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Home > Products > Discrete Semiconductor Products > Thyristors > TRIACs

STMicroelectronics ACST435-8B

Name: ACST435-8B
Brand: STMicroelectronics
SKU: ACST435-8B
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: ACST435-8B

Manufacturer:: STMicroelectronics

Category:: TRIACs

Package:: TO-252-3, DPAK (2 Leads + Tab), SC-63

Datasheet:: ACST435-8B.pdf

Description:: TRIAC 800V 4A DPAK

Quantity:: RFQ Add To RFQ list

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Product details

Overview

ACST435-8B from STMicroelectronics is a 4 A, 800 V insulated AC switch with integrated overvoltage clamping (V_CL ≥ 850 V), high dV/dt immunity (>1000 V/μs at T_j = 125 °C), and 35 mA gate trigger current (I_GT). It functions as a self-protected triac replacement in mains-connected load switching circuits, enabling direct MCU-driven control of universal drum motors in washing machines without external snubbers or MOVs.

For engineers reviewing the ACST435-8B datasheet, ACST435-8B pinout, ACST435-8B application, or ACST435-8B equivalent, this device is selected for IEC 61000-4-4/4-5-compliant AC load switching where high noise immunity, thermal robustness up to 125 °C junction temperature, and elimination of discrete overvoltage protection are critical design requirements.

Technical Context

The ACST435-8B implements a planar triac structure with monolithically integrated voltage-clamping crowbar circuitry that activates at ≥850 V to safely divert line transients-such as inductive turn-off spikes or IEC 61000-4-5 2 kV surges-by latching into conduction for <10 ms before recovering blocking capability at zero-crossing.

Its 35 mA I_GT threshold enables reliable triggering from standard MCU GPIOs via a single series resistor (68 Ω recommended), while its static dV/dt >1000 V/μs and critical dI/dt ≥5 A/ms (unsnubbed) support direct drive of inductive loads like compressor windings and universal motors without auxiliary commutation components.

Key Specifications

Parameter	Value and Actual Design Meaning
I_T(RMS)	4 A - Sustains continuous sinusoidal load current up to 4 A at T_c = 102 °C (DPAK) without derating
V_DRM/V_RRM	800 V - Blocks 800 V peak AC line voltage, suitable for 230 V_RMS mains with safety margin
I_GT	35 mA max - Gate trigger current level optimized for noise-immune operation in industrial EMI environments
dV/dt (static)	>1000 V/μs - Immune to fast transients per IEC 61000-4-4, eliminating need for gate RC snubbers
V_CL	≥850 V - Clamps overvoltage events per IEC 61000-4-5, absorbing energy without external protection
R_th(j-c)	2.6 °C/W - Low thermal resistance enables compact heatsink design for 4 A conduction in DPAK package
V_TM	1.7 V max - Low on-state voltage drop minimizes power loss (≤6.8 W at 4 A) and thermal stress

Pinout & Package

DPAK (TO-252) insulated surface-mount package with isolated tab rated for 2000 V_RMS insulation (UL E81734 certified); thermally optimized for PCB copper area ≥0.5 cm² under tab.

Pin/Terminal	Circuit Role	Design Meaning
COM	Common terminal (anode/cathode reference)	Internal connection point for bidirectional conduction path; referenced to both OUT and gate for symmetrical triggering
OUT	Main output terminal (load connection)	Carries full 4 A RMS load current; electrically symmetric with COM for AC operation
G	Gate control input	Accepts 35 mA DC pulse to initiate conduction in any quadrant; referenced to COM, not ground

Key Features

Feature	Design Value
Integrated overvoltage clamping	V_CL ≥ 850 V enables compliance with IEC 61000-4-5 without MOVs or TVS diodes
High dV/dt immunity	>1000 V/μs at 125 °C eliminates gate snubber networks in noisy appliance environments
Direct MCU interface	35 mA I_GT allows drive from 3.3 V/5 V microcontrollers using only a 68 Ω series resistor
Planar triac technology	Ensures stable off-state leakage (<0.5 mA at 125 °C) and repeatable surge endurance (≥10 IEC 61000-4-5 cycles)
Insulated DPAK package	2000 V_RMS isolation meets reinforced insulation requirements for Class I appliances

Applications

Washing Machine Drum Motor Control

Refrigerator Compressor Start/Run

Use Scenario: Bidirectional speed and direction control of universal AC motors in front-load washers.

IC Role / Device Role / Timing Role: AC mains switch replacing mechanical relays and discrete triacs with snubbers.

Use Value: Eliminates 3–4 passive components (MOV, RC snubber, gate resistor network) while maintaining IEC 61000-4-4 immunity.

Use Scenario: Inrush-current-tolerant start/run switching for hermetic compressors in refrigeration systems.

IC Role / Device Role / Timing Role: High-dI/dt capable AC switch handling 30 A surge (16.7 ms) without failure.

Use Value: Withstands compressor lock-rotor surges and recovers blocking after transient without latch-up or degradation.

Industrial HVAC Fan Control

Smart Plug Load Switching

Use Scenario: Phase-angle dimming and on/off control of shaded-pole and PSC fans in commercial HVAC units.

IC Role / Device Role / Timing Role: Zero-crossing synchronized switching element with built-in transient suppression.

Use Value: Reduces EMI emissions during switching and prevents false triggering from motor back-EMF spikes.

Use Scenario: Mains-isolated load switching in UL-certified smart power strips and IoT-enabled outlets.

IC Role / Device Role / Timing Role: Reinforced-insulation AC switch enabling creepage/clearance compliance in compact form factors.

Use Value: 2000 V_RMS isolation and 800 V blocking voltage meet UL 62368-1 reinforced insulation requirements.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
ACST410-8B	I_GT ≤ 10 mA vs. 35 mA; lower gate drive requirement but reduced noise margin	Better suited for low-noise MCU outputs; less tolerant of PCB coupling or shared ground noise	Select when gate drive strength is limited and system EMI is controlled; avoid in high-noise industrial enclosures
ACS108-8SN	Lower I_T(RMS) (1.2 A), no integrated clamping (requires external MOV), TO-92 package	Limited to low-power resistive loads; unsuitable for compressor or motor inrush	Only viable for indicator lamps or small solenoids; cannot replace ACST435-8B in 4 A inductive applications

Compared with ACST410-8B, ACST435-8B trades lower gate sensitivity for superior noise immunity-critical in washer motor control where brush noise and relay bounce coexist. Unlike ACS108-8SN, it delivers full 4 A capability with integrated protection, eliminating BOM cost and board space for external clamping components.

Availability

ACST435-8B is available at Aetrix Electronics and suitable for washing machine motor control, refrigerator compressor switching, and smart plug load management requiring stable component supply across multi-year production cycles.

Supply support for ACST435-8B 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 robust, snubberless AC load control in home appliances and industrial equipment operating under harsh EMI and surge conditions.

FAQ

What is the maximum continuous load current supported by ACST435-8B?

The ACST435-8B supports 4 A RMS continuous current when mounted on a PCB with ≥0.5 cm² copper area under the tab (DPAK package) and case temperature maintained at ≤102 °C. Derating applies above this temperature per Figure 2 in DS2762.

Does ACST435-8B require an external heat sink?

No external heat sink is required for 4 A operation if the DPAK package is soldered to ≥0.5 cm² of 35 µm-thick copper on the PCB, achieving R_th(j-a) ≈ 70 °C/W. For higher ambient temperatures or sealed enclosures, forced airflow or additional copper improves thermal margin.

Can ACST435-8B replace a standard triac in existing designs?

Yes-it is pin-compatible with industry-standard DPAK triacs and offers enhanced functionality: integrated overvoltage clamping, higher dV/dt immunity, and guaranteed 4 A rating without snubbers. Layout changes are minimal, but gate resistor value must be updated to 68 Ω per Figure 17.

How does the overvoltage clamping function during an IEC 61000-4-5 surge?

When a 2 kV surge exceeds V_CL (≥850 V), the device enters low-impedance conduction for <10 ms, diverting surge current through the load. After zero-crossing, it fully recovers blocking capability-no latch-up or parameter drift occurs, validated for ≥10 repetitive tests.

ACST435-8B Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: ACS™/A.S.D®

Package/Case:: TO-252-3, DPAK (2 Leads + Tab), SC-63

Packaging:: Tube

Product Status:: Active

Triac Type:: Standard

Voltage - Off State:: 800 V

Current - On State (It (RMS)) (Max):: 4 A

Voltage - Gate Trigger (Vgt) (Max):: 1.1 V

Current - Non Rep. Surge 50, 60Hz (Itsm):: 30A, 32A

Current - Gate Trigger (Igt) (Max):: 35 mA

Current - Hold (Ih) (Max):: 25 mA

Configuration:: Single

Operating Temperature:: -40°C ~ 125°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: DPAK

ACST435-8B FAQ

1.How can I place an order for ACST435-8B through Aetrix?

Please submit a Request for Quotation (RFQ) for ACST435-8B on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for ACST435-8B reliable?

The price and inventory of ACST435-8B are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ACST435-8B is usually 5 days.

3.What payment methods are accepted for ACST435-8B?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ACST435-8B transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for ACST435-8B?

ACST435-8B orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your ACST435-8B order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for ACST435-8B?

For technical support, including ACST435-8B datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ACST435-8B requirements.

6.How does Aetrix verify that ACST435-8B is sourced from the original manufacturer or authorized distributors?

All ACST435-8B products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that ACST435-8B meets industry standards.

7.What is the process for return or replacement of ACST435-8B?

All ACST435-8B units undergo pre-shipment inspection (PSI). If there is an issue with ACST435-8B, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The ACST435-8B part is unused and in its original packaging.

Return procedure for ACST435-8B:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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