AAT3220IGY-2.4-T1 AAT [Advanced Analog Technology, Inc.], AAT3220IGY-2.4-T1 Datasheet - Page 9

• Manufacturer Part Number: AAT3220IGY-2.4-T1
• Manufacturer: AAT [Advanced Analog Technology, Inc.]

Applications Information
To assure the maximum possible performance is
obtained from the AAT3220, please refer to the fol-
lowing application recommendations.
Input Capacitor
Typically, a 1µF or larger capacitor is recommended
for C
required for basic LDO regulator operation.
However, if the AAT3220 is physically located any
distance more than one or two centimeters from the
input power source, a C
for stable operation. C
to the device V
ues greater than 1µF will offer superior input line
transient response and will assist in maximizing the
highest possible power supply ripple rejection.
Ceramic, tantalum, or aluminum electrolytic capac-
itors may be selected for C
capacitor ESR requirement for C
LDO regulator output operation, ceramic capacitors
are recommended for C
capability over tantalum capacitors to withstand
input current surges from low-impedance sources
such as batteries in portable devices.
Output Capacitor
For proper load voltage regulation and operational
stability, a capacitor is required between pins V
and GND. The C
LDO regulator ground pin should be as direct as
practically possible for maximum device perform-
ance. The AAT3220 has been specifically designed
to function with very low ESR ceramic capacitors.
Although the device is intended to operate with low
ESR capacitors, it is stable over a very wide range
of capacitor ESR, thus it will also work with some
higher ESR tantalum or aluminum electrolytic
capacitors. However, for best performance, ceram-
ic capacitors are recommended.
The value of C
10µF; however, 1µF is sufficient for most operating
conditions.
3220.2006.01.1.4
IN
in most applications. A C
IN
OUT
pin as practically possible. C
OUT
typically ranges from 0.47µF to
IN
capacitor connection to the
IN
should be located as close
IN
capacitor will be needed
IN
due to their inherent
. There is no specific
IN
IN
capacitor is not
. For 150mA
150mA NanoPower™ LDO Linear Regulator
IN
val-
OUT
If large output current steps are required by an
application, then an increased value for C
should be considered. The amount of capacitance
needed can be calculated from the step size of the
change in the output load current expected and the
voltage excursion that the load can tolerate.
The total output capacitance required can be cal-
culated using the following formula:
Where:
∆I = maximum step in output current
∆V = maximum excursion in voltage that the load
can tolerate.
Note that use of this equation results in capacitor
values approximately two to four times the typical
value needed for an AAT3220 at room temperature.
The increased capacitor value is recommended if
tight output tolerances must be maintained over
extreme operating conditions and maximum opera-
tional temperature excursions. If tantalum or alu-
minum electrolytic capacitors are used, the capaci-
tor value should be increased to compensate for the
substantial ESR inherent to these capacitor types.
Capacitor Characteristics
Ceramic composition capacitors are highly recom-
mended over all other types of capacitors for use
with the AAT3220. Ceramic capacitors offer many
advantages over their tantalum and aluminum elec-
trolytic counterparts. A ceramic capacitor typically
has very low ESR, is lower cost, has a smaller PCB
footprint, and is non-polarized. Line and load tran-
sient response of the LDO regulator is improved by
using low ESR ceramic capacitors. Since ceramic
capacitors are non-polarized, they are less prone
to damage if incorrectly connected.
Equivalent Series Resistance: ESR is a very
important characteristic to consider when selecting
a capacitor. ESR is the internal series resistance
associated with a capacitor that includes lead
C
OUT
=
∆V
∆I
× 15µF
AAT3220
OUT
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