LTC4055 [Linear]
USB Power Controller and Li-Ion Linear Charger; USB电源控制器和锂离子电池线性充电器
| 型号： | LTC4055 |
| 厂家： | 
Linear |
| 描述： | USB Power Controller and Li-Ion Linear Charger |
| 文件： | 总24页 (文件大小：284K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Electrical Specifications Subject to Change
LTC4055
USB Power Controller
and Li-Ion Linear Charger
U
FEATURES
DESCRIPTIO
■
Charges Single Cell Li-Ion Batteries Directly from
The LTC®4055 is a USB power manager and Li-Ion battery
charger designed to work in portable battery-powered
applications. The part manages and limits the total current
used by the USB peripheral for operation and battery
charging. Depending on the state of the current select pin
(HPWR),totalinputcurrentcanbelimitedtoeither100mA
or 500mA. The voltage drop from the USB supply or
battery to the USB peripheral is typically less than 100mV
at400mAand20mVat80mA.Othermanagementfeatures
include: automatic switch over to battery when input is
removed, inrush current limiting, reverse current block-
ing, undervoltage lockout and thermal shutdown.
USB Port
■
Load Dependent Charging Guarantees USB Input
Current Compliance
■
Automatic Battery Switchover When Input Supply
is Removed
■
Constant-Current/Constant-Voltage Operation with
Thermal Feedback to Maximize Charging Rate
Without Risk of Overheating
■
Selectable 100% or 20% Current Limit
(e.g., 500mA/100mA)
Low Loss Full PowerPathTM Control with Ideal Diode
■
Operation (Reverse Current Blocking)
The LTC4055 includes a complete constant-current/con-
stant-voltage linear charger for single cell Li-ion batteries.
The float voltage applied to the battery is held to a tight
0.8%(typ)tolerance,andchargecurrentisprogrammable
usinganexternalresistortoground.Fullydischargedcells
are automatically trickle charged at 10% of the pro-
grammed current until the cell voltage exceeds 2.8V. Total
charge time is programmable by an external capacitor to
ground. When the battery drops 100mV below the float
voltage, automatic recharging of the battery occurs. Also
featured is an NTC thermistor input used to monitor
battery temperature while charging.
■
Preset 4.2V Charge Voltage with 0.8% Accuracy
■
USB Compliant Suspend Mode
■
Programmable Charge Current and Termination Timer
■
Automatic Recharge
Soft-Start Limits Inrush Current
■
■
NTC Thermistor Input for Temperature Qualified
Charging
■
Tiny (4mm × 4mm × 0.8mm) QFN Package
U
APPLICATIO S
■
Portable USB Devices: Cameras, MP3 Players, PDAs
The LTC4055 is available in a 16-pin low profile
(4mm × 4mm) QFN package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
PowerPath is a trademark of Linear Technology Corporation.
U
High Power/Full Charge
RPROG = RCLPROG = 100k
TYPICAL APPLICATIO
600
5V (NOM)
TO LDOs,
REGs, ETC
I
IN
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
0.1µF
100k 100k
–100
4055 TA01
0
100
200
300
(mA)
400
500
600
I
BAT
(IDEAL DIODE)
I
LOAD
4055 TA02
4055p
1
LTC4055
W W
U W
U
W U
ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
(Notes 1, 2, 3, 4, 5)
TOP VIEW
Terminal Voltage
ORDER PART
NUMBER
IN1, IN2, OUT, BAT ................................ –0.3V to 6V
NTC, VNTC, TIMER,
PROG, CLPROG..................... –0.3V to (VCC + 0.3V)
CHRG, HPWR, SUSP, SHDN,
16 15 14 13
LTC4055EUF
IN2
BAT
OUT
IN1
1
2
3
4
12 TIMER
11 PROG
17
GND
10
9
WALL, ACPR .......................................... –0.3V to 6V
IN2 .......................................................... VIN1 + 0.1V
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
Reflow Peak Body Temperature........................... 260°C
Storage Temperature Range ................ –65°C to 125°C
CLPROG
5
6
7
8
UF PART
MARKING
UF PACKAGE
16-LEAD (4mm × 4mm) PLASTIC QFN
4055
TJMAX = 125°C, θJA = 37°C/W
EXPOSED PAD IS GND (PIN 17)
MUST BE SOLDERED TO PCB
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● indicates 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
V
V
Input Supply Voltage
Input Voltage
●
●
4.35
V
V
IN
4.3
BAT
I
Input Supply Current
V
= 4.2V
●
●
0.8
50
1.6
mA
µA
IN
BAT
Suspend Mode
100
Suspend Mode, Wall = 2V, V
Shutdown
= 4.8V
0.2
10
mA
µA
OUT
●
●
20
I
I
Output Supply Current
Battery Drain Current
V
V
= 5V, V = V = 0V, V = 4.2V
BAT
450
900
µA
OUT
BAT
OUT
IN1
IN2
= 4.2V, Charging Stopped
●
●
●
●
15
15
2.5
50
30
30
5
µA
µA
µA
µA
BAT
Suspend Mode
Shutdown
V
IN1
= V = 0V, BAT Powers OUT, No Load
100
IN2
I
Maximum Current Limit
(Note 8)
1
A
LIM(MAX)
V
Input or Output Undervoltage Lockout
V
V
Powers Part, Rising Threshold
OUT
●
●
3.6
3.6
3.8
3.8
4
4
V
V
UVLO
IN
Powers Part, Rising Threshold
∆V
UVLO
Input or Output Undervoltage Lockout
Hysteresis
V
V
Rising – V Falling or
125
mV
IN
IN
Rising – V
Falling
OUT
OUT
Current Limit
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
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
Soft-Start Inrush Current
IN or OUT
5
mA/µs
V
SS
V
Input Current Limit Enable Threshold
Input Current Limit Enable Threshold
V
IN
V
IN
Rising
●
3.6
3.8
125
4
CLEN
∆V
Rising – V Falling
mV
CLEN
IN
V
Automatic Limit Enable Threshold
Voltage
(V – V ) V Rising
25
–75
50
–50
75
–25
mV
mV
ALEN
IN
OUT IN
(V – V ) V Falling
IN
OUT IN
4055p
2
LTC4055
ELECTRICAL CHARACTERISTICS
RPROG = RCLPROG = 100k, unless otherwise noted.
The ● indicates 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,
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Battery Charger
V
Regulated Output Voltage
(0°C to 85°C)
4.165
4.158
4.200
4.200
4.235
4.242
V
V
FLOAT
●
I
Current Mode Charge Current
R
R
R
= 100k, HPWR = 5V, No Load
= 100k, HPWR = 0V, No Load
●
●
●
445
55
485
80
525
105
525
mA
mA
mA
BAT
PROG
PROG
PROG
WALL
= 100k, V
= 2V
= 5V, V = 0V,
445
485
OUT
IN
V
R
PROG
R
PROG
WALL
= 50k, HPWR = 5V, No Load
●
●
900
900
980
980
1060
1060
mA
mA
= 50k, V
= 2V
= 5V, V = 0V,
IN
OUT
V
I
Maximum Charge Current
(Note 8)
∆I /∆I , I
BAT OUT OUT
1
1
A
mA/mA
mA
BAT(MAX)
∆I /∆I
Charge Current Load Dependency
Trickle Charge Current
= 100mA
= 100k
PROG
●
●
0.95
30
1.05
60
3
B
O
I
V
BAT
V
BAT
= 2V, R
Rising
45
2.85
TRKL
V
V
Trickle Charge Threshold Voltage
2.7
V
TRKL
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
V
V
Output Charger Enable Threshold
Voltage
(V
(V
– V ) High to Low
70
80
mV
mV
CENO
UVCL
OUT
OUT
BAT
– V ) Low to High
BAT
Input/Output Undervoltage Current
Limit
I
= I /2
CHG
●
●
4.23
65
4.3
4.37
135
V
BAT
Recharge Battery Threshold Voltage
TIMER Accuracy
V
C
– V
RECHRG
100
±10
50
mV
%
RECHRG
TIMER
FLOAT
t
= 0.1µF
TIMER
Recharge Time
Percent of Total Charge Time
Percent of Total Charge Time, V
%
Low-Battery Trickle Charge Time
< 2.8V
25
%
BAT
T
Junction Temperature in Constant
Temperature Mode
105
°C
LIM
Ideal Diode
R
R
On Resistance, V Regulation
V
V
= 3.5V, 100mA Load
= 3.5V, 600mA Load
0.1
0.2
Ω
Ω
FWD
ON
BAT
On Resistance V
to V
OUT
DIO,ON
FWD
BAT
BAT
V
Voltage Forward Drop (V
– V
)
V
BAT
V
BAT
V
BAT
= 3.5V, 5mA Load
= 3.5V, 100mA Load
= 3.5V, 600mA
●
10
30
55
120
50
mV
mV
mV
BAT
OUT
V
Diode Disable Battery Voltage
V
V
V
Falling
2.8
550
1.8
V
mA
A
OFF
FWD
MAX
BAT
I
I
Load Current Limit for V Regulation
= 3.5V
ON
IN
Diode Current Limit
= 3.5V, V
10% Duty Cycle
= 2.8V, Pulsed with
1.4
2.2
BAT
OUT
Logic
V
V
V
Output Low Voltage (CHRG, ACPR)
Enable Input High Voltage
I
= 5mA
SINK
●
●
●
0.2
0.4
1.2
V
V
OL
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
V
Charger Shutdown Threshold Voltage TIMER Falling
on TIMER
●
●
●
0.15
2
0.4
CHG,SD
I
Charger Shutdown Pull-Up Current
on TIMER
V
= 0V
µA
CHG,SD
TIMER
V
V
Wall Input Threshold Voltage
Wall Input Hysteresis
V
V
V
Rising Threshold
0.98
1.000
35
1.02
V
mV
nA
WALL
WALL
WALL
WALL
Rising – V
Falling Threshold
WALL
WALL,HYS
WALL
I
Wall Input Leakage Current
= 1V
0
±50
4055p
3
LTC4055
ELECTRICAL CHARACTERISTICS
RPROG = RCLPROG = 100k, unless otherwise noted.
The ● indicates 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,
SYMBOL
NTC
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
V
V
Pin Current
Bias Voltage
V
= 2.5V
●
●
1.5
3.4
2.5
3.8
3.5
mA
V
VNTC
NTC
NTC
VNTC
V
V
I
= 500µA
VNTC
COLD
VNTC
Cold Temperature Fault Threshold
Voltage
Rising Threshold
Falling Threshold
0.74 • V
0.72 • V
V
V
VNTC
VNTC
V
V
Hot Temperature Fault Threshold
Voltage
Falling Threshold
Rising Threshold
0.29 • V
0.30 • V
V
V
HOT
DIS
VNTC
VNTC
NTC Disable Voltage
NTC Input Voltage to GND (Falling)
Hysteresis
●
75
100
50
125
mV
mV
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 1: Absolute Maximum Ratings are those beyond which the life of a
device may be impaired.
Note 6: The LTC4055EUF 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.
Note 7: Guaranteed by long term current density limitations.
Note 8: Accuracy of programmed current may degrade for currents
Note 2: V is the greater of V , V
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 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.
or V
BAT
CC
IN1 OUT
greater than 1A.
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Battery Drain Current vs
Temperature (BAT Powers OUT,
No Load)
Input Supply Current
vs Temperature
Input Supply Current
vs Temperature (Suspend Mode)
60
50
40
30
20
10
0
900
800
700
600
500
400
300
200
100
70
60
50
40
30
20
10
0
V
V
= 5V
V
V
= 5V
V
= 0V
IN
IN
IN
= 4.2V
= R
= 4.2V
= R
V
= 4.2V
BAT
BAT
BAT
R
= 100k
CLPROG
R
= 100k
CLPROG
PROG
PROG
SUSP = 5V
0
–50
0
25
50
75
100
–25
–50
–25
0
25
75
100
–50 –25
0
25
50
75
100
50
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
4055 G02
4055 G01
4055 G03
4055p
4
LTC4055
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Input Current Limit vs
Temperature, HPWR = 5V
Input Current Limit vs
Temperature, HPWR = 0V
RON vs Temperature
515
505
495
485
475
465
250
225
200
175
105.0
102.5
100.0
97.5
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
= 5V
IN
V
IN
= 4.5V
V
= 5.5V
IN
150
125
100
95.0
92.5
90.0
–50 –25
0
25
50
75 100 125
50
100 125
–50 –25
0
25
75
50
TEMPERATURE (°C)
100 125
–50 –25
0
25
75
TEMPERATURE (°C)
TEMPERATURE (°C)
4055 G04
4055 G06
4055 G05
CLPROG Pin Voltage
vs Temperature
Battery Regulated Output (Float)
Voltage vs Temperature
PROG Pin Voltage vs Temperature
1.020
1.015
1.010
1.005
1.020
1.015
1.010
1.005
4.220
4.215
4.210
4.205
V
= 5V
PROG
V
R
= 5V
IN
CLPROG
V
= 5V
IN
IN
R
= 100k
= 100k
1.000
0.995
1.000
0.995
4.200
4.195
0.990
0.985
0.980
0.990
0.985
0.980
4.190
4.185
4.180
–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 (°C)
4055 G07
4055 G08
4055 G09
Regulated Output Voltage-
Recharge Threshold Voltage
vs Temperature
Battery Regulated Output (Float)
Voltage vs Supply Voltage
Battery Current and Voltage
vs Time
600
500
6
5
120
115
110
105
4.220
4.215
4.210
4.205
V
= 5V
IN
CHRG
V
BAT
400
300
4
3
100
95
4.200
4.195
200
100
0
2
1
0
0.8AHr CELL
= 5V
I
BAT
90
85
80
4.190
4.185
4.180
V
IN
T
= 25°C
A
R
= 105k
PROG
0
20 40 60 80 100 120 140 160 180 200
TIME (MINUTES)
–25
0
50
4.75
5
5.5
–50
75
100
4.5
5.75
6
25
5.25
(V)
TEMPERATURE (°C)
V
IN
4055 G12
4055 G10
4055 G11
4055p
5
LTC4055
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Undervoltage Current Limit,
Charging from VIN, IBAT vs VIN
Charging from USB, Low Power,
IBAT vs VBAT
Charging from USB, IBAT vs VBAT
100
80
600
500
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
V
V
R
R
= 5V
V
V
R
R
= 5V
IN
OUT
IN
OUT
= NO LOAD
= 100k
= NO LOAD
= 100k
PROG
PROG
R
= 34k
PROG
= 100k
= 100k
CLPROG
CLPROG
HPWR = 0
HPWR = 1
R
= 50k
400
PROG
60
300
200
40
20
0
R
PROG
= 100Ω
100
0
R
= 100k
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
2.5
(V)
3
3.5
4
4.5
4.260
4.300
4.340
4.380
4.420
V
BAT
V
BAT
V
(V)
IN
4055 G14
4055 G13
4055 G15
Charge Current vs Temperature
(Thermal Regulation)
Ideal Diode Forward Voltage and
Resistance vs Current
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
900
800
700
600
500
400
300
200
100
0
V
V
= 3.5V
V
V
= 3.5V
BAT
IN
BAT
IN
25°C
0°C
–50°C
R
PROG
= 50k
= 0V
= 0V
125°C
75°C
R
= 100k
PROG
R
DIO(ON)
R
FWD
V
V
JA
= 5V
BAT
= 37°C/W
IN
= 3.5V
θ
–50
0
25
50
75 100 125
–25
0
20 40 60 80 100 120 140 160 180 200
(mV)
0
20 40 60 80 100 120 140 160 180 200
(mV)
TEMPERATURE (°C)
V
V
FWD
FWD
4055 G16
4055 G17
4055 G18
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
= 3.5V
BAT
IN
V
= 0V
V
IN
IN
5V/DIV
5V/DIV
V
OUT
5V/DIV
V
OUT
5V/DIV
I
IN
I
IN
0.5A/DIV
0.5A/DIV
I
I
BAT
0.5A/DIV
BAT
0.5A/DIV
SCHOTTKY
V
BAT
= 3.5V
= 100mA
1ms/DIV
4055 G20
1ms/DIV
4055 G22
V
I
= 3.5V
= 100mA
BAT
I
OUT
OUT
0
50 100 150 200 250 300 350 400 450
(mV)
V
FWD
4055 G19
4055p
6
LTC4055
U W
TYPICAL PERFOR A CE CHARACTERISTICS
WALL Connect Waveforms
VIN = 0V
Response to Suspend
Response to HPWR
WALL
5V/DIV
OUT
HPWR
5V/DIV
SUSPEND
5V/DIV
OUT
5V/DIV
5V/DIV
I
WALL
I
I
IN
IN
0.5A/DIV
0.5A/DIV
0.5A/DIV
I
BAT
I
I
0.5A/DIV
BAT
BAT
0.5A/DIV
0.5A/DIV
V
I
= 3.5V
V
I
= 3.5V
= 50mA
250µs/DIV
4055 G21
V
I
= 3.5V
BAT
OUT
1ms/DIV
4055 G23
1ms/DIV
4055 G24
BAT
OUT
R
BAT
OUT
= 100mA
= 50mA
= 57.6k
PROG
WALL Disconnect Waveforms
VIN = 0V
WALL Connect Waveforms
VIN = 5V
WALL Disconnect Waveforms
VIN = 5V
WALL
5V/DIV
OUT
WALL
WALL
5V/DIV
5V/DIV
I
IN
I
IN
5V/DIV
0.5A/DIV
0.5A/DIV
I
I
I
WALL
WALL
WALL
0.5A/DIV
0.5A/DIV
0.5A/DIV
I
I
BAT
I
BAT
BAT
0.5A/DIV
0.5A/DIV
0.5A/DIV
V
I
= 3.5V
1ms/DIV
4055 G27
V
I
= 3.5V
1ms/DIV
4055 G25
V
I
= 3.5V
BAT
OUT
R
PROG
1ms/DIV
4055 G26
BAT
OUT
R
BAT
OUT
R
= 100mA
= 57.6k
= 100mA
= 57.6k
= 100mA
= 57.6k
PROG
PROG
4055p
7
LTC4055
U
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PI FU CTIO S
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
connects BAT to OUT and prevents VOUT from dropping
more than 100mV below VBAT. A precision internal resis-
tor divider sets the final float potential on this pin. The
internalresistordividerisdisconnectedwhenIN1/IN2and
OUT are in UVLO.
SUSP(Pin7):SuspendModeInput. Pullingthispinabove
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
V
OUT is less than VBAT while in suspend mode. If VOUT is
kept greater than VBAT, such as when a wall adapter is
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 VBUS (IN1/IN2) or
thebattery(BAT)whentheUSBisnotpresent. Canalsobe
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 logic HI 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 logic low on the
pin will set the current limit to 20% of the current pro-
grammedbytheCLPROGpinanddecreasebatterycharge
currentto16%ofthecurrentprogrammedbytheCLPROG
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 (Pin 4/Pin 1): Input Supply. Connect to USB
supply, VBUS. Used as main supply while connected to
USB VBUS 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 pro-
grammed by the PROG pin but will be limited by the input
current limit if set greater than the current limit.
CLPROG (Pin 9): Current Limit Program. Connecting a
resistor, RCLPROG to ground, programs the input to output
current limit. The current limit is programmed as follows:
Connect IN2 to IN1 with a resistance no greater than
0.05Ω.
WALL (Pin 5): Wall Adapter Present Input. Pulling this pin
above 1V will disable charging from IN1/IN2 and discon-
nect 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 to
be 100mV greater than VBAT and greater than VUVLO to
activate this function.
VCLPROG
RCLPROG
50,000V
RCLPROG
ICL(A) =
• 50,000 =
In USB applications the resistor RCLPROG should be set to
no less than 105k.
GND (Pin 10): Ground.
SHDN (Pin 6): Shutdown Input. Pulling this pin high 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
ensureitisenabledatpowerupwhentheinputisnotbeing
driven externally.
PROG (Pin 11): Charge Current Program. Connecting a
resistor, RPROG, to ground programs the battery charge
current. The battery charge current is programmed as
follows:
VPROG
RPROG
50,000V
RPROG
ICHG(A) =
• 50,000 =
4055p
8
LTC4055
U
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PI FU CTIO S
TIMER (Pin 12): Timer Capacitor. Placing a capacitor
VNTC (Pin 15): Output Bias Voltage for NTC. A resistor
from this pin to the NTC pin will set up the bias for an NTC
thermistor.
C
TIMER to GND sets the timer period. The timer period is:
CTIMER •RPROG • 3Hours
tTIMER(Hours) =
NTC (Pin 16): Input to the NTC Thermistor Monitoring
Circuits. Undernormaloperation, tieathermistorfromthe
NTC pin to ground and a resistor of equal value from NTC
toVNTC. Whenthevoltageonthispinisabove0.74•VVNTC
(Cold, 0°C) or below 0.29 • VVNTC (Hot, 50°C) the timer is
suspended, but not cleared, the charging is disabled and
theCHRGpinremainsinitsformerstate.Whenthevoltage
on NTC comes back between 0.74 • VVNTC and 0.29 •
VVNTC, the timer continues where it 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.
0.1µF •100k
Charge time is increased as charge current is reduced due
to input voltage regulation, load current and current limit
selection (HPWR).
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).
If the NTC function is not to be used, connect the NTC to
ground.ThiswilldisablealloftheLTC4055NTCfunctions.
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
ortheinputsupplyoroutputsupplyisremoved, theCHRG
pin is forced to a high impedance state.
Exposed Pad (Pin 17): Ground. The Exposed Pad must be
soldered to a good thermally conductive PCB ground.
4055p
9
LTC4055
W
BLOCK DIAGRA
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
V
REF
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
2u
+
–
2.8V
BATTERY
UVLO
ACPR
BAT UV
13
5
IN1 OUT BAT
WALL
1V
+
–
+
–
4.1V
RECHARGE
VOLTAGE DETECT
UVLO
BAT UV
V
RECHRG
NTC
15
16
TIMER
CHRG
OSCILLATOR
CLK
12
14
CONTROL LOGIC
–
+
100k
HOLD
2COLD
NTCERR
RESET
STOP
NTC
COUNTER
NTC
100k
–
+
2HOT
+
NTC ENABLE
2u
2u
0.1V
–
GND
SHDN
SUSP
10
6
7
4055 BD
4055p
10
LTC4055
U
OPERATIO
The LTC4055 is a complete PowerPath controller for
battery-powered USB applications. The LTC4055 is de-
signed to provide device power and Li-ion battery charg-
ingfromtheUSBVBUS whilemaintainingthecurrentlimits
asspecifiedintheUSBspecification.Thisisaccomplished
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.
Another advantage to powering the load from the bus
when the bus is available is in cases where the load is a
switching regulator. The input power to a switching regu-
lator 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 avail-
able charge current. More charge current translates to
shorter charge times.
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.
The LTC4055 also has the ability to accommodate power
from a wall adapter. Wall adapter power can be connected
to the output (load side) of the LTC4055 through an
externaldevicesuchasapowerSchottkyorFET,asshown
in Figure 1. The LTC4055 has the unique ability to use the
output, which is powered by the wall adapter, as an
alternate path to charge the battery while providing power
totheload. AwalladaptercomparatorontheLTC4055can
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.
AC
IN1
OUT
3
V
BUS
4
1
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
4055p
11
LTC4055
U
OPERATIO
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
N
N
N
N
N
N
Y
X
X
X
N
X
Y
X
X
X
X
N
Y
Input Powered Charger (IN1/IN2 to BAT)
WALL PRESENT
SHUTDOWN
SUSPEND
V
IN
> 4.35V
> (V
+ 100mV)
V
> (V
+ 100mV)
INPUT CHARGER ENABLED
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
N
N
N
N
N
N
Y
X
X
X
N
X
Y
X
X
X
X
N
Y
Output Powered Charger (OUT to BAT)
WALL PRESENT
SHUTDOWN
SUSPEND
V
> 4.35V
> (V + 100mV)
V
> (V
+ 100mV) OUTPUT CHARGER ENABLED
OUT
OUT
IN
OUT
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
N
N
N
N
N
Y
X
X
X
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
= I
CHG
I
< I
I
= I
– I
= 0
I
I
I
= I + I
Q
CL
OUT
CL
BAT
CHG
OUT
IN
IN
IN
CL
CL
CL
I
= I = I
I
= I + I
OUT
I
CL
CHG
BAT
Q
> I
I
= I – I
= I + I
Q
OUT
CL
BAT
CL
OUT
I
< I
CL
I
I
< (I – I
)
)
I
= I
I
= I + I
+ I
CHG
OUT
OUT
CL
CHG
CHG
BAT
CHG
IN
Q
CHG
OUT
> (I – I
I
I
= I – I
I
I
I
= I + I
= I + I
Q
= I + I
Q
CL
BAT
CL
OUT
IN
IN
IN
Q
CL
CL
CL
I
I
= I
> I
I
= 0
OUT
OUT
CL
BAT
= I – I
CL
CL
BAT
OUT
I
< I
CHG
I
I
< I
I
I
= I – I
= I – I
CL
I
I
= I + I
Q
= I + I
Q
CL
OUT
OUT
CL
*
BAT
BAT
CL
OUT
OUT
IN
IN
CL
CL
> I
CL
*Charge current shuts off when V
drops below V , i.e., when I
exceeds I .
OUT CL
OUT
BAT
4055p
12
LTC4055
U
OPERATIO
4055p
13
LTC4055
U
OPERATIO
USB CURRENT LIMIT AND CHARGE CURRENT
LTC4055 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.
CONTROL
ThecurrentlimitandchargercontrolcircuitsoftheLTC4055
are designed to limit input current as well as control
battery charge current as a function of IOUT. The pro-
grammed current limit, ICL is defined as:
50,000
RCLPROG
50,000V
RCLPROG
ICL
=
• VCLPROG =
The programmed battery charge current, ICHG, is defined
as:
PROGRAMMING CURRENT LIMIT
The formula for current limit is:
50,000
RPROG
50,000V
RPROG
VCLPROG
RCLPROG
ICHG
=
• VPROG =
ICL =ICLPROG • 50,000 =
• 50,000
Input current, IIN, is equal to the sum of the BAT pin output
current and the OUT pin output current.
where VCLPROG is the CLPROG pin voltage and RCLPROG is
the total resistance from the CLPROG pin to ground.
IIN = IOUT + IBAT
For example, if typical 500mA current limit is required,
calculate:
The current limiting circuitry in the LTC4055 can and
should be configured to limit current to 500mA for USB
applications (selectable using the HPWR pin and pro-
grammed using the CLPROG pin).
1V
RCLPROG
=
• 50,000 = 100k
500mA
In USB applications, the minimum value for RCLPROG
should be 105k. This will prevent the application current
from exceeding 500mA due to LTC4055’s tolerances and
Whenprogrammedfor500mAcurrentlimitand500mAor
more of charging current, powered from IN1/IN2 and
battery charging is active, control circuitry within the
600
500
400
300
200
100
0
120
100
80
600
500
I
IN
I
I
IN
IN
400
300
200
100
0
I
I
LOAD
LOAD
I
LOAD
60
I
= I
BAT CHG
40
I
BAT
I
BAT
CHARGING
I
= I – I
BAT CL OUT
I
CHARGING
BAT
20
CHARGING
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
I
BAT
BAT
BAT
I
I
I
LOAD
LOAD
LOAD
(IDEAL DIODE)
(IDEAL DIODE)
(IDEAL DIODE)
4055 F02a
4055 F02b
4055 F02c
(2a) High Power Mode/Full Charge
RPROG = RCLPROG = 100k
(2b) Low Power Mode/Full Charge
(RPROG = RCLPROG = 100k)
(2c) High Power Mode with
ICL = 500mA and ICHG = 250mA
(RPROG = 200k, RCLPROG = 100k)
Figure 2. Input and Battery Currents as a Function of Load Current
4055p
14
LTC4055
U
OPERATIO
quiescent currents. This will give a typical current limit of
approximately 467mA in high power mode (HPWR = 1) or
92mA in low power mode (HPWR = 0).
charge mode to bring the cell voltage up to a safe level for
charging. The charger goes into the fast charge constant-
current mode once the voltage on the BAT pin rises above
2.8V. In constant current mode, the charge current is set
by RPROG. When the battery approaches the final float
voltage, the charge current begins to decrease as the
LTC4055 switches to constant-voltage mode.
Forbeststabilityovertemperatureandtime,1%metalfilm
resistors are recommended.
Battery Charger
An external capacitor on the TIMER pin sets the total
minimum charge time. When this time elapses the charge
cycleterminatesandtheCHRGpinassumesahighimped-
ancestate.Whilecharginginconstant-currentmode,ifthe
charge current is decreased due to load current, under-
voltage charge current limiting or thermal regulation the
charging time is automatically increased. In other words,
the charge time is extended inversely proportional to
chargecurrentdeliveredtothebattery.Forlithium-ionand
similar batteries that require accurate final float potential,
the internal bandgap reference, voltage amplifier and the
resistor divider provide regulation with ±1% maximum
accuracy.
The battery charger circuits of the LTC4055 are designed
for charging single cell lithium-ion batteries. Featuring an
internal P-channel power MOSFET, the charger uses a
constant-current/constant-voltage charge algorithm with
programmable current and a programmable timer for
charge termination. Charge current can be programmed
up to 1A. The final float voltage accuracy is ±0.8% typical.
No blocking diode or sense resistor is required when
charging through IN1/IN2. The CHRG open-drain status
outputprovidesinformationregardingthechargingstatus
of the LTC4055 at all times. An NTC input provides the
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 from excessive temperature, and allows the
user to push the limits of the power handling capability of
agivencircuitboardwithoutriskofdamagingtheLTC4055.
AnotherbenefitoftheLTC4055thermallimitisthatcharge
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
reducing the charge current to 10% of the full-scale
current. If the low battery voltage persists for one quarter
of the total charge time, the battery is assumed to be
defective, thechargecycleisterminatedandtheCHRGpin
output assumes a high impedance state. If for any reason
thebatteryvoltagerisesabove~2.8V, thechargecyclewill
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 VIN or VOUT at least 4.4V.
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 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
VUVCL level. At the beginning of the charge cycle, if the
battery voltage is below 2.8V, the charger goes into trickle
Theformulaforthebatterychargecurrent, whennotbeing
limited, is:
VPROG
RPROG
ICHG =IPROG • 50,000 =
• 50,000
4055p
15
LTC4055
U
OPERATIO
where VPROG is the PROG pin voltage and RPROG is the
that the change in charge current is due to voltage mode,
and increases the timer period back to its programmed
operating period.
total resistance from the PROG pin to ground.
For example, if typical 500mA 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
500mA
RPROG
=
• 50,000 = 100k
Forbeststabilityovertemperatureandtime,1%metalfilm
resistors are recommended. Under trickle charge condi-
tions,thiscurrentisreducedto10%ofthefull-scalevalue.
Connecting the TIMER pin to ground disables the battery
charger.
CHRG STATUS OUTPUT PIN
THE CHARGE TIMER
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 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
this feature, connect the NTC thermistor, RNTC, between
the NTC pin and ground and a resistor, RNOM, from the
NTCpintoVNTC.RNOM shouldbea1%resistorwithavalue
equal to the value of the chosen NTC thermistor at 25°C
(this value is 10k for a Vishay NTHS0603N02N1002J
thermistor). The LTC4055 goes into hold mode when the
resistance, RHOT, of the NTC thermistor drops to 0.41
times the value of RNOM or approximately 4.1k, 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
isdesignedtogointoholdmodewhenthevalueoftheNTC
thermistor increases to 2.82 times the value of RNOM. This
resistance is RCOLD. For a Vishay NTHS0603N02N1002J
thermistor, this value is 28.2k which corresponds to
approximately 0°C. The hot and cold comparators each
have approximately 3°C of hysteresis to prevent oscilla-
tion about the trip point. Grounding the NTC pin disables
the NTC function.
0.1µF •100k
The timer starts when an input voltage greater than the
undervoltage lockout threshold level is applied, or when
leaving shutdown and the voltage on the battery is less
than the recharge threshold. At power up or exiting shut-
down with the battery voltage less than the recharge
threshold, the charge time is a full cycle. If the battery is
greaterthantherechargethreshold, thetimerwillnotstart
and charging 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.
The LTC4055 has a feature that extends charge time
automatically. Charge time is extended if the charge cur-
rent in constant-current mode is reduced due to load
current, undervoltage charge current limiting or thermal
regulation. Thischangeinchargetimeisinverselypropor-
tional to the change in charge current. As the LTC4055
approaches constant-voltage mode 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, the LTC4055 detects
4055p
16
LTC4055
U
OPERATIO
V
V
NTC
NTC
LTC4055
NTC BLOCK
LTC4055
NTC BLOCK
15
15
0.74 • V
0.74 • V
NTC
NTC
R
R
NOM
NOM
–
+
–
+
121k
100k
TOO_COLD
TOO_HOT
TOO_COLD
TOO_HOT
NTC
16
NTC
16
R1
13.3k
R
100k
NTC
–
+
–
+
0.29 • V
0.29 • V
NTC
NTC
R
100k
NTC
+
–
+
–
NTC_ENABLE
NTC_ENABLE
0.1V
0.1V
4055 F03b
4055 F03a
(3a)
(3b)
Figure 3. NTC Circuits
THERMISTORS
calculate RNOM for a shift to lower temperature for ex-
ample, use the following equation:
The LTC4055 NTC trip points were designed to work with
thermistorswhoseresistance-temperaturecharacteristics
follow Vishay Dale’s “R-T Curve 2.” The Vishay
NTHS0603N02N1002Jisanexampleofsuchathermistor.
However, Vishay Dale has many thermistor products that
followthe“R-TCurve2”characteristicinavarietyofsizes.
Furthermore, anythermistorwhoseratioofRCOLD toRHOT
isabout7.0willalsowork(VishayDaleR-TCurve2shows
a ratio of RCOLD to RHOT of 2.815/0.4086 = 6.89).
RCOLD
2.815
RNOM
=
•RNTC at 25°C
where RCOLD is the resistance ratio of RNTC at the desired
cold temperature trip point. If you want to shift the trip
points to higher temperatures use the following equation:
RHOT
0.4086
RNOM
=
•RNTC at 25°C
Power conscious designs may want to use thermistors
whoseroomtemperaturevalueisgreaterthan10k. Vishay
Dale has a number of values of thermistor from 10k to
100k that follow the “R-T Curve 1.” Using these as indi-
cated in the NTC Thermistor section will give temperature
trip points of approximately 3°C and 47°C, a delta of 44°C.
This delta in temperature can be moved in either direction
where RHOT is the resistance ratio of RNTC at the desired
hot temperature trip point.
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 RNOM
needed is calculated as follows:
by changing the value of RNOM with respect to RNTC
.
Increasing RNOM will move both trip points to lower
temperatures.LikewiseadecreaseinRNOM withrespectto
RNTC will move the trip points to higher temperatures. To
RCOLD
2.815
3.266
RNOM
=
=
•RNTC at 25°C
•100k = 116k
2.815
4055p
17
LTC4055
U
OPERATIO
The nearest 1% value for RNOM is 115k. This is the value
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, can be added in series with RNTC (see
Figure 3b). The values of the resistors are calculated as
follows:
CHARGER UNDERVOLTAGE LOCKOUT
Internal undervoltage lockout circuits monitor the VIN and
VOUT voltages and keep the charger circuits of the part
shut down until VIN or VOUT rises above the under-voltage
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
circuit keeps the charger shutdown if VBAT exceeds VOUT
.
RCOLD –RHOT
2.815 – 0.4086
0.4086
RNOM
=
If the charger UVLO comparator is tripped, the charger
circuits will not come out of shutdown until VOUT exceeds
R1=
• RCOLD –RHOT –R
HOT
(
)
V
BAT by 50mV.
2.815 – 0.4086
where RNOM is the value of the bias resistor, RHOT and
RCOLD are the values of RNTC at the desired temperature
trip points. Continuing the example from before with a
desired hot trip point of 50°C:
SHUTDOWN
The LTC4055 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
RCOLD –RHOT
(
)
RNOM
=
=
2.815 – 0.4086
2.815 – 0.4086
= 120.8k, 121k is nearest 1%
SUSPEND
0.4086
2.815 – 0.4086
The LTC4055 can be put in suspend mode by forcing the
SUSPpingreaterthan1V.Insuspendmodetheidealdiode
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 if VOUT becomes less
R1= 100k •
• 3.266 – 0.3602 – 0.3602
(
)
= 13.3k, 13.3k is nearest 1%
The final solution is as shown if Figure 3b where RNOM
121k, R1 = 13.3k and RNTC=100k at 25°C.
=
than VBAT
.
VIN and Wall Adaptor Bypass Capacitor
CURRENT LIMIT UNDERVOLTAGE LOCKOUT
Many types of capacitors can be used for input bypassing.
However, caution must be exercised when using multi-
layer ceramic capacitors. Because of the self resonant and
high Q characteristics of some types of ceramic capaci-
tors, 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.
Aninternalundervoltagelockoutcircuitmonitorstheinput
voltage and keeps the current limit circuits of the part in
shutdown mode until VIN rises above the undervoltage
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
limitUVLOcircuitkeepsthecurrentlimitshutdownifVOUT
exceeds VIN. If the current limit UVLO comparator is
tripped, the current limit circuits will not come out of
shutdown until VOUT falls 50mV below the VIN voltage.
4055p
18
LTC4055
U
OPERATIO
Thenearest1%resistoris34.8k.ThereforeR1=34.8kand
the rising trip point should be 4.48V.
Selecting WALL Input Resistors
The WALL input pin identifies the presence of a wall
adaptor. This information is used to disconnect the inputs
IN1/IN2fromtheOUTpininordertopreventbackconduc-
tion to whatever may be connected to the inputs. It also
forces the ACPR pin low when the voltage at the WALL pin
exceeds the input threshold. The WALL pin has a 1V rising
threshold and approximately 30mV of hysteresis.
34.8
10
VHYST(Adapter) ≈ 30mV • 1+
≈ 134mV
The hysteresis is going to be approximately 124mV for
this example.
Power Dissipation
Itneedstobenotedthatthisfunctionisdisabledwhenthe
only power applied to the part is from the battery. There-
fore the 1V threshold only applies when the voltage on
either IN1/IN2 or OUT is 100mV greater than the voltage
on BAT and the voltage on IN1/IN2 or OUT is greater than
the VUVLO (3.8V typ) threshold.
The conditions that cause the LTC4055 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 VOUT, the LTC4055 power dissipation is approximately:
Thewalladapterdetectionthresholdissetbythefollowing
equation:
PD = (VOUT – VBAT) • IBAT
Where PD is the power dissipated, VOUT is the supply
voltage, VBAT is the battery voltage and IBAT is the battery
charge current. It is not necessary to perform any worst-
case power dissipation scenarios because the LTC4055
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
VTH(Adapter) = VWALL • 1+
R2
R1
VHYST(Adapter) = VWALL−HYST • 1+
R2
where VTH(Adapter) is the wall adaptor detection thresh-
old, VWALL is the WALL pin rising threshold (typically 1V),
R1 is the resistor from the wall adapter input to WALL and
R2 is the resistor from WALL to GND.
TA = 105°C – PD • θJA
TA = 105°C – (VOUT – VBAT) • IBAT • θJA
Consider an example where the VTH(Adapter) is to be set
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 operating from a wall adapter with
5V at VOUT providing 0.8A to a 3V Li-Ion battery. The
ambienttemperatureabove, whichtheLTC4055willbegin
to reduce the 0.8A charge current, is approximately:
TA = 105°C – (5V – 3V) • 0.8A • 37°C/W
TA = 105°C – 1.6W • 37°C/W = 105°C – 59°C = 46°C
VTH(Adapter)
R1= R2 •
−1
VWALL
4.5
1
R1= 10k •
– 1 = 10k • 3.5 = 35k
4055p
19
LTC4055
U
OPERATIO
The LTC4055 can be used above 46°C, but the charge
current will be reduced below 0.8A. The approximate
charge current at a given ambient temperature can be
approximated by:
LTC4055 can deliver over 1A to a battery from a 5V supply
at room temperature. Without a backside thermal connec-
tion, this number could drop to less than 500mA.
STABILITY
105°C – TA
IBAT
=
The constant-voltage mode feedback loop is stable with-
out any compensation when a battery is connected. How-
ever, a 1µF capacitor with a 1Ω series resistor to GND is
recommended at the BAT pin to keep ripple voltage low
when the battery is disconnected.
V
OUT – VBAT • θ
(
)
JA
Considertheaboveexamplewithanambienttemperature
of 55°C. The charge current will be reduced to approxi-
mately:
105°C – 55°C
50°C
Ideal Diode from BAT to OUT
IBAT
=
=
= 0.675A
5V – 3V • 37°C/W 74°C/A
(
)
Forward regulation for the LTC4055 from BAT to OUT has
three operational ranges, depending on the magnitude of
the load current. For small load currents, the LTC4055 will
provide a constant voltage drop; this operating mode is
referred to as “constant VON” regulation. As the current
exceeds IFWD, the voltage drop will increase linearly with
the current with a slope of 1/RDIO,ON; this operating mode
is referred to as “constant RON” regulation. As the current
increases further, exceeding IMAX, the forward voltage
drop will increase rapidly; this operating mode is referred
to as “constant ION” regulation. The characteristics for the
following parameters: RFWD, RON, VFWD, and IFWD are
specified with the aid of Figure 4.
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 package is soldered to the
board. Correctly soldered to a 2500mm2 double-sided
1oz. copper board, the LTC4055 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
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 vs Schottky Diode Forward Voltage Drop
4055p
20
LTC4055
U
TYPICAL APPLICATIO S
LTC4055 Configured for USB Application with Wall
Adapter
allowing the input current supplied by VBUS to exceed the
500mA/100mA limits.
Figure 5 shows an LTC4055 configured for USB applica-
tions with the optional wall adaptor input. The program-
ming resistor (RCLPROG) is set to 105k which sets 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
The programming resistor (RPROG) with a value of 61.9k
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.
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
61.9k
4055 F05
Figure 5. USB Power Control Application with Wall Adapter Input
4055p
21
LTC4055
U
TYPICAL APPLICATIO S
USB Hosting Application: The LTC4055’s IN1 and IN2
application circuit. The wall adapter or the battery can still
provide power to OUT, which in turn can provide power to
VBUS when commanded from the USB controller. The
ability to charge the battery is enabled when the wall
adapter is present.
are Set Hi-Z by Pulling the SUSP Pin Above 1.2V
In applications where the power is required to go back out
on to the USB VBUS the LTC4055 can be configured to turn
off its input power path, IN1 and IN2. Forcing the SUSP
input pin above 1.2V does this. Figure 6 shows the
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
105k
4055 F06
Figure 6. USB Hosting Application
4055p
22
LTC4055
U
PACKAGE DESCRIPTIO
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
0.75 ± 0.05
R = 0.115
TYP
0.55 ± 0.20
4.00 ± 0.10
(4 SIDES)
15
16
PIN 1
TOP MARK
1
2
2.15 ± 0.10
(4-SIDES)
(UF) QFN 0503
0.30 ± 0.05
0.65 BSC
0.200 REF
0.00 – 0.05
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WGGC)
2. ALL DIMENSIONS ARE IN MILLIMETERS
3. 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
4. EXPOSED PAD SHALL BE SOLDER PLATED
4055p
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 represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
23
LTC4055
RELATED PARTS
PART NUMBER
Battery Chargers
LTC1733
DESCRIPTION
COMMENTS
Monolithic Lithium-Ion Linear Battery Charger
Lithium-Ion Linear Battery Charger in ThinSOTTM
Lithium-Ion Linear Battery Charger in ThinSOT
Switch Mode Lithium-Ion Battery Charger
Lithium-Ion Linear Battery Charger Controller
Standalone Charger with Programmable Timer, Up to 1.5A Charge Current
Simple ThinSOT Charger, No Blocking Diode, No Sense Resistor Needed
LTC1734
LTC1734L
LTC4002
Low Current Version of LTC1734; 50mA ≤ I
≤ 180mA
CHRG
Standalone, 4.7V ≤ VIN ≤ 24V, 500kHz Frequency, 3 Hour Charge Termination
LTC4050
Features Preset Voltages, C/10 Charger Detection and Programmable Timer,
Input Power Good Indication, Thermistor Interface
LTC4052
LTC4053
LTC4054
Monolithic Lithium-Ion Battery Pulse Charger
No Blocking Diode or External Power FET Required, ≤1.5A Charge Current
USB Compatible Monolithic Li-Ion Battery Charger Standalone Charger with Programmable Timer, Up to 1.25A Charge Current
Standalone Linear Li-Ion Battery Charger
with Integrated Pass Transistor in ThinSOT
Thermal Regulation Prevents Overheating, C/10 Termination,
C/10 Indicator, Up to 800mA Charge Current
LTC4057
LTC4058
LTC4059
Lithium-Ion Linear Battery Charger
Up to 800mA Charge Current, Thermal Regulation, ThinSOT Package
Standalone 950mA Lithium-Ion Charger in DFN
900mA Linear Lithium-Ion Battery Charger
C/10 Charge Termination, Battery Kelvin Sensing, ±7% Charge Accuracy
2mm × 2mm DFN Package, Thermal Regulation, Charge Current Monitor
Output
LTC4411/LTC4412 Low Loss PowerPathTM Controller in ThinSOT
Automatic Switching Between DC Sources, Load Sharing,
Replaces ORing Diodes
Power Management
LTC3405/LTC3405A 300mA (I ), 1.5MHz, Synchronous Step-Down
95% Efficiency, V = 2.7V to 6V, V
ThinSOT Package
= 0.8V, I = 20µA, I < 1µA,
OUT Q SD
OUT
IN
DC/DC Converter
LTC3406/LTC3406A 600mA (I ), 1.5MHz, Synchronous Step-Down
95% Efficiency, V = 2.5V to 5.5V, V
ThinSOT Package
= 0.6V, I = 20µA, I < 1µA,
Q SD
OUT
IN
OUT
OUT
OUT
DC/DC Converter
LTC3411
LTC3440
1.25A (I ), 4MHz, Synchronous Step-Down
DC/DC Converter
95% Efficiency, V = 2.5V to 5.5V, V
= 0.8V, I = 60µA, I < 1µA,
Q SD
OUT
IN
MS10 Package
600mA (I ), 2MHz, Synchronous Buck-Boost
95% Efficiency, V = 2.5V to 5.5V, V
= 2.5V, I = 25µA, I < 1µA,
Q SD
OUT
IN
DC/DC Converter
MS Package
ThinSOT and PowerPath are trademarks of Linear Technology Corporation.
4055p
LT/TP 0104 1K • PRINTED IN THE USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
24
●
●
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
LINEAR TECHNOLOGY CORPORATION 2004
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