LM3743 datasheet(22/23 Pages) NSC

Part #	LM3743

Description	N-Channel FET Synchronous Buck Controller for Low Output Voltages

PDF	23 Pages

Scroll/Zoom	100%

Manufacturer	NSC [National Semiconductor (TI)]

Direct Link	http://www.national.com

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22 / 23 page

Application Information (Continued)

power components must be kept close together. The longer

the paths that connect them, the more they act as antennas,

radiating unwanted EMI.

Minimize the Switch Node Copper

The plane that connects the power FETs and output inductor

together radiates more EMI as it gets larger. Use just enough

copper to give low impedance to the switching currents.

Kelvin Traces For Sense Lines

The drain and the source of the high-side FET should be

connected as close as possible to the V

CC filter resistor (R6)

and the SW pin and each pin should connect with a separate

trace. The feedback trace should connect the positive node

of the output capacitor and connect to the top feedback

resistor (R2). Keep this trace away from the switch node and

from the output inductor. If driving the COMP pin low with a

signal BJT or MOSFET make sure to keep the signal tran-

sistor as close as possible to the pin and keep the trace

away from EMI radiating nodes and components.

LM3743 Datasheet(PDF) 22 Page - National Semiconductor (TI)