LTC4085-3 Datasheet, PDF (1/24 Pages) Linear Technology – USB Power Manager with Ideal Diode Controller and 3.95V Li-Ion Charger

LTC4085-3/LTC4085-4
FEATURES
USB Power Manager with
Ideal Diode Controller and
3.95V Li-Ion Charger
DESCRIPTION
■ _{Seamless Transition Between Input Power Sources:}
Li-Ion/Polymer Battery, USB and 5V Wall Adapter
■ _{215mΩ Internal Ideal Diode Plus Optional External}
Ideal Diode Controller Provide Low Loss PowerPath^™
When Wall Adapter/USB Input Not Present
■ _{Load Dependent Charging Guarantees Accurate}
USB Input Current Compliance
■ _{3.95V Float Voltage Improves Battery Life Span and}
High Temperature Safety Margin
■ _{Constant-Current/Constant-Voltage Operation with}
Thermal Feedback to Maximize Charging Rate without
Risk of Overheating*
■ _{Selectable 100% or 20% Input Current Limit}
(e.g., 500mA/100mA)
■ _{Battery Charge Current Independently Programmable}
Up to 1.2A
■ _{Automatic Output Undervoltage Charge Current}
Reduction (LTC4085-3)
■ _{Tiny (4mm × 3mm × 0.75mm) 14-Lead DFN Package}
APPLICATIONS
■ _{Portable USB Devices}
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
Bat-Track, PowerPath and ThinSOT are trademarks 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.
The LTC^®4085-3/LTC4085-4 is a USB power manager
and Li-Ion/Polymer battery charger designed for portable
battery-powered applications. 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 programmed value up to 1.5A (typically
100mA or 500mA). Battery charge current is automati-
cally reduced such that the sum of the load current and
charge current does not exceed the programmed input
current limit.
The LTC4085-3/LTC4085-4 includes a complete constant-
current/constant-voltage linear charger for single cell Li-Ion
batteries. These 3.95V versions of the standard LTC4085
are intended for applications which have extended battery
lifetime requirements or those that require high temperature
(approximately >60°C) operation or storage. Under these
conditions, a reduced float voltage will trade-off initial cell
capacity for the benefit of increased capacity retention
over the life of the battery. A reduced float voltage also
minimizes swelling in prismatic and polymer cells, and
avoids open CID (pressure fuse) in cylindrical cells.
The LTC4085-3/LTC4085-4 also includes a programmable
termination timer, automatic recharging, an end-of-charge
status output and an NTC thermistor.
TYPICAL APPLICATION
5V WALL
ADAPTER
INPUT
5V (NOM)
FROM USB
CABLE V_BUS
I_IN
4.7μF ^{SUSPEND USB POWER}
100mA 500mA SELECT
IN
SUSP
WALL
ACPR
HPWR
OUT
LTC4085-3/
PROG LTC4085-4 GATE
CLPROG
BAT
NTC
CHRG
V_NTC
10k
GND TIMER
100k 2k
10k
I_LOAD
TO LDOs,
REGs, ETC
1k
4.7μF
510Ω
*
I_BAT
+
0.1μF
* OPTIONAL - TO LOWER
IDEAL DIODE IMPEDANCE
408534 TA01
Input and Battery Current vs Load Current
R_PROG = 100k, R_CLPROG = 2k
600
I_IN
500
400
I_LOAD
300
200
I_BAT
(CHARGING)
100
0
I_BAT
WALL = 0V
(DISCHARGING)
–100
0 100 200 300 400 500 600
I_LOAD (mA)
408534 TA01b
408534fb
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