FAN4855 Datasheet, PDF (1/12 Pages) Fairchild Semiconductor – 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
diode)
■ Low-battery detection
■ Logic controlled shutdown with true-load disconnect
■ Low (80µA) quiescent current
■ TSSOP-8 Package
Applications
■ DSCs
■ PDAs
■ Cell phones, smart phones
■ Portable instrumentations
■ 2-3 AA / AAA cells operated devices
■ Single cell Li-Ion operated devices
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.
Ordering Information (T_A = -40°C to +85°C)
Part Number
FAN4855MTC
FAN4855MTCX
Package
8 Pin TSSOP
8 Pin TSSOP
Packing
Rails
Tape and Reel
Typical Application
Input 1.6V
to 4.5V
On
Off
Low Battery
Detect In
Low Battery
Detect Out
FAN4855
1 V_IN
GND 8
2 SHDN V_L 7
3 LBI
4 LB0
V_OUT ⁶
FB 5
Output 3.3V to 5V
up to 0.5A
©2005 Fairchild Semiconductor Corporation
1
FAN4855 Rev. 1.0.1
www.fairchildsemi.com