With the rapid development of automotive electrification and intelligence, the role of electronic components in vehicles has become increasingly critical. Among them, NTC thermistors (Negative Temperature Coefficient Thermistors) and crystal units (Timing Device Crystals) play indispensable roles in temperature monitoring and frequency synchronization, respectively. NTC thermistors are primarily used in battery management systems (BMS), motor and power electronics thermal management, charging system protection, and in-cabin temperature control, ensuring stable vehicle operation under varying temperature conditions while enhancing system safety and energy efficiency. On the other hand, crystal units provide precise frequency signals for in-vehicle communication (CAN, Ethernet, V2X), autonomous driving radar and camera modules, power electronics control, and infotainment systems, ensuring data synchronization and reliable operation between systems. This article explores the applications and development of NTC thermistors and crystal units in automotive electrification, as well as the related solutions offered by Murata.
Applications of NTC thermistors in automotive electrification
NTC thermistors are resistors that are sensitive to temperature changes, with their resistance decreasing as temperature increases. This characteristic makes them suitable for applications such as temperature measurement, compensation, and protection. NTC thermistors have high sensitivity, allowing them to respond quickly to temperature variations. They also feature a wide temperature range, making them applicable in both low- and high-temperature environments (-50°C to 300°C). With high stability, they are ideal for long-term use, offering minimal error and compact size with high reliability, making them suitable for embedded circuits and space-constrained applications.
With the electrification of the automotive industry, NTC thermistors are widely used in temperature monitoring and management to ensure the safety and stable operation of motors and electronic systems. NTC thermistors are primarily applied in Battery Management Systems (BMS) to monitor the temperature of lithium battery packs in electric vehicles (EVs) and hybrid electric vehicles (HEVs). This ensures that the battery operates within a safe range, preventing overheating or low-temperature effects on performance and lifespan. Additionally, NTC thermistors can work in conjunction with Battery Management Controllers (BMC) to achieve precise temperature compensation and overheat protection.
On the other hand, NTC thermistors can be used for temperature monitoring in motors and inverters, tracking the temperature of motor windings and power electronic devices (such as IGBT modules) to prevent overheating damage, thereby improving system efficiency and lifespan. NTC thermistors can also be applied in temperature protection for charging systems. In both DC fast charging and AC slow charging systems, they monitor the temperature of charging stations and in-vehicle charging modules, preventing overheating damage to circuits and ensuring that Power Management ICs (PMICs) and power devices (MOSFETs, IGBTs) operate within a safe temperature range.
In air conditioning and cabin comfort systems, NTC thermistors are used in automotive seat heating and HVAC (Heating, Ventilation, and Air Conditioning) systems to maintain a comfortable in-car temperature and enhance energy efficiency. For LED lighting and electronic device thermal management, NTC thermistors are used in LED headlights and in-car display screens to monitor temperature, preventing overheating that could affect brightness and lifespan.
NTC thermistors play a crucial role in temperature detection, overheat protection, and energy efficiency optimization in automotive electrification. As electric vehicle technology advances, high-precision, miniaturized, and high-temperature-resistant NTC thermistors will become indispensable components in automotive electronic systems.
NTC thermistors meeting high reliability demands for automotive applications
With the advancement of autonomous driving and IoT technology in the automotive market, the number of installed electronic components continues to increase, leading to higher circuit board density. Additionally, as ADAS/TELEMATICS devices become more functional, the issue of heat generation due to increased electronic component loads has become more severe. Consequently, the demand for overheat detection and temperature monitoring continues to grow.
Murata has introduced a series of NTC thermistors, leveraging its long-standing expertise in process technology to develop the NCU series, featuring the highly reliable 0603M size (0.6 x 0.3 x 0.3mm). Compared to previous models (1005M size), these thermistors have been reduced in volume by approximately 80% and in mounting area by about 70%. By responding quickly to market demands, Murata further contributes to high reliability needs such as high-density mounting and miniaturization.
The NCU series SMD-type NTC thermistors are designed for automotive temperature detection applications, offering high reliability to meet the stringent requirements of the automotive market. They enable temperature detection and compensation across a wide temperature range.
The NCU series includes the NCU03 series, featuring product lines for both standard and automotive applications. The automotive-grade models can be used in automotive powertrains and safety equipment. The NCU03 series measures 0.6 x 0.3mm (0.2 x 0.1 inches) and offers a resistance value of 10kΩ at 25°C with a tolerance of ±1%. The NCU15 series, measuring 1.0 x 0.5mm (0.4 x 0.2 inches), offers a wide range of product variations with resistance values (25°C) from 33kΩ to 470kΩ and tolerances ranging from ±1% to ±5%. Similarly, the NCU18 series, measuring 1.6 x 0.8mm (0.6 x 0.3 inches), offers diverse product variations with resistance values (25°C) from 10kΩ to 470kΩ and tolerances from ±0.5% to ±5%, meeting a wide variety of application needs.
Murata introduces its latest series of NTC thermistors, the FTI Series, designed to provide innovative temperature sensing solutions for automotive applications, particularly in power modules. This advanced chip-type thermistor is resin-molded, offering electrical insulation while ensuring high performance under extreme temperature conditions.
The FTI Series delivers reliable operation across a wide temperature range of -55°C to 175°C, making it ideal for demanding applications near SiC MOSFETs and IGBT modules. Equipped with upper electrodes that enable direct wire bonding, these thermistors can be mounted close to power semiconductor devices, significantly enhancing thermal response accuracy. Furthermore, the resin molding ensures electrical isolation between the substrate and internal components, allowing safe integration on high-voltage electrodes alongside power semiconductors.
Functions of crystal units and automotive electrification applications
A crystal unit (Timing Device Crystal) is a component that provides a stable frequency (Clock) signal, primarily used for time reference and synchronization control in electronic circuits. The core functions of a crystal unit include having high stability, enabling it to provide precise and stable frequencies to ensure proper circuit system operation. It also features low power consumption, making it suitable for battery-powered applications due to its low energy requirements. Additionally, it offers interference resistance, allowing it to maintain a reliable oscillation frequency under various environmental conditions, making it suitable for harsh environments such as automotive applications. Moreover, it can provide temperature compensation, as certain crystal units (such as TCXO, Temperature Compensated Crystal Oscillators) can offer higher frequency stability across a wide temperature range.
With the rapid advancement of automotive electronics and electrification technology, crystal units have become one of the core components in automotive electronic systems. Their primary application fields include automotive communication and networking systems, such as CAN (Controller Area Network), LIN (Local Interconnect Network), and Ethernet. These in-vehicle communication protocols require precise frequency signals to ensure data transmission stability and synchronization. Additionally, technologies such as 5G V2X (Vehicle-to-Everything) communication require ultra-low jitter and high-stability frequency reference sources to support high-speed vehicle networking applications.
In ADAS (Advanced Driver Assistance Systems) and autonomous driving applications, radar and LiDAR systems require high-precision frequencies to synchronize data processing, improving detection range and resolution. Cameras and image processing units (ISP, Image Signal Processor) also require stable frequencies to ensure synchronization of image data and vehicle control units (ECU).
For battery management and power electronics control systems, Battery Management Systems (BMS) require precise frequency control to monitor and manage battery charging and discharging status, ensuring battery safety and longevity. In motor and inverter control, reliable frequencies are essential to ensure synchronized operation of power electronic components (such as IGBTs and MOSFETs), improving energy efficiency and reducing electromagnetic interference (EMI).
On the other hand, in In-Vehicle Infotainment (IVI) systems, in-car navigation (GPS/GNSS) systems require high-precision frequency synchronization to ensure positioning accuracy. Digital dashboards and in-car displays require stable frequencies to maintain smooth visuals and data synchronization.
In EV (Electric Vehicle) charging management, DC fast charging and wireless charging systems also require precise frequency synchronization for power transmission and communication protocols (such as Power Line Communication, PLC), ensuring efficient and safe charging processes.
Crystal units play a crucial role in automotive electrification applications, including in-vehicle communication, autonomous driving, battery management, infotainment, and charging control. As electric vehicle and smart driving technologies continue to develop, the demand for high-stability, high-temperature-resistant, and vibration-resistant crystal units will continue to grow.
Crystal units with superior quality and unique packaging technology
Crystal units utilize the piezoelectric effect of crystals to generate specific frequencies. They are indispensable for providing clock signals in ICs and LSIs, offering high frequency stability, no need for tuning, and compact size. Today, crystal resonators are widely used in satellite and mobile communications, as well as in automotive, televisions, computers, and DVD players, meeting diverse application requirements.
Murata's CERALOCK crystal units employ unique packaging technology, offering superior quality, mass production capability, and cost-effectiveness. Murata's automotive crystal units meet the demands of next-generation in-vehicle communication standards like Ethernet/FlexRay, supporting load capacitances (Cs) of 6 pF, 8 pF, and 10 pF. The product lineup also includes high-drive-level (600 μW) options and models rated for +125°C/+150°C.
For automotive Ethernet (PHY), Murata's crystal units support ±85 ppm standards, while for FlexRay, they support ±250 ppm. They comply with automotive reliability standards (AEC-Q200), undergoing rigorous testing such as high-temperature storage (+125°C, 1000 hours), temperature cycling (-55°C to +125°C, 1000 cycles), humidity testing (+85°C, 85% RH, DC 6V, 1000 hours), and high-temperature load testing (+125°C, DC 6V, 1000 hours).
Murata's crystal units feature compact, high-reliability packaging, suitable for ECU miniaturization. For example, 2.5 x 2.0 mm and 2.0 x 1.6 mm sizes offer over 60% reduction compared to 3.2 x 2.5 mm sizes. CERALOCK resonators also boast excellent mechanical and climate resistance, including shock and drop resistance.
Additionally, Murata employs unique particle screening technology during production to identify and eliminate defective units that could degrade unit performance. The design also facilitates automatic optical inspection (AOI), with corner electrode shapes that improve solder fillet visibility.
Another feature of the original structure is its resistance to solder cracking. Murata's structure uses a flat substrate and resin sealing. Compared to conventional cavity structures and sealing with glass or metal, the stress on the solder is reduced. Therefore, Murata's resonators have a robust design in terms of resistance to solder cracking in heat cycle testing.
Murata's automotive crystal unit lineup includes the XRCGE_M_F, XRCGB_F_C, XRCGE_F_A, XRCGA_F_A, and XRCGB_F_A series, catering to diverse automotive applications.
Conclusion
As automotive electrification and intelligent technologies continue to evolve, NTC thermistors and crystal units play pivotal roles in vehicle systems. NTC thermistors, with their excellent temperature sensing and protection capabilities, ensure the stable operation of battery management systems and power electronics under varying conditions, enhancing overall vehicle safety and efficiency. Crystal units, with their high precision and low power consumption, provide stable frequency signals for in-vehicle communication, autonomous driving, and infotainment systems, ensuring precise synchronization between electronic components. Moving forward, as technology advances and automotive electronic system requirements grow, these critical components will continue to drive the development of electrification and smart driving. Murata's NTC thermistor and crystal unit solutions offer the safety and stability needed for automotive electrification applications, making them worthy of further exploration and adoption.