AAT1123 Datasheet, PDF (14/20 Pages) Advanced Analogic Technologies – 1MHz Step-Down Converter

Since R_DS(ON), quiescent current, and switching
losses all vary with input voltage, the total losses
should be investigated over the complete input
voltage range.
Given the total losses, the maximum junction tem-
perature can be derived from the θ_JA for the
SC70JW-8 package which is 160°C/W.
T_J(MAX) = P_TOTAL · Θ_JA + T_AMB
Layout
The suggested PCB layout for the AAT1123 is
shown in Figures 2, 3, and 4. The following guide-
lines should be used to help ensure a proper layout.
AAT1123
1MHz Step-Down Converter
1. The input capacitor (C2) should connect as
closely as possible to V_IN (Pin 3) and PGND
(Pins 6-8).
2. C1 and L1 should be connected as closely as
possible. The connection of L1 to the LX pin
should be as short as possible.
3. The feedback trace or OUT pin (Pin 2) should
be separate from any power trace and connect
as closely as possible to the load point. Sensing
along a high-current load trace will degrade DC
load regulation. If external feedback resistors
are used, they should be placed as closely as
possible to the OUT pin (Pin 2) to minimize the
length of the high impedance feedback trace.
4. The resistance of the trace from the load return to
PGND (Pins 6-8) should be kept to a minimum.
This will help to minimize any error in DC regula-
tion due to differences in the potential of the inter-
nal signal ground and the power ground.
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1123.2006.05.1.5