AAT3183 Datasheet, PDF (8/16 Pages) Advanced Analogic Technologies – 300mA Inductorless Step-Down Converter

AAT3183
300mA Inductorless Step-Down Converter
Functional Block Diagram
IN
Thermal
Protection,
Current Limit
EN
Oscillator,
Soft Start
Charge
Transfer
C1+
C1-
OUT
GND
V_REF
Functional Description
The AAT3183 is a 1/2x (gain) charge pump con-
verter providing an output voltage which is less
than the input voltage. The step-down (buck)
charge pump converter provides a regulated out-
put voltage for input voltages greater than 2x the
output voltage plus the required input voltage
headroom (see the Applications Information sec-
tion for more details). The output current range is
0mA (no load) to 300mA.
The AAT3183 provides an ultra-small DC-DC solu-
tion achieving improved efficiency over LDO step-
down regulators. 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 fre-
quency modulation (PFM) control scheme. PFM
compensates for input voltage and output current
variations by modulating 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 oper-
ating 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 con-
sumes less than 1µA of current (shutdown).
Integrated soft-start limits inrush current, maintains
monotonic turn-on characteristics and eliminates
output voltage overshoot. The device includes
short-circuit protection and a self-recovering over-
temperature (thermal) protection.
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