1
LTC1731-8.2/LTC1731-8.4
sn1731 17318fs
FEATURES
APPLICATIO S
U
DESCRIPTIO
U
TYPICAL APPLICATIO
U
Lithium-Ion Linear
Battery Charger Controller
The LTC
®
1731-8.2/LTC1731-8.4 are complete constant-
current/constant-voltage linear charger controllers for 2-
cell lithium-ion (Li-Ion)batteries. Nickel-cadmium (NiCd)
and nickel-metal-hydride (NiMH) batteries can also be
charged with constant current using external termina-
tion. The external sense resistor sets the charge current
with 7% accuracy. An internal resistor divider and preci-
sion reference set the final float potential with 1% accu-
racy. The output float voltages are set internally to 8.2V
(LTC1731-8.2) or 8.4V (LTC1731-8.4).
When the input supply is removed, the LTC1731-8.2/
LTC1731-8.4 automatically enter a low current sleep mode,
dropping the battery drain current to typically 15µA. An
internal comparator detects the end-of-charge (C/10) con-
dition while a programmable timer, using an external
capacitor, sets the total charge time. Fully discharged cells
are automatically trickle charged at 10% of the pro-
grammed current until battery voltage exceeds 4.95V.
The LTC1731-8.2/LTC1731-8.4 are available in the 8-pin
MSOP and SO packages. For 1-cell Li-Ion battery charg-
ing, see the LTC1731-4.1 and LTC1731-4.2 data sheets.
■
Complete Linear Charger Controller for
2-Cell Lithium-Ion Batteries
■
1% Voltage Accuracy
■
Programmable Charge Current
■
C/10 Charge Current Detection Output
■
Programmable Charge Termination Timer
■
Space Saving 8-Pin MSOP Package
■
Automatic Sleep Mode When Input Supply
is Removed (15µA Battery Drain)
■
Automatic Trickle Charging of Low Voltage Cells
■
Programmable for Constant-Current-Only Mode
■
Cellular Phones
■
Handheld Computers
■
Charging Docks and Cradles
■
Programmable Current Source
, LTC and LT are registered trademarks of Linear Technology Corporation.
400mA Li-Ion Charger
V
CC
V
IN
= 9V
SENSE
DRV
2k R
SENSE
0.2Ω
R
PROG
*
19.6k 2-CELL
Li-ION
LTC1731-8.4
*SHUTDOWN INVOKED BY FLOATING THE PROG PIN
BAT
CHRG
8
7
MBRM120T3
10µF
1731 TA01
1µF
I
BAT
= 400mA
C
TIMER
0.1µF
Q1
Si9430DY
6
1
5
4
2
3TIMER
PROG
GND
+
CHARGE
STATUS
Typical Li-Ion Charge Cycle
TIME (HOURS)
0
CHARGE CURRENT (mA)
400
300
200
100
0
9
8
7
6
1.5 2.5
1731 TA01b
0.5 1.0 2.0 3.0
CONSTANT
VOLTAGE
CONSTANT
CURRENT
TIMER
STOPS
CHRG
LED OFF
BATTERY VOLTAGE
400mA HR BATTERY
CHARGE CURRENT
BATTERY VOLTAGE(V)
2
LTC1731-8.2/LTC1731-8.4
sn1731 17318fs
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
CC
Input Supply Voltage ●8.8 12 V
I
CC
Input Supply Current Charger On, Current Mode ●13 mA
Shutdown Mode ●12 mA
Sleep Mode (Battery Drain Current) 15 30 µA
V
BAT
Regulated Output Voltage LTC1731-8.2 (9V ≤ V
CC
≤ 12V) ●8.118 8.2 8.282 V
LTC1731-8.4 (9V ≤ V
CC
≤ 12V) ●8.316 8.4 8.484 V
I
BAT
Current Mode Charge Current R
PROG
= 19.6k, R
SENSE
= 0.2Ω465 500 535 mA
R
PROG
= 19.6k, R
SENSE
= 0.2Ω●415 500 585 mA
R
PROG
= 97.6k, R
SENSE
= 0.2Ω70 100 130 mA
I
TRIKL
Trickle Charge Current V
BAT
= 4V, R
PROG
= 19.6k, I
TRIKL
= (V
CC
– V
SENSE
)/0.2Ω●30 50 100 mA
V
TRIKL
Trickle Charge Threshold Voltage BAT Rising ●4.7 4.95 5.1 V
V
UV
V
CC
Undervoltage Lockout Voltage V
CC
Rising ●8.2 8.8 V
∆V
UV
V
CC
Undervoltage Lockout Hysteresis V
CC
Falling 200 mV
V
MSD
Manual Shutdown Threshold Voltage PROG Pin Rising 2.457 V
PROG Pin Falling 2.446 V
I
DRV
Drive Pin Current V
DRV
= V
CC
– 2V 26 µA
ORDER PART
NUMBER
(Note 1)
Input Supply Voltage (V
CC
) ................................... 13.2V
SENSE, DRV, BAT, TIMER, PROG ............ –0.3V to V
CC
CHRG..................................................... –0.3V to 13.2V
LTC1731EMS8-8.2
LTC1731EMS8-8.4
T
JMAX
= 150°C, θ
JA
= 200°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ABSOLUTE MAXIMUM RATINGS
W
WW
U
PACKAGE/ORDER INFORMATION
W
UU
Operating Temperature Range (Note 2) .....–40° to 85°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
MS8 PART MARKING
LTSW
LTPE
1
2
3
4
BAT
CHRG
TIMER
GND
8
7
6
5
SENSE
V
CC
DRV
PROG
TOP VIEW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
ORDER PART
NUMBER
LTC1731ES8-8.2
LTC1731ES8-8.4
S8 PART MARKING
173182
173184
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 9V unless otherwise noted.
ELECTRICAL CHARACTERISTICS
1
2
3
4
8
7
6
5
TOP VIEW
SENSE
V
CC
DRV
PROG
BAT
CHRG
TIMER
GND
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 150°C, θ
JA
= 125°C/W
3
LTC1731-8.2/LTC1731-8.4
sn1731 17318fs
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
ASD
Automatic Shutdown Threshold Voltage (V
CC
– V
BAT
) Falling 30 54 90 mV
(V
CC
– V
BAT
) Rising 40 69 100 mV
V
DIS
Voltage Mode Disable Threshold Voltage V
DIS
=
(V
CC
– V
TIMER
)●0.4 V
I
PROG
PROG Pin Current Internal Pull-Up Current, No R
PROG
2.5 µA
PROG Pin Load Regulation PROG Pin Source Current, ∆V
PROG
≤ 5mV ●300 µA
V
PROG
PROG Pin Voltage R
PROG
=19.6k 2.457 V
I
CHRG
CHRG Pin Weak Pull-Down Current V
CHRG
= 1V 50 100 150 µA
V
CHRG
CHRG Pin Output Low Voltage I
CHRG
= 5mA 0.6 1.2 V
I
C/10
End of Charge Indication Current Level R
PROG
= 19.6k, R
SENSE
= 0.2Ω●25 50 100 mA
t
TIMER
TIMER Accuracy C
TIMER
= 0.01µF10%
V
CLAMP
DRV Pin Clamp Voltage V
CLAMP
= V
CC
– V
DRV
, I
DRIVE
= 50µA 6.5 V
ELECTRICAL CHARACTERISTICS
Note 2: The LTC1731E-8.2/LTC1731E-8.4 are 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. Consult
factory for I grade parts.
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 9V unless otherwise noted.
TYPICAL PERFOR A CE CHARACTERISTICS
UW
V
CC
(V)
9
I
TRKL
(mA)
10 11 12
1731 G01
60
55
50
45
40
R
PROG
= 19.6K
R
SENSE
= 0.2Ω
V
BAT
= 4V
T
A
= 25°
Trickle Charge Current
vs VCC
I
TRKL
(mA)
60
55
50
45
40
TEMPERATURE (°C)
–50 100
1731 G06
050–25 25 75 125
R
PROG
= 19.6K
R
SENSE
= 0.2Ω
V
BAT
= 4V
V
CC
= 9V
VCC (V)
9
VTRKL (V)
10 11 12
1731 G08
4.96
4.95
4.94
4.93
4.92
4.91
4.90
4.89
4.88
RPROG = 19.6K
TA = 25°
Trickle Charge Current
vs Temperature Trickle Charge Threshold Voltage
vs VCC
4
LTC1731-8.2/LTC1731-8.4
sn1731 17318fs
TYPICAL PERFOR A CE CHARACTERISTICS
UW
TEMPERATURE (°C)
–50
t
TIMER
(%)
100
1731 G04
050
110
105
100
95
90 –25 25 75 125
C
TIMER
= 0.1µF
V
CC
= 9V
V
CC
(V)
9
t
TIMER
(%)
10 11 12
1731 G05
110
105
100
95
90
C
TIMER
= 0.1µF
V
BAT
= 6V
T
A
= 25°
V
CC
(V)
9
I
BAT
(mA)
10 11 12
1731 G09
520
510
500
490
480
R
PROG
= 19.6K
R
SENSE
= 0.2Ω
V
BAT
= 6V
T
A
= 25°
VCC (V)
9
VPROG (V)
10 11 12
1731 G10
2.48
2.47
2.46
2.45
2.44
RPROG = 19.6K
VBAT = 6V
TA = 25°
Timer Accuracy vs Temperature
Timer Accuracy vs VCC
Battery Charge Current
vs Temperature
Battery Charge Current
vs VCC
Program Pin Voltage
vs VCC
I
BAT
(mA)
540
530
520
510
500
490
480
470
460
TEMPERATURE (°C)
–50 100
1731 G07
050–25 25 75 125
R
PROG
= 19.6K
R
SENSE
= 0.2Ω
V
BAT
= 6V
V
CC
= 9V
TEMPERATURE (°C)
–50
V
PROG
(V)
100
1731 G02
050
2.470
2.465
2.460
2.455
2.450 –25 25 75 125
R
PROG
= 19.6k
V
CC
= 9V
TEMPERATURE (°C)
–50
V
TRKL
(V)
100
1731 G03
050
4.94
4.93
4.92
4.91
4.90 –25 25 75 125
V
CC
= 9V
Trickle Charge Threshold Voltage
vs Temperature
Program Pin Voltage
vs Temperature
5
LTC1731-8.2/LTC1731-8.4
sn1731 17318fs
PIN FUNCTIONS
UUU
BAT (Pin 1): Battery Sense Input. A bypass capacitor of at
least 10µF is required to keep the loop stable when the
battery is not connected. A precision internal resistive
divider sets the final float potential on this pin. The resistor
divider is disconnected in sleep mode.
CHRG (Pin 2): 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 at least 0.32
seconds, the N-channel MOSFET turns off and a 100µA
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 3): Timer Capacitor and Constant-Voltage
Mode Disable Input Pin. A capacitor CTIMER connected
from this pin to ground sets a 30 hour/µF time period for
charge termination. When the TIMER pin is connected to
VCC, the constant-voltage mode and the timer is disabled
and the IC will operate in constant-current mode only.
Short the TIMER pin to GND to disable the internal timer
and the C/10 functions.
GND (Pin 4): Ground.
PROG (Pin 5): 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 6): Drive Output Pin for the P-Channel MOSFET
or PNP Transistor. If a PNP transistor is used, it must have
high gain (see Applications Information section). The DRV
pin is internally clamped to 6.5V below V
CC
.
V
CC
(Pin 7): Input Supply Voltage. V
CC
ranges from 8.8V
to 12V when charging. If V
CC
drops below V
BAT
+ 54mV,
for example when the input supply is disconnected, then
the IC enters sleep mode with I
CC
< 30µA. Bypass this pin
with a 1µF capacitor.
SENSE (Pin 8): Current Sense Input. Connect this pin to
the sense resistor. Choose the resistor value using the
following equation:
R
SENSE
= (V
PROG
• 800Ω)/(R
PROG
• I
BAT
)
6
LTC1731-8.2/LTC1731-8.4
sn1731 17318fs
BLOCK DIAGRA
W
–
+
–
+
–
+
–
+
LOGIC
C1
–
+
C4
–
+
–
+
C3 A1
CA
C2
VA
CHARGE
GND
1731 BD
PROG
BATTERY CURRENT I
BAT
= (2.457V • 800Ω)/(R
PROG
• R
SENSE
)R
PROG
V
REF
2.457V
4.9V
LBO
80Ω
V
CC
800Ω54mV
R
SENSE
SENSE
DRV
BAT
720Ω
100µA
TIMER OSCILLATOR
V
REF
COUNTER
STOP
SHDN SLP
C/10 C/10
2.5µA
V
CC
CHRG
4
5
2
3
8
7
6
1
+
–
7
LTC1731-8.2/LTC1731-8.4
sn1731 17318fs
OPERATIO
U
The LTC1731-8.2/LTC1731-8.4 are linear battery charger
controllers. The charge current is programmed by the
combination of a program resistor (R
PROG
) from the
PROG pin to ground and a sense resistor (R
SENSE
) be-
tween the V
CC
and SENSE pins. R
PROG
sets a program
current through an internal trimmed 800Ω resistor that
creates a voltage drop from V
CC
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 R
SENSE
which sets the charge current. When
the potential at the BAT pin approaches the preset float
voltage, the voltage amplifier (VA) will start sinking cur-
rent which shrinks the voltage drop across R
SENSE
, thus
reducing the charge current.
Charging begins when the potential at V
CC
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 4.95V, 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 goes into the fast charge constant-current
mode after the voltage on the BAT pin rises above 4.95V.
In constant-current mode, the charge current is set by the
combination of R
SENSE
and R
PROG
.
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 N-channel MOSFET at the
CHRG pin and connect a weak current source to ground to
indicate a near 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
input voltage and reapply it, or float the PROG pin momen-
tarily.
For batteries like lithium-ion that require an 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
LTC1731-8.2/LTC1731-8.4
can be turned into a current
source by pulling the TIMER pin to V
CC
. When in the
constant-current only mode, the voltage amplifier, timer
and the trickle charge function are all disabled.
The charger can be shut down by floating the PROG pin
(I
CC
≈ 1mA). An internal current source will pull it high and
clamp at 3.5V.
When the input voltage is not present, the charger goes
into a sleep mode, dropping I
CC
to 15µA. This greatly
reduces the current drain on the battery and increases the
standby time.
8
LTC1731-8.2/LTC1731-8.4
sn1731 17318fs
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 charge.
The length of the timer is programmed by an external
capacitor at the TIMER pin. The total charge time is:
Time (Hours) = (3 Hours)(C
TIMER
/0.1µF)
The timer starts when the input voltage greater than 8.2V
is applied and the program resistor is connected to ground.
After a time-out occurs, the CHRG output will become high
impedance indicating that the charge cycle has ended.
Connecting the TIMER pin to V
CC
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 to
ground by an internal N-channel MOSFET that can drive an
LED. When the charge current drops to 10% of the full-
scale current (C/10), the N-channel MOSFET turns off and
a weak 100µA current source to ground is connected to the
CHRG pin. After a time-out occurs, the CHRG pin goes
high impedance indicating that the charge cycle has ended.
By using two different value pull-up resistors, a micropro-
cessor can detect three states from this pin (charging,
C/10 and stop charging). See Figure 1.
APPLICATIONS INFORMATION
WUUU
Charger Conditions
The charger is off when any of the following conditions
exist: the V
CC
pin is less than 8.2V, the droput voltage (V
CC
- V
BAT
) is less than 54mV, the PROG pin is floating, or the
timer has ended. The DRV pin will be pulled to V
CC
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 V
CC
rises above 8.2V. To prevent oscillation around
V
CC
= 8.2V, 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 less than 4.95V the charger goes into trickle
charge mode. The charge current is reduced to 10% of the
full-scale current. If the low battery voltage persists for
one quarter of the total charging time, the battery is
considered defective, charging will be terminated and the
CHRG pin output is forced to a high impedance state.
Shutdown
The
LTC1731-8.2/LTC1731-8.4
can be forced into shut-
down 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 is then pulled
up to V
CC
turning 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:
I
BAT
= (2.457V/R
PROG
)(800Ω/R
SENSE
)
where R
PROG
is the total resistance from the PROG pin to
ground.
For example, if 0.5A charge current is needed, select a
value for R
SENSE
that will drop 100mV at the maximum
charge current. R
SENSE
= 0.1V/0.5A = 0.2Ω, then calculate:
R
PROG
= (2.457V/500mA)(800Ω/0.2Ω) = 19.656k
2k
100k
CHRG
1731 F01
V
CC
LTC1731-8.4
V
+
V
DD
OUT
µPROCESSOR
IN
2
7
Figure 1. Microprocessor Interface
9
LTC1731-8.2/LTC1731-8.4
sn1731 17318fs
When the LTC1731 is in the charge mode, the CHRG pin
is pulled to ground 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 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 100µA current source is connected to the CHRG pin.
By forcing the OUT pin into a high impedance state, the
current source will pull the pin low through the 100k
resistor. When the internal timer has expired, the CHRG
pin will change to high impedance and the 100k resistor
will then pull the pin high to indicate the charge cycle has
ended.
End of Charge (C/10)
The LTC1731-8.2/LTC1731-8.4 include a comparator to
monitor the charge current to detect a near end-of-charge
condition. This comparator does not terminate the charge
cycle, but provides and 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 comparator trips and turns off the N-channel
MOSFET at the CHRG pin and switches in a 100µA current
source to ground. After an internal time delay of 320ms,
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.
Gate Drive
Typically the LTC1731-8.2/LTC1731-8.4 drive an external
P-channel MOSFET to supply current to the battery. The
DRV pin is internally clamped to 6.5V below V
CC
. This
feature allows low voltage P-channel MOSFETs with gate
to source breakdown voltage rated at 8V to be used.
APPLICATIONS INFORMATION
WUUU
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
charging current error. The gain of the current amplifier is
around 0.6µA/mV. For every 1µA of base current, a 1.6mV
gain error shows up at the inputs of CA. With R
PROG
=
19.6k and 100mV across R
SENSE
, this gain error causes a
1.67% error in charge current.
Constant-Current Only Mode
The LTC1731-8.2/LTC1731-8.4 can be used as a pro-
grammable current source by forcing the TIMER pin to
V
CC
. 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 termina-
tion method is required to properly terminate the charge.
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. 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.
When a PNP transistor is chosen as the pass transistor, a
1000pF capacitor is required from the DRV pin to V
CC
. 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.
10
LTC1731-8.2/LTC1731-8.4
sn1731 17318fs
PACKAGE DESCRIPTION
U
MS8 Package
8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1660)
MSOP (MS8) 1001
0.53 ± 0.015
(.021 ± .006)
SEATING
PLANE
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
0.18
(.077)
0.254
(.010)
1.10
(.043)
MAX
0.22 – 0.38
(.009 – .015) 0.13 ± 0.05
(.005 ± .002)
0.86
(.34)
REF
0.65
(.0256)
BCS
0° – 6° TYP
DETAIL “A”
DETAIL “A”
GAUGE PLANE
12
34
4.88 ± 0.1
(.192 ± .004)
8765
3.00 ± 0.102
(.118 ± .004)
(NOTE 3)
3.00 ± 0.102
(.118 ± .004)
NOTE 4
0.52
(.206)
REF
5.23
(.206)
MIN
3.2 – 3.45
(.126 – .136)
0.889 ± 0.127
(.035 ± .005)
RECOMMENDED SOLDER PAD LAYOUT
0.42 ± 0.04
(.0165 ± .0015)
TYP
0.65
(.0256)
BSC
11
LTC1731-8.2/LTC1731-8.4
sn1731 17318fs
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-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
PACKAGE DESCRIPTION
U
0.016 – 0.050
(0.406 – 1.270)
0.010 – 0.020
(0.254 – 0.508)× 45°
0°– 8° TYP
0.008 – 0.010
(0.203 – 0.254)
SO8 1298
0.053 – 0.069
(1.346 – 1.752)
0.014 – 0.019
(0.355 – 0.483)
TYP
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
1234
0.150 – 0.157**
(3.810 – 3.988)
8765
0.189 – 0.197*
(4.801 – 5.004)
0.228 – 0.244
(5.791 – 6.197)
DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
*
**
12
LTC1731-8.2/LTC1731-8.4
sn1731 17318fs
LT/TP 0602 2K • PRINTED IN USA
PART NUMBER DESCRIPTION COMMENTS
LT®1510-5 500kHz Constant-Voltage/Constant-Current Battery Charger Most Compact, Up to 1.5A, Charges NiCd, NiMH, Li-Ion Cells
LT1512 SEPIC Battery Charger V
IN
Can Be Higher or Lower Than Battery Voltage, 1.5A Switch
LT1571-1/-2/-5 200kHz/500kHz 1.5A Constant-Current/Constant-Voltage Charges 1- or 2-Cell Li-Ion Batteries, Preset and Adjustable
Battery Charger Battery Voltages, C/10 Charge Detection
LTC1615 SOT-23 Step-Up Switching Regulator 1.2V ≤ V
IN
≤ 15V; Up to 34 Output; I
Q
= 20µA
LT1620 Rail-to-Rail Current Sense Amplifier Precise Output Current Programming, Up to 32V V
OUT
LTC1682 Low Noise Doubler Charge Pump Output Noise = 60µV
RMS
; 2.5V to 5.5V Output
LTC1729 Termination Controller for Li-Ion Time or Charge Current Termination, Automatic Charger/Battery
Detection, Status Output, Preconditioning, 8-Lead MSOP
LTC1730 Complete Li-Ion Pulse Battery Charger with Internal FET Efficient 1.5A Charger with Many Features Including
and Thermal Regulation Overcurrent Battery Protection
LTC1731-4.1/-4.2 Complete Li-Ion Linear Battery Charger Controller Single Cell Li-Ion; C/10 Detection; Complete Charger
LTC1732 Complete Li-Ion Linear Battery Charger Controller No Firmware Required; AC Adapter Indicator
Automatic Charge and Recharge
LTC1733 Complete Li-Ion Linear Battery Charger with Internal FET 1.5A Charger with Many Features Including Thermal Feedback for
Increased Charge Current without Exceeding Maximum
Temperature
LTC1734 ThinSOT Li-Ion Charger Only Two External Components; V
PROG
Tracks I
CHARGE
No Diode Needed, No Sense Resistor Needed
LTC1754 ThinSOT Charge Pump I
OUT
= 50mA; 2V ≤ V
IN
≤ 4.4V; for Backlight White LED
LTC4050 Complete Li-Ion Charger with Thermistor Interface No Firmware required, AC Adapter Indicator
Automatic Charge and Recharge
RELATED PARTS
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear-tech.com
© LINEAR TECHNOLOGY CORPORATION 2000
Linear Charger Using a PNP Transistor
U
TYPICAL APPLICATIO
V
CC
V
IN
= 9V
SENSE
DRV
R2
2k R
SENSE
0.25Ω
R1
10k
R
PROG
19.6k 2-CELL
Li-ION
LTC1731-8.4
BAT
CHRG
8
7
MBRM120T3
C2
10µF
C1
1nF
1731 TA02
C3
1µF
I
BAT
= 400mA
C
TIMER
*
0.1µF
Q1
2N5087
6
1
5
4
2
3TIMER
PROG
GND
Q2
ZTX749
*AVX 0603ZC104KAT1A
+
CHARGE
STATUS
