Application Notes of KEMET T599 Series Automotive Grade Polymer Tantalum Capacitors in Automotive Design-EEWORLD

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Polymer tantalum capacitors are capacitors composed of an anode (tantalum, Ta), a dielectric layer (tantalum pentoxide, Ta2O5) and a cathode (solid polymer, carbon layer and silver layer). Its structure and materials create many advantages of this type of capacitor, such as low ESR, high energy density, small size, low height and high stability and reliability, no noise, safety (no risk of burning), etc.

Through its own long-term technological investment and the long-term strong support of its core suppliers, KEMET launched the industry's first automotive-grade polymer tantalum capacitors (T598 series, 125℃, AEC-Q200) in 2015, meeting the needs of many customers for capacitors with low ESR, high energy density, small size, low height, high stability and reliability, and no noise. They are no longer limited to using ordinary manganese dioxide tantalum capacitors with safety concerns and high ESR, MLCC (noise issues, small capacitance, capacitance decay over time, DC bias phenomenon, etc.) and ordinary aluminum electrolytic capacitors.

In order to meet the application requirements of more automotive customers in more demanding environments, Kemet launched the automotive-grade 150℃ T599 series in 2018. This series is mainly aimed at the application scenarios that require the use of capacitors at 150℃ and above, such as thermal management related to the engine compartment of traditional fuel vehicles and BMS and heat pumps in new energy vehicles. At the same time, the T599 series can also meet the needs of some application scenarios with an ambient temperature of 85~95℃ and a product life of at least 10 years (the product is installed and operates 24hrs*7days*365 days a day), such as AAU (Active Antenna Unit) in 5G macro base stations.

Basic characteristics of T599 polymer tantalum capacitors

Low ESR: 25mΩ~150mΩ

Operating temperature range: -55°C~150°C

Ultra-long life

Small size and low height (3.5*2.8*1.9mm, 7.3*4.3*3.1mm)

In automotive DC-DC application scenarios

Automotive electronics are usually powered by batteries (12V in passenger cars). DC-DC converters are critical to automotive electronics because they step down the +12 VDC battery voltage to +5 V, +3.3 V, +1.8 V, or even lower. This conversion is sometimes done in stages, such as 12V to 5V, and then from 5V to 3.3V. The DC/DC converters themselves generate these actual required DC operating voltages, and the job of the capacitors is to help these converters work and provide a stable, noise-free power supply.

Figure 1. Simplified circuit diagram of +5V to +3.3V

The simplified circuit diagram above shows a typical scenario of how DC/DC is used in automotive electronics to reduce the +5V voltage to +3.3V. In the DC/DC converter circuit, capacitors are required at both the input and output of the converter. The input capacitor (C1) ensures that the converter has a large current available when switching. The output capacitor (C2) ensures that the load (DSP, microprocessor, I/O, USB, etc.) can obtain a large current when the converter switches. C1 and C2, these capacitors, in automotive circuits, must not only meet the capacitance requirements of the circuit, but more importantly, meet the harsh conditions listed in AEC-Q200, including high temperature, and other higher requirements of customers themselves.

Voltage derating curve

If you want to use T599 series capacitors in automotive applications with a maximum temperature of up to 150°C, KEMET recommends that you select the appropriate capacitor based on the actual operating temperature and the voltage derating curve below.