AW3643CSR datasheet(33/39 Pages) AWINIC

33 / 39 page

AW3643

Jan 2018 V1.4

www.awinic.com.cn

PCB LAYOUT

LAYOUT GUIDELINES

The high switching frequency and large switching currents of the AW3643 make the choice of layout important.

The following steps should be used as a reference to ensure the device is stable and maintains proper LED

current regulation across its intended operating voltage and current range.

Place CIN on the top layer (same layer as the AW3643) and as close to the device as possible. The input

capacitor conducts the driver currents during the low-side MOSFET turn-on and turn-off and can detect

current spikes over 1 A in amplitude. Connecting the input capacitor through short, wide traces to both the

IN and GND pins reduces the inductive voltage spikes that occur during switching which can corrupt the

VIN line.

Place COUT on the top layer (same layer as the AW3643) and as close as possible to the OUT and GND

pin. The returns for both CIN and COUT should come together at one point, as close to the GND pin as

possible. Connecting COUT through short, wide traces reduce the series inductance on the OUT and GND

pins that can corrupt the VOUT and GND lines and cause excessive noise in the device and surrounding

circuitry.

Connect the inductor on the top layer close to the SW pin. There should be a low-impedance connection

from the inductor to SW due to the large DC inductor current, and at the same time the area occupied by

the SW node should be small so as to reduce the capacitive coupling of the high dV/dT present at SW

that can couple into nearby traces.

Avoid routing logic traces near the SW node so as to avoid any capacitive coupling from SW onto any

high-impedance logic lines such as TORCH/TEMP, STROBE, HWEN, SDA, and SCL. A good approach

is to insert an inner layer GND plane underneath the SW node and between any nearby routed traces.

This creates a shield from the electric field generated at SW.

Terminate the Flash LED cathodes directly to the GND pin of the AW3643. If possible, route the LED

returns with a dedicated path so as to keep the high amplitude LED currents out of the GND plane. For

Flash LEDs that are routed relatively far away from the AW3643, a good approach is to sandwich the

forward and return current paths over the top of each other on two layers. This helps reduce the

inductance of the LED current paths.

AW3643CSR Datasheet(PDF) 33 Page - Shanghai awinic technology co.,ltd