LTC4085-3/LTC4085-4
USB Power Manager with
Ideal Diode Controller and
3.95V Li-Ion Charger
DESCRIPTION
FEATURES
■
Seamless Transition Between Input Power Sources:
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.
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*
The LTC4085-3/LTC4085-4 includes a complete constant-
current/constant-voltagelinearchargerforsinglecellLi-Ion
batteries. These 3.95V versions of the standard LTC4085
are intended for applications which have extended battery
lifetimerequirementsorthosethatrequirehightemperature
(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.
■
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
The LTC4085-3/LTC4085-4 also includes a programmable
terminationtimer,automaticrecharging,anend-of-charge
status output and an NTC thermistor.
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.
TYPICAL APPLICATION
I
LOAD
Input and Battery Current vs Load Current
5V WALL
ADAPTER
INPUT
TO LDOs,
RPROG = 100k, RCLPROG = 2k
REGs, ETC
600
4.7μF
1k
I
IN
510Ω
I
5V (NOM)
IN
500
400
300
200
100
0
FROM USB
IN
WALL
ACPR
OUT
CABLE V
BUS
SUSPEND USB POWER
100mA 500mA SELECT
SUSP
HPWR
4.7μF
I
LOAD
LTC4085-3/
LTC4085-4
I
BAT
(CHARGING)
PROG
GATE
*
CLPROG
NTC
BAT
CHRG
TIMER
I
BAT
(DISCHARGING)
WALL = 0V
100
I
GND
V
NTC
BAT
–100
0
200
300 500
400
(mA)
600
+
10k
I
LOAD
408534 TA01b
*
OPTIONAL - TO LOWER
IDEAL DIODE IMPEDANCE
0.1μF
100k
2k
10k
408534 TA01
408534fb
1