PRODUCT DATASHEET
AAT2153
TM
SwitchReg
2.5A Low Noise Step-Down Converter
Functional Block Diagram
VCC
VP
0.6V REF
CMP
DH
LX
DL
OP. AMP
FB
LOGIC
1MΩ
Temp.
Sensing
OSC
SGND
EN
PGND
The integrated low-loss MOSFET switches can provide
greater than 95% efficiency at full load. Light load opera-
tion maintains high efficiency, low ripple and low spectral
noise even at lower currents (typically <150mA).
Functional Description
The AAT2153 is a high performance 2.5A monolithic
step-down converter operating at a 1.4MHz switching
frequency. It minimizes external component size, opti-
mizes efficiency over the complete load range, and pro-
duces reduced ripple and spectral noise. Apart from the
small bypass input capacitor, only a small L-C filter is
required at the output. Typically, a 3.3μH inductor and a
22μF ceramic capacitor are recommended for a 3.3V
output (see table of recommended values).
In battery-powered applications, as VIN decreases, the
converter dynamically adjusts the operating frequency
prior to dropout to maintain the required duty cycle and
provide accurate output regulation. Output regulation is
maintained until the dropout voltage, or minimum input
voltage, is reached. At 2.5A output load, dropout voltage
headroom is approximately 200mV.
At dropout, the converter duty cycle increases to 100%
and the output voltage tracks the input voltage minus
the RDS(ON) drop of the P-channel high-side MOSFET (plus
the DC drop of the external inductor). The device inte-
grates extremely low RDS(ON) MOSFETs to achieve low
dropout voltage during 100% duty cycle operation. This
is advantageous in applications requiring high output
voltages (typically > 2.5V) at low input voltages.
The AAT2153 typically achieves better than ±0.5% out-
put regulation across the input voltage and output load
range. A current limit of 3.5A (typical) protects the IC
and system components from short-circuit damage.
Typical no load quiescent current is 42μA.
Thermal protection completely disables switching when
the maximum junction temperature is detected. The
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2153.2008.09.1.0
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