LTC3456
2-Cell, Multi-Output
DC/DC Converter with
USB Power Manager
U
FEATURES
DESCRIPTIO
■
The LTC®3456 is a complete power management system
IC optimized for a variety of portable applications. The
device generates two separate power rails: a 3.3V (fixed)
Main supply and a 1.8V (adjustable) Core supply. In
addition, the LTC3456 contains a USB power manager, a
Hot Swap output, a low-battery indicator and an alwaysalive VMAX output. The LTC3456 takes power from one of
three sources: a Wall adapter, a USB port or a 2-cell
Alkaline/NiCd/NiMH battery, in that order of priority. Current drawn from the USB port is accurately limited to
100mA or 500mA based on the state of the USBHP pin.
■
■
■
■
■
■
■
■
■
Seamless Transition Between 2-Cell Battery, USB
and AC Wall Adapter Input Power Sources
Main Output: Fixed 3.3V Output
Core Output: Adjustable from 0.8V to VBATT(MIN)
Hot SwapTM Output for Memory Cards
All Outputs Discharged to Ground During Shutdown
Power Supply Sequencing: Main and Hot Swap
Outputs Come Up After Core Output
Accurate USB Current Limiting
High Frequency Operation: 1MHz
High Efficiency: Up to 92%
Small (4mm × 4mm × 0.75mm) 24-Pin QFN Package
U
APPLICATIO S
■
■
■
■
GPS Portable Navigators
MP3 Players
Digital Cameras
Handheld Computers
The Main and Core switchers are all high efficiency, 1MHz
fixed frequency PWM converters. Availability in a small
(4mm × 4mm × 0.75mm) 24-pin QFN package makes the
LTC3456 ideal for space-sensitive portable devices.
, LTC and LT 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 5481178,
6580258, 6304066.
U
TYPICAL APPLICATIO
+
4.7µF
L2
4.7µH
100k
VBATT
22µF
L3
10µH
SW2_BST
SW2_BK
AIN
VINT
80.6k
AO
4.7µF
USB
CONTROLLER
1Ω
HSO
L1
10µH
SUSPEND
LTC3456
USB
SW1
1k
AC WALL
ADAPTER
(5V ±10%)
220pF
VEXT
11.3k
FB1
10µF
WALLFB
ON/OFF
VMAX
PWRKEY
PBSTAT RESET MODE PWRON PGND AGND
250
VBATT = 2.4V
90 MODE = 0V
200
80
1.8V
OUTPUT
70
60
3.3V
OUTPUT
40
POWER LOSS
30
3.3V
OUTPUT
1.8V
OUTPUT
10
VMAX
(POWERS
1µF REAL-TIME CLOCK)
150
EFFICIENCY
50
20
80.6k
1Ω
4.32k
CORE OUTPUT
1.8V
10µF 200mA
100k
EXT_PWR
4.7µF
Hot Swap OUTPUT
3.3V
1µF 50mA
100
0
1
10
100
LOAD CURRENT (mA)
100
POWER LOSS (mW)
USB POWER
(4.35V TO 5.5V)
Efficiency and Power Loss
vs Load Current
(Battery Powered)
MAIN OUTPUT
3.3V
1µF 150mA
VMAIN
USBHP
VINT
3.3V
EFFICIENCY (%)
2 AA
CELLS
50
0
1000
3456 TA01b
µP
3456 TA01
3456fa
1
