SC2446A Semtech Corporation, SC2446A Datasheet - Page 20

• Manufacturer Part Number: SC2446A
• Description: Dual-Phase Single or Two Output Synchronous Step-Down Controller
• Manufacturer: Semtech Corporation

SC2446A
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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.
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