STMicroelectronics TXN825RG

Overview

TXN825RG from STMicroelectronics is a 800 V, 25 A RMS insulated TRIAC in TO-220AB package, designed for AC line switching and phase-controlled rectification in solid-state relays, motor soft starters, and AC inrush current limiters. It delivers 314 A non-repetitive surge current (tp = 8.3 ms), supports 1500 V/µs dV/dt immunity at 125 °C, and features UL1557-certified 2.5 kVRMS insulation.

For engineers reviewing the TXN825RG datasheet, TXN825RG pinout, TXN825RG application, or TXN825RG equivalent, key selection criteria include insulated package thermal performance (Rth(j-c) = 2.0 °C/W), gate trigger current range (4–40 mA), on-state voltage (≤1.60 V at 50 A), and high-temperature blocking capability (800 V at Tj = 125 °C).

Technical Context

This device is a three-quadrant, gate-triggered, bidirectional thyristor optimized for mains-frequency AC control. Its clip-assembled construction enhances surge robustness, while ceramic-insulated TO-220AB housing enables direct heatsink mounting without additional isolation hardware.

It operates with low gate drive requirements (VGT ≤ 1.3 V, IGT ≤ 40 mA), maintains stable latching (IL ≤ 90 mA) and holding (IH ≤ 50 mA) currents across –40 to +125 °C, and sustains 800 V repetitive blocking in both directions under full junction temperature stress.

Key Specifications

Pinout & Package

TXN825RG uses a TO-220AB insulated package with three leads: MT1 (Main Terminal 1), MT2 (Main Terminal 2), and Gate (G). The insulated tab (MT2) is electrically isolated from the case, rated for 2.5 kVRMS per UL1557 (E81734), allowing direct heatsink mounting without insulating washers.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BTB24-800CW and Q6025JH4, TXN825RG uniquely combines 800 V blocking, 25 A RMS rating, UL-certified insulation, and 2.0 °C/W thermal resistance-making it optimal for safety-critical, high-voltage, high-surge industrial AC control.

Availability

TXN825RG is available at Aetrix Electronics and suitable for Solid-State Relay (SSR), AC Inrush Current Limiter (ICL), and Motor Soft Starter applications requiring stable component supply, long-term lifecycle support, and traceable sourcing for industrial OEM programs.

Supply support for TXN825RG 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 microcontrollers, power devices, sensors, and analog ICs for automotive, industrial, and consumer markets.

TXN825RG belongs to ST's insulated TRIAC product line, engineered specifically for high-reliability, safety-certified AC power control in mains-connected equipment where isolation, surge resilience, and thermal efficiency are critical.

FAQ

What is the maximum gate trigger current required to ensure reliable turn-on?

The datasheet specifies IGT ≤ 40 mA at VD = 12 V and RL = 30 Ω, with a minimum of 4 mA. For robust operation across temperature and aging, design gate drive circuits to deliver ≥100 mA peak for ≥10 µs to guarantee turn-on under worst-case conditions including elevated junction temperature and parameter spread.

Can TXN825RG be used in zero-crossing switching applications?

No - TXN825RG is a standard phase-control TRIAC without integrated zero-crossing detection. It requires external timing circuitry (e.g., optocoupler + microcontroller) to synchronize gate pulses with AC zero crossings. For true zero-crossing operation, consider ST's T-series ZCD TRIACs like TN1225H-600W.

Is heatsinking mandatory, and what is the minimum recommended heatsink thermal resistance?

Yes - at 25 A RMS, junction-to-case thermal resistance is 2.0 °C/W, and power dissipation exceeds 40 W. To maintain Tj ≤ 125 °C at TC = 83 °C, the heatsink must provide ≤1.5 °C/W thermal resistance (junction-to-ambient), assuming 20–25 °C ambient and forced airflow or medium-sized aluminum extrusion.

Does TXN825RG support four-quadrant triggering?

No - TXN825RG is a three-quadrant TRIAC (QI, QII, QIII only). It does not trigger reliably in Quadrant IV (MT2 negative, gate positive), which simplifies gate drive design but excludes certain legacy snubberless configurations requiring QIV operation.