Taiwan Semiconductor Corporation S4A

Overview

S4A from Taiwan Semiconductor is a 4A, 50V surface-mount silicon rectifier diode in DO-214AB (SMC) package, featuring glass-passivated junction, low forward voltage drop (max 1.15 V at 4 A), high surge capability (100 A IFSM), and operation up to 150°C junction temperature - used in AC/DC front-end stages of compact SMPS and LED drivers.

For engineers reviewing the S4A datasheet, S4A pinout, S4A application, or S4A equivalent, key selection criteria include repetitive peak reverse voltage (50 V), thermal resistance (R_θJL = 13 °C/W), moisture sensitivity level (MSL 1), RoHS/halogen-free compliance, and tape-and-reel packaging for automated assembly.

Technical Context

The S4A is a single-die, standard recovery rectifier with 1500 ns reverse recovery time (trr) under IF = 0.5 A / IR = 1.0 A conditions, optimized for cost-sensitive, medium-frequency switching applications where fast recovery is not required. Its 60 pF junction capacitance and 10 µA max reverse leakage at 25°C support stable operation in flyback and buck-derived topologies.

Thermally, the DO-214AB package delivers R_θJA = 47 °C/W (free air) and R_θJL = 13 °C/W (lead-to-junction), enabling reliable 4 A continuous conduction without forced cooling in ambient temperatures up to 75°C - validated per JESD201 Class 2 whisker testing and UL 94V-0 molding compound.

Key Specifications

Pinout & Package

Package: DO-214AB (SMC), surface-mount, cathode-indicated by band, matte tin-plated leads, MSL Level 1, weight ≈ 0.210 g.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar rectifier applications.

Compared with MUR420 and VS-4EYH05-M3, the S4A offers optimal balance of cost, thermal performance (R_θJL = 13 °C/W), and manufacturability (MSL 1, tape-and-reel) for 50–100 kHz SMPS where ultrafast recovery is unnecessary.

Availability

S4A is available at Aetrix Electronics and suitable for switching mode power supplies, LED lighting drivers, and AC/DC adapters requiring stable component supply, consistent MSL 1 handling, and RoHS-compliant production.

Supply support for S4A 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, specializing in power rectifiers, TVS diodes, MOSFETs, and ICs since 1979.

The S4A belongs to TSC's S4x series of surface-mount general-purpose rectifiers, engineered for high-volume, cost-sensitive AC/DC conversion in consumer and industrial power supplies - emphasizing reliability, automated assembly readiness, and thermal robustness.

FAQ

What is the maximum repetitive peak reverse voltage (V_RRM) for the S4A?

The S4A has a V_RRM of 50 V, meaning it can reliably block up to 50 V of reverse voltage in repetitive operation. This rating is confirmed in the Absolute Maximum Ratings table on page 1 of the K2102 datasheet. The S4A is intended for low-voltage AC/DC inputs such as 36 VAC RMS systems, where this 50 V rating provides adequate safety margin. Exceeding this voltage risks avalanche breakdown and permanent damage to the S4A.

Does the S4A have a specified reverse recovery time (trr), and how does it affect circuit performance?

Yes, the S4A has a typical reverse recovery time (trr) of 1500 ns under IF = 0.5 A, IR = 1.0 A, and Irr = 0.25 A test conditions. This standard recovery speed makes the S4A appropriate for switching frequencies up to approximately 100 kHz. At higher frequencies, excessive switching losses and EMI may occur. The S4A datasheet explicitly lists trr in the Electrical Specifications table, confirming its suitability for conventional flyback and forward converter topologies - not ultrafast or resonant designs.

What is the thermal resistance from junction to lead (R_θJL) for the S4A, and why does it matter in layout design?

The S4A has a junction-to-lead thermal resistance (R_θJL) of 13 °C/W, measured per JEDEC standards. This low value indicates efficient heat transfer from the die directly to the PCB copper via the leads. In layout, this means designers should maximize copper area connected to both anode and cathode pads - especially the cathode - to exploit this path. Doing so allows the S4A to sustain its full 4 A rating at T_L = 75°C without additional heatsinking, unlike devices with higher R_θJL.

Is the S4A compliant with RoHS and halogen-free requirements, and where is this documented?

Yes, the S4A is RoHS compliant and halogen-free per IEC 61249-2-21, as stated in the Features section on page 1 of the K2102 datasheet. The "RoHS Compliant" and "Halogen-free" bullet points are explicit and unconditional for the entire S4x family, including the S4A. No exemptions apply, and the device carries full material declarations supporting compliance for export to EU, China, and Korea markets.

What packaging format is available for the S4A, and what is the standard reel quantity?

The S4A is supplied in tape-and-reel packaging per the Ordering Information table on page 2 of the K2102 datasheet. The standard reel contains 3,000 units, compatible with industry-standard 12 mm carrier tape and EIA-481-2 orientation. The cathode band is consistently oriented toward the sprocket holes, ensuring correct automated placement. This packaging supports high-yield pick-and-place operations and meets J-STD-020 MSL Level 1 handling requirements without dry pack or baking.