AAT1143IJS-0.6-T1 AnalogicTech, AAT1143IJS-0.6-T1 Datasheet - Page 14

• Manufacturer Part Number: AAT1143IJS-0.6-T1
• Description: 1MHz 400mA Step-Down Converter
• Manufacturer: AnalogicTech

For the condition where the step-down converter is in
dropout at 100% duty cycle, the total device dissipation
reduces to:
Since R
vary with input voltage, the total losses should be inves-
tigated over the complete input voltage range.
Given the total losses, the maximum junction tempera-
ture can be derived from the θ
age which is 160°C/W.
Dissipation due to the RMS current in the ceramic output
capacitor ESR is typically minimal, resulting in less than
a few degrees rise in hot-spot temperature.
14
SwitchReg
DS(ON)
, quiescent current, and switching losses all
P
TM
T
TOTAL
J(MAX)
= I
= P
O
2
TOTAL
· R
DS(ON)H
· Θ
JA
for the SC70JW-8 pack-
JA
+ I
+ T
Q
AMB
· V
IN
w w w . a n a l o g i c t e c h . c o m
Layout
The suggested PCB layout for the AAT1143 is shown in
Figures 2, 3, and 4. The following guidelines should be
used to help ensure a proper layout.
1. The input capacitor (C2) should connect as closely as
2. C1 and L1 should be connected as closely as possi-
3. The feedback trace or OUT pin (Pin 2) should be
4. The resistance of the trace from the load return to
possible to VIN (Pin 3) and PGND (Pins 6 through
8).
ble. The connection of L1 to the LX pin should be as
short as possible.
separate from any power trace and connect as close-
ly as possible to the load point. Sensing along a
high-current load trace will degrade DC load regula-
tion. 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 imped-
ance feedback trace.
PGND (Pins 6 through 8) should be kept to a mini-
mum. 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.
1MHz 400mA Step-Down Converter
PRODUCT DATASHEET
AAT1143
1143.2009.02.1.11