About Tantalum Capacitor
Tantalum Capacitors are used in electronic devices including portable telephones, pagers, personal computers, and automotive electronics. When selecting between available tantalum capacitors, there are a number of key specifications to keep in mind when designing in a tantalum capacitor. These include capacitance value, capacitance tolerance, dissipation factor, leakage current, and equivalent series resistance (ESR). The designer must also consider the board interface requirements. Tecate tantalum capacitors are available in radial leaded or surface mount configurations.
Capacitance is a measure of the energy storage ability of a tantalum capacitor, given as C = K A/D, where A is the area of the electrodes, D is their separation, and K is a function of the dielectric between the electrodes. The formula yields a result in farads (F), but a farad is so large that the most commonly used values are expressed in microfarads (µf = 10-6F).
The dissipation factor (DF) is the ratio between the resistive and the reactive part of the impedance of the tantalum capacitor submitted to a sinusoidal voltage of specified frequency. It is a measure of the losses in the capacitor.
Leakage current is measured as the current flowing from one conductor to an adjacent conductor through an insulating layer. The leakage current in tantalum capacitors is measured after 3 minutes at 25°C, through a 1k resistor connected in series with the capacitor, and with rated voltage applied.
Equivalent series resistance (ESR) represents the extent to which the capacitor acts like a resistor when charging and discharging. This functions via a resistive element within the capacitor model, found in both the AC and DC domains. The lower the ESR the higher the current carrying ability of the tantalum capacitor.
