STMicroelectronics ACST1235-7T

Overview

ACST1235-7T from STMicroelectronics is a 12 A, 700 V overvoltage-protected AC switch (Triac) with integrated crowbar clamping and ultra-high static dV/dt immunity of ≥2000 V/µs at 125 °C. It drives medium-power inductive AC loads-such as refrigerator compressors and washing machine drum motors-without external snubbers or transient protection components, and operates reliably under IEC 61000-4-4/4-5 surge conditions.

For engineers reviewing the ACST1235-7T datasheet, ACST1235-7T pinout, ACST1235-7T application, or ACST1235-7T equivalent, key selection criteria include verified dV/dt immunity, gate trigger current (IGT = 35 mA), clamping voltage (VCL ≥ 850 V), thermal resistance (Rth(j-c) = 1.5 °C/W), and TO-220AB package compatibility for industrial mains switching.

Technical Context

The ACST1235-7T implements A.S.D.® (Application Specific Discrete) technology with a monolithic Triac core plus integrated high-voltage crowbar clamping circuit. Its structure enables self-triggering into conduction during line transients exceeding VCL, safely diverting surge energy through the load without latch-up or failure.

This device operates in all four quadrants with guaranteed IGT ≤ 35 mA at 25 °C and maintains ≥2000 V/µs static dV/dt immunity up to 125 °C-enabling robust operation in noisy industrial AC mains environments where fast transients and inductive turn-off spikes are common.

Key Specifications

Pinout & Package

ACST1235-7T uses the TO-220AB package (JEDEC TO-220 variant) with isolated tab, rated for 0.4–0.6 N·m mounting torque and UL94 V0 epoxy molding. The case serves as the COM terminal, enabling direct heatsink mounting with electrical isolation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ACST1210-7T, ACST1235-7T trades lower gate sensitivity for superior noise immunity-critical for compressor applications. Versus BTB12-700CW, it integrates protection that would otherwise require three additional components and layout space.

Availability

ACST1235-7T is available at Aetrix Electronics and suitable for refrigerator compressor control, washing machine motor drive, and industrial HVAC blower activation requiring stable component supply across multi-year production lifecycles.

Supply support for ACST1235-7T 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 industrial, automotive, and consumer markets.

The ACST™ family is engineered specifically for robust AC mains switching in home appliances and industrial controls-emphasizing integrated surge resilience, snubberless inductive load handling, and direct microcontroller interoperability.

FAQ

What is the maximum continuous case temperature for reliable operation?

The ACST1235-7T supports continuous operation at Tc = 104 °C with IT(RMS) = 12 A, as validated in Figure 3 of the datasheet. Derating begins above this point; at Tc = 125 °C, maximum RMS current drops to ~8.5 A. Thermal design must ensure the tab remains below 104 °C under worst-case ambient and airflow conditions.

Does ACST1235-7T require a heat sink in 12 A applications?

Yes-a heatsink is mandatory for sustained 12 A RMS operation. With Rth(j-c) = 1.5 °C/W and typical power dissipation of ~1.8 W at 12 A, even a modest 20 °C rise above ambient requires thermal resistance from case to ambient ≤ 11 °C/W. A small extruded aluminum heatsink (e.g., 50 × 50 × 20 mm) meets this requirement in still air.

Can ACST1235-7T replace a mechanical relay in compressor applications?

Yes-its 120 A non-repetitive surge rating (IEC 61000-4-5 compliant clamping), 12 A RMS capacity, and planar junction reliability make it a proven solid-state relay replacement. Unlike relays, it eliminates contact bounce, wear, and EMI from arcing-while handling compressor inrush and turn-off transients natively.

Is the metal tab electrically isolated in TO-220AB packaging?

No-the TO-220AB package has an electrically connected tab serving as the COM terminal. Electrical isolation requires insulating hardware (e.g., silicone washer + shoulder washer) between tab and heatsink. For fully isolated mounting, ST offers D2PAK variants (e.g., ACST1235-7G), where the tab is not internally connected to any pin.