Toshiba’s New Power MOSFET Aims to Miniaturize Power Systems

In the context of power MOSFETs, one of the most significant device specifications is on-resistance. A determinant of device power efficiency and thermal performance, on-resistance has been a major focus of power transistor manufacturers as they aim to improve their products from generation to generation. 

 

A MOSFET transistor key is soldered out of a computer board. Image used courtesy of Adobe Stock

 

Recently, Toshiba released a new N-channel Power MOSFET they claim offers an exceptional improvement in on-resistance compared to previous generations. As part of this improved on-resistance specification, Toshiba claims the new product can aid in miniaturizing electronic power systems.

 

What is On Resistance?

On-resistance (RDS(on))in a MOSFET is defined as the resistance between the drain and source terminals when the transistor is in the "on" state, meaning it is fully conducting. It is an important parameter in power electronics because it affects a system's overall efficiency and thermal performance.

In the context of a MOSFET, the "on" state refers to when a suitable voltage is applied to the gate terminal (i.e., VGS>VTH), inducing a conductive channel between the drain and source. The channel's conductivity is determined by the density of charge carriers (electrons or holes, depending on the type of MOSFET), which, in turn, determines the RDS(on), where conductivity is the inverse of resistance.

 

MOSFET RDS(on) modeled by a resistor in series with the transistor channel. Image used courtesy of All About Circuits

 

So why do transistors have on-resistance? When an electric current flows through any material, it encounters some resistance due to the interactions between the charge carriers (e.g., electrons) and the material's atomic structure. Even in a semiconductor material like silicon, which forms the basis of a MOSFET, these interactions are inevitable. This effect results in energy losses manifested as heat. 

On-resistance is, thus, a vital parameter, particularly for power devices like MOSFETs, where high current and voltage levels can lead to significant heating. Designers aim to minimize the Rdson to improve efficiency, reduce thermal challenges, and potentially enable smaller, more energy-efficient devices. However, the on-resistance is also a function of the MOSFET's physical dimensions and the technology used in its fabrication. Hence, there's always a trade-off between minimizing Rdson and managing other design constraints.

 

Toshiba’s New MOSFET

Recently, Toshiba released an all-new 100 V N-Channel Power MOSFET.

The TPH3R10AQM has been fabricated using Toshiba's advanced U-MOSIX-H process technology, which, the company claims, allows for significantly reduced RDS(on). To quantify this, the new device offers an on-channel resistance of 3.1 mΩ (max), representing a 16% decrease from Toshiba’s previous generation devices. With a decreased RDS(on), Toshiba claims that the TPH3R10AQM significantly reduces energy losses and, thus, heat generation when current flows through the device, making this device ideal for power supply circuits in equipment that require high efficiency and space-saving, such as server power supplies, base station power amplifiers, and switch-mode power supplies.

 

Internal connections of the TPH3R10AQM. Image used courtesy of Toshiba

 

Other notable specifications include a high continuous drain current (Id) of 100 A and a pulse drain current, (Idp) rating of 400 A, which indicates its capacity to handle substantial current surges for short periods. Additionally, Toshiba boasts the device’s low gate threshold voltage, Vgs(th), of between 2.0 V and 4.0 V, enabling it to operate effectively at lower gate-source voltages. 

In terms of packaging, the TPH3R10AQM uses a compact surface-mount SOP Advance package. This package style provides excellent thermal conductivity, which assists in managing heat dissipation, particularly crucial for power electronics applications.