STMicroelectronics STF21N90K5

Overview

STF21N90K5 from STMicroelectronics is a high-voltage N-channel Power MOSFET using MDmesh K5 technology, rated for 900 V V_DS, 299 mΩ R_DS(on) max at V_GS = 10 V and 9 A, with 18.5 A continuous drain current (T_C = 25 °C). It features ultra-low gate charge (43 nC), 100% avalanche tested operation, and Zener-protected gate, targeting high-efficiency switch-mode power supplies in industrial AC-DC converters.

For engineers reviewing the STF21N90K5 datasheet, STF21N90K5 pinout, STF21N90K5 application, or STF21N90K5 equivalent, key selection criteria include its 900 V breakdown voltage, TO-220FP package thermal resistance (R_thJC = 3.13 °C/W), 74 A pulsed drain capability, and low C_oss (112 pF) for hard-switching PFC stages.

Technical Context

This device implements a proprietary vertical MDmesh K5 structure to minimize conduction and switching losses simultaneously. Its 43 nC total gate charge and 25 nC gate-drain charge enable fast, low-loss turn-off in high-frequency (>100 kHz) topologies while maintaining ruggedness under unclamped inductive switching.

The integrated Zener-protected gate ensures ±30 V V_GS tolerance and robust ESD immunity. Avalanche capability is validated to 6 A repetitive I_AR and 200 mJ single-pulse E_AS, supporting reliable operation in flyback and resonant converters without external snubbers.

Key Specifications

Pinout & Package

STF21N90K5 is housed in a TO-220FP (Full-Pak) package with insulated tab, offering enhanced creepage/clearance versus standard TO-220 and simplified mounting without insulating washers.

Key Features

Applications

Equivalent & Alternatives

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

Compared with STP21N90K5, STF21N90K5 trades 2.63 °C/W higher junction-to-case thermal resistance for simplified assembly and reinforced isolation; versus IXTH20N90L2, it delivers 34% lower gate charge and 10% lower R_DS(on), directly improving light-load efficiency and thermal headroom in high-frequency PFC.

Availability

STF21N90K5 is available at Aetrix Electronics and suitable for industrial AC-DC power supplies, server rectifiers, and renewable energy converters requiring stable component supply and long-term production continuity.

Supply support for STF21N90K5 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 and discrete power devices for industrial, automotive, and consumer markets.

STF21N90K5 belongs to the MDmesh K5 high-voltage Power MOSFET product line, engineered specifically for high-efficiency, high-power-density switch-mode power conversion in 600–1000 V applications.

FAQ

What is the maximum recommended gate drive voltage for STF21N90K5?

The absolute maximum gate-source voltage is ±30 V, but ST specifies optimal linear operation and longevity at V_GS = 10 V for R_DS(on) characterization. Driving above 15 V provides no significant R_DS(on) improvement and increases risk of gate oxide stress during transients; 12 V is the practical upper limit for robust industrial designs.

Can STF21N90K5 replace STW21N90K5 in a TO-247-based design?

No - STF21N90K5 uses a TO-220FP package with insulated tab and R_thJC = 3.13 °C/W, while STW21N90K5 is in TO-247 with R_thJC = 0.5 °C/W. Direct replacement would cause thermal runaway at >100 W dissipation due to 6× higher junction-to-case resistance; board layout, heatsink interface, and gate drive loop inductance must all be requalified.

Does STF21N90K5 include an integrated body diode suitable for synchronous rectification?

Yes - it features a fast-recovery source-drain diode with t_rr = 548 ns at T_J = 25 °C and Q_rr = 12 µC, rated for 18.5 A continuous and 74 A pulsed current. However, its V_SD = 1.5 V forward drop is higher than dedicated SiC Schottky diodes, so it is suitable for freewheeling and clamping but not primary synchronous rectification in high-efficiency LLC designs.

What is the safe operating area (SOA) limitation at 100 °C case temperature?

At T_C = 100 °C, the continuous drain current is derated to 11.6 A per Table 1. The SOA curve (Figure 3) shows that operation above 10 A at V_DS > 200 V is limited by second breakdown beyond 100 µs pulse width; for 1 ms pulses, the maximum sustainable V_DS drops to ~120 V at 10 A, requiring careful snubber design in hard-switched inverters.