AAT1143 데이터 시트보기 (PDF) - Skyworks Solutions

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AAT1143

1MHz 400mA Step-Down Converter

Skyworks Solutions 

For the condition where the step-down converter is in

dropout at 100% duty cycle, the total device dissipation

reduces to:

PTOTAL = IO2 · RDS(ON)H + IQ · VIN

Since RDS(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 tempera-

ture can be derived from the JA for the SC70JW-8 pack-

age which is 160°C/W.

TJ(MAX) = PTOTAL · ΘJA + TAMB

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.

DATA SHEET

AAT1143

1MHz 400mA Step-Down Converter

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

possible to VIN (Pin 3) and PGND (Pins 6 through 8).

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 OUT pin (Pin 2) should be

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.

4. The resistance of the trace from the load return to

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.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

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201983B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 25, 2013

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