LTC3455 Datasheet, PDF (1/24 Pages) Linear Technology – Dual DC/DC Converter with USB Power Manager and Li-Ion Battery Charger

FEATURES
s _{Seamless Transition between Input Power Sources:}
Li-Ion Battery, USB, and 5V Wall Adapter
s _{Accurate USB Current Limiting (500mA/100mA)}
s _{Two High Efficiency DC/DC Converters: Up to 96%}
s _{Thermal Regulation Maximizes Battery Charge}
Rate without Risk of Overheating*
s _{Full-Featured Li-Ion Battery Charger}
s _{Hot Swap™ Output for SDIO and Memory Cards}
s _{Pin-Selectable Burst Mode}^® _Operation
s _{Output Disconnect: All Outputs Discharged to}
Ground During Shutdown
s _{Available in a 4mm × 4mm × 0.8mm 24-Pin}
QFN Package
U
APPLICATIO S
s _{Handheld Computers}
s _{Digital Cameras}
s _{MP3 Players}
LTC3455
Dual DC/DC Converter
with USB Power Manager
and Li-Ion Battery Charger
DESCRIPTIO
The LTC^®3455 is a complete power management solution
for a variety of portable applications. The device contains
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 provides 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 dis-
charged to ground during shutdown to provide complete
output disconnect. The device is available in a
4mm × 4mm 24-pin exposed-pad QFN package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
*U.S. Patent 6,522,118
TYPICAL APPLICATIO
8
USB 5V
6
1Ω
USB
4.7µF
CONTROLLER
5
WALL 5V
1Ω
1µF
10
10µF
3.32k
1.24k
1k
4
11
0.1µF
3
2
2.49k
9
SINGLE
CELL Li-ION
+
3.3V TO 4.2V
4.7µF
1.8V
1M
LBO
17
V_BAT
2.49M
16
806k
21
USB
MODE
SUSPEND
15
HSON
19
USBHP
ON2
22
µC
PWRON
V_MAX
20
RST
23
PBSTAT
LTC3455
CHRG
WALLFB
TIMER
PROG
V_BAT
AO
AI
1M 1M
1.8V
24
ON
14
HSO
ON/OFF
3.3V, HS
1µF
13
HSI
12 ^4.7µH
SW2
10pF
249k
18
FB2
80.6k
7
SW1
1
FB1
25
GND
3455 TA01a
4.7µH
10pF
100k
80.6k
3.3V
0.5A
10µF
1.8V
0.4A
10µF
Efficiency
100
SWITCHER 2
95 VOUT2 = 3.3V
90
85
SWITCHER 1
V_OUT1 = 1.8V
80
75
70
65
60 ^{VBAT = 3.6V}
1
10
100
LOAD CURRENT (mA)
1000
3455 TA01b
3455f
1