LTC3555/LTC3555-X
1
3555fe
For more information www.linear.com/LTC3555
n
HDD-Based MP3 Players, PDAs, GPS, PMPs
n
Portable Medical Products
n
Handheld Instrumentation
n
Other USB-Based Handheld Products
FEATURES
APPLICATIONS
DESCRIPTION
High Efficiency USB Power
Manager + Triple
Step-Down DC/DC
The LT C
®
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
available 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 I
2
C 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.
High Efficiency PowerPath Manager and Triple Step-Down Regulator
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
I
2
C or Independent Enable, V
OUT
Controls
n
Low No-Load Quiescent Current: 20µA
n
28-Pin (4mm × 5mm × 0.75mm) QFN Package
Switching Regulator Efficiency to
System Load (P
OUT
/P
BUS
)
Li-Ion
0.8V TO 3.6V/400mA
3.3V/25mA
0.8V TO 3.6V/400mA
0.8V TO 3.6V/1A
RST
2
OPTIONAL
0V
T
TO OTHER
LOADS
+
LTC3555/LTC3555-X
TRIPLE
HIGH EFFICIENCY
STEP-DOWN
SWITCHING
REGULATORS
I
2
C PORT
ALWAYS ON LDO
MEMORY
RTC/LOW
POWER LOGIC
I
2
C
CORE
I/O
µPROCESSOR
USB/WALL
4.35V TO 5.5V
CHARGE
ENABLE
CONTROLS
USB COMPLIANT
STEP-DOWN
REGULATOR
CC/CV
BATTERY
CHARGER
5
1
2
3
CURRENT
CONTROL
I
OUT
(A)
0.01
0
20
40
60
80
0.1 1
3555 TA01b
10
30
50
70
90
BAT = 4.2V
BAT = 3.3V
V
BUS
= 5V
I
BAT
= 0mA
10x MODE
TYPICAL APPLICATION
L, LT, LTC, LTM Linear Technology, the Linear logo and Burst Mode are registered trademarks
and 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.