Semtech Corporation SC418ULTRT

Overview

SC418ULTRT from Semtech is a transient diverting suppressor designed for high-energy EOS protection on 22V-rated power or I/O lines, featuring ±30kV IEC 61000-4-2 ESD immunity, 40A peak pulse current (8/20μs), 27.5–28V clamping voltage at 40A, and ultra-low 20mΩ dynamic resistance. It protects USB Type-C power delivery buses, load switch inputs, and industrial interfaces where stable clamping across temperature and current is critical.

For engineers reviewing the SC418ULTRT datasheet, pinout, applications, or equivalent options, this page delivers verified electrical specs, DFN-6 package layout guidance, real-world USB PD and load switch protection use cases, and two validated alternative parts with documented functional trade-offs.

Technical Context

The SC418ULTRT uses a surge-rated FET as its primary protection element, activated by a precision trigger circuit that turns on the shunt path when transient voltage exceeds breakdown. Unlike conventional TVS diodes, its clamping voltage remains nearly constant (27.5–28V) from 24A to 40A due to decreasing R_DS(on) under surge conditions.

It operates from –40°C to +125°C with <600nA reverse leakage at 22V, 175pF junction capacitance at 22V/1MHz, and is housed in a RoHS-compliant DFN 1.6×1.6×0.55mm package with six terminals-three dedicated GND pins (1–3) and three IN pins (4–6) requiring parallel connection for full 40A rating.

Key Specifications

Pinout & Package

SC418ULTRT is packaged in a Pb-free, halogen-free DFN 1.6mm × 1.6mm × 0.55mm 6-lead outline (UL 94V-0 molding compound), with exposed thermal pad not required - energy is dissipated in the FET channel, not the junction.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TDS2211P.C (identical function and form) and uClamp2411ZA.TCT (lower-power Zener TVS), SC418ULTRT delivers superior 40A surge handling and flat clamping essential for 22V power rail protection - making it the only viable option for USB PD 100W and industrial 24VDC systems requiring IEC 61000-4-5 compliance.

Availability

SC418ULTRT is available at Aetrix Electronics and suitable for USB Type-C power delivery systems, industrial PLC power inputs, and notebook DC-in protection requiring stable component supply, long-term lifecycle support, and guaranteed RoHS/WEEE compliance.

Supply support for SC418ULTRT 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

Semtech Corporation is a U.S.-based fabless semiconductor company specializing in analog and mixed-signal ICs for precision sensing, protection, and signal integrity.

SC418ULTRT belongs to Semtech's Transient Diverting Suppressor (TDS) product line, engineered to replace conventional TVS diodes in high-energy EOS applications where stable clamping, temperature independence, and FET-level surge robustness are mandatory.

FAQ

What is the maximum continuous operating voltage for SC418ULTRT?

The SC418ULTRT has a reverse stand-off voltage (V_RWM) of 22V, meaning it reliably blocks up to 22V DC or RMS AC without significant leakage. This makes SC418ULTRT ideal for protecting 20V USB PD VBUS lines and 24V industrial auxiliary rails where sustained voltage must remain below the device's threshold to avoid conduction or degradation.

Does SC418ULTRT require a thermal pad on the PCB?

No, SC418ULTRT does not require a thermal pad. Unlike TVS diodes that dissipate surge energy in the PN junction, SC418ULTRT uses a surge-rated FET whose channel conducts and dissipates energy with minimal temperature rise. The datasheet explicitly states "no thermal pad is needed," and layout guidelines emphasize low-inductance GND connections instead of thermal vias.

How does SC418ULTRT differ from standard TVS diodes in clamping behavior?

Standard TVS diodes exhibit linearly rising clamping voltage (V_C = V_BR + I_PP × R_DYN) due to fixed dynamic resistance. SC418ULTRT maintains ~27.5–28V clamping from 24A to 40A because its FET's R_DS(on) decreases under surge, resulting in near-constant V_C. This eliminates thermal derating and simplifies design margining for SC418ULTRT in high-temp environments.

Can SC418ULTRT be used on high-speed data lines like USB SuperSpeed?

No, SC418ULTRT is not suitable for USB SuperSpeed (SS), DP, or DM lines due to its 175pF junction capacitance, which would severely degrade signal integrity. It is intended exclusively for power or low-speed control lines (e.g., VBUS, CC, SBU). For SS lines, Semtech recommends low-capacitance devices like RClamp3371ZC (<0.25pF), not SC418ULTRT.

What is the recommended PCB layout for SC418ULTRT to achieve full 40A rating?

To achieve the full 40A peak pulse rating, all three IN pins (4–6) must be connected in parallel to the protected line via a single short, wide trace, and all three GND pins (1–3) must connect to a solid ground plane using multiple low-inductance vias. SC418ULTRT must be placed within 5mm of the connector - longer traces add parasitic inductance that raises clamping voltage during fast transients.