
LTC4085-3
1
40853f
ILOAD (mA)
0
600
500
400
300
200
100
0
–100
300
500
40853 TA01b
100
200
400
600
CURRENT
(mA)
ILOAD
IIN
IBAT
(CHARGING)
IBAT
(DISCHARGING)
WALL = 0V
USB Power Manager with
Ideal Diode Controller and
3.95V Li-Ion Charger
The LTC4085-3 is a USB power manager and Li-Ion/Poly-
mer 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 automatically reduced
such that the sum of the load current and charge current
does not exceed the programmed input current limit.
The LTC4085-3 includes a complete constant-current/
constant-voltage linear charger for single cell Li-Ion bat-
teries. This 3.95V version of the standard LTC4085 is
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 oat voltage will trade-off initial cell
capacity for the benet of increased capacity retention
over the life of the battery. A reduced oat voltage also
minimizes swelling in prismatic and polymer cells, and
avoids open CID (pressure fuse) in cylindrical cells.
The LTC4085-3 also includes a programmable termina-
tion timer, automatic recharging, an end-of-charge status
output and an NTC thermistor.
■
Portable USB Devices
■
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
■
Preset 3.95V Charge Voltage with ±0.8% Accuracy
■
C/10 Charge Current Detection Output
■
Tiny (4mm
× 3mm × 0.75mm) 14-Lead DFN Package
Input and Battery Current vs Load Current
RPROG = 100k, RCLPROG = 2k
IN
SUSP
HPWR
PROG
CLPROG
NTC
VNTC
WALL
ACPR
OUT
GATE
BAT
CHRG
TIMER
LTC4085-3
GND
+
0.1μF
4.7μF
TO LDOs,
REGs, ETC
10k
2k
100k
5V WALL
ADAPTER
INPUT
5V (NOM)
FROM USB
CABLE VBUS
4.7μF
SUSPEND USB POWER
100mA 500mA SELECT
1k
510Ω
40853 TA01
*
* OPTIONAL - TO LOWER
IDEAL DIODE IMPEDANCE
IIN
ILOAD
IBAT
FEATURES
DESCRIPTION
APPLICATIONS
TYPICAL APPLICATION
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.