LTC1732-4/LTC1732-4.2
Lithium-Ion Linear
Battery Charger Controller
FEATURES
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DESCRIPTIO
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Complete Linear Charger Controller for 1-Cell
Lithium-Ion Batteries
Preset Charge Voltage with 1% Accuracy
Programmable Charge Current
C/10 Charge Current Detection Output
Programmable Charge Termination Timer
Small, Thin 10-Pin MSOP Package
Select Pin Charges 4.1V or 4.2V Cells (LTC1732-4)
Input Supply (Wall Adapter) Detection Output
4.5V to 12V Input Voltage Range
Automatic Sleep Mode When Input Supply
is Removed (Only 7µA Battery Drain)
Automatic Trickle Charge of Low Voltage Cells
Programmable for Constant-Current-Only Mode
Battery Insertion Detect
4.05V Recharge Threshold for 4.2V Cells
(LTC1732-4.2)
3.8V Recharge Threshold for 4.1V or 4.2V Cells
(LTC1732-4)
The LTC
®
1732 is a complete constant-current/constant-
voltage linear charger controller for lithium-ion
(Li-Ion) batteries. Nickel-cadmium (NiCd) and nickel metal-
hydride (NiMH) batteries can also be charged with con-
stant current using external termination. Charge current
can be programmed with 7% (max) accuracy using exter-
nal sense and program resistors. An internal resistor
divider and precision reference set the final float voltage
with 1% accuracy. The SEL pin allows users to charge
either 4.1V or 4.2V cells.
When the input supply is removed, the LTC1732 automati-
cally enters a low current sleep mode, dropping the battery
drain current to 7µA. An internal comparator detects the
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 2.457V.
The LTC1732 begins a new charge cycle when a discharged
battery is connected to the charger or when the input power
is applied. In addition, if the battery remains connected to
the charger and the cell voltage drops below 3.8V for the
LTC1732-4 or below 4.05V for the LTC1732-4.2, a new
charge cycle will automatically begin.
The LTC1732 is available in the 10-pin MSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
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Cellular Phones
Handheld Computers
Charging Docks and Cradles
TYPICAL APPLICATIO
Single Cell 4.2V Li-Ion Battery Charger
V
IN
= 6V
MBRM120T3
R2
1k
R1
1k
3
8
V
CC
2
SEL
SENSE
CHRG
DRV
9
7
R
SENSE
0.2Ω
Q1
Si9430DY
I
BAT
= 500mA
1µF
LTC1732-4
10
4
C
TIMER
0.1µF
ACPR
TIMER
BAT
PROG
1
6
R
PROG
*
19.6k
GND
5
10µF
+
4.2V
Li-Ion
CELL
1732 TA01
*SHUTDOWN INVOKED BY FLOATING THE PROG PIN
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LTC1732-4/LTC1732-4.2
ABSOLUTE
MAXIMUM
RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
TOP VIEW
BAT
SEL
CHRG
TIMER
GND
1
2
3
4
5
10
9
8
7
6
ACPR
SENSE
V
CC
DRV
PROG
Input Supply Voltage (V
CC
) ................................... 13.2V
SENSE, DRV, BAT, SEL, TIMER, PROG,
CHRG, ACPR ......................................... – 0.3V to 13.2V
Operating Temperature Range (Note 2) .... – 40° to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
LTC1732EMS-4
LTC1732EMS-4.2
MS10 PART MARKING
LTNJ
LTUA
MS10 PACKAGE
10-LEAD PLASTIC MSOP
T
JMAX
= 140°C,
θ
JA
= 180°C/W
Consult factory 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)
LTC1732-4; 5V
≤
V
CC
≤
12V, V
SEL
= GND
LTC1732-4/LTC1732-4.2; 5V
≤
V
CC
≤
12V, V
SEL
= V
CC
R
PROG
= 19.6k, R
SENSE
= 0.2Ω
R
PROG
= 19.6k, R
SENSE
= 0.2Ω
R
PROG
= 97.6k, R
SENSE
= 0.2Ω
I
TRIKL
V
TRIKL
V
UV
∆V
UV
V
MSD
V
ASD
V
DIS
I
PROG
V
PROG
V
ACPR
I
CHRG
V
CHRG
V
SEL
Trickle Charge Current
Trickle Charge Threshold Voltage
V
CC
Undervoltage Lockout Voltage
V
CC
Undervoltage Lockout Hysteresis
Manual Shutdown Threshold Voltage
Automatic Shutdown Threshold Voltage
Voltage Mode Disable Threshold Voltage
PROG Pin Current
PROG Pin Voltage
ACPR Pin Output Low Voltage
CHRG Pin Weak Pull-Down Current
CHRG Pin Output Low Voltage
SEL Pin Threshold
PROG Pin Low to High
PROG Pin High to Low
(V
CC
– V
BAT
) High to Low
(V
CC
– V
BAT
) Low to High
V
DIS
= V
CC
– V
TIMER
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
ELECTRICAL CHARACTERISTICS
CONDITIONS
q
q
q
q
q
q
MIN
4.5
TYP
1
1
7
MAX
12
3
3
20
4.141
4.242
535
585
140
110
2.55
4.5
UNITS
V
mA
mA
µA
V
V
mA
mA
mA
mA
V
V
mV
V
V
V
BAT
I
BAT
Regulated Output Voltage
Current Mode Charge Current
4.059
4.158
465
415
60
30
2.35
4.1
4.2
500
100
50
2.457
4.1
200
2.457
2.446
V
BAT
= 2V, R
PROG
= 19.6k, I
TRIKL
= (V
CC
– V
SENSE
)/0.2Ω
q
From Low to High
From Low to High
q
q
30
40
54
69
2.5
90
100
0.4
q
300
2.457
0.7
15
0.3
35
0.6
1.2
55
1.2
2
2
U
W
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W
mV
mV
V
µA
µA
V
V
µA
V
V
LTC1732-4/LTC1732-4.2
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
End of Charge Indication Current Level
TIMER Accuracy
Recharge Battery Voltage Threshold per Cell
CONDITIONS
R
PROG
= 19.6k, R
SENSE
= 0.2Ω
C
TIMER
= 0.1µF
V
BAT
from High to Low (LTC1732-4)
V
BAT
from High to Low (LTC1732-4.2)
3.72
3.95
q
ELECTRICAL CHARACTERISTICS
MIN
25
TYP
50
10
3.80
4.05
MAX
100
UNITS
mA
%
V
V
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
The LTC1732E 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
Trickle Charge Current vs V
CC
60
R
PROG
=19.6kΩ
R
SEN
= 0.2Ω
V
BAT
= 2V
T
A
= 25°C
2.470
55
T
TIMER
(%)
I
TRKL
(mA)
V
PROG
(V)
50
45
40
4
6
8
V
CC
(V)
1732 G01
Trickle Charge Threshold Voltage
vs Temperature
2.470
V
CC
= 6V
2.465
105
110
T
TIMER
(%)
2.460
100
I
TRKL
(mA)
V
TRKL
(V)
2.455
2.250
–50
–25
25
50
75
0
TEMPERATURE (°C)
U W
10
100
1732 G04
Program Voltage vs Temperature
V
CC
= 6V
R
PROG
= 19.6kΩ
110
Timer Accuracy vs Temperature
V
CC
= 6V
C
TIMER
= 0.1µF
2.465
105
2.460
100
2.455
95
12
2.450
–50
–25
25
50
75
0
TEMPERATURE (°C)
100
125
90
–50
–25
25
50
75
0
TEMPERATURE (°C)
100
125
1732 G02
1732 G03
Timer Accuracy vs V
CC
C
TIMER
= 0.1µF
V
BAT
= 3V
T
A
= 25°C
Trickle Charge Current vs
Temperature
60
R
PROG
=19.6kΩ
R
SEN
= 0.2Ω
V
BAT
= 2V
V
CC
= 6V
55
50
95
45
90
125
4
6
8
V
CC
(V)
1732 G05
10
12
40
–50
–25
25
50
75
0
TEMPERATURE (°C)
100
125
1732 G06
3
LTC1732-4/LTC1732-4.2
TYPICAL PERFOR A CE CHARACTERISTICS
Battery Charge Current vs
Temperature
540
R
PROG
=19.6kΩ
R
SEN
= 0.2Ω
530
V
BAT
= 3V
V = 6V
520
CC
2.480
2.475
2.470
V
PROG
(V)
V
TRKL
(V)
I
BAT
(mA)
510
500
490
480
470
460
–50
–25
25
50
75
0
TEMPERATURE (°C)
100
125
Battery Charge Current vs V
CC
520
R
PROG
=19.6kΩ
R
SEN
= 0.2Ω
515
V
BAT
= 3V
T = 25°C
510
A
I
BAT
(mA)
505
500
495
490
485
480
4
6
8
V
CC
(V)
1732 G10
V
RECHRG
(V)
4
U W
1732 G07
Trickle Charge Threshold Voltage
vs V
CC
R
PROG
=19.6kΩ
T
A
= 25°C
2.480
Program Pin Voltage vs V
CC
R
PROG
=19.6kΩ
T
A
= 25°C
2.475
V
BAT
= 3V
2.470
2.465
2.460
2.455
2.450
2.445
2.440
2.465
2.460
2.455
2.450
2.445
2.440
4
6
8
V
CC
(V)
1732 G08
10
12
4
6
8
V
CC
(V)
10
12
1732 G09
Recharge Threshold Voltage vs
Temperature
4.1
V
CC
= 6V
LTC1732-4.2
4.0
3.9
3.8
LTC1732-4
10
12
3.7
–50
–25
25
50
75
0
TEMPERATURE (°C)
100
125
1732 G11
LTC1732-4/LTC1732-4.2
PIN FUNCTIONS
BAT (Pin 1):
Battery Sense Input. A bypass capacitor of
10µF or more is required to keep the loop stable when the
battery is not connected. A precision internal resistor
divider on this pin sets the final float potential. The resistor
divider is disconnected in sleep mode to reduce the
current drain on the battery.
SEL (Pin 2):
4.1V/4.2V Battery Selection Input Pin. Ground-
ing this pin will set the output float voltage to 4.1V per cell,
while connecting to V
CC
will set the voltage to 4.2V per cell.
For the LTC1732-4.2, the SEL pin must be connected to
V
CC
.
CHRG (Pin 3):
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 charge current
drops to 10% of the full-scale current for more than 15ms,
the N-channel MOSFET turns off and a 35µA current
source is connected from the CHRG pin to GND. When the
timer runs out or the input supply is removed, the current
source will be disconnected and the CHRG pin is forced
into a high impedance state.
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
(hours) = (C
TIMER
• 3 hours)/(0.1µF). When the TIMER pin
is connected to V
CC
, the timer is disabled, the constant-
voltage mode is disabled and the chip will operate in
constant-current mode only. 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 2.5µA current source to pull the pin above the
2.457V shutdown threshold voltage.
DRV (Pin 7):
Drive Output Pin for the P-Channel MOSFET
or PNP Transistor. If a PNP pass transistor is used, select
a high beta transistor to minimize the charge current error
due to the base current.
V
CC
(Pin 8):
Positive Input Supply Voltage. When V
BAT
is
within 54mV of V
CC
, the LTC1732 is forced into sleep
mode, dropping I
CC
to 7µA. V
CC
ranges from 4.5V to 12V.
Bypass this pin with a 1µF capacitor.
SENSE (Pin 9):
Current Sense Input. A sense resistor,
R
SENSE
, must be connected from V
CC
to the SENSE pin.
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 adapter) greater than the undervoltage
lockout threshold is applied to the LTC1732, this pin is
pulled to ground by an internal N-channel MOSFET that is
capable of sinking 5mA to drive an external LED.
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