LTC3550_15 Datasheet, PDF (1/24 Pages) Linear Technology – Dual Input USB/AC Adapter Li-Ion Battery Charger with 600mA Buck Converter

LTC3550
Dual Input USB/AC Adapter
Li-Ion Battery Charger with
600mA Buck Converter
FEATURES
■ _{Charges Single-Cell Li-Ion Battery from Wall}
Adapter and USB Inputs
■ _{Automatic Input Power Detection and Selection}
■ _{Charge Current Programmable Up to 950mA from}
Wall Adapter Input
■ _{Adjustable Output, High Efficiency 600mA}
Synchronous DC/DC Converter
■ _{No External MOSFET, Sense Resistor or Blocking}
Diode Needed
■ _{Thermal Regulation Maximizes Charge Rate Without}
Risk of Overheating*
■ _{Preset Charge Voltage with ±0.6% Accuracy}
■ _{Programmable Charge Current Termination}
■ _{1.5MHz Constant Frequency Operation (Step-Down}
Converter)
■ _{18μA USB Suspend Current in Shutdown}
■ _{“Power Present” Status Output}
■ _{Charge Status Output}
■ _{Automatic Recharge}
■ _{Available in a Thermally Enhanced, Low Profile}
(0.75mm) 16-Lead (5mm × 3mm) DFN Package
U
APPLICATIO S
■ _{Cellular Telephones}
DESCRIPTIO
The LTC^®3550 is a standalone linear charger with a 600mA
monolithic synchronous buck converter. It is capable of
charging a single-cell Li-Ion battery from both wall adapter
and USB inputs. The charger automatically selects the
appropriate power source for charging.
Internal thermal feedback regulates the battery charge
current to maintain a constant die temperature during high
power operation or high ambient temperature conditions.
The float voltage is fixed at 4.2V and the charge currents
are programmed with external resistors. The LTC3550
terminates the charge cycle when the charge current
drops below the programmed termination threshold after
the final float voltage is reached. With power applied to
both inputs, the LTC3550 can be put into shutdown mode
reducing the DCIN supply current to 20μA, the USBIN
supply current to 10μA, and the battery drain current to
less than 2μA.
The DC/DC converter switching frequency is internally
set at 1.5MHz, allowing the use of small surface mount
inductors and capacitors.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
*Protected by U.S. patents, includng 6522118, 6700364, 6580258, 5481178, 6304066,
6127815, 6498466, 6611131
TYPICAL APPLICATIO
Dual Input Battery Charger and DC/DC Converter
WALL
ADAPTER
USB
PORT
1µF
1µF
SW
LTC3550
DCIN
V_FB
RUN
USBIN V_CC
IUSB BAT
2k
1%
IDC ITERM
1.24k
GND
1%
2.2µH
22pF 301k
V_OUT
1.2V
C_OUT ^600mA
10µF
CER
301k
800mA (WALL)
500mA (USB)
4.7µF
2k
1%
+ ^4.2V
SINGLE-CELL
Li-Ion BATTERY
3550 TA01
1000
800
600
400
200
0
4.2
4.0
3.8
3.6
3.4
5.0
2.5
0
0
Complete Charge Cycle
(1100mA Battery)
CONSTANT VOLTAGE
USBIN = 5V
T_A = 25°C
R_IDC = 1.24k
R_IUSB = 2k
0.5 1.0 1.5 2.0 2.5 3.0
TIME (HR)
3550 TA02
3550fa
1