LTC1732-4.2 [Linear]
Lithium-Ion Linear Battery Charger Controller; 锂离子电池线性充电器，控制器
| 型号： | LTC1732-4.2 |
| 厂家： | 
Linear |
| 描述： | Lithium-Ion Linear Battery Charger Controller |
| 文件： | 总12页 (文件大小：171K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC1732-4/LTC1732-4.2
Lithium-Ion Linear
Battery Charger Controller
U
FEATURES
DESCRIPTIO
The LTC®1732 is a complete constant-current/constant-
voltage linear charger controller for lithium-ion
(Li-Ion)batteries.Nickel-cadmium(NiCd)andnickelmetal-
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.
■
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
Whentheinputsupplyisremoved,theLTC1732automati-
callyentersalowcurrentsleepmode,droppingthebattery
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.Fullydischargedcellsareautomaticallytricklecharged
at 10% of the programmed current until cell voltage
exceeds 2.457V.
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)
TheLTC1732beginsanewchargecyclewhenadischarged
batteryisconnectedtothechargerorwhentheinputpower
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.
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APPLICATIO S
■
Cellular Phones
■
Handheld Computers
Charging Docks and Cradles
■
The LTC1732 is available in the 10-pin MSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
U
TYPICAL APPLICATIO
Single Cell 4.2V Li-Ion Battery Charger
V
IN
= 6V
MBRM120T3
8
2
SEL
R2
1k
R
SENSE
V
1µF
CC
0.2Ω
9
7
R1
1k
SENSE
DRV
3
Q1
Si9430DY
CHRG
ACPR
LTC1732-4
I
= 500mA
BAT
10
4
1
6
BAT
TIMER PROG
C
TIMER
0.1µF
4.2V
Li-Ion
CELL
GND
5
+
R
*
PROG
19.6k
10µF
1732 TA01
*SHUTDOWN INVOKED BY FLOATING THE PROG PIN
1
LTC1732-4/LTC1732-4.2
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ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
(Note 1)
Input Supply Voltage (VCC) ................................... 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
TOP VIEW
BAT
SEL
CHRG
TIMER
GND
1
2
3
4
5
10 ACPR
LTC1732EMS-4
LTC1732EMS-4.2
9
8
7
6
SENSE
V
CC
DRV
PROG
MS10 PART MARKING
MS10 PACKAGE
10-LEAD PLASTIC MSOP
TJMAX = 140°C, θJA = 180°C/W
LTNJ
LTUA
Consult factory for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 6V unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
Input Supply Voltage
Input Supply Current
●
4.5
12
V
CC
I
Charger On, Current Mode
Shutdown Mode
Sleep Mode (Battery Drain Current)
●
●
1
1
7
3
3
20
mA
mA
µA
CC
V
Regulated Output Voltage
LTC1732-4; 5V ≤ V ≤ 12V, V = GND
●
●
4.059
4.158
4.1
4.2
4.141
4.242
V
V
BAT
CC
SEL
LTC1732-4/LTC1732-4.2; 5V ≤ V ≤ 12V, V
= V
CC
CC
SEL
I
Current Mode Charge Current
R
R
= 19.6k, R
= 19.6k, R
= 0.2Ω
= 0.2Ω
465
415
500
535
585
mA
mA
BAT
PROG
PROG
SENSE
SENSE
●
R
= 97.6k, R
= 0.2Ω
60
30
100
50
140
110
mA
mA
V
PROG
SENSE
I
Trickle Charge Current
V
= 2V, R
= 19.6k, I
= (V – V
)/0.2Ω
SENSE
●
●
●
TRIKL
BAT
PROG
TRIKL
CC
V
V
Trickle Charge Threshold Voltage
From Low to High
From Low to High
2.35
2.457 2.55
TRIKL
UV
V
V
Undervoltage Lockout Voltage
Undervoltage Lockout Hysteresis
4.1
4.5
V
CC
CC
∆V
200
mV
UV
V
V
V
Manual Shutdown Threshold Voltage
PROG Pin Low to High
PROG Pin High to Low
2.457
2.446
V
V
MSD
Automatic Shutdown Threshold Voltage
(V – V ) High to Low
30
40
54
69
90
100
mV
mV
ASD
CC
BAT
(V – V ) Low to High
CC
BAT
Voltage Mode Disable Threshold Voltage
PROG Pin Current
V
= V – V
TIMER
0.4
V
DIS
DIS
CC
I
Internal Pull-Up Current, No R
PROG Pin Source Current, ∆V
2.5
µA
µA
PROG
PROG
≤ 5mV
●
●
300
PROG
V
V
PROG Pin Voltage
R
=19.6k
PROG
2.457
0.7
V
V
PROG
ACPR
CHRG
ACPR Pin Output Low Voltage
CHRG Pin Weak Pull-Down Current
CHRG Pin Output Low Voltage
SEL Pin Threshold
I
= 5mA
1.2
55
1.2
2
ACPR
I
V
= 1V
15
35
µA
V
CHRG
CHRG
V
V
I
= 5mA
0.6
CHRG
SEL
0.3
V
2
LTC1732-4/LTC1732-4.2
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 6V unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
50
MAX
UNITS
mA
I
t
End of Charge Indication Current Level
TIMER Accuracy
R
PROG
= 19.6k, R = 0.2Ω
SENSE
●
25
100
C/10
C
= 0.1µF
10
%
TIMER
TIMER
VRECHRG
Recharge Battery Voltage Threshold per Cell
V
V
from High to Low (LTC1732-4)
from High to Low (LTC1732-4.2)
3.72
3.95
3.80
4.05
V
V
BAT
BAT
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.
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TYPICAL PERFOR A CE CHARACTERISTICS
Timer Accuracy vs Temperature
Trickle Charge Current vs VCC
Program Voltage vs Temperature
60
55
50
45
40
2.470
2.465
2.460
2.455
2.450
110
105
100
95
R
R
=19.6kΩ
V
C
= 6V
V
= 6V
PROG
PROG
SEN
BAT
CC
TIMER
CC
= 0.2Ω
= 0.1µF
R
= 19.6kΩ
V
= 2V
= 25°C
T
A
90
8
25
50
75
125
–50 –25
0
25
50
75 100 125
4
6
10
12
–50 –25
0
100
V
CC
(V)
TEMPERATURE (°C)
TEMPERATURE (°C)
1732 G01
1732 G02
1732 G03
Trickle Charge Current vs
Temperature
Trickle Charge Threshold Voltage
vs Temperature
Timer Accuracy vs VCC
110
105
100
95
60
55
50
45
40
2.470
2.465
2.460
2.455
2.250
R
R
V
=19.6kΩ
C
V
T
= 0.1µF
PROG
SEN
BAT
TIMER
BAT
A
V
CC
= 6V
= 0.2Ω
= 3V
= 2V
= 6V
= 25°C
V
CC
90
8
4
6
10
12
25
50
75
125
–50 –25
0
100
25
50
75
125
–50 –25
0
100
V
CC
(V)
TEMPERATURE (°C)
TEMPERATURE (°C)
1732 G05
1732 G06
1732 G04
3
LTC1732-4/LTC1732-4.2
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TYPICAL PERFOR A CE CHARACTERISTICS
Trickle Charge Threshold Voltage
vs VCC
Battery Charge Current vs
Temperature
Program Pin Voltage vs VCC
540
530
520
510
500
490
480
470
460
2.480
2.475
2.470
2.465
2.460
2.455
2.450
2.445
2.440
2.480
2.475
2.470
2.465
2.460
2.455
2.450
2.445
2.440
R
R
V
=19.6kΩ
R
T
=19.6kΩ
R
=19.6kΩ
PROG
PROG
SEN
BAT
PROG
A
= 0.2Ω
= 25°C
T
= 25°C
A
= 3V
= 6V
V
= 3V
BAT
V
CC
25
50
75
125
–50 –25
0
100
8
4
6
8
10
12
4
6
10
12
TEMPERATURE (°C)
V
CC
(V)
V
CC
(V)
1732 G07
1732 G08
1732 G09
Recharge Threshold Voltage vs
Temperature
Battery Charge Current vs VCC
4.1
4.0
3.9
3.8
3.7
520
515
510
505
500
495
490
485
480
R
R
=19.6kΩ
PROG
SEN
BAT
V
= 6V
CC
= 0.2Ω
LTC1732-4.2
V
= 3V
= 25°C
T
A
LTC1732-4
25
50
75
125
–50 –25
0
100
8
4
6
10
12
TEMPERATURE (°C)
V
CC
(V)
1732 G11
1732 G10
4
LTC1732-4/LTC1732-4.2
U
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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 onthispinsetsthefinalfloatpotential.Theresistor
divider is disconnected in sleep mode to reduce the
current drain on the battery.
GND (Pin 5): Ground.
PROG (Pin 6): Charge Current Program and Shutdown
Input Pin. The charge current is programmed by connect-
ing a resistor, RPROG to ground. The charge current is IBAT
= (VPROG • 800Ω)/(RPROG • RSENSE). 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.
SEL(Pin2):4.1V/4.2VBatterySelectionInputPin.Ground-
ing this pin will set the output float voltage to 4.1V per cell,
whileconnectingtoVCC willsetthevoltageto4.2Vpercell.
For the LTC1732-4.2, the SEL pin must be connected to
VCC.
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.
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
dropsto10%ofthefull-scalecurrentformorethan15ms,
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.
V
CC (Pin 8): Positive Input Supply Voltage. When VBAT is
within 54mV of VCC, the LTC1732 is forced into sleep
mode, dropping ICC to 7µA. VCC ranges from 4.5V to 12V.
Bypass this pin with a 1µF capacitor.
SENSE (Pin 9): Current Sense Input. A sense resistor,
RSENSE, must be connected from VCC to the SENSE pin.
This resistor is chosen using the following equation:
RSENSE = (VPROG • 800Ω)/(RPROG • IBAT
)
TIMER (Pin 4): Timer Capacitor and Constant-Voltage
Mode Disable Input Pin. The timer period is set by placing
a capacitor, CTIMER, to GND. The timer period is tTIMER
(hours)=(CTIMER •3hours)/(0.1µF).WhentheTIMERpin
is connected to VCC, 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.
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.
5
LTC1732-4/LTC1732-4.2
W
BLOCK DIAGRA
V
CC
8
3.8V (LTC1732-4)
4.05V (LTC1732-4.2)
+
–
UNDERVOLTAGE
LOCKOUT
C5
V
= 4.1V
UV
R
SENSE
SENSE
+
–
9
800Ω
C1
80Ω
+
–
54mV
CHRG
+
–
3
C4
–
+
C/10 STOP UVLO RECHRG C/10
720Ω
DRV
BAT
35µA
CA
7
1
ACPR
SHDN
LOGIC
–
+
SLP
C2
LBO
TIMER
ACPR
OSCILLATOR
COUNTER
4
SEL
2
V
REF
–
+
10
+
+
VA
V
CC
C3
A1
–
–
2.5µA
V
REF
2.457V
CHARGE
PROG
GND
6
5
1732 BD
BATTERY CURRENT I
= (2.457V • 800Ω)/(R
• R
)
SENSE
BAT
PROG
R
PROG
6
LTC1732-4/LTC1732-4.2
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OPERATIO
The LTC1732 is a linear battery charger controller. The
charge current is programmed by the combination of a
program resistor (RPROG) from the PROG pin to ground
and a sense resistor (RSENSE) between the VCC and SENSE
pins. RPROG sets a program current through an internal
trimmed 800Ω resistor setting up a voltage drop from VCC
to the input of the current amplifier (CA). The current
amplifierservosthegateoftheexternalP-channelMOSFET
to force the same voltage drop across RSENSE which sets
the charge current. When the potential at the BAT pin
approaches the preset float voltage, the voltage amplifier
(VA) will start sinking current which shrinks the voltage
drop across RSENSE, thus reducing the charge current.
drops to 10% of the full-scale charge current, an internal
comparatorwillturnoffthepull-downN-channelMOSFET
at the CHRG pin and connect a weak current source to
ground to indicate an end-of-charge (C/10) condition.
An external capacitor on the TIMER pin sets the total
charge time. After a time-out occurs, the charge cycle is
terminated and the CHRG pin is forced to a high imped-
ance state. To restart the charge cycle, simply remove the
inputvoltageandreapplyit, orfloatthePROGpinmomen-
tarily.
For batteries like lithium-ion that require accurate final
float potential, the internal 2.457V reference, voltage am-
plifierandtheresistordividerprovideregulationwith±1%
(max)accuracy.ForNiMHandNiCdbatteries,theLTC1732
can function as a current source by pulling the TIMER pin
to VCC. When in the constant-current only mode, the
voltage amplifier, timer, C/10 comparator and the trickle
charge function are all disabled.
Charging begins when the potential on the VCC pin rises
above the UVLO level and a program resistor is connected
from the PROG pin to ground. At the beginning of the
charge cycle, if the battery voltage is below 2.457V, the
charger goes into trickle charge mode. The trickle charge
current is 10% of the full-scale current. If the cell voltage
stays low for one quarter of the total charge time, the
charge sequence will terminate.
The charger can be shut down by floating the PROG pin
(ICC = 1mA). An internal current source will pull this pin
high and clamp it at 3.5V.
The charger goes into the fast charge constant-current
mode after the voltage on the BAT pin rises above 2.457V.
In constant-current mode, the charge current is set by the
When the input voltage is not present, the charger goes
into a sleep mode, dropping ICC to 7µA. This greatly
reduces the current drain on the battery and increases the
standby time.
combination of RSENSE and RPROG
.
When the battery approaches the final float voltage, the
charge current will begin to decrease. When the current
7
LTC1732-4/LTC1732-4.2
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APPLICATIONS INFORMATION
RPROG = (2.457V/500mA)(800Ω/0.2Ω) = 19.656k
Charger Conditions
For best stability over temperature and time, 1% resistors
are recommended. The closest 1% resistor value is 19.6k.
Thechargerisoffwhenanyofthefollowingconditionsexist:
the VCC pin voltage is less than 4.1V, the dropout voltage
(VCC – VBAT) is less than 54mV, or if the program resistor
isfloating.TheDRVpinispulleduptoVCC thuskeepingthe
MOSFEToff,andtheinternalresistordividerisdisconnected
to reduce the drain on the battery.
Programming the Timer
The programmable timer is used to terminate the charge
cycle. The length of the timer is programmed by an
external capacitor at the TIMER pin. The total charge time
is:
Undervoltage Lockout (UVLO)
Aninternalundervoltagelockoutcircuitmonitorstheinput
voltage and keeps the charger in shutdown mode until
VCC rises above 4.1V. To prevent oscillation around
VCC = 4.1V, the UVLO circuit has 200mV of hysteresis.
Time = (3 Hours)(CTIMER/0.1µF)
The timer starts when an input voltage greater than 4.1V
isappliedandtheprogramresistorisconnectedtoground.
After a time-out occurs, the CHRG output will turn into a
high impedance state to indicate that the charging has
stopped. Connecting the TIMER pin to VCC disables the
timer and also puts the charger into a constant-current
mode. To disable only the timer function, short the TIMER
pin to GND.
Trickle Charge and Defective Battery Detection
At the beginning of the charging sequence, if the battery
voltage is below 2.457V, the charger goes into trickle
mode. The charge current is dropped to 10% of the full-
scale current. If the low cell voltage persists for one
quarterofthetotalchargingtime,thebatteryisconsidered
defective, the charging will be terminated and the CHRG
pin output is forced to a high impedance state.
Battery Detection and Recharge
LTC1732-4: replacing the battery before the timer has ex-
pired will reset the timer, thus starting a new charge cycle,
provided the cell voltage of the new battery is less than
3.8V. If the new battery is greater than 3.8V, the timer will
not be reset and charging will continue for the remaining
portion of the time period. Replacing the battery after the
timer has expired will start a new charge cycle, regardless
of the battery voltage, provided the previous battery volt-
age exceeded 3.9V before the timer expired. After a com-
plete charge cycle has occurred (VBAT > 3.9V), and the
battery remains connected to the charger, a new charge
cycle will begin if the battery voltage drops below 3.8V
because of a load on the battery or self discharge.
Shutdown
The LTC1732 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. The DRV pin will then be pulled up to VCC and turn
off the external P-channel MOSFET. The internal timer is
reset in the shutdown mode.
Programming Charge Current
The formula for the battery charge current (see Block
Diagram) is:
LTC1732-4.2: replacing the battery before the timer has
expired will reset the timer, thus starting a new charge
cycle, provided the cell voltage of the new battery is less
than 4.05V. If the new battery is greater than 4.05V, the
timer will not be reset and charging will continue for the
remainingportionofthetimeperiod.Replacingthebattery
after the timer has expired will start a new charge cycle,
regardless of the battery voltage, provided the previous
battery voltage exceeded 4.1V before the timer expired.
2.457V 800Ω
RPROG RSENSE
IBAT
=
•
where RPROG is the total resistance from the PROG pin to
ground.
For example, if 0.5A charge current is needed, select a
value for RSENSE that will drop 100mV at the maximum
chargecurrent.RSENSE =0.1V/0.5A=0.2Ω,thencalculate:
8
LTC1732-4/LTC1732-4.2
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APPLICATIONS INFORMATION
After a complete charge cycle has occured (VBAT > 4.1V),
and the battery remains connected to the charger, a new
charge cycle will begin if the battery voltage drops below
4.05V because of a load on the battery or self discharge.
forcing the OUT pin into a high impedance state, the
current source will pull the pin low through the 400k
resistor. When the internal timer has expired, the CHRG
pin will change to high impedance state and the 400k
resistor will then pull the pin high to indicate the charging
has stopped.
For either version, to force a new charge cycle, regardless
of previous conditions, momentarily lift the program
resistor or remove and reapply the input power.
ACPR Output Pin
CHRG Status Output Pin
The LTC1732 has an ACPR output pin to indicate that the
input supply (wall adapter) is higher than 4.1V and 54mV
abovethevoltageattheBATpin.Whenbothconditionsare
met, the ACPR pin is pulled down to ground by an
N-channel MOSFET that is capable of driving an LED.
Otherwise, this pin is in a high impedance state.
Whenthechargecyclestarts, theCHRGpinispulleddown
to ground by an internal N-channel MOSFET that can drive
an LED. When the battery current drops to 10% of the full-
scale current (C/10), the N-channel MOSFET is turned off
and a weak 35µA current source to ground is connected
to the CHRG pin. A 15ms time delay is included to help
prevent false triggering due to transient currents. The
end-of-charge comparator is disabled in trickle charge
mode. After the timer expires, the charge cycle ends, and
thepingoesintoahighimpedancestate. Thetimerisused
to terminate the charge cycle. By using two different value
pull-upresistors,amicroprocessorcandetectthreestates
from this pin (charging, C/10 and stop charging). See
Figure 1.
End of Charge (C/10) Output
TheLTC1732includesacomparatortomonitorthecharge
current to detect an end-of-charge condition. This com-
parator does not terminate the charge cycle, but provides
an output signal to indicate a near full charge condition.
The timer is used to terminate the charge cycle. When the
battery current falls below 10% of full scale, the compara-
tor trips and turns off the N-channel MOSFET at the CHRG
pin and switches in a 35µA current source to ground. A
15ms time delay is included to help prevent false trigger-
ingduetotransientcurrents.Theend-of-chargecompara-
tor is disabled in trickle charge mode.
+
V
V
DD
8
V
CC
400k
2k
µPROCESSOR
LTC1732
CHRG
3
OUT
Output Voltage Selection
IN
ThefloatvoltageattheBATpincanbeselectedbytheSEL
pin. Shorting the SEL pin to ground will set the float
voltage to 4.1V, while connecting it to VCC sets it to 4.2V.
This feature allows the charger to be used with different
types of Li-Ion cells. When charging 4.1V cells, use the
LTC1732-4 with the SEL pin grounded. The LT1732-4
can also be used for charging 4.2V cells by connecting
the SEL pin to VCC. The recharge threshold level is preset
to 3.8V, thus allowing either 4.1V or 4.2V cells to be
charged. Because the recharge threshold voltage level of
the LTC1732-4.2 is preset for 4.05V, this version is not
recommended for 4.1V cells.
1732 F01
Figure 1. Microprocessor Interface
When the LTC1732 is in charge mode, the CHRG pin is
pulled low by the internal N-channel MOSFET. To detect
this mode, force the digital output pin, OUT, high and
measure the voltage at the CHRG pin. The N-channel
MOSFET will pull the pin low even with a 2k pull-up
resistor. Once the charge current drops to 10% of the full-
scale current (C/10), the N-channel MOSFET is turned off
and a 35µA current source is connected to the CHRG pin.
The IN pin will then be pulled high by the 2k pull-up. By
9
LTC1732-4/LTC1732-4.2
U
W U U
APPLICATIONS INFORMATION
Gate Drive
is required to properly terminate the charging by floating
the PROG pin.
Typically the LTC1732 controls an external P-channel
MOSFET to supply current to the battery. An external PNP
transistor can also be used as the pass transistor instead
oftheP-channelMOSFET.Duetothelowtransconductance
of the current amplifier (CA), a high gain Darlington PNP
transistor is required to avoid excessive charge current
error. The transconductance of the current amplifier is
around 0.6µA/mV. For every 1µA of base current, a 1.6mV
Stability
The charger is stable without any compensation when a
P-channel MOSFET is used as the pass transistor and
the battery is present. A 10µF tantalum capacitor is
recommended at the BAT pin to keep the ripple voltage
low when the battery is disconnected. A ceramic output
capacitor may also be used, but because of the very low
ESR and high Q characteristics of multilayer ceramic
capacitors, it may be necessary to add a 1Ω resistor in
series with the ceramic capacitor to improve voltage
mode stability.
of gain error shows up at the inputs of CA. With RPROG
=
19.6k (100mV across RSENSE). This represents a 1.6%
error in charge current.
Constant-Current Only Mode
The LTC1732 can be used as a programmable current
source by connecting the TIMER pin to VCC. This is
particularlyusefulforchargingNiMHorNiCdbatteries. In
the constant-current only mode, the timer and voltage
amplifierarebothdisabled.Anexternalterminationmethod
IfaPNPtransistorisusedforthepasstransistor,a1000pF
capacitor is required from the DRV pin to VCC. To help
stablize the voltage loop a 10µF tantalum capacitor at the
BAT pin is also recommended when a battery is not
present.
U
TYPICAL APPLICATIO S
Li-Ion Linear Charger Using a PNP Transistor
V
IN
= 6V
MBRM120T3
R
SENSE
R2
1k
C1
1nF
R3
10k
C3
1µF
0.2Ω
R1
1k
8
V
CC
Q2
ZTX749
9
7
3
CHRG SENSE
10
Q1
2N5087
DRV
ACPR
LTC1732-4
I
= 500mA
BAT
4
1
6
TIMER
BAT
PROG
C
TIMER
0.1µF
SEL
2
GND
5
4.1V
Li-Ion
CELL
C2
10µF
+
R
PROG
19.6k
1732 TA02
10
LTC1732-4/LTC1732-4.2
U
PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
MS10 Package
10-Lead Plastic MSOP
(LTC DWG # 05-08-1661)
0.118 ± 0.004*
(3.00 ± 0.102)
10 9
8
7 6
0.118 ± 0.004**
(3.00 ± 0.102)
0.193 ± 0.006
(4.90 ± 0.15)
1
2
3
4 5
0.034
(0.86)
REF
0.043
(1.10)
MAX
0.007
(0.18)
0° – 6° TYP
SEATING
PLANE
0.007 – 0.011
(0.17 – 0.27)
0.021 ± 0.006
(0.53 ± 0.015)
0.005 ± 0.002
(0.13 ± 0.05)
MSOP (MS10) 1100
0.0197
(0.50)
BSC
* DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH,
PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
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.
11
LTC1732-4/LTC1732-4.2
U
TYPICAL APPLICATIO
Single Cell 4.1V, High Efficiency 1.5A Li-Ion Battery Charger
V
IN
6V
D2
MBRS130LT3
+
C4
R1
1k
C2
1k
0.47µF
22µF
8
R3
R2
4.7Ω
0.082Ω
V
CC
1/4W
9
7
3
CHRG SENSE
2
D1
10
8
7
1
Q2
MBRS130LT3
ACPR
DRV
Si2305DS
LTC1693-5
LTC1732-4
4
4
1
6
TIMER
BAT
15µH
CDRH6D28-150NC
PROG
C1
0.1µF
R4
19.6k
SEL
2
GND
5
+
1-CELL
+
C3
220µF
Li-Ion
BATTERY
1732 TA03
RELATED PARTS
PART NUMBER
LT®1510-5
LT1512
DESCRIPTION
COMMENTS
500kHz Constant-Voltage/Constant-Current Battery Charger Most Compact, Up to 1.5A, Charges NiCd, NiMH, Li-Ion Cells
SEPIC Battery Charger
V Can Be Higher or Lower Than Battery Voltage, 1.5A Switch
IN
LTC1541
Op Amp, Comparator and Reference with 5µA I
Rail-to-Rail Current Sense Amplifier
Termination Controller for Li-Ion
Low Cost Linear Charger—See Design Note 188
CC
LT1620
Precise Output Current Programming, Up to 32V V , Up to 10A I
OUT
OUT
LTC1729
Time or Charge Current Termination, Automatic Charger/Battery
Detection, Status Output, Preconditioning, 8-Lead MSOP
LTC1730
LTC1734
Li-Ion Pulse Charger
Minimum Heat Dissipation; No Reverse Current Diode Needed; No
MOSFET Required; Limits Charge Current for Safety
ThinSOTTM Li-Ion Linear Battery Charger
Only Two External Components; Charge Termination and Gas Gauging
Provided by Monitoring V Pin.
PROG
ThinSOT is a trademark of Linear Technology Corporation.
1732f LT/TP 0501 2K • PRINTED IN THE USA
LINEAR TECHNOLOGY CORPORATION 2000
12 LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
●
●
(408)432-1900 FAX:(408)434-0507 www.linear-tech.com
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