AAT3258_06 Datasheet, PDF (11/16 Pages) Advanced Analogic Technologies – 300mA LDO Linear Regulator with μP Reset

AAT3258
300mA LDO Linear Regulator with µP Reset
The microprocessor reset section monitors the supply
voltage to a microprocessor and asserts a reset sig-
nal whenever the V_DET voltage falls below a factory-
programmed threshold. This threshold is accurate
within +/-1.5% at 25°C. The reset signal remains
asserted for a minimum of 150ms after V_DET has risen
above the threshold, as shown in Figure 1.
To assure the maximum possible performance is
obtained from the AAT3258, please refer to the fol-
lowing application recommendations.
V_DET
V_TH
V_TH
V_TH
RESET
t_RDY
t_RDY
Figure 1: Reset Signal Assertion.
LDO Regulator Applications
Input Capacitor
Typically, a 1µF or larger capacitor is recommend-
ed for C_IN in most applications. A C_IN capacitor is
not required for basic LDO regulator operation.
However, if the AAT3258 is physically located more
than three centimeters from an input power source,
a C_IN capacitor will be needed for stable operation.
C_IN should be located as closely to the device V_IN
pin as practically possible. C_IN values 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 capaci-
tors may be selected for C_IN. There is no specific
capacitor ESR requirement for C_IN. However, for
300mA LDO regulator output operation, ceramic
capacitors are recommended for C_IN due to their
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_OUT
and GND. The C_OUT capacitor connection to
the LDO regulator ground pin should be made as
direct as practically possible for maximum device
performance.
The AAT3258 has been specifically designed to func-
tion with very low ESR ceramic capacitors. For best
performance, ceramic capacitors are recommended.
Typical output capacitor values for maximum output
current conditions range from 1µF to 10µF.
Applications utilizing the exceptionally low output
noise and optimum power supply ripple rejection
characteristics of the AAT3258 should use 2.2µF or
greater for C_OUT. If desired, C_OUT may be increased
without limit.
In low output current applications where output
load is less than 10mA, the minimum value for
C_OUT can be as low as 0.47µF.
3258.2006.03.1.6
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