FEATURES
s
s
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LTC3455
Dual DC/DC Converter
with USB Power Manager
and Li-Ion Battery Charger
DESCRIPTIO
The LTC
®
3455 is a complete power management solution
for a variety of portable applications. The device contains
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 provides 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 dis-
charged to ground during shutdown to provide complete
output disconnect. The device is available in a
4mm
×
4mm 24-pin exposed-pad QFN package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
*U.S. Patent 6,522,118
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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
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
×
0.8mm 24-Pin
QFN Package
APPLICATIO S
s
s
s
Handheld Computers
Digital Cameras
MP3 Players
TYPICAL APPLICATIO
USB 5V
1Ω
4.7µF
WALL 5V
1Ω
1µF
10µF
3.32k
1k
4
11
0.1µF
1.24k
2.49k
9
4.7µF
SINGLE
CELL Li-ION
3.3V TO 4.2V
V
BAT
3
2
TIMER
PROG
CHRG
WALLFB
USB
CONTROLLER
8
6
5
10
USB
SUSPEND
USBHP
V
MAX
MODE
HSON
ON2
PWRON
RST
PBSTAT
LTC3455
21
15
19
22
20
23
1M
24
14
1M
1.8V
ON/OFF
3.3V, HS
1µF
µC
100
95
90
EFFICIENCY (%)
85
80
75
70
65
60
1.8V
0.4A
10µF
80.6k
SWITCHER 2
V
OUT2
= 3.3V
ON
HSO
HSI
SW2
FB2
13
12
18
4.7µH
10pF
249k
3.3V
0.5A
10µF
80.6k
+
1.8V
1M
LBO
V
BAT
2.49M
16
806k
AI
17
AO
V
BAT
= 3.6V
1
10
100
LOAD CURRENT (mA)
1000
3455 TA01b
SW1
FB1
GND
3455 TA01a
7
1
25
4.7µH
10pF
100k
U
U
U
Efficiency
SWITCHER 1
V
OUT1
= 1.8V
3455f
1
LTC3455
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
PBSTAT
PWRON
MODE
ON2
RST
ON
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
ORDER PART
NUMBER
18 FB2
17 AO
24 23 22 21 20 19
FB1 1
PROG 2
TIMER 3
CHRG 4
USBHP 5
SUSPEND 6
7
SW1
LTC3455EUF
UF PART
MARKING
3455
25
16 AI
15 HSON
14 HSO
13 HSI
8
USB
9 10 11 12
WALLFB
V
MAX
V
BAT
SW2
UF PACKAGE
24-LEAD (4mm
×
4mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 36°C/W,
θ
JC
= 2.5°C/W
EXPOSED PAD (PIN 25) IS GND
MUST BE SOLDERED TO PCB
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
q
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.
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
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
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
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
V
BAT
Rising
MIN
2.9
TYP
3.0
450
MAX
3.2
UNITS
V
mV
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
160
800
20
20
4
1.0
1.0
1.0
1.0
1.26
WALLFB Rising
q
1.20
1.23
60
2.5
2.5
2.5
2.5
±1
0.02
0.20
0.02
0.20
200
±30
0.10
0.35
0.10
0.35
2
U
µA
µA
µA
µA
µA
V
V
V
V
V
mV
µA
µA
µA
µA
nA
V
V
V
V
ms
3455f
W
U
U
W W
W
LTC3455
The
q
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.
PARAMETER
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
Hot Swap Output
Hot Swap PMOS Switch On-Resistance
Hot Swap PMOS Switch Current Limit
HSON Pin Threshold
HSON Pin Pulldown Current
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
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
q
q
q
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
TYP
0.15
MAX
UNITS
Ω
A
A
2.5
With V
MAX
Rising, V
MAX
= 3V, V
BAT
= 3.6V
0.4
0.784
–8
q
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
q
±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
1200
4.10
mA
mA
V
mV
V
Ω
500
100
20
1.1
1.1
mA
mA
µA
V
V
µA
µA
3455f
3
LTC3455
The
q
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
ON
= 0V,
V
USB
= 0V, V
WALLFB
= 0V unless otherwise noted.
PARAMETER
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:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
The LTC3455 is guaranteed to meet specified performance from
0°C to 70°C and is designed, characterized and expected to meet these
extended temperature limits, but is not tested at –40°C and 85°C
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
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
425
4.158
4.200
400
50
500
150
2.85
60
65
2
1.23
0.75
±10
105
4.242
470
90
575
V
mA
mA
mA
mV
V
mV
mA
µA
V
V
%
°C
CONDITIONS
MIN
TYP
MAX
UNITS
ELECTRICAL CHARACTERISTICS
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 PERFOR A CE CHARACTERISTICS
Burst Mode Quiescent Current
120
100
BOTH SWITCHERS ENABLED
600
BOTH SWITCHERS ENABLED
500
QUIESCENT CURRENT (µA)
QUIESCENT CURRENT (µA)
ONLY SWITCHER 1 ENABLED
80
60
40
20
0
–50 –25
V
BAT
= 3.6V
NOT SWITCHING
50
25
75
0
TEMPERATURE (°C)
100
125
400
300
200
100
0
–50 –25
ONLY SWITCHER 1 ENABLED
QUIESCENT CURRENT (µA)
4
U W
3455 G01
PWM Mode Quiescent Current
5
Shutdown Quiescent Current
V
BAT
= 3.6V
4
3
2
1
V
BAT
= 3.6V
NOT SWITCHING
50
25
75
0
TEMPERATURE (°C)
100
125
0
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
3455 G02
3455 G03
3455f
LTC3455
TYPICAL PERFOR A CE CHARACTERISTICS
Feedback Pins (FB1, FB2)
and AI Pin Voltage
815
2.0
SWITCHING FREQUENCY (MHz)
810
805
800
FB2
795
790
785
–50 –25
AI
VOLTAGE (mV)
FOR BOTH SWITCHERS
1.0
CURRENT LIMIT (mA)
FB1
50
25
75
0
TEMPERATURE (°C)
USB Pin Current Limit
500
USBHP = 2V
5.0
4.5
V
MAX
CURRENT LIMIT (A)
400
USB PIN CURRENT (mA)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
STARTUP
HSO PIN CURRENT LIMIT (mA)
300
200
100
USBHP = 0V
0
–50 –25
V
USB
= 5V
50
25
75
0
TEMPERATURE (°C)
100
125
Battery Undervoltage Lockout
4.00
3.75
BATTERY UVLO (V)
RISING
FALLING
WALLFB TRIP VOLTAGE (V)
USB UVLO (V)
3.50
3.25
RISING
3.00
2.75
FALLING
2.50
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
U W
100
3455 G04
3455 G07
3455 G10
Switching Regulator Oscillator
Frequency
1000
Switching Regulator Current Limit
SWITCHER 2
1.5
800
600
SWITCHER 1
400
0.5
200
125
0
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
0
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
3455 G05
3455 G06
V
MAX
Pin Current Limit
200
NORMAL OPERATION
HSO Pin Current Limit
150
100
50
V
HSI
= 3.3V
V
HSO
= 2.5V
50
25
75
0
TEMPERATURE (°C)
100
125
0.5
0
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
0
–50 –25
3455 G08
3455 G09
USB Undervoltage Lockout
4.00
3.75
3.50
3.25
3.00
2.75
2.50
–50 –25
1.26
1.24
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 G11
3455 G12
3455f
5
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