STMicroelectronics TN805-800B

Overview

TN805-800B from STMicroelectronics is a standard-sensitivity 8 A, 800 V silicon-controlled rectifier (SCR) in DPAK package, designed for phase-controlled AC power switching in motor control, overvoltage crowbar protection, and inrush current limiting. It delivers 8 A RMS on-state current at TC = 110 °C, supports 800 V repetitive peak off-state voltage, and requires 0.5–5 mA gate trigger current (IGT) at 12 V.

For engineers reviewing the TN805-800B datasheet, TN805-800B pinout, TN805-800B application, or TN805-800B equivalent, key selection criteria include dV/dt immunity (≥50 V/µs at Tj = 125 °C), low on-state voltage drop (≤1.6 V at 16 A), thermal resistance (Rth(j-c) = 4.6 °C/W for TO-220FPAB variant; DPAK Rth(j-c) = 1.3 °C/W), and compatibility with standard gate drive circuits using 1 kΩ gate-cathode resistors.

Technical Context

The TN805-800B operates as a unidirectional thyristor requiring gate-triggered latching into conduction, with holding current (IH) ≤25 mA and latching current (IL) ≤30 mA at 25 °C. Its dV/dt immunity of ≥50 V/µs (at Tj = 125 °C, gate open) ensures robustness against false triggering in noisy AC line environments.

It features a threshold voltage (Vt0) ≤0.85 V and dynamic resistance (Rd) ≤46 mΩ at 125 °C, enabling low conduction losses. The device sustains non-repetitive surge current up to 70 A (tp = 10 ms) and I²t rating of 24.5 A²s, supporting transient overload handling in motor start-up and capacitive discharge applications.

Key Specifications

Pinout & Package

DPAK (TO-252) package: surface-mount, 3-terminal, single-die SCR with exposed cathode tab for thermal conduction. Dimensions per DS2118 Rev 9: D = 5.97–6.22 mm, E = 6.35–6.73 mm, L = 1.00–1.78 mm, tab width ≈ 4.5 mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar SCR switching applications.

Compared with TN805-800B, TN815-800B offers superior dV/dt immunity at the cost of higher gate drive demand, while TYN608 provides identical electrical performance in a through-hole form factor with proven long-term reliability in harsh thermal cycling environments.

Availability

TN805-800B is available at Aetrix Electronics and suitable for motor control in power tools, overvoltage crowbar protection in industrial SMPS, and inrush current limiting in AC/DC front-ends requiring stable component supply and consistent parametric performance across production lots.

Supply support for TN805-800B 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, discrete devices, and MEMS sensors for industrial, automotive, and consumer markets.

The TN8 series belongs to ST's high-reliability power thyristor product line, engineered specifically for ruggedized AC power control in cost-sensitive industrial equipment where long-term parametric stability and surge robustness are mandatory.

FAQ

What is the maximum junction temperature for continuous operation?

The TN805-800B has an operating junction temperature range of –40 °C to +125 °C. For continuous RMS current operation at 8 A, case temperature must be maintained at ≤110 °C per datasheet absolute ratings. Exceeding 125 °C risks irreversible degradation of the PN junction and loss of latching capability.

Can TN805-800B be used in DC circuits?

Yes, but only in circuits where the anode-cathode current can be externally interrupted (e.g., via series MOSFET or mechanical contactor) to force commutation. As a natural-commutated SCR, it cannot self-turn-off in pure DC; gate signal only initiates conduction, not termination.

Is a heat sink required for 8 A RMS operation?

A heat sink is not required if PCB copper area under the DPAK tab meets minimum 30 cm² (per Figure 14) and ambient temperature stays below 50 °C. At 8 A RMS with 1.6 V VTM, power dissipation is ~12.8 W; Rth(j-a) drops from 70 °C/W (no copper) to ~25 °C/W with 30 cm², yielding ΔT ≈ 320 °C - thus adequate copper area or forced air is essential.

What gate resistor value is recommended for reliable triggering?

A 100 Ω to 470 Ω series gate resistor is recommended when driving from a 12 V source, limiting peak gate current to 25–120 mA (well below 4 A IGM rating) while ensuring IGT ≥0.5 mA is delivered even at elevated temperature. Values >1 kΩ risk insufficient gate charge under worst-case IGT max and temperature drift.