LINER LTC4055-1 Usb power controller and li-ion charger Datasheet

LTC4055/LTC4055-1
USB Power Controller
and Li-Ion Charger
FEATURES
DESCRIPTION
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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
and battery charging. Depending on the state of the current
select pin (HPWR), total input current can be limited to
either 100mA or 500mA. The voltage drop from the USB
supply or battery to the USB peripheral is typically less than
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.
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APPLICATIONS
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Portable USB Devices: Cameras, MP3 Players, PDAs
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.
The LTC4055/LTC4055-1 include a complete constantcurrent/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
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.
The LTC4055/LTC4055-1 are available in a 16-pin low
profile (4mm × 4mm) QFN package.
TYPICAL APPLICATION
Input and Battery Current vs Load Current
RPROG = RCLPROG = 97.6k
600
5V (NOM)
FROM USB
CABLE VBUS
1Ω
IN1
OUT
IN2
BAT
VNTC
10μF
TO SYSTEM
LOADS
+
NTC
WALL
CHRG
LTC4055
ACPR
SHDN
SUSPEND USB POWER
SUSP
500mA/100mA SELECT
HPWR
10μF
Li-Ion
CELL
400
ILOAD
300
200
IBAT
CHARGING
100
TIMER PROG
0.1μF
IIN
500
CURRENT (mA)
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Charges Single-Cell Li-Ion Batteries Directly from
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 500mA/100mA Current Limit
Low Loss Full PowerPath™ Control with Ideal Diode
Operation (Reverse Current Blocking)
Preset 4.2V Charge Voltage with 0.8% Accuracy
(4.1V for LTC4055-1)
4.1V Float Voltage (LTC4055-1) Improves Battery Life
and High Temperature Safety Margin
USB-Compliant Suspend Mode
Programmable Charge Current and Termination Timer
Soft-Start Limits Inrush Current
NTC Thermistor Input for Temperature Qualified
Charging
Tiny (4mm × 4mm × 0.75mm) QFN Package
CLPROG
97.6k
GND
97.6k
0
–100
4055 TA01
IBAT
(IDEAL DIODE)
0
100
200
300
400
ILOAD (mA)
500
600
4055 TA02
4055fb
1
LTC4055/LTC4055-1
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Notes 1, 2, 3, 4, 5)
ACPR
CHRG
VNTC
NTC
TOP VIEW
16 15 14 13
IN2 1
12 TIMER
BAT 2
11 PROG
17
OUT 3
10 GND
6
7
8
SUSP
HPWR
9 CLPROG
5
WALL
IN1 4
SHDN
Terminal Voltage
IN1, IN2, OUT, BAT .................................. –0.3V to 6V
NTC, VNTC , TIMER,
PROG, CLPROG ..................... –0.3V to (VCC + 0.3V)
CHRG, HPWR, SUSP, SHDN,
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
Storage Temperature Range.................. –65°C to 125°C
UF PACKAGE
16-LEAD (4mm s 4mm) PLASTIC QFN
TJMAX = 125°C, θJA = 37°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC4055EUF#PBF
LTC4055EUF#TRPBF
4055
16-Lead (4mm × 4mm) Plastic QFN
–40°C to 85°C
LTC4055EUF-1#PBF
LTC4055EUF-1#TRPBF
40551
16-Lead (4mm × 4mm) Plastic QFN
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
ELECTRICAL CHARACTERISTICS
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
VIN
VBAT
IIN
PARAMETER
Input Supply Voltage
Input Voltage
Input Supply Current
IOUT
IBAT
Output Supply Current
Battery Drain Current
ILIM(MAX)
VUVLO
Maximum Current Limit
Input or Output Undervoltage Lockout
ΔVUVLO
Input or Output Undervoltage Lockout
Hysteresis
CONDITIONS
IN1, IN2 and OUT
BAT
VBAT = 4.2V
Suspend Mode
Suspend Mode, Wall = 2V, VOUT = 4.8V
Shutdown
VOUT = 5V, VIN1 = VIN2 = 0V, VBAT = 4.2V
VBAT = 4.2V, Charging Stopped
Suspend Mode
Shutdown
VIN1 = VIN2 = 0V, BAT Powers OUT, No Load
(Note 8)
VIN Powers Part, Rising Threshold
VOUT Powers Part, Rising Threshold
VIN Rising – VIN Falling or
VOUT Rising – VOUT Falling
l
MIN
4.35
TYP
l
l
l
l
l
l
l
l
l
l
l
l
3.5
3.5
0.8
50
0.1
10
450
15
15
2.5
50
1
3.8
3.8
125
MAX
5.5
4.3
1.6
100
0.2
20
900
30
30
5
100
4
4
UNITS
V
V
mA
μA
mA
μA
μA
μA
μA
μA
μA
A
V
V
mV
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
Current Limit
ILIM
PARAMETER
CONDITIONS
Current Limit
RON
ON Resistance VIN to VOUT
VPROG
Programming Pin Voltage
(PROG, CLPROG)
Soft-Start Inrush Current
Input Current Limit Enable Threshold
Input Current Limit Enable Threshold
Automatic Limit Enable Threshold
Voltage
RCLPROG = 100k, HPWR = 5V
RCLPROG = 100k, HPWR = 0V
HPWR = 5V, 400mA Load
HPWR = 0V, 80mA Load
RCLPROG = RPROG = 100k
RCLPROG = RPROG = 50k
IN or OUT
VIN Rising
VIN Rising – VIN Falling
(VIN – VOUT) VIN Rising
(VIN – VOUT) VIN Falling
ISS
VCLEN
ΔVCLEN
VALEN
Battery Charger
Regulated BAT Voltage
VFLOAT
IBAT
IBAT(MAX)
ΔIB/ΔIO
ITRKL
VTRKL
VCENI
VCENO
VUVCL
VRECHRG
tTIMER
TLIM
(0°C to 85°C) IBAT = 2mA (LTC4055)
IBAT = 2mA (LTC4055)
(0°C to 85°C). IBAT = 2mA (LTC4055-1)
IBAT = 2mA (LTC4055-1)
Current Mode Charge Current
RPROG = 100k, HPWR = 5V, No Load
RPROG = 100k, HPWR = 0V, No Load
RPROG = 100k, VOUT = 5V, VIN = 0V,
VWALL = 2V
RPROG = 50k, HPWR = 5V, No Load
RPROG = 50k, VOUT = 5V, VIN = 0V,
VWALL = 2V
Maximum Charge Current
(Note 8)
Charge Current Load Dependency
ΔIBAT/ΔIOUT , IOUT = 100mA
Trickle-Charge Current
VBAT = 2V, RPROG = 100k
Trickle-Charge Threshold Voltage
VBAT Rising
Input Charger Enable Threshold
(VIN – VBAT) High to Low
Voltage
(VIN – VBAT) Low to High
Output Charger Enable Threshold
(VOUT – VBAT) High to Low
Voltage
(VOUT – VBAT) Low to High
Input/Output Undervoltage Current Limit IBAT = ICHG/2
Recharge Battery Threshold Voltage
VFLOAT – VRECHRG
TIMER Accuracy
CTIMER = 0.1μF
Recharge Time
Percent of Total Charge Time
Low Battery Trickle-Charge Time
Percent of Total Charge Time, VBAT < 2.8V
Junction Temperature in Constant
Temperature Mode
Ideal Diode
RFWD
RDIO,ON
VFWD
On Resistance, VON Regulation
On Resistance VBAT to VOUT
Voltage Forward Drop (VBAT – VOUT)
VOFF
IFWD
IMAX
Diode Disable Battery Voltage
Load Current Limit for VON Regulation
Diode Current Limit
VBAT = 3.5V, 100mA Load
VBAT = 3.5V, 600mA Load
VBAT = 3.5V, 5mA Load
VBAT = 3.5V, 100mA Load
VBAT = 3.5V, 600mA
VBAT Falling
VIN = 3.5V
VBAT = 3.5V, VOUT = 2.8V, Pulsed with
10% Duty Cycle
MIN
TYP
MAX
UNITS
l
l
465
89
515
105
l
l
0.98
0.98
l
3.5
25
–75
490
97
0.2
0.2
1.000
1.000
5
3.8
125
50
–50
mA
mA
Ω
Ω
V
V
mA/μs
V
mV
mV
mV
l
l
l
4.165
4.158
4.066
4.059
445
45
445
4.200
4.200
4.100
4.100
485
80
485
4.235
4.242
4.134
4.141
525
110
525
V
V
V
V
mA
mA
mA
l
l
900
900
980
980
1060
1060
mA
mA
l
l
l
l
l
l
l
0.95
30
2.7
4.23
65
10
1.4
1
1
45
2.85
70
80
70
80
4.3
100
±10
50
25
105
0.1
0.2
30
55
120
2.8
550
1.8
1.02
1.02
4
75
–25
1.05
60
3
4.37
135
50
2.2
A
mA/mA
mA
V
mV
mV
mV
mV
V
mV
%
%
%
°C
Ω
Ω
mV
mV
mV
V
mA
A
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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
VOL
VIH
VIL
IPULLDN
VCHG,SD
ICHG,SD
VWALL
VWALL,HYS
IWALL
NTC
IVNTC
VVNTC
VCOLD
VHOT
VDIS
PARAMETER
CONDITIONS
Output Low Voltage (CHRG, ACPR)
Enable Input High Voltage
Enable Input Low Voltage
Logic Input Pull-Down Current
Charger Shutdown Threshold Voltage
on TIMER
Charger Shutdown Pull-Up Current
on TIMER
Wall Input Threshold Voltage
Wall Input Hysteresis
Wall Input Leakage Current
ISINK = 5mA
SUSP, SHDN, HPWR Pin Low to High
SUSP, SHDN, HPWR Pin High to Low
SUSP, SHDN, HPWR
TIMER Falling
l
l
0.15
VTIMER = 0V
l
2
4
VWALL Rising Threshold
VWALL Rising – VWALL Falling Threshold
VWALL = 1V
l
0.98
1.000
35
0
1.02
VNTC Pin Current
VNTC Bias Voltage
Cold Temperature Fault Threshold
Voltage
Hot Temperature Fault Threshold
Voltage
NTC Disable Voltage
VVNTC = 2.5V
IVNTC = 500μA
Rising Threshold
Falling Threshold
Falling Threshold
Rising Threshold
NTC Input Voltage to GND (Falling)
Hysteresis
l
2.5
3.8
0.74 • VVNTC
0.72 • VVNTC
0.29 • VVNTC
0.30 • VVNTC
100
50
3.5
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: VCC is the greater of VIN1, VOUT or VBAT .
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.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
MIN
TYP
MAX
0.2
0.4
1.2
l
l
0.4
2
l
1.5
3.4
l
75
0.4
UNITS
V
V
V
μA
V
μA
±50
125
V
mV
nA
mA
V
V
V
V
V
mV
mV
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 7: Guaranteed by long-term current density limitations.
Note 8: Accuracy of programmed current may degrade for currents greater
than 1A.
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4
LTC4055/LTC4055-1
TYPICAL PERFORMANCE CHARACTERISTICS
Input Supply Current
vs Temperature
800
700
60
VIN = 5V
VBAT = 4.2V
RPROG = RCLPROG = 100k
50
60
VIN = 0V
VBAT = 4.2V
50
600
40
IIN (μA)
IIN (μA)
70
VIN = 5V
VBAT = 4.2V
RPROG = RCLPROG = 100k
SUSP = 5V
500
400
IBAT (μA)
900
Battery Drain Current
vs Temperature
(BAT Powers OUT, No Load)
Input Supply Current
vs Temperature (Suspend Mode)
30
20
300
40
30
20
200
10
10
100
0
–50
–25
0
25
50
TEMPERATURE (°C)
0
–50
100
75
–25
0
25
50
TEMPERATURE (°C)
75
Input Current Limit
vs Temperature, HPWR = 5V
505
–25
50
25
0
TEMPERATURE (°C)
4055 G03
Input Current Limit
vs Temperature, HPWR = 0V
105.0
VIN = 5V
VBAT = 3.5V
RPROG = RCLPROG = 100k
102.5
100
75
4055 G02
4055 G01
515
0
–50
100
RON vs Temperature
250
VIN = 5V
VBAT = 3.5V
RPROG = RCLPROG = 100k
ILOAD = 400mA
225
VIN = 5V
485
475
465
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
200
RON (mΩ)
495
IIN (mA)
IIN (mA)
100.0
97.5
92.5
125
50
25
75
0
TEMPERATURE (°C)
100
1.010
1.010
1.005
1.005
0.985
0.985
0
50
25
TEMPERATURE (°C)
75
100
4055 G07
0.980
–50
125
VIN = 5V
LTC4055
4.2
0.995
0.990
–25
4.3
VIN = 5V
RCLPROG = 100k
1.000
0.990
0.980
–50
100
Battery Regulated Output (Float)
Voltage vs Temperature
VFLOAT (V)
1.015
VCLPROG (V)
VPROG (V)
1.020
0.995
50
25
75
0
TEMPERATURE (°C)
4055 G06
CLPROG Pin Voltage
vs Temperature
VIN = 5V
RPROG = 100k
1.000
100
–50 –25
125
4055 G05
PROG Pin Voltage vs Temperature
1.015
VIN = 5.5V
150
4055 G04
1.020
175
95.0
90.0
–50 –25
125
VIN = 4.5V
LTC4055-1
4.1
–25
0
50
25
TEMPERATURE (°C)
75
100
4055 G08
4.0
–50
–25
0
50
25
TEMPERATURE (oC)
75
100
4055 G09
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LTC4055/LTC4055-1
TYPICAL PERFORMANCE CHARACTERISTICS
Regulated Output VoltageRecharge Threshold Voltage
vs Temperature
120
Battery Regulated Output (Float)
Voltage vs Supply Voltage
4.3
VIN = 5V
Battery Current and Voltage
vs Time (LTC4055)
600
TA = 25°C
110
LTC4055
95
IBAT (mA)
VFLOAT (V)
100
LTC4055-1
4.1
400
4
300
3
200
2
0.8AHr CELL
VIN = 5V
TA = 25°C
RPROG = 105k
90
100
85
80
–50
–25
0
50
25
TEMPERATURE (°C)
100
75
4.0
4.5
4.75
5
0
5.5
5.25
VIN (V)
100
4055 G12
Undervoltage Current Limit,
Charging from VIN, IBAT vs VIN
1.6
VIN = 5V
VOUT = NO LOAD
RPROG = 100k
RCLPROG = 100k
HPWR = 0
TA = 25°C
80
300
60
RPROG = 34k
1.2
RPROG = 50k
40
RPROG = 100k
0.4
0
1
1.5
2 2.5
VBAT (V)
3
3.5
4
0
4.5
0.5
1
1.5
2 2.5
VBAT (V)
3
3.5
RPROG = 100k
HPWR = 0
1000
RPROG = 50k
VBAT = 3.5V
VIN = 0V
900
800
0.7
700
0.6
600
IOUT (mA)
0.8
RPROG = 100k
0.4
0.3
1000
25°C
0
–50
800
125°C
75°C
400
–25
50
25
0
75
TEMPERATURE (°C)
100
125
4055 G16
700
600
500
400
300
200
200
100
100
0
0
4.420
VBAT = 3.5V
VIN = 0V
TA = 25°C
900
0°C
–50°C
500
4.380
Ideal Diode Forward Voltage and
Resistance vs Current
300
VIN = 5V
VBAT = 3.5V
QJA = 37°C/W
4.340
4055 G15
Ideal Diode Forward Voltage
vs Current and Temperature
1.0
4.300
4055 G14
Charge Current vs Temperature
(Thermal Regulation)
0.5
0
4.260
4.5
VIN (V)
4055 G13
0.9
4
IOUT (mA), RDIO (mΩ)
0.5
0
IBAT (A)
0.8
0.2
0
0.1
1.0
0.6
20
100
TA = 25°C
1.4
200
0.2
1
0
20 40 60 80 100 120 140 160 180 200
TIME (MINUTES)
Charging from USB, Low Power,
IBAT vs VBAT (LTC4055)
IBAT (mA)
400
IBAT
4055 G11
VIN = 5V
VOUT = NO LOAD
RPROG = 100k
RCLPROG = 100k
HPWR = 1
TA = 25°C
500
0
IBAT (A)
600
6
5.75
4055 G10
Charging from USB, IBAT
vs VBAT (LTC4055)
5
VBAT
4.2
105
IBAT (mA)
CHRG
500
VBAT AND VCHRG (V)
VFLOAT-VRECHARGE (V)
115
6
20 40 60 80 100 120 140 160 180 200
VFWD (mV)
4055 G17
0
RDIO(ON)
RFWD
0
20 40 60 80 100 120 140 160 180 200
VFWD (mV)
4055 G18
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LTC4055/LTC4055-1
TYPICAL PERFORMANCE CHARACTERISTICS
Ideal Diode and Schottky Diode
Forward Voltage vs Current
Input Connect Waveforms
Input Disconnect Waveforms
IOUT (mA)
1000
VBAT = 3.5V
900 VIN = 0V
T = 25°C
800 A
VIN
5V/DIV
VIN
5V/DIV
700
VOUT
5V/DIV
600
IIN
0.5A/DIV
VOUT
5V/DIV
IIN
0.5A/DIV
IBAT
0.5A/DIV
IBAT
0.5A/DIV
500
400
SCHOTTKY
300
200
VBAT = 3.5V
IOUT = 100mA
100
0
0
1ms/DIV
VBAT = 3.5V
IOUT = 100mA
4055 G20
1ms/DIV
4055 G22
50 100 150 200 250 300 350 400 450
VFWD (mV)
4055 G19
WALL Connect Waveforms
(VIN = 0V)
Response to HPWR
WALL Disconnect Waveforms
(VIN = 0V)
WALL
5V/DIV
OUT
5V/DIV
WALL
5V/DIV
OUT
5V/DIV
HPWR
5V/DIV
IIN
0.5A/DIV
IBAT
0.5A/DIV
VBAT = 3.5V
IOUT = 50mA
250μs/DIV
IWALL
0.5A/DIV
IWALL
0.5A/DIV
IBAT
0.5A/DIV
IBAT
0.5A/DIV
VBAT = 3.5V
IOUT = 100mA
RPROG = 57.6k
4055 G21
SUSPEND
5V/DIV
OUT
5V/DIV
IIN
0.5A/DIV
IBAT
0.5A/DIV
1ms/DIV
VBAT = 3.5V
IOUT = 100mA
RPROG = 57.6k
4055 G24
WALL Connect Waveforms
(VIN = 5V)
Response to Suspend
VBAT = 3.5V
IOUT = 50mA
1ms/DIV
4055 G23
WALL
5V/DIV
IIN
0.5A/DIV
IWALL
0.5A/DIV
IWALL
0.5A/DIV
IBAT
0.5A/DIV
IBAT
0.5A/DIV
1ms/DIV
4055 G25
WALL Disconnect Waveforms
(VIN = 5V)
WALL
5V/DIV
IIN
0.5A/DIV
VBAT = 3.5V
IOUT = 100mA
RPROG = 57.6k
1ms/DIV
4055 G26
VBAT = 3.5V
IOUT = 100mA
RPROG = 57.6k
1ms/DIV
4055 G27
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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
when supplying power to OUT. When the OUT pin potential
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 resistor
divider sets the final float potential on this pin. The internal
resistor divider is disconnected when IN1/IN2 and OUT
are in UVLO.
OUT (Pin 3): Voltage Output. Used to provide controlled
power to a USB device from either USB VBUS (IN1/IN2) or
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.
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 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.
WALL (Pin 5): Wall Adapter Present Input. Pulling this pin
above 1V will disable charging from IN1/IN2 and disconnect
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.
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.
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
VOUT 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.
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.
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:
ICL ( A) =
VCLPROG
49, 000 V
• 49, 000 =
RCLPROG
RCLPROG
In USB applications the resistor RCLPROG should be set
to no less than 105k.
GND (Pin 10): Ground.
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:
ICHG( A) =
VPROG
48, 500 V
• 48, 500 =
RPROG
RPROG
4055fb
8
LTC4055/LTC4055-1
PIN FUNCTIONS
TIMER (Pin 12): Timer Capacitor. Placing a capacitor CTIMER
to GND sets the timer period. The timer period is:
t TIMER(Hours) =
CTIMER • RPROG • 3 Hours
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
above the input threshold and power is present on IN1/IN2
or OUT (i.e., above UVLO threshold).
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.
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.
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 VNTC . When the voltage on this pin is above 0.74
• VVNTC (Cold, 0°C) or below 0.29 • VVNTC (Hot, 50°C)
the timer is suspended, but not cleared, the charging is
disabled and the CHRG pin remains in its former state.
When the voltage 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.
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
VBUS
4
3
IN1
2
1
BAT
OUT
IN2
–+
25mV IDEAL
DIODE
IN1 0.2Ω OUT
DIE
TEMP
105°C
4.35V
–
+
–
TA
+
VR
SOFT-START
1V
ILIM CNTL
ENABLE
–
CLPROG
SENSE
CURRENT CONTROL
SOFT-START2
I/O SEL
+
8
13
ENABLE
1V
BATTERY CHARGER
–
11
CHARGER
CC/CV REGULATOR
ICHRG
100k
100k
BAT 0.2Ω IN2
CURRENT LIMIT
+
ILIM
9
0.2Ω
+
PROG
HPWR
500mA/100mA
2μ
ACPR
–
0.25V
+
2.8V
BATTERY
UVLO
BAT UV
–
5
WALL
IN1 OUT BAT
+
+
1V
VOLTAGE DETECT
–
4.1V
RECHARGE
(4.0V
LTC4055-1)
–
UVLO
BAT UV
15
VNTC
RECHRG
TIMER
OSCILLATOR
–
100k
HOLD
2COLD
16
NTCERR
+
NTC
12
CONTROL LOGIC
RESET
CHRG
CLK
COUNTER
14
STOP
NTC
–
100k
2HOT
+
+
NTC ENABLE
0.1V
2μ
2μ
–
10
GND
6
SHDN
7
SUSP
4055 BD
4055fb
10
LTC4055/LTC4055-1
OPERATION
The LTC4055/LTC4055-1are complete PowerPath controllers for battery-powered USB applications. The LTC4055/
LTC4055-1 are designed to provide device power and Li-ion
battery charging from the USB VBUS while maintaining
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.
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, the battery remains fully charged until bus power
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.
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 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.
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
power Schottky or FET, as shown in Figure 1. The LTC4055/
LTC4055-1 have 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 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.
WALL
ADAPTER
VBUS
4
1
IN1
OUT
IN2
LOAD
INPUT CHARGER
CONTROL
CURRENT LIMIT
CONTROL
OUTPUT CHARGER
CONTROL
ENABLE
ENABLE
ENABLE
IDEAL
BAT
5
3
2
+
WALL
+
1V
–
Li-Ion
UVLO
4055 F01
Figure 1. Simplified Block Diagram—PowerPath
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11
LTC4055/LTC4055-1
OPERATION
Table 1. Operating Modes—PowerPath States Current Limited Input Power (IN1/IN2 to OUT)
WALL PRESENT SHUTDOWN
SUSPEND
VIN > 3.8V
VIN > (VOUT + 100mV)
VIN > (VBAT + 100mV)
CURRENT LIMIT ENABLED
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
N
X
X
X
X
N
X
N
X
X
X
X
X
N
N
N
N
N
Y
Y
Y
Y
SUSPEND
VIN > 4.35V
VIN > (VOUT + 100mV)
VIN > (VBAT + 100mV)
INPUT CHARGER ENABLED
Input Powered Charger (IN1/IN2 to BAT)
WALL PRESENT SHUTDOWN
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
N
X
X
X
X
N
X
N
X
X
X
X
X
N
N
N
N
N
Y
Y
Y
Y
SUSPEND
VIN > 4.35V
VOUT > (VIN + 100mV)
VOUT > (VBAT + 100mV)
OUTPUT CHARGER ENABLED
Output Powered Charger (OUT to BAT)
WALL PRESENT SHUTDOWN
N
X
X
X
X
X
N
X
Y
X
X
X
X
N
X
X
X
N
X
X
N
X
X
X
X
N
X
N
X
X
X
X
X
N
N
Y
N
X
Y
Y
Y
Y
SUSPEND
VBAT > 2.8V
VBAT > VOUT
VIN
DIODE ENABLED
X
X
N
Ideal Diode (BAT to OUT)
WALL PRESENT SHUTDOWN
X
Y
X
X
X
X
X
N
X
X
N
X
X
X
X
N
X
N
X
N
X
Y
Y
X
Y
Table 2. Operating Modes—Pin Currents vs Programmed Currents (Charging from IN1/IN2)
PROGRAMMING
OUTPUT CURRENT
BATTERY CURRENT
INPUT CURRENT
ICL = ICHG
IOUT < ICL
IOUT = ICL = ICHG
IOUT > ICL
IBAT = ICHG – IOUT
IBAT = 0
IBAT = ICL – IOUT
IIN = IQ + ICL
IIN = IQ + ICL
IIN = IQ + ICL
ICHG < ICL
IOUT < (ICL – ICHG)
IOUT > (ICL – ICHG)
IOUT = ICL
IOUT > ICL
IBAT = ICHG
IBAT = ICL – IOUT
IBAT = 0
IBAT = ICL – IOUT
IIN = IQ + ICHG + IOUT
IIN = IQ + ICL
IIN = IQ + ICL
IIN = IQ + ICL
ICL < ICHG
IOUT < ICL
IOUT > ICL*
IBAT = ICL – IOUT
IBAT = ICL – IOUT
IIN = IQ + ICL
IIN = IQ + ICL
*Charge current shuts off when VOUT drops below VBAT , i.e., when IOUT exceeds ICL.
4055fb
12
VOUT < VBAT
VOUT > VBAT
VOUT < VBAT
BATTERY POWERS VOUT
• CHARGING SUSPENDED
• CHRG PULLED LOW
VIN POWERS PART
LOW BATTERY
BATTERY < 2.8V
WALL ADAPTER PRESENT
BATTERY < 4.1V
(4.0V LTC4055-1)
TEMP NOT OK
• CHRG IS Hi-Z
• BATTERY POWER TO VOUT—DISABLED
BAD BATTERY
• BATTERY CHARGING ON
• CHARGE CURRENT C/10
• VOUT CHARGE SWITCH OPEN
• CHRG PULLED LOW
• BATTERY POWER TO VOUT IS OFF
VIN CHARGING LOW BATTERY
TEMP OK AND
BATTERY < 2.8V
1/4 TIMEOUT
AND
BATTERY < 2.8V
WALL ADAPTER PRESENT
• CHRG IS Hi-Z
• BATTERY POWER TO VOUT—DISABLED
BAD BATTERY
• CURRENT LIMIT SWITCH FROM VIN TO VOUT—OFF
• BATTERY CHARGING ON
• CHARGE CURRENT C/10
• VIN CHARGE SWITCH OPEN
• CHRG PULLED LOW
• ACPR PULLED LOW
4055 SD
BATTERY > 2.8V
TEMP OK AND
BATTERY < 2.8V
VOUT CHARGING LOW BATTERY
TEMP NOT OK
NTC FAULT
BATTERY < 2.8V
TEMP OK AND
BATTERY > 2.8V
• BATTERY CHARGING SUSPENDED
• CHRG PULLED LOW
BATTERY < 2.8V
TEMP NOT OK
NTC FAULT
TEMP NOT OK
• BATTERY CHARGING SUSPENDED
• CHRG PULLED LOW
TEMP OK AND
BATTERY > 2.8V
• CURRENT LIMIT SWITCH FROM VIN TO VOUT—OFF
• BATTERY CHARGING ON
• VIN CHARGE SWITCH OPEN
• CHRG PULLED LOW
• ACPR PULLED LOW
WALL ADAPTER PRESENT
BATTERY > 4.1V
(4.0V LTC4055-1)
AND CHARGER
TIMED OUT
• CURRENT LIMIT SWITCH FROM
VIN TO VOUT—OFF
• ACPR PULLED LOW
VOUT POWERS PART
WALL ADAPTER PRESENT
• CURRENT LIMIT SWITCH FROM VIN TO VOUT—ON
• BATTERY CHARGING ON
• VIN CHARGE SWITCH OPEN
• CHRG PULLED LOW
1/4 TIMEOUT
AND
BATTERY < 2.8V
• CHRG IS Hi-Z
• BATTERY POWER TO VOUT—DISABLED
BATTERY > 2.8V
BATTERY > 4.1V
(4.0V LTC4055-1)
AND CHARGER
TIMED OUT
UVLO
• CHARGING DISABLED
• BATTERY POWERS VOUT
SHDN
VOUT CHARGING BATTERY
BATTERY < 4.1V
(4.0V LTC4055-1)
• CURRENT LIMIT SWITCH FROM
VIN TO VOUT—ON
SHUTDOWN
• CHARGING DISABLED
• ALL SWITCHES OPEN
VIN CHARGING BATTERY
BATTERY > 2.8V
VOUT > VBAT
BATTERY POWERS VOUT
• CHARGING SUSPENDED
• CHRG Hi-Z
POWER APPLIED TO VIN
(VIN AND VOUT) < UVLO
SHUTDOWN
Operational State Diagram
LTC4055/LTC4055-1
OPERATION
4055fb
13
LTC4055/LTC4055-1
OPERATION
USB CURRENT LIMIT AND CHARGE CURRENT
CONTROL
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
IOUT . The programmed current limit, ICL is defined as:
⎛ 49, 000
⎞ 49, 000 V
ICL = ⎜⎜
• VCLPROG ⎟⎟ =
⎝ RCLPROG
⎠ RCLPROG
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 programmed battery charge current, ICHG , is defined as:
PROGRAMMING CURRENT LIMIT
⎛ 48, 500
⎞ 48, 500 V
ICHG = ⎜⎜
• VPROG ⎟⎟ =
⎝ RPROG
⎠ RPROG
The formula for programming current limit is:
Input current, IIN , is equal to the sum of the BAT pin output
current and the OUT pin output current.
IIN = IOUT + IBAT
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).
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
600
RCLPROG =
1V
• 49, 000 = 100k
490mA
In USB applications, the minimum value for RCLPROG should
be 105k. This will prevent the application current from
600
500
200
IBAT
CHARGING
40
20
0
0
100
200
300
400
ILOAD (mA)
500
600
IBAT
(IDEAL DIODE)
4055 F02a
(2a) High Power Mode/Full Charge
(RPROG = RCLPROG = 97.6k)
ILOAD
60
100
0
400
–20
CURRENT (mA)
ILOAD
300
IIN
IIN
80
CURRENT (mA)
CURRENT (mA)
For example, if typical 490mA current limit is required,
calculate:
100
400
VCLPROG
• 49, 000
RCLPROG
where VCLPROG is the CLPROG pin voltage and RCLPROG is
the total resistance from the CLPROG pin to ground.
120
IIN
500
–100
ICL = ICLPROG • 49, 000 =
IBAT
CHARGING
ILOAD
300
IBAT = ICHG
200
IBAT
CHARGING
100
IBAT = ICL – IOUT
0
0
20
40
60
80
ILOAD (mA)
100
120
IBAT
(IDEAL DIODE)
–100
0
100
4055 F02b
(2b) Low Power Mode/Full Charge
(RPROG = RCLPROG = 97.6k)
200
300
400
ILOAD (mA)
500
600
IBAT
(IDEAL DIODE)
4055 F02c
(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
and 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).
For best stability over temperature and time, 1% metal
film resistors are recommended.
Battery Charger
The battery charger circuits of the LTC4055/LTC4055-1
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 output
provides information regarding the charging status of the
LTC4055/LTC4055-1 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
preset value of approximately 105°C. This feature protects
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 damaging 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.
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.
The charge cycle begins when the voltage at the input
(IN1/IN2) rises above the input UVLO level and the battery
voltage is below the recharge threshold. No charge current
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-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/LTC4055-1 switches to constant-voltage mode.
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-current 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
final float potential, the internal bandgap reference, voltage
amplifier and the resistor divider provide regulation with
±1% maximum accuracy.
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,
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
dead battery is replaced with a discharged battery), simply
remove the input voltage and reapply it, cycle the TIMER
pin to 0V or cycle the SHDN pin to 0V.
PROGRAMMING CHARGE CURRENT
The formula for programming the battery charge current,
when not being limited, is:
ICHG = IPROG • 48, 500 =
VPROG
• 48, 500
RPROG
4055fb
15
LTC4055/LTC4055-1
OPERATION
where VPROG is the PROG pin voltage and RPROG is the
total resistance from the PROG pin to ground.
For example, if typical 485mA charge current is required,
calculate:
RPROG =
1V
• 48, 500 = 100k
485mA
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 fullscale value.
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:
t TIMER(Hours) =
CTIMER • RPROG • 3 Hours
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 shutdown
with the battery voltage less than the recharge threshold,
the charge time is a full cycle. If the battery is greater than
the recharge threshold, the timer will not start 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/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 limiting or thermal regulation. This change in charge time is
inversely proportional to the change in charge current. As
the LTC4055/LTC4055-1 approach 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/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.
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.
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.
NTC Thermistor
The battery temperature is measured by placing a negative
temperature coefficient (NTC) thermistor close to the
battery pack. The NTC circuitry is shown in Figure 3. To use
this feature, connect the NTC thermistor, RNTC , between
the NTC pin and ground and a resistor, RNOM , from the
NTC pin to VNTC . RNOM should be a 1% resistor with a
value equal to the value of the chosen NTC thermistor at
25°C (this value is 10k for a Vishay NTHS0603N02N1002J
thermistor). The LTC4055/LTC4055-1 go 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/
LTC4055-1 are designed to go into hold mode when the
value of the NTC 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 oscillation about the trip point. Grounding the
NTC pin disables the NTC function.
4055fb
16
LTC4055/LTC4055-1
OPERATION
VNTC
RNOM
100k
NTC
VNTC
LTC4055/LTC4055-1
NTC BLOCK
15
0.74 • VNTC
LTC4055/LTC4055-1
NTC BLOCK
15
RNOM
121k
NTC
–
TOO_COLD
0.74 • VNTC
–
TOO_COLD
16
+
16
+
RNTC
100k
–
R1
13.3k
–
TOO_HOT
TOO_HOT
0.29 • VNTC
0.29 • VNTC
+
RNTC
100k
+
+
+
NTC_ENABLE
NTC_ENABLE
0.1V
–
0.1V
–
4055 F03b
4055 F03a
(3a)
(3b)
Figure 3. NTC Circuits
THERMISTORS
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).
Power conscious designs may want to use thermistors
whose room temperature value is greater than 10k. Vishay
Dale has a number of values of thermistor from 10k to 100k
that follow the “R-T Curve 1.” Using these as indicated
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 by
changing the value of RNOM with respect to RNTC . Increasing
RNOM will move both trip points to lower temperatures.
Likewise a decrease in RNOM with respect to RNTC will
move the trip points to higher temperatures. To calculate
RNOM for a shift to lower temperature for example, use
the following equation:
RNOM =
RCOLD
• RNTC at 25°C
2.815
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:
RNOM =
RHOT
• RNTC at 25°C
0.4086
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:
RCOLD
• RNTC at 25°C
2.815
3.266
=
• 100k = 116k
2.815
RNOM =
4055fb
17
LTC4055/LTC4055-1
OPERATION
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:
RCOLD – RHOT
2.815 – 0.4086
0.4086
⎛
⎞
R1 = ⎜
⎟ • (RCOLD – RHOT ) – RHOT
⎝ 2.815 – 0.4086 ⎠
RNOM =
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:
RCOLD – RHOT 100k • (3.266 – 0.3602)
=
2.815 – 0.4086
2.815 – 0.4086
= 120.8k, 121k is nearest 1%
RNOM =
⎡⎛
⎤
0.4086
⎞
R1 = 100k • ⎢⎜
⎟ • (3.266 – 0.3602) – 0.3602⎥
⎦
⎣⎝ 2.815 – 0.4086 ⎠
= 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.
CURRENT LIMIT UNDERVOLTAGE LOCKOUT
An internal undervoltage lockout circuit monitors the input
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
limit UVLO circuit keeps the current limit shutdown if
VOUT 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.
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 undervoltage
lockout threshold. The charger UVLO circuit has a builtin 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 .
If the charger UVLO comparator is tripped, the charger
circuits will not come out of shutdown until VOUT exceeds
VBAT by 50mV.
SHUTDOWN
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.
SUSPEND
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
if VOUT becomes less than VBAT .
VIN and Wall Adapter Bypass Capacitor
Many types of capacitors can be used for input bypassing.
However, caution must be exercised when using multilayer
ceramic capacitors. Because of the self resonant and high
Q characteristics of some types of ceramic capacitors, 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.
4055fb
18
LTC4055/LTC4055-1
OPERATION
Selecting WALL Input Resistors
The WALL input pin identifies the presence of a wall adapter.
This information is used to disconnect the inputs IN1/IN2
from the OUT pin in order to prevent back conduction 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.
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 voltage on BAT and the voltage on IN1/IN2 or OUT is greater
than the VUVLO (3.8V typ) threshold.
The wall adapter detection threshold is set by the following equation:
⎛ R1 ⎞
VTH( Adapter ) = VWALL • ⎜1+ ⎟
⎝ R2 ⎠
⎛ R1 ⎞
VHYST ( Adapter ) = VWALL −HYST • ⎜1+ ⎟
⎝ R2 ⎠
where VTH(Adapter) is the wall adapter detection threshold,
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.
Consider an example where the VTH(Adapter) is to be set
somewhere around 4.5V. Resistance on the WALL pin
should be kept relatively low (~10k) in order to prevent false
tripping of the wall comparator due to leakages associated
with the switching element used to connect the adapter
to OUT. Pick R2 to be 10k and solve for R1.
⎛ V ( Adapter ) ⎞
R1= R2 • ⎜⎜ TH
− 1⎟⎟
⎝ VWALL
⎠
⎛ 4.5 ⎞
– 1⎟ = 10k • 3.5 = 35k
R1= 10k • ⎜
⎝ 1
⎠
The nearest 1% resistor is 34.8k. Therefore R1 = 34.8k
and the rising trip point should be 4.48V.
⎛ 34.8 ⎞
VHYST ( Adapter ) ≈ 30mV • ⎜1+
⎟ ≈ 134mV
10 ⎠
⎝
The hysteresis is going to be approximately 134mV for
this example.
Power Dissipation
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 VOUT , the LTC4055/LTC4055-1 power
dissipation is approximately:
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 worstcase 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:
TA = 105°C – PD • θJA
TA = 105°C – (VOUT – VBAT) • IBAT • θJA
Example: An LTC4055/LTC4055-1 operating from a wall
adapter with 5V at VOUT 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:
TA = 105°C – (5V – 3V) • 0.8A • 37°C/W
TA = 105°C – 1.6W • 37°C/W = 105°C – 59°C = 46°C
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 approximated by:
IBAT =
105°C – TA
( VOUT – VBAT ) • θJA
Consider the above example with an ambient temperature
of 55°C. The charge current will be reduced to approximately:
105°C – 55°C
50°C
= 0.6675A
=
IBAT =
(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
soldered to the board. Correctly soldered to a 2500mm2
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
temperature. Without a backside thermal connection, this
number could drop to less than 500mA.
STABILITY
The constant-voltage mode feedback loop is stable without
any compensation when a battery is connected. However,
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.
Ideal Diode from BAT to OUT
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
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.
CONSTANT
ION
LTC4055
IMAX
CONSTANT
RON
CURRENT (A)
SLOPE: 1/RDIO,ON
IFWD
SLOPE: 1/RFWD
0
VFWD
SCHOTTKY
DIODE
CONSTANT
VON
4055 F04
FORWARD VOLTAGE (V)
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 VBUS to exceed the
500mA/100mA limits.
Figure 5 shows an LTC4055/LTC4055-1 configured for
USB applications with the optional wall adapter input. The
programming 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 60.4k
sets up a nominal charge current of approximately 800mA.
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)
FROM USB
CABLE VBUS
R3
1Ω
10μF
IN1
OUT
IN2
BAT
TO LDOs,
REGs, ETC
+
CHRG
R1
34.8k
R2
10k
ACPR
RNTCBIAS
100k
LTC4055
SUSP
SUSPEND USB POWER
WALL
HPWR
500mA/100mA SELECT
VNTC
SHDN
SHUTDOWN
NTC
TIMER PROG
NTC C
TIMER
100k 0.1μF
10μF
Li-Ion
CELL
CLPROG
RPROG
60.4k
GND
RCLPROG
105k
4055 F05
Figure 5. USB Power Control Application with Wall Adapter Input
4055fb
21
LTC4055/LTC4055-1
TYPICAL APPLICATIONS
Forcing the SUSP input pin above 1.2V does this. Figure 6
shows the 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.
USB Hosting Application: The LTC4055/LTC4055-1’s
IN1 and IN2 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/LTC4055-1 can be
configured to turn off its input power path, IN1 and IN2.
5V (NOM)
FROM USB
CABLE VBUS
DC/DC
VOUT CONVERTER VIN
EN
1μF
5V WALL
ADAPTER INPUT
R1
34.8k
IN1
OUT
IN2
BAT
USB
CONTROLLER
SUSP
ACPR
VNTC
HPWR
500mA/100mA SELECT
NTC
SHDN
GND
SHUTDOWN
TIMER PROG
NTC C
TIMER
100k 0.1μF
Li-Ion
CELL
CHRG
LTC4055
R3
100k
10μF
+
WALL
R2
10k
TO LDOs,
REGs, ETC
CLPROG
RPROG
100k
RCLPROG
105k
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
2.15 ± 0.05
2.90 ± 0.05 (4 SIDES)
PACKAGE OUTLINE
0.30 ±0.05
0.65 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
BOTTOM VIEW—EXPOSED PAD
4.00 ± 0.10
(4 SIDES)
R = 0.115
TYP
0.75 ± 0.05
15
PIN 1 NOTCH R = 0.20 TYP
OR 0.35 × 45° CHAMFER
16
0.55 ± 0.20
PIN 1
TOP MARK
(NOTE 6)
1
2.15 ± 0.10
(4-SIDES)
2
(UF16) QFN 1004
0.200 REF
0.00 – 0.05
0.30 ± 0.05
0.65 BSC
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 representation 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
ADAPTER
4.5V TO 5.5V
USB
4.35V TO 5.5V
1
C5
1μF
2
R10
35.8k
3
VIN
5
VOUT
C3
10μF
GND
CTL
SYSTEM LOAD
OUTPUT
4
STAT
+Li-Ion
C1
10μF
5
R9
10k
6
7
8
17
4
3
2
1
IN1
OUT
BAT
IN2
WALL
NTC
SHDN
VNTC
LTC4055
SUSP
CHRG
HPWR
ACPR
16
15 R5 10k
USB CURRENT 100mA-500mA
ADAPTER CURRENT 700mA
NTC
14
13
EXPOSED PAD
CLPROG GND PROG TIMER
9
R2
105k
10
11
R3
68.1k
12
C2
0.1μF
4055 TA03
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
Battery Chargers
LTC4075HVX
Dual Input USB/AC Adapter Li-Ion Battery Charger with
Overvoltage Protection
Both USB and AC Adapter Inputs Protected up to 22V, Standalone
Operation, 3mm × 3mm DFN
LTC4095
950mA USB Linear Lithium-Ion Battery Charger
2mm × 2mm DFN Package, thermal Regulation, Standalone Operation
LTC4097
USB/Wall Adapter Standalone Li-Ion/Polymer Battery Charger Dual Input, Thermal Regulation, 3mm × 2mm DFN
LTC4413
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/
LTC4085-1
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 VOUT , No
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
24 Linear Technology Corporation
LT 1108 REV B • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
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© LINEAR TECHNOLOGY CORPORATION 2004