STMicroelectronics STP3NK50Z

Overview

STP3NK50Z from STMicroelectronics is a Zener-protected N-channel SuperMESH Power MOSFET in TO-220 package, rated for 500 V drain-source voltage, 2.8 Ω typical R_DS(on), and 2.3 A continuous drain current at T_C = 25 °C. It delivers high dv/dt capability (4.5 V/ns), 100% avalanche tested performance (E_AS = 120 mJ), and gate charge minimized to 11 nC - deployed in offline SMPS primary-side switching.

For engineers reviewing the STP3NK50Z datasheet, STP3NK50Z pinout, STP3NK50Z application, or STP3NK50Z equivalent, key selection criteria include avalanche ruggedness, Zener-protected gate integrity, TO-220 thermal resistance (R_thJC = 2.78 °C/W), and verified unclamped inductive switching behavior under 500 V bus conditions.

Technical Context

This device implements ST's SuperMESH process - an evolution of PowerMESH - optimizing cell pitch and drift region doping to reduce R_DS(on) while preserving high-voltage blocking (V_(BR)DSS = 500 V min). Its Zener-protected gate structure clamps transient overvoltage to ±30 V, enabling robust operation in noisy flyback or resonant converter environments.

The MOSFET exhibits low output capacitance (C_oss = 42 pF typ.) and reverse transfer capacitance (C_rss = 8 pF typ.), supporting fast switching with measured t_d(off) = 24 ns and t_f = 14 ns under 4.7 Ω gate drive. Its intrinsic body diode shows t_rr = 250 ns and Q_rr = 0.745 µC at 2.3 A, suitable for discontinuous conduction mode (DCM) topologies.

Key Specifications

Pinout & Package

TO-220 package with isolated tab (drain-connected); standard 3-pin vertical mounting configuration. Tab serves as thermal and electrical connection to drain terminal.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage N-channel MOSFET applications.

Compared with STP2NK50Z, STP3NK50Z offers +15% current capacity and −21% R_DS(on); versus IPP50R190C7, it trades 92× higher R_DS(on) for guaranteed avalanche ruggedness and gate Zener - critical for cost-sensitive, low-volume industrial supplies.

Availability

STP3NK50Z is available at Aetrix Electronics and suitable for AC-DC adapters, flyback SMPS, LED driver power stages, and industrial control power supplies requiring stable component supply across extended production lifecycles.

Supply support for STP3NK50Z 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 analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

STP3NK50Z belongs to the SuperMESH Power MOSFET product line, engineered specifically for rugged, cost-optimized high-voltage switching in offline power conversion - emphasizing avalanche reliability, gate robustness, and thermal efficiency in TO-220 form factor.

FAQ

Is STP3NK50Z suitable for zero-voltage switching (ZVS) topologies?

No - STP3NK50Z is optimized for hard-switched applications like DCM flyback and basic forward converters. Its body diode recovery time (t_rr = 250 ns) and Q_rr = 0.745 µC are not characterized for ZVS soft-recovery; dedicated superjunction or SiC devices are recommended for resonant LLC or phase-shifted full-bridge designs.

What is the maximum safe operating area (SOA) at T_C = 100 °C?

At T_C = 100 °C, the continuous DC SOA limit is 1.45 A at V_DS = 500 V (per datasheet Table 1). For pulse operation, the 10 ms boundary supports up to 2.3 A at 250 V, constrained by R_DS(on) and thermal saturation - see Figure 1 in DS9873 for full SOA curves.

Does the TO-220 tab require electrical isolation from heatsink?

Yes - the metal tab is internally connected to the drain (Pin 2), so electrical isolation using mica or polymer insulator kits is mandatory when mounting to a grounded heatsink. Failure to isolate risks short-circuiting the high-voltage drain node to system ground.

Can STP3NK50Z replace STP3NK60Z in existing designs?

No - STP3NK60Z has 600 V rating and higher R_DS(on) (3.6 Ω max). Substituting STP3NK50Z in 600 V designs violates V_DS derating rules (e.g., 80% rule yields 480 V max), risking catastrophic failure during line surges or reflected transients above 480 V.