onsemi FQB6N80TM 800V N-Channel MOSFET: Datasheet, Application Circuit, and Replacement Guide
The onsemi FQB6N80TM is an N-Channel Power MOSFET engineered to deliver high efficiency and robustness in demanding power conversion applications. With a drain-to-source voltage (Vds) rating of 800V and low on-state resistance, it is a cornerstone component in switch-mode power supplies (SMPS), power factor correction (PFC) stages, lighting ballasts, and motor control circuits. This article provides a detailed overview of its key specifications, a typical application circuit, and guidance for selecting a suitable replacement.
Datasheet Overview and Key Specifications
The FQB6N80TM is built using onsemi's advanced planar stripe MOSFET technology, which is designed to provide minimal gate charge and low effective output capacitance (Coss). This results in reduced switching losses and improved efficiency in high-frequency switching applications. Some of its most critical electrical characteristics include:
Drain-to-Source Voltage (Vdss): 800V
Continuous Drain Current (Id): 6A at a case temperature (Tc) of 25°C
On-Resistance (Rds(on)): 0.8 Ω (max) when driven by a 10V gate-to-source voltage (Vgs)
Gate Threshold Voltage (Vgs(th)): 2.5V to 5.0V
Total Gate Charge (Qg): 28 nC (typ)
Avalanche Energy Rated (Eas): This specification indicates its ruggedness and ability to withstand unclamped inductive switching (UIS) events, enhancing system reliability.
The device is offered in a TO-220F full-pack insulated package. This isolation allows for easier mounting to a heatsink without the need for an insulating mica washer, simplifying the assembly process and improving thermal performance.
Typical Application Circuit: Power Factor Correction (PFC) Boost Converter
A primary application for the FQB6N80TM is in the critical PFC stage of an AC-DC power supply. The circuit below illustrates its role in a classic boost converter topology.
The circuit operates by switching the MOSFET on and off at a high frequency (e.g., 50-100 kHz). When the MOSFET is on, current builds in the inductor. When it turns off, the inductor's collapsing magnetic field forces current to flow through the diode, charging the output capacitor to a voltage higher than the input peak. A dedicated PFC controller IC generates the gate drive signal (Vgs) and modulates the duty cycle to shape the input current to be sinusoidal and in phase with the input voltage, achieving a high power factor.
Replacement and Cross-Reference Guide
When seeking a replacement for the FQB6N80TM, it is crucial to compare key parameters to ensure compatibility and performance. A suitable alternative must match or exceed the following:
Voltage Rating (800V minimum)
Current Rating (6A or higher)
On-Resistance (Rds(on)): A similar or lower value is preferred for better efficiency.
Gate Charge (Qg): A similar or lower value ensures the existing gate driver can switch the replacement MOSFET effectively.
Package (TO-220F or equivalent): Mechanical compatibility is essential for mounting.
Potential direct or functional replacements could include the Infineon IPA60R800P7XKSA1, STMicroelectronics STP6N80K5, or TI (formerly Fairchild) FCP6N80. Always consult the latest datasheets to verify parametric alignment with your specific design requirements, including switching speed and safe operating area (SOA).
The onsemi FQB6N80TM stands out as a highly reliable and efficient 800V MOSFET optimized for high-voltage switching. Its low gate charge and robust avalanche characteristics make it an excellent choice for improving performance in power supply designs. When replacing it, a meticulous comparison of Vdss, Rds(on), and package thermal performance is paramount for maintaining system integrity.
Keywords:
1. 800V MOSFET
2. Power Factor Correction (PFC)
3. Low Gate Charge
4. Unclamped Inductive Switching (UIS)
5. TO-220F Package
