LTC3550-1_15 Datasheet, PDF (1/24 Pages) Linear Technology – Dual Input USB/AC Adapter Li-Ion Battery Charger with 600mA Buck Converter

LTC3550-1
FEATURES
Dual Input USB/AC Adapter
Li-Ion Battery Charger with
600mA Buck Converter
DESCRIPTIO
■ _{Charges Single-Cell Li-Ion Batteries from Wall}
Adapter and USB Inputs
■ _{Automatic Input Power Detection and Selection}
■ _{Charge Current Programmable Up to 950mA from}
Wall Adapter Input
■ _{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}
■ _{Independent “Power Present” Status Outputs}
■ _{Charge Status Output}
■ _{Automatic Recharge}
■ _{Available in a Thermally Enhanced, Low Profile}
(0.75mm) 16-Lead (5mm x 3mm) DFN Package
U
APPLICATIO S
■ _{Cellular Telephones}
The LTC^®3550-1 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 LTC3550-1
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 LTC3550-1 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 synchronous buck converter generates a fixed output
voltage of 1.875V. The switching frequency is internally
set at 1.5MHz, allowing the use of small surface mount
inductors and capacitors.
, LTC and LT 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
2k
1%
1µF
LTC3550-1
RUN
SW
DCIN
USBIN
IUSB
V_OUT
V_CC
BAT
IDC ITERM
1.24k
GND
1%
2.2µH
800mA (WALL)
500mA (USB)
V_OUT
1.875V
C_OUT ^600mA
10µF
CER
4.7µF
2k
1%
+ ^4.2V
SINGLE-CELL
Li-Ion BATTERY
3550-1 TA01
Complete Charge Cycle (1100mA Battery)
1000
800
600
400
200
0
4.2
4.0
3.8
3.6
3.4
5.0
2.5
0
–2.5
0
CONSTANT VOLTAGE
USBIN = 5V
T_A = 25°C
R_IDC = 1.25k
R_IUSB = 2k
0.5 1.0 1.5 2.0 2.5 3.0
TIME (HR)
3550-1 TA02
35501f
1