AAT3120 Datasheet, PDF (11/14 Pages) Advanced Analogic Technologies – 3-Channel Charge Pump For White LED Applications

ESR is an important characteristic to consider when
selecting a capacitor. ESR is a resistance internal
to a capacitor, which is caused by the leads, inter-
nal 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 tan-
talum 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. Large 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 typically not required for
AAT3120 applications.
AAT3120
3-Channel Charge Pump
For White LED Applications
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 AAT3120 has a thermal protection circuit that
will shut down the internal LDO and charge pump
if the die temperature rises above the thermal limit,
as is the case during a short circuit of the OUT pin.
Charge Pump Compatibility
The AAT3120 is pin-compatible with the AAT3113
in TSOPJW-12 packages, with no D4 output.
Compared to the AAT3113, the AAT3120 offers an
improved overall efficiency, wider operating range,
and the ability to drive high-V_F type LEDs (up to
4.3V) at full current from a 3V input condition. The
AAT3120 is well suited for battery-powered appli-
cations using single-cell Lithium-Ion (Li-Ion) batter-
ies (4.2V to 2.8V), Lithium Polymer batteries, and
3-series connected dry cells (3.6V).
3120.2005.11.1.1
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