1
LTC1731-4.1/LTC1731-4.2
Single Cell Lithium-Ion Linear
Battery Charger Controllers
The LTC
®
1731 is a complete constant-current/constant-
voltage linear charger controller for single cell lithium-ion
batteries. Nickel-cadmium (NiCd) and nickel-metal-hy-
dride (NiMH) batteries can also be charged with constant
current using external termination. The external sense
resistor sets the charge current with 5% accuracy. An
internal resistor divider and precision reference set the
final float potential with ±1% accuracy. The output float
voltage is set internally to 4.1V (LTC1731-4.1) or 4.2V
(LTC1731-4.2).
When the input supply is removed, the LTC1731 automati-
cally enters a low current sleep mode, dropping the battery
drain current to typically 7µA. An internal comparator
detects the end-of-charge (C/10) condition while a pro-
grammable 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 LTC1731 is available in the 8-pin MSOP and SO
packages.
■
Complete Linear Charger Controller for
1-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 (7µA 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.
V
CC
V
IN
= 6V
SENSE
DRV
1k R
SENSE
0.2Ω
R
PROG
*
19.6k Li-ION
CELL
LTC1731-4.2
*SHUTDOWN INVOKED BY FLOATING THE PROG PIN
BAT
CHRG
8
7
MBRM120T3
10µF
1731 TA01
1µF
I
BAT
= 500mA
C
TIMER
0.1µF
CHARGE
STATUS Q1
Si9430DY
6
1
5
4
+
2
3TIMER
PROG
GND
500mA Li-Ion Battery Charger
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
2
LTC1731-4.1/LTC1731-4.2
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
CC
Input Supply Voltage ●4.5 12 V
I
CC
Input Supply Current Charger On, Current Mode ●13 mA
Shutdown Mode ●12 mA
Sleep Mode (Battery Drain Current) 7 20 µA
V
BAT
Regulated Output Voltage LTC1731-4.1 (5V ≤ V
CC
≤ 12V) ●4.059 4.1 4.141 V
LTC1731-4.2 (5V ≤ V
CC
≤ 12V) ●4.158 4.2 4.242 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●415 585 mA
R
PROG
= 97.6k, R
SENSE
= 0.2Ω70 100 130 mA
I
TRIKL
Trickle Charge Current V
BAT
= 2V, R
PROG
= 19.6k, I
TRIKL
= (V
CC
– V
SENSE
)/0.2Ω●30 50 100 mA
V
TRIKL
Trickle Charge Threshold Voltage From Low to High ●2.35 2.457 2.55 V
V
UV
V
CC
Undervoltage Lockout Voltage From Low to High ●4.1 4.5 V
∆V
UV
V
CC
Undervoltage Lockout Hysteresis 200 mV
V
MSD
Manual Shutdown Threshold Voltage PROG Pin Low to High 2.457 V
PROG Pin High to Low 2.446 V
ORDER PART
NUMBER
(Note 1)
Input Supply Voltage (V
CC
) ................................... 13.2V
Input Voltage (SENSE, DRV, BAT,
TIMER, PROG) .................................. –0.3V to 13.2V
Output Voltage (CHRG) ......................... –0.3V to 13.2V
LTC1731EMS8-4.1
LTC1731EMS8-4.2
T
JMAX
= 150°C, θ
JA
= 200°C/W
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
LTJK
LTKQ
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
LTC1731ES8-4.1
LTC1731ES8-4.2
S8 PART MARKING
173141
173142
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 6V 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
Consult factory for parts specified with wider operating temperature ranges.
3
LTC1731-4.1/LTC1731-4.2
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
) High to Low 30 54 90 mV
(V
CC
– V
BAT
) Low to High 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
= 0.1µF10%
V
CLAMP
DRV Pin Clamp Voltage V
CLAMP
= V
CC
– V
DRV
, I
DRIVE
= 50µA 6.5 V
ELECTRICAL CHARACTERISTICS
Note 2: The LTC1731E 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. Guaranteed I grade parts are available,
consult factory.
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 6V unless otherwise noted.
TYPICAL PERFOR A CE CHARACTERISTICS
UW
Trickle Charge Current
vs Input Supply
V
CC
(V)
4
I
TRKL
(mA)
50
55
12
1731 G01
45
40 6810
60 R
PROG
= 19.6k
R
SENSE
= 0.2Ω
V
BAT
= 2V
T
A
= 25°C
TEMPERATURE (°C)
–50 –25 25
V
PROG
(V)
2.460
2.465
150
1731 G02
2.455
2.450 050 75 100 125
2.470 V
CC
= 6V
R
PROG
= 19.6k
TEMPERATURE (°C)
–50 –25 25
t
TIMER
(%)
100
105
150
1731 G03
95
90 050 75 100 125
110 V
CC
= 6V
C
TIMER
= 0.1µF
Program Pin Voltage
vs Temperature Timer Accuracy vs Temperature
4
LTC1731-4.1/LTC1731-4.2
TYPICAL PERFOR A CE CHARACTERISTICS
UW
Trickle Charge Threshold Voltage
vs Temperature Timer Accuracy vs Input Supply Trickle Charge Current
vs Temperature
TEMPERATURE (°C)
–50 –25 25
V
TRKL
(V)
2.460
2.465
150
1731 G04
2.455
2.450 050 75 100 125
2.470 V
CC
= 6V
V
CC
(V)
4
t
TIMER
(%)
100
105
12
1731 G05
95
90 6810
110 V
BAT
= 3V
C
TIMER
= 0.1µF
T
A
= 25°C
TEMPERATURE (°C)
–50 –25 25
I
TRKL
(mA)
50
55
150
1731 G06
45
40 050 75 100 125
60 R
PROG
= 19.6k
R
SENSE
= 0.2Ω
V
BAT
= 2V
V
CC
= 6V
Battery Charge Current
vs Temperature
TEMPERATURE (°C)
–50 –25 25
I
BAT
(mA)
500
510
520
530
150
1731 G07
480
490
460
470
050 75 100 125
540 R
PROG
= 19.6k
R
SENSE
= 0.2Ω
V
BAT
= 3V
V
CC
= 6V
Trickle Charge Threshold Voltage
vs Input Supply
V
CC
(V)
4
V
TRKL
(V)
2.460
2.465
2.470
2.475
12
1731 G08
2.450
2.455
2.440
2.445
6810
2.480 R
PROG
= 19.6k
T
A
= 25°C
Program Pin Voltage
vs Input Supply Battery Charge Current
vs Input Supply
V
CC
(V)
4
V
PROG
(V)
2.460
2.465
2.470
2.475
12
1731 G09
2.450
2.455
2.440
2.445
6810
2.480 R
PROG
= 19.6k
V
BAT
= 3V
T
A
= 25°C
V
CC
(V)
4
I
BAT
(mA)
500
505
510
515
12
1731 G10
490
495
480
485
6810
520 R
PROG
= 19.6k
R
SENSE
= 0.2Ω
V
BAT
= 3V
T
A
= 25°C
5
LTC1731-4.1/LTC1731-4.2
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 resistor
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. 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 constant-voltage mode and the
timer are disabled, the chip will operate in constant-
current mode only. Short the TIMER pin to GND to disable
the internal timer function and the C/10 function.
GND (Pin 4): Ground Connection.
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. An internal 2.5µA
current source will pull the pin above the shutdown
threshold voltage when the program resistor (R
PROG
) is
disconnected.
DRV (Pin 6): Drive Output Pin for the P-Channel MOSFET
or PNP Transistor. The impedance is high at this pin,
therefore, a high beta PNP pass transistor should be used.
The DRV pin is internally clamped to 6.5V below V
CC
.
V
CC
(Pin 7): Positive Input Supply Voltage. When V
BAT
is
within 54mV of V
CC
, the LTC1731 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 8): 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
)
6
LTC1731-4.1/LTC1731-4.2
BLOCK DIAGRA
W
–
+
–
+
–
+
–
+
LOGIC
C1
–
+
C4
–
+
–
+
C3 A1
CA
C2
VA
CHARGE
GND
1731 BD
PROG
BATTERY CURRENT IBAT = (2.457V • 800Ω)/(RPROG • RSENSE)RPROG
VREF
2.457V
LBO
80Ω
VCC
800Ω54mV
RSENSE
SENSE
DRV
BAT
720Ω
100µA
TIMER OSCILLATOR
VREF
COUNTER
STOP
SHDN SLP
C/10 C/10
2.5µA
VCC
CHRG
4
5
2
3
8
7
6
1
+
–
7
LTC1731-4.1/LTC1731-4.2
OPERATIO
U
The LTC1731 is a linear battery charger controller for
single cell lithium-ion batteries. 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
) between the V
CC
and SENSE pins. R
PROG
sets a
program current through an internal trimmed 800Ω resis-
tor setting up 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
current 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 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 be terminated.
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 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 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.
An external capacitor on the TIMER pin sets the total
charge time. After a time-out occurs, the charging will be
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
momentarily.
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
LTC1731 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 7µA. This
greatly reduces the current drain on the battery and
increases the standby time.
APPLICATIONS INFORMATION
WUUU
Charge Termination
The charger is off when any of the following conditions
exist: the voltage at the V
CC
pin is below 4.1V, the voltage
at the V
CC
pin is higher than 4.1V but is less than 54mV
above V
BAT
, or the PROG pin is floating. The DRV pin will
be pulled to V
CC
and the internal resistor divider is discon-
nected 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 4.1V. To prevent oscillation around
V
CC
= 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 low (below 2.457V) the charger goes into trickle
charge mode. The charge current is set to 10% of the full-
scale current. If the low cell 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 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
8
LTC1731-4.1/LTC1731-4.2
pull-up resistors, a microprocessor can detect three states
from this pin (charging, C/10 and stop charging). See
Figure 1.
When the LTC1731 is in charge mode, the CHRG pin is
pulled down 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 resis-
tor. 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. The
IN pin will then be pulled high by the 2k pull-up. 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 state and the 100k resistor will
then pull the pin high to indicate the charging has stopped.
Refer to Table 1 for the summary.
Table 1. CHRG Pin Interface with Microprocessor
IN OUT STATUS
Low High Charging
Low Hi-Z Charging
High High C/10
Low Hi-Z C/10
High Hi-Z Stop Charging
End of Charge (C/10)
The LTC1731 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 compara-
tor trips and turns off the N-channel MOSFET at the CHRG
pin and switches in a 100µA current source to ground.
APPLICATIONS INFORMATION
WUUU
2k
100k
CHRG
1731 F01
V
CC
LTC1731
V
+
V
DD
OUT
µPROCESSOR
IN
2
7
Figure 1. Microprocessor Interface
voltage. The DRV pin will then be pulled up to V
CC
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:
I
BAT
= (I
PROG
)(800Ω/R
SENSE
)
= (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
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 = (3 Hours)(C
TIMER
/0.1µF)
The timer starts when the 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 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 down
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 100µA 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
9
LTC1731-4.1/LTC1731-4.2
APPLICATIONS INFORMATION
WUUU
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 dis-
abled in trickle charge mode.
Gate Drive
Typically the LTC1731 controls 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.
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 R
PROG
=
19.6k (100mV across R
SENSE
), it represents 1.67% of
error in charging current.
Constant-Current Only Mode
The LTC1731 can be used as a programmable current
source by forcing the TIMER pin to V
CC
. This is particularly
useful for charging NiMH or NiCd batteries. In the con-
stant-current only mode, the timer and voltage amplifier
are both disabled. An external termination 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.
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.
V
CC
V
IN
= 6V
SENSE
DRV
4.7k
1k 2.2k 1k
AMBER
1.5k
20k R
SENSE
0.2Ω
R
PROG
19.6k Li-ION
CELL
LTC1731-4.2
BAT
CHRG
8
7
10µF
1µF
1731 TA04
0.1µF
Si9430DY
6
1
5
4
+
2
3TIMER
PROG
GND
GREEN
MMBT3906
MMSD4148
MBRM120T3
OPTIONAL: FOR REVERSE
INPUT PROTECTION
MMBT3906
CONDITION
NO WALL ADAPTER
CHARGING (I > C/10)
CHARGING (I < C/10)
TIMER EXPIRED
GREEN
OFF
OFF
ON
ON
AMBER
OFF
ON
OFF
OFF
Using CHRG Pin to Indicate Charge Status
U
TYPICAL APPLICATIO
10
LTC1731-4.1/LTC1731-4.2
Dimensions in inches (millimeters) unless otherwise noted.
U
PACKAGE DESCRIPTIO
MS8 Package
8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
MSOP (MS8) 1100
* 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
0.021 ± 0.006
(0.53 ± 0.015)
0° – 6° TYP
SEATING
PLANE
0.007
(0.18)
0.043
(1.10)
MAX
0.009 – 0.015
(0.22 – 0.38) 0.005 ± 0.002
(0.13 ± 0.05)
0.034
(0.86)
REF
0.0256
(0.65)
BSC
12
34
0.193 ± 0.006
(4.90 ± 0.15)
8765
0.118 ± 0.004*
(3.00 ± 0.102)
0.118 ± 0.004**
(3.00 ± 0.102)
11
LTC1731-4.1/LTC1731-4.2
Dimensions in inches (millimeters) unless otherwise noted.
U
PACKAGE DESCRIPTIO
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 0.150)
(LTC DWG # 05-08-1610)
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
LTC1731-4.1/LTC1731-4.2
1731f LT/TP 0301 4K • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATIO N 1999
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear-tech.com
PART NUMBER DESCRIPTION COMMENTS
LT®1510-5 500kHz Constant-Voltage/Constant-Current Most Compact, Up to 1.5A, Charges NiCd, NiMH, Li-Ion Cells
Battery Charger
LT1512 SEPIC Battery Charger V
IN
Can Be Higher or Lower Than Battery Voltage, 1.5A Switch
LT1571-1/LT1571-2 200kHz/500kHz Constant-Current/Constant-Voltage Up to 1.5A Charge Current for 1- or 2-Cell Li-Ion Batteries, Preset and
LT1571-5 Battery Charger Family Adjustable Battery Voltages, C/10 Charge Detection
LT1620/LT1621 Rail-to-Rail Current Sense Amplifier Precise Output Current Programming, Up to 32V V
OUT
LTC1730 Integrated Pulse Charger for 1-Cell Li-Ion Battery 0.35Ω Internal N-FET Requires No Blocking Diode
LTC1729 Termination Controller for Li-Ion Time or Charge Current Termination, Automatic Charger/Battery
Detection, Status Output, Preconditioning, 8-Lead MSOP
LTC1732 Constant-Current/Constant-Voltage Li-Ion Linear Stand Alone Battery, No µC or Firmware Required, Auto Recharge of
Battery Charger Low Battery, 10-Pin MSOP, Input Supply Detection
LTC1734 SOT-23 Li-Ion Battery Charger Needs Only Two External Components, Monitors Charge Current, No
Reverse Diode or Sense Resistor Required
RELATED PARTS
1.5A Single Cell Switching Battery Charger
V
CC
SENSE
DRV
R5
1k R3
0.082Ω
1/4W
R2
4.7Ω
Li-ION
BATTERY
R4
18.2k
1%
+
LTC1731-4.2
BAT
CHRG
8
7
C3
100µF
1731 TA03
C2
22µF
CER
C1*
0.1µF
Q2
Si2305DS
D1
MBRS130LT3
22µH
CDRH6D38-220NC
D2
MBRS130LT3
V
IN
5V TO 6V
6
LTC1693-5
1
*AVX 0603ZC104KAT1A
45
2
3TIMER
GND PROG
C4
0.47µF
C5
1µF
CER
+
V
CC
V
IN
= 6V
SENSE
DRV
R2
1k R
SENSE
0.2Ω
R1
10k
R
PROG
19.6k Li-ION
CELL
LTC1731-4.2
BAT
CHRG
8
7
MBRM120T3
C2
10µF
C1
1nF
1731 TA02
C3
1µF
I
BAT
= 500mA
+
C
TIMER
0.1µF
Q1
2N5087
6
1
5
4
2
3TIMER
PROG
GND
Q2
ZTX749
Linear Charger Using a PNP Transistor
TYPICAL APPLICATIO S
U
