LTC4055-1_15 Datasheet, PDF (1/24 Pages) Linear Technology – USB Power Controller and Li-Ion Charger

LTC4055/LTC4055-1
USB Power Controller
and Li-Ion Charger
FEATURES
DESCRIPTION
n _{Charges Single-Cell Li-Ion Batteries Directly from}
USB Port
n _{Load Dependent Charging Guarantees USB Input}
Current Compliance
n _{Automatic Battery Switchover When Input Supply is}
Removed
n _{Constant-Current/Constant-Voltage Operation with}
Thermal Feedback to Maximize Charging Rate
Without Risk of Overheating*
n _{Selectable 500mA/100mA Current Limit}
n _{Low Loss Full PowerPath™ Control with Ideal Diode}
Operation (Reverse Current Blocking)
n _{Preset 4.2V Charge Voltage with 0.8% Accuracy}
(4.1V for LTC4055-1)
n _{4.1V Float Voltage (LTC4055-1) Improves Battery Life}
and High Temperature Safety Margin
n _{USB-Compliant Suspend Mode}
n _{Programmable Charge Current and Termination Timer}
n _{Soft-Start Limits Inrush Current}
n _{NTC Thermistor Input for Temperature Qualified}
Charging
n _{Tiny (4mm × 4mm × 0.75mm) QFN Package}
APPLICATIONS
n _{Portable USB Devices: Cameras, MP3 Players, PDAs}
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. *Protected by U.S. Patent, including 6522118.
The LTC^®4055/LTC4055-1 are USB power manager and
Li-Ion battery chargers designed to work in portable
battery-powered applications. The parts manage and limit
the total current used by the USB peripheral for operation
and battery charging. Depending on the state of the current
select pin (HPWR), total input current can be limited to
either 100mA or 500mA. The voltage drop from the USB
supply or battery to the USB peripheral is typically less than
100mV at 400mA and 20mV at 80mA. Other management
features include: automatic switchover to battery when
input is removed, inrush current limiting, reverse current
blocking, undervoltage lockout and thermal shutdown.
The LTC4055/LTC4055-1 include a complete constant-
current/constant-voltage linear charger for single-cell
Li-ion batteries. The float voltage applied to the battery
is held to a tight 0.8% tolerance, and charge current is
programmable using an external resistor to ground. Fully
discharged cells are automatically trickle charged at 10%
of the programmed current until the cell voltage exceeds
2.8V. Total charge time is programmable by an external
capacitor to ground. When the battery drops 100mV below
the float voltage, automatic recharging of the battery
occurs. Also featured is an NTC thermistor input used to
monitor battery temperature while charging.
The LTC4055/LTC4055-1 are available in a 16-pin low
profile (4mm × 4mm) QFN package.
TYPICAL APPLICATION
5V (NOM)
FROM USB
CABLE V_BUS
1Ω
10μF
SUSPEND USB POWER
500mA/100mA SELECT
IN1
IN2
V_NTC
NTC
WALL
LTC4055
SHDN
SUSP
HPWR
TIMER PROG CLPROG
OUT
BAT ₊
CHRG
ACPR
GND
Li-Ion
CELL
0.1μF
97.6k 97.6k
4055 TA01
TO SYSTEM
LOADS
10μF
Input and Battery Current vs Load Current
R_PROG = R_CLPROG = 97.6k
600
500
I_IN
400
I_LOAD
300
200
I_BAT
CHARGING
100
0
–100
0
I_BAT
(IDEAL DIODE)
100 200 300 400 500 600
I_LOAD (mA)
4055 TA02
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