Taiwan Semiconductor Corporation US1B

Overview

US1B from Taiwan Semiconductor is a 1 A, 100 V ultrafast surface-mount rectifier diode in DO-214AC (SMA) package, featuring 1.0 V forward voltage at 1 A and 50 ns reverse recovery time. It serves as a freewheeling or snubber diode in DC-DC converters and switching inverters where low conduction loss and fast turn-off are critical.

For engineers reviewing the US1B datasheet, US1B pinout, US1B application, or US1B equivalent, key selection criteria include its 100 V repetitive peak reverse voltage, 30 A surge rating, glass-passivated junction, RoHS/halogen-free compliance, and suitability for automated SMT assembly.

Technical Context

The US1B operates as a single-die, unidirectional silicon rectifier with cathode-band polarity marking. Its ultrafast recovery (trr ≤ 50 ns) enables high-frequency switching up to several hundred kHz in SMPS topologies, while the 27 °C/W junction-to-lead thermal resistance supports reliable power dissipation under pulsed load conditions.

Designed for surface-mount use in space-constrained power stages, the US1B maintains stable reverse leakage (≤5 µA at 25°C, ≤150 µA at 125°C) and exhibits low junction capacitance (15 pF at 4 V), minimizing switching node oscillation and EMI generation in flyback and buck-derived converters.

Key Specifications

Pinout & Package

DO-214AC (SMA) package: molded epoxy case, matte tin-plated leads, cathode indicated by band, moisture sensitivity level 1, weight ≈ 0.060 g.

Key Features

Applications

Equivalent & Alternatives

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

Compared with STTH1R04 and ES1B, the US1B offers the lowest forward voltage in its voltage class among DO-214AC ultrafast rectifiers, making it optimal for thermally constrained, high-efficiency 100 V DC-DC stages where conduction loss dominates total loss budget.

Availability

US1B is available at Aetrix Electronics and suitable for DC-DC converters, switching inverters, and lighting applications requiring stable component supply, consistent parametric performance, and full RoHS/halogen-free compliance.

Supply support for US1B 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 devices, and MOSFETs for industrial and consumer markets.

The US1B belongs to TSC's US1x ultrafast rectifier family, engineered specifically for high-frequency switching power supplies where low VF, fast trr, and robust SMT reliability are mandatory design requirements.

FAQ

What is the maximum repetitive peak reverse voltage (VRRM) rating for US1B?

The US1B has a VRRM rating of 100 V, meaning it can reliably block up to 100 V of reverse voltage in repetitive operation. This value is confirmed in the Absolute Maximum Ratings table on page 1 of the N2102 datasheet and defines the upper limit for use in clamp, snubber, and freewheeling circuits where transient spikes must be contained. Exceeding 100 V risks avalanche breakdown and permanent damage to the US1B.

Does US1B have a specified reverse recovery time (trr), and how is it measured?

Yes, the US1B has a maximum reverse recovery time (trr) of 50 ns, measured under IF = 0.5 A, IR = 1.0 A, and Irr = 0.25 A per JEDEC test conditions. This parameter is critical for high-frequency switching efficiency and is validated in the Electrical Specifications table on page 2 of the N2102 datasheet. The 50 ns trr directly impacts switching loss and EMI in converters operating above 100 kHz.

Is US1B compatible with lead-free reflow soldering processes?

Yes, the US1B is fully compatible with lead-free reflow soldering. Its matte tin-plated leads meet J-STD-002 solderability requirements, and the DO-214AC (SMA) package is rated for moisture sensitivity level 1 (MSL-1), allowing unlimited floor life before reflow. The device supports peak reflow temperatures up to 260°C per J-STD-020, making it suitable for standard Pb-free assembly lines without baking or special handling.

What is the junction-to-ambient thermal resistance (RθJA) for US1B, and how does it affect PCB layout?

The US1B has an RθJA of 75 °C/W under standard JEDEC test conditions (single-layer 1 in² copper pad). This value indicates moderate self-heating under full 1 A load; however, its lower RθJL (27 °C/W) means thermal performance improves significantly with copper pour under both leads. For sustained 1 A operation, designers should extend cathode and anode pads to ≥25 mm² each to approach the RθJL-limited thermal ceiling.

Can US1B replace US1A or US1D in an existing design?

US1B is not a direct replacement for US1A (50 V) or US1D (200 V) due to differing VRRM ratings. While all share identical package, VF, and trr, substituting US1B for US1A risks overvoltage failure in 50 V systems, and using it in place of US1D may compromise safety margin in 200 V applications. Always verify reverse voltage stress margins before interchanging any US1x variant, including US1B.