APS1056
Fast Transient 600mA Step-Down Converter
Functional Block Diagram
OUT
VIN
See note
Err
Am. p
Voltage
Reference
EN
INPUT
DH
Logic
DL
LX
GND
Note: For adjustable version, the internal feedback divider is omitted and the OUT pin is tied directly
to the internal error amplifier.
Functional Description
The APS1056 is a high performance 600mA
1.4MHz monolithic step-down converter. It has
been designed with the goal of minimizing external
component size and optimizing 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 4.7µH inductor and a 4.7µF
ceramic capacitor are recommended (see table of
values).
The fixed output version requires only three external
power components (CIN, COUT, and L). The
adjustable version can be programmed with external
feedback to any voltage, ranging from 0.6V to the
input voltage. An additional feed-forward capacitor
can also be added to the external feedback to pro-
vide improved transient response (see Figure 1).
At dropout, the converter duty cycle increases to
100% and the output voltage tracks the input volt-
age minus the RDSON drop of the P-channel high-
side MOSFET.
The input voltage range is 2.7V to 5.5V. The con-
verter efficiency has been optimized for all load
conditions, ranging from no load to 600mA.
The internal error amplifier and compensation pro-
vides excellent transient response, load, and line
regulation. Soft start eliminates any output voltage
overshoot when the enable or the input voltage is
applied.
APS1056.2007.04.0.9 (PRELIMINARY INFORMATION)
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