Driven by user demand for more comfort, safety and functions, the automobile industry has become a rapidly developing market area. Various electronic systems are equipped into modern cars, many of which directly affect the reliability of the car and the safety of the passengers. Conversely, this means that the electronic components used in critical electronic systems must be very reliable. Capacitors are widely used in many automotive electronic systems, and their quality, stability and reliability must be strictly controlled by automakers. Tantalum capacitors and niobium oxide capacitors can improve the performance of automotive systems.
Unlike aluminum electrolytic capacitors, tantalum capacitors and niobium oxide capacitors have no drying effect and thus have more stable electrical parameters (capacitors, ESR, leakage current, etc.), which means that their properties and functions can be consistent and reliable for a long time. The tantalum capacitors and niobium oxide capacitors do not have any piezoelectric effect when compared with multilayer ceramic capacitors. Another advantage of tantalum and niobium oxide devices is better parameter stability in a range of temperature and dc bias. Broadband coupling requires high end capacitors to be stable within a range of temperature and dc voltage. Since there is no piezoelectric effect, the capacitance varies little with temperature and is independent of voltage, so tantalum or niobium oxide capacitors are more suitable for coupling circuits than MLCC.
In order to use tantalum capacitors and niobium oxide capacitors correctly in the design, all important electrical and physical conditions of the target circuit and equipment must be fully considered. Input parameters usually need to provide capacitance values, which can be calculated according to power line filter ratio, maximum pressure drop, etc. Another important parameter to consider when selecting capacitance correctly is the dc operating voltage. The recommended voltage drop is important to use this general rule. For all tantalum capacitors, the reduction range is 50% and the niobium oxide capacitor is 20%, which means that the working voltage of tantalum capacitor is up to half of the rated voltage Vr, and the working voltage of niobium oxide capacitor is 80% of the rated voltage. Following this rule is important because it protects devices from accidental surges and overpressures, which are likely to occur in automobile circuits. However, the tantalum capacitance derating voltage used in the main output circuit is well isolated from the automotive battery line, has a protective effect when overvoltage, and has a slow charging mode (soft start circuit), such as the output of low-power DC/DC converter. In this case, a reduction of as low as 20 per cent is allowed. Working temperature range tell main consideration when we choose capacitance maximum temperature, but also should realize that when more than 85 ℃ high temperature, we must use the additional voltage derating temperature values. Under the actual temperature capacity allows the voltage of dc voltage is known as the largest category (rated voltage is at room temperature 25 ℃ when one category voltage value).
