sc2447tstrt Semtech Corporation, sc2447tstrt Datasheet - Page 23

• Manufacturer Part Number: sc2447tstrt
• Description: Sc2447 Dual-phase, Single Or Dual Output Synchronous Step-down Controller
• Manufacturer: Semtech Corporation

SC2447
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 R
should be placed
OSC
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.
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2006 Semtech Corp.
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