SC2447 View Datasheet(PDF) - Semtech Corporation

Part Name

Description

Manufacturer

SC2447

Dual-Phase, Single or Dual Output Synchronous Step-Down Controller

Semtech Corporation 

POWER MANAGEMENT

Application Information (Cont.)

PC Board Layout Issues

Circuit board layout is very important for the proper

operation of high frequency switching power converters.

A power ground plane is required to reduce ground

bounces. The followings are suggested for proper layout.

Power Stage

1) Separate the power ground from the signal ground. In

the SC2447, the power ground PGND should be tied to

the source terminal of lower MOSFETs. The signal ground

AGND should be tied to the negative terminal of the

output capacitor.

2) Minimize the size of high pulse current loop. Place

the top MOSFET, bottom MOSFET and the input

capacitors close to each other with short and wide traces.

In addition to the aluminum energy storage capacitors,

add multi-layer ceramic (MLC) capacitors from the input

to the power ground to improve high frequency bypass.

Control Section

1) The frequency-setting resistor ROSC should be placed

close to Pin 3. Trace length from this resistor to the

analog ground should be minimized.

2) Solder the bias decoupling capacitor right across the

AVCC and analog ground AGND.

3) Place the current sensing network away from the

power circuit and close to the corresponding CS+ and

CS- pins. Use X7R ceramic capacitor for the sensing

capacitor because of its temperature stability.

4) Use an isolated local ground plane for the controller

and tie it to the negative side of output capacitor bank.

© 2006 Semtech Corp.

23

SC2447

www.semtech.com

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