STMicroelectronics BTA40-400B

Overview

BTA40-400B from STMicroelectronics is a 40 A, 400 V RMS insulated TRIAC in RD91 package, rated for 2500 V_rms isolation between main terminals and heatsink, designed for high-power AC switching in static relays, heating regulation, and motor starting circuits. It supports phase control up to 9 kW with proper heatsinking and meets UL 1557 (file ref: 81734) and RoHS 2002/95/EC.

For engineers reviewing the BTA40-400B datasheet, BTA40-400B pinout, BTA40-400B application, or BTA40-400B equivalent, key selection criteria include its 40 A RMS current rating, 400 V blocking voltage, 50 mA gate trigger current, insulated tab design, and thermal resistance of 0.9 °C/W (junction-to-case).

Technical Context

The BTA40-400B is a four-quadrant sensitive-gate TRIAC optimized for robust AC line commutation in industrial and appliance control. Its gate trigger current (IGT ≤ 50 mA) ensures reliable turn-on across all quadrants, while dV/dt immunity ≥ 500 V/µs at 125 °C prevents false triggering under noisy line conditions.

Thermal performance is defined by R_th(j-c) = 0.9 °C/W and maximum junction temperature of +125 °C, enabling continuous 40 A conduction at T_c = 80 °C. The insulated RD91 package provides galvanic isolation between MT1/MT2 and heatsink, critical for safety-compliant designs.

Key Specifications

Pinout & Package

The BTA40-400B uses the RD91 power package with insulated metal tab. Mounting torque must not exceed 1.2 N·m. The device has three terminals: MT1 (Main Terminal 1), MT2 (Main Terminal 2), and Gate (G). MT1 and MT2 connect to AC line/load; Gate controls conduction. The insulated tab serves as MT2 and provides 2500 V_rms isolation from heatsink.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BTA40-400B, the BTA40-600B extends voltage capability without trade-offs in current or isolation, while the BTA41-600BRG trades mechanical robustness and heatsink contact area for PCB integration-neither is pin-compatible due to differing packages (RD91 vs. TOP3).

Availability

BTA40-400B is available at Aetrix Electronics and suitable for static relay control, heating regulation, and motor starting applications requiring stable component supply, long-term industrial lifecycle support, and certified insulation compliance.

Supply support for BTA40-400B 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, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The BTA40 series belongs to ST's high-power AC switching TRIAC product line, engineered specifically for safety-certified, high-reliability AC load control in appliances, industrial automation, and energy management systems.

FAQ

What is the maximum continuous RMS current for BTA40-400B at 80 °C case temperature?

The BTA40-400B supports 40 A RMS continuous conduction at T_c = 80 °C with 180° conduction angle, as specified in Table 1 of DS2111 Rev 13. Derating is required above this temperature: at T_c = 100 °C, maximum IT(RMS) drops to approximately 28 A per Figure 2.

Does BTA40-400B require a heatsink, and what thermal resistance is needed?

Yes - a heatsink is mandatory for continuous operation above ~5 A. With R_th(j-c) = 0.9 °C/W and max T_j = 125 °C, a total system R_th(j-a) ≤ 3.1 °C/W is required at 40 A. This typically demands a forced-air or large passive heatsink; ST recommends using AN533 for sizing.

Can BTA40-400B be driven directly by a microcontroller GPIO?

No - the gate requires ≥50 mA peak current for reliable triggering. A microcontroller GPIO (typically 20 mA max) must interface via a driver stage: either a discrete transistor (e.g., BC817) or an optocoupler (e.g., MOC3021) with zero-crossing or random-phase output, per ST's recommended gate drive circuits in DS2111 Section 5.

Is BTA40-400B compliant with RoHS and REACH regulations?

Yes - BTA40-400B uses RoHS-compliant (2002/95/EC) and REACH-conformant materials. Its epoxy package meets UL94 V0 flammability standard, and it carries ECOPACK®2 environmental grade certification per ST's public compliance documentation.