LTC3555 Datasheet, PDF (1/32 Pages) Linear Technology – High Effi ciency USB Power Manager + Triple Step-Down DC/DC

FEATURES
Power Manager
n _{High Efficiency Switching PowerPath™ Controller}
with Bat-Track™ Adaptive Output Control
n _{Programmable USB or Wall Current Limit}
(100mA/500mA/1A)
n _{Full Featured Li-Ion/Polymer Battery Charger}
n _{1.5A Maximum Charge Current}
n _{Internal 180mΩ Ideal Diode + External Ideal Diode}
Controller Powers Load in Battery Mode
n _{Low No-Load Quiescent Current when Powered from}
BAT (<32μA)
DC/DCs
n _{Triple High Efficiency Step-Down DC/DCs}
(1A/400mA/400mA I_OUT)
n _{All Regulators Operate at 2.25MHz}
n _{Dynamic Voltage Scaling on Two Outputs}
n _I²_{C or Independent Enable, VOUT Controls}
n _{Low No-Load Quiescent Current: 20μA}
n _{28-Pin (4mm × 5mm × 0.75mm) QFN Package}
APPLICATIONS
n _{HDD-Based MP3 Players, PDAs, GPS, PMPs}
n _{Portable Medical Products}
n _{Handheld Instrumentation}
n _{Other USB-Based Handheld Products}
LTC3555/LTC3555-X
High Efficiency USB Power
Manager + Triple
Step-Down DC/DC
DESCRIPTION
The LTC^®3555 family are highly integrated USB com-
patible power management and battery charger ICs for
Li-Ion/Polymer battery applications. They include a high
efficiency current limited switching PowerPath manager
with automatic load prioritization, a battery charger, an ideal
diode and three general purpose synchronous step-down
switching regulators.
The LTC3555 family limits input current to either 100mA
or 500mA for USB applications or 1A for adapter-powered
applications. Unlike linear chargers, the LTC3555 family’s
switching architecture transmits nearly all of the power avail-
able from the USB port to the load with minimal loss and
heat which eases thermal constraints in small spaces.
Two of the three general purpose switching regulators can
provide up to 400mA and the third can deliver 1A. The
entire product can be controlled via I²C or simple I/O. The
LTC3555-1/LTC3555-3 versions offer “instant-on” power
delivery to the portable product even with a very low battery
voltage. The LTC3555-3 version also has a reduced charger
float voltage of 4.100V for battery safety and longevity.
The LTC3555 family is available in the low profile 28-pin
(4mm × 5mm × 0.75mm) QFN surface mount package.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. PowerPath
and Bat-Track are trademarks of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents, including 6522118 and 6404251.
TYPICAL APPLICATION
High Efficiency PowerPath Manager and Triple Step-Down Regulator
USB/WALL
4.35V TO 5.5V
CHARGE
ENABLE ⁵
CONTROLS
USB COMPLIANT
STEP-DOWN
REGULATOR
CURRENT
CONTROL
CC/CV
BATTERY
0V
CHARGER
LTC3555/LTC3555-X
ALWAYS ON LDO
TRIPLE
1
HIGH EFFICIENCY
STEP-DOWN
2
SWITCHING
REGULATORS
3
I²C PORT
TO OTHER
LOADS
OPTIONAL
+
T
Li-Ion
3.3V/25mA
0.8V TO 3.6V/400mA
0.8V TO 3.6V/400mA
0.8V TO 3.6V/1A
RST
2
RTC/LOW
POWER LOGIC
MEMORY
I/O
CORE
μPROCESSOR
I²C
3555 TA01
Switching Regulator Efficiency to
System Load (P_OUT/P_BUS)
100
90
80
70 BAT = 4.2V
60
BAT = 3.3V
50
40
30
20
10
0
0.01
V_BUS = 5V
I_BAT = 0mA
10x MODE
0.1
I_OUT (A)
1
3555 TA01b
3555fd
1