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201999B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013

AAT1171

600mA Voltage-Scaling Step-Down Converter

for RF Power Amplifiers with Bypass Switch

DATA SHEET

WLCSP Package Light Sensitivity

The electrical performance of the WLCSP package can be

adversely affected by exposing the device to certain light

sources such as direct sunlight or a halogen lamp whose

wavelengths are red and infra-reds. However, fluores-

cent lighting has very little effect on the electrical per-

formance of the WLCSP package.

Layout

The suggested PCB layout for the AAT1171 is shown in

Figures 4 and 5. The following guidelines should be used

to ensure a proper layout.

1. The input capacitor (C1) should connect as closely

as possible to VIN (Pin 10) and PGND (Pin 11).

2. C2 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 PCB trace connected to VOUT (Pins 2 and 3) is

tied to the bypass path, as well as the feedback path

for the control loop. In bypass mode, the full load

current is delivered directly from the battery input;

therefore, this trace should be sufficient to handle

current up to the bypass current limit level.

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

PGND (Pin 11) should be kept to a minimum. This

minimizes any error in DC regulation due to differ-

ences in the potential of the internal signal ground

and the power ground.

5. For good thermal coupling, PCB vias are required

from the pad for the TDFN exposed paddle to the

ground plane. The via diameter should be 0.3mm to

0.33mm and positioned on a 1.2mm grid.

Figure 4: AAT1171 Evaluation Board

Figure 5: AAT1171 Evaluation Board

Top Side Layout.

Bottom Side Layout.