STMicroelectronics TN22-1500T

Overview

TN22-1500T from STMicroelectronics is a high-voltage, high-holding-current thyristor (SCR) designed specifically as the main switching element in fluorescent tube electronic starter circuits. It features a clamping breakdown voltage of 1200–1500 V, low gate trigger current (<1.5 mA), and high holding current (>175 mA), enabling reliable lamp ignition with minimal external drive power in line-powered AC starter topologies.

For engineers reviewing the TN22-1500T datasheet, TN22-1500T pinout, TN22-1500T application, or TN22-1500T equivalent, key selection criteria include its 1500 V V_BR rating, 2 A I_T(RMS), TO-220AB package thermal resistance (R_th(j-c) = 3 °C/W), dV/dt immunity (≥500 V/µs), and compatibility with sensitive SCR-based ignition control stages.

Technical Context

The TN22-1500T operates as a latching bidirectional switch triggered by gate current and maintained in conduction until current falls below its 175 mA minimum holding threshold. Its 1200–1500 V breakdown voltage ensures robust overvoltage clamping during inductive kick from the ballast inductor, directly protecting the fluorescent tube electrodes during ignition.

It functions within a two-stage starter sequence: first conducting continuously to preheat filaments via full-wave rectified mains current, then rapidly commutating off when the parallel SCR fires - inducing a high-voltage pulse across the tube. Its 50 A/µs critical dI/dt rating and 500 V/µs dV/dt immunity prevent false triggering under fast transients.

Key Specifications

Pinout & Package

TO-220AB package: Insulated tab (pin 2), anode (pin 1), cathode (pin 3). Mounting tab is electrically connected to pin 2 (anode) and serves as primary thermal path. Requires mechanical torque of 0.4–0.6 N·m for heatsink attachment.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fluorescent lamp starter switch applications.

Compared with TN22-1500H and S4006L, the TN22-1500T uniquely combines 1500 V clamping, 2 A RMS rating, and 3 °C/W thermal resistance in TO-220AB-enabling robust, self-contained, heatsink-cooled starter designs without gate buffering or derating.

Availability

TN22-1500T is available at Aetrix Electronics and suitable for fluorescent lamp starters, AC line-powered ignition modules, and ballast-integrated preheat controllers requiring stable component supply and long-life reliability.

Supply support for TN22-1500T 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, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The TN22 series belongs to ST's legacy power thyristor product line, engineered specifically for energy-efficient, maintenance-free fluorescent lighting control with emphasis on ignition reliability, thermal robustness, and long operational lifetime.

FAQ

What is the maximum allowable case temperature for continuous operation?

The TN22-1500T supports continuous operation up to T_c = 95 °C, as validated by its 2 A I_T(RMS) rating under those conditions. Exceeding this requires derating per Figure 2 in the datasheet; junction temperature must remain ≤110 °C to maintain specified holding current and dV/dt immunity.

Can TN22-1500T replace older TN22 variants like TN22-1200T?

Yes, the TN22-1500T is a direct upgrade with identical pinout and package but extended V_BR (1200–1500 V vs. 1200 V min). It maintains all original timing, gate, and thermal parameters, offering improved margin against voltage surges and tube aging without circuit redesign.

Is the TO-220AB tab electrically isolated from the leads?

No-the metal tab (pin 2) is internally connected to the anode (pin 1). Electrical isolation requires use of an insulating washer and shoulder washer during heatsink mounting. The device is not offered in insulated-tab variants.

Does TN22-1500T require a snubber circuit in typical starter applications?

No snubber is required in standard fluorescent starter topologies. Its 500 V/µs dV/dt rating and 1500 V V_BR provide sufficient margin against ballast-induced transients. Snubbers may be added only in unusually noisy environments or non-standard inductor designs with excessive ringing.