SC2446AEVB View Datasheet(PDF) - Semtech Corporation

Part Name

Description

MFG CO.

SC2446AEVB

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

SC2446A, 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. Keep the

top MOSFET, bottom MOSFET and the input capacitors

within a small area 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

3) The frequency-setting resistor Rosc should be placed

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

ground should be minimized.

4) Solder the bias decoupling capacitor right across the

AVCC and analog ground AGND.

5) Place the Combi-sense components away from the

power circuit and close to the corresponding CS+ and

CS- pins. Use X7R type ceramic capacitor for the Combi-

sense capacitor because of their temperature stability.

6) Use an isolated local ground plane for the controller

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

 2005 Semtech Corp.

20

SC2446A

www.semtech.com

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