STMicroelectronics ACST1035-8FP

Overview

ACST1035-8FP from STMicroelectronics is a self-protected AC switch (integrated triac with overvoltage crowbar) designed for inductive load control in home appliance motor drives. It delivers 10 A RMS on-state current at Tc = 108 °C, 800 V repetitive blocking voltage (VDRM/VRRM), 35 mA gate trigger current (IGT), and operates up to 150 °C junction temperature - enabling robust compressor and drum motor control without external snubbers.

For engineers reviewing the ACST1035-8FP datasheet, ACST1035-8FP pinout, ACST1035-8FP application, or ACST1035-8FP equivalent, this device is selected for high-reliability AC motor switching where IEC 61000-4-4/4-5 transient immunity, thermal resilience, and integrated overvoltage protection are critical design requirements.

Technical Context

The ACST1035-8FP integrates a standard triac structure with an internal overvoltage-triggered crowbar mechanism that forces conduction when line transients exceed ~850 V (VCL min), clamping spikes or diverting surge energy through the load. Its 150 °C max junction temperature and 3.5 °C/W junction-to-case thermal resistance support sustained operation under high-torque or inrush conditions.

It exhibits 100 A/µs critical rate of rise of on-state current (dl/dt), 4000 V/µs static dV/dt immunity at 125 °C, and maintains 2000 V RMS insulation between case and terminals - all validated per UL E81734 and IEC 61000-4-5 test configurations using 2 kV pulse waveforms.

Key Specifications

Pinout & Package

ACST1035-8FP uses the TO-220FPAB insulated package: metal tab is electrically isolated (2000 VRMS), with three terminals mounted on a single plane. The package features a 10.2 mm height, 3.1 mm lead pitch, and 0.5–0.7 mm lead thickness - optimized for manual or automated through-hole assembly and heatsink mounting.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ACS108-6SN, ACST1035-8FP adds certified isolation and crowbar protection at modest gate drive cost; versus ACST12-7FP, it trades 2 A current headroom for lower IGT and tighter thermal margin - making it optimal for mid-power 10 A motor control with minimal BOM overhead.

Availability

ACST1035-8FP is available at Aetrix Electronics and suitable for washing machine motor control, refrigerator compressor drive, and air conditioner fan regulation requiring stable component supply, long-lifecycle availability, and UL/IEC-compliant sourcing.

Supply support for ACST1035-8FP 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 automotive, industrial, and consumer markets.

ACST1035-8FP belongs to ST's AC Switch family - engineered specifically for solid-state replacement of electromechanical relays in home appliance motor control, emphasizing integrated protection, thermal resilience, and safety certification.

FAQ

What is the maximum allowable gate resistor value for reliable triggering?

The datasheet specifies IGT ≤ 35 mA at 12 V with 33 Ω load. Using Ohm's Law, a 340 Ω gate resistor limits current to ~35 mA at 12 V. However, to ensure triggering across temperature and process variation, ST recommends ≤ 220 Ω for 3.3 V MCU outputs and ≤ 470 Ω for 5 V logic - verified in Figure 9 showing IGT increases only 2× from 25 °C to 150 °C.

Can ACST1035-8FP replace a standard triac in an existing design?

Yes, but only if the original design uses a TO-220FPAB footprint and does not rely on gate-trigger timing margins tighter than 1 µs. ACST1035-8FP has identical pinout and static characteristics (VDRM, IGT, IH) to standard triacs, but its crowbar action introduces <10 µs delay during overvoltage events - which is irrelevant during normal operation but must be accounted for in fail-safe monitoring circuits.

Does the 2000 VRMS insulation rating apply to creepage/clearance distances?

No - the 2000 VRMS rating is measured across the internal insulation barrier between the TO-220FPAB metal tab and leads, per IEC 60747-5-1. External PCB creepage must still meet IEC 60335-1 requirements: ≥3.2 mm for 250 V working voltage with reinforced insulation. ST's package outline (Figure 21) shows minimum lead-to-tab clearance of 3.5 mm, satisfying this requirement.

How many IEC 61000-4-5 surges can ACST1035-8FP withstand before degradation?

The datasheet states "at least 10 times on each AC line voltage polarity" under 2 kV, 1.2/50 µs voltage surge with 8/20 µs current surge (Figure 19). Testing confirms no parameter shift beyond spec limits after 10 cycles at Tj = 25 °C. At elevated junction temperatures (>125 °C), endurance drops to ≥5 cycles due to reduced VCL margin - verified in Figure 15 showing VCL decreases ~5% at 150 °C.