In modern power electronics design, selecting the right MOSFET is critical for balancing efficiency, size, cost, and supply chain stability. This article takes two representative MOSFETs from onsemi—FDC645N (N-channel) and FDD86367 (N-channel)—as benchmarks, analyzes their design focus and application scenarios, and evaluates two domestic alternative solutions: VB7322 and VBGE1805. By clarifying parameter differences and performance orientations, we provide a clear selection guide to help you find the most suitable power switching solution for your next design.
Comparative Analysis: FDC645N (N-channel) vs. VB7322
Analysis of the Original Model (FDC645N) Core:
This is a 30V N-channel MOSFET from onsemi in a compact TSOT-23-6 package. It is specifically designed to enhance total efficiency in DC/DC converters, whether used with synchronous switching or traditional PWM controllers. Key advantages include low gate charge, low on-resistance (30mΩ at 4.5V), fast switching speed, and a continuous drain current of 5.5A, making it ideal for space-constrained, efficiency-sensitive applications.
Compatibility and Differences of the Domestic Alternative (VB7322):
VBsemi’s VB7322 is offered in an SOT23-6 package and serves as a pin-to-pin compatible alternative. Electrically, it shows slight improvements: a lower on-resistance of 27mΩ at 4.5V (vs. 30mΩ for FDC645N) and a higher continuous current rating of 6A (vs. 5.5A). Both share a 30V drain-source voltage rating, making VB7322 a performance-enhanced drop-in replacement.
Key Application Areas:
Original Model FDC645N: Optimized for high-efficiency DC/DC conversion in portable devices, IoT modules, and low-power synchronous buck converters where fast switching and low losses are critical.
Alternative Model VB7322: Suitable for the same applications as FDC645N but offers better conduction performance and current handling, ideal for designs requiring margin or upgraded efficiency within 30V systems.
Comparative Analysis: FDD86367 (N-channel) vs. VBGE1805
Unlike the small-signal FDC645N, the FDD86367 is designed for high-power applications where low resistance and high current capability are paramount.
Analysis of the Original Model (FDD86367) Core:
This 80V N-channel MOSFET in a TO-252 (DPAK) package delivers robust performance: an extremely low on-resistance of 4.2mΩ at 10V (typical 3.3mΩ), a continuous drain current of 100A, and a typical total gate charge of 68nC. It features UIS capability and is optimized for applications demanding high power density and reliability.
Compatibility and Differences of the Domestic Alternative (VBGE1805):
VBsemi’s VBGE1805, also in a TO-252 package, provides a competitive alternative with enhanced specifications: a slightly higher on-resistance of 4.6mΩ at 10V but a superior continuous current rating of 120A (vs. 100A). Both are rated for 80V drain-source voltage, making VBGE1805 suitable for high-current upgrades.
Key Application Areas:
Original Model FDD86367: Ideal for powertrain management, solenoid and motor drives, and high-current DC/DC converters in automotive, industrial, and power systems where low conduction loss and high reliability are essential.
Alternative Model VBGE1805: Targets similar high-power applications but offers higher current handling (120A), making it a strong choice for designs requiring increased power margins or upgraded drive capabilities in 80V systems.
Conclusion
This comparison reveals two clear selection paths:
For compact, efficiency-focused N-channel applications around 30V, the original FDC645N—with its optimized low RDS(on) and fast switching—remains an excellent choice for DC/DC converters in space-constrained designs. Its domestic alternative VB7322 offers a pin-to-pin compatible solution with slightly better on-resistance and current rating, providing an efficient upgrade or backup option.
For high-power N-channel applications up to 80V, the original FDD86367 stands out with its extremely low 4.2mΩ RDS(on) and 100A current capability, making it a robust solution for motor drives and power management. The domestic alternative VBGE1805 delivers a performance-enhanced option with 120A current rating, suitable for designs demanding higher power density and upgraded performance.
The core insight: selection depends on precise requirement matching. In a diversified supply chain, domestic alternatives like VB7322 and VBGE1805 not only offer reliable backups but also provide parameter enhancements, giving engineers greater flexibility in design trade-offs and cost control. Understanding each device’s design philosophy and parametric implications is key to maximizing its value in your circuit.