USB Power Manager with
Ideal Diode Controller and
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
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
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.
4.7μF SUSPEND USB POWER
100mA 500mA SELECT
Input and Battery Current vs Load Current
RPROG = 100k, RCLPROG = 2k
* OPTIONAL - TO LOWER
IDEAL DIODE IMPEDANCE
WALL = 0V
0 100 200 300 400 500 600