FEATURES
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LTC3455/LTC3455-1
Dual DC/DC Converter
with USB Power Manager
and Li-Ion Battery Charger
DESCRIPTION
The LTC
®
3455/LTC3455-1 are complete power manage-
ment solutions for a variety of portable applications.
These devices contain 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/LTC3455-1 provide 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 discharged to ground during
shutdown to provide complete output disconnect. These
devices are available in a 4mm
×
4mm 24-pin exposed-
pad QFN package.
L,
LT, LTC, LTM and Burst Mode 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 6522118.
Seamless Transition between Input Power Sources:
Li-Ion Battery, USB, and 5V Wall Adapter
Accurate USB Current Limiting (500mA/100mA)
Two High Efficiency DC/DC Converters: Up to 96%
Thermal Regulation Maximizes Battery Charge
Rate without Risk of Overheating
Full-Featured Li-Ion Battery Charger with 4.2V Float
Voltage for LTC3455 and 4.1V for LTC3455-1
4.1V Float Voltage (LTC3455-1) Improves Battery Life
and High Temperature Safety Margin
Hot Swap™ Output for SDIO and Memory Cards
Pin-Selectable Burst Mode
®
Operation
Output Disconnect: All Outputs Discharged to Ground
During Shutdown
Available in a 4mm
×
4mm
×
0.75mm 24-Pin
QFN Package
APPLICATIONS
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Handheld Computers
Digital Cameras
MP3 Players
TYPICAL APPLICATION
USB 5V
1Ω
4.7μF
WALL 5V
1Ω
4.7μF
3.32k
10μF
1k
5.6V
USB
CONTROLLER
USB
SUSPEND
USBHP
V
MAX
MODE
HSON
ON2
PWRON
RST
PBSTAT
LTC3455/LTC3455-1
CHRG
WALLFB
0.1μF
1.24k
2.49k
V
BAT
4.7μF
SINGLE
CELL Li-ION
3.3V TO 4.2V
TIMER
PROG
HSI
SW2
10pF
FB2
1M
LBO
V
BAT
2.49M
AI
806k
FB1
GND
3455 TA01a
μC
Efficiency
100
95
1M
1M
1.8V
SWITCHER 2
V
OUT2
= 3.3V
1000
90
POWER LOSS (mW)
EFFICIENCY (%)
85
80
75
70
65
60
55
V
BAT
= 3.6V
1
10
100
LOAD CURRENT (mA)
1
1000
POWER LOSS FOR
BOTH OUTPUTS
10
SWITCHER 1
V
OUT1
= 1.8V
100
ON/OFF
ON
HSO
3.3V, HS
1μF
4.7μH
249k
80.6k
3.3V
0.5A
10μF
+
1.8V
AO
4.7μH
SW1
10pF
100k
80.6k
1.8V
0.4A
10μF
3455 TA01b
3455fc
1
LTC3455/LTC3455-1
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
PWRON
PBSTAT
MODE
ON2
18 FB2
17 AO
25
16 AI
15 HSON
14 HSO
13 HSI
7
SW1
8
USB
9 10 11 12
V
MAX
WALLFB
V
BAT
SW2
RST
ON
FB1 1
PROG 2
TIMER 3
CHRG
4
USBHP 5
SUSPEND 6
Transient (t < 1ms and Duty Cycle < 1%):
V
MAX
USB Voltages .................................. –0.3V to 7V
Steady State:
V
BAT
, V
MAX
, USB Voltages ........................ –0.3V to 6V
SW1, SW2 Voltages ................... –0.3V to (V
MAX
+ 0.3V)
TIMER Voltage ........................... –0.3V to (V
MAX
+ 0.3V)
PWRON,
ON,
ON2, HSON Voltages ............. –0.3V to 6V
PBSTAT,
RST, CHRG,
AO Voltages ............... –0.3V to 6V
HSI, HSO Voltages ....................................... –0.3V to 6V
MODE, USBHP SUSPEND Voltages.............. –0.3V to 6V
,
WALLFB, AI, PROG Voltages ........................ –0.3V to 2V
FB1, FB2 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
UF PACKAGE
24-LEAD (4mm 4mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 37°C/W,
θ
JC
= 4.3°C/W
EXPOSED PAD (PIN 25) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3455EUF#PBF
LTC3455EUF-1#PBF
TAPE AND REEL
LTC3455EUF#TRPBF
LTC3455EUF-1#TRPBF
PART MARKING
3455
34551
PACKAGE DESCRIPTION
24-Lead (4mm
×
4mm) Plastic QFN
24-Lead (4mm
×
4mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
ELECTRICAL CHARACTERISTICS
PARAMETER
Battery Undervoltage Lockout Voltage
Battery Undervoltage Lockout Hysteresis
V
BAT
Pin Quiescent Current (Note 3)
Burst Mode, Battery Powered
PWM Mode, Battery Powered
USB Powered
Wall Powered
Shutdown
ON
Pin Threshold
PWRON Pin Threshold
ON2 Pin Threshold
MODE Pin Threshold
WALLFB Pin Threshold Voltage
WALLFB Pin Hysteresis
WALLFB Rising
CONDITIONS
V
BAT
Rising
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
BAT
= 3.6V, V
MAX
= 3.6V, V
PWRON
= 2V, V
ON
is open, V
ON2
= 0V,
V
USB
= 0V, V
WALLFB
= 0V unless otherwise noted.
MIN
2.9
TYP
3.0
450
V
ON2
= V
MODE
= 1V, Not Switching
V
ON2
= 1V, V
MODE
= 0V, Not Switching
V
USB
= 5V, Charger Off
V
WALL
= 1.5V, V
MAX
= 4.5V, Charger Off
V
PWRON
= 0V, V
MAX
= 0V
110
500
10
10
2
0.8
0.8
0.8
0.8
l
MAX
3.2
UNITS
V
mV
160
800
20
20
4
1.1
1.0
1.0
1.0
1.26
μA
μA
μA
μA
μA
V
V
V
V
V
mV
3455fc
1.20
1.23
60
2
LTC3455/LTC3455-1
ELECTRICAL CHARACTERISTICS
PARAMETER
ON
Pin Pullup Current
PWRON Pin Pulldown Current
ON2 Pin Pulldown Current
MODE Pin Pullup Current
WALLFB Pin Input Bias Current
PBSTAT Pin Low Voltage
RST
Pin Low Voltage
RST
Pulse Duration
Battery-V
MAX
PMOS
V
MAX
PMOS Switch On-Resistance
V
MAX
Switch Current Limit
V
MAX
Switch Current Limit at Startup
Gain Block
AI Pin Threshold Voltage
AI Pin/FB2 Pin Voltage Difference
AI Pin Input Bias Current
AO Pin Sink Current
AO Pin Voltage
Switching Regulators
FB1, FB2 Voltage
FB1, FB2 Voltage Line Regulation
FB1, FB2 Voltage Burst Mode Hysteresis
FB1, FB2 Pin Input Bias Current
Switching Frequency
PMOS Switch On-Resistance
NMOS Switch On-Resistance
PMOS Switch Current Limit
USB Power Manager
USB Undervoltage Lockout Voltage
USB Undervoltage Lockout Hysteresis
USB Minimum Voltage to Charge Battery
USB PMOS Switch On-Resistance
USB Current Limit
USB Suspend Mode Bias Current
SUSPEND Pin Threshold
USBHP Pin Threshold
SUSPEND Pin Pulldown Current
USBHP Pin Pulldown Current
V
SUSPEND
= 0.5V
V
USBHP
= 0.5V
V
USB
= 5V
V
USB
= 5V, V
USBHP
= 2V
V
USB
= 5V, V
USBHP
= 0V
V
USB
= 5V, V
SUSPEND
= 2V
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
BAT
= 3.6V, V
MAX
= 3.6V, V
PWRON
= 2V, V
ON
is open, V
ON2
= 0V,
V
USB
= 0V, V
WALLFB
= 0V unless otherwise noted.
CONDITIONS
V
ON
= 1V
V
PWRON
= 1V
V
ON2
= 1V
V
MODE
= 1V
V
WALLFB
= 1.35V
V
ON
= 0V, I
PBSTAT
= 100μA
V
ON
= 0V, I
PBSTAT
= 1mA
I
RST
= 100μA
I
RST
= 1mA
After FB1 and FB2 in Regulation
l
MIN
TYP
2.5
2.5
2.5
2.5
±1
0.02
0.20
0.02
0.20
200
0.15
MAX
UNITS
μA
μA
μA
μA
±30
0.10
0.35
0.10
0.35
nA
V
V
V
V
ms
Ω
A
A
2.5
With V
MAX
Rising, V
MAX
= 3V, V
BAT
= 3.6V
0.4
0.784
–8
l
4.0
0.9
0.805
0
±1
1.8
0.8
0.826
8
±25
2.5
1.2
0.826
V
mV
nA
mA
V
V
%/V
mV
V
FB2
– V
AI
V
AI
= 0.85V
V
AI
= 0.6V, V
AO
= 1.5V
V
AI
= 0.6V, I
AO
= 1mA
1.0
0.784
0.805
0.01
8
V
MAX
= 3V to 5V
V
MODE
= 2V
V
FB1
= V
FB2
= 0.85V
Both Switchers
Both Switchers
Both Switchers
Switcher 1
Switcher 2
From Low to High
450
700
3.75
l
±1
1.2
1.5
0.35
0.45
600
900
3.90
150
4.0
0.5
440
60
475
80
4
0.8
0.8
2.5
2.5
±25
1.8
nA
MHz
Ω
Ω
850
1300
4.10
mA
mA
V
mV
V
Ω
500
100
20
1.1
1.1
mA
mA
μA
V
V
μA
μA
3455fc
3
LTC3455/LTC3455-1
ELECTRICAL CHARACTERISTICS
PARAMETER
Hot Swap Output
Hot Swap PMOS Switch On-Resistance
Hot Swap PMOS Switch Current Limit
HSON Pin Threshold
HSON Pin Pulldown Current
Battery Charger
Regulated Charger V
BAT
Voltage
Charger Current Limit (USB Powered)
Charger Current Limit (Wall Powered)
Recharge Battery Voltage Threshold
Trickle Charge Trip Threshold
Trickle Charge Trip Hysteresis
Trickle Charge Current
PROG Pin Current
PROG Pin Voltage
CHRG
Pin Output Low Voltage
Timer Accuracy
Junction Temperature in Constant
Temperature Mode
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
The LTC3455/LTC3455-1 are guaranteed to meet specified
performance from 0°C to 85°C and is designed, characterized and
R
PROG
= 2.49kΩ, V
BAT
= 2V
Internal Pull-Up Current, No R
PROG
R
PROG
= 2.49kΩ
I
CHRG
= 5mA
C
TIMER
= 0.1μF
0°C ≤ T
A
≤ 85°C (LTC3455)
0°C ≤ T
A
≤ 85°C (LTC3455-1)
R
PROG
= 2.49kΩ, V
USBHP
= 2V, V
USB
= 5V, 0°C ≤ T
A
≤ 85°C
R
PROG
= 2.49kΩ, V
USBHP
= 0V, V
USB
= 5V, 0°C ≤ T
A
≤ 85°C
R
PROG
= 2.49kΩ, V
MAX
= 4.5V, 0°C ≤ T
A
≤ 85°C
V
BAT(REGULATED)
– V
RECHARGE
Battery Voltage Rising
4.158
4.058
425
4.200
4.1
400
50
500
150
2.85
60
65
2
1.23
0.75
±10
105
4.242
4.142
470
90
575
V
V
mA
mA
mA
mV
V
mV
mA
μA
V
V
%
°C
V
HSI
= 3.3V
V
HSI
= 3.3V, V
HSO
= 2.5V
120
0.9
160
0.8
2.5
1.1
Ω
mA
V
μA
CONDITIONS
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
BAT
= 3.6V, V
MAX
= 3.6V, V
PWRON
= 2V, V
ON
is open, V
ON2
= 0V,
V
USB
= 0V, V
WALLFB
= 0V unless otherwise noted.
MIN
TYP
MAX
UNITS
expected to meet these extended temperature limits, but is not 100%
tested at –40°C and 85°C.
Note 3:
Quiescent current is pulled from the V
BAT
pin when neither USB
or wall power is present, and from the V
MAX
pin when either USB or Wall
power is present.
TYPICAL PERFORMANCE CHARACTERISTICS
Burst Mode Quiescent Current
120
100
QUIESCENT CURRENT (μA)
80
60
40
20
0
–50 –25
V
BAT
= 3.6V
NOT SWITCHING
50
25
75
0
TEMPERATURE (°C)
100
125
BOTH SWITCHERS ENABLED
QUIESCENT CURRENT (μA)
ONLY SWITCHER 1 ENABLED
600
BOTH SWITCHERS ENABLED
500
400
300
200
100
0
–50 –25
V
BAT
= 3.6V
NOT SWITCHING
50
25
75
0
TEMPERATURE (°C)
100
125
ONLY SWITCHER 1 ENABLED
QUIESCENT CURRENT (μA)
4
PWM Mode Quiescent Current
5
Shutdown Quiescent Current
V
BAT
= 3.6V
3
2
1
0
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
3455 G01
3455 G02
3455 G03
3455fc
4
LTC3455/LTC3455-1
TYPICAL PERFORMANCE CHARACTERISTICS
Feedback Pins (FB1, FB2)
and AI Pin Voltage
815
SWITCHING FREQUENCY (MHz)
810
805
800
FB2
795
790
785
–50 –25
AI
2.0
Switching Regulator Oscillator
Frequency
1000
Switching Regulator Current Limit
SWITCHER 2
800
VOLTAGE (mV)
FOR BOTH SWITCHERS
1.0
CURRENT LIMIT (mA)
1.5
600
SWITCHER 1
FB1
400
0.5
200
50
25
75
0
TEMPERATURE (°C)
100
125
0
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
0
–50 –25
50
25
75
0
TEMPERATURE ( C)
100
125
3455 G04
3455 G05
3455 G06
USB Pin Current Limit
500
USBHP = 2V
V
MAX
CURRENT LIMIT (A)
USB PIN CURRENT (mA)
400
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
USBHP = 0V
0
–50 –25
V
USB
= 5V
50
25
75
0
TEMPERATURE (°C)
100
125
0.5
V
MAX
Pin Current Limit
200
HSO PIN CURRENT LIMIT (mA)
NORMAL OPERATION
HSO Pin Current Limit
150
300
100
200
100
STARTUP
50
V
HSI
= 3.3V
V
HSO
= 2.5V
50
25
75
0
TEMPERATURE (°C)
100
125
0
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
0
–50 –25
3455 G07
3455 G08
3455 G09
Battery Undervoltage Lockout
4.00
3.75
BATTERY UVLO (V)
3.50
3.25
RISING
3.00
2.75
FALLING
2.50
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
4.00
3.75
USB Undervoltage Lockout
1.26
1.24
RISING
USB UVLO (V)
3.50
3.25
3.00
2.75
2.50
–50 –25
FALLING
WALLFB TRIP VOLTAGE (V)
WALLFB Trip Voltage
RISING
1.22
1.20
1.18
1.16
1.14
1.12
FALLING
50
25
75
0
TEMPERATURE (°C)
100
125
1.10
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
3455 G10
3455 G11
3455 G12
3455fc
5
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