LINER LTC3456 2-cell, multi-output dc/dc converter with usb power manager Datasheet

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
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LTC3456
W W
W
AXI U
U
ABSOLUTE
RATI GS
U
U
W
PACKAGE/ORDER I FOR ATIO
(Note 1)
VBATT, VMAX Voltages ................................. – 0.3V to 6V
VINT, VMAIN, VEXT, 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
ORDER PART
NUMBER
PWRKEY
PBSTAT
PWRON
MODE
RESET
FB1
TOP VIEW
24 23 22 21 20 19
AIN 1
18 SUSPEND
AO 2
17 HSO
AGND 3
16 VMAIN
25
VBATT 4
LTC3456EUF
15 VINT
SW1 5
14 SW2_BST
PGND 6
VEXT
UF PART
MARKING
USBHP
WALLFB
VMAX
9 10 11 12
USB
8
EXT_PWR
13 SW2_BK
7
3456
UF PACKAGE
24-LEAD (4mm × 4mm) PLASTIC QFN
TJMAX = 125°C, θJA = 37°C/ W, θJC = 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 TA = 25°C.
VBATT = 2.4V, VINT = 3.3V, VPWRON = 2V, PWRKEY is open, VUSB = 0V, VWALLFB = 0V, unless otherwise specified.
PARAMETER
CONDITIONS
MIN
Battery Voltage Range
Quiescent Current (Battery Powered)
Burst Mode® Operation
PWM Operation
Shutdown
TYP
MAX
UNITS
3.2
V
180
380
0.1
250
450
1
µA
µA
µA
1.8
(Note 3)
VMODE = 2V, VFB1 = 1V, VINT = 3.4V
VMODE = 0V, VFB1 = 1V, VINT = 3.4V
VPWRON = 0V, VINT = 0V
VBATT Pin Current (Wall Powered)
VWALLFB = 1.5V, VEXT = 5V (Note 4)
1
2
µA
VBATT Pin Current (USB Powered)
VUSB = 5V, VEXT = 5V (Note 4)
1
2
µA
Switching Frequency
Battery Powered
USB or Wall Powered
VBATT = 2.4V
VEXT = 5V, VWALLFB = 1.5V
1
1
1.2
1.2
3.3
3.38
V
0.1
0.5
%/V
0.8
0.8
MHz
MHz
Main Output
●
VINT Voltage Regulation
VINT Voltage Line Regulation
VBATT = 1.8V to 3.2V
●
Max Duty Cycle
3.22
●
80
87
Switch Leakage (Battery Powered)
SW2_BST PMOS Switch
SW2_BST NMOS Switch
VPWRON = 0V
VSW2_BST = 0V
VSW2_BST = 3.3V
0.1
0.1
Switch On-Resistance (Battery Powered)
SW2_BST PMOS Switch
SW2_BST NMOS Switch
ISW2_BST = 150mA
ISW2_BST = –150mA
0.8
0.5
%
1
1
µA
µA
Ω
Ω
Burst Mode is a registered trademark of Linear Technology
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LTC3456
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
VBATT = 2.4V, VINT = 3.3V, VPWRON = 2V, PWRKEY is open, VUSB = 0V, VWALLFB = 0V, unless otherwise specified.
PARAMETER
CONDITIONS
Switch Leakage (USB/Wall Powered)
SW2_BK PMOS Switch
SW2_BK NMOS Switch
MIN
TYP
MAX
VEXT = 5V, VWALLFB = 1.5V, VPWRON = 0V
VSW2_BK = 0V
VSW2_BK = 5V
0.1
0.1
1
1
Switch On-Resistance (USB/Wall Powered)
SW2_BK PMOS Switch
SW2_BK NMOS Switch
VEXT = 5V, VWALLFB = 1.5V
ISW2_BK = 150mA
ISW2_BK = –150mA
0.9
0.4
Ω
Ω
Switch Current Limit
Battery Powered (SW2_BST NMOS Current)
Wall/USB Powered (SW2_BK PMOS Current)
VBATT = 2.4V
VEXT = 5V, VWALLFB = 1.5V
900
500
mA
mA
VMAIN PMOS Switch On-Resistance
Measured Between VINT and VMAIN Pins
0.4
Ω
VMAIN Turn-On Delay
Battery Powered
USB or Wall Powered
After FB1 and VINT in Regulation
VBATT = 2.4V
VEXT = 5V, VWALLFB = 1.5V
700
400
●
●
0.8
1.5
2
2
UNITS
µA
µA
ms
ms
Hot Swap Output
HSO PMOS Switch On-Resistance
Measured Between VINT and HSO Pins
HSO PMOS Switch Current Limit
VINT = 3.3V, VHSO = 2.5V
HSO Turn-On Delay
Battery Powered
USB or Wall Powered
After FB1 and VINT in Regulation
VBATT = 2.4V
VEXT = 5V, VWALLFB = 1.5V
90
●
●
0.8
Ω
120
mA
0.5
0.5
1
1
ms
ms
VMAX Output
VMAX Output Voltage
Shutdown
Battery Powered
USB/Wall Powered
VMAX Output Unloaded
VPWRON = 0V
VPWRON = 2V, VBATT = 2.4V
VPWRON = 2V, VEXT = 5V, VWALLFB = 1.5V
Maximum VMAX Output Current
VMAX Output < 12.5% Below Nominal Value
VBATT
3.3
5
●
1
●
0.784
V
V
V
mA
Core Output
FB1 Voltage
0.800
0.816
V
FB1 Voltage Line Regulation
VBATT = 1.8V to 3.2V
●
0.1
0.5
%/V
FB1 Pin Input Bias Current
VFB1 = 0.8V
●
±2
±20
nA
Duty Cycle Range
Buck Switchers
●
100
%
SW1 PMOS Switch Current Limit
Battery Powered
Wall/USB Powered
VBATT = 2.4V
VEXT = 5V
SW1 Leakage Current
VSW1 = 0V, VEXT = 5V or VBATT = 5V
0.1
SW1 PMOS Switch On-Resistance
Battery Powered
Wall/USB Powered
ISW1 = 150mA
VBATT = 2.4V
VEXT = 5V, VWALLFB = 1.5V
0.5
0.5
Ω
Ω
SW1 NMOS Switch On-Resistance
Battery Powered
Wall/USB Powered
ISW1 = –150mA
VBATT = 2.4V
VEXT = 5V, VWALLFB = 1.5V
0.4
0.4
Ω
Ω
0
400
350
550
450
mA
mA
1
µA
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LTC3456
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
VBATT = 2.4V, VINT = 3.3V, VPWRON = 2V, PWRKEY is open, VUSB = 0V, VWALLFB = 0V, unless otherwise specified.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Rising Edge
3.9
4
4.1
V
USB
USB Turn-On Voltage Threshold
USB Turn-On Voltage Hysteresis
75
USB PMOS Switch On-Resistance
VUSB = 5V
USB Current Limit
VUSBHP = 2V (500mA Mode), VUSB = 5V
VUSBHP = 0V (100mA Mode), VUSB = 5V
SUSPEND Pin Threshold
VUSB = 5V
0.3
USBHP Pin Threshold
VUSB = 5V
0.3
SUSPEND Pin Pull-Down Current
VUSB = 5V, VSUSPEND = 2V
mV
Ω
0.5
●
420
85
500
100
mA
mA
0.8
1.2
V
0.8
1.2
V
µA
2.5
µA
USBHP Pin Pull-Down Current
VUSB = 5V, VUSBHP = 2V
2.5
USB Pin Bias Current (Suspend Mode)
VUSB = 5V, VSUSPEND = 2V
100
150
1.25
1.3
µA
AC Adapter
WALLFB Pin Threshold
●
Rising Edge
1.2
WALLFB Pin Hysteresis
20
WALLFB Pin Input Bias Current
VWALLFB = 1.25V, VEXT = 5V
VEXT UVLO Voltage
Rising Edge
●
3.9
VEXT UVLO Hysteresis
EXT_PWR Pin Low Voltage
±2
±20
4
4.1
150
VUSB > 4V and VSUSPEND = 0V or
WALLFB > 1.25V, IEXT_PWR = 1mA
V
mV
nA
V
mV
0.25
0.5
V
0.800
0.84
V
±2
±20
nA
0.25
0.5
V
Gain Block
AIN Pin Reference Voltage
0.76
●
AIN Pin Input Bias Current
VAIN = 0.8V
AO Pin Low Voltage
VAIN = 0V, IAO = 1mA
Logic Inputs
PWRKEY Pin Input High Voltage
0.7VMAX
V
PWRKEY Pin Input Low Voltage
0.3VMAX
PWRKEY Pin Pull-Up Resistor to VMAX
PBSTAT Pin Low Voltage
400
VPWRKEY = 0V, IPBSTAT = 100µA
PWRON Pin Threshold
PWRON Pin Pull-Down Current
0.3
VPWRON = 2V
0.05
0.1
V
0.8
1.2
V
0.3
0.8
MODE Pin Pull-Down Current
VMODE = 2V
RESET Pin Low Voltage
IRESET = 100µA
0.05
RESET Pulse Duration
After VFB1 and VINT in Regulation
262
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.
µA
1
MODE Pin Threshold
V
kΩ
1.2
V
µA
1
0.1
V
ms
Note 3: Quiescent current is pulled from the VINT pin when neither USB
nor wall power is present. Multiply this value by VINT/VBATT to get the
equivalent input (battery) current.
Note 4: Quiescent current is pulled from the VEXT pin when either USB or
wall power is present.
Note 5: Specification is guaranteed by design and not 100% tested in
production.
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LTC3456
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TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise specified.
Main Converter Efficiency
(Battery Powered)
100
100
90
90
90
80
80
70
70
60
50
40
EFFICIENCY (%)
80
70
60
50
40
30
30
20
20
0
PWM MODE
Burst Mode
OPERATION
10
100
LOAD CURRENT (mA)
1
0
1000
PWM MODE
Burst Mode
OPERATION
VBATT = 2.4V
VMAIN = 3.3V
10
10
100
LOAD CURRENT (mA)
1
3456 G01
0
1000
Oscillator Frequency
vs Temperature
1150
1150
1150
1100
1100
1100
FREQUENCY (kHz)
1200
FREQUENCY (kHz)
1200
950
1050
1000
950
1000
950
900
900
850
850
850
1.8
2.0
2.2 2.4 2.6
VBATT (V)
2.8
3.0
800
3.2
4
4.25
4.5
4.75
VEXT (V)
5
3456 G04
800
–50
5.5
PWM MODE
3
2
1
Burst Mode OPERATION
1.8
2
2.2
2.4
2.6
2.8
3
3.2
VBATT (V)
3456 G07
3.0
2.5
FB1 = 1V
(CORE CONVERTER
NOT SWITCHING)
2.0
1.5
1.0
0.5
0
– 50 – 25
125
VBATT = 2.4V
PWM MODE
Burst Mode OPERATION
0
50
75
25
TEMPERATURE (°C)
100
125
3456 G08
SHUTDOWN CURRENT (µA)
4
BATTERY SUPPLY CURRENT (mA)
5
3.5
100
Shutdown Current vs Temperature
5
4.0
FB1 = 1V
(CORE CONVERTER
NOT SWITCHING)
75
50
25
0
TEMPERATURE (°C)
3456 G06
No Load Battery Supply Currrent
vs Temperature
7
6
–25
3456 G05
No Load Battery Supply Current
vs Battery Voltage
0
1.6
5.25
VBATT = 2.4V
1050
900
800
1.6
1000
3456 G02
1200
1000
10
100
LOAD CURRENT (mA)
1
Oscillator Frequency
vs VEXT Voltage
1050
1.8V OUTPUT
3.3V OUTPUT
10
3456 G02
Oscillator Frequency
vs Battery Voltage
FREQUENCY (kHz)
50
40
30
VBATT = 2.4V
VCORE = 1.8V
VUSB = 5V
VUSBHP = 2V
60
20
10
BATTERY SUPPLY CURRENT (mA)
Efficiency (USB Powered)
100
EFFICIENCY (%)
EFFICIENCY (%)
Core Converter Efficiency
(Battery Powered)
4
3
2
1
0
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
125
3456 G09
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LTC3456
U W
TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise specified.
VBATT Pin Current when USB or
Wall Powered
2.0
3
2
1
0
–50
–25
75
0
25
50
TEMPERATURE (°C)
100
800
FB1 = 1V
CORE CONVERTER
NOT SWITCHING
1.6
700
1.2
0.8
0.4
0
125
4
4.25
4.5
4.75
VEXT (V)
5
5.25
850
825
800
775
100
VEXT = 5V
550
525
500
475
450
700
0
50
75
25
TEMPERATURE (°C)
100
RESISTOR LOAD
VMAIN LOAD CURRENT (mA)
VINT LOAD CURRENT (mA)
100
2.80
100
75
50
3.00 3.20
!"#$ /$
0
50
75
25
TEMPERATURE (°C)
100
3456 G15
600
L = 4.7µH
(BATTERY POWERED)
600
500
400
300
100
1.8
125
Maximum VCORE Load Current
Capability (Output 4% Below
Regulation)
L = 10µH
(BATTERY POWERED)
500
VCORE = 1.5V
VCORE = 1.8V
400
300
200
100
200
50
2.20 2.40 2.60
VBATT (V)
125
0
– 50 – 25
125
VCORE LOAD CURRENT (mA)
300
0
1.80 2.00
150
Maximum VMAIN Load Current
Capability (Output 4% Below
Regulation)
150
VBATT = 2.4V
3456 G14
VINT Load Current
vs Start-Up Battery Voltage
125
25
3456 G13
200
100
175
400
– 50 – 25
125
250
50
25
75
0
TEMPERATURE (°C)
Hot Swap (HSO) Current Limit
200
425
50
75
25
TEMPERATURE (°C)
400
3456 G12
HSO CURRENT LIMIT (mA)
875
VBATT = 2.4V
200
–50 –25
5.5
575
SW2_BK CURRENT LIMIT (mA)
SW2_BST CURRENT LIMIT (mA)
VBATT = 2.4V
925
0
500
SW2_BK Current Limit
600
900
VEXT = 5V
3456 G11
SW2_BST Current Limit
750
– 50 – 25
600
300
3456 G10
950
SW1 Current Limit
SW1 CURRENT LIMIT (mA)
VEXT = 5V
VEXT SUPPLY CURRENT (mA)
VBATT PIN CURRENT (µA)
4
No Load VEXT Suppy Current when
USB or Wall Powered
2
2.2
2.4 2.6
VBATT (V)
2.8
3
3.2
3456 G17
0
1.8
2
2.2
2.4 2.6
VBATT (V)
2.8
3
3.2
3456 G18
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LTC3456
U W
TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise specified.
Maximum VCORE Load Current
Capability (Output 4% Below
Regulation)
500
500
400
300
USB Undervoltage Lockout
4.10
L = 10µH
(USB/WALL POWERED)
4.05
400
USB VOTLAGE (V)
L = 10µH
(USB/WALL POWERED)
VMAIN LOAD CURRENT (mA)
VCORE LOAD CURRENT (mA)
600
Maximum VMAIN Load Current
Capability (Output 4% Below
Regulation)
300
RISING
4.00
3.95
FALLING
3.90
200
3.85
100
200
4
4.25
4.5
4.75
VEXT (V)
5
5.25
4
5.5
4.25
4.5
4.75
VEXT (V)
5
5.25
125
WALLFB Trip Point
1.28
0.820
450
0.815
USBHP = 2V
400
0.805
AIN (V)
300
250
200
WALLFB VOLTAGE (V)
0.810
350
VEXT = 5V
0.800
0.795
VBATT = 2.4V
150
0.790
USBHP = 0V
1.26
RISING
1.24
FALLING
1.22
0.785
50
VUSB = 5V
0
–50 –25
50
25
0
75
TEMPERATURE (°C)
100
125
0.780
– 50 – 25
0
50
75
25
TEMPERATURE (°C)
100
3456 G22
1.20
–50
125
–25
75
0
25
50
TEMPERATURE (°C)
4.50
3.5
VMAX Output Voltage
(USB/Wall Powered)
6
PWRON = 2V
3.0
VMAX OUTPUT CURRENT = 0.5mA
5
4.25
PWRON = 0V, 2V
2.5
4
FALLING
VMAX (V)
VMAX (V)
PWRON = 0V
RISING
125
3456 G24
VMAX Output Voltage
(Battery Powered)
4.00
100
3456 G23
VEXT Undervoltage Lockout
VEXT (V)
100
3456 G21
AIN Pin Reference Voltage
USB Current Limit
500
100
50
25
75
0
TEMPERATURE (°C)
3456 G20
3456 G19
USB CURRENT LIMIT (mA)
3.80
–50 –25
5.5
2.0
1.5
3
2
1.0
3.75
1
0.5
3.50
–50
–25
75
0
25
50
TEMPERATURE (°C)
100
125
3456 G25
VMAX OUTPUT CURRENT = 0.5mA
0
1.6 1.8 2 2.2 2.4 2.6 2.8
VBATT (V)
0
3
3.2
3456 G26
4
4.25
4.5
4.75
VEXT (V)
5
5.25
5.5
3456 G27
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LTC3456
U W
TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise specified.
Switching Waveforms
(Battery Powered)
Switching Waveforms
(Wall/USB Powered)
IL1
50mA/DIV
IL1
200mA/DIV
VSW1
5V/DIV
VSW1
5V/DIV
IL2
200mA/DIV
VSW2_BST
5V/DIV
IL3
100mA/DIV
VSW2_BK
5V/DIV
VBATT = 2.4V
VPWRON = 2V
ICORE = 100mA
IMAIN = 100mA
0.5µs/DIV
VEXT = 5V
VPWRON = 2V
ICORE = 100mA
IMAIN = 100mA
3456 G28
0.5µs/DIV
3456 G29
USB ↔ Battery Switchover
(Core Converter Transient
Waveforms)
USB ↔ Battery Switchover
(Main Converter Transient
Waveforms)
VCORE
100mV/DIV
(AC COUPLED)
VMAIN
100mV/DIV
(AC COUPLED)
IL2
200mA/DIV
IL1
100mA/DIV
IL3
100mA/DIV
SUSPEND
5V/DIV
SUSPEND
5V/DIV
VUSB = 5V
VUSBHP = 5V
VBATT = 2.4V
ICORE = 100mA
IMAIN = 100mA
200µs/DIV
VUSB = 5V
VUSBHP = 5V
VBATT = 2.4V
ICORE = 100mA
IMAIN = 100mA
3456 G30
200µs/DIV
3456 G31
Power Supply Sequencing
(Battery Powered)
Power Up/Power Down
Sequencing (Battery Powered)
VPWRON
5V/DIV
VMAIN
5V/DIV
VPWRON
5V/DIV
VCORE
2V/DIV
VCORE
2V/DIV
RESET
5V/DIV
VMAIN
5V/DIV
VINT
5V/DIV
VBATT = 2.4V
ICORE = 10mA
IMAIN = 10mA
100ms/DIV
3456 G32
VBATT = 2.4V
ICORE = 5mA
200µs/DIV
3456 G33
3456fa
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LTC3456
U
U
U
PI FU CTIO S
AIN (Pin 1): Low-Battery Detector Input Pin. The detector
compares the voltage on this pin to an 800mV reference.
Connect the resistor divider tap to this pin to set the lowbattery trip point.
AO (Pin 2): Open-Drain Digital Output. This open-drain
logic output is pulled to GND whenever the AIN pin voltage
falls lower than 0.8V.
AGND (Pin 3): Analog Ground. All resistor dividers should
be connected to this pin.
VBATT (Pin 4): Battery Input Supply. The input voltage at this
pin can range from 1.8V to 3.2V. Must be locally bypassed
with a 1µF (or greater) X5R or X7R type ceramic capacitor.
SW1 (Pin 5): Switch Pin for Core Regulator. Connect the
inductor between SW1 and the output capacitor. Keep
these PCB trace lengths as short and wide as possible to
reduce EMI.
PGND (Pin 6): Power Ground. This is the ground pin for all
internal drivers and switches. Provide a short PCB path
between PGND and PCB system ground.
WALLFB (Pin 7): Wall Feedback Pin. This pin receives the
feedback voltage from an external resistor divider across
the AC wall adapter input. When the pin voltage is higher
than 1.25V, the chip is powered from the VEXT pin and the
USB switch is turned off. Ensure that the resistor ratio is
set so that the wall adapter voltage (min) is still high
enough to make VEXT > 4V. Connect to ground if not used.
EXT_PWR (Pin 8): External Power Good Pin. This opendrain logic output is pulled to GND whenever the WALLFB
pin is pulled higher than 1.25V or the USB pin voltage is
greater than 4V and SUSPEND is low. Essentially this pin
is pulled low whenever the AC adapter or the USB power
is present. When pulled low, this pin is capable of sinking
5mA suitable for driving an external LED.
VEXT (Pin 9): External Power Pin. This pin is connected to
the USB pin via an internal 0.5Ω (typ) PMOS switch. The
AC wall adapter can be connected to this pin through a
Schottky diode. An onboard voltage detector prevents the
IC from drawing power from this pin until the pin voltage
rises above 4V. The voltage detector for VEXT has built-in
150mV hysteresis. Connect a 10µF X5R or X7R type
ceramic capacitor from this pin to ground.
USB (Pin 10): USB Input Supply. Input current into this pin
is limited to either 100mA or 500mA based on the state of
the USBHP pin. When the USB pin voltage is greater than
4V and SUSPEND is low, and WALLFB is less than 1.25V,
USB is connected to the VEXT pin via an internal 0.5Ω
current limited PMOS Switch. Connect a 4.7µF (X5R or
X7R type) ceramic capacitor in series with a 1Ω resistor
from this pin to ground.
VMAX (Pin 11): Maximum Supply Voltage Pin. A special
internal PowerPathTM controller monitors the VBATT, VINT,
VEXT and USB voltages and passes the highest available
supply voltage to the VMAX pin. This pin is used to power
some of the internal circuitry of the IC. Connect a 1µF
bypass capacitor from this pin to ground. It can be used
to supply a maximum of 1mA output load. The VMAX
output voltage stays alive even when the IC is in shutdown.
USBHP (Pin 12): USB High Power Select Pin. This pin is
used to set the USB current limit. Pull high to select 500mA
current limit (High Power mode); low to select 100mA
current limit (Low Power mode). This pin has a weak pulldown current source to ensure that Low Power mode is in
effect during start-up.
SW2_BK (Pin 13): Switch Pin for Main Regulator (USB or
Wall Powered). Connect the inductor between SW2_BK
and the output voltage. Keep these PCB trace lengths as
short and wide as possible to reduce EMI.
SW2_BST (Pin 14): Switch Pin for Main Regulator (Battery Powered). Connect the inductor between SW2_BST
and VBATT. Keep these PCB trace lengths as short and wide
as possible to reduce EMI.
VINT (Pin 15): Internal Supply Voltage Pin. The VINT
voltage is regulated to 3.3V. This pin is used to power most
of the internal circuitry of the IC. Do not load this output.
Connect an output capacitor from this pin to ground.
VMAIN (Pin 16): Main Regulator Output Voltage. An internal 0.4Ω PMOS switch connects this pin to the VINT pin
0.8ms (typ) after the Core voltage comes into regulation.
This ensures that VMAIN will always power up after Core
output during start-up. Connect an output capacitor from
this pin to ground.
PowerPath is a trademark of Linear Technology Corporation.
3456fa
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LTC3456
U
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PI FU CTIO S
HSO (Pin 17): Hot Swap Output. An internal 0.8Ω current
limited PMOS switch connects this pin to the VINT pin
0.5ms after the core voltage comes into regulation. The
nominal voltage at this pin is 3.3V. It is short-circuit
protected and the current out of this pin is limited to
120mA (typ).
SUSPEND (Pin 18): USB Suspend Pin. Pull this pin high
to disable all USB functionality. The USB switch connected
between USB and VEXT behaves like a back-to-back diode
whenever SUSPEND is pulled high. In Suspend mode the
device limits the current drawn from the USB port to
100µA (typ).
PWRKEY (Pin 19): Power ON/OFF Key. Connecting this
pin to GND will turn on the IC. This pin is typically used with
a momentary-on pushbutton switch to turn on the LTC3456.
This pin must be held low until the PWRON pin is pulled
high (usually from a microprocessor) in order to keep the
IC turned on. This pin has a 400k pull-up resistor to VMAX.
PBSTAT (Pin 20): Power ON/OFF Key Status Pin. This
open-drain output pin indicates the state of the PWRKEY
pin to the microcontroller. The pin output follows the state
of the PWRKEY pin (PBSTAT goes low when PWRKEY is
pulled low).
PWRON (Pin 21): Power On Pin. When pulled high this
microprocessor controlled pin turns on the IC. This pin
has a weak 1µA pull-down current source.
MODE (Pin 22): Burst Mode Select Pin. Tie this pin high to
allow automatic Burst Mode operation. Burst Mode operation will provide superior efficiency when any of the
outputs are operating with very low output currents. Tie
this pin low to force PWM operation under all load current
conditions. The device operates in forced PWM mode
when powered from USB or wall input (irrespective of the
state of the MODE pin). Furthermore, at initial power-up,
the device operates in forced PWM mode during the
262ms internal delay timeout. This pin has a weak 1µA
pull-down current source.
RESET (Pin 23): Fault Indicator Output Pin. This opendrain output is active both at power-up and power-down.
RESET is held low at initial power up. When both the Core
and Main outputs come into regulation, an internal reset
delay timer is activated. RESET is released at the end of the
262ms timeout. If either Main or Core outputs fall out of
regulation during normal operation, RESET is pulled low.
Also, RESET is pulled low at power-off to prevent spurious
turn-on of the microprocessor.
FB1 (Pin 24): Feedback Pin for the Core Regulator. The
regulator drives the voltage at this pin to 0.8V. Connect the
resistor divider tap to this pin. The output voltage of the
core regulator can be adjusted from 0.8V to VBATT(MIN).
Exposed Pad (Pin 25): The Exposed Pad must be soldered
to the PCB system ground.
3456fa
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LTC3456
W
BLOCK DIAGRA
USB
VEXT
VINT
VBATT
R
USB
–
+VOS
4V
4.7µF
+ –
1Ω
EN
USB
CONTROLLER
18
12
11.3k
AC
ADAPTER
7
SUSPEND
WALLFB
1.25V
4.32k
USB
CONTROL
LOGIC
USBHP
4V
+
–
PowerPath
CONTROLLER
VMAX
1µF
PWRKEY
VEXT_RDY
PBSTAT
USB_RDY
+
–
PWRON
START-UP
LOGIC
MODE
D1
RESET
1k
8
EXT_PWR
TURN-ON
SWITCHERS
D2
VEXT
9
VEXT
HSO
80.6k
1
100k
4
VBATT
R
AO
–
+
2
0.8V
19
20
21
22
23
262ms
TIMER
10µF
AO
11
VEXT
AIN
1µF
–
VOS
+
PSWITCH
VMAIN
VBATT
VMAIN
16
1µF
200k
L1
10µH
VCORE
5
SW1
625k
VINT
SW2_BST
DRV
100k
24
10µF
HSO
17
4.7µF
220pF
MICROCONTROLLER
10
USB
0.8V
FB1
80.6k
0.8V
–
+
–
+
VINT
15
L2
4.7µH
22µF
VBATT
14
DRV
4.7µF
SW2_BK
L3
10µH
13
AGND 3
PGND 6
3456 F01
Figure 1. LTC3456 Block Diagram
3456fa
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LTC3456
U
OPERATIO
INTRODUCTION
OPERATING MODES
The LTC3456 is a complete system-level power supply IC
used to power GPS portable navigators and other portable
systems. It takes power from one of three sources: battery,
USB or wall adapter. The device provides an integrated
standard solution resulting in a reduced parts count and
higher efficiency.
The LTC3456 is powered from an AC wall adapter, USB or
battery, in that order of priority. It has onboard voltage
detectors to monitor the status of the wall adapter and USB
voltages. The unique control scheme of the LTC3456
allows seamless transition between battery, USB and wall
adapter input power sources.
The LTC3456 generates two separate power supplies: a
Core supply for the processor and a Main supply for the
peripheral circuitry. The Main supply is a fixed 3.3V output
and the Core supply voltage can be adjusted from 0.8V to
VBATT(MIN). In addition, the LTC3456 provides a Hot Swap
output which can be used for powering flash memory
cards. Both regulators utilize a 1MHz constant frequency
current mode architecture.
Battery Powered
The LTC3456 is designed to accept an input battery
voltage range from 1.8V to 3.2V. This range is ideal for
2-cell Alkaline, NiCd or NiMH designs. Figure 2 shows an
LTC3456 being powered from two AA cells.
When enabled, the internal supply voltage VINT (3.3V) is
generated via the boost regulator. VINT is used to power
the bandgap reference, drivers and other internal circuitry.
Core output (1.8V) comes up next via the buck regulator.
Main output and the Hot Swap output are powered up with
a delay after the core output is in regulation.
The device also incorporates a low-battery detector
(configurable as a low dropout regulator), USB power
manager and several protection features in a single package. The LTC3456’s control scheme allows 100% duty
cycle operation for the core output. It provides low dropout
operation when the core output is powered from the
battery, thereby extending battery life.
LTC3456
VBATT
2 AA CELLS
1.8V TO 3.2V
4
VBATT
BUCK
SW1
L1
10µH
5
+
10µF
L2
4.7µH
14
SW2_BST
BOOST
VINT
15
22µF
VMAIN
R
HSO
VINT
3.3V
1µF
MAIN OUTPUT
3.3V
150mA
1µF
Hot Swap OUTPUT
3.3V
50mA
16
17
–
+VOS
CORE OUTPUT
1.8V
200mA
3456 F02
Figure 2. Battery-Powered LTC3456
3456fa
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LTC3456
U
OPERATIO
AC Wall Adapter Powered
will draw all its power from the AC adapter via the VEXT pin.
The WALLFB voltage should always be kept below 2V.
The LTC3456 can be powered off the AC wall adapter as
shown in Figure 3. The wall adapter is connected to the
VEXT pin via the diode D1.
When enabled, the onboard voltage detector checks the
status of the VEXT voltage. If the VEXT pin voltage is greater
than 4V, the VINT, Core output, Main output and Hot Swap
outputs power-up in that sequence.
The status of the AC wall adapter power is monitored
through the WALLFB pin. The nominal voltage at this pin
is 1.25V. When the pin voltage is higher than 1.25V, the IC
4V
VEXT
9
–
+
LTC3456
L1
10µH
EN
VEXT
BUCK 1
SW1
5
10µF
10µF
BUCK 2
D1
SW2_BK
VINT
AC
ADAPTER
5V ±5%
WALL_RDY
11.3k
7
4.32k
L3
10µH
13
22µF
VINT
3.3V
15
1µF
MAIN OUTPUT
3.3V
150mA
1µF
Hot Swap OUTPUT
3.3V
50mA
16
+
–
VMAIN
CORE OUTPUT
1.8V
200mA
WALLFB
1.25V
R
HSO
17
–
+VOS
3456 F03
Figure 3. AC Adapter-Powered LTC3456
3456fa
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LTC3456
U
OPERATIO
USB Powered
Pulling the SUSPEND pin logic high disables all USB
functionality. The USB switch connected between USB
and VEXT behaves like a back-to-back diode whenever
SUSPEND is pulled high. In Suspend mode the device
limits the current drawn from the USB pin to 100µA (typ).
The LTC3456 is designed to be powered from the USB as
shown in Figure 4. The LTC3456 has an internal currentlimited 0.5Ω (typ) PMOS switch with preset 0.1A and 0.5A
current limits. The LTC3456 interfaces with the USB
controller bus via logic pins USBHP and SUSPEND.
The minimum voltage to a USB-powered device may drop
as low as 4.35V due to cable and connector drops. The
LTC3456 has an internal voltage monitor that checks the
USB supply voltage and cuts off the USB power if the USB
voltage falls below 4V. There is 75mV of hysteresis builtin the USB voltage monitor.
The USBHP pin is used to set the USB current limit to either
100mA or 500mA. This pin has a weak 2.5µA pull-down
current source to ensure that Low Power mode is in effect
during start-up. If the USBHP pin is held low, it limits the
input power drawn from the USB port. The USB port can
supply the Core output (1.8V at 200mA) effortlessly in Low
Power mode (USBHP = 0V). However, the loading on the
3.3V output must be held below 100mA (typ) when the
USB is in low power mode. If the loading on 3.3V output
is increased beyond 100mA (typ), the USB port is unable
to supply the load current and the LTC3456 will switch
between the battery and the USB port. This results in
undesirable switching noise and increased voltage ripple
at the 3.3V output.
4V
VEXT
9
–
+
When the IC is enabled, the USB pin is connected to the
VEXT pin via the PMOS switch. The VEXT pin gets charged
by the preset 0.1A or 0.5A current limit determined by the
state of the USBHP pin. As the VEXT pin voltage rises above
4V, the VINT, Core output, Main output and Hot Swap
outputs power-up in that sequence.
LTC3456
EN
VEXT
SW1
BUCK 1
L1
10µH
5
10µF
10µF
BUCK 2
500mA
100mA
USBHP
12
SUSPEND
18
USB
4.35V TO 5.5V
10
VINT
USBHP
VMAIN
SUSPEND
USB
4.7µF
1Ω
SW2_BK
4V
R
+
–
USB_RDY
HSO
L3
10µH
13
22µF
CORE OUTPUT
1.8V
200mA
VINT
3.3V
15
1µF
MAIN OUTPUT
3.3V
150mA
1µF
Hot Swap OUTPUT
3.3V
50mA
16
17
–
+VOS
3456 F04
Figure 4. USB-Powered LTC3456
3456fa
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LTC3456
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OPERATIO
MAIN REGULATOR
PWRON
5V/DIV
VINT Output
The main regulator produces a fixed 3.3V output from a
1.8V to 3.2V input (2-cell battery), USB port or AC adapter
input supply. The main regulator output, VINT, is used to
power most of the internal circuitry of the IC. It is the first
one to power-up. Connect a 22µF or higher X5R or X7R
type ceramic capacitor from this pin to ground.
The loading on this output should be limited to 20mA.
Refer to the Minimum Start-Up Battery Voltage vs
VINT Output Current graph in the Typical Performance
Characteristics.
When the IC is turned off, the VINT output voltage is
discharged to ground.
Output Disconnect and Inrush Limiting
The LTC3456 allows true output disconnect when powered off the battery (boost topology). It achieves this by
disconnecting the body diode of the synchronous PMOS
switch from the output. This allows the VINT to go to
ground during shutdown. Do not connect a Schottky diode
from SW2_BST to VINT; doing so will defeat the output
disconnect feature.
The LTC3456 also features inrush current limiting at
power-up (battery powered). Inrush current in boost
converters is important when powering from input sources
with high input impedance like alkaline cells. The LTC3456
incorporates an inrush current limiting scheme that regulates the inrush current to 600mA (typ) during power-up.
Figure 5 shows inrush current when the device is powered
up from the battery.
Short-Circuit Protection
The LTC3456 features short-circuit protection for the main
regulator output. When the main regulator is powered
from the USB or wall input, it operates in a buck topology.
VINT
2V/DIV
IL2
500mA/DIV
VBATT = 2.4V
IVINT = 10mA
100µs/DIV
3456 F05
Figure 5. Inrush Current at Power-Up (Battery Powered)
If the main regulator outputs (VINT or VMAIN) are shorted
to ground, the LTC3456 unique control scheme prevents
inductor current runaway.
When the device is powered from the battery, it operates
in a boost topology. Most boost converters do not allow their
outputs to be shorted to ground. However, the LTC3456
allows the output of its main regulator (VINT or VMAIN) to
be short-circuited due to its unique inrush current limiting.
In the event of a short-circuit, the input current is well
regulated.
VMAIN Output
The LTC3456 is designed to supply power to the microprocessor peripheral circuitry in a controlled manner. The
peripheral circuitry should be connected to the VMAIN
output.
VMAIN is connected to VINT via a 0.4Ω (typ) PMOS switch
0.8ms (typ) after the Core output comes into regulation.
This ensures that the peripheral circuitry always powers
up after the microprocessor.
The VMAIN output is discharged to ground through internal pull-down resistors at shutdown. This ensures that
the peripheral circuitry gets turned-off completely during
shutdown. Connect a 1µF (X5R or X7R) bypass capacitor
from this pin to ground.
3456fa
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LTC3456
U
OPERATIO
Hot Swap Output
CORE REGULATOR
The LTC3456 is designed to supply power to flash memory
cards. It has a built-in Hot Swap output, HSO, which allows
memory cards to be hot swapped into and out of the
system. The Hot Swap output features short-circuit and
reverse-voltage blocking protection. Connect a 1µF (X5R
or X7R) bypass capacitor from this pin to ground.
The core regulator produces a 0.8V to 1.8V adjustable
output from a 1.8V to 3.2V input (2-cell battery), USB port
or AC adapter supply. The core regulator utilizes a synchronous N-channel MOSFET, improving efficiency and eliminating the need for an external Schottky diode. The core
output voltage is measured at the FB1 pin through a resistive divider network. The nominal voltage at the FB1 pin is
0.8V. The divider can be adjusted to set the output voltage
level. The FB1 voltage should always be kept below 2V.
After the VINT and Core output voltages come into regulation, the HSO pin is connected to VINT via a 0.8Ω (typ) PMOS
switch after a delay of 0.5ms. The PMOS switch has a
120mA built-in current limit. When a flash memory card is
plugged into the system, the input bypass capacitors are
slowly charged up to 3.3V with the preset 120mA current
limit. Figure 6 shows the switching waveforms with Hot
Swap output short-circuited. As seen in the figure, the shortcircuited current out of the HSO pin is well regulated.
The LTC3456 also features reverse-voltage blocking capability for the HSO pin. In the event the HSO pin voltage rises
greater than 3.3V (VINT pin voltage), the internal PMOS
switch is turned off and behaves like a back-to-back diode.
During shutdown, the Hot Swap output is discharged to
ground via internal pull-down resistors.
VINT
100mV/DIV
(AC COUPLED)
The LTC3456 internal soft-start circuitry limits current
drawn at start-up. Soft-start is essential for input sources
with high input impedance like alkaline cells. Soft-start is
implemented by ramping up the current limit. At start-up,
the current limit is set to 25% and increased by 25% every
256µs. The final inductor current limit is reached after
1ms.
When the core regulator is turned off, the output voltage
VCORE is discharged to ground. This is accomplished by
pulling the switching node, SW1, to ground through the
internal pull-down resistors.
IL2
500mA/DIV
VHSO
5V/DIV
VINT
100mV/DIV
(AC COUPLED)
IL3
500mA/DIV
VHSO
5V/DIV
IHSO
200mA/DIV
IHSO
200mA/DIV
VBATT = 2.4V
VPWRON = 2V
2ms/DIV
3456 F06a
Figure 6a. Short-Circuit at the Hot Swap Output (Battery Powered)
VEXT = 5V
VPWRON = 2V
2ms/DIV
3456 F06b
Figure 6b. Short-Circuit at the Hot Swap Output
(Wall/USB Powered)
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LTC3456
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OPERATIO
The LTC3456 incorporates additional features like output
short-circuit protection and thermal regulation. When the
core regulator output (VCORE) is shorted to ground, the
LTC3456’s unique control scheme prevents inductor current runaway.
Dropout Operation
The LTC3456 is capable of operating at 100% duty cycle
when powered from the battery. If the input supply voltage
decreases to a value close to the output voltage, the core
regulator will run at 100% duty cycle. The output voltage
is then determined by the input voltage minus the voltage
drop across the PMOS switch and the inductor. When
running off the USB or the AC adapter, this situation never
arises (there is plenty of voltage headroom).
When the LTC3456 operates with low input supply voltage, say 1.8V (fully discharged two AA cells) the maximum
allowable output current gets reduced. Figure 7 shows the
reduction in the maximum output current as a function of
input voltage for various output voltages.
VCORE LOAD CURRENT (mA)
600
L = 10µH
(BATTERY POWERED)
500
VCORE = 1.5V
VCORE = 1.8V
400
300
200
100
0
1.8
2
2.2
2.4 2.6
VBATT (V)
2.8
3
3.2
3456 G18
Figure 7. Maximum Output Current vs Battery Voltage
VMAX OUTPUT
A special internal PowerPath controller monitors the VBATT,
VINT, VEXT and USB voltages and passes the highest
available supply voltage to the VMAX pin. This pin is used
to power some of the internal circuitry of the IC. Connect
a 1µF bypass capacitor from this pin to ground. It can be
used to supply a maximum of 1mA output load.
The VMAX output voltage stays alive even when the IC is in
shutdown. During shutdown, the VMAX output will be the
highest of VBATT, VEXT and USB voltages. VMAX output can
be used to supply power to a critical block like the real-time
clock, which needs to stay alive even during shutdown.
POWER SEQUENCING
Power On/Off
The LTC3456 can turned on in two different ways:
• Pulling the PWRKEY pin low
• Pulling the PWRON pin high
Pulling the PWRKEY pin low is usually the first step in
turning on the LTC3456. When PWRKEY is pulled low, it
powers on the bandgap reference. Onboard voltage monitors check the status of the AC adapter and USB supply.
The IC is powered from either the AC adapter, USB or the
battery, in that order of preference. The VINT voltage
powers up, followed by the Core, Main and Hot Swap
outputs.
At initial power up, the RESET pin is held low. When the
Core output comes into regulation, the RESET timer is
started. After a 262ms timeout, the RESET pin is released.
This allows the microprocessor to turn on. The microprocessor in turn pulls PWRON high. After the PWRON pin is
pulled high, the PWRKEY pin can be released. There is a
400kΩ pull-up resistor on the PWRKEY pin.
The PWRKEY pin serves the dual purpose of turning on
and off the IC. During regular operation, if PWRKEY is
pressed low, the microprocessor detects this by monitoring the status of PBSTAT pin. The PBSTAT pin goes low
whenever the PWRKEY pin is pulled low. The microprocessor then goes into shutdown mode and pulls the
PWRON pin low. This results in powering off the LTC3456.
Figure 8 shows the device power-on/power-off sequence.
3456fa
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LTC3456
U
OPERATIO
PWRKEY
PWRKEY
PULLED LOW
PWRKEY
RELEASED
VCORE
RESET
262ms
TIMEOUT
PWRON
PBSTAT
3456 F08
POWER-ON SEQUENCE
POWER-OFF SEQUENCE
Figure 8. Power-On/Power-Off Sequence
RESET
The LTC3456 contains a RESET circuitry that is active
during both power-up and shutdown. The RESET pin is
held low during initial power-up. When both the VINT and
Core outputs come into regulation, a reset delay timer gets
activated. There is a full 262ms timeout before RESET is
released. During power-off mode RESET is pulled low.
This prevents the microprocessor from entering into any
spurious operating mode.
MODE
The LTC3456 has a user selectable MODE pin. When the
MODE pin is pulled logic high and the LTC3456 is battery
powered, the device will automatically enter into Burst
Mode operation under light load current situations. If the
load current in either of the regulators falls below a
predetermined value, the regulator will enter into Burst
Mode operation independent of the other regulator. When
the MODE pin is connected to ground, continuous PWM
operation is selected. It provides the lowest output voltage
ripple and current ripple, albeit at the cost of lower
efficiency under light load conditions.
The Burst Mode operation is disabled when the device is
USB or wall powered. The device operates in forced PWM
mode when powered from USB or wall input (irrespective
of the state of the MODE pin). Also, at initial power up, the
device operates in forced PWM mode during the 262ms
initial delay timeout.
Figure 9 shows the Main and Core converters in Burst
Mode operation.
VMAIN
100mV/DIV
(AC COUPLED)
IL2
500mA/DIV
VCORE
100mV/DIV
(AC COUPLED)
IL1
100mA/DIV
VBATT = 2.4V
IMAIN = 37.5mA
ICORE = 6.2mA
20µs/DIV
3456 F09
Figure 9. The LTC3456 in Burst Mode Operation
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LTC3456
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OPERATIO
VOLTAGE MONITORS
Low-Battery Detection
The LTC3456 has an on-chip gain block that can be used
for low-battery detection. The low-battery trip point can be
set by two resistors (Figure 10). The nominal voltage at
AIN is 0.8V. If the voltage at AIN falls below 0.8V, AO sinks
current to ground.
The battery minimum voltage can be set according to the
formula:
⎛ R2 ⎞
VBATT(MIN) = 0.8 V⎜ 1 + ⎟
⎝ R1⎠
The AIN input bias current is quite low, on the order of 2nA
(typ). Large resistor values (R2 ~ 100k) can be used in the
divider network. This helps in minimizing the loading on
the battery. AO is an open-drain logic output. The voltage
at AIN must always be kept less than 2V. If the gain block
is not used then connect AIN to ground.
There is no built-in hysteresis in the gain block. Hysteresis
can be added by connecting resistor R4 from AIN to AO as
shown in Figure 10. Ensure that R4 ≅ 10R3 for correct
operation. With the values shown in Figure 10b, the circuit
has 180mV of hysteresis.
VBATT
1.8V TO 3.2V
R2
100k
VCORE
LTC3456
AIN
R3
100k
AO
R1
80.6k
(10a)
VBATT
R2
100k
VCORE
LTC3456
AIN
R3
100k
The gain block can be configured to drive an external PNP
transistor and generate an auxiliary voltage as shown in
Figure 11. An auxiliary output voltage 2.5V/20mA is generated from the VMAIN (3.3V) power supply.
VMAIN
3.3V
100k
LTC3456
AIN
Q1
PHILIPS
MMBT3906
AO
43.2k
VAUX
2.5V
20mA
2.2µF
20.5k
3456 F11
Figure 11. Generating Auxiliary Voltage Supply
External Power Detection
The LTC3456 has an EXT_PWR output pin to indicate the
presence of USB or wall power. Whenever the WALLFB pin
is pulled higher than 1.25V (AC adapter present), or the
USB input is greater than 4V and the SUSPEND pin is low
(USB power available), the EXT_PWR pin is pulled to
ground. When pulled low, this pin is capable of sinking
5mA suitable for driving an external LED. Otherwise, this
pin is in a high impedance state.
Overtemperature Protection
The maximum allowable junction temperature for LTC3456
is 125°C. In normal operation, the IC does not dissipate
much heat and its junction temperature stays well below
125°C at an ambient temperature of 85°C or less. If the
junction temperature exceeds 150°C, the Core, Main and
Hot Swap outputs are turned off and RESET is pulled low.
AO
R1
80.6k
R4
1M
3456 F10
(10b)
The VINT output stays alive in this state. The Core and Main
outputs will remain off until the die temperature falls below
150°C, regardless of the state of the PWRKEY and PWRON
inputs.
Figure 10. Low-Battery Detector (10a) and
Low-Battery Detector with Hysteresis (10b)
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19
LTC3456
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APPLICATIO S I FOR ATIO
COMPONENT SELECTION
Inductor Selection
The high frequency operation of LTC3456 allows the use
of small surface mount inductors. For most applications,
the inductance value will be between 2.2µH and 10µH. The
desired value of inductance is determined by the amount
of ripple current, ∆IL, in the converter.
The inductor current ripple, ∆IL, for Boost mode operation
neglecting the voltage drop across the switches is given
by:
∆IL =
VIN • ( VOUT – VIN )
VOUT • f • L
The inductor current ripple, ∆IL, for Buck mode operation
neglecting the voltage drop across the switches is given
by:
∆IL1 =
VOUT • ( VIN – VOUT )
VIN • f • L
where
L = Inductor
f = Operating Frequency
VIN = Input Voltage
VOUT = Output Voltage
The ∆IL is typically set to 20% to 40% of the maximum
inductor current.
The inductor should have a saturation current rating
greater than the peak inductor current required for the
application. Also, ensure that the inductor has a low DCR
(copper wire resistance) to minimize I2R power losses.
Several inductors that work well with the LT3456 are listed
in Table 1. Consult each manufacturer for more detailed
information and for their entire selection of related parts.
Table 1. Recommended Inductors
PART
L
(µH)
MAX
DCR
(Ω)
CURRENT
RATING
(mA)
ELT5KT-4R7
ELT5KT-100
4.7
10
0.2
0.36
950
680
Panasonic
(714) 373-7939
www.panasonic.com
CDRH4D18-4R7
CDRH4D18-100
4.7
10
0.16
0.2
840
610
Sumida
(847) 956-0666
www.sumida.com
LQH32CN4R7
LQH32CN100
4.7
10
0.15
0.3
650
450
Murata
(814) 237-1431
www.murata.com
1002AS-4R7M
1002AS-100M
4.7
10
0.19
0.32
910
620
Toko
(800) 745-8656
www.toko.com
VENDOR
Output Capacitor Selection
Low ESR (equivalent series resistance) capacitors should
be used at the output to minimize the output ripple voltage.
Multilayer ceramic capacitors are an excellent choice, as
they have an extremely low ESR and are available in very
small packages. Use only X7R or X5R dielectrics, as these
materials retain their capacitance over wider voltage and
temperature ranges than other dielectrics. A 1µF to 22µF
output capacitor is sufficient for most applications. Solid
tantalum or OS-CON capacitors can be used, but they will
occupy more board area than a ceramic and will have a
higher ESR for the same device footprint. Always use a
capacitor with a sufficient voltage rating.
Table 2 shows a list of several ceramic capacitor manufacturers. Consult the manufacturers for detailed information
on their entire selection of ceramic parts.
Table 2. Ceramic Capacitor Manufacturers
Taiyo Yuden
(408) 573-4150
www.t-yuden.com
AVX
(803) 448-9411
www.avxcorp.com
Murata
(714) 852-2001
www.murata.com
TDK
(847) 803-6100
www.component.tdk.com
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LTC3456
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APPLICATIO S I FOR ATIO
Input Capacitor Selection
The LTC3456 can be powered from three different power
sources: battery, USB or the AC wall adapter. Choose a
4.7µF or higher X5R or X7R type ceramic capacitor for
bypassing the input of LTC3456.
VUSB
(2V/DIV)
However, special care must be taken when bypassing the
USB and AC wall adapter inputs with ceramic capacitors.
Ceramic capacitors with their low ESR can form a resonant
tank circuit with the stray wiring inductance of the power
leads. This can cause large voltage transients at the input
of the device when the power is applied quickly (for
example, plugging the AC adapter output into the portable
device). This voltage spike can be large enough to damage
the LTC3456. A possible solution is to clamp the input
voltage or insert a small resistor in series with the ceramic
capacitor as shown in Figure 12. Please refer to Linear
Technology Application Note AN88 for more details.
VEXT
(2V/DIV)
USB
INPUT
0.1mS/DIV
Figure 13(a). Hot-Plugging the USB Power (5.5V Input) with
a 4.7µF Ceramic Capacitor Used for Bypassing.
VUSB
(2V/DIV)
VEXT
(2V/DIV)
USB
1Ω
4.7µF
LTC3456
0.1mS/DIV
AC
ADAPTER
VEXT
1Ω
10µF
3456 F12
4.7µF
Figure 12. Bypassing USB and AC Wall Adapter Inputs
Figure 13(a) shows the voltage waveforms at the USB and
VEXT pins resulting from hot-plugging a 5.5V input supply.
As seen in the figure, there is a large voltage transient (in
excess of 8V) at the USB input pin. This voltage spike
exceeds the 6V absolute maximum voltage rating of the
pin, and can cause serious performance degradation or,
even complete failure of the part. The spike can be greatly
reduced by adding a 1Ω series resisitor with the 4.7µF
ceramic capacitor, as seen in Figure 13(b). The voltage
ringing at the USB pin is completely removed and the
maximum voltage spike at the USB pin is less than the
maximum voltage rating of 6V.
Figure 13(b). Hot-Plugging the USB Power (5.5V Input) with a
4.7µF Ceramic Capacitor and 1Ω Series Resistor Used for
Bypassing
Output Voltage Programming
The output of the core converter can be set by a resistor
divider according to the formula:
⎛ R2 ⎞
VCORE = 0.8 V ⎜ 1+ ⎟
⎝
R1⎠
The external resistor divider is connected at the output as
shown in Figure 14. Choose 1% resistors for better
accuracy. R1 should be 80.6k or smaller for better noise
immunity.
0.8V ≤ VCORE ≤ VBATT(MIN)
R2
FB1
LTC3456
R1
AGND
3456 F13
Figure 14. Setting the Core Output Voltage
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LTC3456
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APPLICATIO S I FOR ATIO
AC ADAPTER UVLO VOLTAGE PROGRAMMING
The AC wall adapter UVLO voltage can be set by a resistor
divider connected across the AC wall adapter as shown in
Figure 15.
The AC wall adapter UVLO voltage can be set by a resistor
divider according to the formula:
⎛ R2 ⎞
VADAPTER(MIN) = 1.25V ⎜ 1+ ⎟
⎝
R1⎠
LTC3456
USB
1Ω
EN
4.7µF
D1
VEXT
AC
ADAPTER
R2
10µF
WALLFB
R1
Connect the WALLFB pin to ground if the wall adapter is
not used.
Rectifier Diode Selection
Choose 1% resistors for better accuracy. When the WALLFB
pin voltage is higher than 1.25V, the LTC3456 will be
powered from the VEXT pin. The internal USB power switch
is turned off and the power is derived from the AC adapter
through the diode D1. Ensure that the AC adapter UVLO
voltage is set high enough to make VEXT > 4V during
regular operation.
USB
POWER
A 4.32k or smaller resistor should be chosen for R1 to
prevent this behavior. When the power is being delivered
from the wall adapter, efficiency is not a big concern and
choosing small value R1 and R2 resistors should be
acceptable.
3456 F14
The diode, D1, shown in Figures 15 and 16 is used to
connect the VEXT pin to the AC adapter input. The IC is
powered through the diode D1 when running off the AC
adapter. A Schottky diode is recommended to minimize
the voltage drop from the AC adapter to the VEXT pin.
VEXT(MIN) = VADAPTER(MIN) – VDIODE(MAX)
Always ensure that VEXT > 4V during regular operation.
Choose a diode with a current rating high enough to handle
the input current.
Choose a Schottky diode with low reverse leakage current
(as explained in previous section). ON Semiconductor
MBRM120E (20V/1A) is a good choice for a low leakage
Schottky rectifier.
The Zetex ZLLS400 (40V/0.5A) Schottky diode is available
in a small surface mount package and is also a good fit for
this application.
LTC3456
USB
Figure 15. Setting the Wall Adapter UVLO Voltage
When the device is powered from the USB input (AC
adapter is not present), the VEXT pin is charged close to the
USB voltage. The reverse leakage current of the diode D1
flows through R1 and R2 as shown in Figure 16. If the
leakage current is large enough to pull the WALLFB pin
above 1.25V, then the USB power is switched off. The
LTC3456 will then enter into a hiccup mode with USB
power being turned on and off in a periodic fashion.
USB
POWER
1Ω
EN
4.7µF
D1
AC ADAPTER
NOT PRESENT
R2
ILKG
10µF
VEXT
WALLFB
R1
3456 F15
Figure 16. Diode D1 Leakage Current Flow in USB Powered Mode
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LTC3456
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APPLICATIO S I FOR ATIO
2 AA +
CELLS
4.7µF
L2
4.7µH
100k
VBATT
22µF
L3
10µH
SW2_BST
SW2_BK
AIN
VINT
1µF
MAIN OUTPUT
3.3V
150mA
1µF
Hot Swap OUTPUT
3.3V
50mA
10µF
CORE OUTPUT
1.8V
200mA
1µF
VMAX
(POWERS
REAL-TIME CLOCK)
VMAIN
80.6k
AO
USB POWER
(4.35V TO 5.5V)
4.7µF
HSO
USBHP
USB
CONTROLLER
L1
10µH
SUSPEND
1Ω
SW1
LTC3456
USB
1k
AC
ADAPTER
(5V ±10%)
100k
EXT_PWR
11.3k
220pF
FB1
VEXT
4.7µF
80.6k
10µF
1Ω
WALLFB
4.32k
VINT
3.3V
VMAX
PWRKEY
PBSTAT RESET MODE PWRON PGND AGND
µP
3456 TA01
BOLD LINES INDICATE HIGH CURRENT PATHS
Figure 17. Layout Diagram
BOARD LAYOUT CONSIDERATION
DESIGN EXAMPLE
As with all switching regulators, careful attention must be
paid to the PCB board layout and component placement.
To prevent electromagnetic interference (EMI) problems,
proper layout of high frequency switching paths is essential. Minimize the length and area of all traces connected to
the switching node pins (SW1, SW2_BK, SW2_BST).
Keep the feedback pins FB1 and AIN away from the
switching nodes. The power traces shown as bold lines in
Figure 17 should be kept short, direct and wide.
As a design example, we target a 2 AA cell powered GPS
navigator application. Figure 18 shows LTC3456 being
used to provide power to the core and I/O peripherals. The
flash memory card is powered from the Hot Swap output.
The QFN package has an exposed paddle and it must be
connected to the system ground. The ground connection
for the feedback resistors should be tied directly to the
ground plane and not shared with any other component,
ensuring a clean, noise-free connection.
Core output needs to be 1.8V and the maximum load
current is 200mA. The inductor current ripple, ∆IL, for
buck mode of operation is given by:
∆IL1 =
VOUT • ( VIN – VOUT )
VIN • f(L1)
The maximum inductor current in L1 is set by the core
converter current limit; i.e., 400mA (minimum). Choosing
∆IL = 100mA (~25% of peak inductor current) is a reasonable starting value.
Substituting VOUT = 1.8V, VIN(MAX) = 3.2V, ∆IL1 = 100mA,
f = 1MHz in above equation gives:
L1 =
1.8 V • (3.2V – 1.8 V )
= 7.8µH
3.2V • 100mA • 1MHz
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23
LTC3456
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APPLICATIO S I FOR ATIO
We can choose a low resistance 7.8µH or slightly higher
value inductor. We can choose a 450mA, 10µH inductor
(Murata LQH32CN100).
We need to check the ripple current when the core output
is powered from the AC adapter or the USB. L1 is used to
power the output in this case too.
Substituting VOUT = 1.8V, VIN(MAX) = 5.5V , L1 = 10µH,
f = 1MHz in above equation gives:
∆IL1 =
1.8 V • (5.5V – 1.8 V )
= 120mA
5.5V • 10µH • 1MHz
L1 gives a reasonable value of ripple current when powered from both battery and USB or AC adapter.
We can choose a low resistance 4.7µH, 650mA inductor
(Murata LQH32CN4R7M53).
When powered from the AC adapter or the USB, the 3.3V
output is generated via the L3 buck inductor. The inductor
current ripple (∆IL3) for Buck mode operation is given by:
∆IL3 =
VOUT • ( VIN – VOUT )
VIN • f(L3)
A reasonable starting value of inductor ripple current is
∆IL3 = 100mA. Substituting VOUT = 3.3V, VIN(MAX) = 5.5V,
∆IL3 = 100mA, f = 1MHz in above equation gives:
L3 =
3.3V • (5.5V – 3.3V )
= 13.2µH
5.5V • 100mA • 1MHz
The main output needs to be 3.3V and the maximum load
current is 200mA. Hot Swap current is derived from the
same main converter.
We can choose a 450mA, 10µH inductor (Murata
LQH32CN100K53).
When powered from the 2 AA cell, the 3.3V output is
generated via the L2 boost inductor. The inductor current
ripple, ∆IL2, for Boost mode operation is given by:
A 4.7µF to 22µF (X5R or X7R) ceramic output capacitor is
sufficient for most applications. They have a low ESR and
result in a low output ripple.
VIN • ( VOUT – VIN )
∆IL2 =
VOUT • f(L2)
Figure 18 shows the complete circuit along with the
efficiency curves.
A reasonable starting value of inductor ripple current is
∆IL2 = 150mA. Substituting VOUT = 3.3V, VIN(MIN) = 1.8V,
∆IL2 = 150mA, f = 1MHz in above equation gives:
L2 =
1.8 V • (3.3V – 1.8 V )
= 5.4µH
3.3V • 150mA • 1MHz
3456fa
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LTC3456
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APPLICATIO S I FOR ATIO
2 AA
CELLS
+
C1
4.7µF
L3
10µH
L2
4.7µH
100k
VBATT
C9
22µF
SW2_BST
SW2_BK
VINT
AIN
VMAIN
C8
1µF
80.6k
AO
USB POWER
(4.35V TO 5.5V)
C2
4.7µF
1Ω
HSO
USBHP
USB
CONTROLLER
L1
10µH
SUSPEND
SW1
LTC3456
USB
1k
D1
AC
ADAPTER
(5V ±10%)
C3
4.7µF
1Ω
220pF
100k
EXT_PWR
C6
10µF
MAIN OUTPUT
3.3V
150mA
Hot Swap OUTPUT
3.3V
50mA
CORE OUTPUT
1.8V
200mA
FB1
VEXT
C4
10µF
11.3k
C7
1µF
VINT
3.3V
80.6k
WALLFB
VMAX
PWRKEY
4.32k
C5
1µF
PBSTAT RESET MODE PWRON PGND AGND
µP
C2 TO C5: X5R OR X7R, 6.3V
C1, C6 TO C9: X5R OR X7R, 4V
D1: ON SEMICONDUCTOR MBRM120E
VMAX
(POWERS
REAL-TIME CLOCK)
3456 F17
L1, L3: MURATA LQH32CN100K53
L2: MURATA LQH32CN4R7M53
Figure 18. 2 AA Cells to 1.8V/200mA and 3.3V/200mA Outputs
Using All Ceramic Capacitors with Lowest Parts Count
Efficiency (USB Powered)
Efficiency (Battery Powered)
100
40
POWER LOSS
30
20
3.3V
OUTPUT
1.8V
OUTPUT
10
0
1
10
100
LOAD CURRENT (mA)
100
50
0
1000
3456 TA01b
80
80
70
70
60
50
40
60
50
40
30
30
20
20
1.8V OUTPUT
3.3V OUTPUT
10
0
1
VWALL = 5V
90
EFFICIENCY (%)
150
EFFICIENCY
50
POWER LOSS (mW)
60
3.3V
OUTPUT
EFFICIENCY (%)
200
1.8V
OUTPUT
70
100
VUSB = 5V
VUSBHP = 2V
90
80
EFFICIENCY (%)
100
250
VBATT = 2.4V
90 MODE = 0V
Efficiency (Wall Powered)
10
100
LOAD CURRENT (mA)
1000
3456 G02
1.8V OUTPUT
3.3V OUTPUT
10
0
1
10
100
LOAD CURRENT (mA)
1000
3456 F17d
3456fa
25
LTC3456
U
TYPICAL APPLICATIO
2 AA Cells Power Complete Power Supply for Handheld Devices
2 AA
CELLS
+
C1
4.7µF
L2
4.7µH
SW2_BST
SW2_BK
VINT
VMAIN
VBATT
USBHP
USB
CONTROLLER
C10
22µF
L3
10µH
C9
1µF
MAIN OUTPUT
3.3V
100mA
100k
Q1
A0
SUSPEND
49.9k
USB POWER
(4.35V TO 5.5V)
C2
4.7µF
20k
1Ω
LTC3456
EXT_PWR
C4
10µF
D1
AC
ADAPTER
(5V ±10%)
HSO
C7
1µF
L1
10µH
1k
VEXT
C8
2.2µF
AIN
USB
LCD LOGIC BIAS
2.8V
10mA
SW1
VEXT
100k
220pF
C6
10µF
FLASH MEMORY CARD
3.3V
50mA
CORE OUTPUT
1.8V
200mA
FB1
80.6k
11.3k
WALLFB
C3
4.32k
4.7µF
1Ω
PWRKEY
VMAX
PBSTAT RESET MODE PWRON PGND AGND
C5
1µF
VMAX
(TO REAL-TIME CLOCK)
3456 TA02a
MICROCONTROLLER
L1, L3: MURATA LQH32CN100K53
C1, C6 TO C10: X5R OR X7R, 4V
L2: MURATA LQH32CN4R7M53
C2 TO C5: X5R OR X7R, 6.3V
D1: ON SEMICONDUCTOR MBRM120E Q1: PHILIPS MMBT3906
Load Transient (USB/Wall Powered)
Load Transient (Battery Powered)
VCORE
100mV/DIV
(AC COUPLED)
IL1
200mA/DIV
VMAIN
200mV/DIV
(AC COUPLED)
VCORE
100mV/DIV
(AC COUPLED)
IL1
200mA/DIV
VMAIN
200mV/DIV
(AC COUPLED)
IL2
200mA/DIV
IL3
200mA/DIV
VBATT = 2.4V
100µs/DIV
IMAIN = 20mA TO 100mA
ICORE = 20mA TO 150mA
3456 TA02b
VEXT = 5V
200µs/DIV
IMAIN = 20mA TO 100mA
ICORE = 5mA TO 150mA
3456 TA02c
3456fa
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LTC3456
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PACKAGE DESCRIPTIO
UF Package
24-Lead Plastic QFN (4mm × 4mm)
(Reference LTC DWG # 05-08-1697)
0.70 ±0.05
4.50 ± 0.05
2.45 ± 0.05
3.10 ± 0.05 (4 SIDES)
PACKAGE OUTLINE
0.25 ±0.05
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
4.00 ± 0.10
(4 SIDES)
BOTTOM VIEW—EXPOSED PAD
0.23 TYP
R = 0.115
(4 SIDES)
TYP
23 24
0.75 ± 0.05
0.38 ± 0.10
PIN 1
TOP MARK
(NOTE 6)
1
2
2.45 ± 0.10
(4-SIDES)
(UF24) QFN 1103
0.200 REF
0.00 – 0.05
0.25 ± 0.05
0.50 BSC
NOTE:
1. DRAWING PROPOSED TO BE MADE A JEDEC PACKAGE OUTLINE MO-220 VARIATION (WGGD-X)—TO BE APPROVED
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE, IF PRESENT
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
3456fa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
27
LTC3456
U
TYPICAL APPLICATIO
Quad-Output Converter Runs Off 2 AA Cells, USB or Wall Adapter
2 AA
CELLS
+
C1
4.7µF
L2
4.7µH
SW2_BST
SW2_BK
VINT
VMAIN
VBATT
USBHP
USB
CONTROLLER
C10
22µF
L3
10µH
C9
1µF
Q2
A0
SUSPEND
LCD LOGIC BIAS
2.8V
C8
2.2µF 10mA
49.9k
USB POWER
(4.35V TO 5.5V)
C2
4.7µF
AIN
USB
20k
1Ω
LTC3456
EXT_PWR
C3
10µF
D1
AC
ADAPTER
(5V ±10%)
HSO
L1
10µH
1k
VEXT
MAIN OUTPUT
3.3V
100mA
100k
D2
C7
1µF
FLASH MEMORY CARD
3.3V
50mA
CORE OUTPUT
2.5V
100mA
SW1
Q1
VEXT
10µF
43.2k
330pF
FB1
20.5k
11.3k
WALLFB
C4
4.32k
4.7µF
PWRKEY
VMAX
PBSTAT RESET MODE PWRON PGND AGND
1Ω
C5
1µF
VMAX
TO REAL-TIME CLOCK
(ALIVE OR SHUT DOWN)
3456 TA03
MICROCONTROLLER
L1, L3: MURATA LQH32CN100K53
C1, C6 TO C10: X5R OR X7R, 4V
L2: MURATA LQH32CN4R7M53
C2 TO C5: X5R OR X7R, 6.3V
D1, D2: ON SEMICONDUCTOR MBRM120E Q1: FAIRCHILD FDG327N
Q2: PHILIPS MMBT3906
RELATED PARTS
PART NUMBER
LT1616
LTC1879
LTC3405/LTC3405A
LTC3406/LTC3406B
LTC3407
LTC3412
LTC3414
LTC3440/LTC3441
LTC3455
DESCRIPTION
500mA (IOUT), 1.4MHz, High Efficiency Step-Down
DC/DC Converter
1.2A (IOUT), 550kHz, Synchronous Step-Down
DC/DC Converter
300mA (IOUT), 1.5MHz, Synchronous Step-Down
DC/DC Converter
600mA (IOUT), 1.5MHz, Synchronous Step-Down
DC/DC Converter
Dual 600mA (IOUT), 1.5MHz, Synchronous Step-Down
DC/DC Converter
2.5A (IOUT), 4MHz, Synchronous Step-Down
DC/DC Converter
4A (IOUT), 4MHz, Synchronous Step-Down
DC/DC Converter
600mA/1A (IOUT), 2MHz/1MHz, Synchronous Buck-Boost
DC/DC Converter
Dual DC/DC Converter with USB Power Manager
and Li-Ion Battery
COMMENTS
90% Efficiency, VIN: 3.6V to 25V, VOUT(MIN) = 1.25V, IQ = 1.9mA,
ISD < 1µA, ThinSOT
95% Efficiency, VIN: 2.7V to 10V, VOUT(MIN) = 0.8V, IQ = 15µA,
ISD < 1µA, TSSOP16
95% Efficiency, VIN: 2.7V to 6V, VOUT(MIN) = 0.8V, IQ = 20µA,
ISD < 1µA, ThinSOT
96% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.6V, IQ = 20µA,
ISD < 1µA, ThinSOT
96% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.6V, IQ = 40µA,
ISD < 1µA, MS10E
95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.8V, IQ = 60µA,
ISD < 1µA, TSSOP16E
95% Efficiency, VIN: 2.25V to 5.5V, VOUT(MIN) = 0.8V, IQ = 64µA,
ISD < 1µA, TSSOP16E
95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 2.5V, IQ = 25µA/50µA,
ISD < 1µA, MS/DFN
96% Efficiency, Seamless Transition Between Inputs, IQ = 110µA,
ISD < 2µA, QFN
3456fa
28
Linear Technology Corporation
LT/LT 1005 REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2004