1
LTC3456
3456f
2-Cell, Multi-Output
DC/DC Converter with
USB Power Manager
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 V
BATT(MIN)
Hot Swap
TM
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
GPS Portable Navigators
MP3 Players
Digital Cameras
Handheld Computers
DESCRIPTIO
U
FEATURES
APPLICATIO S
U
TYPICAL APPLICATIO
U
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 always-
alive V
MAX
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. Cur-
rent drawn from the USB port is accurately limited to
100mA or 500mA based on the state of the USBHP pin.
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.
+
WALLFB
PWRKEY
V
MAX
V
EXT
10F
4.7F
4.7F
1k
11.3k
1
4.7F
1
AC WALL
ADAPTER
(5V 10%)
USB POWER
(4.35V TO 5.5V)
USB
CONTROLLER
4.32k
80.6k
100k
L2
4.7H
2 AA
CELLS
L3
10H
EXT_PWR
USB
SUSPEND
USBHP
AO
AIN
V
MAIN
V
BATT
V
INT
SW2_BST
LTC3456
SW2_BK
PBSTAT RESET MODE
P
PWRON PGND AGND
22F
V
INT
3.3V
MAIN OUTPUT
3.3V
150mA
1F
HSO
Hot Swap OUTPUT
3.3V
50mA
1F
1F
3456 TA01
SW1
FB1
L1
10H
CORE OUTPUT
1.8V
200mA
V
MAX
(POWERS
REAL-TIME CLOCK)
10F
220pF
100k
80.6k
LOAD CURRENT (mA)
1
40
EFFICIENCY (%)
POWER LOSS (mW)
50
60
70
80
10
100
1000
3456 TA01b
30
20
10
0
90
100
100
150
200
50
0
250
V
BATT
= 2.4V
MODE = 0V
EFFICIENCY
POWER LOSS
1.8V
OUTPUT
1.8V
OUTPUT
3.3V
OUTPUT
3.3V
OUTPUT
Efficiency and Power Loss
vs Load Current
(Battery Powered)
, 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.
2
LTC3456
3456f
(Note 1)
V
BATT
, V
MAX
Voltages ................................. 0.3V to 6V
V
INT
, V
MAIN
, V
EXT
, HSO Voltages ................ 0.3V to 6V
SW1, SW2_BK, SW2_BST Voltages ........... 0.3V to 6V
USB, USBHP, SUSPEND Voltages .............. 0.3V to 6V
PWRKEY, PBSTAT, PWRON Voltages ........ 0.3V to 6V
MODE, AO, EXT_PWR, RESET Voltages ..... 0.3V to 6V
FB1, AIN, WALLFB Voltages ....................... 0.3V to 2V
Junction Temperature .......................................... 125C
Operating Temperature Range (Note 2) .. 40C to 85C
Storage Temperature Range ................. 65C to 125C
ABSOLUTE AXI U RATI GS
W
W
W
U
ELECTRICAL CHARACTERISTICS
The
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25C.
V
BATT
= 2.4V, V
INT
= 3.3V, V
PWRON
= 2V, PWRKEY is open, V
USB
= 0V, V
WALLFB
= 0V, unless otherwise specified.
ORDER PART
NUMBER
LTC3456EUF
T
JMAX
= 125C,
JA
= 37C/ W,
JC
= 2C/ W
EXPOSED PAD (PIN 25) IS PGND
MUST BE SOLDERED TO PCB
PACKAGE/ORDER I FOR ATIO
U
U
W
UF PART
MARKING
Consult LTC Marketing for parts specified with wider operating temperature ranges.
3456
24 23 22 21 20 19
7
8
9
TOP VIEW
25
UF PACKAGE
24-LEAD (4mm 4mm) PLASTIC QFN
10 11 12
6
5
4
3
2
1
13
14
15
16
17
18
AIN
AO
AGND
V
BATT
SW1
PGND
SUSPEND
HSO
V
MAIN
V
INT
SW2_BST
SW2_BK
FB1
RESET
MODE
PWRON
PBSTAT
PWRKEY
WALLFB
EXT_PWR
V
EXT
USB
V
MAX
USBHP
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Battery Voltage Range
1.8
3.2
V
Quiescent Current (Battery Powered)
(Note 3)
Burst Mode
Operation
V
MODE
= 2V, V
FB1
= 1V, V
INT
= 3.4V
180
250
A
PWM Operation
V
MODE
= 0V, V
FB1
= 1V, V
INT
= 3.4V
380
450
A
Shutdown
V
PWRON
= 0V, V
INT
= 0V
0.1
1
A
V
BATT
Pin Current (Wall Powered)
V
WALLFB
= 1.5V, V
EXT
= 5V (Note 4)
1
2
A
V
BATT
Pin Current (USB Powered)
V
USB
= 5V, V
EXT
= 5V (Note 4)
1
2
A
Switching Frequency
Battery Powered
V
BATT
= 2.4V
0.8
1
1.2
MHz
USB or Wall Powered
V
EXT
= 5V, V
WALLFB
= 1.5V
0.8
1
1.2
MHz
Main Output
V
INT
Voltage Regulation
3.22
3.3
3.38
V
V
INT
Voltage Line Regulation
V
BATT
= 1.8V to 3.2V
0.1
0.5
%/V
Max Duty Cycle
80
87
%
Switch Leakage (Battery Powered)
SW2_BST PMOS Switch
V
SW2_BST
= 0V
0.1
1
A
SW2_BST NMOS Switch
V
SW2_BST
= 3.3V
0.1
1
A
Switch On-Resistance (Battery Powered)
SW2_BST PMOS Switch
I
SW2_BST
= 150mA
0.8
SW2_BST NMOS Switch
I
SW2_BST
= 150mA
0.5
Burst Mode is a registered trademark of Linear Technology
3
LTC3456
3456f
ELECTRICAL CHARACTERISTICS
The
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25C.
V
BATT
= 2.4V, V
INT
= 3.3V, V
PWRON
= 2V, PWRKEY is open, V
USB
= 0V, V
WALLFB
= 0V, unless otherwise specified.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Switch Leakage (USB/Wall Powered)
V
EXT
= 5V, V
WALLFB
= 1.5V
SW2_BK PMOS Switch
V
SW2_BK
= 0V
0.1
1
A
SW2_BK NMOS Switch
V
SW2_BK
= 5V
0.1
1
A
Switch On-Resistance (USB/Wall Powered)
V
EXT
= 5V, V
WALLFB
= 1.5V
SW2_BK PMOS Switch
I
SW2_BK
= 150mA
0.9
SW2_BK NMOS Switch
I
SW2_BK
= 150mA
0.4
Switch Current Limit
Battery Powered (SW2_BST NMOS Current)
V
BATT
= 2.4V
700
900
mA
Wall/USB Powered (SW2_BK PMOS Current)
V
EXT
= 5V, V
WALLFB
= 1.5V
400
500
mA
V
MAIN
PMOS Switch On-Resistance
Measured Between V
INT
and V
MAIN
Pins
0.4
V
MAIN
Turn-On Delay
After FB1 and V
INT
in Regulation
Battery Powered
V
BATT
= 2.4V
0.8
2
ms
USB or Wall Powered
V
EXT
= 5V, V
WALLFB
= 1.5V
1.5
2
ms
Hot Swap Output
HSO PMOS Switch On-Resistance
Measured Between V
INT
and HSO Pins
0.8
HSO PMOS Switch Current Limit
V
INT
= 3.3V, V
HSO
= 2.5V
90
120
mA
HSO Turn-On Delay
After FB1 and V
INT
in Regulation
Battery Powered
V
BATT
= 2.4V
0.5
1
ms
USB or Wall Powered
V
EXT
= 5V, V
WALLFB
= 1.5V
0.5
1
ms
V
MAX
Output
V
MAX
Output Voltage
V
MAX
Output Unloaded
Shutdown
V
PWRON
= 0V
V
BATT
V
Battery Powered
V
PWRON
= 2V, V
BATT
= 2.4V
3.3
V
USB/Wall Powered
V
PWRON
= 2V, V
EXT
= 5V, V
WALLFB
= 1.5V
5
V
Maximum V
MAX
Output Current
V
MAX
Output < 12.5% Below Nominal Value
1
mA
Core Output
FB1 Voltage
0.784
0.800
0.816
V
FB1 Voltage Line Regulation
V
BATT
= 1.8V to 3.2V
0.1
0.5
%/V
FB1 Pin Input Bias Current
V
FB1
= 0.8V
2
20
nA
Duty Cycle Range
Buck Switchers
0
100
%
SW1 PMOS Switch Current Limit
Battery Powered
V
BATT
= 2.4V
400
550
mA
Wall/USB Powered
V
EXT
= 5V
350
450
mA
SW1 Leakage Current
V
SW1
= 0V, V
EXT
= 5V or V
BATT
= 5V
0.1
1
A
SW1 PMOS Switch On-Resistance
I
SW1
= 150mA
Battery Powered
V
BATT
= 2.4V
0.5
Wall/USB Powered
V
EXT
= 5V, V
WALLFB
= 1.5V
0.5
SW1 NMOS Switch On-Resistance
I
SW1
= 150mA
Battery Powered
V
BATT
= 2.4V
0.4
Wall/USB Powered
V
EXT
= 5V, V
WALLFB
= 1.5V
0.4
4
LTC3456
3456f
ELECTRICAL CHARACTERISTICS
The
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25C.
V
BATT
= 2.4V, V
INT
= 3.3V, V
PWRON
= 2V, PWRKEY is open, V
USB
= 0V, V
WALLFB
= 0V, unless otherwise specified.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2: The LTC3456 is guaranteed to meet performance specifications
from 0C to 70C. Specifications over the 40C to 85C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3: Quiescent current is pulled from the V
INT
pin when neither USB
nor wall power is present. Multiply this value by V
INT
/V
BATT
to get the
equivalent input (battery) current.
Note 4: Quiescent current is pulled from the V
EXT
pin when either USB or
wall power is present.
Note 5: Specification is guaranteed by design and not 100% tested in
production.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
USB
USB Turn-On Voltage Threshold
Rising Edge
3.9
4
4.1
V
USB Turn-On Voltage Hysteresis
75
mV
USB PMOS Switch On-Resistance
V
USB
= 5V
0.5
USB Current Limit
V
USBHP
= 2V (500mA Mode), V
USB
= 5V
420
500
mA
V
USBHP
= 0V (100mA Mode), V
USB
= 5V
85
100
mA
SUSPEND Pin Threshold
V
USB
= 5V
0.3
0.8
1.2
V
USBHP Pin Threshold
V
USB
= 5V
0.3
0.8
1.2
V
SUSPEND Pin Pull-Down Current
V
USB
= 5V, V
SUSPEND
= 2V
2.5
A
USBHP Pin Pull-Down Current
V
USB
= 5V, V
USBHP
= 2V
2.5
A
USB Pin Bias Current (Suspend Mode)
V
USB
= 5V, V
SUSPEND
= 2V
100
150
A
AC Adapter
WALLFB Pin Threshold
Rising Edge
1.2
1.25
1.3
V
WALLFB Pin Hysteresis
20
mV
WALLFB Pin Input Bias Current
V
WALLFB
= 1.25V, V
EXT
= 5V
2
20
nA
V
EXT
UVLO Voltage
Rising Edge
3.9
4
4.1
V
V
EXT
UVLO Hysteresis
150
mV
EXT_PWR Pin Low Voltage
V
USB
> 4V and V
SUSPEND
= 0V or
0.25
0.5
V
WALLFB > 1.25V, I
EXT_PWR
= 1mA
Gain Block
AIN Pin Reference Voltage
0.78
0.800
0.83
V
AIN Pin Input Bias Current
V
AIN
= 0.8V
2
20
nA
AO Pin Low Voltage
V
AIN
= 0V, I
AO
= 1mA
0.25
0.5
V
Logic Inputs
PWRKEY Pin Input High Voltage
0.7V
MAX
V
PWRKEY Pin Input Low Voltage
0.3V
MAX
V
PWRKEY Pin Pull-Up Resistor to V
MAX
400
k
PBSTAT Pin Low Voltage
V
PWRKEY
= 0V, I
PBSTAT
= 100A
0.05
0.1
V
PWRON Pin Threshold
0.3
0.8
1.2
V
PWRON Pin Pull-Down Current
V
PWRON
= 2V
1
A
MODE Pin Threshold
0.3
0.8
1.2
V
MODE Pin Pull-Down Current
V
MODE
= 2V
1
A
RESET Pin Low Voltage
I
RESET
= 100A
0.05
0.1
V
RESET Pulse Duration
After V
FB1
and V
INT
in Regulation
262
ms
5
LTC3456
3456f
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Core Converter Efficiency
(Battery Powered)
Main Converter Efficiency
(Battery Powered)
Efficiency (USB Powered)
Oscillator Frequency
vs Battery Voltage
Oscillator Frequency
vs V
EXT
Voltage
Oscillator Frequency
vs Temperature
No Load Battery Supply Current
vs Battery Voltage
No Load Battery Supply Currrent
vs Temperature
Shutdown Current vs Temperature
LOAD CURRENT (mA)
1
60
EFFICIENCY (%)
80
100
10
100
1000
3456 G01
40
30
50
70
90
20
0
10
V
BATT
= 2.4V
V
CORE
= 1.8V
PWM MODE
Burst Mode
OPERATION
V
BATT
(V)
1.6
FREQUENCY (kHz)
1000
1100
3.2
3456 G04
900
800
2.0
2.4
2.8
1.8
2.2
2.6
3.0
1200
950
1050
850
1150
V
EXT
(V)
4
FREQUENCY (kHz)
1000
1100
5.5
3456 G05
900
800
4.5
5
4.25
4.75
5.25
1200
950
1050
850
1150
TEMPERATURE (C)
50
FREQUENCY (kHz)
1000
1100
125
3456 G06
900
800
0
50
25
25
100
75
1200
950
1050
850
1150
V
BATT
= 2.4V
V
BATT
(V)
1.6
BATTERY SUPPLY CURRENT (mA)
4
5
6
2.8
3456 G07
3
2
2
2.4
1.8
3
2.2
2.6
3.2
1
0
7
PWM MODE
Burst Mode OPERATION
FB1 = 1V
(CORE CONVERTER
NOT SWITCHING)
TEMPERATURE (C)
50
BATTERY SUPPLY CURRENT (mA)
3.5
25
3456 G08
2.0
1.0
25
0
50
0.5
0
4.0
3.0
2.5
1.5
75
100
125
PWM MODE
Burst Mode OPERATION
FB1 = 1V
(CORE CONVERTER
NOT SWITCHING)
TEMPERATURE (C)
50
25
0
SHUTDOWN CURRENT (
A)
2
5
0
50
75
3456 G09
1
4
3
25
100
125
V
BATT
= 2.4V
LOAD CURRENT (mA)
1
60
EFFICIENCY (%)
80
100
10
100
1000
3456 G02
40
30
50
70
90
20
0
10
V
BATT
= 2.4V
V
MAIN
= 3.3V
PWM MODE
Burst Mode
OPERATION
LOAD CURRENT (mA)
1
60
EFFICIENCY (%)
80
100
10
100
1000
3456 G02
40
30
50
70
90
20
0
10
V
USB
= 5V
V
USBHP
= 2V
1.8V OUTPUT
3.3V OUTPUT
T
A
= 25C unless otherwise specified.
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