Onsemi FDS9945 Dual N-Channel PowerTrench MOSFET: Datasheet, Application Circuit, and Pinout Configuration

The Onsemi FDS9945 is a dual N-Channel MOSFET fabricated using advanced PowerTrench® process technology, designed to deliver high efficiency and reliability in power management applications. This device integrates two independent MOSFETs in a compact SOIC-8 package, making it an excellent choice for space-constrained designs requiring high performance. Its key attributes include low on-state resistance (RDS(ON)) and high current handling capability, which minimize conduction losses and improve thermal performance.

Datasheet Overview

The datasheet provides critical specifications for the FDS9945. Key parameters include a drain-to-source voltage (VDS) of 20V, a continuous drain current (ID) of 5.3A per MOSFET, and a low RDS(ON) of 28mΩ at VGS = 4.5V. The device features a low gate charge (Qg) and fast switching characteristics, making it suitable for high-frequency applications such as DC-DC converters, motor drives, and load switches. The datasheet also outlines thermal resistances, safe operating areas (SOA), and maximum ratings, ensuring designers can implement robust circuit protection.

Application Circuit

A common application for the FDS9945 is in synchronous buck converters, where the dual MOSFETs are used as the control and synchronous switches. In such circuits, the low RDS(ON) reduces power dissipation, while the integrated design simplifies PCB layout and minimizes parasitic inductance. The device is also ideal for power OR-ing circuits, battery management systems, and high-efficiency voltage regulators. Designers should incorporate gate drivers optimized for fast switching to maximize performance and avoid voltage spikes.

Pinout Configuration

The FDS9945 is available in an SOIC-8 package. The pinout is standardized:

- Pins 1, 2, and 3: Drain of MOSFET 1

- Pin 4: Gate of MOSFET 1

- Pin 5: Gate of MOSFET 2

- Pins 6, 7, and 8: Drain of MOSFET 2

- The source terminals of both MOSFETs are connected internally and brought out to the exposed thermal pad, which must be soldered to the PCB for effective heat dissipation. Proper pin identification is crucial for avoiding short circuits and ensuring optimal performance.

ICGOODFIND

The Onsemi FDS9945 leverages PowerTrench technology to offer a efficient, compact solution for dual N-Channel applications. Its balance of low RDS(ON), fast switching, and thermal efficiency makes it a standout choice for modern power systems.

Keywords:

PowerTrench MOSFET, Dual N-Channel, Low RDS(ON), Synchronous Buck Converter, SOIC-8 Package