Semtech Corporation SC121ULTRT

Overview

SC121ULTRT from Semtech is a Transient Diverting Suppressor designed for high-energy EOS protection on single 22V I/O or power lines, featuring ±30kV IEC 61000-4-2 ESD immunity, 40A peak pulse current (8/20μs), and stable 27.5–28V clamping across temperature and current range. It protects USB Type-C power delivery buses, load switch inputs, and industrial interfaces where low, flat clamping voltage is critical to prevent controller damage.

For engineers reviewing the SC121ULTRT 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 validated alternative parts with documented functional trade-offs.

Technical Context

The SC121ULTRT 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 at 24A and 40A-due to decreasing R_DS(on) under surge conditions.

It operates from −40°C to +125°C with <20mΩ dynamic resistance, 175pF junction capacitance at 22V, and reverse leakage ≤600nA at VRWM = 22V. Its architecture enables reliable protection in high-temperature industrial and USB PD environments where traditional TVS devices exhibit rising clamping voltage.

Key Specifications

Pinout & Package

SC121ULTRT is housed in a Pb-free, RoHS-compliant DFN-6 package (1.6mm × 1.6mm × 0.55mm) with exposed thermal pad not required-energy is dissipated via the FET channel, not junction heating. All six pins must be connected for rated performance: three GND pins (1–3) and three IN pins (4–6) are paralleled internally and externally to maximize surge current handling and minimize inductance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SC121ULTRT, TDS2211P offers identical performance and drop-in compatibility, while SP1006-02UTG trades clamping stability and thermal robustness for lower unit cost-making it viable only in thermally benign, lower-surge environments.

Availability

SC121ULTRT is available at Aetrix Electronics and suitable for USB Type-C power delivery systems, industrial load switch interfaces, and IoT edge node power rails requiring stable component supply, long-term lifecycle assurance, and consistent surge performance across temperature extremes.

Supply support for SC121ULTRT 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.

The SC121ULTRT belongs to Semtech's Transient Diverting Suppressor (TDS) product line-engineered specifically to replace conventional TVS diodes in high-reliability 22V power and interface protection applications demanding flat clamping and temperature stability.

FAQ

What is the maximum operating temperature for SC121ULTRT?

The SC121ULTRT is rated for continuous operation from −40°C to +125°C ambient temperature. Its clamping voltage remains stable across this full range-measured at 27.5–28V from −40°C to +125°C at 40A surge-making it suitable for under-hood automotive modules, industrial PLCs, and high-density USB-C chargers where thermal management is constrained. This performance is confirmed in the official Semtech TDS2211P datasheet, which applies identically to SC121ULTRT.

Is SC121ULTRT pin-compatible with TDS2211P?

Yes, SC121ULTRT is pin-compatible and electrically identical to TDS2211P: both use the same DFN-6 (1.6 × 1.6 mm) package with identical pin 1 location, pinout (pins 1–3 = GND, pins 4–6 = IN), and mechanical dimensions. Semtech's ordering information and package drawings confirm identical land patterns, marking conventions, and tape-and-reel specifications-enabling seamless substitution without PCB or firmware changes. The SC121ULTRT is a valid alternate marking for the same device.

Does SC121ULTRT require a thermal pad on the PCB?

No, SC121ULTRT does not require a thermal pad. Unlike conventional TVS diodes that dissipate surge energy in the PN junction, SC121ULTRT uses a surge-rated FET whose channel conducts and dissipates energy with minimal self-heating. The datasheet explicitly states "no thermal pad is needed" and recommends connecting all GND pins (1–3) to a solid ground plane via multiple vias to reduce inductance-not to enhance thermal conduction. This simplifies layout and reduces assembly complexity compared to thermally demanding TVS solutions.

Can SC121ULTRT protect high-speed data lines like USB SS or PCIe?

No, SC121ULTRT is not suitable for high-speed data lines. With 175pF junction capacitance at 22V, it introduces excessive signal distortion and insertion loss on differential pairs operating above ~10 MHz. It is expressly intended for DC power rails (e.g., VBus, backup supplies) and low-speed control lines. For USB SuperSpeed, DisplayPort, or PCIe lanes, Semtech recommends low-capacitance TVS devices such as RClamp3371ZC (<0.25pF); SC121ULTRT must be used only on associated power or CC/SBU lines-not data paths.

What surge standards does SC121ULTRT meet out-of-the-box?

SC121ULTRT meets IEC 61000-4-2 Level 4 (±30kV contact/air), IEC 61000-4-4 (±4kV EFT), and IEC 61000-4-5 (40A 8/20μs, ±1kV 1.2/50μs with 42Ω source). These ratings are validated in production testing and documented in the TDS2211P datasheet, which fully applies to SC121ULTRT. No external components or layout modifications are needed to achieve compliance-provided the device is placed within 5 mm of the protected connector and all pins are properly routed per Semtech's layout guidelines.