FEATURES
Battery Charger:
n
Constant-Current/Constant-Voltage Operation
with Thermal Feedback to Maximize Charge Rate
without Risk of Overheating
n
Internal 4.5-Hour Safety Timer for Termination
n
Charge Current Programmable Up to 500mA with
5% Accuracy
n
NTC Thermistor Input for Temperature Qualified
Charging
n
C/10 Charge Current Detection Output
n
5µA Supply Current in Shutdown Mode
Switching Regulator:
n
High Efficiency Synchronous Buck Converter
n
300mA Output Current (Constant-Frequency Mode)
n
2.7V to 4.5V Input Range (Powered from BAT Pin)
n
0.8V to V
BAT
Output Range
n
MODE Pin Selects Fixed (2.25MHz) Constant-Frequency
PWM Mode or Low I
CC
(23µA) Burst Mode
®
Operation
n
2µA BAT Current in Shutdown Mode
n
10-Lead, Low Profile (0.75 mm) 3mm
×
3mm DFN Package
LTC4081
500mA Li-Ion Charger
with NTC Input and
300mA Synchronous Buck
DESCRIPTION
The
LTC
®
4081
is a complete constant-current/constant-
voltage linear battery charger for a single-cell 4.2V
lithium-ion/polymer battery with an integrated 300mA
synchronous buck converter. A 3mm × 3mm DFN pack-
age and low external component count make the LTC4081
especially suitable for portable applications. Furthermore,
the LTC4081 is specifically designed to work within USB
power specifications.
The
CHRG
pin indicates when charge current has dropped
to ten percent of its programmed value (C/10). An internal
4.5-hour timer terminates the charge cycle. The full-
featured LTC4081 battery charger also includes trickle
charge, automatic recharge, soft-start (to limit inrush
current) and an NTC thermistor input used to monitor
battery temperature.
The LTC4081 integrates a synchronous buck converter
that is powered from the BAT pin. It has an adjustable
output voltage and can deliver up to 300mA of load cur-
rent. The buck converter also features low current high
efficiency Burst Mode operation that can be selected by
the MODE pin.
The LTC4081 is available in a 10-lead, low profile (0.75mm)
3mm × 3mm DFN package.
L,
LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
and ThinSOT and PowerPath are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents, including
6522118.
APPLICATIONS
n
n
n
n
Wireless Headsets
Bluetooth Applications
Portable MP3 Players
Multifunction Wristwatches
TYPICAL APPLICATION
510Ω
V
CC
(3.75V
TO 5.5V)
100k
Li-Ion Battery Charger with 1.8V Buck Regulator
100
80
BAT
EN_BUCK
NTC LTC4081
SW
FB
1O H
10pF
1M
V
OUT
(1.8V/300mA)
806Ω
806k
4081 TA01a
Buck Efficiency vs Load Current
(V
OUT
= 1.8V)
1000
EFFICIENCY
(Burst)
EFFICIENCY
(PWM)
100
POWER LOSS (mW)
POWER
LOSS 10
(PWM)
1
4.7 F
+
4.2V
Li-Ion/
POLYMER
BATTERY
EFFICIENCY (%)
V
CC
CHRG
500mA
60
40
4.7 F
100k
T
EN_CHRG
MODE GND PROG
POWER LOSS
(Burst)
20
4.7 F
0
0.01
V
BAT
= 3.8V 0.1
V
OUT
= 1.8V
L = 10 H
C = 4.7 F
0.01
0.1
1
10
100
1000
LOAD CURRENT (mA)
4081 TA01b
4081fa
For more information
www.linear.com/LTC4081
1
LTC4081
ABSOLUTE MAXIMUM RATINGS
(Note 1)
V
CC
, t < 1ms and Duty Cycle < 1% ............... –0.3V to 7V
V
CC
Steady State .......................................... –0.3V to 6V
BAT,
CHRG
................................................... –0.3V to 6V
EN_CHRG, PROG, NTC ....................–0.3V to V
CC
+ 0.3V
MODE, EN_BUCK ........................... –0.3V to V
BAT
+ 0.3V
FB ................................................................ –0.3V to 2V
BAT Short-Circuit Duration ........................... Continuous
BAT Pin Current .................................................. 800mA
PROG Pin Current ....................................................2mA
Junction Temperature ............................................125°C
Operating Temperature Range (Note 2)....–40°C to 85°C
Storage Temperature Range .................. –65°C to 125°C
PIN CONFIGURATION
TOP VIEW
BAT
V
CC
EN_CHRG
PROG
NTC
1
2
3
4
5
11
10 SW
9 EN_BUCK
8 MODE
7 FB
6
CHRG
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
T
JMAX
= 110°C,
θ
JA
= 43°C/W (NOTE 3)
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC4081EDD#PBF
TAPE AND REEL
LTC4081EDD#TRPBF
PART MARKING*
LDBX
PACKAGE DESCRIPTION
10-Lead (3mm × 3mm) DFN
TEMPERATURE RANGE
0°C to 70°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
SYMBOL
V
CC
V
BAT
I
CC
I
CC_SD
I
BAT_SD
PARAMETER
Battery Charger Supply Voltage
Quiescent Supply Current (Charger On,
Switching Regulator Off)
Supply Current in Shutdown (Both Battery
Charger and Switching Regulator Off)
Battery Current in Shutdown (Both Battery
Charger and Switching Regulator Off)
The
l
denotes specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C, V
CC
= 5V, V
BAT
= 3.8V, V
EN_CHRG
= 0V, V
NTC
= 0V, V
EN_BUCK
= V
BAT
, V
MODE
= 0V. (Note 2)
CONDITIONS
(Note 4)
V
BAT
= 4.5V (Forces I
BAT
and I
PROG
= 0), V
EN_BUCK
= 0
V
EN_CHRG
= 5V, V
EN_BUCK
= 0, V
CC
> V
BAT
V
EN_CHRG
= 4V, V
EN_BUCK
= 0, V
CC
(3.5V) < V
BAT
(4V)
V
EN_CHRG
= 5V, V
EN_BUCK
= 0, V
CC
> V
BAT
V
EN_CHRG
= 4V, V
EN_BUCK
= 0, V
CC
(3.5V) < V
BAT
(4V)
l
l
l
l
l
MIN
3.75
2.7
TYP
5
3.8
110
5
2
0.6
2
MAX
5.5
4.5
300
10
5
UNITS
V
V
µA
µA
µA
µA
µA
4081fa
Input Voltage for the Switching Regulator (Note 5)
2
For more information
www.linear.com/LTC4081
LTC4081
ELECTRICAL CHARACTERISTICS
SYMBOL
V
FLOAT
I
BAT
PARAMETER
V
BAT
Regulated Output Voltage
Current Mode Charge Current
Battery Charger
I
BAT
= 2mA
I
BAT
= 2mA, 4.3V < V
CC
< 5.5V
R
PROG
= 4k; Current Mode; V
EN_BUCK
= 0
R
PROG
= 0.8k; Current Mode; V
EN_BUCK
= 0
V
CC
Rising
V
CC
Falling
0.8k ≤ R
PROG
≤ 4k
(V
CC
– V
BAT
), V
CC
Low to High
(V
CC
– V
BAT
), V
CC
High to Low
V
BAT
= 2V, R
PROG
= 0.8k
V
BAT
Rising
V
FLOAT
– V
BAT
, 0°C < T
A
< 85°C
I
BAT
= 0.9 I
CHG
I
BAT
= 0.1 I
CHG
l
l
l
l
l
l
l
l
l
The
l
denotes specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C, V
CC
= 5V, V
BAT
= 3.8V, V
EN_CHRG
= 0V, V
NTC
= 0V, V
EN_BUCK
= V
BAT
, V
MODE
= 0V. (Note 2)
CONDITIONS
MIN
4.179
4.158
90
475
3.5
2.8
0.98
60
15
35
2.75
100
70
180
90
3
1.5
0.75
0.085
TYP
4.2
4.2
100
500
3.6
3.0
1.0
82
32
180
50
2.9
150
100
300
130
4.5
2.25
1.125
0.1
115
I
BAT
= 350mA, V
CC
= 4V
V
BAT
= 2V
V
BAT
= 2V
V
NTC
= 2.5V
0.76 • V
CC
0.015 • V
CC
0.35 • V
CC
0.017 • V
CC
82
50
2
25
700
2
75
1
6
3
1.5
65
3.05
350
130
MAX
4.221
4.242
110
525
3.7
3.2
1.02
100
45
UNITS
V
V
mA
mA
V
V
V
mV
mV
µs
mA
V
mV
mV
mV
mV
hrs
hrs
hrs
°C
mW
Hz
%
µA
V
V
V
V
mV
mV
Hz
%
V
UVLO_CHRG
V
CC
Undervoltage Lockout Voltage
V
PROG
V
ASD
t
SS_CHRG
I
TRKL
V
TRKL
V
TRHYS
DV
RECHRG
DV
UVCL1,
DV
UVCL2
t
TIMER
PROG Pin Servo Voltage
Automatic Shutdown Threshold Voltage
Battery Charger Soft-Start Time
Trickle Charge Current
Trickle Charge Threshold Voltage
Trickle Charge Threshold Voltage Hysteresis
Recharge Battery Threshold Voltage
(V
CC
– V
BAT
) Undervoltage Current Limit
Threshold Voltage
Charge Termination Timer
Recharge Time
Low-Battery Charge Time
I
C/10
T
LIM
R
ON_CHRG
f
BADBAT
D
BADBAT
I
NTC
V
COLD
V
HOT
V
DIS
f
NTC
D
NTC
End of Charge Indication Current Level
Junction Temperature in Constant-
Temperature Mode
Power FET On-Resistance
(Between V
CC
and BAT)
Defective Battery Detection
CHRG
Pulse Frequency
Defective Battery Detection
CHRG
Pulse Frequency Duty Ratio
NTC Pin Current
V
BAT
= 2.5V
R
PROG
= 2k (Note 6)
l
l
0.115 mA/mA
Cold Temperature Fault Threshold Voltage Rising Voltage Threshold
Hysteresis
Hot Temperature Fault Threshold Voltage
NTC Disable Threshold Voltage
Fault Temperature
CHRG
Pulse Frequency
Fault Temperature
CHRG
Pulse Frequency
Duty Ratio
Falling Voltage Threshold
Hysteresis
Falling Threshold; V
CC
= 5V
Hysteresis
4081fa
For more information
www.linear.com/LTC4081
3
LTC4081
ELECTRICAL CHARACTERISTICS
SYMBOL
V
FB
I
FB
f
OSC
I
BAT_NL_CF
I
BAT_NL_BM
I
BAT_SLP
PARAMETER
FB Servo Voltage
FB Pin Input Current
Switching Frequency
No-Load Battery Current (Continuous
Frequency Mode)
No-Load Battery Current (Burst Mode
Operation)
Battery Current in SLEEP Mode
No-Load for Regulator, V
EN_CHRG
= 5V,
L = 10µH, C = 4.7µF
No-Load for Regulator, V
EN_CHRG
= 5V,
MODE = V
BAT
, L = 10µH, C = 4.7µF
V
EN_CHRG
= 5V, MODE = V
BAT
,
V
OUT
> Regulation Voltage
V
BAT
Rising
V
BAT
Falling
l
l
l
The
l
denotes specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C, V
CC
= 5V, V
BAT
= 3.8V, V
EN_CHRG
= 0V, V
NTC
= 0V, V
EN_BUCK
= V
BAT
, V
MODE
= 0V. (Note 2)
CONDITIONS
l
MIN
0.78
–50
l
TYP
0.80
2.25
1.9
23
MAX
0.82
50
2.75
UNITS
V
nA
MHz
mA
µA
Buck Converter
V
FB
= 0.85V
1.8
10
2.6
2.4
15
2.7
2.5
0.95
0.85
20
2.8
2.6
µA
V
V
W
W
V
UVLO_BUCK
Buck Undervoltage Lockout Voltage
R
ON_P
R
ON_N
I
LIM_P
I
LIM_N
I
ZERO_CF
I
PEAK
I
ZERO_BM
t
SS_BUCK
Logic
V
IH
V
IL
V
OL
I
IH
I
IL
R
EN_CHRG
I
CHRG
Input High Voltage
Input Low Voltage
Output Low Voltage (CHRG)
Input Current High
Input Current Low
EN_CHRG Pin Input Resistance
CHRG
Pin Leakage Current
PMOS Switch On-Resistance
NMOS Switch On-Resistance
PMOS Switch Current Limit
NMOS Switch Current Limit
NMOS Zero Current in Normal Mode
Peak Current in Burst Mode Operation
Zero Current in Burst Mode Operation
Buck Soft-Start Time
375
520
700
15
700
mA
mA
mA
MODE = V
BAT
MODE = V
BAT
From the Rising Edge of EN_BUCK to 90%
of Buck Regulated Output
EN_CHRG, EN_BUCK, MODE Pin Low to High
EN_CHRG, EN_BUCK, MODE Pin High to Low
I
SINK
= 5mA
EN_BUCK, MODE Pins at 5.5V, V
BAT
= 5V
EN_CHRG, EN_BUCK, MODE Pins at GND
V
EN_CHRG
= 5V
V
BAT
= 4.5V, V
EN_CHRG
= 5V
l
l
l
l
l
l
50
20
100
35
400
150
50
mA
mA
µs
1.2
0.4
60
–1
–1
1
1.45
105
1
1
3.3
1
V
V
mV
µA
µA
MW
µA
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:
The LTC4081 is 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 3:
Failure to solder the exposed backside of the package to the PC
board ground plane will result in a thermal resistance much higher than
43°C/W.
Note 4:
Although the LTC4081 charger functions properly at 3.75V, full
charge current requires an input voltage greater than the desired final
battery voltage per
DV
UVCL1
specification.
Note 5:
The 2.8V maximum buck undervoltage lockout (V
UVLO_BUCK
) exit
threshold must first be exceeded before the minimum V
BAT
specification
applies.
Note 6:
I
C/10
is expressed as a fraction of measured full charge current
with indicated PROG resistor.
4
4081fa
For more information
www.linear.com/LTC4081
LTC4081
TYPICAL PERFORMANCE CHARACTERISTICS
(T
A
= 25°C, V
CC
= 5V, V
BAT
= 3.8V, unless otherwise specified)
Battery Regulation (Float) Voltage
vs Charge Current
R
PROG
= 2k
4.21
4.20
FLOAT VOLTAGE (V)
FLOAT VOLTAGE (V)
4.210
4.205
4.200
Battery Regulation (Float) Voltage
vs Temperature
4.25
4.20
4.15
FLOAT VOLTAGE (V)
4.10
4.05
4.00
3.95
3.90
Battery Regulation (Float) Voltage
vs V
CC
Supply Voltage
4.19
4.18
4.17
4.16
4.15
4.14
4.13
0
50
200
150
100
CHARGE CURRENT (mA)
250
4081 G01
4.195
4.190
4.185
4.180
4.175
4.170
4.165
4.160
– 50 – 30
– 10
50
30
10
TEMPERATURE (°C)
70
90
4081 G02
3.85
4
4.5
5
5.5
V
CC
SUPPLY VOLTAGE (V)
6
4081 G03
250
Charge Current vs Temperature
with Thermal Regulation
(Constant-Current Mode)
V
CC
= 6V
V
BAT
= 3V
R
PROG
= 2k
1.0
PROG Pin Voltage
vs Charge Current
R
PROG
= 2k
0.9
Charger FET On-Resistance
vs Temperature
V
CC
= 4V
0.8 I
BAT
= 350mA
0.7
0.6
R
DS(ON)
(Ω)
0.5
0.4
0.3
CHARGE CURRENT (mA)
200
0.8
THERMAL CONTROL
LOOP IN OPERATION
V
PROG
(V)
150
0.6
100
0.4
0.2
50
0
–50
0.2
0.1
0
–25
0
25
50
75
100
125
4081 G04
0
25
TEMPERATURE (°C)
50 75 100 125 150 175 200
CHARGE CURRENT (mA)
4081 G05
0
– 50 – 30
–10
50
30
10
TEMPERATURE (°C)
70
90
4081 G06
EN_CHRG, EN_BUCK and
MODE Pin Threshold Voltage
vs Temperature
0.95
0.90
THRESHOLD VOLTAGE (V)
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
–50
–30
–10 10
30
50
TEMPERATURE (°C)
70
90
4081 G07
EN_CHRG Pin Pull-Down
Resistance vs Temperature
1.7
PULLDOWN RESISTANCE (MΩ)
1.6
1.5
1.4
1.3
1.2
1.1
1.0
–50
–30
–10 10
30
50
TEMPERATURE (°C)
70
90
4081 G08
RISING
FALLING
4081fa
For more information
www.linear.com/LTC4081
5
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