STMicroelectronics T1235T-8R

Overview

T1235T-8R from STMicroelectronics is a snubberless 12 A, 800 V RMS triac in I²PAK package, designed for AC line phase and on/off control without external snubber circuits. It operates up to 150 °C junction temperature, features 35 mA gate trigger current (IGT), 2000 V/µs dV/dt immunity at 125 °C, and supports motor control, lighting dimming, and appliance load switching.

For engineers reviewing the T1235T-8R datasheet, T1235T-8R pinout, T1235T-8R application, or T1235T-8R equivalent, key selection criteria include snubberless commutation capability, high-temperature operation up to 150 °C, three-quadrant triggering, dynamic dV/dt immunity, and I²PAK thermal performance for compact industrial and consumer AC control designs.

Technical Context

This triac uses a three-quadrant triggering architecture (Quadrants I, II, III) enabling gate control with either polarity of A2 relative to A1. Its snubberless design relies on guaranteed minimum dV/dt (2000 V/µs at 125 °C) and critical rate of rise of on-state current (100 A/µs) to prevent false turn-on during voltage transients.

Thermal design is enabled by Rth(j-c) = 1.5 °C/W and full-rated 150 °C junction operation, allowing sustained 12 A RMS conduction at TC = 128 °C. The device sustains 95 A non-repetitive surge (tp = 16.7 ms) and 66 A²s I²t fusing value, supporting inrush current handling in motor and transformer loads.

Key Specifications

Pinout & Package

Housed in an I²PAK (TO-262 variant) package with exposed drain tab for thermal and electrical connection to heatsink. Dimensions: 9.15 mm × 10.2 mm × 4.5 mm (L × W × H), weight 1.7 g, ECOPACK®2 compliant, lead-free, halogen-free molding compound.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BTA12-800BWRG and BTB12-800CW, T1235T-8R offers superior snubberless reliability via higher dV/dt and three-quadrant flexibility, while its I²PAK package delivers better thermal resistance (1.5 °C/W vs. ~2.5 °C/W) in space-constrained designs.

Availability

T1235T-8R is available at Aetrix Electronics and suitable for motor control, lighting dimming, home appliance load switching, and inrush current limiting applications requiring stable component supply across industrial and consumer production programs.

Supply support for T1235T-8R 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, power, MCU, and sensor solutions for automotive, industrial, and consumer markets.

T1235T-8R belongs to ST's Snubberless™ Triac product line, engineered specifically for compact, high-temperature AC load control where reliability, reduced BOM count, and elimination of snubber components are critical design goals.

FAQ

Is T1235T-8R truly snubberless in all applications?

Yes - the device is characterized for snubberless operation under defined conditions: dV/dt ≥2000 V/µs at 125 °C, (dI/dt)c ≥19.5 A/ms, and gate drive meeting IGT ≤35 mA. Real-world implementation still requires proper PCB layout, gate drive timing, and load type verification per ST Application Note AN437.

What is the maximum allowable case temperature for continuous 12 A operation?

The datasheet specifies IT(RMS) = 12 A at TC = 128 °C for full sine wave conduction. Exceeding this case temperature requires linear derating per Figure 2; at TC = 100 °C, maximum RMS current rises to ~14.5 A, constrained by Rth(j-c) = 1.5 °C/W and Tj ≤150 °C.

Can T1235T-8R be used with zero-crossing SSR drivers?

No - zero-crossing drivers deliver gate pulses only near voltage zero, which is incompatible with triac latching requirements. T1235T-8R requires a minimum gate pulse width (≥10 µs) and amplitude (≥1.5×IGT) during conduction window, best driven by phase-controlled optocouplers like MOC3021 or microcontroller-timed pulses.

Does the I²PAK package require electrical isolation from the heatsink?

Yes - the A2 terminal is internally connected to the exposed metal tab. When mounted on a heatsink, electrical isolation (e.g., mica washer + thermal paste or isolating pad) is mandatory unless the heatsink is fully floating or referenced to A2 potential in the system design.