LTC3455
1
3455f
APPLICATIO S
U
FEATURES
TYPICAL APPLICATIO
U
DESCRIPTIO
U
LOAD CURRENT (mA)
60
EFFICIENCY (%)
80
75
70
65
85
90
95
100
3455 TA01b
V
BAT
= 3.6V
SWITCHER 1
V
OUT1
= 1.8V
SWITCHER 2
V
OUT2
= 3.3V
1
10
100
1000
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.
s
Handheld Computers
s
Digital Cameras
s
MP3 Players
, LTC and LT are registered trademarks of Linear Technology Corporation.
s
Seamless Transition between Input Power Sources:
Li-Ion Battery, USB, and 5V Wall Adapter
s
Accurate USB Current Limiting (500mA/100mA)
s
Two High Efficiency DC/DC Converters: Up to 96%
s
Thermal Regulation Maximizes Battery Charge
Rate without Risk of Overheating*
s
Full-Featured Li-Ion Battery Charger
s
Hot SwapTM Output for SDIO and Memory Cards
s
Pin-Selectable Burst Mode
Operation
s
Output Disconnect: All Outputs Discharged to
Ground During Shutdown
s
Available in a 4mm
4mm
0.8mm 24-Pin
QFN Package
Efficiency
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
11
10
13
14
1
1
F
1
F
10
F
4.7
F
WALL 5V
3.3V, HS
8
6
5
9
1
4.7
F
USB 5V
4
2
3
18
12
249k
4.7
H
80.6k
10pF
10
F
3.3V
0.5A
1
7
100k
4.7
H
80.6k
10pF
10
F
1.8V
0.4A
16
17
LBO
24
23
20
21
19
22
15
0.1
F
1k
806k
1M
1.8V
V
BAT
2.49M
1M
2.49k
1M
1.8V
25
3455 TA01a
C
USB
CONTROLLER
SINGLE
CELL Li-ION
3.3V TO 4.2V
1.24k
3.32k
ON/OFF
+
WALLFB
HSI
HSO
V
MAX
USB
SUSPEND
USBHP
SW2
FB2
SW1
FB1
TIMER
PROG
AI
AO
V
BAT
ON
GND
CHRG
PBSTAT
RST
MODE
LTC3455
ON2
PWRON
HSON
Dual DC/DC Converter
with USB Power Manager
and Li-Ion Battery Charger
LTC3455
2
3455f
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
UF PART
MARKING
T
JMAX
= 125
C,
JA
= 36
C/W,
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.
3455
LTC3455EUF
ABSOLUTE AXI U
RATI GS
W
W
W
U
PACKAGE/ORDER I FOR ATIO
U
U
W
(Note 1)
ELECTRICAL CHARACTERISTICS
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
CONDITIONS
MIN
TYP
MAX
UNITS
Battery Undervoltage Lockout Voltage
V
BAT
Rising
2.9
3.0
3.2
V
Battery Undervoltage Lockout Hysteresis
450
mV
V
BAT
Pin Quiescent Current (Note 3)
Burst Mode,
Battery Powered
V
ON2
= V
MODE
= 1V, Not Switching
110
160
A
PWM Mode, Battery Powered
V
ON2
= 1V, V
MODE
= 0V, Not Switching
500
800
A
USB Powered
V
USB
= 5V, Charger Off
10
20
A
Wall Powered
V
WALL
= 1.5V, V
MAX
= 4.5V, Charger Off
10
20
A
Shutdown
V
PWRON
= 0V, V
MAX
= 0V
2
4
A
ON Pin Threshold
0.8
1.0
V
PWRON Pin Threshold
0.8
1.0
V
ON2 Pin Threshold
0.8
1.0
V
MODE Pin Threshold
0.8
1.0
V
WALLFB Pin Threshold Voltage
WALLFB Rising
q
1.20
1.23
1.26
V
WALLFB Pin Hysteresis
60
mV
ON Pin Pullup Current
V
ON
= 1V
2.5
A
PWRON Pin Pulldown Current
V
PWRON
= 1V
2.5
A
ON2 Pin Pulldown Current
V
ON2
= 1V
2.5
A
MODE Pin Pullup Current
V
MODE
= 1V
2.5
A
WALLFB Pin Input Bias Current
V
WALLFB
= 1.35V
q
1
30
nA
PBSTAT Pin Low Voltage
V
ON
= 0V, I
PBSTAT
= 100
A
0.02
0.10
V
V
ON
= 0V, I
PBSTAT
= 1mA
0.20
0.35
V
RST Pin Low Voltage
I
RST
= 100
A
0.02
0.10
V
I
RST
= 1mA
0.20
0.35
V
RST Pulse Duration
After FB1 and FB2 in Regulation
200
ms
24
25
23 22 21 20 19
7
8
9
TOP VIEW
UF PACKAGE
24-LEAD (4mm
4mm) PLASTIC QFN
10 11 12
6
5
4
3
2
1
13
14
15
16
17
18
FB1
PROG
TIMER
CHRG
USBHP
SUSPEND
FB2
AO
AI
HSON
HSO
HSI
ON
PBSTAT
PWRON
MODE
RST
ON2
SW1
USB
V
BAT
V
MAX
WALLFB
SW2
LTC3455
3
3455f
ELECTRICAL CHARACTERISTICS
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
CONDITIONS
MIN
TYP
MAX
UNITS
Battery-V
MAX
PMOS
V
MAX
PMOS Switch On-Resistance
0.15
V
MAX
Switch Current Limit
2.5
4.0
A
V
MAX
Switch Current Limit at Startup
With V
MAX
Rising, V
MAX
= 3V, V
BAT
= 3.6V
0.4
0.9
A
Gain Block
AI Pin Threshold Voltage
q
0.784
0.805
0.826
V
AI Pin/FB2 Pin Voltage Difference
V
FB2
V
AI
8
0
8
mV
AI Pin Input Bias Current
V
AI
= 0.85V
q
1
25
nA
AO Pin Sink Current
V
AI
= 0.6V, V
AO
= 1.5V
1.0
1.8
2.5
mA
AO Pin Voltage
V
AI
= 0.6V, I
AO
= 1mA
0.8
1.2
V
Switching Regulators
FB1, FB2 Voltage
q
0.784
0.805
0.826
V
FB1, FB2 Voltage Line Regulation
V
MAX
= 3V to 5V
0.01
%/V
FB1, FB2 Voltage Burst Mode Hysteresis
V
MODE
= 2V
8
mV
FB1, FB2 Pin Input Bias Current
V
FB1
= V
FB2
= 0.85V
q
1
25
nA
Switching Frequency
Both Switchers
1.2
1.5
1.8
MHz
PMOS Switch On-Resistance
Both Switchers
0.35
NMOS Switch On-Resistance
Both Switchers
0.45
PMOS Switch Current Limit
Switcher 1
450
600
850
mA
Switcher 2
700
900
1200
mA
USB Power Manager
USB Undervoltage Lockout Voltage
From Low to High
3.75
3.90
4.10
V
USB Undervoltage Lockout Hysteresis
150
mV
USB Minimum Voltage to Charge Battery
4.0
V
USB PMOS Switch On-Resistance
V
USB
= 5V
0.5
USB Current Limit
V
USB
= 5V, V
USBHP
= 2V
q
440
475
500
mA
V
USB
= 5V, V
USBHP
= 0V
q
60
80
100
mA
USB Suspend Mode Bias Current
V
USB
= 5V, V
SUSPEND
= 2V
4
20
A
SUSPEND Pin Threshold
0.8
1.1
V
USBHP Pin Threshold
0.8
1.1
V
SUSPEND Pin Pulldown Current
V
SUSPEND
= 0.5V
2.5
A
USBHP Pin Pulldown Current
V
USBHP
= 0.5V
2.5
A
Hot Swap Output
Hot Swap PMOS Switch On-Resistance
V
HSI
= 3.3V
0.9
Hot Swap PMOS Switch Current Limit
V
HSI
= 3.3V, V
HSO
= 2.5V
120
160
mA
HSON Pin Threshold
0.8
1.1
V
HSON Pin Pulldown Current
2.5
A
LTC3455
4
3455f
ELECTRICAL CHARACTERISTICS
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.
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
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.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Battery Charger
Regulated Charger V
BAT
Voltage
0
C
T
A
85
C
4.158
4.200
4.242
V
Charger Current Limit (USB Powered)
R
PROG
=2.49k
, V
USBHP
= 2V, V
USB
= 5V, 0
C
T
A
85
C
400
470
mA
R
PROG
=2.49k
, V
USBHP
= 0V, V
USB
= 5V, 0
C
T
A
85
C
50
90
mA
Charger Current Limit (Wall Powered)
R
PROG
=2.49k
, V
MAX
= 4.5V, 0
C
T
A
85
C
425
500
575
mA
Recharge Battery Voltage Threshold
V
BAT(REGULATED)
V
RECHARGE
150
mV
Trickle Charge Trip Threshold
Battery Voltage Rising
2.85
V
Trickle Charge Trip Hysteresis
60
mV
Trickle Charge Current
R
PROG
=2.49k
, V
BAT
= 2V
65
mA
PROG Pin Current
Internal Pull-Up Current, No R
PROG
2
A
PROG Pin Voltage
R
PROG
=2.49k
1.23
V
CHRG Pin Output Low Voltage
I
CHRG
= 5mA
0.75
V
Timer Accuracy
C
TIMER
= 0.1
F
10
%
Junction Temperature in
105
C
Constant Temperature Mode
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Burst Mode Quiescent Current
PWM Mode Quiescent Current
Shutdown Quiescent Current
TEMPERATURE (
C)
50
QUIESCENT CURRENT (
A)
120
100
80
60
40
20
0
25
75
3455 G01
25
0
50
100
125
V
BAT
= 3.6V
NOT SWITCHING
BOTH SWITCHERS ENABLED
ONLY SWITCHER 1 ENABLED
TEMPERATURE (
C)
50
QUIESCENT CURRENT (
A)
600
500
400
300
200
100
0
25
75
3455 G02
25
0
50
100
125
BOTH SWITCHERS ENABLED
ONLY SWITCHER 1 ENABLED
V
BAT
= 3.6V
NOT SWITCHING
TEMPERATURE (
C)
50
QUIESCENT CURRENT (
A)
5
4
3
2
1
0
25
75
3455 G03
25
0
50
100
125
V
BAT
= 3.6V
LTC3455
5
3455f
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Feedback Pins (FB1, FB2)
and AI Pin Voltage
Switching Regulator Oscillator
Frequency
Switching Regulator Current Limit
USB Pin Current Limit
V
MAX
Pin Current Limit
HSO Pin Current Limit
Battery Undervoltage Lockout
USB Undervoltage Lockout
WALLFB Trip Voltage
TEMPERATURE (
C)
50
USB PIN CURRENT (mA)
500
400
300
200
100
0
25
75
3455 G07
25
0
50
100
125
USBHP = 2V
USBHP = 0V
V
USB
= 5V
TEMPERATURE (
C)
50
HSO PIN CURRENT LIMIT (mA)
200
150
100
50
0
25
75
3455 G09
25
0
50
100
125
V
HSI
= 3.3V
V
HSO
= 2.5V
TEMPERATURE (
C)
50
SWITCHING FREQUENCY (MHz)
2.0
1.5
1.0
0.5
0
25
75
3455 G05
25
0
50
100
125
FOR BOTH SWITCHERS
TEMPERATURE (
C)
50
CURRENT LIMIT (mA)
1000
800
600
400
200
0
25
75
3455 G06
25
0
50
100
125
SWITCHER 1
SWITCHER 2
TEMPERATURE (
C)
50
VOLTAGE (mV)
815
810
805
800
795
790
785
25
75
3455 G04
25
0
50
100
125
FB1
AI
FB2
TEMPERATURE (
C)
50
V
MAX
CURRENT LIMIT (A)
5.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0
25
75
3455 G08
25
0
50
100
125
STARTUP
NORMAL OPERATION
TEMPERATURE (
C)
50
BATTERY UVLO (V)
4.00
3.75
3.50
3.25
3.00
2.75
2.50
25
75
3455 G10
25
0
50
100
125
FALLING
RISING
TEMPERATURE (
C)
50
USB UVLO (V)
4.00
3.75
3.50
3.25
3.00
2.75
2.50
25
75
3455 G11
25
0
50
100
125
FALLING
RISING
TEMPERATURE (
C)
50
WALLFB TRIP VOLTAGE (V)
1.26
1.24
1.22
1.20
1.18
1.16
1.14
1.12
1.10
25
75
3455 G12
25
0
50
100
125
FALLING
RISING
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