PRODUCT DATASHEET
AAT2113A
SwitchReg
TM
3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
Functional Block Diagram
FB
AAT2113A-1.2V Only
VCC
VP
Err
Amp
DH
V
REF
=
0.6V
Comp
Logic
DL
LX
EN
Input
PGND
AGND
Functional Description
The AAT2113A SwitchReg is a 1.5A step-down converter
with a typical input voltage of 3.3V and a fixed output
voltage of 1.2V. The 3MHz switching frequency enables
the use of small external components. The ultra-small,
2mm x 2mm footprint and high efficiency make the
AAT2113A an ideal choice for portable applications.
Typically, a 0.47μH inductor and a 10μF ceramic capaci-
tor are recommended for a 1.2V output (see Figure 2 for
recommended values).
At dropout, the converter duty cycle increases to 100%
and the output voltage tracks the input voltage minus
the R
DS(ON)
drop of the P-channel high-side MOSFET (plus
the DC drop of the external inductor). The device inte-
grates extremely low R
DS(ON)
MOSFETs to achieve low
dropout voltage during 100% duty cycle operation.
The integrated low-loss MOSFET switches can provide
excellent efficiency at heavy loads. Light load operation
maintains high efficiency, low ripple and low spectral
noise even at lower currents (typically <150mA). PWM
mode operation maintains constant frequency and low
output ripple at output loads greater than 200mA.
In battery-powered applications, as V
IN
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 1.5A output load, dropout voltage
headroom is approximately 200mV.
The AAT2113A typically achieves better than ±0.5%
output regulation across the input voltage and output
load range. A current limit of 3.0A (typical) protects the
IC and system components from short-circuit damage.
Typical no load quiescent current is 55μA.
Thermal protection completely disables switching when
the maximum junction temperature is detected. The
junction over-temperature threshold is 140°C with 15°C
of hysteresis. Once an over-temperature or over-current
fault condition is removed, the output voltage automati-
cally recovers.
Peak current mode control and optimized internal com-
pensation provide high loop bandwidth and excellent
response to input voltage and fast load transient events.
Soft start eliminates output voltage overshoot when the
enable or the input voltage is applied. Under-voltage
lockout prevents spurious start-up events.
2113A.2009.06.1.1
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