Document
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 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 includes a complete constant-current/ constant-voltage linear charger for single cell Li-ion batteries. 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 temperature 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 VBUS
IIN 4.7μF SUSPEND USB POWER
100mA 500mA SELECT
10k
IN SUSP
WALL ACPR
HPWR PROG
LTC4085
OUT GATE
CLPROG NTC
BAT CHRG
VNTC
GND TIMER
100k 2k
10k
Input and Battery Current vs Load Current
ILOAD
TO LDOs, REGs, ETC 4.7μF
RPROG = 100k, RCLPROG = 2k
600
IIN 500
1k
510Ω
400 ILOAD
300
*
200
IBAT
(CHARGING)
CURRENT (mA)
100
IBAT
+
0.1μF
* OPTIONAL - TO LOWER
IDEAL DIODE IMPEDANCE
4085 TA01
0 IBAT
WALL = 0V
(DISCHARGING)
–100
0 100 200 300 400 500 600
ILOAD (mA)
4085 TA01b
4085fd
1
LTC4085
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2, 3, 4, 5)
Terminal Voltag.