AAT2522 Datasheet, PDF (10/19 Pages) Skyworks Solutions Inc. – Dual High-Current, Low-Noise, Step-Down Regulator

Functional Block Diagram
DATA SHEET
AAT2522
Dual High-Current, Low-Noise, Step-Down Regulator
IN1
VCC1
Slope
Comp
FB1
AGND1
0.6V
REF
EN1
INP
Control
Osc
Logic
TSHDN
LX1
PGND1
VCC2
Slope
Comp
FB2
AGND2
0.6V
REF
EN2
INP
Control
Osc
Logic
TSHDN
IN2
LX2
PGND2
Functional Description
The AAT2522 dual step-down regulators provide high-
performance operation with a 1.4MHz switching frequen-
cy. The AAT2522 regulators are completely independent,
including separate power supply inputs and enable sig-
nals. The highly integrated controller minimizes the
external component requirements, optimizes efficiency
over the complete load range, and produces reduced
ripple and spectral noise. Apart from the small bypass
input capacitor, only a small LC filter is required at the
output. Typically, a 3.3μH inductor and a 22μF ceramic
capacitor are recommended for a 3.3V output (see table
of recommended values).
At dropout, the converter duty cycle increases to 100%
and the output voltage tracks the input voltage minus the
R_DS(ON) drop of the high-side P-channel MOSFET (plus the
DC drop of the external inductor and PCB layout). The
device integrates extremely low R_DS(ON) MOSFETs to achieve
low dropout voltage during 100% duty cycle operation.
This is advantageous in applications requiring high output
voltages (typically > 2.5V) at low input voltages.
The integrated low-loss MOSFET switches can provide
greater than 85% efficiency at full load (5V Input to 3.3V
Output). Light-load, low-noise operation maintains high
efficiency, low ripple and low spectral noise with low cur-
rent conditions (typically < 150mA).
In battery-powered applications, as V_IN decreases, the
converter dynamically adjusts the operating frequency
prior to dropout to maintain the required high duty-cycle
and maintain accurate output regulation. The regulators
will maintain output regulation until either the dropout
voltage limit is exceeded, or the input under-voltage
threshold is reached.
The AAT2522 typically achieves better than ±0.5% out-
put regulation across the input voltage and output load
range. A current limit of 4.0A (typical) protects the IC
and system components from short-circuit damage.
Typical no load quiescent current is 90μA.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
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202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012