STMicroelectronics ACST4-7SB-TR

Overview

ACST4-7SB-TR from STMicroelectronics is a 4 A RMS, 700 V blocking voltage AC power switch in DPAK package, featuring integrated Triac structure with avalanche clamping (V_CL = 1100 V), gate trigger current < 10 mA, and direct microcontroller interface capability. It drives inductive/resistive loads such as dishwasher spray pumps and air-conditioner fans without external snubber or overvoltage protection.

For engineers reviewing the ACST4-7SB-TR datasheet, ACST4-7SB-TR pinout, ACST4-7SB-TR application, or ACST4-7SB-TR equivalent, key selection criteria include dV/dt immunity (>500 V/µs at T_j = 110 °C), I_TSM = 30 A surge rating, thermal resistance R_th(j-c) = 2.6 °C/W, and IEC 61000-4-5 transient ruggedness up to 2 kV peak pulse voltage.

Technical Context

The ACST4-7SB-TR implements ASD™ technology - a planar Triac-based AC switch with monolithically integrated high-voltage clamping. Its gate-triggered turn-on operates in all four quadrants (QI–QIII), enabling robust commutation under high dV/dt stress and inductive load switching.

It sustains non-repetitive line transients per IEC 61000-4-5 (2 kV, 220 Ω source impedance) without external protection, thanks to its 1100 V clamping voltage and 50 A/µs critical dI/dt rating at T_j = 125 °C. The device uses direct logic-level gate drive with <10 mA I_GT, eliminating need for discrete driver stages.

Key Specifications

Pinout & Package

DPAK (TO-252) package with exposed thermal pad (Tab connected to COM pin), optimized for surface-mount assembly and thermal conduction via copper pour.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ACST4-7CB-TR and ACS108-7SN, the ACST4-7SB-TR uniquely combines low gate drive demand (<10 mA), full IEC 61000-4-5 ruggedness, and 4 A load capability in DPAK - making it optimal for mid-power appliance control where reliability, size, and MCU compatibility are jointly critical.

Availability

ACST4-7SB-TR is available at Aetrix Electronics and suitable for dishwasher control modules, HVAC fan drivers, smart plug designs, and industrial heater controllers requiring stable component supply across multi-year production cycles.

Supply support for ACST4-7SB-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, designing and manufacturing analog, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The ACST4 series belongs to ST's ASD™ AC power switch product line, engineered specifically for solid-state replacement of electromechanical relays in home appliances and industrial controls - emphasizing transient robustness, gate-drive simplicity, and snubberless inductive load switching.

FAQ

What is the maximum allowable junction temperature for continuous operation?

The ACST4-7SB-TR has a specified operating junction temperature range of –30 °C to +125 °C. For continuous RMS current of 4 A, case temperature must be maintained at ≤110 °C per datasheet derating curves (Fig. 2-1). Thermal design must ensure R_th(j-c) = 2.6 °C/W is achieved via adequate copper area under the Tab (COM-connected thermal pad).

Does this device require a heat sink in typical appliance applications?

A dedicated heat sink is not required for most 4 A RMS applications if the PCB provides ≥0.5 cm² of 35 µm-thick copper under the DPAK Tab. Thermal resistance to ambient drops to ~70 °C/W under those conditions (Fig. 11), allowing safe operation at T_c = 110 °C without additional heatsinking in enclosed but ventilated enclosures.

Can ACST4-7SB-TR replace a mechanical relay in a 230 VAC, 3 A fan circuit?

Yes - it is qualified for direct replacement: it handles 3 A RMS continuously at T_c ≤ 110 °C, withstands 2 kV IEC 61000-4-5 surges, and switches inductive loads without snubber. Its <10 mA gate drive simplifies MCU interface versus relay coil drivers, and its solid-state nature eliminates contact arcing and wear.

Is zero-crossing switching supported natively by this device?

No - the ACST4-7SB-TR is a random-turn-on AC switch, not a zero-crossing type. However, it can be synchronized to zero-crossing using an external zero-cross detection circuit feeding the MCU, which then triggers the gate precisely at voltage zero. Its high dV/dt immunity (>500 V/µs) prevents false turn-on during voltage transitions.