STMicroelectronics STQ3NK50ZR-AP

Overview

STQ3NK50ZR-AP from STMicroelectronics is a Zener-protected N-channel SuperMESH™ MOSFET rated for 500 V drain-source voltage, 2.8 Ω typical R_DS(on) at V_GS = 10 V, and 0.5 A continuous drain current at T_C = 25°C, housed in TO-92 (Ammopak) package. It delivers high dv/dt capability (4.5 V/ns), 100% avalanche tested performance, and integrated gate-source Zener protection for robust operation in low-power AC-DC converters.

For engineers reviewing the STQ3NK50ZR-AP datasheet, STQ3NK50ZR-AP pinout, STQ3NK50ZR-AP application, or STQ3NK50ZR-AP equivalent, this device is selected for compact, cost-sensitive high-voltage switching where ESD resilience, gate transient immunity, and thermal reliability on FR4 boards are critical design requirements.

Technical Context

This MOSFET employs ST's optimized strip-based PowerMESH™ layout to achieve low on-resistance while preserving exceptional dv/dt immunity-critical for fast-switching flyback and resonant topologies. Its built-in back-to-back gate-source Zener diodes (±30 V breakdown) eliminate external clamping components and enhance system-level ESD robustness (HBM 2000 V).

The device operates with a gate threshold voltage of 3.0–4.5 V and exhibits low total gate charge (11 nC), enabling efficient drive with standard logic-level controllers. Its safe operating area (SOA) is validated up to 2.3 A pulsed current under unclamped inductive load conditions, supporting reliable energy recovery in SMPS snubber networks.

Key Specifications

Pinout & Package

STQ3NK50ZR-AP uses the TO-92 (Ammopak) package-a through-hole, three-terminal plastic case with lead spacing optimized for automated insertion and wave soldering. The package provides mechanical stability and moderate thermal dissipation for low-power applications.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage, low-current MOSFET applications.

Compared with STD3NK50Z and STD3NK50Z-1, STQ3NK50ZR-AP offers the smallest footprint and lowest assembly cost for sub-3 W designs, while trading off current capacity and thermal headroom-making it optimal for space-constrained, ultra-low-cost AC-DC stages.

Availability

STQ3NK50ZR-AP is available at Aetrix Electronics and suitable for AC adaptors, battery chargers, lighting drivers, and industrial control power supplies requiring stable component supply and long-term manufacturability.

Supply support for STQ3NK50ZR-AP 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, digital, and mixed-signal ICs, discrete devices, and MEMS for automotive, industrial, and consumer markets.

This device belongs to ST's SuperMESH™ high-voltage MOSFET product line, engineered specifically for efficiency, ruggedness, and integration in cost-sensitive offline power conversion systems up to 5 W.

FAQ

What is the maximum gate-source voltage rating for STQ3NK50ZR-AP?

The absolute maximum gate-source voltage is ±30 V, enforced by internal back-to-back Zener diodes. This protects the gate oxide from overvoltage during drive transients or ESD events. Operation beyond this rating risks permanent gate damage, even if brief. Drive circuits must be designed to clamp gate voltage within this window, especially during hot-plug or startup conditions.

Can STQ3NK50ZR-AP replace STD3NK50Z in an existing DPAK-based design?

No-it cannot be used as a direct replacement due to fundamental differences: TO-92 vs. DPAK package, 0.5 A vs. 2.3 A continuous current rating, and 3 W vs. 45 W power dissipation capability. Mechanical mounting, PCB layout, thermal design, and SOA margins would all require redesign. Only consider substitution after full electrical and thermal revalidation.

Is the STQ3NK50ZR-AP suitable for use in a 100 kHz flyback converter?

Yes-its 11 nC total gate charge and 4.5 V/ns dv/dt capability support stable 100 kHz operation in discontinuous conduction mode (DCM) flyback converters. However, switching losses increase at higher frequencies; thermal performance must be verified on the target board using its measured R_thj-amb of 120 °C/W under actual load and airflow conditions.

Does STQ3NK50ZR-AP include body diode recovery specifications?

Yes-the datasheet specifies source-drain diode parameters: forward voltage V_SD = 1.6 V at I_SD = 2.3 A, reverse recovery time t_rr = 250 ns at T_j = 25°C, and Q_rr = 745 µC. These values are measured under standardized inductive test conditions (di/dt = 100 A/µs, V_DD = 40 V) and inform snubber design and EMI filtering in flyback and LLC topologies.