AAT1149A Datasheet, PDF (11/17 Pages) Advanced Analogic Technologies – 2.2MHz Fast Transient 400mA Step-Down Converter

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PRODUCT DATASHEET
AAT1149A
2.2MHz Fast Transient 400mA Step-Down Converter
Figure 1: AAT1149AIUV Evaluation Board
Top Side.
Figure 2: AAT1149AIUV Evaluation Board
Bottom Side.
V_IN
U1
L1
4
5
IN
LX
EN
3
AAT1149AIUV
C3
open
22
EN
1
1
FB
C2
4.7μF
3
GND
R1
0
R2
open
V_OUT
C1
4.7μF
WLCSP-5
Figure 3: AAT1149AIUV Evaluation Board Schematic.
Thermal Calculations
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 R_DS(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:
P_TOTAL =
I_O2 · (R_DS(ON)H · V_O + R_DS(ON)L · [V_IN - V_O])
V_IN
+ (t_sw · F_S · I_O + I_Q) · V_IN
I_Q is the step-down converter quiescent current. The
term t_sw is used to estimate the full load step-down con-
verter switching losses.
1149A.2008.08.1.1
www.analogictech.com
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