The need to enhance driving performance, levels of safety, fuel efficiency, and comfort has accelerated the use of electronic modules and assemblies in automotive vehicles; the number of these modules and assemblies is expected to grow even further as manufacturers switch to more advanced propulsion technologies to meet new emission regulations. Modern automobiles already have advanced fuel injection, cruise control, air conditioning, airbag and entertainment systems and it is expected that HEVs will be dominated by electronic modules and assemblies.

Capacitor Applications In Modern Automobiles

Automotive grade capacitors come in a wide variety of types. Electronic systems for automobiles can be classified into safety systems, engine control systems, lighting systems, accessory systems and body control systems. Automotive safety systems include electronic power steering circuits, electronic stability control circuits, and airbag systems. Body control systems include electronic circuits for wiper control, climate control, and keyless entry mechanisms. Capacitors are widely used in all these systems.

A vehicle’s engine bay and drive train are harsh environments that demand capacitors capable of withstanding high temperatures and vibrations.

The high speed communications bus of today’s modern automobile is highly susceptible to transients and EMI emissions, and requires special protection circuits. A special type of capacitor is required for these protection circuits.

Capacitors For Use In General Purpose Electronic Systems

This category of capacitors is used in automotive electronic circuits that are not exposed to harsh environments. These include wiper control circuits, vehicle navigation systems, speech recognition systems, seat control systems etc. Although these capacitors are not required to withstand harsh environments, they are expected to be affordable and miniature to allow the realization of compact modules. Capacitors for use in these automotive systems are also required to provide high stability and reliability.

Tantalum and niobium oxide capacitors are widely used in electronic systems that demand high reliability components. These capacitors offer stable capacitance, equivalent series resistance (ESR), and leakage current, and unlike aluminum electrolytic capacitors, their functionality does not degrade over time.

The piezo effects and temperature and voltage fluctuations of multilayer ceramic capacitors make them less suitable than stable tantalum and niobium devices for these sort of electronic circuits, and tantalum and niobium capacitors are widely used in infotainment, comfort, security and power management systems.

Capacitors For High Temperature Applications

Electronic modules and assemblies for gearbox controllers, clutch controllers, engine management systems and turbocharger sensors experience severe temperature cycling, long periods of high temperature exposure, and severe vibrations. Capacitors used in such modules and assemblies must be capable of withstanding these conditions. High temperature MLCCs, tantalums and some aluminum electrolytics are the types commonly preferred for these applications. All 3 are available in versions rated up to 150°C, while tantalum and MLC devices are available in ratings of 175°C and higher.

Considering that sensors used in ignition systems, oil pressure systems, and engine management systems can be exposed to temperatures of up to 200°C, there is a growing demand for capacitors with higher temperature ratings. For electronic assemblies that are likely to be exposed to temperatures that only a handful of tantalum and MLC capacitors can withstand, silicon capacitors provide an alternative choice. Silicon capacitors that are designed for “under the hood” applications provide stable and reliable performance at temperatures of up to 200°C. In addition, these low profile capacitors have low leakage currents and a low ageing rate at high temperatures, making them a premium option for high-temperature automotive applications.

Capacitors For Transient And EMI Suppression Systems

The automotive environment exposes electronic circuits to transient over-voltages. Suppression of transients is required to ensure reliable performance of electronic modules and assemblies. The alternator and regulator are major sources of transients in an automotive system. The two can produce high energy and severe transients that can considerably affect the reliability and performance of on-board electronic systems. Conversely, the ignition system generates low-level noise.

In addition, the multiplex bus communication network of an automobile is highly susceptible to transients and EMI. The performance of this network can be considerably degraded if no protection is provided. Plastic film and paper and foil capacitors are used for suppressing noise in ignition and charging systems. Multilayer ceramic capacitors are also widely used for suppressing noise in automotive electronic systems.

Outsource your capacitor headaches

Capacitors For High Temperature Applications

Electronic modules and assemblies for gearbox controllers, clutch controllers, engine management systems and turbocharger sensors experience severe temperature cycling, long periods of high temperature exposure, and severe vibrations. Capacitors used in such modules and assemblies must be capable of withstanding these conditions. High temperature MLCCs, tantalums and some aluminum electrolytics are the types commonly preferred for these applications. All 3 are available in versions rated up to 150°C, while tantalum and MLC devices are available in ratings of 175°C and higher.

Considering that sensors used in ignition systems, oil pressure systems, and engine management systems can be exposed to temperatures of up to 200°C, there is a growing demand for capacitors with higher temperature ratings. For electronic assemblies that are likely to be exposed to temperatures that only a handful of tantalum and MLC capacitors can withstand, silicon capacitors provide an alternative choice. Silicon capacitors that are designed for “under the hood” applications provide stable and reliable performance at temperatures of up to 200°C. In addition, these low profile capacitors have low leakage currents and a low ageing rate at high temperatures, making them a premium option for high-temperature automotive applications.

Capacitors For Transient And EMI Suppression Systems

The automotive environment exposes electronic circuits to transient over-voltages. Suppression of transients is required to ensure reliable performance of electronic modules and assemblies. The alternator and regulator are major sources of transients in an automotive system. The two can produce high energy and severe transients that can considerably affect the reliability and performance of on-board electronic systems. Conversely, the ignition system generates low-level noise.

In addition, the multiplex bus communication network of an automobile is highly susceptible to transients and EMI. The performance of this network can be considerably degraded if no protection is provided. Plastic film and paper and foil capacitors are used for suppressing noise in ignition and charging systems. Multilayer ceramic capacitors are also widely used for suppressing noise in automotive electronic systems.