LTC4050
Lithium-Ion Linear Battery
Charger with Thermistor Interface
FEATURES
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DESCRIPTIO
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Complete Standalone Linear Charger Controller
for 1-Cell Lithium-Ion Batteries
Thermistor Interface for Battery Temperature
Sensing
Preset Charge Voltage with
±1%
Accuracy
Programmable Charge Current
C/10 Charge Current Detection Output
Programmable Charge Termination Timer
Input Supply (Wall Adapter) Detection Output
4.5V to 10V Input Voltage Range
Automatic Sleep Mode When Input Supply
is Removed (Only 5µA Battery Drain)
Automatic Trickle Charging of Low Voltage Cells
Automatic Battery Recharge
Battery Insertion Detection
Space Saving 10-Pin MSOP Package
The LTC
®
4050-4.1/LTC4050-4.2 are complete standalone
constant-current/constant-voltage linear charge control-
lers for lithium-ion (Li-Ion) batteries. Charge current is
programmable and final float voltage has
±1%
accuracy.
When the input supply is removed, the LTC4050 automati-
cally enters a low quiescent current sleep mode, dropping
the battery drain current to 5µA. An internal comparator
detects the near-end-of-charge (C/10) condition while a
programmable timer, using an external capacitor, sets the
total charge time. Fully discharged cells are automatically
trickle charged at 10% of the programmed current until
cell voltage exceeds 2.49V. The thermistor interface
suspends charging if the cell temperature is outside of a
0°C to 50°C temperature window.
The LTC4050 begins a new charge cycle when a discharged
battery is connected to the charger or when the input power
is applied. In addition, a new charge cycle is automatically
started if the battery remains connected to the charger and
the cell voltage drops below 3.88V for 4.1V cells or below
3.98V for 4.2V cells.
The LTC4050 is available in the 10-pin MSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s
s
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Cellular Phones
Handheld Computers
Charging Docks and Cradles
TYPICAL APPLICATIO
Single Cell 4.2V 500mA Li-Ion Battery Charger
V
IN
6V
MBRM120T3
8
1k
1k
3
CHRG
V
CC
SENSE
DRV
0.2Ω
9
7
Si9430DY
I
BAT
= 500mA
*
19.6k
10µF
1µF
600
V
BAT
= 3.7V
500
CHARGE CURRENT (mA)
400
300
200
100
LTC4050-4.2
10
4
0.1µF
ACPR
TIMER
GND
5
BAT
PROG
NTC
2
1
6
+
4.2V
Li-Ion
CELL
10k NTC
T DALE NTHS-1206N02
*SHUTDOWN INVOKED BY FLOATING THE PROG PIN
4050 TA01
U
Charge Current vs
Thermistor Temperature
0
50
100
–50 –25
25
75
0
THERMISTOR TEMPERATURE (°C)
125
4050 TA05
U
U
4050f
1
LTC4050
ABSOLUTE
MAXIMUM
RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
ORDER PART
NUMBER
TOP VIEW
BAT
NTC
CHRG
TIMER
GND
1
2
3
4
5
10
9
8
7
6
ACPR
SENSE
V
CC
DRV
PROG
Input Supply Voltage (V
CC
) ...................................... 12V
SENSE, DRV, BAT, SEL,
TIMER, PROG, CHRG, ACPR .................– 0.3V to 12V
Operating Temperature Range (Note 2) . – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
LTC4050EMS-4.1
LTC4050EMS-4.2
MS PART MARKING
LTTW
LTTX
MS PACKAGE
10-LEAD PLASTIC MSOP
T
JMAX
= 140°C,
θ
JA
= 180°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 6V unless otherwise noted.
SYMBOL
V
CC
I
CC
PARAMETER
Input Supply Voltage
Input Supply Current
Charger On, Current Mode
Shutdown Mode
Sleep Mode (Battery Drain Current)
LTC4050-4.1; 5V
≤
V
CC
≤
10V, 0°C
≤
T
A
≤
85°C
LTC4050-4.2; 5V
≤
V
CC
≤
10V, 0°C
≤
T
A
≤
85°C
LTC4050-4.1; 5V
≤
V
CC
≤
10V
LTC4050-4.2; 5V
≤
V
CC
≤
10V
R
PROG
= 19.6k, R
SENSE
= 0.2Ω
R
PROG
= 19.6k, R
SENSE
= 0.2Ω
R
PROG
= 97.6k, R
SENSE
= 0.2Ω
CONDITIONS
q
q
q
ELECTRICAL CHARACTERISTICS
MIN
4.5
TYP
1.3
1.3
5
MAX
10
3
3
15
4.141
4.242
4.141
4.242
535
585
140
90
2.58
4.5
UNITS
V
mA
mA
µA
V
V
V
V
mA
mA
mA
mA
V
V
mV
V
V
BAT
Regulated Output (Float) Voltage in
Constant Voltage Mode
q
q
q
4.059
4.158
4.039
4.137
440
415
60
20
2.41
4.1
4.2
4.1
4.2
500
100
55
2.49
4
130
3.6
I
BAT
Current Mode Charge Current
I
TRIKL
V
TRIKL
V
UV
∆V
UV
V
MSD
V
ASD
I
PROG
V
PROG
V
ACPR
I
CHRG
V
CHRG
R
HOT
R
COLD
Trickle Charge Current
Trickle Charge Threshold Voltage
V
CC
Undervoltage Lockout Voltage
V
CC
Undervoltage Lockout Hysteresis
PROG Pin Manual Shutdown
Threshold Voltage
Automatic Shutdown Threshold Voltage
PROG Pin Current
PROG Pin Voltage
ACPR Pin Output Low Voltage
CHRG Pin Weak Pull-Down Current
CHRG Pin Output Low Voltage
Thermistor Resistance for Hot Fault
Thermistor Resistance for Cold Fault
V
BAT
= 2V, R
PROG
= 19.6k, I
TRIKL
= (V
CC
– V
SENSE
)/0.2Ω
q
q
q
(V
CC
– V
BAT
) High to Low
(V
CC
– V
BAT
) Low to High
Internal Pull-Up Current, No R
PROG
PROG Pin Source Current,
∆V
PROG
≤
5mV
R
PROG
=19.6k
I
ACPR
= 5mA
V
CHRG
= 1V
I
CHRG
= 5mA
q
25
40
300
54
69
2.3
2.47
0.525
32
0.525
85
100
3.7
25
4.1
28.5
4.4
31
2
U
W
U
U
W W
W
mV
mV
µA
µA
V
V
µA
V
kΩ
kΩ
4050f
LTC4050
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 6V unless otherwise noted.
SYMBOL
I
C/10
t
TIMER
V
RECHRG
PARAMETER
10% Charge Current Indication Level
TIMER Accuracy
Recharge Threshold Voltage
CONDITIONS
R
PROG
= 19.6k, R
SENSE
= 0.2Ω
C
TIMER
= 0.1µF
V
BAT
from High to Low (LTC4050-4.1)
V
BAT
from High to Low (LTC4050-4.2)
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
3.83
3.93
q
ELECTRICAL CHARACTERISTICS
MIN
25
TYP
50
10
3.88
3.98
MAX
100
UNITS
mA
%
V
V
Note 2:
The LTC4050E 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.
TYPICAL PERFOR A CE CHARACTERISTICS
Charge Current vs Temperature
540
R
PROG
= 19.6k
R
SEN
= 0.2Ω
V
BAT
= 3V
520
V
CC
= 6V
I
BAT
(mA)
I
BAT
(mA)
520
I
TRKL
(mA)
500
480
460
–50
–25
75
0
25
50
TEMPERATURE (°C)
Trickle Charge Current vs V
CC
70
R
PROG
= 19.6k
R
SEN
= 0.2Ω
65
V
BAT
= 2V
T
A
= 25°C
60
I
TRKL
(mA)
55
50
45
40
4
6
V
CC
(V)
LTC4050 G04
V
TRKL
(V)
V
TRKL
(V)
8
U W
100
LTC4050 G01
Charge Current vs V
CC
70
R
PROG
= 19.6k
515
R
SEN
= 0.2Ω
V
BAT
= 3V
510
T
A
= 25°C
505
500
495
490
485
480
125
4
6
V
CC
(V)
LC4050 G02
Trickle Charge Current
vs Temperature
R
PROG
= 19.6k
R
SEN
= 0.2Ω
65
V
BAT
= 2V
V
CC
= 6V
60
55
50
45
40
–50 –25
8
10
50
25
75
0
TEMPERATURE (°C)
100
125
LTC4050 G03
Trickle Charge Threshold Voltage
vs Temperature
2.51
V
CC
= 6V
R
PROG
= 19.6k
Trickle Charge Threshold Voltage
vs V
CC
2.55
R
PROG
= 19.6k
T
A
= 25°C
2.54
2.50
2.53
2.52
2.49
2.51
2.50
2.49
2.48
2.48
2.47
2.47
2.46
10
2.46
–50 –25
50
25
0
75
TEMPERATURE (°C)
100
125
2.45
4
6
V
CC
(V)
8
10
LTC4050 G06
LTC4050 G05
3
LTC4050
TYPICAL PERFOR A CE CHARACTERISTICS
Recharge Threshold Voltage
vs Temperature
4.1
V
CC
= 6V
LTC4050-4.2
2.470
V
RECHRG
(V)
V
PROG
(V)
3.9
LTC4050-4.1
2.465
2.460
3.8
2.455
3.7
–50
2.450
–50 –25
2.46
V
PROG
(V)
2.48
2.480
2.475
4.0
–25
75
0
25
50
TEMPERATURE (°C)
Timer Accuracy vs Temperature
110
V
CC
= 6V
V
BAT
= 3V
C
TIMER
= 0.1µF
110
105
TIMER (%)
TIMER (%)
100
R
HOT
(kΩ)
95
90
–50
–25
75
0
25
50
TEMPERATURE (°C)
NTC R
COLD
Threshold Voltage
vs Temperature
29.0
28.9
28.8
28.7
R
COLD
(kΩ)
V
CC
= 6V
28.6
28.5
28.4
28.3
28.2
28.1
–50
4.100
R
COLD
(kΩ)
R
HOT
(kΩ)
–25
0
25
50
75
TEMPERATURE (°C)
4
U W
100
LTC4050 G07
PROG Pin Voltage vs Temperature
V
CC
= 6V
R
PROG
= 19.6k
2.50
PROG Pin Voltage vs V
CC
R
PROG
= 19.6k
T
A
= 25°C
2.49
2.47
125
50
25
75
0
TEMPERATURE (°C)
100
125
2.45
4
6
V
CC
(V)
8
10
LTC4050 G09
LTC4050 G08
Timer Accuracy vs V
CC
V
BAT
= 3V
C
TIMER
= 0.1µF
T
A
= 25°C
4.16
4.14
4.12
100
4.10
4.08
95
4.06
90
4
5
6
7
V
CC
(V)
8
9
10
NTC R
HOT
Threshold Voltage
vs Temperature
V
CC
= 6V
105
100
125
4.04
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
LTC4050 G10
LTC4050 G11
LTC4050 G12
NTC R
HOT
Threshold Voltage
vs V
CC
4.150
T
A
= 25°C
28.60
NTC R
COLD
Threshold Voltage
vs V
CC
T
A
= 25°C
4.125
28.55
28.50
4.075
28.45
4.050
100
125
4
6
V
CC
(V)
8
10
LT4050 G14
28.40
4
6
V
CC
(V)
8
10
LTC4050 G15
LTC4050 G13
LTC4050
PIN FUNCTIONS
BAT (Pin 1):
Battery Sense Input. A precision internal
resistor divider on this pin sets the final float voltage. The
resistor divider is disconnected in sleep mode to reduce
the current drain on the battery. A bypass capacitor of
10µF or more is required to keep the loop stable when the
battery is not connected.
NTC (Pin 2):
Thermistor Interface Input. A 10kΩ Dale
Curve 2 NTC thermistor (or other 10kΩ NTC thermistor
with a room temperature beta of around 3400) is con-
nected from this pin to ground. The charge cycle will be
disabled and the timer will be placed on hold if the
thermistor temperature is above 50°C or below 0°C.
CHRG (Pin 3):
Charge Status Open-Drain Output. When
the battery is charging, the CHRG pin is pulled low by an
internal N-channel MOSFET. When the charge current
drops to 10% of the full-scale current for more than 15ms,
the N-channel MOSFET turns off and a 32µA current
source is connected from the CHRG pin to GND. When the
timer runs out or the input supply is removed, the current
source is disconnected and the CHRG pin becomes high
impedance.
TIMER (Pin 4):
Timer Capacitor and Constant-Voltage
Mode Disable Input Pin. The timer period is set by placing
a capacitor, C
TIMER
, to GND. The timer period is t
TIMER
=
(C
TIMER
• 3 hours)/(0.1µF). Shorting the TIMER pin to
GND will disable the internal timer function and the C/10
function.
GND (Pin 5):
Ground.
PROG (Pin 6):
Charge Current Program and Shutdown
Input Pin. The charge current is programmed by connect-
ing a resistor, R
PROG
to ground. The charge current is I
BAT
= (V
PROG
• 800Ω)/(R
PROG
• R
SENSE
). The IC can be forced
into shutdown by floating the PROG pin and allowing the
internal 2.3µA current source to pull the pin above the 3.6V
shutdown threshold voltage.
DRV (Pin 7):
Drive Output Pin for the P-Channel MOSFET
or PNP Transistor. The impedance is high at this pin,
therefore, if a PNP pass transistor is used, it must have
high gain.
V
CC
(Pin 8):
Positive Input Supply Voltage. V
CC
can range
from 4.5V to 10V. Bypass this pin with a 1µF capacitor.
When V
BAT
is within 54mV of V
CC
, the LTC4050 is forced
into sleep mode, dropping I
CC
to 5µA.
SENSE (Pin 9):
Current Sense Input. A sense resistor,
R
SENSE
, must be connected from V
CC
to the SENSE pin.
Select a resistor value that will develop approximately
100mV at the programmed full-scale charge current.
This resistor is chosen using the following equation:
R
SENSE
= (V
PROG
• 800Ω)/(R
PROG
• I
BAT
)
ACPR (Pin 10):
Wall Adapter Present Output. When the
input voltage (wall adaptor) is applied to the LTC4050, this
pin is pulled to ground by an internal N-channel MOSFET
that is capable of sinking 5mA suitable for driving an
external LED.
U
U
U
4050f
5
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