AAT3242 AAT, AAT3242 Datasheet - Page 10

• Manufacturer Part Number: AAT3242
• Description: Dual CMOS LDO Linear Regulator
• Manufacturer: AAT

Applications Information
To assure the maximum possible performance is
obtained from the AAT3242, please refer to the fol-
lowing application recommendations.
Input Capacitor
A 1µF or larger capacitor is typically recommended
for C
required for basic LDO regulator operation; howev-
er, if the AAT3242 is physically located more than
three centimeters from an input power source, a
C
C
pin as practically possible. C
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
300mA LDO regulator output operation, ceramic
capacitors are recommended for C
inherent capability over tantalum capacitors to with-
stand 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 made as direct
as practically possible for maximum device per-
formance.
designed to function with very low ESR ceramic
capacitors. For best performance, ceramic capaci-
tors are recommended.
Typical output capacitor values for maximum out-
put current conditions range from 1µF to 10µF.
Applications utilizing the exceptionally low output
noise and optimum power supply ripple rejection
characteristics of the AAT3242 should use 2.2µF or
10
IN
IN
should be located as closely to the device V
capacitor will be needed for stable operation.
IN
in most applications. A C
The AAT3242 has been specifically
OUT
capacitor connection to the
IN
IN
. There is no specific
values greater than
IN
IN
capacitor is not
; however, for
IN
due to their
300mA/150mA Dual CMOS LDO Linear Regulator
OUT
IN
greater for C
without limit.
where output load is less than 10mA, the minimum
value for C
Capacitor Characteristics
Ceramic composition capacitors are highly recom-
mended over all other types of capacitors for use
with the AAT3242. 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 not prone to
incorrect connection damage.
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 resistance, internal connections, size
and area, material composition, and ambient tem-
perature. Typically, capacitor ESR is measured in
milliohms 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 generally have tight tolerance and are
very stable over temperature. Larger capacitor val-
ues are usually composed of X7R, X5R, Z5U, or
Y5V dielectric materials. These two material types
are not recommended for use with LDO regulators
since the capacitor tolerance can vary more than
±50% over the operating temperature range of the
device. A 2.2µF Y5V capacitor could be reduced to
1µF over temperature; this could cause problems
for circuit operation. X7R and X5R dielectrics are
much more desirable. The temperature tolerance
OUT
OUT
can be as low as 0.47µF.
In low output current applications
. If desired, C
OUT
may be increased
AAT3242
3242.2006.04.1.10