T491B475M020AT4254

Lifetime @ Temp.:	2000 Hrs @ 125°C
Failure Rate:	--
Features:	General Purpose
Ratings:	--
Manufacturer Size Code:	B
Lead Spacing:	--
Height - Seated (Max):	0.083" (2.10mm)
Size / Dimension:	0.138" L x 0.110" W (3.50mm x 2.80mm)
Package / Case:	1411 (3528 Metric)
Mounting Type:	Surface Mount
Series:	T491
Operating Temperature:	-55°C ~ 125°C
ESR (Equivalent Series Resistance):	3 Ohm
Type:	Molded
Voltage - Rated:	20V
Tolerance:	±20%
Capacitance:	4.7µF
Part Status:	Active
Packaging:	Tape & Reel (TR)

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Tantalum Capacitors

T491B475M020AT4254 is an axial-leaded tantalum capacitor, one part of the general tantalum capacitor family.

Tantalum capacitors are polarised electrolytic capacitors. They are constructed with two electrodes separated by an electrolyte, usually a solid wetting agent. They offer a distinctive combination of low ESR, large capacitance per unit volume, high dielectric strength, superior temperature and frequency characteristics. Tantalum capacitors are lighter, smaller and offer higher capacitance than comparably-sized aluminum electrolytic capacitors. Therefore, they are frequently used for a wide variety of general-purpose, low power audio and communications applications, especially where space-saving and high capacitance are desired.

An advantage of the construction of tantalum capacitors is that a solid capacitor is much more robust than the liquid electrolyte used in aluminum electrolytic capacitors. Furthermore, the tantalum powder and dielectric used in tantalum capacitors allow them to have higher capacitance values than those available with other types of capacitor like ceramic, paper and mica. Additionally, with careful selection of materials, tantalum capacitors can be manufactured to have very low leakage.

T491B475M020AT4254 is a surface-mount device. The two-terminal AC-certified micro tantalum capacitor has a chip shape which makes it very suitable for automatic insertion with robotics. Available in EIA 0603 and EIA 0805 case sizes, this capacitor has an outer casing constructed of manganese dioxide and tantalum. The inner core of the capacitor is the oxidising tantalum powder which together with the wetting agent (typically an aqueous solution of an alkaline metal hydroxide) form a dielectric layer.

Working Principle
The working principle of tantalum capacitors is based on electrochemical reactions, rather than dielectric polarization as in other types of capacitors. In the simplest cases, one terminal of the capacitor is made of tantalum, while the other is lead. When a voltage is applied to the capacitor, the chemical process creates an electrical charge that acts as a dielectric. The amount of charge created by this process is determined by the voltage applied to the capacitor. As the charge builds up, an electric field is created between the two terminals of the capacitor which stores energy by means of electrostatic attraction and repulsion.

T491B475M020AT4254 is widely used in a variety of areas suchas, computers, telecommunications equipment, medical equipment and various industrial circuits. It is also suitable for digital and RF applicable equipment, especially in audio frequency applications. The capacitor is rated for a voltage of 16 VDC and the temperature range is -55°C to +125°C. The frequency range is from 10 to 100kHz, with the nominal capacitance of 475mF and the maximum ripple current rated at 0.7A.

T491B475M020AT4254 combines the properties of tantalum powder with those of the manganese dioxide and the alkaline wetting agent to produce a capacitor that is extremely reliable, small and with a high capacitance. The advantages of using this device are its low power consumption, high dielectric strength, superior temperature and frequency characteristics and wide range of working conditions. Its applications range from computer electronics to medical equipment, audio frequency applications to digital and RF applications.

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