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Infineon Claims First 15 V Trench Power MOSFETs in a PQFN Package

November 30, 2023 by Jake Hertz

The new FETs aim to provide more efficient operation for lower-power electronic systems.

A major design consideration in power electronics systems is power efficiency: a criterion that largely comes down to the power efficiency of the components themselves. For this reason, the industry has seen a recent push for power MOSFETs with lower RDS(on),which translates directly to greater power efficiency.

This week, Infineon introduced the OptiMOS 7, its their newest family of power FETs, which they claim is the industry’s first 15 V trench power FETs in a PQFN package.
 

The OptiMOS 7 devices are touted to be the first 15 V trench power FETs in a PQFN package.

The OptiMOS 7 devices are touted to be the first 15 V trench power FETs in a PQFN package. Image used courtesy of Infineon

 

Naturally, this new family comes with significant performance improvements over previous generations, but what underlies this enhanced performance, and how does a lower breakdown voltage play a crucial role in the efficiency of these FETs?

 

DC-DC Conversion with Low Output Voltages

Infineon's OptiMOS 7 family is a group of 15 V MOSFETs tailored for DC-DC conversions with low output voltages, particularly in server and computing environments. 

As compared to previous generations, the new OptiMOS 7 series offers a substantial improvement in performance. When compared to the OptiMOS 5 25 V FETs, for example, the new family achieves around a 30% reduction in Rds(on) and FOMQg, and approximately a 50% reduction in FOMQoss, primarily achieved by lowering the breakdown voltage. This reduction in resistance and figure of merit translates to enhanced efficiency and power management in high-demand environments​​.

 

The normalized drain-source on resistance of the ISK018NE1LM7.

The normalized drain-source on resistance of the ISK018NE1LM7. Image used courtesy of Infineon

 

Looking at the ISK018NE1LM7 family member datasheet, for example, we see impressive technical specifications. It features a very low RDS(on) of 1.8 mΩ and a pulsed current capability of more than 500 A.

The thermal resistance junction to case-bottom is a notable 1.6 ℃/W, demonstrating excellent thermal management capabilities. The small 4 mm² footprint package of this FET also allows for significant space savings and PCB layout flexibility​​.

Additionally, the ISK018NE1LM7 boasts a gate charge of 1.9 nC and an output charge of 6.7 nC, indicating efficient switching performance. These features, combined with ultra-low package parasitics and a small package outline, make this device a top fit for high-ratio DC-DC conversion applications, offering reduced conduction losses and high efficiency​​​​.

 

The Significance of 15 V Power MOSFETs

When we talk about power FETs, we often think the higher the breakdown voltage the better. So why would Infineon be interested in developing a 15 V FET?

The need for 15 V MOSFETs in modern electronics is largely driven by the increasing demands for high efficiency and miniaturization in various applications. In particular, the efficiency of these devices is closely tied to their breakdown voltage characteristics.

For starters, the efficiency of a FET can be largely attributed to its on-state resistance. Lower breakdown voltages in FETs lead to a reduction in the RDS(on), thereby improving efficiency.

This reduction is because the construction of a FET capable of withstanding lower voltages requires less robust, and thus less resistive, materials and structures. As the breakdown voltage decreases, the need for thick, heavily doped layers in the transistor diminishes, which in turn reduces the resistance of the current path.

 

The relationship between RDS(on) and breakdown voltage.

The relationship between RDS(on) and breakdown voltage. Image used courtesy of Renesas

 

How Carrier Mobility Factors In

Another aspect to consider is the relationship between the breakdown voltage and the carrier mobility in the semiconductor material of the FET. Carrier mobility is a measure of how quickly charge carriers (electrons and holes) can move through the semiconductor material under the influence of an electric field.

In lower breakdown voltage FETs, the semiconductor material can be designed to have higher carrier mobility, which enhances the conductivity and reduces resistive losses, further contributing to power efficiency.

Moreover, FETs with lower breakdown voltages tend to have smaller geometries, which is advantageous for high-frequency operations. Smaller device geometries reduce the capacitance within the FET, which in turn minimizes the switching losses.

This is particularly important in applications where FETs are switched on and off rapidly, such as in switching power supplies and inverters in renewable energy systems.

 

Moving to 15 V Devices

The move towards 15 V MOSFETs, as exemplified by the OptiMOS 7, shows Infineon’s recognition of the need for power devices that are high-performing and adaptable to the stringent demands of modern electronics.

As the industry continues to evolve, it is clear that innovations like the OptiMOS 7 will play a pivotal role in shaping the future of power electronics that are more efficient, reliable, and versatile.