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Home > Products > Discrete Semiconductor Products > Thyristors > TRIACs

STMicroelectronics T1235T-8T

Name: T1235T-8T
Brand: STMicroelectronics
SKU: T1235T-8T
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: T1235T-8T

Manufacturer:: STMicroelectronics

Category:: TRIACs

Package:: TO-220-3

Datasheet:: T1235T-8T.pdf

Description:: TRIAC ALTERNISTOR 800V 12A TO220

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Product details

Overview

T1235T-8T from STMicroelectronics is a snubberless, medium-current, three-quadrant Triac in TO-220AB package rated for 12 A RMS on-state current, 800 V repetitive peak off-state voltage (VDRM/VRRM), and 35 mA maximum gate trigger current (IGT). It enables robust AC line switching and phase-angle control in motor drives, lighting, and overvoltage crowbar protection without requiring external snubber circuits when operated within datasheet-defined limits.

For engineers reviewing the T1235T-8T datasheet, T1235T-8T pinout, T1235T-8T application, or T1235T-8T equivalent, key selection criteria include commutation robustness (dV/dt ≥ 1000 V/µs at Tj = 150 °C), high static/dynamic dI/dt capability (≥ 6 A/ms at Tj = 150 °C), and ECOPACK2-compliant lead-free packaging for industrial-grade reliability.

Technical Context

This Triac operates across all three quadrants (I, II, III) with symmetrical triggering characteristics, enabling bidirectional AC conduction without polarity constraints. Its gate sensitivity (IGT ≤ 35 mA) and low threshold voltage (VTO ≤ 0.85 V at Tj = 150 °C) support direct drive from microcontrollers or optocouplers.

Designed for snubberless operation, it achieves high commutation immunity via optimized silicon structure: dV/dt immunity reaches 2000 V/µs at Tj = 125 °C with gate open, and critical rate of decrease of main current (di/dt)c remains ≥ 12 A/ms at Tj = 125 °C under specified reapplied dV/dt conditions.

Key Specifications

Parameter	Value and Actual Design Meaning
IT(RMS)	12 A - Sustains continuous AC load current up to 12 A at case temperature 131 °C without derating.
VDRM / VRRM	800 V - Blocks repetitive 50/60 Hz AC line surges up to 800 V peak at junction temperature 125 °C.
IGT	35 mA - Maximum gate current required to reliably trigger conduction in all three quadrants.
dV/dt (min)	1000 V/µs - Minimum rate of rise of off-state voltage tolerated at Tj = 150 °C with gate open, ensuring noise immunity.
(di/dt)c	6 A/ms - Minimum critical rate of decrease of main current before commutation failure at Tj = 150 °C.
Rth(j-c)	1.3 °C/W - Thermal resistance from junction to case enables efficient heatsink coupling for high-power dissipation.
ECOPACK2	Compliant - Halogen-free epoxy, lead-free plating, UL94 V0 rating for environmental and safety compliance.

Pinout & Package

Package: TO-220AB - Through-hole, single-ended heat-transfer package with isolated mounting tab, 2.0 g mass, and recommended screw torque of 0.4–0.6 N·m.

Pin/Terminal	Circuit Role	Design Meaning
A1 (MT1)	Main Terminal 1	Reference terminal for gate triggering; forms one side of AC load path with A2.
A2 (MT2)	Main Terminal 2	Second main terminal; polarity relative to A1 defines quadrant of operation (I, II, or III).
G	Gate	Control input; triggers conduction when IGT ≥ 1.75 mA (min) and VGT ≤ 1.3 V applied between G and A1.

Key Features

Feature	Design Value
Snubberless operation	Validated for no-snubber use in phase-control applications when dV/dt and di/dt limits are respected per DS9635.
Three-quadrant triggering	Guaranteed turn-on in Quadrants I, II, and III-enables simplified gate drive without polarity switching circuitry.
High commutation robustness	Supports >1000 V/µs dV/dt and ≥6 A/ms (di/dt)c at 150 °C junction temperature for reliable AC line transients.
Thermal performance	1.3 °C/W junction-to-case thermal resistance allows 12 A RMS operation with standard heatsinking at Tc = 131 °C.
ECOPACK2 compliance	Halogen-free, lead-free, UL94 V0-rated package meets RoHS and WEEE requirements for global industrial deployment.

Applications

Motor Control Circuits

Lighting Dimming Systems

Use Scenario: Speed control of universal motors in power tools and household appliances using phase-angle firing.

IC Role / Device Role / Timing Role: Main AC power switch that modulates RMS voltage delivered to motor windings based on gate timing.

Use Value: Eliminates need for snubber networks, reducing BOM count and PCB area while maintaining stable commutation at full-load currents up to 12 A.

Use Scenario: Leading-edge dimming of incandescent and halogen lamps in residential and commercial fixtures.

IC Role / Device Role / Timing Role: Bidirectional AC switch triggered synchronously with zero-crossing detection to adjust conduction angle.

Use Value: Three-quadrant operation ensures consistent turn-on across AC half-cycles, preventing flicker and audible noise during dimming transitions.

Overvoltage Crowbar Protection

Inrush Current Limiting Circuits

Use Scenario: Fast-acting short-circuit clamp activated by transient overvoltage detection to protect downstream DC supplies.

IC Role / Device Role / Timing Role: High-energy crowbar device triggered into hard conduction to divert fault current and collapse bus voltage.

Use Value: 90 A non-repetitive surge rating (at 50 Hz, 20 ms) and 900 V non-repetitive peak blocking enable safe clamping of high-energy transients.

Use Scenario: Controlled turn-on of capacitive loads (e.g., SMPS input stages) to limit peak inrush current during cold start.

IC Role / Device Role / Timing Role: Soft-start switch that delays full conduction until bulk capacitor voltage rises gradually.

Use Value: Low latching current (IL ≤ 60 mA) and precise gate control allow repeatable, low-jitter turn-on timing for predictable inrush limiting.

Equivalent & Alternatives

The following parts are listed as comparable options for similar Triac-based AC switching applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BT139-600E	Same 12 A IT(RMS), but 600 V VDRM/VRRM and higher IGT (50 mA max); lacks snubberless certification.	Suitable only for lower-voltage AC lines (≤ 230 VAC RMS); requires external snubber for reliable commutation.	Select when cost sensitivity outweighs voltage margin and snubber elimination benefits.
MAC12N8G	12 A rating, 800 V blocking, but two-quadrant (Q1+Q3 only); IGT = 35 mA, Rth(j-c) = 1.5 °C/W.	Cannot replace in Q2/Q4-sensitive circuits (e.g., certain solid-state relay topologies); slightly higher thermal resistance.	Choose only if design restricts triggering to quadrants I and III and accepts marginal thermal derating.

Compared with BT139-600E and MAC12N8G, the T1235T-8T delivers superior system-level reliability in 230/400 VAC environments due to its certified snubberless operation, full three-quadrant compatibility, and tighter thermal resistance-reducing design validation effort and field failure risk.

Availability

T1235T-8T is available at Aetrix Electronics and suitable for motor control circuits, lighting dimming systems, and overvoltage crowbar protection requiring stable component supply and long-term industrial lifecycle support.

Supply support for T1235T-8T 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, digital, and mixed-signal ICs for automotive, industrial, and consumer markets.

The T1235T-8T belongs to ST's high-reliability Triac product line, engineered specifically for snubberless AC power control in harsh industrial environments where voltage transients, thermal cycling, and long service life are critical.

FAQ

Is the T1235T-8T truly snubberless, and under what conditions?

Yes-the T1235T-8T is certified snubberless per DS9635 Rev 4. It operates reliably without external RC snubbers when dV/dt does not exceed 1000 V/µs (at Tj = 150 °C) and (di/dt)c remains above 6 A/ms. These limits must be verified against actual circuit waveforms using worst-case transient models.

What is the maximum allowable junction temperature during continuous operation?

The T1235T-8T supports continuous operation up to +150 °C junction temperature, as confirmed by absolute maximum ratings and thermal characterization curves in DS9635. Derating begins at Tc = 131 °C for full 12 A IT(RMS), requiring appropriate heatsinking to maintain Tj ≤ 150 °C under load.

Can this Triac be driven directly from a 3.3 V microcontroller GPIO?

No-direct 3.3 V GPIO drive is insufficient. With VGT ≤ 1.3 V but IGT ≤ 35 mA, a series current-limiting resistor (e.g., 100 Ω) plus optional buffer stage is required to deliver ≥1.75 mA minimum gate current across all temperatures and quadrants, especially at elevated Tj where IGT increases.

Does the TO-220AB package provide electrical isolation between the mounting tab and internal die?

No-the TO-220AB package used for T1235T-8T has an electrically connected mounting tab tied to A2 (MT2). Isolation requires insulating hardware (e.g., mica washer + shoulder washer) or use of an isolated package variant like TO-220FPAB if galvanic separation is needed.

T1235T-8T Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: Snubberless™

Package/Case:: TO-220-3

Packaging:: Tube

Product Status:: Active

Triac Type:: Alternistor - Snubberless

Voltage - Off State:: 800 V

Current - On State (It (RMS)) (Max):: 12 A

Voltage - Gate Trigger (Vgt) (Max):: 1.3 V

Current - Non Rep. Surge 50, 60Hz (Itsm):: 90A, 95A

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

Current - Hold (Ih) (Max):: 40 mA

Configuration:: Single

Operating Temperature:: -40°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220

T1235T-8T FAQ

1.How can I place an order for T1235T-8T through Aetrix?

Please submit a Request for Quotation (RFQ) for T1235T-8T 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 T1235T-8T reliable?

The price and inventory of T1235T-8T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for T1235T-8T is usually 5 days.

3.What payment methods are accepted for T1235T-8T?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for T1235T-8T transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for T1235T-8T?

T1235T-8T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your T1235T-8T 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 T1235T-8T?

For technical support, including T1235T-8T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your T1235T-8T requirements.

6.How does Aetrix verify that T1235T-8T is sourced from the original manufacturer or authorized distributors?

All T1235T-8T 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 T1235T-8T meets industry standards.

7.What is the process for return or replacement of T1235T-8T?

All T1235T-8T units undergo pre-shipment inspection (PSI). If there is an issue with T1235T-8T, 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 T1235T-8T part is unused and in its original packaging.

Return procedure for T1235T-8T:

1.Submit a request within 90 days.

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

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