LTC3456
2-Cell, Multi-Output
DC/DC Converter with
USB Power Manager
FEATURES
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DESCRIPTIO
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
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.
, 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.
APPLICATIO S
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GPS Portable Navigators
MP3 Players
Digital Cameras
Handheld Computers
TYPICAL APPLICATIO
2 AA
CELLS
+
4.7µF
L2
4.7µH
100k
AIN
80.6k
AO
V
BATT
L3
10µH
SW2_BK
V
INT
V
MAIN
22µF
V
INT
3.3V
SW2_BST
MAIN OUTPUT
3.3V
1µF 150mA
Hot Swap OUTPUT
3.3V
1µF 50mA
CORE OUTPUT
1.8V
10µF 200mA
220pF
4.7µF
1Ω
SUSPEND
USB
LTC3456
SW1
L1
10µH
EFFICIENCY (%)
USB POWER
(4.35V TO 5.5V)
USB
CONTROLLER
USBHP
HSO
1k
AC WALL
ADAPTER
(5V
±10%)
EXT_PWR
V
EXT
4.7µF
1Ω
WALLFB
4.32k
ON/OFF
PWRKEY
V
MAX
11.3k
10µF
FB1
100k
80.6k
V
MAX
(POWERS
1µF REAL-TIME CLOCK)
PBSTAT RESET MODE PWRON PGND AGND
µP
3456 TA01
U
Efficiency and Power Loss
vs Load Current
(Battery Powered)
100
V
BATT
= 2.4V
90 MODE = 0V
80
70
60
50
40
30
20
10
0
1
10
100
LOAD CURRENT (mA)
POWER LOSS
1.8V
OUTPUT
3.3V
OUTPUT
EFFICIENCY
3.3V
OUTPUT
150
250
200
U
U
POWER LOSS (mW)
100
1.8V
OUTPUT
50
0
1000
3456 TA01b
3456fa
1
LTC3456
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
EXT_PWR
WALLFB
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 .......................................... 125°C
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 125°C
24 23 22 21 20 19
AIN 1
AO 2
AGND 3
V
BATT
4
SW1 5
PGND 6
7
8
9 10 11 12
25
18 SUSPEND
17 HSO
16 V
MAIN
15 V
INT
14 SW2_BST
13 SW2_BK
PWRKEY
PBSTAT
PWRON
RESET
MODE
FB1
ORDER PART
NUMBER
LTC3456EUF
USBHP
USB
V
MAX
V
EXT
UF PART
MARKING
3456
UF PACKAGE
24-LEAD (4mm
×
4mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 37°C/ W,
θ
JC
= 2°C/ W
EXPOSED PAD (PIN 25) IS PGND
MUST BE SOLDERED TO PCB
Order Options
Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
V
BATT
= 2.4V, V
INT
= 3.3V, V
PWRON
= 2V, PWRKEY is open, V
USB
= 0V, V
WALLFB
= 0V, unless otherwise specified.
PARAMETER
Battery Voltage Range
Quiescent Current (Battery Powered)
Burst Mode
®
Operation
PWM Operation
Shutdown
V
BATT
Pin Current (Wall Powered)
V
BATT
Pin Current (USB Powered)
Switching Frequency
Battery Powered
USB or Wall Powered
Main Output
V
INT
Voltage Regulation
V
INT
Voltage Line Regulation
Max Duty Cycle
Switch Leakage (Battery Powered)
SW2_BST PMOS Switch
SW2_BST NMOS Switch
Switch On-Resistance (Battery Powered)
SW2_BST PMOS Switch
SW2_BST NMOS Switch
Burst Mode is a registered trademark of Linear Technology
3456fa
CONDITIONS
(Note 3)
V
MODE
= 2V, V
FB1
= 1V, V
INT
= 3.4V
V
MODE
= 0V, V
FB1
= 1V, V
INT
= 3.4V
V
PWRON
= 0V, V
INT
= 0V
V
WALLFB
= 1.5V, V
EXT
= 5V (Note 4)
V
USB
= 5V, V
EXT
= 5V (Note 4)
V
BATT
= 2.4V
V
EXT
= 5V, V
WALLFB
= 1.5V
●
MIN
1.8
TYP
MAX
3.2
UNITS
V
µA
µA
µA
µA
µA
MHz
MHz
V
%/V
%
180
380
0.1
1
1
0.8
0.8
3.22
80
1
1
3.3
0.1
87
0.1
0.1
0.8
0.5
250
450
1
2
2
1.2
1.2
3.38
0.5
V
BATT
= 1.8V to 3.2V
V
PWRON
= 0V
V
SW2_BST
= 0V
V
SW2_BST
= 3.3V
I
SW2_BST
= 150mA
I
SW2_BST
= –150mA
●
●
1
1
2
U
µA
µA
Ω
Ω
W
U
U
W W
W
LTC3456
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
V
BATT
= 2.4V, V
INT
= 3.3V, V
PWRON
= 2V, PWRKEY is open, V
USB
= 0V, V
WALLFB
= 0V, unless otherwise specified.
PARAMETER
Switch Leakage (USB/Wall Powered)
SW2_BK PMOS Switch
SW2_BK NMOS Switch
Switch On-Resistance (USB/Wall Powered)
SW2_BK PMOS Switch
SW2_BK NMOS Switch
Switch Current Limit
Battery Powered (SW2_BST NMOS Current)
Wall/USB Powered (SW2_BK PMOS Current)
V
MAIN
PMOS Switch On-Resistance
V
MAIN
Turn-On Delay
Battery Powered
USB or Wall Powered
Hot Swap Output
HSO PMOS Switch On-Resistance
HSO PMOS Switch Current Limit
HSO Turn-On Delay
Battery Powered
USB or Wall Powered
V
MAX
Output
V
MAX
Output Voltage
Shutdown
Battery Powered
USB/Wall Powered
Maximum V
MAX
Output Current
Core Output
FB1 Voltage
FB1 Voltage Line Regulation
FB1 Pin Input Bias Current
Duty Cycle Range
SW1 PMOS Switch Current Limit
Battery Powered
Wall/USB Powered
SW1 Leakage Current
SW1 PMOS Switch On-Resistance
Battery Powered
Wall/USB Powered
SW1 NMOS Switch On-Resistance
Battery Powered
Wall/USB Powered
V
BATT
= 1.8V to 3.2V
V
FB1
= 0.8V
Buck Switchers
V
BATT
= 2.4V
V
EXT
= 5V
V
SW1
= 0V, V
EXT
= 5V or V
BATT
= 5V
I
SW1
= 150mA
V
BATT
= 2.4V
V
EXT
= 5V, V
WALLFB
= 1.5V
I
SW1
= –150mA
V
BATT
= 2.4V
V
EXT
= 5V, V
WALLFB
= 1.5V
●
●
●
●
CONDITIONS
V
EXT
= 5V, V
WALLFB
= 1.5V, V
PWRON
= 0V
V
SW2_BK
= 0V
V
SW2_BK
= 5V
V
EXT
= 5V, V
WALLFB
= 1.5V
I
SW2_BK
= 150mA
I
SW2_BK
= –150mA
V
BATT
= 2.4V
V
EXT
= 5V, V
WALLFB
= 1.5V
Measured Between V
INT
and V
MAIN
Pins
After FB1 and V
INT
in Regulation
V
BATT
= 2.4V
V
EXT
= 5V, V
WALLFB
= 1.5V
Measured Between V
INT
and HSO Pins
V
INT
= 3.3V, V
HSO
= 2.5V
After FB1 and V
INT
in Regulation
V
BATT
= 2.4V
V
EXT
= 5V, V
WALLFB
= 1.5V
V
MAX
Output Unloaded
V
PWRON
= 0V
V
PWRON
= 2V, V
BATT
= 2.4V
V
PWRON
= 2V, V
EXT
= 5V, V
WALLFB
= 1.5V
V
MAX
Output < 12.5% Below Nominal Value
●
●
●
●
●
MIN
TYP
0.1
0.1
0.9
0.4
MAX
1
1
UNITS
µA
µA
Ω
Ω
mA
mA
Ω
700
400
900
500
0.4
0.8
1.5
0.8
2
2
ms
ms
Ω
mA
90
120
0.5
0.5
1
1
ms
ms
V
BATT
3.3
5
1
0.784
0.800
0.1
±2
0
400
350
550
450
0.1
0.5
0.5
0.4
0.4
1
0.816
0.5
±20
100
V
V
V
mA
V
%/V
nA
%
mA
mA
µA
Ω
Ω
Ω
Ω
3456fa
3
LTC3456
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
V
BATT
= 2.4V, V
INT
= 3.3V, V
PWRON
= 2V, PWRKEY is open, V
USB
= 0V, V
WALLFB
= 0V, unless otherwise specified.
PARAMETER
USB
USB Turn-On Voltage Threshold
USB Turn-On Voltage Hysteresis
USB PMOS Switch On-Resistance
USB Current Limit
SUSPEND Pin Threshold
USBHP Pin Threshold
SUSPEND Pin Pull-Down Current
USBHP Pin Pull-Down Current
USB Pin Bias Current (Suspend Mode)
AC Adapter
WALLFB Pin Threshold
WALLFB Pin Hysteresis
WALLFB Pin Input Bias Current
V
EXT
UVLO Voltage
V
EXT
UVLO Hysteresis
EXT_PWR Pin Low Voltage
Gain Block
AIN Pin Reference Voltage
AIN Pin Input Bias Current
AO Pin Low Voltage
Logic Inputs
PWRKEY Pin Input High Voltage
PWRKEY Pin Input Low Voltage
PWRKEY Pin Pull-Up Resistor to V
MAX
PBSTAT Pin Low Voltage
PWRON Pin Threshold
PWRON Pin Pull-Down Current
MODE Pin Threshold
MODE Pin Pull-Down Current
RESET Pin Low Voltage
RESET Pulse Duration
V
MODE
= 2V
I
RESET
= 100µA
After V
FB1
and V
INT
in Regulation
V
PWRON
= 2V
0.3
V
PWRKEY
= 0V, I
PBSTAT
= 100µA
0.3
400
0.05
0.8
1
0.8
1
0.05
262
0.1
1.2
0.1
1.2
0.7V
MAX
0.3V
MAX
V
V
kΩ
V
V
µA
V
µA
V
ms
V
AIN
= 0.8V
V
AIN
= 0V, I
AO
= 1mA
●
CONDITIONS
Rising Edge
V
USB
= 5V
V
USBHP
= 2V (500mA Mode), V
USB
= 5V
V
USBHP
= 0V (100mA Mode), V
USB
= 5V
V
USB
= 5V
V
USB
= 5V
V
USB
= 5V, V
SUSPEND
= 2V
V
USB
= 5V, V
USBHP
= 2V
V
USB
= 5V, V
SUSPEND
= 2V
Rising Edge
V
WALLFB
= 1.25V, V
EXT
= 5V
Rising Edge
V
USB
> 4V and V
SUSPEND
= 0V or
WALLFB > 1.25V, I
EXT_PWR
= 1mA
●
●
●
MIN
3.9
TYP
4
75
0.5
420
85
MAX
4.1
UNITS
V
mV
Ω
500
100
1.2
1.2
mA
mA
V
V
µA
µA
0.3
0.3
0.8
0.8
2.5
2.5
100
150
1.3
±20
4.1
0.5
µA
V
mV
nA
V
mV
V
1.2
1.25
20
±2
3.9
4
150
0.25
0.76
0.800
±2
0.25
0.84
±20
0.5
V
nA
V
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 0°C to 70°C. Specifications over the – 40°C to 85°C 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.
3456fa
4
LTC3456
TYPICAL PERFOR A CE CHARACTERISTICS
T
A
= 25°C unless otherwise specified.
Core Converter Efficiency
(Battery Powered)
100
90
80
100
90
80
EFFICIENCY (%)
EFFICIENCY (%)
EFFICIENCY (%)
70
60
50
40
30
20
10
0
1
V
BATT
= 2.4V
V
CORE
= 1.8V
PWM MODE
Burst Mode
OPERATION
1000
3456 G01
10
100
LOAD CURRENT (mA)
Oscillator Frequency
vs Battery Voltage
1200
1150
1100
FREQUENCY (kHz)
1200
1150
1100
FREQUENCY (kHz)
1050
1000
950
900
850
800
1.6
1.8
2.0
2.2 2.4 2.6
V
BATT
(V)
2.8
3.0
3.2
1050
1000
950
900
850
800
4
4.25
4.5
4.75
V
EXT
(V)
5
5.25
5.5
FREQUENCY (kHz)
No Load Battery Supply Current
vs Battery Voltage
7
BATTERY SUPPLY CURRENT (mA)
BATTERY SUPPLY CURRENT (mA)
6
5
4
3.0
2.5
2.0
1.5
1.0
0.5
0
– 50 – 25
Burst Mode OPERATION
FB1 = 1V
(CORE CONVERTER
NOT SWITCHING)
SHUTDOWN CURRENT (µA)
FB1 = 1V
(CORE CONVERTER
NOT SWITCHING)
PWM MODE
3
2
1
Burst Mode OPERATION
0
1.6
1.8
2
2.2
2.4
2.6
2.8
3
3.2
V
BATT
(V)
3456 G07
U W
3456 G04
Main Converter Efficiency
(Battery Powered)
100
90
80
70
60
50
40
30
PWM MODE
Burst Mode
OPERATION
1000
3456 G02
Efficiency (USB Powered)
V
USB
= 5V
V
USBHP
= 2V
70
60
50
40
30
20
10
0
1
V
BATT
= 2.4V
V
MAIN
= 3.3V
20
10
0
1
1.8V OUTPUT
3.3V OUTPUT
10
100
LOAD CURRENT (mA)
1000
3456 G02
10
100
LOAD CURRENT (mA)
Oscillator Frequency
vs V
EXT
Voltage
1200
1150
1100
1050
1000
950
900
850
Oscillator Frequency
vs Temperature
V
BATT
= 2.4V
800
–50
–25
75
50
25
0
TEMPERATURE (°C)
100
125
3456 G05
3456 G06
No Load Battery Supply Currrent
vs Temperature
4.0
3.5
PWM MODE
Shutdown Current vs Temperature
5
V
BATT
= 2.4V
4
3
2
1
0
50
75
25
TEMPERATURE (°C)
100
125
0
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
125
3456 G08
3456 G09
3456fa
5
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