AAT2511 Datasheet, PDF (9/20 Pages) Advanced Analogic Technologies – Dual 600mA, 1MHz Step-Down DC/DC Converter

AAT2511
Dual 600mA, 1MHz Step-Down DC/DC Converter
VIN
C3
10µF
1.8V
C4
100pF
L1
4.7µH
C1
10µF
R1
118k
R2
59.0k
U1
AAT2511
12
VIN1
9
VIN2
1
EN1
4
EN2
11
LX1
8
LX2
2
FB1
5
FB2
3
6
SGND1 SGND2
10
GND1
7
GND2
C8
0.1µF
2.5V
L2
10µH _C5
100pF
R4
59.0k
R3
187k
C2
10µF
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.
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
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.
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
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