LTC4055EUF-1#PBF [Linear]
LTC4055/LTC4055-1 - USB Power Controller and Li-Ion Linear Charger; Package: QFN; Pins: 16; Temperature Range: -40°C to 85°C;
| 型号： | LTC4055EUF-1#PBF |
| 厂家： | 
Linear |
| 描述： | LTC4055/LTC4055-1 - USB Power Controller and Li-Ion Linear Charger; Package: QFN; Pins: 16; Temperature Range: -40°C to 85°C |
| 文件： | 总24页 (文件大小：292K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC4055/LTC4055-1
USB Power Controller
and Li-Ion Charger
FEATURES
DESCRIPTION
The LTC®4055/LTC4055-1 are USB power manager and
Li-Ion battery chargers designed to work in portable
battery-powered applications. The parts manage and limit
the total current used by the USB peripheral for operation
andbatterycharging.Dependingonthestateofthecurrent
select pin (HPWR), total input current can be limited to
either 100mA or 500mA. The voltage drop from the USB
supplyorbatterytotheUSBperipheralistypicallylessthan
100mV at 400mA and 20mV at 80mA. Other management
features include: automatic switchover to battery when
input is removed, inrush current limiting, reverse current
blocking, undervoltage lockout and thermal shutdown.
n
Charges Single-Cell Li-Ion Batteries Directly from
USB Port
n
Load Dependent Charging Guarantees USB Input
Current Compliance
n
Automatic Battery Switchover When Input Supply is
Removed
n
Constant-Current/Constant-Voltage Operation with
Thermal Feedback to Maximize Charging Rate
Without Risk of Overheating*
n
Selectable 500mA/100mA Current Limit
n
™
Low Loss Full PowerPath Control with Ideal Diode
Operation (Reverse Current Blocking)
n
Preset 4.2V Charge Voltage with 0.8% Accuracy
The LTC4055/LTC4055-1 include a complete constant-
current/constant-voltage linear charger for single-cell
Li-ion batteries. The float voltage applied to the battery
is held to a tight 0.8% tolerance, and charge current is
programmable using an external resistor to ground. Fully
discharged cells are automatically trickle charged at 10%
of the programmed current until the cell voltage exceeds
2.8V. Total charge time is programmable by an external
capacitortoground.Whenthebatterydrops100mVbelow
the float voltage, automatic recharging of the battery
occurs. Also featured is an NTC thermistor input used to
monitor battery temperature while charging.
(4.1V for LTC4055-1)
n
4.1V Float Voltage (LTC4055-1) Improves Battery Life
and High Temperature Safety Margin
USB-Compliant Suspend Mode
n
n
Programmable Charge Current and Termination Timer
n
Soft-Start Limits Inrush Current
n
NTC Thermistor Input for Temperature Qualified
Charging
n
Tiny (4mm × 4mm × 0.75mm) QFN Package
APPLICATIONS
n
Portable USB Devices: Cameras, MP3 Players, PDAs
The LTC4055/LTC4055-1 are available in a 16-pin low
profile (4mm × 4mm) QFN package.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. *Protected by U.S. Patent, including 6522118.
TYPICAL APPLICATION
Input and Battery Current vs Load Current
RPROG = RCLPROG = 97.6k
600
5V (NOM)
I
IN
TO SYSTEM
LOADS
FROM USB
IN1
IN2
OUT
BAT
500
400
300
200
100
0
CABLE V
BUS
10μF
1Ω
10μF
+
Li-Ion
CELL
V
NTC
I
LOAD
NTC
LTC4055
WALL
SHDN
SUSP
HPWR
CHRG
ACPR
I
BAT
CHARGING
SUSPEND USB POWER
500mA/100mA SELECT
TIMER PROG CLPROG
GND
I
BAT
(IDEAL DIODE)
0.1μF
97.6k 97.6k
–100
0
100
200
300
(mA)
400
500
600
4055 TA01
4055 TA02
I
LOAD
4055fb
1
LTC4055/LTC4055-1
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Notes 1, 2, 3, 4, 5)
Terminal Voltage
TOP VIEW
IN1, IN2, OUT, BAT.................................. –0.3V to 6V
NTC, V , TIMER,
NTC
16 15 14 13
PROG, CLPROG..................... –0.3V to (VCC + 0.3V)
IN2
BAT
OUT
IN1
1
2
3
4
12 TIMER
11 PROG
CHRG, HPWR, SUSP, SHDN,
17
GND
10
9
WALL, ACPR........................................... –0.3V to 6V
CLPROG
IN2........................................................... V + 0.1V
IN1
5
6
7
8
Pin Current (DC)
IN1, IN2, OUT, BAT (Note 7) ............................... 1.6A
Operating Temperature Range................. –40°C to 85°C
Maximum Operating Junction Temperature ......... 125°C
Storage Temperature Range.................. –65°C to 125°C
UF PACKAGE
16-LEAD (4mm s 4mm) PLASTIC QFN
T
= 125°C, θ = 37°C/W
JA
JMAX
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC4055EUF#PBF
LTC4055EUF-1#PBF
TAPE AND REEL
PART MARKING
4055
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC4055EUF#TRPBF
LTC4055EUF-1#TRPBF
–40°C to 85°C
–40°C to 85°C
16-Lead (4mm × 4mm) Plastic QFN
16-Lead (4mm × 4mm) Plastic QFN
40551
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 The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN1 = VIN2 = 5V, VBAT = 3.5V, HPWR = 5V, WALL = 0V,
RPROG = RCLPROG = 100k, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
IN1, IN2 and OUT
BAT
MIN
TYP
MAX
5.5
UNITS
l
l
V
V
Input Supply Voltage
Input Voltage
4.35
V
V
IN
4.3
BAT
l
l
l
l
I
IN
Input Supply Current
V
= 4.2V
0.8
50
0.1
10
1.6
100
0.2
20
mA
μA
mA
μA
BAT
Suspend Mode
Suspend Mode, Wall = 2V, V
Shutdown
= 4.8V
OUT
l
I
I
Output Supply Current
Battery Drain Current
V
V
= 5V, V = V = 0V, V = 4.2V
450
900
μA
OUT
OUT
IN1
IN2
BAT
l
l
l
l
= 4.2V, Charging Stopped
15
15
2.5
50
30
30
5
μA
μA
μA
μA
BAT
BAT
Suspend Mode
Shutdown
V
= V = 0V, BAT Powers OUT, No Load
100
IN1
IN2
I
Maximum Current Limit
(Note 8)
1
A
LIM(MAX)
l
l
V
Input or Output Undervoltage Lockout
V
V
Powers Part, Rising Threshold
OUT
3.5
3.5
3.8
3.8
4
4
V
V
UVLO
IN
Powers Part, Rising Threshold
ΔV
UVLO
Input or Output Undervoltage Lockout
Hysteresis
V
V
Rising – V Falling or
OUT
125
mV
IN
IN
Rising – V
Falling
OUT
4055fb
2
LTC4055/LTC4055-1
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN1 = VIN2 = 5V, VBAT = 3.5V, HPWR = 5V, WALL = 0V,
RPROG = RCLPROG = 100k, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Current Limit
l
l
I
Current Limit
R
R
= 100k, HPWR = 5V
= 100k, HPWR = 0V
465
89
490
97
515
105
mA
mA
LIM
CLPROG
CLPROG
R
ON
ON Resistance V to V
OUT
HPWR = 5V, 400mA Load
HPWR = 0V, 80mA Load
0.2
0.2
Ω
Ω
IN
l
l
V
Programming Pin Voltage
(PROG, CLPROG)
R
R
= R
= R
= 100k
= 50k
0.98
0.98
1.000
1.000
1.02
1.02
V
V
PROG
CLPROG
CLPROG
PROG
PROG
I
V
ΔV
Soft-Start Inrush Current
Input Current Limit Enable Threshold
Input Current Limit Enable Threshold
IN or OUT
5
3.8
125
mA/μs
V
SS
l
V
IN
V
IN
Rising
Rising – V Falling
3.5
4
CLEN
mV
CLEN
IN
V
ALEN
Automatic Limit Enable Threshold
Voltage
(V – V ) V Rising
25
–75
50
–50
75
–25
mV
mV
IN
OUT IN
(V – V ) V Falling
IN
OUT IN
Battery Charger
V
FLOAT
Regulated BAT Voltage
(0°C to 85°C) I = 2mA (LTC4055)
BAT
4.165
4.158
4.066
4.059
4.200
4.200
4.100
4.100
4.235
4.242
4.134
4.141
V
V
V
V
BAT
l
l
I
= 2mA (LTC4055)
(0°C to 85°C). I = 2mA (LTC4055-1)
BAT
I
= 2mA (LTC4055-1)
BAT
l
l
l
I
Current Mode Charge Current
R
R
R
= 100k, HPWR = 5V, No Load
= 100k, HPWR = 0V, No Load
445
45
485
80
525
110
525
mA
mA
mA
BAT
PROG
PROG
PROG
= 100k, V
= 2V
= 5V, V = 0V,
445
485
OUT
IN
V
WALL
l
l
R
= 50k, HPWR = 5V, No Load
900
900
980
980
1060
1060
mA
mA
PROG
PROG
R
= 50k, V
= 2V
= 5V, V = 0V,
OUT IN
V
WALL
I
Maximum Charge Current
Charge Current Load Dependency
Trickle-Charge Current
(Note 8)
ΔI /ΔI , I
BAT OUT OUT
1
1
45
2.85
A
mA/mA
mA
BAT(MAX)
l
l
ΔI /ΔI
= 100mA
= 100k
PROG
0.95
30
2.7
1.05
60
3
B
O
I
V
BAT
V
BAT
= 2V, R
Rising
TRKL
V
Trickle-Charge Threshold Voltage
V
TRKL
V
CENI
Input Charger Enable Threshold
Voltage
(V – V ) High to Low
70
80
mV
mV
IN
BAT
(V – V ) Low to High
IN
BAT
V
Output Charger Enable Threshold
Voltage
(V
(V
– V ) High to Low
70
80
mV
mV
CENO
OUT
OUT
BAT
– V ) Low to High
BAT
l
l
V
V
t
Input/Output Undervoltage Current Limit
Recharge Battery Threshold Voltage
TIMER Accuracy
I
V
C
= I /2
4.23
65
4.3
100
10
4.37
135
V
mV
%
UVCL
BAT
CHG
– V
RECHRG
RECHRG
TIMER
FLOAT
TIMER
= 0.1μF
Recharge Time
Low Battery Trickle-Charge Time
Percent of Total Charge Time
Percent of Total Charge Time, V < 2.8V
50
25
%
%
BAT
T
LIM
Junction Temperature in Constant
Temperature Mode
105
°C
Ideal Diode
R
R
V
On Resistance, V Regulation
V
V
= 3.5V, 100mA Load
= 3.5V, 600mA Load
= 3.5V, 5mA Load
= 3.5V, 100mA Load
= 3.5V, 600mA
0.1
0.2
30
55
120
Ω
Ω
mV
mV
mV
FWD
ON
BAT
On Resistance V to V
OUT
DIO,ON
FWD
BAT
BAT
l
Voltage Forward Drop (V – V
)
V
BAT
V
BAT
V
BAT
10
50
BAT
OUT
V
I
I
Diode Disable Battery Voltage
V
V
V
Falling
= 3.5V
= 3.5V, V
10% Duty Cycle
2.8
550
1.8
V
mA
A
OFF
FWD
MAX
BAT
Load Current Limit for V Regulation
ON
IN
Diode Current Limit
= 2.8V, Pulsed with
OUT
1.4
2.2
BAT
4055fb
3
LTC4055/LTC4055-1
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN1 = VIN2 = 5V, VBAT = 3.5V, HPWR = 5V, WALL = 0V,
RPROG = RCLPROG = 100k, unless otherwise noted.
SYMBOL
Logic
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
l
l
V
V
V
Output Low Voltage (CHRG, ACPR)
Enable Input High Voltage
I
= 5mA
0.2
0.4
1.2
V
V
OL
SINK
SUSP, SHDN, HPWR Pin Low to High
SUSP, SHDN, HPWR Pin High to Low
SUSP, SHDN, HPWR
IH
Enable Input Low Voltage
0.4
V
IL
I
Logic Input Pull-Down Current
2
4
μA
V
PULLDN
l
l
l
V
Charger Shutdown Threshold Voltage
on TIMER
TIMER Falling
0.15
2
0.4
CHG,SD
I
Charger Shutdown Pull-Up Current
on TIMER
V
= 0V
μA
CHG,SD
TIMER
V
WALL
Wall Input Threshold Voltage
Wall Input Hysteresis
V
Rising Threshold
0.98
1.000
35
1.02
50
V
mV
nA
WALL
V
V
Rising – V
= 1V
WALL
Falling Threshold
WALL,HYS
WALL
WALL
I
Wall Input Leakage Current
V
0
WALL
NTC
l
l
I
V
V
Pin Current
Bias Voltage
V = 2.5V
VNTC
1.5
3.4
2.5
3.8
3.5
mA
V
VNTC
NTC
V
I
= 500μA
VNTC
VNTC
NTC
V
V
V
Cold Temperature Fault Threshold
Voltage
Rising Threshold
Falling Threshold
0.74 • V
0.72 • V
V
V
COLD
HOT
DIS
VNTC
VNTC
Hot Temperature Fault Threshold
Voltage
Falling Threshold
Rising Threshold
0.29 • V
0.30 • V
V
V
VNTC
VNTC
l
NTC Disable Voltage
NTC Input Voltage to GND (Falling)
Hysteresis
75
100
50
125
mV
mV
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 6: The LTC4055EUF/LTC4055EUF-1 are guaranteed to meet
performance specifications from 0°C to 85°C. Specifications over the
–40°C to 85°C operating temperature range are assured by design,
characterization and correlation with statistical process controls.
Note 2: V is the greater of V , V
or V
.
BAT
Note 7: Guaranteed by long-term current density limitations.
CC
IN1 OUT
Note 3: IN1 and IN2 should be tied together with a low impedance to
ensure that the difference between the two pins does not exceed 100mV.
Note 8: Accuracy of programmed current may degrade for currents greater
than 1A.
Note 4: All voltage values are with respect to GND.
Note 5: This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
4055fb
4
LTC4055/LTC4055-1
TYPICAL PERFORMANCE CHARACTERISTICS
Battery Drain Current
vs Temperature
Input Supply Current
vs Temperature
Input Supply Current
vs Temperature (Suspend Mode)
(BAT Powers OUT, No Load)
70
60
50
40
30
20
10
0
900
800
700
600
500
400
300
200
100
V
V
= 0V
BAT
V
V
= 5V
V
V
= 5V
IN
IN
IN
= 4.2V
= 4.2V
= R
= 4.2V
= R
BAT
BAT
60
50
40
30
20
10
0
R
= 100k
CLPROG
R
= 100k
CLPROG
PROG
PROG
SUSP = 5V
0
50
TEMPERATURE (°C)
100
–50 –25
0
25
75
–50
0
25
50
75
100
–25
–50
–25
0
25
75
100
50
TEMPERATURE (°C)
TEMPERATURE (°C)
4055 G03
4055 G02
4055 G01
Input Current Limit
vs Temperature, HPWR = 5V
Input Current Limit
vs Temperature, HPWR = 0V
RON vs Temperature
515
505
495
485
475
465
105.0
102.5
100.0
97.5
250
225
200
175
V
V
= 5V
I
= 400mA
V
V
= 5V
IN
LOAD
IN
= 3.5V
= R
= 3.5V
= R
BAT
BAT
R
= 100k
CLPROG
R
= 100k
CLPROG
PROG
PROG
V
IN
= 5V
V
IN
= 4.5V
V
= 5.5V
IN
95.0
92.5
90.0
150
125
100
50
TEMPERATURE (°C)
100 125
50
100 125
50
75 100 125
–50 –25
0
25
75
–50 –25
0
25
75
–50 –25
0
25
TEMPERATURE (°C)
TEMPERATURE (°C)
4055 G05
4055 G06
4055 G04
CLPROG Pin Voltage
vs Temperature
Battery Regulated Output (Float)
Voltage vs Temperature
PROG Pin Voltage vs Temperature
4.3
4.2
4.1
4.0
1.020
1.015
1.010
1.005
1.020
1.015
1.010
1.005
V
IN
= 5V
V
= 5V
PROG
V
R
= 5V
IN
CLPROG
IN
R
= 100k
= 100k
LTC4055
1.000
0.995
1.000
0.995
LTC4055-1
0.990
0.985
0.980
0.990
0.985
0.980
–25
0
50
–25
0
50
–25
0
50
–50
75
100
–50
75
100
–50
75
100
25
25
25
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (oC)
4055 G07
4055 G08
4055 G09
4055fb
5
LTC4055/LTC4055-1
TYPICAL PERFORMANCE CHARACTERISTICS
Regulated Output Voltage-
Recharge Threshold Voltage
vs Temperature
Battery Regulated Output (Float)
Voltage vs Supply Voltage
Battery Current and Voltage
vs Time (LTC4055)
4.3
4.2
4.1
4.0
600
500
6
5
120
115
110
105
T
= 25°C
V
IN
= 5V
A
CHRG
V
BAT
LTC4055
400
300
4
3
100
95
LTC4055-1
200
100
0
2
1
0
0.8AHr CELL
= 5V
I
90
85
80
BAT
V
IN
T
= 25°C
A
R
= 105k
PROG
–25
0
50
4.75
5
5.5
–50
75
100
4.5
5.75
6
0
20 40 60 80 100 120 140 160 180 200
TIME (MINUTES)
25
5.25
TEMPERATURE (°C)
V
IN
(V)
4055 G10
4055 G11
4055 G12
Undervoltage Current Limit,
Charging from VIN, IBAT vs VIN
Charging from USB, IBAT
vs VBAT (LTC4055)
Charging from USB, Low Power,
IBAT vs VBAT (LTC4055)
600
500
100
80
1.6
V
V
R
R
= 5V
V
V
R
R
= 5V
T
= 25°C
IN
OUT
IN
OUT
A
= NO LOAD
= 100k
= NO LOAD
= 100k
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
PROG
CLPROG
PROG
CLPROG
R
= 34k
PROG
= 100k
= 100k
HPWR = 1
= 25°C
HPWR = 0
T = 25°C
A
R
= 50k
400
PROG
T
A
60
300
200
40
20
0
R
= 100k
= 100k
PROG
100
0
R
PROG
HPWR = 0
0
0.5
1
1.5
2
2.5
(V)
3
3.5
4
4.5
0
0.5
1
1.5
2
V
BAT
2.5
(V)
3
3.5
4
4.5
4.340
4.260
4.300
4.380
4.420
V
BAT
V
IN
(V)
4055 G13
4055 G14
4055 G15
Ideal Diode Forward Voltage and
Resistance vs Current
Charge Current vs Temperature
(Thermal Regulation)
Ideal Diode Forward Voltage
vs Current and Temperature
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1000
900
800
700
600
500
400
300
200
100
0
1000
V
V
A
= 3.5V
V
V
= 3.5V
BAT
IN
BAT
IN
25°C
0°C
–50°C
R
= 50k
PROG
900
800
700
600
500
400
300
200
100
0
= 0V
= 0V
T
= 25°C
125°C
R
= 100k
75°C
PROG
R
DIO(ON)
R
FWD
V
V
JA
= 5V
BAT
= 37°C/W
IN
= 3.5V
Q
50
75 100 125
0
20 40 60 80 100 120 140 160 180 200
(mV)
0
20 40 60 80 100 120 140 160 180 200
(mV)
–50
0
25
–25
TEMPERATURE (°C)
V
FWD
V
FWD
4055 G17
4055 G18
4055 G16
4055fb
6
LTC4055/LTC4055-1
TYPICAL PERFORMANCE CHARACTERISTICS
Ideal Diode and Schottky Diode
Forward Voltage vs Current
Input Connect Waveforms
Input Disconnect Waveforms
1000
900
800
700
600
500
400
300
200
100
0
V
V
T
= 3.5V
BAT
IN
A
= 0V
V
V
IN
IN
= 25°C
5V/DIV
5V/DIV
V
V
OUT
5V/DIV
OUT
5V/DIV
I
IN
I
IN
0.5A/DIV
0.5A/DIV
I
I
BAT
0.5A/DIV
SCHOTTKY
BAT
0.5A/DIV
1ms/DIV
4055 G22
V
I
= 3.5V
= 100mA
V
I
= 3.5V
= 100mA
1ms/DIV
4055 G20
BAT
OUT
BAT
OUT
0
50 100 150 200 250 300 350 400 450
(mV)
V
FWD
4055 G19
WALL Connect Waveforms
(VIN = 0V)
WALL Disconnect Waveforms
(VIN = 0V)
Response to HPWR
WALL
5V/DIV
OUT
WALL
5V/DIV
OUT
HPWR
5V/DIV
5V/DIV
5V/DIV
I
WALL
I
WALL
I
0.5A/DIV
IN
0.5A/DIV
0.5A/DIV
I
I
BAT
BAT
I
BAT
0.5A/DIV
0.5A/DIV
0.5A/DIV
V
I
= 3.5V
1ms/DIV
4055 G25
V
I
= 3.5V
= 50mA
250μs/DIV
4055 G21
V
I
= 3.5V
1ms/DIV
4055 G24
BAT
OUT
R
BAT
OUT
R
BAT
OUT
= 100mA
= 57.6k
= 100mA
= 57.6k
PROG
PROG
WALL Connect Waveforms
(VIN = 5V)
WALL Disconnect Waveforms
(VIN = 5V)
Response to Suspend
WALL
WALL
SUSPEND
5V/DIV
5V/DIV
5V/DIV
I
IN
I
IN
0.5A/DIV
0.5A/DIV
OUT
5V/DIV
I
I
WALL
0.5A/DIV
WALL
0.5A/DIV
I
IN
0.5A/DIV
I
I
BAT
0.5A/DIV
BAT
I
BAT
0.5A/DIV
0.5A/DIV
V
I
= 3.5V
1ms/DIV
4055 G26
V
I
= 3.5V
BAT
1ms/DIV
4055 G27
V
I
= 3.5V
= 50mA
1ms/DIV
4055 G23
BAT
OUT
R
BAT
OUT
= 100mA
= 100mA
OUT
= 57.6k
R
= 57.6k
PROG
PROG
4055fb
7
LTC4055/LTC4055-1
PIN FUNCTIONS
BAT (Pin 2): Connect to a single-cell Li-Ion battery. Used
as an output when charging the battery and as an input
whensupplyingpowertoOUT.WhentheOUTpinpotential
drops below the BAT pin potential, an ideal diode function
SUSP (Pin 7): Suspend Mode Input. Pulling this pin above
1.2V will disable charging from IN1/IN2 and disconnect
the power path from IN1/IN2 to OUT. The supply current
will be reduced to comply with the USB specification for
Suspend mode. The BAT to OUT ideal diode function will
remain active as well as the ability to charge the battery
from OUT. Suspend mode will reset the charge timer if
connects BAT to OUT and prevents V
from dropping
OUT
morethan100mVbelowV .Aprecisioninternalresistor
BAT
divider sets the final float potential on this pin. The internal
resistor divider is disconnected when IN1/IN2 and OUT
are in UVLO.
V
is less than V while in suspend mode. If V
is
OUT
BAT
OUT
kept greater than V , such as when a wall adapter is
BAT
present, the charge timer will not be reset when the part
is put in suspend. A weak pull-down current is internally
applied to this pin to ensure it is low at power-up when
the input is not being driven externally.
OUT (Pin 3): Voltage Output. Used to provide controlled
power to a USB device from either USB V
(IN1/IN2) or
BUS
the battery (BAT) when the USB is not present. Can also
be used as an input for battery charging when the USB
is not present and a wall adaptor is applied to this pin.
Should be bypassed with at least 10μF to GND.
HPWR (Pin 8): High Power Select. Used to control the
amount of current drawn from the USB port. A voltage
greater than 1.2V on the pin will set the current limit to
100% of the current programmed by the CLPROG pin
and 100% of the charge current programmed by the
PROG pin. A voltage less than 0.4V on the pin will set
the current limit to 20% of the current programmed by
the CLPROG pin and decrease battery charge current to
16% of the current programmed by the CLPROG pin. A
weak pull-down current is internally applied to this pin to
ensure it is low at power-up when the input is not being
driven externally.
IN1/IN2(Pin4/Pin1):InputSupply.ConnecttoUSBsupply,
V
. Used as main supply while connected to USB V
BUS
BUS
for power control to a USB device. Input current is limited
to either 20% or 100% of the current programmed by the
CLPROG pin as determined by the state of the HPWR pin.
Charge current (to BAT pin) supplied through the inputs is
set to the current programmed by the PROG pin but will
be limited by the input current limit if set greater than the
input current limit.
Connect IN2 to IN1 with a resistance no greater than
0.05Ω.
CLPROG (Pin 9): Current Limit Program. Connecting
a resistor, R
to ground, programs the input to
CLPROG
WALL (Pin 5): Wall Adapter Present Input. Pulling this pin
above1VwilldisablechargingfromIN1/IN2anddisconnect
the power path from IN1/IN2 to OUT. The ACPR pin will
also be pulled low to indicate that a wall adapter has
been detected. Requires the voltage on IN1/IN2 or OUT
output current limit. The current limit is programmed as
follows:
VCLPROG
RCLPROG
49,000V
RCLPROG
ICL(A) =
• 49,000 =
to be 100mV greater than V and greater than V
to
BAT
UVLO
In USB applications the resistor R
to no less than 105k.
should be set
CLPROG
activate this function.
SHDN (Pin 6): Shutdown Input. Pulling this pin greater
than 1.2V will disable the entire part and place it in a low
supply current mode of operation. All power paths will be
disabled. A weak pull-down current is internally applied
to this pin to ensure it is low at power-up when the input
is not being driven externally.
GND (Pin 10): Ground.
PROG (Pin 11): Charge Current Program. Connecting a
resistor, R , to ground programs the battery charge
PROG
current. The battery charge current is programmed as
follows:
VPROG
RPROG
48,500V
RPROG
ICHG(A) =
• 48,500 =
4055fb
8
LTC4055/LTC4055-1
PIN FUNCTIONS
TIMER(Pin12):TimerCapacitor.PlacingacapacitorC
to GND sets the timer period. The timer period is:
V
(Pin 15): Output Bias Voltage for NTC. A resistor
NTC
TIMER
from this pin to the NTC pin will set up the bias for an
NTC thermistor.
CTIMER •RPROG • 3Hours
tTIMER(Hours) =
NTC (Pin 16): Input to the NTC Thermistor Monitoring
Circuits. Under normal operation, tie a thermistor from
the NTC pin to ground and a resistor of equal value from
NTC to V . When the voltage on this pin is above 0.74
• V
0.1μF •100k
Charge time is increased as charge current is reduced due
to input voltage regulation, load current and current limit
selection (HPWR).
NTC
(Cold, 0°C) or below 0.29 • V
(Hot, 50°C)
VNTC
VNTC
the timer is suspended, but not cleared, the charging is
disabled and the CHRG pin remains in its former state.
When the voltage on NTC comes back between 0.74 •
Shorting the TIMER pin to GND disables the battery
charging functions.
ACPR (Pin 13): Wall Adapter Present Output. Active low
open-drain output pin. A low on this pin indicates that the
wall adapter input comparator has had its input pulled
abovetheinputthresholdandpowerispresentonIN1/IN2
or OUT (i.e., above UVLO threshold).
V
and 0.29 • V
, the timer continues where it
VNTC
VNTC
left off and charging is re-enabled if the battery voltage
is below the recharge threshold. There is approximately
3°C of temperature hysteresis associated with each of the
input comparators.
CHRG (Pin 14): Open-Drain Charge Status Output. When
the battery is being charged, the CHRG pin is pulled low
by an internal N-channel MOSFET. When the timer runs
out or the input supply or output supply is removed, the
CHRG pin is forced to a high impedance state.
If the NTC function is not to be used, connect the NTC to
ground. This will disable all of the LTC4055/LTC4055-1
NTC functions.
Exposed Pad (Pin 17): Ground. The Exposed Pad must be
soldered to a good thermally conductive PCB ground.
4055fb
9
LTC4055/LTC4055-1
BLOCK DIAGRAM
V
BUS
4
3
2
1
IN1
IN1
OUT
BAT
IN2
+
–
IDEAL
DIODE
25mV
0.2Ω
0.2Ω
0.2Ω
BAT IN2
OUT
DIE
TEMP 105°C
4.35V
CURRENT LIMIT
+
+
–
–
TA
VR
SOFT-START
+
–
1V
I
LIM
I
CNTL
LIM
ENABLE
SENSE
CLPROG
SOFT-START2
CURRENT CONTROL
9
CHARGER
CC/CV REGULATOR
I
CHRG
100k
I/O SEL ENABLE
+
–
1V
BATTERY CHARGER
+
PROG
HPWR
11
8
0.25V
–
100k
500mA/100mA
2μ
+
–
2.8V
BATTERY
UVLO
ACPR
BAT UV
13
5
IN1 OUT BAT
WALL
1V
4.1V
+
–
RECHARGE
(4.0V
+
–
VOLTAGE DETECT
UVLO
LTC4055-1)
BAT UV
V
RECHRG
NTC
15
16
TIMER
OSCILLATOR
CLK
12
14
CONTROL LOGIC
–
+
100k
HOLD
CHRG
2COLD
NTCERR
RESET
STOP
NTC
COUNTER
NTC
100k
–
+
2HOT
+
NTC ENABLE
2μ
2μ
0.1V
–
GND
SHDN
SUSP
10
6
7
4055 BD
4055fb
10
LTC4055/LTC4055-1
OPERATION
Anotheradvantagetopoweringtheloadfromthebuswhen
thebusisavailableisincaseswheretheloadisaswitching
regulator. The input power to a switching regulator can be
thought of as constant. A higher voltage across a constant
power load will require less current. Less load current in
USB applications means more available charge current.
More charge current translates to shorter charge times.
TheLTC4055/LTC4055-1arecompletePowerPathcontrol-
lers for battery-powered USB applications. The LTC4055/
LTC4055-1aredesignedtoprovidedevicepowerandLi-ion
battery charging from the USB V
while maintaining
BUS
the current limits as specified in the USB specification.
This is accomplished by reducing battery charge current
as output/load current is increased. In this scenario, the
available bus current is maximized in an effort to minimize
battery charge time.
The LTC4055/LTC4055-1 also have the ability to
accommodate power from a wall adapter. Wall adapter
power can be connected to the output (load side) of the
LTC4055/LTC4055-1 through an external device such as a
powerSchottkyorFET,asshowninFigure1.TheLTC4055/
LTC4055-1havetheuniqueabilitytousetheoutput, which
is powered by the wall adapter, as an alternate path to
charge the battery while providing power to the load. A
wall adapter comparator on the LTC4055/LTC4055-1 can
be configured to detect the presence of the wall adapter
and shut off the connection to the USB to prevent reverse
conduction out to the bus.
An ideal diode function provides power from the battery
when output/load current exceeds the input current limit
set for the part or when input power is removed. The
advantage to powering the load through the ideal diode
(rather than connecting the load directly to the battery)
is that when the bus is connected and the battery is fully
charged, thebatteryremainsfullychargeduntilbuspower
is removed. Once bus power is removed the output drops
until the ideal diode is forward biased. The forward biased
ideal diode will then provide the output power to the load
from the battery.
WALL
ADAPTER
IN1
OUT
3
V
4
1
BUS
IN2
LOAD
INPUT CHARGER
CONTROL
CURRENT LIMIT
CONTROL
OUTPUT CHARGER
CONTROL
IDEAL
BAT
ENABLE
ENABLE
ENABLE
2
+
Li-Ion
WALL
1V
5
+
–
UVLO
4055 F01
Figure 1. Simplified Block Diagram—PowerPath
4055fb
11
LTC4055/LTC4055-1
OPERATION
Table 1. Operating Modes—PowerPath States Current Limited Input Power (IN1/IN2 to OUT)
WALL PRESENT SHUTDOWN SUSPEND
V
> 3.8V
V
V
V
> (V
+ 100mV)
V
> (V + 100mV)
CURRENT LIMIT ENABLED
IN
IN
OUT
IN
BAT
Y
X
X
X
X
X
N
X
Y
X
X
X
X
N
X
X
Y
X
X
X
N
X
X
X
N
X
X
Y
X
X
X
X
X
X
N
Y
N
N
N
N
N
N
Y
X
X
X
N
X
Y
Input Powered Charger (IN1/IN2 to BAT)
WALL PRESENT SHUTDOWN SUSPEND
V
> 4.35V
> (V
+ 100mV)
V
IN
> (V + 100mV)
INPUT CHARGER ENABLED
IN
IN
OUT
BAT
Y
X
X
X
X
X
N
X
Y
X
X
X
X
N
X
X
Y
X
X
X
N
X
X
X
N
X
X
Y
X
X
X
X
X
X
N
Y
N
N
N
N
N
N
Y
X
X
X
N
X
Y
Output Powered Charger (OUT to BAT)
WALL PRESENT SHUTDOWN SUSPEND
V
> 4.35V
> (V + 100mV)
V
OUT
> (V + 100mV)
OUTPUT CHARGER ENABLED
IN
OUT
IN
BAT
N
X
X
X
X
Y
X
Y
X
X
X
N
X
X
X
X
X
X
X
X
N
X
X
Y
X
X
X
N
X
Y
X
X
X
X
N
Y
N
N
N
N
N
Y
Ideal Diode (BAT to OUT)
WALL PRESENT SHUTDOWN SUSPEND
V
> 2.8V
V
> V
X
V
IN
DIODE ENABLED
BAT
BAT
OUT
X
X
X
X
Y
X
X
N
X
X
X
X
X
N
X
Y
X
N
N
N
Y
X
X
X
X
N
Y
Table 2. Operating Modes—Pin Currents vs Programmed Currents (Charging from IN1/IN2)
PROGRAMMING OUTPUT CURRENT BATTERY CURRENT
INPUT CURRENT
I
CL
= I
I
< I
CL
> I
I
= I
BAT
– I
I
I
I
= I + I
Q
CHG
OUT
CL
CHG
CL
BAT
CHG
OUT
IN
IN
IN
CL
CL
CL
I
= I = I
I
= 0
= I + I
Q
OUT
I
I
= I – I
= I + I
Q
OUT
BAT
CL
OUT
I
< I
I
I
< (I – I
)
)
I
= I
CL
I
= I + I
+ I
CHG
CL
OUT
OUT
CL
CHG
CHG
BAT
CHG
OUT
IN
Q
CHG
OUT
> (I – I
I
I
= I – I
I
I
I
= I + I
Q
CL
BAT
IN
IN
IN
CL
CL
CL
I
I
= I
> I
I
= 0
CL
= I + I
Q
= I + I
Q
OUT
OUT
CL
CL
BAT
= I – I
BAT
OUT
I
CL
< I
I
< I
CL
I
I
= I – I
CL
I
I
= I + I
Q
= I + I
Q
CHG
OUT
OUT
CL
BAT
BAT
CL
OUT
OUT
IN
IN
CL
CL
I
> I
*
= I – I
*Charge current shuts off when V
drops below V , i.e., when I
exceeds I .
OUT CL
OUT
BAT
4055fb
12
LTC4055/LTC4055-1
OPERATION
4055fb
13
LTC4055/LTC4055-1
OPERATION
USB CURRENT LIMIT AND CHARGE CURRENT
CONTROL
the LTC4055/LTC4055-1 reduces the battery charging
current such that the sum of the battery charge current
and the load current does not exceed 500mA (100mA
when HPWR is low, see Figure 2) The battery charging
current goes to zero when load current exceeds 500mA
(80mA when HPWR is low). If the load current is greater
than the current limit, the output voltage will drop to just
under the battery voltage where the ideal diode circuit will
take over and the excess load current will be drawn from
the battery (shaded region in Figure 2).
The current limit and charger control circuits of the
LTC4055/LTC4055-1 are designed to limit input current
as well as control battery charge current as a function of
I
. The programmed current limit, I is defined as:
OUT
CL
⎛
⎞
49,000
49,000V
RCLPROG
ICL =⎜
• VCLPROG⎟=
⎜
⎟
R
⎝
⎠
CLPROG
Theprogrammedbatterychargecurrent,I ,isdefinedas:
CHG
PROGRAMMING CURRENT LIMIT
The formula for programming current limit is:
VCLPROG
⎛
⎞
48,500
48,500V
RPROG
I
CHG =⎜
• VPROG ⎟=
⎜
⎟
R
⎝
⎠
PROG
ICL = ICLPROG • 49,000 =
• 49,000
RCLPROG
Input current, I , is equal to the sum of the BAT pin output
current and the OUT pin output current.
IN
where V
is the CLPROG pin voltage and R
is
CLPROG
CLPROG
I = I
+ I
BAT
the total resistance from the CLPROG pin to ground.
IN
OUT
The current limiting circuitry in the LTC4055/LTC4055-1
can and should be configured to limit current to 500mA
for USB applications (selectable using the HPWR pin and
programmed using the CLPROG pin).
For example, if typical 490mA current limit is required,
calculate:
1V
490mA
RCLPROG
=
• 49,000 = 100k
When programmed for 500mA current limit and 500mA
or more of charging current, powered from IN1/IN2
and battery charging is active, control circuitry within
InUSBapplications,theminimumvalueforR
should
CLPROG
be 105k. This will prevent the application current from
600
500
400
300
200
100
0
120
100
80
600
500
I
IN
I
I
IN
IN
400
I
I
LOAD
LOAD
I
LOAD
60
300
200
100
0
I
= I
BAT CHG
40
I
BAT
I
BAT
I
= I – I
BAT CL OUT
CHARGING
I
BAT
CHARGING
CHARGING
20
0
–100
–20
–100
0
100
200
300
(mA)
400
500
600
0
20
40
60
(mA)
80
100
120
0
100
200
300
(mA)
400
500
600
I
I
BAT
I
BAT
BAT
I
I
LOAD
I
LOAD
LOAD
(IDEAL DIODE)
(IDEAL DIODE)
(IDEAL DIODE)
4055 F02a
4055 F02b
4055 F02c
(2a) High Power Mode/Full Charge
(RPROG = RCLPROG = 97.6k)
(2b) Low Power Mode/Full Charge
(RPROG = RCLPROG = 97.6k)
(2c) High Power Mode with
ICL = 500mA and ICHG = 250mA
(RPROG = 196k, RCLPROG = 97.6k)
Figure 2. Input and Battery Currents as a Function of Load Current
4055fb
14
LTC4055/LTC4055-1
OPERATION
exceeding 500mA due to LTC4055/LTC4055-1 tolerances
andquiescentcurrents.Thiswillgiveatypicalcurrentlimit
of approximately 467mA in high power mode (HPWR = 1)
or 92mA in low power mode (HPWR = 0).
battery voltage is below 2.8V, the charger goes into
trickle-charge mode to bring the cell voltage up to a safe
level for charging. The charger goes into the fast charge
constant-currentmodeoncethevoltageontheBATpinrises
above 2.8V. In constant current mode, the charge current
For best stability over temperature and time, 1% metal
film resistors are recommended.
is set by R
. When the battery approaches the final
PROG
float voltage, the charge current begins to decrease as the
LTC4055/LTC4055-1 switches to constant-voltage mode.
Battery Charger
An external capacitor on the TIMER pin sets the total
minimum charge time. When this time elapses the
charge cycle terminates and the CHRG pin assumes a
high impedance state. While charging in constant-cur-
rent mode, if the charge current is decreased due to load
current, undervoltage charge current limiting or thermal
regulation the charging time is automatically increased.
In other words, the charge time is extended inversely
proportional to charge current delivered to the battery.
For lithium-ion and similar batteries that require accurate
finalfloatpotential,theinternalbandgapreference,voltage
amplifier and the resistor divider provide regulation with
1% maximum accuracy.
The battery charger circuits of the LTC4055/LTC4055-1
aredesignedforchargingsingle-celllithium-ionbatteries.
FeaturinganinternalP-channelpowerMOSFET,thecharger
usesaconstant-current/constant-voltagechargealgorithm
withprogrammablecurrentandaprogrammabletimerfor
chargetermination.Chargecurrentcanbeprogrammedup
to 1A. The final float voltage accuracy is 0.8% typical. No
blockingdiodeorsenseresistorisrequiredwhencharging
through IN1/IN2. The CHRG open-drain status output
provides information regarding the charging status of the
LTC4055/LTC4055-1atalltimes.AnNTCinputprovidesthe
option of charge qualification using battery temperature.
An internal thermal limit reduces the programmed charge
current if the die temperature attempts to rise above a
presetvalueofapproximately105°C. Thisfeatureprotects
the LTC4055/LTC4055-1 from excessive temperature, and
allows the user to push the limits of the power handling
capability of a given circuit board without risk of dam-
aging the LTC4055/LTC4055-1. Another benefit of the
LTC4055/LTC4055-1 thermal limit is that charge current
can be set according to typical, not worst-case, ambient
temperatures for a given application with the assurance
that the charger will automatically reduce the current in
worst-case conditions.
TRICKLE CHARGE AND DEFECTIVE BATTERY
DETECTION
At the beginning of a charge cycle, if the battery voltage
is low (below 2.8V) the charger goes into trickle-charge
reducingthechargecurrentto10%ofthefull-scalecurrent.
If the low battery voltage persists for one quarter of the
total charge time, the battery is assumed to be defective,
the charge cycle is terminated and the CHRG pin output
assumes a high impedance state. If for any reason the
battery voltage rises above ~2.8V, the charge cycle will
be restarted. To restart the charge cycle (i.e., when the
deadbatteryisreplacedwithadischargedbattery), simply
remove the input voltage and reapply it, cycle the TIMER
pin to 0V or cycle the SHDN pin to 0V.
An internal voltage regulation circuit, called undervoltage
current limit, UVCL, reduces the programmed charge
current to keep the voltage on V or V
at least 4.4V.
IN
OUT
This feature prevents the charger from cycling in and out
of undervoltage lockout due to resistive drops in the USB
or wall adapter cabling.
PROGRAMMING CHARGE CURRENT
The formula for programming the battery charge current,
when not being limited, is:
The charge cycle begins when the voltage at the input
(IN1/IN2) rises above the input UVLO level and the battery
voltageisbelowtherechargethreshold.Nochargecurrent
actually flows until the input voltage is greater than the
VPROG
RPROG
ICHG = IPROG • 48,500 =
• 48,500
V
level. At the beginning of the charge cycle, if the
UVCL
4055fb
15
LTC4055/LTC4055-1
OPERATION
where V
is the PROG pin voltage and R
is the
the LTC4055/LTC4055-1 detect that the change in charge
current is due to voltage mode, and increase the timer
period back to its programmed operating period.
PROG
PROG
total resistance from the PROG pin to ground.
For example, if typical 485mA charge current is required,
calculate:
Once a time-out occurs and the voltage on the battery is
greater than the recharge threshold, the charge current
stops, and the CHRG output assumes a high impedance
state to indicate that the charging has stopped.
1V
485mA
RPROG
=
• 48,500 = 100k
For best stability over temperature and time, 1% metal
film resistors are recommended. Under trickle-charge
conditions, this current is reduced to 10% of the full-
scale value.
Connecting the TIMER pin to ground disables the battery
charger.
CHRG STATUS OUTPUT PIN
When the charge cycle starts, the CHRG pin is pulled
to ground by an internal N-channel MOSFET capable of
driving an LED. After a time-out occurs, the pin assumes
a high impedance state.
THE CHARGE TIMER
The programmable charge timer is used to terminate the
charge cycle. The timer duration is programmed by an
external capacitor at the TIMER pin and is also a function
of the resistance on PROG. Typically the charge time is:
NTC Thermistor
CTIMER •RPROG • 3Hours
tTIMER(Hours) =
Thebatterytemperatureismeasuredbyplacinganegative
temperature coefficient (NTC) thermistor close to the
batterypack.TheNTCcircuitryisshowninFigure3.Touse
0.1μF •100k
The timer starts when an input voltage greater than the
undervoltage lockout threshold level is applied, or when
leavingshutdownandthevoltageonthebatteryislessthan
the recharge threshold. At power-up or exiting shutdown
with the battery voltage less than the recharge threshold,
the charge time is a full cycle. If the battery is greater than
therechargethreshold,thetimerwillnotstartandcharging
is prevented. If after power-up the battery voltage drops
below the recharge threshold, or if after a charge cycle
the battery voltage is still below the recharge threshold,
the charge time is set to one half of a full cycle.
this feature, connect the NTC thermistor, R , between
NTC
the NTC pin and ground and a resistor, R
, from the
NOM
NTC pin to V . R
should be a 1% resistor with a
NTC
NOM
value equal to the value of the chosen NTC thermistor at
25°C(thisvalueis10kforaVishayNTHS0603N02N1002J
thermistor). The LTC4055/LTC4055-1 go into hold mode
when the resistance, R , of the NTC thermistor drops
HOT
to 0.41 times the value of R
or approximately 4.1k,
NOM
which should be at 50°C. The hold mode freezes the timer
and stops the charge cycle until the thermistor indicates a
return to a valid temperature. As the temperature drops,
the resistance of the NTC thermistor rises. The LTC4055/
LTC4055-1 are designed to go into hold mode when the
value of the NTC thermistor increases to 2.82 times the
The LTC4055/LTC4055-1 have a feature that extends
charge time automatically. Charge time is extended if
the charge current in constant-current mode is reduced
due to load current, undervoltage charge current limit-
ing or thermal regulation. This change in charge time is
inversely proportional to the change in charge current. As
theLTC4055/LTC4055-1approachconstant-voltagemode
the charge current begins to drop. This change in charge
current is part of the normal charging operation of the
part and should not affect the timer duration. Therefore,
value of R
. This resistance is R
. For a Vishay
NOM
COLD
NTHS0603N02N1002J thermistor, this value is 28.2k
whichcorrespondstoapproximately0°C.Thehotandcold
comparators each have approximately 3°C of hysteresis
to prevent oscillation about the trip point. Grounding the
NTC pin disables the NTC function.
4055fb
16
LTC4055/LTC4055-1
OPERATION
V
V
NTC
NTC
LTC4055/LTC4055-1
NTC BLOCK
LTC4055/LTC4055-1
NTC BLOCK
15
15
0.74 • V
0.74 • V
NTC
NTC
R
R
NOM
NOM
–
+
–
+
100k
121k
TOO_COLD
TOO_HOT
TOO_COLD
TOO_HOT
NTC
NTC
16
16
R
100k
R1
13.3k
NTC
–
+
–
+
0.29 • V
0.29 • V
NTC
NTC
R
NTC
100k
+
–
+
–
NTC_ENABLE
NTC_ENABLE
0.1V
0.1V
4055 F03a
4055 F03b
(3a)
(3b)
Figure 3. NTC Circuits
THERMISTORS
R
for a shift to lower temperature for example, use
NOM
the following equation:
The LTC4055/LTC4055-1 NTC trip points were designed
to work with thermistors whose resistance-temperature
characteristics follow Vishay Dale’s “R-T Curve 2.” The
Vishay NTHS0603N02N1002J is an example of such a
thermistor. However, Vishay Dale has many thermistor
products that follow the “R-T Curve 2” characteristic in
a variety of sizes. Furthermore, any thermistor whose
ratio of RCOLD to RHOT is about 7.0 will also work
(Vishay Dale R-T Curve 2 shows a ratio of RCOLD to RHOT
of 2.815/0.4086 = 6.89).
RCOLD
2.815
RNOM
=
•RNTC at 25°C
where R
is the resistance ratio of R
at the desired
COLD
NTC
coldtemperaturetrippoint.Ifyouwanttoshiftthetrippoints
to higher temperatures use the following equation:
RHOT
0.4086
RNOM
=
•RNTC at 25°C
where R
hot temperature trip point.
is the resistance ratio of R at the desired
NTC
HOT
Power conscious designs may want to use thermistors
whoseroomtemperaturevalueisgreaterthan10k. Vishay
Dalehasanumberofvaluesofthermistorfrom10kto100k
that follow the “R-T Curve 1.” Using these as indicated
in the NTC Thermistor section will give temperature trip
pointsofapproximately3°Cand47°C,adeltaof44°C.This
delta in temperature can be moved in either direction by
Here is an example using a 100k R-T Curve 1 thermistor
from Vishay Dale. The difference between the trip points
is 44°C, from before, and we want the cold trip point to
be 0°C, which would put the hot trip point at 44°C. The
R
NOM
needed is calculated as follows:
changingthevalueofR
withrespecttoR .Increasing
NOM
NTC
RCOLD
2.815
3.266
RNOM
=
=
•RNTC at 25°C
•100k = 116k
R
will move both trip points to lower temperatures.
NOM
Likewise a decrease in R
with respect to R
will
NOM
NTC
move the trip points to higher temperatures. To calculate
2.815
4055fb
17
LTC4055/LTC4055-1
OPERATION
The nearest 1% value for R
is 115k. This is the value
CHARGER UNDERVOLTAGE LOCKOUT
Internal undervoltage lockout circuits monitor the V and
NOM
used to bias the NTC thermistor to get cold and hot trip
points of approximately 0°C and 44°C respectively. To
extend the delta between the cold and hot trip points a
resistor,R1,canbeaddedinserieswithR (seeFigure 3b).
The values of the resistors are calculated as follows:
IN
V
voltages and keep the charger circuits of the part
OUT
shut down until V or V
rises above the undervoltage
IN
OUT
NTC
lockout threshold. The charger UVLO circuit has a built-
in hysteresis of 125mV. Furthermore, to protect against
reverse current in the power MOSFET, the charger UVLO
RCOLD –RHOT
2.815 – 0.4086
RNOM
=
circuit keeps the charger shutdown if V exceeds V
.
BAT
OUT
0.4086
2.815 – 0.4086
If the charger UVLO comparator is tripped, the charger
⎛
⎝
⎞
⎠
R1=
• RCOLD –RHOT –R
(
HOT
)
⎜
⎟
circuits will not come out of shutdown until V exceeds
OUT
V
BAT
by 50mV.
where R
COLD
is the value of the bias resistor, R
and
NOM
HOT
R
are the values of R
at the desired temperature
SHUTDOWN
NTC
trip points. Continuing the example from before with a
desired hot trip point of 50°C:
The LTC4055/LTC4055-1 can be shut down by forcing the
SHDN pin greater than 1V. In shutdown, the currents on
IN1/IN2, OUT and BAT are decreased to less than 2.5μA
and the internal battery charge timer is reset. All power
paths are put in a Hi-Z state.
100k • 3.266 – 0.3602
R
COLD –RHOT
(
)
RNOM
=
=
2.815 – 0.4086
2.815 – 0.4086
= 120.8k, 121k is nearest 1%
SUSPEND
⎡
⎤
⎥
⎦
0.4086
2.815 – 0.4086
⎛
⎜
⎝
⎞
⎟
⎠
R1= 100k •
• 3.266 – 0.3602 – 0.3602
(
)
⎢
⎣
The LTC4055/LTC4055-1 can be put in suspend mode by
forcing the SUSP pin greater than 1V. In suspend mode
the ideal diode function from BAT to OUT and the output
charger are kept alive. The rest of the part is shut down
to conserve current and the battery charge timer is reset
= 13.3k, 13.3k is nearest 1%
The final solution is as shown if Figure 3b where R
=
NOM
121k, R1 = 13.3k and R
= 100k at 25°C.
NTC
if V
becomes less than V
.
OUT
BAT
CURRENT LIMIT UNDERVOLTAGE LOCKOUT
V and Wall Adapter Bypass Capacitor
IN
Aninternalundervoltagelockoutcircuitmonitorstheinput
voltage and keeps the current limit circuits of the part in
Many types of capacitors can be used for input bypassing.
However,cautionmustbeexercisedwhenusingmultilayer
ceramic capacitors. Because of the self resonant and high
Qcharacteristicsofsometypesofceramiccapacitors,high
voltage transients can be generated under some start-up
conditions, such as connecting the charger input to a hot
power source. For more information, refer to Application
Note 88.
shutdown mode until V rises above the undervoltage
IN
lockout threshold. The current limit UVLO circuit has a
built-in hysteresis of 125mV. Furthermore, to protect
against reverse current in the power MOSFET, the current
limit UVLO circuit keeps the current limit shutdown if
V
exceeds V . If the current limit UVLO comparator
OUT
IN
is tripped, the current limit circuits will not come out of
shutdown until V
falls 50mV below the V voltage.
OUT
IN
4055fb
18
LTC4055/LTC4055-1
OPERATION
Selecting WALL Input Resistors
The nearest 1% resistor is 34.8k. Therefore R1 = 34.8k
and the rising trip point should be 4.48V.
TheWALLinputpinidentifiesthepresenceofawalladapter.
This information is used to disconnect the inputs IN1/IN2
from the OUT pin in order to prevent back conduction to
whatevermaybeconnectedtotheinputs. Italsoforcesthe
ACPR pin low when the voltage at the WALL pin exceeds
theinputthreshold.TheWALLpinhasa1Vrisingthreshold
and approximately 30mV of hysteresis.
⎛
⎞
34.8
10
VHYST(Adapter)≈ 30mV • 1+
≈134mV
⎜
⎟
⎝
⎠
The hysteresis is going to be approximately 134mV for
this example.
Power Dissipation
It needs to be noted that this function is disabled when
the only power applied to the part is from the battery.
Therefore the 1V threshold only applies when the voltage
on either IN1/IN2 or OUT is 100mV greater than the volt-
age on BAT and the voltage on IN1/IN2 or OUT is greater
The conditions that cause the LTC4055/LTC4055-1 to
reduce charge current due to the thermal protection
feedback can be approximated by considering the power
dissipated in the part. For high charge currents and a wall
adapter applied to V , the LTC4055/LTC4055-1 power
dissipation is approximately:
than the V
(3.8V typ) threshold.
UVLO
OUT
The wall adapter detection threshold is set by the follow-
ing equation:
P = (V
– V ) • I
BAT BAT
D
OUT
⎛
⎞
where P is the power dissipated, V
is the supply
BAT
R1
R2
D
OUT
VTH(Adapter)= VWALL • 1+
⎜
⎟
voltage, V is the battery voltage and I is the battery
BAT
⎝
⎠
charge current. It is not necessary to perform any worst-
case power dissipation scenarios because the LTC4055/
LTC4055-1 will automatically reduce the charge current
to maintain the die temperature at approximately 105°C.
However, the approximate ambient temperature at which
the thermal feedback begins to protect the IC is:
⎛
⎞
R1
R2
VHYST(Adapter)= VWALL−HYST • 1+
⎜
⎟
⎝
⎠
whereV (Adapter)isthewalladapterdetectionthreshold,
TH
V
is the WALL pin rising threshold (typically 1V), R1
WALL
is the resistor from the wall adapter input to WALL and
T = 105°C – P • θ
JA
A
D
R2 is the resistor from WALL to GND.
T = 105°C – (V
– V ) • I • θ
BAT BAT JA
A
OUT
Consider an example where the V (Adapter) is to be set
TH
somewhere around 4.5V. Resistance on the WALL pin
shouldbekeptrelativelylow(~10k)inordertopreventfalse
trippingofthewallcomparatorduetoleakagesassociated
with the switching element used to connect the adapter
to OUT. Pick R2 to be 10k and solve for R1.
Example: An LTC4055/LTC4055-1 operating from a wall
adapter with 5V at V providing 0.8A to a 3V Li-Ion
battery. The ambient temperature above, which the
LTC4055/LTC4055-1 will begin to reduce the 0.8A charge
current, is approximately:
OUT
⎛
⎞
T = 105°C – (5V – 3V) • 0.8A • 37°C/W
VTH(Adapter)
VWALL
A
R1=R2•⎜
−1⎟
⎜
⎟
T = 105°C – 1.6W • 37°C/W = 105°C – 59°C = 46°C
A
⎝
⎠
⎛
⎞
4.5
1
R1=10k •
–1 =10k •3.5=35k
⎟
⎜
⎝
⎠
4055fb
19
LTC4055/LTC4055-1
OPERATION
The LTC4055/LTC4055-1 can be used above 46°C, but the
charge current will be reduced below 0.8A. The charge
current at a given ambient temperature can be approxi-
mated by:
temperature. Without a backside thermal connection, this
number could drop to less than 500mA.
STABILITY
105°C – TA
Theconstant-voltagemodefeedbackloopisstablewithout
any compensation when a battery is connected. However,
a 1μF capacitor with a 1Ω series resistor to GND is recom-
mended at the BAT pin to keep ripple voltage low when
the battery is disconnected.
IBAT
=
V
OUT – VBAT •θ
(
)
JA
Considertheaboveexamplewithanambienttemperature
of 55°C. The charge current will be reduced to approxi-
mately:
Ideal Diode from BAT to OUT
105°C – 55°C
50°C
IBAT
=
=
=0.675A
Forward regulation for the LTC4055/LTC4055-1 from BAT
to OUT has three operational ranges, depending on the
magnitude of the load current. For small load currents,
the LTC4055/LTC4055-1 will provide a constant-voltage
drop; this operating mode is referred to as “constant
5V – 3V •37°C/W 74°C/A
(
)
Board Layout Considerations
In order to be able to deliver maximum charge current
under all conditions, it is critical that the Exposed Pad
on the backside of the LTC4055/LTC4055-1 package is
V ” regulation. As the current exceeds I
, the voltage
ON
FWD
drop will increase linearly with the current with a slope
of 1/R ; this operating mode is referred to as
2
DIO,ON
soldered to the board. Correctly soldered to a 2500mm
“constant R ” regulation. As the current increases
ON
double-sided 1oz. copper board, the LTC4055/LTC4055-1
has a thermal resistance of approximately 37°C/W. Failure
to make thermal contact between the Exposed Pad on the
backside of the package and the copper board will result
in thermal resistances far greater than 37°C/W. As an
example, a correctly soldered LTC4055/LTC4055-1 can
deliver over 1A to a battery from a 5V supply at room
further, exceeding I
, the forward voltage drop will
MAX
increase rapidly; this operating mode is referred to as
“constant I ” regulation. The characteristics for the
ON
following parameters: R
specified with the aid of Figure 4.
, R , V
, and I
are
FWD
ON
FWD
FWD
CONSTANT
ON
LTC4055
I
I
MAX
CONSTANT
ON
SLOPE: 1/R
DIO,ON
R
I
FWD
SCHOTTKY
DIODE
CONSTANT
ON
SLOPE: 1/R
FWD
V
4055 F04
0
FORWARD VOLTAGE (V)
V
FWD
Figure 4. LTC4055/LTC4055-1 vs Schottky Diode Forward Voltage Drop
4055fb
20
LTC4055/LTC4055-1
TYPICAL APPLICATIONS
LTC4055/LTC4055-1 Configured for USB Application
with Wall Adapter
allowing the input current supplied by V
to exceed the
BUS
500mA/100mA limits.
The programming resistor (R
) with a value of 60.4k
Figure 5 shows an LTC4055/LTC4055-1 configured for
USB applications with the optional wall adapter input. The
PROG
setsupanominalchargecurrentofapproximately800mA.
Note that this is the charge current when the wall adapter
is present. When the wall adapter is absent, the current
limit supersedes the charge current programming and
charge current is limited to 467mA.
programmingresistor(R
)issetto105kwhichsets
CLPROG
up a nominal current limit of 467mA in high power mode
(92mA in low power). This is done to prevent the various
tolerances in the part and programming resistors from
5V WALL
ADAPTER INPUT
5V (NOM)
TO LDOs,
OUT
FROM USB
IN1
IN2
REGs, ETC
CABLE V
BUS
R3
BAT
10μF
+
1Ω
Li-Ion
CELL
10μF
CHRG
ACPR
WALL
R1
LTC4055
SUSP
HPWR
SHDN
SUSPEND USB POWER
500mA/100mA SELECT
SHUTDOWN
34.8k
R2
10k
V
NTC
R
NTCBIAS
NTC
TIMER PROG CLPROG
100k
GND
NTC
100k
R
R
CLPROG
105k
C
PROG
TIMER
0.1μF
60.4k
4055 F05
Figure 5. USB Power Control Application with Wall Adapter Input
4055fb
21
LTC4055/LTC4055-1
TYPICAL APPLICATIONS
USB Hosting Application: The LTC4055/LTC4055-1’s
IN1 and IN2 are Set Hi-Z by Pulling the SUSP Pin
Above 1.2V
Forcing the SUSP input pin above 1.2V does this. Figure 6
showstheapplicationcircuit.Thewalladapterorthebattery
can still provide power to OUT, which in turn can provide
powertoV
whencommandedfromtheUSBcontroller.
BUS
In applications where the power is required to go back
The ability to charge the battery is enabled when the wall
adapter is present.
out on to the USB V
the LTC4055/LTC4055-1 can be
BUS
configured to turn off its input power path, IN1 and IN2.
5V (NOM)
DC/DC
FROM USB
V
V
IN
CONVERTER
OUT
CABLE V
BUS
1μF
EN
5V WALL
ADAPTER INPUT
TO LDOs,
REGs, ETC
IN1
IN2
OUT
BAT
R1
10μF
34.8k
+
WALL
Li-Ion
CELL
R2
10k
CHRG
ACPR
LTC4055
SUSP
V
500mA/100mA SELECT
SHUTDOWN
HPWR
NTC
R3
100k
USB
CONTROLLER
NTC
SHDN
GND
TIMER PROG CLPROG
NTC
100k
R
R
CLPROG
105k
C
PROG
TIMER
0.1μF
100k
4055 F06
Figure 6. USB Hosting Application
4055fb
22
LTC4055/LTC4055-1
PACKAGE DESCRIPTION
UF Package
16-Lead Plastic QFN (4mm × 4mm)
(Reference LTC DWG # 05-08-1692)
0.72 ±0.05
4.35 ± 0.05
2.90 ± 0.05
2.15 ± 0.05
(4 SIDES)
PACKAGE OUTLINE
0.30 ±0.05
0.65 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
BOTTOM VIEW—EXPOSED PAD
PIN 1 NOTCH R = 0.20 TYP
R = 0.115
OR 0.35 × 45° CHAMFER
0.75 ± 0.05
4.00 ± 0.10
(4 SIDES)
TYP
15
16
0.55 ± 0.20
PIN 1
TOP MARK
(NOTE 6)
1
2
2.15 ± 0.10
(4-SIDES)
(UF16) QFN 1004
0.200 REF
0.30 ± 0.05
0.65 BSC
0.00 – 0.05
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WGGC)
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
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
4055fb
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
23
LTC4055/LTC4055-1
TYPICAL APPLICATION
Adapter Diode Replaced with LTC4411 “Ideal Diode” for Improved Efficiency
LTC4411
1
2
3
5
ADAPTER
SYSTEM LOAD
OUTPUT
V
V
OUT
IN
4.5V TO 5.5V
C5
C3
10μF
1μF
GND
CTL
4
R10
35.8k
STAT
USB
4.35V TO 5.5V
+Li-Ion
C1
10μF
4
3
2
1
IN1
OUT BAT
IN2
USB CURRENT 100mA-500mA
ADAPTER CURRENT 700mA
5
6
7
8
WALL
SHDN
SUSP
16
NTC
VNTC
CHRG
ACPR
R9
10k
R5 10k
15
14
13
NTC
LTC4055
HPWR
17
EXPOSED PAD
CLPROG GND PROG TIMER
10 11 12
R3
9
C2
0.1μF
R2
105k
68.1k
4055 TA03
RELATED PARTS
PART NUMBER DESCRIPTION
Battery Chargers
COMMENTS
LTC4075HVX
Dual Input USB/AC Adapter Li-Ion Battery Charger with
Overvoltage Protection
Both USB and AC Adapter Inputs Protected up to 22V, Standalone
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LTC4095
LTC4097
LTC4413
950mA USB Linear Lithium-Ion Battery Charger
2mm × 2mm DFN Package, thermal Regulation, Standalone Operation
Dual Input, Thermal Regulation, 3mm × 2mm DFN
USB/Wall Adapter Standalone Li-Ion/Polymer Battery Charger
Dual Monolithic Ideal Diodes
3mm × 3mm DFN Package, Low Loss Replacement for ORing Diodes
Power Management
LTC4066/
LTC4066-1
USB Power Controller and Battery Charger
“Instant On” Operation, 50mΩ Ideal Diode, 4.1V Float Voltage
(LTC4066-1), 4mm × 4mm QFN24 Package
LTC4085/
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USB Power Manager with Ideal Diode Controller and Li-Ion
Charger
“Instant On” Operation, 200mΩ Ideal Diode with <50mΩ Option,
4.1V Float Voltage (LTC4085-1), 4mm × 3mm DFN14 Package
LTC4088
High Efficiency USB Power Manager and Battery Charger
Maximizes Available Power from USB Port, Bat-Track™, “Instant On”
Operation, 1.5A Max Charge Current, 180mΩ Ideal Diode with <50mΩ
Option, 3.3V/25mA Always-On LDO, 4mm × 3mm DFN14 Package
LTC4088-1/
LTC4088-2
High Efficiency USB Power Manager and Battery Charger with Maximizes Available Power from USB Port, Bat-Track, “Instant On”
Regulated Output Voltage
Operation, 1.5A Max Charge Current, 180mΩ Ideal Diode with <50mΩ
Option, Automatic Charge Current Reduction Maintains 3.6V V , No
OUT
3.3V LDO, 4mm × 3mm DFN14 Package
LTC4089/
LTC4089-5/
LTC4089-1
USB Power Manager with Ideal Diode Controller and High
Voltage High Efficiency Li-Ion Battery Charger
High Efficiency 1.2A Charger from 6V to 36V (40V Max) Input, 200mΩ
Ideal Diode with <50mΩ Option, 6mm × 3mm DFN22, Bat-Track Adaptive
Output Control (LTC4089), Fixed 5V Output (LTC4089-5), 4.1V Float
Voltage (LTC4089-1)
LTC4090/
LTC4090-5
USB Power Manager with Ideal Diode Controller and High
Voltage High Efficiency Li-Ion Battery Charger
High Efficiency 1.2A Charger from 6V to 38V (60V Max) Input (2A
Available to Load). 200mΩ Ideal Diode with <50mΩ Option, 6mm × 3mm
DFN22, Bat-Track Adaptive Output Control (LTC4089), Fixed 5V Output
(LTC4089-5)
Bat-Track is a trademark of Linear Technology Corporation.
4055fb
LT 1108 REV B • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
24
●
●
© LINEAR TECHNOLOGY CORPORATION 2004
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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Linear
LTC4057ES5-4.2#TR
LTC4057-4.2 - Linear Li-Ion Battery Charger with Thermal Regulation in ThinSOT; Package: SOT; Pins: 5; Temperature Range: -40°C to 85°C
Linear
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