Dual Channel 600mA Step-Down Converter
Functional Block Diagram
Regulator 1
Slope Comp
AAT2514
+
I
SENSE
AMP
3
IN
-
600mV
+
EA
-
+
I
COMP
-
S _Q
R
Q
PWM
Logic
FB1
1
Non-
Overlap
Control
4
LX1
650mV
+
OVDET
-
+
I
ZERO
COMP
-
8
EN1
EN2
2
9
Bandgap
Reference
Overtemperature
and Shortcircuit
Protection
POR
Counter
POR
OSC
FB2 10
REGULATOR 2 (Same as Regulator 1)
7
LX2
Functional Description
The AAT2514 is a dual high performance 600mA,
1.5MHz fixed frequency monolithic switch-mode
step-down converter which uses current mode
architecture with an adaptive slope compensation
scheme. It minimizes external component size and
optimizes efficiency over the complete load range.
The adaptive slope compensation allows the device
to remain stable over a wider range of inductor val-
ues so that smaller values (1µH to 4.7µH) with asso-
ciated lower DCR can be used to achieve higher
efficiency.
Apart from the small bypass input capacitor, only a
small L-C filter is required at each output. The
adjustable outputs can be programmed with exter-
nal feedback to any voltage, ranging from very low
output voltages to the input voltage and by using an
internal reference of 0.6V. The part uses internal
MOSFETs for each channel to achieve high efficien-
cy. At dropout, the converter duty cycle increases to
100% and the output voltages track the input voltage
minus the low R
DS(ON)
drop of the P-channel high-
side MOSFETs. The converter efficiency has been
optimized for all load conditions, ranging from no
load to 600mA at V
IN
= 3V with an input voltage
range from 2.5V to 5.5V. The internal error amplifier
and compensation provides excellent transient
response, load, and line regulation. Internal soft start
eliminates any output voltage overshoot when the
enable or the input voltage is applied.
2514.2007.06.1.0
7
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
