Dual 400mA High Frequency Buck Converter
Functional Block Diagram
FB1
VIN1
AAT2512
Err.
Amp.
Comp.
DH
Logic
Voltage
Reference
Control
Logic
LX1
DL
EN1
GND1
SGND1
FB2
See
Note
VIN2
Err.
Amp.
Comp.
DH
Logic
Voltage
Reference
LX2
DL
EN2
See
Note
Control
Logic
GND2
SGND2
Note: Internal resistor divider included for
≥1.2V
versions. For low voltage versions, the feedback pin is tied directly to the error amplifier input.
Functional Description
The AAT2512 is a high performance power man-
agement IC comprised of two buck converters.
Each channel has independent input voltages and
enable/disable pins. Designed to operate at 1.4MHz
of switching frequency, the converters require only
three external components (C
IN
, C
OUT
, and L
X
), min-
imizing cost and size of external components.
Both converters are designed to operate with an input
voltage range of 2.7V to 5.5V. Typical values of the
output filter are 4.7µH and 4.7µF ceramic capacitor.
The output voltage operates to as low as 0.6V and is
offered as both fixed and adjustable. Power devices
are sized for 400mA current capability while main-
taining over 90% efficiency at full load. Light load effi-
ciency is maintained at greater than 80% down to
500µA of load current. Both channels have excellent
transient response, load, and line regulation.
Transient response time is typically less than 20µs.
2512.2006.06.1.4
The AAT2512 also features soft-start control to limit
inrush current. Soft start increases the inductor
current limit point in discrete steps when power is
applied to the input or when the enable pins are
pulled high. It limits the current surge seen at the
input and eliminates output voltage overshoot. The
enable input, when pulled low, forces the converter
into a low power, non-switching state consuming
less than 1µA of current.
For overload conditions, the peak input current is
limited. As load impedance decreases and the out-
put voltage falls closer to zero, more power is dis-
sipated internally, raising the device temperature.
Thermal protection completely disables switching
when internal dissipation becomes excessive, pro-
tecting the device from damage. The junction over-
temperature threshold is 140°C with 15°C of hys-
teresis. The under-voltage lockout guarantees suf-
ficient V
IN
bias and proper operation of all internal
circuits prior to activation.
9
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
