LINER LTC1732-4_00

Final Electrical Specifications
LTC1732-4/LTC1732-4.2
Lithium-Ion Linear
Battery Charger Controller
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FEATURES
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DESCRIPTIO
The LTC ®1732 is a complete constant-current/constantvoltage linear charge controller for lithium-ion
(Li-Ion) batteries. Nickel-cadmium (NiCd) and nickel metalhydride (NiMH) batteries can also be charged with constant current using external termination. Charge current
can be programmed with 7% (max) accuracy using external 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
4.5V to 12V Input Voltage Range
Programmable Charge Current
C/10 Charge Current Detection Output
Programmable Charge Termination Timer
Small, Thin 10-Pin MSOP Package
Select Pin to Charge Either 4.1V or
4.2V Cells (LTC1732-4)
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 and Automatic Charging
of Low-Battery Cell
Input Supply (Wall Adapter) Detection Output
4.05V Recharge Threshold for 4.2V Cells
(LTC1732-4.2)
3.8V Recharge Threshold for 4.1V or 4.2V Cells
(LTC1732-4)
When the input supply is removed, the LTC1732 automatically 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 begin.
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APPLICATIONS
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October 2000
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.
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TYPICAL APPLICATION
Single Cell 4.2V Li-Ion Battery Charger
VIN = 6V
MBRM120T3
R2
1k
R1
1k
8
2
VCC
SEL
SENSE
3
DRV
CHRG
RSENSE
0.2Ω
9
7
Q1
Si9430DY
LTC1732-4
10
4
CTIMER
0.1µF
ACPR
BAT
TIMER
PROG
GND
5
1µF
IBAT = 500mA
1
6
RPROG*
19.6k
10µF
+ 4.2V
Li-Ion
CELL
1732 TA01
*SHUTDOWN INVOKED BY FLOATING THE PROG PIN
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.
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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
9
8
7
6
ACPR
SENSE
VCC
DRV
PROG
LTC1732EMS-4
LTC1732EMS-4.2
MS10 PART MARKING
MS10 PACKAGE
10-LEAD PLASTIC MSOP
LTNJ
LTUA
TJMAX = 140°C, θJA = 180°C/W
Consult factory for Industrial and Military grade parts.
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
VCC
Input Supply Voltage
ICC
Input Supply Current
Charger On, Current Mode
Shutdown Mode
Sleep Mode (Battery Drain Current)
●
●
VBAT
Regulated Output Voltage
LTC1732-4; 5V ≤ VCC ≤ 12V, VSEL = GND
LTC1732-4/LTC1732-4.2; 5V ≤ VCC ≤ 12V, VSEL = VCC
●
●
IBAT
Current Mode Charge Current
RPROG = 19.6k, RSENSE = 0.2Ω
RPROG = 19.6k, RSENSE = 0.2Ω
●
●
TYP
4.5
MAX
UNITS
12
V
1
1
7
3
3
20
mA
mA
µA
4.059
4.158
4.1
4.2
4.141
4.242
465
415
500
535
585
mA
mA
V
V
RPROG = 97.6k, RSENSE = 0.2Ω
60
100
140
mA
ITRIKL
Trickle Charge Current
VBAT = 2V, RPROG = 19.6k, ITRIKL = (VCC – VSENSE)/0.2Ω ●
30
50
110
mA
VTRIKL
Trickle Charge Threshold Voltage
From Low to High
●
2.35
2.457
2.55
V
VUV
VCC Undervoltage Lockout Voltage
From Low to High
●
4.1
4.5
∆VUV
VCC Undervoltage Lockout Hysteresis
VMSD
Manual Shutdown Threshold Voltage
PROG Pin Low to High
PROG Pin High to Low
VASD
Automatic Shutdown Threshold Voltage
(VCC – VBAT) High to Low
(VCC – VBAT) Low to High
VDIS
Voltage Mode Disable Threshold Voltage
VDIS = VCC – VTIMER
IPROG
PROG Pin Current
Internal Pull-Up Current, No RPROG
PROG Pin Source Current, ∆VPROG ≤ 5mV
200
VPROG
PROG Pin Voltage
RPROG =19.6k
VACPR
ACPR Pin Output Low Voltage
IACPR = 5mA
ICHRG
CHRG Pin Weak Pull-Down Current
VCHRG = 1V
VCHRG
CHRG Pin Output Low Voltage
ICHRG = 5mA
VSEL
SEL Pin Threshold
2
2.457
2.446
30
40
54
69
V
V
90
100
0.4
●
●
0.3
mV
mV
V
2.5
µA
µA
2.457
V
300
15
V
mV
0.7
1.2
V
35
55
µA
0.6
1.2
V
2
V
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
IC/10
End of Charge Indication Current Level
RPROG = 19.6k, RSENSE = 0.2Ω
tTIMER
TIMER Accuracy
CTIMER = 0.1µF
VRECHRG
Recharge Battery Voltage Threshold per Cell
VBAT from High to Low (LTC1732-4)
VBAT from High to Low (LTC1732-4.2)
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
MIN
●
25
3.72
3.95
TYP
MAX
UNITS
50
100
mA
10
%
3.80
4.05
V
V
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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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. Grounding this pin will set the output float voltage to 4.1V per cell,
while connecting to VCC will set the voltage to 4.2V per cell.
For the LTC1732-4.2, the SEL pin must be connected to
VCC.
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, CTIMER, to GND. The timer period is tTIMER =
(CTIMER • 3 hours)/(0.1µF). When the TIMER pin is
connected to VCC, the timer is disabled, the constantvoltage 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 connecting 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.
DRV (Pin 7): Drive Output Pin for the P-Channel MOSFET
or PNP Transistor. The impedance is high at this pin,
therefore, a high gain PNP pass transistor should be used.
VCC (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)
ACPR (Pin 10): Wall Adapter Present Output. When the
input voltage (wall adaptor) 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.
3
LTC1732-4/LTC1732-4.2
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BLOCK DIAGRA
VCC
7
+
3.8V
C5
–
RSENSE
SENSE
+
2
+
–
800Ω
80Ω
C1
–
CHRG
8
54mV
+
C4
–
–
C/10 STOP RECHRG C/10
+
SHDN
3
TIMER
720Ω
LOGIC
DRV
CA
SLP
OSCILLATOR
BAT
LBO
COUNTER
1
C2
SEL
VREF
2
–
ACPR
+
+
C3
–
VA
VCC
A1
–
+
10
6
+
ACPR
–
35µA
2.5µA
VREF
2.457V
CHARGE
5
BATTERY CURRENT IBAT = (2.457V • 800Ω)/(RPROG • RSENSE)
PROG
GND
4
1732 BD
RPROG
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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
amplifier servos the gate of the external P-channel MOSFET
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
4
(VA) will start sinking current which shrinks the voltage
drop across RSENSE, thus reducing the charge current.
Charging begins when the potential at 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.
LTC1732-4/LTC1732-4.2
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OPERATIO
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
combination of RSENSE and RPROG.
continue for the remaining charge time. In the case when
a time out has occurred, a new battery with the cell voltage
of less than 3.8V can be inserted and charged automatically with the full programmed charge time.
When the battery approaches the final float voltage, the
charge current will begin to decrease. When the current
drops to 10% of the full-scale charge current, an internal
comparator will turn off the pull-down N-channel MOSFET
at the CHRG pin and connect a weak current source to
ground to indicate an end-of-charge (C/10) condition.
For batteries like lithium-ion that require accurate final
float potential, the internal 2.457V reference, voltage amplifier and the resistor divider provide regulation with ±1%
(max) accuracy. For NiMH and NiCd batteries, the LTC1732
can be turned into 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.
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 impedance state. To restart the charge cycle, simply remove the
input voltage and reapply it, or float the PROG pin momentarily.
Replacing the battery while in the charge mode will cause
the timer to be reset if the cell voltage of the new battery
is below 3.8V. If the voltage is above 3.8V, the timer will
The charger can be shut down by floating the PROG pin.
An internal current source will pull this pin high and clamp
it at 3.5V.
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.
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APPLICATIONS INFORMATION
Stop Charging
The charger is off when any of the following conditions exist:
the voltage at the VCC pin is below 4.1V, the voltage at the
VCC pin is higher than 4.1V but is less than 54mV above
VBAT, or the PROG pin is floating. The DRV pin will be pulled
to VCC and the internal resistor divider is disconnected to
reduce the current drain on the battery.
Undervoltage Lockout (UVLO)
An internal undervoltage lockout circuit monitors the input
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 built-in hysteresis.
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 fullscale current. If the low cell voltage persists for one
quarter of the total charging time, the battery is considered
defective, the charging will be terminated and the CHRG
pin output is forced to a high impedance state.
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:
IBAT = (IPROG)(800Ω/RSENSE)
= (2.457V/RPROG)(800Ω/RSENSE)
where RPROG is the total resistance from the PROG pin to
ground.
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LTC1732-4/LTC1732-4.2
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APPLICATIONS INFORMATION
For example, if 0.5A charge current is needed, select a
value for RSENSE that will drop 100mV at the maximum
charge current. RSENSE = 0.1V/0.5A = 0.2Ω, then calculate:
RPROG = (2.457V/500mA)(800Ω/0.2Ω) = 19.656k
For best stability over temperature and time, 1% resistors
are recommended. The closest 1% resistor value is 19.6k.
Programming the Timer
The programmable timer is used to terminate the charging. The length of the timer is programmed by an external
capacitor at the TIMER pin. The total charge time is:
Time = (3 Hours)(CTIMER/0.1µF)
The timer starts when an input voltage greater than 4.1V
is applied and the program resistor is connected to ground.
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 only disable the timer function, short the TIMER
pin to GND.
CHRG Status Output Pin
When the charge cycle starts, the CHRG pin is pulled down
to ground by an internal N-channel MOSFET that can drive
an LED. When the battery current drops to 10% of the fullscale current (C/10), the N-channel MOSFET is turned off
and a weak 35µA current source to ground is connected to
the CHRG pin. After a time-out occurs, the pin will go into
a high impedance state. By using two different value pullup resistors, a microprocessor can detect three states
from this pin (charging, C/10 and stop charging). See
Figure 1.
V+
VDD
400k
LTC1732
CHRG
3
µPROCESSOR
1k
OUT
IN
1732 F01
Figure 1. Microprocessor Interface
6
ACPR Output Pin
The LTC1732 has an ACPR output pin to indicate that the
input supply (wall adapter) is higher than 4.1V and 55mV
above the voltage at the BAT pin. When both conditions are
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.
End of Charge (C/10)
The LTC1732 includes a comparator to monitor the charge
current to detect an end-of-charge condition. When the
battery current falls below 10% of full scale, the comparator trips and turns off the N-channel MOSFET at the CHRG
pin and switches in a 35µA current source to ground. After
an internal time delay of 15ms, this state is then latched.
This delay will help prevent false triggering due to transient currents. The end-of-charge comparator is disabled
in trickle charge mode.
Output Voltage Selection
8
VCC
When the LTC1732 is in charge mode, the CHRG pin is
pulled low by an 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 1k pull-up
resistor. Once the charge current drops to 10% of the fullscale 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 1k pull-up. By
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.
The float voltage at the BAT pin can be selected by the SEL
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. 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. When
LTC1732-4/LTC1732-4.2
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APPLICATIONS INFORMATION
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).
Gate Drive
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
of the P-channel MOSFET. Due to the low current gain of
the current amplifier (CA), a high gain Darlington PNP
transistor is required to avoid excessive charge current
error. The gain of the current amplifier is around 0.6µA/
mV. For every 1µA of base current, a 1.6mV of gain error
shows up at the inputs of CA. With RPROG = 19.6k (100mV
across RSENSE), it represents 1.67% of error in charging
current.
Constant-Current Only Mode
The LTC1732 can be used as a programmable current
source by connecting the TIMER pin to VCC. This is
particularly useful for charging NiMH or NiCd batteries. In
the constant-current only mode, the timer and voltage
amplifier are both disabled. An external termination method
is required to properly terminate the charge.
Battery Detection
The LTC1732 can detect the insertion of a new battery.
When a battery with cell voltage of less than 3.8V is
inserted, the LTC1732 resets the timer and starts the
charging cycle immediately. If the cell voltage of the new
battery is above 3.8V, the charging will not start. If a new
battery (with cell voltage above 3.8V) is inserted while in
the charging process, the timer will not be reset. It will
continue until the timer runs out.
After a time out has occurred and the battery remains
connected, a new charge cycle will begin if the battery
voltage drops below 3.8V (LTC1732-4) or 4.05V (LTC17324.2) due to self-discharge or external loading.
Stability
The charger is stable without any compensation when a
P-channel MOSFET is used as the pass transistor.
However, a 10µF capacitor is recommended at the BAT
pin to keep the ripple voltage low when the battery is
disconnected.
If a PNP transistor is used for the pass transistor, a 1000pF
capacitor is required from the DRV pin to VCC. This
capacitor is needed to help stablize the voltage loop. A
10µF capacitor at the BAT pin is also recommended when
a battery is not present.
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TYPICAL APPLICATIO S
Linear Charger Using a PNP Transistor
VIN = 6V
MBRM120T3
R1
1k
R2
1k
C1
1nF
8
3
10
VCC
CHRG
SENSE
ACPR
DRV
CTIMER
0.1µF
TIMER
BAT
PROG
SEL
GND
2
5
RSENSE
0.2Ω
C3
1µF
Q2
ZTX749
9
7
Q1
2N5087
LTC1732-4
4
R3
10k
IBAT = 500mA
1
6
RPROG
19.6k
C2
10µF
+
4.1V
Li-Ion
CELL
1732 TA02
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LTC1732-4/LTC1732-4.2
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TYPICAL APPLICATIO S
Single Cell 4.1V, 1.5A Li-Ion Battery Charger
VIN
6V
D2
MBRS130LT3
R1
1k
1k
VCC
3
10
CHRG
SENSE
ACPR
DRV
TIMER
BAT
PROG
C1
0.1µF
SEL
GND
2
5
C2
22µF
R3
0.082Ω
1/4W
R2
4.7Ω
9
7
3
TPS2829DBVR
LTC1732-4
4
+
C4
0.47µF
8
5
D1
Q2
MBRS130LT3
Si2305DS
4
2
1
15µH
CDRH6D28-150NC
6
R4
19.6k
+ 1-CELL
+
Li-Ion
BATTERY
C3
220µF
1732 TA03
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PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
MS10 Package
10-Lead Plastic MSOP
(LTC DWG # 05-08-1661)
0.040 ± 0.006
(1.02 ± 0.15)
0.007
(0.18)
0.034 ± 0.004
(0.86 ± 0.102)
0.118 ± 0.004*
(3.00 ± 0.102)
10 9 8 7 6
0° – 6° TYP
0.021 ± 0.006
(0.53 ± 0.015)
SEATING
PLANE 0.009
(0.228)
REF
0.0197
(0.50)
BSC
0.006 ± 0.004
(0.15 ± 0.102)
0.118 ± 0.004**
(3.00 ± 0.102)
0.193 ± 0.006
(4.90 ± 0.15)
MSOP (MS10) 1098
* 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
1 2 3 4 5
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LTC1731
Li-Ion Linear Battery Charger Controller
CC/CV Charges Li-Ion Cells, 8-Lead MSOP, Programmable Timer
®
8
Linear Technology Corporation
1732i LT/LCG 1000 4K • PRINTED IN THE USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com
 LINEAR TECHNOLOGY CORPORATION 2000