STMicroelectronics ST2111FX

Overview

ST2111FX from STMicroelectronics is a high-voltage, fast-switching NPN power transistor in ISOWATT218FX package, rated for V_CEO = 700 V, I_C = 12 A, and P_TOT = 65 W at T_C = 25°C. It features tight h_FE control (4.5–25), low V_CE(sat) = 3 V at I_C = 8 A/I_B = 2 A, and 2500 V_RMS insulation withstand voltage - designed for horizontal deflection circuits and switch-mode power supplies in CRT TVs.

For engineers reviewing the ST2111FX datasheet, ST2111FX pinout, ST2111FX application, or ST2111FX equivalent, key selection criteria include its 1500 V V_CES, 1.9 °C/W R_thJ-case, 2.3 µs storage time under inductive switching, and U.L.-compliant fully insulated package enabling direct heatsink mounting without isolation hardware.

Technical Context

The ST2111FX employs diffused collector technology to stabilize operation against base drive variations, minimizing worst-case power dissipation in high-repetition-rate horizontal deflection stages. Its ruggedness is enhanced via controlled saturation characteristics and improved thermal robustness up to T_J = 150°C.

Designed for hard-switched inductive loads (e.g., flyback transformers), it delivers 64 kHz switching capability with t_s = 2.3 µs and t_f = 0.16 µs under specified test conditions (I_C = 6 A, L_BB = 1.3 µH, V_BE(off) = −2.5 V), supporting reliable energy transfer in TV SMPS and deflection yoke drivers.

Key Specifications

Pinout & Package

Package: ISOWATT218FX - fully insulated, U.L.-compliant molded package with integral heatsink interface; lead-free per ECOPACK® standard.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BU2520DX and 2SD2571, the ST2111FX uniquely combines U.L.-rated insulation, 25 A peak current, and 1.9 °C/W thermal resistance - making it optimal for cost-sensitive, safety-certified TV deflection and SMPS where assembly simplicity and thermal headroom are critical.

Availability

ST2111FX is available at Aetrix Electronics and suitable for horizontal deflection circuits, switch-mode power supplies, and high-voltage relay drivers requiring stable component supply and long-lifecycle support.

Supply support for ST2111FX 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, designing and manufacturing analog, digital, and mixed-signal ICs and discrete devices for automotive, industrial, and consumer markets.

The ST2111FX belongs to ST's high-voltage power transistor family, engineered specifically for CRT television deflection and SMPS applications demanding ruggedness, insulation integrity, and repeatable switching behavior under thermal stress.

FAQ

What is the maximum allowable case temperature for continuous operation?

The ST2111FX has a maximum operating junction temperature of 150°C and a thermal resistance of 1.9°C/W. For continuous 65 W dissipation, the case temperature must remain at or below 25°C. In practice, derating is required above 25°C ambient; at T_C = 80°C, maximum usable power drops to approximately 34 W based on linear thermal model.

Can ST2111FX be used in avalanche mode?

No - the ST2111FX is not rated or characterized for repetitive avalanche operation. Its absolute maximum V_CES = 1500 V defines safe non-avalanche blocking; operation beyond V_CEO = 700 V with base open risks secondary breakdown. Designers must use snubbers or clamping to limit voltage transients within rated limits.

Is the ISOWATT218FX package RoHS-compliant?

Yes - the ST2111FX uses an ECOPACK®-compliant ISOWATT218FX package with lead-free second-level interconnect, meeting RoHS Directive 2011/65/EU. The inner box label and package marking indicate compliance per JEDEC Standard JESD97, including soldering profile limits.

What base drive current is required for full saturation at 12 A collector current?

Per datasheet Figure 5 and Table 3, full saturation at I_C = 8 A requires I_B = 2 A. Extrapolating conservatively using h_FE(min) = 4.5, achieving I_C = 12 A demands ≥2.7 A base current. However, due to h_FE degradation at high current, a 3–3.5 A peak base drive is recommended for reliable hard saturation across temperature and process variation.