AAT3129
High Efficiency 1X/1.5X/2X Charge Pump
for RGB Color LED Applications
Ceramic Capacitor Materials
Layout Considerations
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, typi-
cally greater than 2.2µF, are often available in low-
cost Y5V and Z5U dielectrics, but capacitors
greater than 1µF are typically not required for
AAT3129 applications.
The AAT3129 is a high-performance device that
operates with a high switching frequency. To ensure
optimal device performance and accommodate the
fast transients generated by the AAT3129 special
attention should be given to the board layout.
The recommended layout is illustrated in Figure 1.
The 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
components 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, CIN and COUT are placed
as closely as possible to the IN and CP pins and
are connected to a solid ground.
Capacitor area is another contributor to ESR.
Capacitors that are physically large will have a
lower ESR when compared to a smaller 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.
GND
C2
COUT
CIN
C1
GND
Figure 1: Optimal PCB Layout.
3129.2005.11.1.3
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