AN1025 データシートの表示（PDF） - Microchip Technology
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AN1025 Datasheet PDF : 8 Pages
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VIN
CIN
Q1
L1
Q2
Switch Control
and Oscillator
AN1025
COUT
RL
FIGURE 5:
Synchronous Buck Converter.
SUMMARY
This application note has provided the system designer
with an overview of different options used to produce a
regulated 3.0V from a 5.0V system rail. Key highlights
of each option were discussed, but often it is important
to compare the advantages of one particular solution
over another.
As a system designer, an LDO might be chosen
because of its lower cost, smaller size, ease-of-use, or
low system noise generation. However, under certain
conditions, the extra power that needs to be dissipated
in an LDO might over shadow these advantages.
The biggest advantage of using charge pumps is no
inductor is required. Regulation is accomplished by
transferring charge from the fly capacitor to the output.
The low output current capability of a charge pump
might prohibit a charge pump from being chosen for
heavy load applications.
A buck switch mode converter offers the advantages of
being the highest efficiency when VIN to much greater
than VOUT and capable of suppling higher output
current levels. With the integration of the MOSFETs
and control circuitry into a buck regulator IC, designing
a buck converter is relatively simple to accomplish.
However, an inductor and output capacitor are required
causing the parts count to be slightly higher than other
options.
Deciding which option to use when converting an exist-
ing 5.0V system rail to a regulated 3.0V ultimately lays
with the specific application requirements.
REFERENCES
MCP1601 Data Sheet, “500 mA Synchronous BUCK
Regulator”, DS21762, Microchip Technology Inc., 2003
MCP1612 Data Sheet, “Single 1A, 1.4 MHz Synchro-
nous Buck Regulator”, DS21921, Microchip
Technology Inc., 2005
TC1303A/TC1303B — TC1303C/TC1304 Data Sheet,
“500 mA Synchronous Buck Regulator, + 300 mA LDO
with Power-Good Output”, DS21949, Microchip
Technology Inc., 2005
MCP1252/53 Data Sheet, “Low Noise, Positive-Regu-
lated Charge Pump”, DS21752, Microchip Technology
Inc., 2002
MCP1700 Data Sheet, “Low Quiescent Current LDO”,
DS21826, Microchip Technology Inc., 2003
TC1017 Data Sheet, “150 mA, Tiny CMOS LDO With
Shutdown”, DS21813, Microchip Technology Inc., 2005
AN793 Application Note, “Power Management in Por-
table Applications: Understanding the Buck Switch
Mode Power Converter”, DS00793, Microchip Technol-
ogy Inc., 2001
AN968 Application Note, “Simple Synchronous Buck
Converter Design - MCP1612”, DS00968, Microchip
Technology Inc., 2005
AN960 Application Note, “New Components and
Design Methods Bring Intelligence to Battery Charger
Applications”, DS00960, Microchip Technology Inc.,
2004
MCP1601 Buck Regulator Evaluation Board,
MCP1601EV, Microchip Technology Inc., 2004
MCP1612 Synchronous Buck Regulator Evaluation
Board, MCP1612EV, Microchip Technology Inc., 2005
TC1303B Buck Regulator LDO Demo Board,
TC1303BDM-DDBK1, Microchip Technology Inc., 2005
TC1016/17 LDO Linear Regulator Evaluation Board,
TC1016/17EV, Microchip Technology Inc.,2005
© 2006 Microchip Technology Inc.
DS01025A-page 5
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