AAT2803 datasheet(15/16 Pages) AAT

15 / 16 page

Capacitor Characteristics

Ceramic composition capacitors are highly recom-

mended over all other types of capacitors for use

with the AAT2803. Ceramic capacitors offer many

advantages over their tantalum and aluminum elec-

trolytic counterparts. A ceramic capacitor typically

has very low ESR, is lowest cost, has a smaller

PCB footprint, and is non-polarized. Low ESR

ceramic capacitors help maximize charge pump

transient response. Since ceramic capacitors are

non-polarized, they are not prone to incorrect con-

nection damage.

Equivalent Series Resistance

ESR is an important characteristic to consider when

selecting a capacitor. ESR is a resistance internal

to a capacitor that is caused by the leads, internal

connections, size or area, material composition,

and ambient temperature. Capacitor ESR is typi-

cally measured in milliohms for ceramic capacitors

and can range to more than several ohms for tanta-

lum or aluminum electrolytic capacitors.

Ceramic Capacitor Materials

Ceramic capacitors less than 0.1μF are typically

made from NPO or C0G materials. NPO and C0G

materials typically have tight tolerance and are sta-

ble over temperature. Larger capacitor values are

typically composed of X7R, X5R, Z5U, or Y5V

dielectric materials. Large ceramic capacitors, typ-

ically greater than 2.2μF, are often available in low-

cost Y5V and Z5U dielectrics, but capacitors

greater than 1μF are not typically required.

Capacitor area is another contributor to ESR.

Capacitors that are physically large will have a lower

ESR when compared to an equivalent material

smaller capacitor. These larger devices can improve

circuit transient response when compared to an

equal value capacitor in a smaller package size.

AAT2803

Six-Channel White LED Backlight

Charge Pump with Flash

2803.2006.12.1.6

AAT2803 Datasheet(PDF) 15 Page - Advanced Analog Technology, Inc.