STMicroelectronics SMP50-320

Overview

SMP50-320 from STMicroelectronics is a bidirectional Trisil™ thyristor surge protection device designed for primary overvoltage crowbar clamping in telecom line interfaces. It features a 320 V stand-off voltage (VRM), 400 V dynamic breakover voltage (VBO), 12 mA minimum holding current (IH), 25 pF capacitance at 50 V, and 50 A repetitive peak pulse current (10/1000 µs). It is used in xDSL line cards and central office equipment to meet GR-1089 Core Level 1 and ITU-T K20/K21 lightning immunity requirements.

For engineers reviewing the SMP50-320 datasheet, SMP50-320 pinout, SMP50-320 application, or SMP50-320 equivalent, this device is selected for high-energy bidirectional transient suppression where fail-safe short-circuit behavior, low leakage (<2 µA), and UL497B/UL94 V0 compliance are required in telecom infrastructure designs.

Technical Context

The SMP50-320 operates as a voltage-triggered bidirectional thyristor, latching into low-impedance conduction once VBO is exceeded and remaining on until current falls below IH. Its junction-to-ambient thermal resistance is 120 °C/W in SMA package with recommended footprint, enabling sustained energy handling under repeated surges.

It meets multiple telecom surge standards including GR-1089 Core (2500 V, 10/1000 µs), ITU-T K20 (6000 V, 10/700 µs), and FCC Part 68 Type A (1500 V, 10/160 µs), requiring no external series resistor for some test levels due to its robust Ipp rating and intrinsic clamping stability.

Key Specifications

Pinout & Package

The SMP50-320 is housed in an SMA (JEDEC DO-214AC) surface-mount package with two terminals: Anode (A) and Cathode (K). The package measures 2.25–2.90 mm (D) × 4.80–5.35 mm (E) × 0.75–1.50 mm (L), optimized for FR4 PCBs with thermal pad layout per Figure 12.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar bidirectional telecom surge protection applications.

Compared with SMTPA320 and TPA320, the SMP50-320 offers the smallest PCB footprint (SMA), highest mounting density, and optimal thermal performance for high-volume SMT production-making it the preferred choice for next-generation compact DSLAM and VoIP gateway designs.

Availability

SMP50-320 is available at Aetrix Electronics and suitable for DSL line card protection, ISDN terminal interface design, and central office equipment requiring stable component supply, long-lifecycle support, and certified telecom surge immunity.

Supply support for SMP50-320 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing silicon solutions for automotive, industrial, and communications markets since 1987.

The Trisil™ product line was developed specifically for fail-safe, high-energy transient protection in telecom infrastructure-targeting GR-1089, ITU-T K-series, and FCC Part 68 compliance in analog and digital line interface applications.

FAQ

What is the fail-safe behavior of SMP50-320 during end-of-life?

The SMP50-320 fails in a short-circuit mode, maintaining low-impedance clamping even after exceeding its rated surge endurance. This ensures continued overvoltage protection rather than open-circuit failure, which could expose downstream components to unclamped transients-a critical requirement for telecom central office and DSLAM reliability standards.

Can SMP50-320 be used without a series current-limiting resistor?

Yes-SMP50-320 can operate without an external series resistor for many standard tests, including GR-1089 Core Level 1 (2500 V, 10/1000 µs) and FCC Part 68 Type A (1500 V, 10/160 µs), due to its 50 A IPP rating and inherent holding current (12 mA min) that sustains conduction until surge energy dissipates.

How does SMP50-320 differ from standard TVS diodes in telecom protection?

Unlike unidirectional or bidirectional TVS diodes, SMP50-320 is a thyristor-based crowbar device with latching behavior: once triggered, it remains conductive until current drops below 12 mA. This provides lower clamping voltage under high-current surges and eliminates leakage-dependent voltage drift-key for stable protection in 48 V phantom-powered telecom lines.

Is SMP50-320 RoHS-compliant and halogen-free?

Yes-SMP50-320 is supplied in ST's ECOPACK® package with lead-free second-level interconnect, compliant with RoHS Directive 2011/65/EU and halogen-free per IEC 61249-2-21. The UL94 V0 epoxy housing contains no brominated flame retardants, meeting environmental requirements for telecom infrastructure deployed globally.