PRODUCT DATASHEET
AAT1149A
TM
SwitchReg
2.2MHz FastTransient 400mA Step-Down Converter
Figure 1: AAT1149AIUV Evaluation Board
Top Side.
Figure 2: AAT1149AIUV Evaluation Board
Bottom Side.
VIN
U1
L1
5
4
IN
LX
VOUT
C3
EN
AAT1149AIUV
R1
0
open
1
3
2
2
EN
FB
C1
4.7μF
1
R2
open
C2
4.7μF
3
GND
WLCSP-5
Figure 3: AAT1149AIUV Evaluation Board Schematic.
Thermal Calculations
IO2 · (RDS(ON)H · VO + RDS(ON)L · [VIN - VO])
PTOTAL
=
There are three types of losses associated with the
AAT1149A step-down converter: switching losses, con-
duction losses, and quiescent current losses. Conduction
losses are associated with the RDS(ON) characteristics of the
power output switching devices. Switching losses are
dominated by the gate charge of the power output switch-
ing devices. At full load, assuming continuous conduction
mode (CCM), a simplified form of the losses is given by:
VIN
+ (tsw · FS · IO + IQ) · VIN
IQ is the step-down converter quiescent current. The
term tsw is used to estimate the full load step-down con-
verter switching losses.
w w w . a n a l o g i c t e c h . c o m
1149A.2008.08.1.1
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ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
