onsemi SMMJT350T1G

Overview

SMMJT350T1G from onsemi is a PNP silicon bipolar power transistor designed for line-operated series pass and switching regulators, featuring 300 V_CEO, 0.5 A continuous collector current, 2.75 W power dissipation at T_C = 25°C, and SOT-223 package - used in low-power AC/DC offline regulator output stages.

For engineers reviewing the SMMJT350T1G datasheet, pinout, applications, or equivalent options, key selection criteria include high V_CEO sustain capability, DC current gain (h_FE = 30–240 at I_C = 50–100 mA), thermal resistance (R_JC = 45°C/W), Pb-free RoHS compliance, and AEC-Q101 qualification for automotive-grade reliability.

Technical Context

The SMMJT350T1G operates as a medium-voltage, medium-current PNP switch or linear pass element in unregulated or feedback-controlled power supplies. Its 300 V_CEO rating enables direct use across 230 VAC rectified rails, while its h_FE range supports stable base drive design across temperature (–55°C to +150°C).

Thermal performance is defined by junction-to-case resistance of 45°C/W and safe operating area limited by second breakdown and thermal constraints. The device exhibits low leakage (I_CBO, I_EBO ≤ 100 nA) and V_BE(sat) ≤ 0.8 V at I_C/I_B = 10, enabling efficient base control in low-quiescent designs.

Key Specifications

Pinout & Package

SMMJT350T1G is housed in a surface-mount SOT-223 (Case 318E, Style 1) package with exposed collector tab for thermal conduction and mechanical anchoring.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP bipolar power transistor applications.

Compared with MJD2955T4G and ZTX951, the SMMJT350T1G uniquely balances 300 V capability, SOT-223 mountability, and AEC-Q101 qualification - making it optimal for compact, mains-connected, automotive-qualified PNP switching or regulation where thermal budget is moderate and voltage stress is high.

Availability

SMMJT350T1G is available at Aetrix Electronics and suitable for AC/DC offline regulators, automotive body control modules, and industrial sensor power supplies requiring stable component supply, long-lifecycle support, and automotive-grade reliability.

Supply support for SMMJT350T1G 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier focused on energy-efficient electronics, with leadership in power management, analog, sensing, and connectivity solutions.

The MMJT350 family is part of onsemi's bipolar power transistor portfolio engineered for robust line-operated power conversion - specifically targeting cost-effective, reliable PNP switching and regulation in safety-critical and thermally constrained applications.

FAQ

What is the maximum continuous collector current rating for the SMMJT350T1G?

The SMMJT350T1G has a maximum continuous collector current (I_C) of 0.5 A at T_C = 25°C. This rating decreases with rising case temperature - derating begins at 22 mW/°C above 25°C. At T_C = 100°C, usable I_C drops to approximately 0.35 A. Designers must verify thermal design using R_JC = 45°C/W and actual PCB copper area to maintain safe junction temperature.

Is the SMMJT350T1G suitable for automotive applications?

Yes, the SMMJT350T1G is AEC-Q101 qualified and PPAP capable, making it suitable for automotive applications such as body control modules, lighting drivers, and power distribution units. Its –55°C to +150°C junction temperature range, Pb-free RoHS compliance, and UL 94 V-0 epoxy meet stringent automotive reliability and safety requirements.

What is the pin configuration of the SMMJT350T1G in the SOT-223 package?

The SMMJT350T1G uses a standard SOT-223 pinout: Pin 1 = Base, Pin 2 = Collector, Pin 3 = Emitter, and the exposed metal tab (Pin 4) is electrically connected to the Collector. This configuration enables straightforward PCB layout with the collector tab soldered directly to a thermal pad for effective heat dissipation.

Does the SMMJT350T1G have built-in ESD protection?

The SMMJT350T1G meets ESD Human Body Model (HBM) Class 3B (≥8 kV) and Machine Model (MM) Class C (≥1 kV) per JESD22-A114 and JESD22-A115. These ratings reflect intrinsic device-level robustness - no external ESD diodes are required for typical handling and assembly, though system-level protection remains recommended in high-noise environments.

How does the DC current gain (h_FE) of the SMMJT350T1G vary with operating conditions?

The SMMJT350T1G specifies h_FE = 30 (min) at I_C = 50 mA and h_FE = 20 (min) at I_C = 100 mA, both measured at V_CE = 10 V and T_J = 25°C. Gain decreases at higher current and temperature; Figure 1 in the datasheet shows h_FE dropping to ~50% of room-temperature value at T_J = 150°C. Designers should size base resistors using worst-case h_FE to ensure saturation.