AAT3128_08 Datasheet, PDF (10/12 Pages) Advanced Analogic Technologies – RGB LED Fashion Lighting Controller

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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 connec-
tions, size or area, material composition, and ambient
temperature. Capacitor ESR is typically measured in mil-
liohms for ceramic capacitors and can range to more
than several ohms for tantalum or aluminum electrolytic
capacitors.
Ceramic Capacitor Materials
Capacitors used in AAT3128 applications range in value
from 0.47μF to 2.2μF. Nominally a 1μF capacitor with a
minimum voltage specification exceeding 6V is recom-
mended. Ceramic capacitors in this range are typically
composed of X7R, X5R, Z5U, or Y5V dielectric materials.
The use of X5R and X7R dielectric capacitors is strongly
recommended due to their inherent low ESR characteris-
tics and improved tolerance specifications over the
device operating temperature range.
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AAT3128
RGB LED Fashion Lighting Controller
Capacitors that are physically larger will have a lower
ESR when compared to a smaller case size capacitor
made from an equivalent material. These larger devices
can improve circuit transient response when compared
to an equal value capacitor in a smaller package size.
Layout Considerations
The AAT3128 is a high-performance device that operates
with a high switching frequency. To ensure optimal device
performance and accommodate the fast switched capaci-
tor transients generated by the AAT3128, special atten-
tion should be given to the printed circuit board (PCB)
layout. The PCB traces connecting C1 and C2 experience
fast current transients. As a result, the trace lengths for
C1 and C2 should be minimized by placing the compo-
nents as closely as possible to the IC. This will minimize
path resistance and reduce ringing due to the inductance
associated with trace length. For best IC performance, C_IN
and C_OUT are placed as closely as possible to the IN and
CP pins and are connected to a solid ground.
AAT3128 Evaluation Board Layout
Figure 3: AAT3128 Evaluation Board
Component Side PCB Layout.
Figure 4: AAT3128 Evaluation Board
Solder Side PCB Layout.
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