STMicroelectronics T635T-8T

Overview

T635T-8T from STMicroelectronics is a 6 A, 800 V snubberless triac in TO-220AB package, designed for quadrant I/II/III AC phase-angle and on/off switching. It delivers 45 A non-repetitive surge current (50 Hz), 2000 V/µs dV/dt immunity at 125 °C, and operates junction-temperature up to 150 °C - enabling robust motor control and lighting load switching without external snubbers.

For engineers reviewing the T635T-8T datasheet, T635T-8T pinout, T635T-8T application, or T635T-8T equivalent, key selection criteria include commutation robustness (dI/dt)c ≥ 6 A/ms at 125 °C, gate trigger current ≤ 35 mA, and thermal resistance Rth(j-c) = 2.1 °C/W for heatsink-integrated AC power control designs.

Technical Context

This triac supports three-quadrant triggering (QI, QII, QIII) with gate sensitivity optimized for low-power drive circuits. Its high dV/dt immunity (2000 V/µs at 125 °C) and critical commutation current (dI/dt)c ≥ 6 A/ms eliminate need for snubber networks when operated within specified voltage and current slew limits.

The device features low on-state voltage (VT ≤ 1.55 V at 8.5 A, 25 °C) and dynamic resistance (Rd ≤ 75 mΩ at 150 °C), ensuring minimal conduction loss in mains-frequency AC loads. Thermal design is enabled by Rth(j-c) = 2.1 °C/W and TO-220AB's metal tab for direct heatsink mounting.

Key Specifications

Pinout & Package

TO-220AB package with insulated metal tab, halogen-free epoxy, lead-free plating, and recommended mounting torque of 0.4–0.6 N·m. Metal tab is electrically connected to MT2 (A2) terminal.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar triac-based AC switching applications.

Compared with BTA06-600BWRG and BTB06-800CW, the T635T-8T uniquely combines 800 V blocking, 2000 V/µs dV/dt, and 35 mA IGT in a non-isolated TO-220AB package - optimizing size, cost, and noise immunity for consumer and industrial AC control where heatsink grounding to MT2 is acceptable.

Availability

T635T-8T is available at Aetrix Electronics and suitable for motor control, lighting dimming, and home appliance load switching requiring stable component supply across production lifecycles.

Supply support for T635T-8T 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 for automotive, industrial, and consumer markets.

The T635T-8T belongs to ST's high-reliability snubberless triac product line, engineered specifically for robust, space-constrained AC power control in cost-sensitive, high-volume applications.

FAQ

Is the T635T-8T suitable for zero-crossing switching applications?

Yes - its 35 mA maximum gate trigger current and low holding current (IH ≤ 40 mA) enable reliable turn-on at or near zero-crossing when driven by optocouplers like MOC3021 or MOC3041. The device maintains conduction through the full half-cycle due to its 6 A RMS rating and thermal stability up to 150 °C junction temperature.

What is the maximum allowable case temperature for continuous 6 A operation?

The datasheet specifies IT(RMS) = 6 A at TC = 135 °C for full sine-wave conduction. Exceeding this case temperature requires derating - e.g., at TC = 100 °C, maximum sustainable IT(RMS) is approximately 4.8 A per Figure 2. Thermal design must ensure Rth(j-c) × (Tj − TC) ≤ power dissipation, with Tj limited to 150 °C.

Can the T635T-8T replace a four-quadrant triac in existing designs?

Only if the original design uses only quadrants I, II, or III - the T635T-8T does not support quadrant IV triggering. Gate drive circuits must be verified to avoid negative gate-to-MT1 voltage during QIV conditions. For full four-quadrant compatibility, ST's T635T-800E (four-quadrant variant) is required.

Does the TO-220AB package require electrical isolation from the heatsink?

Yes - the metal tab is internally connected to MT2 (A2), so direct mounting to a grounded heatsink creates an electrical short unless isolation is implemented. Use insulating washers and shoulder washers with thermal grease, or select the BTB06-800CW (4-pin isolated-tab variant) if system grounding topology prohibits MT2-to-heatsink connection.