AAT2511
Dual 600mA, 1MHz Step-Down DC/DC Converter
V
IN
C3
10µF
12
U1
AAT2511
VIN1
EN1
LX1
FB1
SGND1
GND1
VIN2
EN2
LX2
FB2
SGND2
GND2
9
1
4
8
5
6
7
C8
0.1µF
2.5V
L2
10µH
C5
100pF
R3
187k
C2
10µF
1.8V
L1
C4
100pF
R1
118k
4.7µH
11
2
3
10
C1
10µF
R2
59.0k
R4
59.0k
Figure 1: AAT2511 Adjustable Output with
Enhanced Transient Response.
Soft Start
The AAT2511 soft-start control prevents output volt-
age overshoot and limits inrush current when either
the input power or the enable input is applied.
When pulled low, the enable input forces the con-
verter into a low-power, non-switching state with a
bias current of less than 1µA.
MOSFET is turned on continuously for 100% duty
cycle. At 100% duty cycle, the output voltage tracks
the input voltage minus the I*R drop of the high
side P-channel MOSFET R
DS(ON)
.
Low Supply
The under-voltage lockout (UVLO) feature guaran-
tees sufficient V
IN
bias and proper operation of all
internal circuitry prior to activation.
Low Dropout Operation
For conditions where the input voltage drops to the
output voltage level, the converter duty cycle
increases to 100%. As 100% duty cycle is
approached, the minimum off-time initially forces
the high side on-time to exceed the 1MHz clock
cycle and reduce the effective switching frequency.
Once the input drops below the level where the out-
put can be regulated, the high side P-channel
Fault Protection
For overload conditions, the peak inductor current is
limited. Thermal protection disables switching when
the internal dissipation or ambient temperature
becomes excessive. The junction over-temperature
threshold is 140°C with 15°C of hysteresis.
2511.2006.02.1.2
9
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
