Since electronics were introduced into the automotive industry the amount of technology in a vehicle has continued to increase. So much so that very soon cars will be close to being supercomputers on wheels. The amount of electronics in automotive applications is expanding rapidly, as more sensors, more computing power, and more electrical power are packed into vehicles every day. This promises to continue into the future, as advancements are made in electrical drive vehicles and autonomous driving vehicles. Automotive environments present special challenges to electrical devices – high temperatures, critical reliability requirements, and long lifetimes, to name a few. KEMET’s Organic Capacitor series (KO-CAPTM) solid polymer tantalum capacitors offer an unmatched solution to those challenges.
The automotive environment creates special challenges for electronics. Unlike many computer applications, automobiles experience vast extremes in conditions – extremely low and high temperatures, extreme humidity, contamination, or vibration and shock. In addition to those harsh conditions, the electronics in automobiles are expected to have a very long, stable, and reliable lifetime and, if they fail, to fail in a safe manner.
KEMET’s polymer tantalum capacitors offer low ESR to minimize power losses and unwanted noise, and they can withstand the high temperatures of automotive applications. Specifically, the T599 tantalum polymer capacitor has excellent characteristics up to 150°C, with an extended life expectancy (demonstrated up to 130,000 hours under certain conditions).
The AEC-Q200 automotive qualification standard is a global standard for passive electrical components to be used in automotive circuits. There is a stringent set of stress tests which, if passed, yield a “qualified” status to a component. KEMET’s T59x series of tantalum polymer capacitors meet and exceed these requirements easily.
Different electronic subsystems in vehicles come with their own unique challenges and requirements for the components used within those systems. Control and safety systems (such as anti-lock brakes, backup cameras, and adaptive headlights) require components with especially long lifetimes and high reliability. The powertrain (which includes the components that generate power and transmit it to the road surface) requires components that can withstand high temperatures and harsh conditions. On-board electronics systems (including navigation, advanced diagnostics, and entertainment) need small, high-speed componentry.
Polymer tantalum capacitors can be used anywhere in an automotive circuit where capacitors are needed, but they are most commonly found in DC/DC converter circuits, which step down the battery voltage to a lower voltage rail for electrical circuits. Automotive batteries output a +12V DC voltage, while most electrical circuits containing processors today run on voltage rails of +5V, +3.3V, +1.8V, or even lower. DC/DC converters help provide these rails and capacitors help those converters function and provide stable, clean power.
Simplified DC/DC converter schematic
The AEC-Q200 standard requires passive components to be tested at rated stress levels for 1,000 hours of operational life. KEMET’s T599 series capacitors are rated for 2,000 hours of operational life at 150°C. When properly derated for voltage and temperature, the T599 series capacitors can be used to support the 8,000-hour high temperature mission profile and even the 130,000-hour (15 year) ultra extended mission profile in the right conditions. Life expectancy and failure rate equations for polymer capacitors can be used to validate them for mission profiles.
In a DC/DC converter circuit, capacitance is required at both the input and the output of the converter. The input capacitor(s) ensure that instantaneous current is available to the converter while it is switching. The output capacitor(s) ensure that instantaneous current is available to the load (DSP, microprocessor, I/O, USB, etc) while the converter is switching. Each of these capacitors, in an automotive application, must not only be designed to meet the capacitance needs of the circuit, but also selected to meet the high temperatures and harsh conditions of the AEC-Q200 standard and beyond.
KEMET’s KO-CAP® T599 series tantalum polymer capacitors offer customers high temperature ratings and long operational life for automotive applications. Offered in capacitances of 33 to 150 µF and voltage ratings of 4 to 35 VDC, these capacitors are ideal for DC/DC converter circuits and other designs in automotive applications.