STMicroelectronics STTH8S12D

Overview

STTH8S12D from STMicroelectronics is an ultrafast high-voltage silicon rectifier diode in TO-220AC package, rated for 1200 V repetitive peak reverse voltage and 8 A average forward current, with 32 ns typical reverse recovery time and 1.75 V typical forward voltage at 150 °C - optimized as a boost diode in UPS systems.

For engineers reviewing the STTH8S12D datasheet, STTH8S12D pinout, STTH8S12D application, or STTH8S12D equivalent, key selection criteria include reverse recovery performance (trr = 32 ns typ), thermal resistance (Rth(j-c) = 2.3 °C/W), softness factor (S ≥ 2), low leakage (IR ≤ 200 µA at 150 °C), and conduction loss modeling via P = 1.7×IF(AV) + 0.1×IF²(RMS).

Technical Context

The STTH8S12D employs ST's Turbo 2 1200 V process to achieve ultrafast switching with soft recovery characteristics (S ≥ 2), minimizing EMI and voltage overshoot during turn-off. Its low thermal resistance (2.3 °C/W) enables high-power operation up to 175 °C junction temperature without forced cooling.

Designed for hard-switching topologies, it delivers stable dynamic performance across temperature: trr increases only modestly from 32 ns (25 °C) to ~45 ns (125 °C), while IRM remains tightly controlled at 11–15 A under 600 V/8 A/200 A/µs conditions.

Key Specifications

Pinout & Package

TO-220AC package: single-diode configuration with isolated tab (cathode-connected metal flange), 3-pin outline (Anode, Cathode, Case/Tab). Mounting torque: 0.4–0.6 N·m. UL94 V0 epoxy encapsulation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar ultrafast high-voltage rectifier applications.

Compared with MUR812E and VS-8EWH12FN-M3, the STTH8S12D offers the best balance of ultrafast recovery (32 ns), low VF (1.75 V), and lowest thermal resistance (2.3 °C/W), making it optimal for thermally constrained UPS and industrial drive applications requiring both efficiency and reliability.

Availability

STTH8S12D is available at Aetrix Electronics and suitable for uninterruptible power supplies, industrial motor drives, solar inverters, and welding equipment requiring stable component supply and long-term production continuity.

Supply support for STTH8S12D 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 microcontrollers, power devices, sensors, and analog ICs for industrial, automotive, and consumer markets.

The STTH series belongs to ST's Turbo 2 ultrafast rectifier product line, engineered specifically for high-efficiency, high-reliability power conversion in demanding industrial and energy infrastructure applications.

FAQ

Is the STTH8S12D pin-compatible with standard TO-220AC diodes?

Yes - STTH8S12D uses the industry-standard TO-220AC outline with Anode (lead 1), Cathode (lead 2), and electrically connected metal tab (cathode). Mounting hole spacing, lead pitch, and flange dimensions match JEDEC TO-220AC specifications, enabling direct mechanical replacement in existing PCB layouts.

What is the maximum recommended case temperature for continuous operation?

The datasheet specifies IF(AV) = 8 A at Tc = 110 °C, with absolute maximum junction temperature of 175 °C. Using Rth(j-c) = 2.3 °C/W, sustained operation at Tc = 110 °C implies ΔT = 18.4 °C rise, confirming safe thermal margin. Operation above 110 °C case temperature requires derating per Figure 1.

Does the STTH8S12D require a heatsink in all applications?

A heatsink is required for continuous 8 A operation - without it, power dissipation (P ≈ 1.7×8 + 0.1×8² = 20 W) would exceed safe junction limits. At lower currents (<3 A) or pulsed duty cycles (δ < 0.1), natural convection may suffice, but thermal simulation using Zth(j-c) curves (Figure 4) is recommended.

How does the softness factor affect circuit design?

A softness factor ≥2 indicates gradual current decay during reverse recovery, reducing dI/dt-induced voltage spikes and electromagnetic interference. This allows smaller snubbers, relaxed layout constraints for high-di/dt paths, and improved reliability of adjacent switching devices - especially critical in compact UPS and inverter modules.