LTC4081_15 Datasheet, PDF (1/24 Pages) Linear Technology – 500mA Li-Ion Charger with NTC Input and 300mA Synchronous Buck

FEATURES
Battery Charger:
nn _{Constant-Current/Constant-Voltage Operation}
with Thermal Feedback to Maximize Charge Rate
without Risk of Overheating
nn _{Internal 4.5-Hour Safety Timer for Termination}
nn _{Charge Current Programmable Up to 500mA with}
5% Accuracy
nn _{NTC Thermistor Input for Temperature Qualified}
Charging
nn _{C/10 Charge Current Detection Output}
nn _{5µA Supply Current in Shutdown Mode}
Switching Regulator:
nn _{High Efficiency Synchronous Buck Converter}
nn _{300mA Output Current (Constant-Frequency Mode)}
nn _{2.7V to 4.5V Input Range (Powered from BAT Pin)}
nn _{0.8V to VBAT Output Range}
nn _{MODE Pin Selects Fixed (2.25MHz) Constant-Frequency}
PWM Mode or Low I_CC (23µA) Burst Mode^® Operation
nn _{2µA BAT Current in Shutdown Mode}
nn _{10-Lead, Low Profile (0.75 mm) 3mm × 3mm DFN Package}
APPLICATIONS
nn _{Wireless Headsets}
nn _{Bluetooth Applications}
nn _{Portable MP3 Players}
nn _{Multifunction Wristwatches}
LTC4081
500mA Li-Ion Charger
with NTC Input and
300mA Synchronous Buck
DESCRIPTION
The LTC^®4081 is a complete constant-current/constant-
voltage linear battery charger for a single-cell 4.2V
lithium-ion/polymer battery with an integrated 300mA
synchronous buck converter. A 3mm × 3mm DFN pack-
age and low external component count make the LTC4081
especially suitable for portable applications. Furthermore,
the LTC4081 is specifically designed to work within USB
power specifications.
The CHRG pin indicates when charge current has dropped
to ten percent of its programmed value (C/10). An internal
4.5-hour timer terminates the charge cycle. The full-
featured LTC4081 battery charger also includes trickle
charge, automatic recharge, soft-start (to limit inrush
current) and an NTC thermistor input used to monitor
battery temperature.
The LTC4081 integrates a synchronous buck converter
that is powered from the BAT pin. It has an adjustable
output voltage and can deliver up to 300mA of load cur-
rent. The buck converter also features low current high
efficiency Burst Mode operation that can be selected by
the MODE pin.
The LTC4081 is available in a 10-lead, low profile (0.75mm)
3mm × 3mm DFN package.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
and ThinSOT and PowerPath are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents, including
6522118.
TYPICAL APPLICATION
Li-Ion Battery Charger with 1.8V Buck Regulator
510Ω
V_CC
(3.75V
TO 5.5V)
100k
4.7μF
100k T
V_CC
CHRG
BAT
EN_BUCK
NTC LTC4081 _SW
EN_CHRG
FB
MODE GND PROG
500mA
1OμH
10pF
806Ω
+
4.7μF
4.2V
Li-Ion/
POLYMER
BATTERY
1M
806k
V_OUT
(1.8V/300mA)
4.7μF
4081 TA01a
Buck Efficiency vs Load Current
(V_OUT = 1.8V)
100
1000
EFFICIENCY
80 _(Burst)
EFFICIENCY
(PWM)
60
100
POWER
LOSS 10
(PWM)
40
20
0
0.01
POWER LOSS
1
(Burst)
V_BAT = 3.8V
V_OUT = 1.8V
0.1
L = 10μH
C = 4.7μF
0.01
0.1
1
10 100 1000
LOAD CURRENT (mA)
4081 TA01b
For more information www.linear.com/LTC4081
4081fa
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