PRODUCT DATASHEET
AAT3183
ChargePump
TM
300mA Inductorless Step-Down Converter
Functional Block Diagram
IN
Thermal
Protection,
Current Limit
C1+
Oscillator,
Soft Start
Charge
Transfer
EN
C1-
OUT
V
REF
GND
Functional Description
The AAT3183 is a 1/2x (gain) charge pump converter
providing an output voltage which is less than the input
voltage. The step-down (buck) charge pump converter
provides a regulated output voltage for input voltages
greater than 2x the output voltage plus the required
input voltage headroom (see the Applications Information
section for more details). The output current range is
0mA (no load) to 300mA.
The AAT3183 provides an ultra-small DC-DC solution
achieving improved efficiency over LDO step-down regu-
lators. The high switching frequency allows the use of
small external capacitors. Only three ceramic capacitors
are required to achieve a complete step-down converter
solution.
Output regulation is maintained with a pulse frequency
modulation (PFM) control scheme. PFM compensates for
input voltage and output current variations by modulat-
ing the frequency of charge pump switching intervals.
Switching frequency increases with high output currents
(heavy loads) and decreases with low output currents
(light loads); with a maximum switching frequency of
2MHz. PFM control provides decreased switching losses
and increased efficiency with light loads. This extends
battery life under lightly loaded operating conditions.
The AAT3183 responds quickly to changes in line voltage
and/or output current, providing stable operation with
excellent line and load transient behavior.
No load (zero output current) quiescent current is 35µA
(typical). When disabled, the device consumes less than
1µA of current (shutdown).
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