Information

14
Portable Power Conversion Design Guide
DC/DC Conversion
Step-Up (Boost) Switch Mode Power Converters
Performance Tradeoffs – Matching the Boost Converter to the Load Requirements
In many cases, light or no load conditions have very different requirements than high load conditions. This tradeoff can be
readily observed by comparing the MCP1640 and MCP16251. The MCP1640 offers higher current capability, handing peak
loads up to 350 mA compared to only 225 mA for MCP16251. However, the MCP16251 reduces the input quiescent
current drawn from the battery even further than the MCP1640, and the MCP16251 PFM mode offers higher efficiency at
light load conditions. An 80% quiescent current reduction extends battery run time for applications that operate for long
periods of time in sleep mode. When powering a 100 µA load, the MCP16251 is nearly 12% more efficient than the
MCP1640. Applications that draw high currents may need the additional power capability of the MCP1640, while
applications with significant operating time at low or no load conditions may benefit from the reduced power consumption
of the MCP16251.
No Load Input Current Requirements for MCP1640
and MCP16251
30
40
50
60
70
80
90
100
a
d Input Current (µA)
V
OUT
= 3.3V
MCP1640
0
10
20
1 1.2 1.4 1.6 1.8 2 2.2 2.4
No Lo
a
Input Voltage (V)
MCP16251/2
Light Load Efficiency of MCP1640 and MCP16251
100
80
90
)
V
IN
=25V
70
80
n
cy (%
)
V
OUT
= 3.3V
V
IN
= 2
.
5V
50
60
Efficie
n
40
50
MCP16251/2
MCP1640
30
0.01 0.1 1 10 100 1000
I
OUT
(mA)