STMicroelectronics T435-400T

Overview

T435-400T from STMicroelectronics is a 4 A, 400 V snubberless triac designed for AC inductive load switching in universal motor control, electrovalves, and small home appliances. It features three-quadrant operation, 35 mA maximum gate trigger current (IGT), 400 V repetitive peak off-state voltage (VDRM/VRRM), and 50 A/µs critical dI/dt rating at 125 °C.

For engineers reviewing the T435-400T datasheet, T435-400T pinout, T435-400T application, or T435-400T equivalent, key selection criteria include snubberless commutation performance, thermal resistance (Rth(j-c) = 2.6 °C/W), TO-220AB package mounting torque (0.4–0.6 N·m), and compatibility with logic-level gate drive in 50/60 Hz AC mains environments.

Technical Context

The T435-400T operates as a three-quadrant triac with gate-triggered conduction in Quadrants I, II, and III-enabling robust turn-on without false triggering during high dv/dt transients. Its Snubberless technology eliminates need for external RC snubbers in inductive loads like universal motors and solenoids.

It delivers 400 V VDRM/VRRM with 35 mA max IGT, 35 mA max holding current (IH), and 50 mA max latching current (IL) at 25 °C. Critical dV/dt immunity reaches 400 V/µs at 125 °C, supporting reliable operation in noisy AC line environments without gate protection circuitry.

Key Specifications

Pinout & Package

Package: TO-220AB (non-insulated, 3-lead, through-hole). Tab is connected to MT2 terminal. Mounting torque: 0.4–0.6 N·m.

Key Features

Applications

Equivalent & Alternatives

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

Compared with T435-600T, the T435-400T trades 200 V off-state margin for tighter voltage matching to 230 VAC systems, while outperforming Q4004L4 in dV/dt immunity and surge robustness-making it preferred for compact, noise-prone appliance designs.

Availability

T435-400T is available at Aetrix Electronics and suitable for vacuum cleaner motor control, dishwasher solenoid actuation, and kitchen aid mixer speed regulation requiring stable component supply across high-volume consumer electronics production.

Supply support for T435-400T 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, MCU, power, and discrete devices for automotive, industrial, and consumer markets.

The T4 series belongs to ST's high-reliability AC power switching product line, engineered specifically for snubberless operation in universal motor and solenoid-driven home appliances-prioritizing commutation robustness, thermal efficiency, and gate drive simplicity.

FAQ

Is the T435-400T compatible with zero-crossing trigger circuits?

No-the T435-400T is not optimized for zero-crossing operation. It is a snubberless, three-quadrant triac intended for phase-angle control where precise timing of gate pulses relative to the AC waveform enables variable power delivery. Zero-crossing operation requires dedicated ZC-triacs with internal timing circuitry not present in this device.

What is the maximum allowable gate resistor value when driving T435-400T from a 5 V MCU GPIO?

With a 5 V supply and 35 mA max IGT, the absolute maximum series gate resistor is 143 Ω (5 V ÷ 35 mA). However, to ensure reliable turn-on across temperature and device variation, ST recommends ≤100 Ω. Lower values (e.g., 47 Ω) improve noise immunity and reduce gate charge time, especially at high junction temperatures.

Does the TO-220AB package of T435-400T require electrical isolation from the heatsink?

Yes-MT2 is internally connected to the metal tab. If the heatsink is grounded or at a different potential than MT2, an insulating washer and shoulder washer must be used. ST specifies 0.4–0.6 N·m mounting torque; exceeding this risks cracking the package or compromising thermal interface integrity.

Can T435-400T replace a BT136-600E in an existing design?

Only with validation. While both are 4 A, 600 V triacs, the T435-400T has lower VDRM (400 V vs. 600 V), higher IGT (35 mA vs. 5 mA), and three-quadrant operation (BT136 is four-quadrant). Direct substitution may cause false triggering or insufficient voltage margin-re-layout and gate drive adjustment are required.