Power MOSFETs Suppress Noise in Motor

Power MOSFETs Suppress Noise in Motor-Control Circuits
Vishay Intertechnology introduced a new series of 40-V n-channel power MOSFETs optimized for the noisy environments of motor-control circuits.
The new devices — the SIR5402DP, SIR5404DP, SIR5406DP, and SIR5408DP — are all specifically designed to reduce the risk of unintended switching induced by the gate while limiting switching losses caused by gate noise. Vishay said it addressed the first problem by increasing the minimum gate-source threshold voltage to more than 2.5 V and confronted the second by reducing the QGD/QGS ratios to less than 1.0.
The higher gate-source threshold voltage helps prevent unintended turn-on of the MOSFET in motor-drive circuits, where fast switching speeds can lead to high dv/dt rates. That, in turn, can cause significant LC oscillations between the parasitic inductance of the PCB traces and parasitic capacitance in the MOSFET package. This switching noise may increase the gate voltage enough that it turns on the power transistor, impacting the system’s performance and potentially damaging the power stage in the motor driver.
At the same time, the improved gate-charge ratio further reduces gate-induced voltage fluctuations and the impact of gate noise, improving switching stability and reliability along with overall circuit robustness, said Vishay.
These noise-rejection characteristics are suitable for synchronous rectification and DC-DC conversion stages in brushless DC (BLDC) motor drives, cordless power tools, drones, and other systems requiring reliable operation in noisy conditions. By mitigating the effects of gate noise, the devices also deliver higher performance by reducing the risk of unwanted switching and the power losses that come with it.
Housed in a compact PowerPAK SO-8 package measuring 6.15 × 5.15 mm, they undergo rigorous testing to verify device robustness.
The devices strike a balance between conduction losses and switching performance with typical on-resistance (RDS(on)) values ranging from 0.9 m to 2.5 mΩ at a gate drive of 10 V and gate charge (QG) values from 32.6 to 82 nC.
About the Author
James Morra
Senior Editor
James Morra is the senior editor for Electronic Design, covering the semiconductor industry and new technology trends, with a focus on power electronics and power management. He also reports on the business behind electrical engineering, including the electronics supply chain. He joined Electronic Design in 2015 and is based in Chicago, Illinois.

Facts Only

* Vishay introduced 40-V n-channel power MOSFETs (SIR5402DP, SIR5404DP, SIR5406DP, and SIR5408DP).
* The devices are optimized for noisy motor-control environments.
* The devices reduce the risk of unintended switching induced by the gate while limiting switching losses from gate noise.
* The first problem was addressed by increasing the minimum gate-source threshold voltage to more than 2.5 V.
* The second problem was addressed by reducing the QGD/QGS ratios to less than 1.0.
* Higher gate-source threshold voltage helps prevent unintended turn-on in motor-drive circuits with fast switching speeds, which can cause LC oscillations.
* Improved gate-charge ratio reduces gate-induced voltage fluctuations and the impact of gate noise.
* The devices are suitable for synchronous rectification and DC-DC conversion in BLDC motor drives, cordless power tools, drones, and other noisy systems.
* Devices are housed in a PowerPAK SO-8 package measuring 6.15 × 5.15 mm.
* Typical on-resistance (RDS(on)) values range from 0.9 m to 2.5 mΩ at a gate drive of 10 V.
* Gate charge (QG) values range from 32.6 to 82 nC.

Executive Summary

Vishay Intertechnology introduced a new series of 40-V n-channel power MOSFETs, including the SIR5402DP, SIR5404DP, SIR5406DP, and SIR5408DP, designed for motor-control circuits. These devices aim to reduce unintended switching caused by gate action while minimizing switching losses resulting from gate noise. This was achieved by increasing the minimum gate-source threshold voltage above 2.5 V and reducing the QGD/QGS ratios below 1.0. The increased threshold voltage helps prevent unintended turn-on in motor-drive circuits experiencing fast switching, which can cause LC oscillations between PCB trace inductance and MOSFET package capacitance. Furthermore, the improved gate-charge ratio lessens gate-induced voltage fluctuations, enhancing switching stability and reliability. These noise-rejection features are applicable to synchronous rectification and DC-DC conversion stages in applications like BLDC motor drives and drones, offering higher performance by reducing unwanted switching and power losses while maintaining robustness.

Full Take

The narrative centers on mitigating systemic instability caused by electrical noise within high-speed power switching applications. The core tension lies between achieving high-speed performance and ensuring robust, predictable operation in electrically noisy environments. The solution proposed—adjusting gate threshold voltage and charge ratios—suggests that the failure mode is not just thermal or resistive loss but dynamic electromagnetic coupling leading to unintended state changes. This pattern points toward a recognized engineering reality: switching transients create parasitic oscillations that exploit physical layout constraints (PCB inductance/capacitance) to corrupt control signals, which ultimately impacts device reliability. The implication for system design is that noise rejection must be engineered into the transistor physics rather than being treated as an external mitigation step. A critical question arises regarding the trade-off: while reducing switching noise improves stability, what is the precise energetic cost, beyond loss reduction, associated with setting these voltage and charge boundaries? Furthermore, when deploying these solutions across diverse systems like drones versus industrial motor drives, how do the specific parameters (2.5V threshold vs. QGD/QGS ratios) map onto differing operational margins?

Sentinel — Human

Confidence

This text reads like a standard, fact-based technology announcement, exhibiting the precision and structure typical of human technical journalism rather than purely synthetic generation.

Signals Detected

Moderate sentence length variance and appropriate technical complexity.

Logical flow from problem (noise) to solution (device specs) to application (BLDC drives).

Specific technical details (e.g., QGD/QGS ratios, RDS(on), specific MOSFET part numbers) suggesting direct sourcing.

The tone is purely informational and lacks the characteristic hedging or overly broad generalizations often seen in AI-generated summaries of complex topics.

Human Indicators

The inclusion of highly specific, verifiable technical parameters (e.g., minimum gate-source threshold voltage > 2.5 V, QGD/QGS ratios < 1.0, RDS(on) range) strongly suggests direct reporting from a technical source or press release.

The author bio provides specific career history and location, adding human context.