AAT1130 Datasheet, PDF (10/18 Pages) Advanced Analogic Technologies – 2.5MHz 500mA Step-Down DC/DC Converter

Functional Block Diagram
DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
VP
VCC
EN
Control and
FET Driver
Logic Circuitry
Current
Limit
Comparator
Error
Comparator
Shoot
Through
LX
Protection
V_ILIM
Current
Sense
Amplifier
GND
VOUT
FB
Soft-Start
+ _VREF
-
Functional Description
The AAT1130 is a high performance 400mA 2.5MHz
(maximum switching frequency during steady-state
operation) monolithic step-down converter. It minimizes
external component size, enabling the use of a tiny 0603
inductor that is only 1mm tall, and optimizes 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 1μH inductor and a 4.7μF
ceramic capacitor are recommended for <1.2V output
voltage applications (see table of values).
Only three external power components (C_IN, C_OUT, and L)
are required. Output voltage is programmed with exter-
nal feedback resistors, ranging from 0.6V to 1.8V. An
additional feed-forward capacitor can also be added to
the external feedback to provide improved transient
response (see Figure 1).
GND
The input voltage range is 2.7V to 5.5V. The converter
efficiency has been optimized for all load conditions,
ranging from no load to 400mA.
The internal error comparator and incorporated compen-
sation provide excellent transient response, load, and line
regulation. Soft-start eliminates any output voltage over-
shoot when the enable or the input voltage is applied.
Control Loop
The AAT1130 uses a current-mode control scheme that
allows it to operate at very high switching frequencies.
The current-mode control scheme operates with a pre-
dicted on-time for a given output to input voltage ratio.
The on-time varies inversely proportional to the input
voltage and proportional to the output voltage giving the
regulator a fixed switching frequency when in steady-
state. This allows the use of very small external inductor
and capacitor. The small size coupled with the low quies-
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201977B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 15, 2013