LTC3455_15 Datasheet, PDF (1/28 Pages) Linear Technology – Dual DC/DC Converter with USB Power Manager and Li-Ion Battery Charger

LTC3455/LTC3455-1
Dual DC/DC Converter
with USB Power Manager
and Li-Ion Battery Charger
FEATURES
DESCRIPTION
n _{Seamless Transition between Input Power Sources:}
Li-Ion Battery, USB, and 5V Wall Adapter
n _{Accurate USB Current Limiting (500mA/100mA)}
n _{Two High Efficiency DC/DC Converters: Up to 96%}
n _{Thermal Regulation Maximizes Battery Charge}
Rate without Risk of Overheating
n _{Full-Featured Li-Ion Battery Charger with 4.2V Float}
Voltage for LTC3455 and 4.1V for LTC3455-1
n _{4.1V Float Voltage (LTC3455-1) Improves Battery Life}
and High Temperature Safety Margin
n _{Hot Swap™ Output for SDIO and Memory Cards}
n _{Pin-Selectable Burst Mode}^® _Operation
n _{Output Disconnect: All Outputs Discharged to Ground}
During Shutdown
n _{Available in a 4mm × 4mm × 0.75mm 24-Pin}
QFN Package
APPLICATIONS
n _{Handheld Computers}
n _{Digital Cameras}
n _{MP3 Players}
The LTC^®3455/LTC3455-1 are complete power manage-
ment solutions for a variety of portable applications.
These devices contain two synchronous step-down
DC/DC converters, a USB power controller, a full-featured
Li-Ion battery charger, a Hot Swap output, a low-battery
indicator, and numerous internal protection features. The
LTC3455/LTC3455-1 provide a small, simple solution for
obtaining power from three different power sources: a
single-cell Li-Ion battery, a USB port, and a wall adapter.
Current drawn from the USB bus is accurately limited
under all conditions. Whenever a USB or a wall adapter
is present, the battery charger is enabled and all internal
power for the device is drawn from the appropriate external
power source. All outputs are discharged to ground during
shutdown to provide complete output disconnect. These
devices are available in a 4mm × 4mm 24-pin exposed-
pad QFN package.
L, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents including 6522118.
TYPICAL APPLICATION
USB 5V
1Ω
4.7μF
WALL 5V
1Ω
4.7μF
USB
5.6V _CONTROLLER
10μF
3.32k
1k
1.24k
0.1μF
2.49k
SINGLE
CELL Li-ION
+
3.3V TO 4.2V
4.7μF
1.8V
1M
LBO
V_BAT
2.49M
806k
USB
SUSPEND
USBHP
V_MAX
MODE
HSON
ON2
PWRON
RST
PBSTAT
LTC3455/LTC3455-1
CHRG
WALLFB
ON
HSO
TIMER
PROG
HSI
V_BAT
SW2
FB2
AO
SW1
AI
FB1
GND
3455 TA01a
μC
1M 1M
1.8V
ON/OFF
3.3V, HS
1μF
4.7μH
10pF
4.7μH
10pF
249k
80.6k
3.3V
0.5A
10μF
100k
80.6k
1.8V
0.4A
10μF
Efficiency
100
SWITCHER 2
95 VOUT2 = 3.3V
1000
90
85
SWITCHER 1
100
V_OUT1 = 1.8V
80
75
70
10
POWER LOSS FOR
65
BOTH OUTPUTS
60
55
1
V_BAT = 3.6V ₁
10
100
1000
LOAD CURRENT (mA)
3455 TA01b
3455fc
1