High-Voltage Safety: The SMDY1 Advantage
Image Source: Mouser Electronics
By Dr. Florian Weyland, Director of Product Marketing for the Ceramic Capacitor Division, Vishay Intertechnology
Published April 7, 2026
Optimising High Voltage EV Powertrains with SMDY1 Safety Capacitors
For designing next-generation electric vehicle (EV) architectures, the migration to >800V battery systems presents a dual challenge: managing increased electromagnetic interference (EMI) while maintaining stringent safety standards within a shrinking footprint. Traditional leaded safety capacitors often become assembly bottlenecks and consume excessive vertical space. Vishay’s SMDY1 Automotive Series addresses these hurdles directly, offering the industry’s first surface-mount ceramic disc safety capacitors qualified for Class Y1 automotive applications.
Technical Core: Voltage and Capacitance Performance
When designing filters for onboard chargers (OBCs), DC/DC converters, or power inverters, the component choice is dictated by impulse withstand capability. Class Y capacitors are connected from line to ground. Because failure in this position could lead to a conductive path directly to the vehicle's chassis, these components must meet rigorous safety standards to prevent shock hazards. Class Y1 capacitors are specifically designed to bridge reinforced or double insulation, providing the highest level of protection against transient impulses up to 8000V.
The SMDY1 series is rated for Class Y1 (500VAC) operation per IEC 60384-14. Crucially for your xEV design, these components also carry a 1500VDC rating according to IEC 60384-14 Annex H, providing the necessary overhead for high-voltage DC buses.
The series offers a capacitance range from 470pF to 4700pF with a standard tolerance of ±20 percent. Utilising a Y5U dielectric, the SMDY1 provides stable performance across an operating temperature range of -55 °C to +125 °C. For your high-frequency filtering needs, these capacitors exhibit typical impedance curves optimised for effective common-mode noise suppression in the MHz range.
Engineered for the Assembly Line: The SMD Advantage
One of the most immediate benefits that designers can experience with the SMDY1 series is its surface-mount form factor. By eliminating manual through-hole assembly, designers can utilise standard reflow soldering processes, significantly increasing manufacturing throughput and reducing mechanical stress on the PCB leads.
The physical design is tailored for high voltage isolation without wasting board area. The design ensures a creepage distance of 10mm even in a compact SMD layout, satisfying the reinforced insulation requirements for systems operating under typical automotive pollution levels.
When designing for 800V systems, standard component spacing is often insufficient. The creepage distance—the shortest path along the surface of an insulating material between two conductive parts—must be evaluated to prevent “tracking,” a process where localised deterioration creates a conductive path over time.
According to IEC 60664-1, the required creepage distance depends on the working voltage, the environmental pollution level, and the component's material group. The SMDY1 series utilises a high-quality, flame-retardant epoxy molding that falls into Material Group II, meaning it has a Comparative Tracking Index (CTI) between 400V and 600V.
For an 800V system and under typical automotive conditions (Pollution Degree 2), IEC 60664-1 specifies a basic creepage distance of 5.6mm for Material Group II. This is well below the components’ creepage distance of 10mm for case size C and 14.5mm for case size D. However, in case reinforced insulation must be considered, the distance must be doubled to 14.2mm. The SMDY1 series size code D features a creepage distance of >14.5mm, providing a substantial safety margin even under these extreme considerations.
Another critical variable is the operating altitude. Standard insulation distances are valid up to 2000m above sea level. As altitude increases, lower air pressure reduces the dielectric strength of the air, increasing the risk of arcing. At altitudes of 5000m, the correction factor of 1.48 needs to be considered. For maximum voltage spikes of 2500V and pollution degree 2, the clearance distance increases from 1.5mm to 2.2mm.
Reliability Under Automotive Stress
Automotive environments are notoriously unforgiving. To ensure long-term stability in your design, the SMDY1 series is AEC-Q200 qualified. These components are built to survive the most rigorous stress tests, including:
- 1000 Temperature Cycles: From -55 °C to +125 °C, ensuring ceramic and resin integrity during thermal shocks
- Harsh Humidity Resistance: The series withstands the demanding 85/85/1000h temperature humidity bias test
- Robust Encapsulation: The single-layer ceramic disc is copper-plated on both sides and encapsulated in a flame-retardant epoxy resin (UL 94 V-0) that is also halogen-free
Safety Certifications and Compliance
As a safety-certified component, the SMDY1 series carries full approvals from VDE, UL, CSA, and CQC. This simplifies the end-product certification process, as the components are pre-verified to bridge reinforced insulation. With a dielectric strength of 4000VAC for 60s and an insulation resistance of at least 10,000MΩ, these capacitors provide the “last line of defense” that a system needs against transient impulses up to 8kV.
Conclusion
Vishay’s SMDY1 series is more than just a miniaturised safety capacitor; it is a high-performance solution for the high-voltage demands of modern xEV powertrains. By combining Class Y1 safety ratings with surface-mount efficiency and AEC-Q200 reliability, it allows the streamlining of assembly while meeting the most stringent EMI and isolation standards.
Author Bio
Dr. Florian Weyland serves as Director of Product Marketing for the Ceramic Capacitor Division at Vishay Intertechnology. He is based in Selb, Bavaria, and brings over 6 years of experience in the electronic components sector. Earlier, he completed a PhD (Dr.-Ing.) in Material Science at the Technical University of Darmstadt, blending deep technical expertise with senior product management skills for capacitor technologies.