STMicroelectronics T405-800B-TR

Overview

T405-800B-TR from STMicroelectronics is a 4 A, 800 V three-quadrant logic-level triac in DPAK package, designed for zero-crossing and phase-control AC switching in inductive loads. It features 5 mA max gate trigger current (IGT), 1.56 V max on-state voltage (VTM), and 20 V/µs minimum critical dV/dt at 125 °C, enabling reliable commutation in universal motor drives and kitchen appliance control circuits.

For engineers reviewing the T405-800B-TR datasheet, T405-800B-TR pinout, T405-800B-TR application, or T405-800B-TR equivalent, key selection criteria include RMS current rating (4 A), blocking voltage (800 V), gate sensitivity (5 mA IGT), thermal resistance (70 °C/W junction-to-ambient), and DPAK package compatibility with FR4 PCB layouts.

Technical Context

The T405-800B-TR uses ST's Snubberless logic-level triac architecture optimized for high commutation performance without external snubbers. Its three-quadrant operation eliminates quadrant IV triggering, reducing false turn-on risk in noisy AC environments.

It supports full-cycle sinusoidal conduction with 30 A non-repetitive surge current (50 Hz, 20 ms), 50 A/µs critical dI/dt (at 125 °C), and 2.6 °C/W junction-to-case thermal resistance - enabling direct heatsink mounting in compact motor control modules.

Key Specifications

Pinout & Package

DPAK (TO-252) surface-mount package with isolated tab; thermally enhanced for PCB copper area mounting. Pin 1 = MT2, Pin 2 = MT1, Pin 3 = Gate - standard triac terminal assignment per IEC 60747-6.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BT134-800D and T410-800B-TR, the T405-800B-TR offers lowest gate drive demand (5 mA), making it optimal for low-power MCU interfaces, while maintaining identical 800 V blocking and DPAK footprint - ideal for cost-sensitive, space-constrained appliance control boards.

Availability

T405-800B-TR is available at Aetrix Electronics and suitable for universal motor control, solenoid actuation, kitchen appliance power switching, and small home appliance motor drives requiring stable component supply across production lifecycles.

Supply support for T405-800B-TR 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 T4 series triacs are part of ST's power discrete portfolio, engineered specifically for snubberless, logic-level AC switching in cost-sensitive, high-volume appliance and motor control applications.

FAQ

What is the maximum junction temperature for continuous operation?

The T405-800B-TR has an operating junction temperature range of –40 °C to +125 °C. For continuous 4 A RMS operation in DPAK package, case temperature must be held ≤110 °C per Table 3, requiring ≥0.5 cm² copper area on FR4 PCB or external heatsinking to maintain thermal safety margin.

Can this triac replace a BT136 in an existing design?

No - BT136 is a 4 A, 600 V triac with different gate sensitivity (15 mA IGT) and thermal characteristics. T405-800B-TR has higher blocking voltage (800 V) and lower IGT (5 mA), but requires verification of PCB layout, gate drive circuit, and thermal management due to differing Rth(j-a) (70 vs. ~65 °C/W) and dV/dt rating.

Is a snubber circuit required for inductive loads?

No - the T405-800B-TR is explicitly designed as a Snubberless triac. Its 20 V/µs dV/dt rating at 125 °C and optimized internal structure eliminate the need for external RC snubbers in typical 230 VAC inductive loads like universal motors and solenoids, per ST's application guidance in AN437.

What is the recommended gate resistor value for MCU GPIO drive?

For 3.3 V GPIO driving the gate with 5 mA IGT max, a 470 Ω series resistor limits peak current to ~7 mA while providing noise filtering. ST recommends keeping gate trace short and routing away from high-dv/dt nodes; no pull-down resistor is needed due to inherent gate leakage control in logic-level triacs.