onsemi FJAFS1720TU

Overview

FJAFS1720TU from ON Semiconductor (formerly Fairchild) is an ESBC™-rated NPN power transistor designed for high-voltage, high-speed switching in cascode configurations with a MOSFET. It delivers 1700 V collector-base breakdown voltage, 12 A DC collector current, and 0.25 V V_CE(sat) at 10 A/3.33 A drive - enabling robust operation in smart meter power stages and industrial HV SMPS.

For engineers reviewing the FJAFS1720TU datasheet, pinout, applications, or equivalent options, key selection criteria include its squared RBSOA up to 1700 V, avalanche rating, absence of Miller capacitance in ESBC™ mode, and TO-3PF package thermal resistance of 2.08 °C/W.

Technical Context

The FJAFS1720TU operates as the bipolar high-voltage switch in an Emitter-Switched Bipolar/MOSFET Cascode (ESBC™) topology, where it is driven by a low-voltage MOSFET (e.g., FDS8817) to eliminate Miller feedback and enable fast, dv/dt-immune turn-off. Its ruggedized high-voltage bipolar process ensures no parasitic transistors and immunity to static dv/dt failures.

It supports inductive load switching up to 1700 V without snubber when h_FE = 5 and I_C = 6 A, with measured inductive current fall time of 24 ns at 5 A and gate-driven conditions. The device's reverse-bias safe operating area (RBSOA) is explicitly rated to 1700 V, distinguishing it from standard BJT SOA limits.

Key Specifications

Pinout & Package

Supplied in a high-voltage TO-3PF molded package with isolated base, collector, and emitter terminals. Pin 2 (Collector) connects directly to the internal die attach pad (DAP) for optimal thermal path and high-voltage isolation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage bipolar switching applications.

Compared with STGD10NB60KD and IXGH32N60B3, the FJAFS1720TU uniquely combines 1700 V RBSOA, avalanche energy rating, and Miller-free ESBC™ operation - making it the only option qualified for unclamped inductive switching in 1–1.5 kV smart grid infrastructure.

Availability

FJAFS1720TU is available at Aetrix Electronics and suitable for smart meter power stages, industrial HV SMPS, and ignition driver modules requiring stable component supply, long-term lifecycle assurance, and traceable high-voltage qualification.

Supply support for FJAFS1720TU 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

ON Semiconductor is a global semiconductor supplier delivering energy-efficient, high-performance silicon solutions for automotive, industrial, cloud computing, and IoT applications.

The FJAFS1720TU belongs to Fairchild's ESBC™ (Emitter-Switched Bipolar Cascode) product line, engineered specifically to replace IGBTs and high-voltage MOSFETs in 800–1700 V switching applications demanding low loss, high reliability, and immunity to dv/dt-induced failure.

FAQ

What is the maximum operating voltage for FJAFS1720TU in ESBC™ configuration?

The FJAFS1720TU achieves a maximum collector-source voltage of 1700 V at turn-off without snubber when used in ESBC™ configuration with h_FE = 5 and I_C = 6 A. This is validated per Figure 18 (ESBC RBSOA) and Table on page 3 of the datasheet. The 1700 V rating applies specifically to the ESBC™ topology - not to standalone common-emitter operation, where V_CEO remains 800 V. Always confirm layout creepage and PCB material CTI for full 1700 V system compliance.

Does FJAFS1720TU require a dedicated gate driver IC?

No, the FJAFS1720TU itself is a bipolar transistor and does not have a gate - it uses base drive. However, in its intended ESBC™ configuration, it pairs with a low-voltage MOSFET (e.g., FDS8817) that *does* require standard 10 V gate drive. The FJAFS1720TU base is driven by the MOSFET's source, eliminating isolated high-side drivers. So while FJAFS1720TU doesn't need a gate driver, the overall ESBC™ circuit relies on a compatible MOSFET gate driver stage.

Is FJAFS1720TU pin-compatible with other TO-3PF transistors like MJE13009?

No - although both use TO-3PF packages, FJAFS1720TU has Base–Collector–Emitter pinout (1–2–3), whereas MJE13009 uses Base–Emitter–Collector (1–2–3). Swapping them will cause immediate circuit failure. The FJAFS1720TU pinout is confirmed in Figure 1 and "Pin Configuration" section of the datasheet. Always verify pin mapping using the official marking "J1720" and physical orientation before PCB integration.

Can FJAFS1720TU be used in linear amplifier applications?

No - the FJAFS1720TU is optimized exclusively for saturated switching operation in ESBC™ or hard-switched configurations. Its squared RBSOA, avalanche rating, and low V_CE(sat) are specified only for switching duty. Linear operation risks secondary breakdown due to localized hot-spot formation, and no Safe Operating Area (SOA) curves are provided for analog biasing. Use only as a switch, not as a linear pass device.

What thermal interface material is recommended for FJAFS1720TU in TO-3PF package?

A thermally conductive, electrically insulating pad or grease rated for ≥200°C continuous operation is recommended, such as Bergquist Sil-Pad 2000 or Wakefield-Vette 1140. The TO-3PF's Pin 2 (Collector) connects directly to the DAP, so thermal interface must cover the full DAP surface (15.3 × 14.3 mm per Figure 33) and withstand 2.08 °C/W junction-to-case resistance. Avoid silicone-based pastes if long-term stability above 150°C is required; ceramic-filled pads offer better aging performance.