AAT1142 Datasheet, PDF (10/22 Pages) Advanced Analogic Technologies – 800mA Voltage-Scaling Step-Down Converter

AAT1142
800mA Voltage-Scaling Step-Down Converter
Functional Block Diagram
FB
VIN PVIN
MODE/SYNC
Voltage
Reference
EN/SET
SDA
SCL
Err.
Amp.
Control
Logic
DH
Logic
DL
AGND
LX
PGND
Functional Description
The AAT1142 is a high performance, 800mA step-
down converter with an input voltage range from
2.7V to 5.5V. The AAT1142 uses Dynamic Voltage
Management, which allows the system host to
quickly set the output voltage through the integrat-
ed I²C or S²Cwire interface. Through this interface,
the host can change the output voltage to track
processor idle and active states, greatly extending
battery life without degrading system performance.
I²C provides an industry-standard, dual-line inter-
face, while S²Cwire provides a single-line, high-
speed serial interface.
The 2.2MHz switching frequency allows the use of
small external components. Only three external
components are needed to program the output
10
from 0.6V to 2.0V. Typically, one 4.7µF capacitor,
one 10µF capacitor, and one 2.2µH inductor are
required.
The integrated low-loss MOSFET switches provide
up to 93% efficiency. PFM operation maintains
high efficiency under light load conditions (typically
<50mA). Pulling the MODE/SYNC pin high allows
optional PWM Only low noise mode. This main-
tains 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 synchronization can
be maintained between 1MHz and 3MHz.
At low input voltages, the converter dynamically
adjusts the operating frequency prior to dropout to
maintain the required duty cycle and provide accu-
1142.2006.07.1.0