STMicroelectronics ACST435-8BTR

Overview

ACST435-8BTR from STMicroelectronics is a 4 A, 800 V insulated AC switch with integrated overvoltage clamping, designed as a self-protected triac replacement for mains-connected inductive load control. It features 35 mA maximum gate trigger current (IGT), 1000 V/μs static dV/dt immunity at 125 °C, and TO-220FPAB package with 2000 VRMS insulation - enabling direct MCU-driven compressor and drum motor switching in washing machines and refrigerators without external snubbers or MOVs.

For engineers reviewing the ACST435-8BTR datasheet, ACST435-8BTR pinout, ACST435-8BTR application, or ACST435-8BTR equivalent, this device is selected for IEC 61000-4-4/4-5-compliant AC static switching where high noise immunity, zero external protection, and thermal robustness up to 125 °C junction temperature are required.

Technical Context

The ACST435-8BTR implements a planar triac structure with monolithically integrated voltage-clamping crowbar circuitry, enabling automatic turn-on during line transients ≥850 V (VCL min) to safely dissipate surge energy through the load. Its gate is optimized for high-noise immunity: IGT ≤35 mA at 25 °C and dV/dt ≥1000 V/μs at Tj = 125 °C with gate open.

Thermal design leverages TO-220FPAB's 4.6 °C/W junction-to-case resistance and UL-certified 2000 VRMS insulation, allowing operation at 4 A RMS with case temperature ≤102 °C under full conduction - eliminating need for heatsink derating in sealed appliance enclosures.

Key Specifications

Pinout & Package

ACST435-8BTR uses the TO-220FPAB package: insulated plastic body with metal tab, UL E81734 certified, 2000 VRMS isolation, and recommended mounting torque of 0.4–0.6 N·m. Tab is electrically connected to COM terminal.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar AC switch applications.

Compared with ACST410-8BTR, ACST435-8BTR trades lower gate sensitivity for superior noise immunity - critical in shared-appliance PCBs with compressors and motors. Versus BTB16-800BRG, it reduces total solution size and qualification effort by integrating protection previously requiring 3+ discrete components.

Availability

ACST435-8BTR is available at Aetrix Electronics and suitable for washing machine motor control, refrigerator compressor drive, and industrial AC solenoid valve actuation requiring stable component supply across multi-year production lifecycles.

Supply support for ACST435-8BTR 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, and microcontroller solutions for industrial, automotive, and consumer markets.

The ACST4 series belongs to ST's ACS/ACST power switch family - engineered specifically for IEC 61000-4-4/4-5-compliant AC static switching in home appliances, where integrated overvoltage protection and high dV/dt immunity replace legacy triac + protection designs.

FAQ

What is the maximum allowable case temperature for continuous 4 A RMS operation?

The ACST435-8BTR supports 4 A RMS continuous conduction at Tc ≤102 °C (full sine wave, TO-220FPAB package), as specified in Table 1. Exceeding this temperature requires derating per Figure 2, where IT(RMS) drops to ~3.2 A at Tc = 110 °C. Thermal interface material and heatsink design must maintain tab-to-heatsink ΔT within this limit.

Can ACST435-8BTR replace a mechanical relay in a 230 VAC, 3 A resistive load application?

Yes - its 4 A RMS rating, 800 V blocking voltage, and zero-contact wear make it suitable for resistive load switching. Unlike relays, it offers silent operation, infinite cycle life, and immunity to vibration-induced bounce. Gate drive requires only a 220 Ω resistor from a 3.3 V/5 V MCU GPIO, per Figure 17.

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

No - the TO-220FPAB package features reinforced insulation (2000 VRMS, UL E81734) so the metal tab (COM terminal) may be directly bolted to an earthed heatsink without additional insulating hardware. This simplifies thermal design and improves reliability versus insulated-mount alternatives.

How does the integrated overvoltage clamping function during a 2 kV IEC 61000-4-5 surge?

During a 2 kV surge, the ACST435-8BTR's internal crowbar triggers when voltage exceeds 850 V (VCL min), forcing the device into low-impedance conduction for <10 ms. Energy is safely dissipated through the load, and the device recovers blocking capability after the next zero-crossing - verified for ≥10 polarity-switched surges per Figure 17 test setup.