STMicroelectronics STF21NM50N

Overview

STF21NM50N from STMicroelectronics is an N-channel 500 V, 18 A, 0.15 Ω R_DS(on) Power MOSFET in TO-220FP package, built on second-generation MDmesh™ technology. It delivers low gate charge (65 nC), high avalanche ruggedness (480 mJ E_AS), and fast switching (t_r = 18 ns) for high-efficiency offline SMPS in industrial power supplies and AC-DC adapters.

For engineers reviewing the STF21NM50N datasheet, STF21NM50N pinout, STF21NM50N application, or STF21NM50N equivalent, key selection criteria include its 500 V V_DSS, 0.15 Ω R_DS(on) at V_GS = 10 V, 65 nC total gate charge, 15 V/ns dv/dt capability, and TO-220FP thermal resistance of 4.21 °C/W - all critical for hard-switched PFC and LLC resonant converter designs.

Technical Context

This MOSFET employs ST's second-generation MDmesh™ vertical structure with strip layout to minimize conduction and switching losses simultaneously. Its 1950 pF C_iss and 60 pF C_rss support stable high-frequency operation up to 300 kHz in continuous conduction mode (CCM) PFC stages.

The device integrates a fast-recovery body diode (t_rr = 360 ns, Q_rr = 5 µC at T_j = 25°C) with low V_SD = 1.5 V, enabling efficient synchronous rectification replacement in flyback and forward converters without external Schottky assistance.

Key Specifications

Pinout & Package

STF21NM50N uses the TO-220FP (Full-Pak) package: insulated plastic case with internal heat sink tab, optimized for surface-mount-compatible through-hole assembly and improved thermal isolation. Pin 1 = Gate, Pin 2 = Drain (tab-connected), Pin 3 = Source.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage power switching applications.

Compared with IPP60R190C6, STF21NM50N trades 13 nC higher gate charge for 0.04 Ω lower R_DS(on) and certified 2500 V isolation - making it superior for thermally constrained, safety-critical industrial SMPS. Against STP21NM50N, it sacrifices 3.32 °C/W higher junction-to-case resistance for guaranteed creepage and simplified assembly.

Availability

STF21NM50N is available at Aetrix Electronics and suitable for industrial AC-DC power supplies, LED streetlight drivers, and telecom rectifiers requiring stable component supply, long-term lifecycle support, and RoHS-compliant sourcing.

Supply support for STF21NM50N 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 power management applications.

STF21NM50N belongs to the MDmesh™ Power MOSFET product line, engineered specifically for high-efficiency, high-voltage switching in offline power conversion systems where low R_DS(on) × Q_g and avalanche ruggedness are critical.

FAQ

What is the maximum continuous drain current for STF21NM50N at 100°C case temperature?

The maximum continuous drain current is 11 A at T_C = 100°C, as specified in Table 1 of the datasheet. This derating reflects thermal limits of the TO-220FP package, which has a junction-to-case thermal resistance of 4.21 °C/W. Operation above this current requires forced-air cooling or reduced ambient temperature to maintain T_j ≤ 150°C.

Does STF21NM50N require a gate resistor for stability in hard-switched applications?

Yes - a 10–22 Ω series gate resistor is recommended to dampen ringing caused by PCB trace inductance and the device's 1.6 Ω intrinsic gate resistance. The 60 pF C_rss and 1950 pF C_iss create a resonant loop with typical gate drive traces; omitting the resistor risks shoot-through or electromagnetic interference exceeding CISPR-22 Class B limits.

Can STF21NM50N replace STP21NM50N in an existing design without layout changes?

No - although both share identical die characteristics, STF21NM50N uses TO-220FP (insulated tab), while STP21NM50N uses standard TO-220 (conductive tab). Direct substitution requires verifying creepage distance, heatsink isolation, and mounting hardware, as the FP variant eliminates need for mica washers but increases thermal resistance by 3.32 °C/W.

What is the safe operating area (SOA) limitation for single-pulse avalanche operation?

The device supports single-pulse avalanche energy up to 480 mJ at T_j = 25°C, with I_AS = 9 A. SOA curves (Figure 1) confirm it can sustain 18 A at 400 V for ≤10 µs in repetitive switching, but pulse width must be limited by junction temperature rise - exceeding 150°C risks permanent parametric shift or bond-wire failure.