C0G MLCCs Provide Design Advantages for Onboard Chargers

Electric vehicle operators should not have to worry about charging efficiency and thermal stability—they just want highly reliable transportation with the best range per charge and minimum maintenance and repairs. Manufacturers want an onboard charger (OBC) that is as compact as possible. Bridging the goals of operators and manufacturers is a design challenge that is increasingly accomplished by using multilayer ceramic capacitors (MLCCs) with C0G characteristics.

C0G, also called NP0, is a Class 1 dielectric ceramic capacitor with an extremely stable capacitance: near-zero change with a maximum allowable error of ±30 ppm/°C. This provides superior operation that doesn’t change much with temperature, voltage, or age, making it perfect for precise circuits and reliable applications, such as OBCs for EVs. In comparison, Class II MLCCs, such as X7R, experience ±15% drift, and film capacitors typically operate with ±2% drift.

OBCs are high-voltage AC/DC converters used to safely and efficiently utilize grid power to charge EV batteries. C0G MLCCs are prized for high-precision, high-stability functions in power conversion and electromagnetic interference (EMI) filtering. They are used in LLC resonant tank circuits, voltage transient snubber circuits, high-frequency EMI suppression filters, DC bias-sensitive control circuits, and gate drivers and auxiliary power supplies.

With 22 kW output power now common in EV OBCs, capacitors for resonant circuit function must withstand high voltage and deliver low loss to withstand higher power densities in a compact form factor. They have a pivotal role in ensuring overall system efficiency and reliability, which makes C0G MLCCs an attractive design option.

C0G advantages

MLCCs with C0G characteristics have key advantages over traditional film capacitors in these applications. Designers can take advantage of significant reductions in mounting area, suppressed heat generation, and improved transmission efficiency, enabling smaller and more powerful OBCs.

Switching in OBC power stages generates EMI, which can further be amplified by wide-bandgap (WBG) semiconductors like silicon carbide (SiC) and gallium nitride (GaN). These materials enable ultra-fast switching with high efficiency, but they also produce steep voltage transients. These are commonly referred to as high-voltage change over time (dv/dt) events that can exceed 50 kV/µs, which is much higher than in traditional silicon MOSFET designs.

MLCCs with C0G characteristics are inherently stable, non-piezoelectric, and less prone to thermal or electrical drift under high-frequency stress. They excel at pulse handling and low ESL, making them well-suited for snubber circuits and common-mode filtering.

C0G MLCCs exhibit exceptionally low dissipation factors and high quality (Q) capacitance. This combination ensures minimal energy loss and stable resonant behavior, resulting in lower thermal stress and improved power density. They provide superior electrical stability compared to X7R/X5R Class II dielectric MLCCs, offering zero piezoelectric noise and ensuring low dissipation factors and high Q performance, which are critical for high-frequency switching applications.

In snubber networks and EMI filters, high Q components help ensure precise impedance characteristics, enhancing transient suppression and noise filtering effectiveness. For RF systems and precision analog circuits, high Q supports narrowband selectivity and signal integrity, enabling more accurate filtering and frequency control.

With lower equivalent series resistance (ESR) than film capacitors, self-heating is reduced, contributing to a longer lifespan. Also, with a reduction in component count, using C0G MLCCs results in extended mean time to failure (MTTF) for OBC applications.

C0G MLCCs impact EV drivers and owners by enhancing the charging experience, vehicle reliability, and overall perception of build quality. C0G MLCCs contribute to thermal reliability in extreme conditions, improved energy efficiency and range confidence, smooth and quiet operation with reduced EMI, and driver peace of mind.

Design considerations for OBCs

The unique combination of stability, low loss, and compact size makes C0G MLCCs ideal for high-speed and high-precision circuits. But there are trade-offs that designers need to evaluate in deciding whether to use C0G MLCCs, X7R MLCCs, or film capacitors.

Film capacitors provide greater capacitance for high voltage and energy storage, but are generally more costly and bulky options (Figure 1). X7R MLCCs are more compact and cost-effective than film alternatives, but their capacitance can be significantly impacted under DC bias, and they require derating for voltage stability.

Figure 1: Size comparison of a typical 600 V film capacitor (left) and a 3225 package, high-voltage C0G MLCC. (Image source: TDK Corporation)

C0G MLCCs have a small price premium over X7R but ensure greater stability and better performance with no derating required. The cost differential may be offset at least partially by a reduction in the overall number of components, which lowers the total bill of materials.

When designing with C0G MLCCs in EV OBCs or other power-sensitive automotive systems, it pays to take care in component selection. Vendor specifications may be similar, but variances in ESR, ESL, and construction can impact circuit tuning. It's essential not to casually mix vendor components and to validate selections through bench testing or simulations.

C0G MLCCs are replacing film capacitors and X7R MLCCs for many applications, such as the resonant circuits that deliver efficient and high-performance power conversion for OBCs and other critical applications. Ultra stability and miniaturization combined with high voltage make these components an attractive design option.

TDK's high-capacitance C0G MLCCs

In 2025, TDK Corporation expanded its CGA (automotive grade) series and C (commercial and industrial grade) series of surface-mount C0G MLCCs to 10 nanofarads (nF) with what is believed to be the industry’s highest capacitance for a 1,250 V rated product. They are packaged in a 3225 (3.2 x 2.5 x 2.5 mm) case. TDK's high-voltage X7R components, in comparison, are larger and only support up to 630 V.

The C3225 and CGA6P C0G product lines utilize optimized product and process design to deliver high-voltage resistance. They share the 3225 form factor, so designers can utilize them to reduce the physical size and number of MLCCs mounted in series (Figure 2).

Figure 2: Comparison of the mounting area required for similar capacitor banks using film capacitors, lower voltage MLCCs, and higher voltage MLCCs. (Image source: TDK Corporation)

Compared to the alternatives, the TDK C0G MLCCs are optimized to reduce heat generation, which adds to longevity and improves reliability. They are highly suited for resonant and snubber circuits, DC/DC converters, and wireless charging applications in automotive and commercial applications.

The compact size of the TDK components allows designers to deliver AEC-2000 compliant applications that are smaller and more efficient for next-generation automobiles. They ensure reliable performance in harsh conditions, including thermal shock, vibration, and temperature cycling, with a temperature range of -55 to 125°C.

The CGA6P1C0G3B103G250AC automotive-grade MLCC offers capacitance of 10 nF with a ±2% tolerance. The C0G dielectric provides outstanding stability over temperature, and can withstand intense engine compartment temperatures and vibrations. They're particularly useful in high-voltage resonant and snubber circuits, such as those found in EV charging systems and power electronics. The CGA6P1C0G3B103J250AC provides the same capacitance but with a ±5% tolerance.

The C3225 components feature the same packaging and temperature range characteristics but are less costly and designed for more moderate and less regulated commercial and industrial environments. Like the counterpart in the CGA6 line, the C3225C0G3B103G250AC provides a 10 nF capacitance and a high rated voltage of 1,250 V in the same 3225 package with a capacitance tolerance of ±2%, making it suitable for precision applications. The C3225C0G3B103J250AC features a capacitance of 10 nF with a ±5% tolerance.

Conclusion

Designers can confidently replace larger film or electrolytic capacitors, streamline board layouts, and enhance system reliability in next-generation power and automotive systems with C0G MLCCs. TDK’s commercial grade C3225 and automotive grade CGA6P C0G MLCCs provide an appealing option for high-voltage, high-reliability applications with industry-leading capacitance in a compact package for exceptional stability.