AAT3340_08 Datasheet, PDF (11/14 Pages) Advanced Analogic Technologies – High Efficiency 1x/1.5x Charge Pump

ChargePump^TM
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
Ceramic capacitors less than 0.1μF are typically made
from NPO or C0G materials. NPO and C0G materials
have tight tolerance and are stable over temperature.
Capacitors with large values are typically composed of
X7R, X5R, Z5U, or Y5V dielectric materials.
Large ceramic capacitors, greater than 2.2μF, are often
available in low-cost Y5V and Z5U dielectrics, but capac-
itors greater than 1μF are usually not required for
AAT3340 applications.
PRODUCT DATASHEET
AAT3340
High Efficiency 1x/1.5x Charge Pump
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.
Thermal Protection
The AAT3340 has a built-in thermal protection circuit
that will shut down the charge pump if the die tempera-
ture rises above the thermal limit, as is generally the
case during short-circuit event of the V_OUT pin.
Evaluation Board Layout
When designing a PCB for the AAT3340, the key require-
ments are:
1. Place the two flying capacitors, C1 and C2, as close
to the chip as possible, otherwise the 1.5X mode
performance will be compromised.
2. Place the input and output decoupling capacitors as
close to the chip as possible to reduce switching
noise and output ripple.
3340.2008.07.1.1
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