AAT1112 Datasheet, PDF (10/19 Pages) Advanced Analogic Technologies – 1.5A, 1.4MHz Step-Down Converter

Functional Block Diagram
FB
DATA SHEET
AAT1112
1.5A, 1.4MHz Step-Down Converter
VIN
VP
Err.
Amp
V_REF
EN
MODE/SYNC
Input
GND
DH
Logic
DL
LX
PGND
Functional Description
The AAT1112 is a high performance 1.5A monolithic
step-down converter operating at 1.4MHz switching fre-
quency. It minimizes external component size and opti-
mizes efficiency over the complete load range. Apart
from the small bypass input capacitor, only a small L-C
filter is required at the output. Typically, a 3.3μH induc-
tor 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 P-channel high-side MOSFET (plus
the DC drop of the external inductor). The device inte-
grates 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 95% efficiency at full load. PFM operation
maintains high efficiency under light load conditions
(typically <150mA). The MODE/ SYNC pin allows option-
al “PWM only” mode. This maintains constant frequency
and low output ripple across all load conditions.
Alternatively, the IC can be synchronized to an external
clock via the MODE/ SYNC input. External synchroniza-
tion is maintained between 0.6MHz and 3.0MHz.
In battery-powered applications, as V_IN decreases, the
converter dynamically adjusts the operating frequency
prior to dropout to maintain the required duty cycle and
provide accurate output regulation. Output regulation is
maintained until the dropout voltage, or minimum input
voltage, is reached. At 1.5A output load, dropout volt-
age headroom is approximately 200mV.
The AAT1112 typically achieves better than ±0.5% out-
put regulation across the input voltage and output load
range. A current limit of 2.0A (typical) protects the IC
and system components from short-circuit damage.
Typical no load quiescent current is 42μA.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
10
201972B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 15, 2013