STMicroelectronics ACST10-7ST

Overview

ACST10-7ST from STMicroelectronics is an overvoltage-protected AC switch (Triac) with integrated crowbar clamping, rated for 10 A RMS and 700 V blocking voltage, featuring low gate trigger current (IGT ≤ 10 mA) and high static dV/dt immunity (>2000 V/µs), used for direct MCU-controlled switching of universal motors in washing machine drums.

For engineers reviewing the ACST10-7ST datasheet, ACST10-7ST pinout, ACST10-7ST application, or ACST10-7ST equivalent, this device delivers self-protected AC mains switching without external snubbers, meets IEC 61000-4-5 surge immunity, and supports compact, reliable control of inductive loads up to 10 A in home appliance power stages.

Technical Context

The ACST10-7ST integrates a planar Triac structure with monolithically embedded overvoltage crowbar protection, enabling automatic foldback to conduction during line transients ≥850 V (VCL), recovering full blocking capability after zero-crossing. Its gate-triggering threshold remains stable across –40 °C to +125 °C junction temperature.

It operates in all four quadrants with guaranteed IGT ≤10 mA at 25 °C and static dV/dt ≥2000 V/µs at 125 °C, eliminating need for external transient suppressors while maintaining <1.5 V on-state drop at 14.1 A and 25 °C (VTM).

Key Specifications

Pinout & Package

ACST10-7ST is housed in TO-220AB package (non-insulated, metal tab connected to MT2), with three terminals: COM (MT1), OUT (MT2), and G (Gate). The metal tab serves as heat sink interface and electrical connection to MT2.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ACST1035-7T, ACST10-7ST offers lower gate drive burden ideal for direct MCU control, while TIC226M lacks integrated overvoltage protection-requiring external components to meet same surge standards, increasing design risk and footprint.

Availability

ACST10-7ST is available at Aetrix Electronics and suitable for washing machine motor control, refrigerator compressor drive, and industrial AC load sequencing requiring stable component supply, long-term lifecycle support, and traceable sourcing for consumer appliance OEMs.

Supply support for ACST10-7ST 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, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The ACST™ family was developed specifically for robust, snubberless AC mains switching in white goods and industrial controls, combining Triac functionality with monolithic overvoltage protection to simplify safety-certified designs.

FAQ

What is the maximum allowable gate resistor value when driving ACST10-7ST directly from a 3.3 V MCU GPIO?

With IGT ≤10 mA max and VGT ≤1.0 V, a 3.3 V MCU GPIO can drive the gate through a 220 Ω resistor (allowing ≥10.5 mA worst-case current at 25 °C). At 125 °C, IGT may rise to ~15 mA; 180 Ω ensures margin. Higher values risk unreliable triggering under temperature or voltage variation.

Does ACST10-7ST require a heatsink for 10 A continuous operation?

Yes - at 10 A RMS and Tc = 105 °C, the TO-220AB package requires a heatsink achieving ≤1.7 °C/W thermal resistance. Without forced airflow, a 15 cm² aluminum heatsink (1 mm thick) is typical. Junction temperature must stay ≤125 °C; derate linearly above 105 °C case temperature.

Can ACST10-7ST replace a standard Triac like BT139-600 in existing designs?

Yes, as a pin-compatible upgrade: same TO-220AB footprint and terminal assignment (MT1/MT2/Gate). However, its crowbar action changes failure mode - it latches during overvoltage instead of failing open. System firmware must handle brief conduction during surges and ensure safe load disconnection post-event.

How does the VCL parameter affect circuit protection design?

VCL = 850 V (min) defines the clamping voltage at which the device enters crowbar mode. It ensures inductive spikes and IEC 61000-4-5 surges are limited below 850 V, protecting downstream components. Unlike TVS diodes, ACST10-7ST dissipates surge energy through the load, so load power rating must sustain ≥2 kV × 10 A × 10 ms pulses.