LTC4085_15 Datasheet, PDF (1/24 Pages) Linear Technology – USB Power Manager with Ideal Diode Controller and Li-Ion Charger

LTC4085
FEATURES
USB Power Manager with
Ideal Diode Controller and
Li-Ion Charger
DESCRIPTION
n _{Seamless Transition Between Input Power Sources:}
Li-Ion Battery, USB and 5V Wall Adapter
n _{215mΩ Internal Ideal Diode Plus Optional External}
Ideal Diode Controller Provide Low Loss PowerPath™
When Wall Adapter/USB Input Not Present
n _{Load Dependent Charging Guarantees Accurate USB}
Input Current Compliance
n _{Constant-Current/Constant-Voltage Operation with}
Thermal Feedback to Maximize Charging Rate Without
Risk of Overheating*
n _{Selectable 100% or 20% Input Current Limit}
(e.g., 500mA/100mA)
n _{Battery Charge Current Independently Programmable}
Up to 1.2A
n _{Preset 4.2V Charge Voltage with 0.8% Accuracy}
n _{C/10 Charge Current Detection Output}
n _{NTC Thermistor Input for Temperature Qualified Charging}
n _{Tiny (4mm × 3mm × 0.75mm) 14-Lead DFN Package}
APPLICATIONS
n _{Portable USB Devices: Cameras, MP3 Players, PDAs}
The LTC^®4085 is a USB power manager and Li-Ion battery
charger designed for portable battery-powered applica-
tions. The part controls the total current used by the USB
peripheral for operation and battery charging. The total
input current can be limited to 20% or 100% of a pro-
grammed value up to 1.5A (typically 100mA or 500mA).
Battery charge current is automatically reduced such that
the sum of the load current and charge current does not
exceed the programmed input current limit.
The LTC4085 includes a complete constant-current/
constant-voltage linear charger for single cell Li-ion bat-
teries. 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. An end-of-charge
status output CHRG indicates full charge. 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 tem-
perature while charging.
The LTC4085 is available in a 14-lead low profile 4mm ×
3mm DFN package.
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. Patents, including 6522118,6700364.
Other patents pending.
TYPICAL APPLICATION
5V WALL
ADAPTER
INPUT
5V (NOM)
FROM USB
CABLE V_BUS
I_IN
4.7μF SUSPEND USB POWER
100mA 500mA SELECT
10k
IN
SUSP
WALL
ACPR
HPWR
PROG
LTC4085
OUT
GATE
CLPROG
NTC
BAT
CHRG
V_NTC
GND TIMER
100k 2k
10k
Input and Battery Current vs Load Current
I_LOAD
TO LDOs,
REGs, ETC
4.7μF
R_PROG = 100k, R_CLPROG = 2k
600
I_IN
500
1k
510Ω
400
I_LOAD
300
*
200
I_BAT
(CHARGING)
100
I_BAT
+
0.1μF
* OPTIONAL - TO LOWER
IDEAL DIODE IMPEDANCE
4085 TA01
0
I_BAT
WALL = 0V
(DISCHARGING)
–100
0 100 200 300 400 500 600
I_LOAD (mA)
4085 TA01b
4085fd
1