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FAN4855 500mA High Efficiency Boost Regulator with Adjustable Output, Shutdown and Low Battery Detect
December 2005
FAN4855
500mA High Efficiency Boost Regulator with Adjustable
Output, Shutdown and Low Battery Detect
Features
■
Low power PFM boost regulator
■
Input voltage range is from 1.6V to 4.5V
■
Output voltage range is from 3V to 5V
■
500mA maximum load current capability
■
95% efficient power conversion
■
2-3 cell and single cell Li-Ion systems
■
Variable on-time Pulse Frequency Modulation (PFM)
■
Internal synchronous rectifier (no need for external
■
■
■
■
General Description
The FAN4855 is a low power boost regulator designed
for low voltage DC to DC conversion in 2-cell battery
powered systems such as digital cameras, cell phones
and PDAs. The converter starts-up at 1.3V and operates
after the start at an input voltage as low as 1V. Output
voltage can be adjusted by external resistors from 3.3V
to 5V with a maximum load current of 0.5A. Quiescent
current in shut-down mode is less than 10µA, which
maximizes the battery live time. The ON time changes
with the input voltage to maintain the ripple current con-
stant and to provide the highest efficiency over a wide
load range—while maintaining low peak currents in the
boost inductor. The combination of built-in power transis-
tors, synchronous rectification and low supply current,
make the FAN4855 ideal for portable applications. The
FAN4855 is available in 8-lead TSSOP package.
diode)
Low-battery detection
Logic controlled shutdown with true-load disconnect
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