LTC4080 Datasheet, PDF (1/20 Pages) Linear Technology – 500mA Standalone Li-Ion Charger with Integrated 300mA Synchronous Buck

FEATURES
■ _{Complete Linear Battery Charger with Integrated}
Buck Converter
Battery Charger:
■ _{Constant-Current/Constant-Voltage Operation}
with Thermal Feedback to Maximize Charge Rate
Without Risk of Overheating
■ _{Internal 4.5 Hour Safety Timer for Termination}
■ _{Charge Current Programmable Up to 500mA with}
5% Accuracy
■ _{C/10 Charge Current Detection Output}
■ _{5μA Supply Current in Shutdown Mode}
Switching Regulator:
■ _{High Efficiency Synchronous Buck Converter}
■ _{300mA Output Current}
■ _{2.7V to 4.5V Input Range (Powered from BAT Pin)}
■ _{0.8V to VBAT Output Range}
■ _{MODE Pin Selects Fixed (2.25MHz) Constant-Frequency}
PWM Mode or Low I_CC (23μA) Burst Mode^®
Operation
■ _{2μA BAT Current in Shutdown Mode}
U
APPLICATIO S
■ _{Wireless Headsets}
■ _{Bluetooth Applications}
■ _{Portable MP3 Players}
■ _{Multifunction Wristwatches}
LTC4080
500mA Standalone Li-Ion
Charger with Integrated
300mA Synchronous Buck
DESCRIPTIO
The LTC4080 is a complete constant-current/constant-
voltage linear battery charger for a single-cell 4.2V
lithium-ion battery with an integrated 300mA synchron-
ous buck converter. The small packages and low external
component count make the LTC4080 especially suitable for
portable applications. Furthermore, LTC4080 is specifically
designed to work within USB power specifications.
The ^⎯C^⎯H^⎯R^⎯G 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 LTC4080 battery charger also includes
trickle charge, automatic recharge and soft-start (to limit
inrush current).
The LTC4080 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 LTC4080 is available in 10-lead, low profile (0.75 mm)
3mm × 3mm DFN and MSOP Exposed Pad packages.
, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology
Corporation. All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 6522118.
TYPICAL APPLICATIO
Li-Ion Battery Charger with 1.8V Buck Regulator
V_CC
(3.75V
to 5.5V)
C_IN
4.7μF
V_CC
BAT
LTC4080
EN_CHRG
SW
L1, 1OμH
500mA
C_BAT ⁺
4.7μF
4.2V
Li-Ion
BATTERY
EN_BUCK
FB
MODE GND PROG
C_PL
10pF
R_PROG
806Ω
R1
1M
R2
806k
4080 TA01a
V_OUT
(1.8V/300mA)
C_OUT
4.7μF
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
0
(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)
4080 TA01b
4080fb
1