cabin-mounted automotive electronics where long-term reliability under thermal and mechanical stress is critical. The SMA4S56AH's 175°C maximum junction temperature further supports this use case.

What is the thermal resistance from junction to lead (R_θJL) for the SMA4S56AH?

The junction-to-lead thermal resistance (R_θJL) of the SMA4S56AH is 20°C/W, measured under standard conditions using a 5 mm × 5 mm copper pad test board. This low value enables efficient heat conduction from the silicon die to the PCB copper, supporting sustained power dissipation and reducing thermal runaway risk in high-density layouts. When designing thermal relief, this parameter should be used alongside R_θJA = 62°C/W to model total thermal path performance for the SMA4S56AH.

How does the SMA4S56AH compare to the SMA4S51AH in terms of voltage ratings?

The SMA4S56AH has a higher working stand-off voltage (56 V) and breakdown voltage range (62.6–69.2 V) compared to the SMA4S51AH (51 V, 57.0–63.0 V). Its clamping voltage is also elevated at 90.9 V versus 82.8 V for the SMA4S51AH. This makes the SMA4S56AH appropriate for 48V nominal systems with wider transient margins, whereas the SMA4S51AH suits tighter 42–48V rails. Both share identical package, power rating, and AEC-Q101 qualification-enabling voltage-tiered design reuse of the SMA4S56AH footprint.