AAT1130 Datasheet, PDF (14/18 Pages) Advanced Analogic Technologies – 2.5MHz 500mA Step-Down DC/DC Converter

DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
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. For the condition where the
step-down converter is in dropout at 100% duty cycle,
the total device dissipation reduces to:
P_TOTAL = I_O2 · R_DS(ON)H + I_Q · V_IN
Since R_DS(ON), quiescent current, and switching losses all
vary with input voltage, the total losses should be inves-
tigated over the complete input voltage range. Given the
total losses, the maximum junction temperature can be
derived from the θ_JA for the SC70JW-10 package which
is 160°C/W.
T_J(MAX) = P_TOTAL · Θ_JA + T_AMB
Layout
The suggested PCB layout for the AAT1130 is shown in
Figures 4 and 5. The following guidelines should be used
to help ensure a proper layout:
1. The input capacitor (C1) should connect as closely as
possible to the VCC/VP and GND pins.
2. C1 and L1 should be connected as closely as possi-
ble. The connection of L1 to the LX pin should be as
short as possible.
3. The feedback trace or FB pin for adjustable output
voltage 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 FB pin for adjustable output voltage to minimize
the length of the high impedance feedback trace.
4. The resistance of the trace from the load return to
the GND pins should be kept to a minimum. This will
help to minimize any error in DC regulation due to
differences in the potential of the internal signal
ground and the power ground.
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201977B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 15, 2013