LTC1734
Lithium-Ion Linear
Battery Charger in ThinSOT
FEATURES
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DESCRIPTIO
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Low Profile (1mm) ThinSOT
TM
Package
No Blocking Diode Required
No Sense Resistor Required
1% Accurate Preset Voltages: 4.1V or 4.2V
Charge Current Monitor Output
for Charge Termination
Programmable Charge Current: 200mA to 700mA
Automatic Sleep Mode with Input Supply Removal
Manual Shutdown
Negligible Battery Drain Current in Shutdown
Undervoltage Lockout
Self Protection for Overcurrent/Overtemperature
The LTC
®
1734 is a low cost, single cell, constant-current/
constant-voltage Li-Ion battery charger controller. When
combined with a few external components, the SOT-23
package forms a very small, low cost charger for single cell
lithium-ion batteries.
The LTC1734 is available in 4.1V and 4.2V versions with
1% accuracy. Constant current is programmed using a
single external resistor between the PROG pin and ground.
Manual shutdown is accomplished by floating the pro-
gram resistor while removing input power automatically
puts the LTC1734 into a sleep mode. Both the shutdown
and sleep modes drain near zero current from the battery.
Charge current can be monitored via the voltage on the
PROG pin allowing a microcontroller or ADC to read the
current and determine when to terminate the charge cycle.
The output driver is both current limited and thermally
protected to prevent the LTC1734 from operating outside
of safe limits. No external blocking diode is required.
The LTC1734 can also function as a general purpose
current source or as a current source for charging nickel-
cadmium (NiCd) and nickel-metal-hydride (NiMH) batter-
ies using external termination.
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
APPLICATIO S
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Cellular Telephones
Handheld Computers
Digital Cameras
Charging Docks and Cradles
Low Cost and Small Size Chargers
Programmable Current Sources
TYPICAL APPLICATIO
PROG Pin Indicates Charge Status
5V
V
BAT
(V)
300mA Li-Ion Battery Charger
V
IN
5V
1µF
3
2
4
R
PROG
5k
V
CC
I
SENSE
1
4V
LTC1734
6
GND
DRIVE
PROG
BAT
5
3V
FMMT549
I
BAT
= 300mA
10µF
V
PROG
(V)
2V
1.5V
1V
CONSTANT
CURRENT
V
PROG
+
SINGLE
Li-Ion
BATTERY
1734 TA01
0V
CHARGING
BEGINS
U
V
BAT
CONSTANT
VOLTAGE
CHARGING
COMPLETE
1734 TA01b
U
U
1
LTC1734
ABSOLUTE
MAXIMUM
RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
ORDER PART
NUMBER
TOP VIEW
I
SENSE
1
GND 2
V
CC
3
6 DRIVE
5 BAT
4 PROG
Supply Voltage (V
CC
) ...................................– 0.3V to 9V
Input Voltage (BAT, PROG) ........ – 0.3V to (V
CC
+ 0.3V)
Output Voltage (DRIVE) .............. – 0.3V to (V
CC
+ 0.3V)
Output Current (I
SENSE
) ................................... – 900mA
Short-Circuit Duration (DRIVE) ...................... Indefinite
Junction Temperature .......................................... 125°C
Operating Ambient Temperature Range
(Note 2) ...............................................–40°C to 85°C
Operating Junction Temperature (Note 2) ............ 100°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
LTC1734ES6-4.1
LTC1734ES6-4.2
S6 PART MARKING
LTHD
LTRG
S6 PACKAGE
6-LEAD PLASTIC SOT-23
T
JMAX
= 125°C,
θ
JA
= 230°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 5V, GND = 0V and V
BAT
is equal to the float voltage unless
otherwise noted. All current into a pin is positive and current out of a pin is negative. All voltages are referenced to GND, unless
otherwise specified.
SYMBOL
V
CC
Supply
V
CC
I
CC
I
SHDN
I
BMS
I
BSL
V
UVLOI
V
UVLOD
V
UVHYS
V
BAT
I
BAT1
I
BAT2
V
CM1
Operating Supply Range (Note 5)
Quiescent V
CC
Pin Supply Current
V
CC
Pin Supply Current in Manual Shutdown
Battery Drain Current in Manual Shutdown
(Note 3)
Battery Drain Current in Sleep Mode (Note 4)
Undervoltage Lockout Exit Threshold
Undervoltage Lockout Entry Threshold
Undervoltage Lockout Hysteresis
Output Float Voltage in Constant Voltage Mode
Output Full-Scale Current When Programmed
for 200mA in Constant Current Mode
Output Full-Scale Current When Programmed
for 700mA in Constant Current Mode
Current Monitor Voltage on PROG Pin
V
BAT
= 5V, (Forces I
DRIVE
= I
BAT
= 0),
I
PROG
= 200µA,(7500Ω from PROG to GND)
PROG Pin Open
PROG Pin Open
V
CC
= 0V
V
CC
Increasing
V
CC
Decreasing
V
CC
Decreasing
4.1V Version, I
BAT
= 10mA, 4.55V
≤
V
CC
≤
8V
4.2V Version, I
BAT
= 10mA, 4.55V
≤
V
CC
≤
8V
R
PROG
= 7500Ω, 4.55V
≤
V
CC
≤
8V,
Pass PNP Beta > 50
R
PROG
= 2143Ω, 4.55V
≤
V
CC
≤
8V,
Pass PNP Beta > 50
I
BAT
= 10% of I
BAT1
, R
PROG
= 7500Ω,
4.55V
≤
V
CC
≤
8V, Pass PNP Beta > 50,
0°C
≤
T
A
≤
85°C
I
BAT
= 10% of I
BAT2
, R
PROG
= 2143Ω,
4.55V
≤
V
CC
≤
8V, Pass PNP Beta > 50,
0°C
≤
T
A
≤
85°C
V
DRIVE
= 3.5V
q
q
q
q
q
q
q
q
q
q
q
q
ELECTRICAL CHARACTERISTICS
PARAMETER
CONDITIONS
MIN
4.55
TYP
MAX
8
UNITS
V
µA
µA
µA
µA
V
V
mV
670
450
–1
–1
4.45
4.30
0
0
4.56
4.41
150
4.059
4.158
155
620
0.045
4.10
4.20
200
700
0.15
1150
900
1
1
4.68
4.53
Charging Performance
4.141
4.242
240
770
0.28
V
V
mA
mA
V
V
CM2
Current Monitor Voltage on PROG Pin
0.10
0.15
0.20
I
DSINK
Drive Output Current
30
2
U
W
U
U
W W
W
V
mA
LTC1734
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 5V, GND = 0V and V
BAT
is equal to the float voltage unless
otherwise noted. All current into a pin is positive and current out of a pin is negative. All voltages are referenced to GND, unless
otherwise specified.
SYMBOL
V
MSDT
V
MSHYS
I
PROGPU
Protection
I
DSHRT
Drive Output Short-Circuit Current Limit
V
DRIVE
= V
CC
q
ELECTRICAL CHARACTERISTICS
PARAMETER
Manual Shutdown Threshold
Manual Shutdown Hysteresis
Programming Pin Pull-Up Current
CONDITIONS
V
PROG
Increasing
V
PROG
Decreasing from V
MSDT
V
PROG
= 2.5V
q
MIN
2.05
–6
35
TYP
2.15
90
–3
65
MAX
2.25
– 1.5
130
UNITS
V
mV
µA
mA
Charger Manual Control
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
The LTC1734E is guaranteed to meet performance specifications
from 0°C to 70°C ambient temperature range and 0°C to 100°C junction
temperature range. Specifications over the – 40°C to 85°C operating
ambient temperature range are assured by design, characterization and
correlation with statistical process controls.
Note 3:
Assumes that the external PNP pass transistor has negligible B-C
reverse-leakage current when the collector is biased at 4.2V (V
BAT
) and the
base is biased at 5V (V
CC
).
Note 4:
Assumes that the external PNP pass transistor has negligible B-E
reverse-leakage current when the emitter is biased at 0V (V
CC
) and the
base is biased at 4.2V (V
BAT
).
Note 5:
The 4.68V maximum undervoltage lockout (UVLO) exit threshold
must first be exceeded before the minimum V
CC
specification applies.
Short duration drops below the minimum V
CC
specification of several
microseconds or less are ignored by the UVLO. If manual shutdown is
entered, then V
CC
must be higher than the 4.68V maximum UVLO
threshold before manual shutdown can be exited. When operating near the
minimum V
CC
, a suitable PNP transistor with a low saturation voltage
must be used.
TYPICAL PERFOR A CE CHARACTERISTICS
Float Voltage vs Temperature
and Supply Voltage
4.21
I
BAT
= 10mA
PNP = FCX589
4.2V OPTION
4.201
FLOAT VOLTAGE (V)
FLOAT VOLTAGE (V)
4.20
V
CC
= 8V
V
CC
= 4.55V
4.200
I
BAT1
(mA)
4.19
–50 –25
50
25
0
75
TEMPERATURE (°C)
U W
100
1734 G01
Float Voltage vs I
BAT
V
CC
= 5V
T
A
= 25°C
PNP = FCX589
4.2V OPTION
R
PROG
= 2150Ω
210
I
BAT1
vs Temperature
and Supply Voltage
R
PROG
= 7.5k
PNP = FCX589
200
V
CC
= 4.55V AND 8V
125
4.199
0
100
200
300 400
I
BAT
(mA)
500
600
700
190
–50 –25
50
25
0
75
TEMPERATURE (°C)
100
125
1734 G02
1734 G03
3
LTC1734
TYPICAL PERFOR A CE CHARACTERISTICS
I
BAT2
vs Temperature
and Supply Voltage
740
R
PROG
= 2.15k
PNP = FCX589
I
BAT1
(mA)
I
BAT2
(mA)
700
V
CC
= 4.55V AND 8V
200
BAT PIN MUST BE DISCONNECTED
AND GROUNDED TO FORCE
CC MODE IN THIS REGION
I
BAT2
(mA)
660
–50 –25
50
25
0
75
TEMPERATURE (°C)
Program Pin Pull-Up Current vs
Temperature and Supply Voltage
3.6
3.5
V
CC
= 8V
I
PROGPU
(µA)
I
PROGPU
(µA)
3.6
V
PROG
= 2.5V
3.4
3.4
3.3
V
CC
= 4.55V
3.2
3.1
3.0
–50 –25
V
PROG
(V)
50
25
75
0
TEMPERATURE (°C)
Program Pin Voltage
vs Charge Current (700mA)
1.6
V
CC
= 5V
T
A
= 25°C
1.4
R
PROG
= 2.15k
PNP = FCX589
1.2
160
V
PROG
(mV)
0.8
0.6
0.4
0.2
0
0
100
200
300 400
I
BAT2
(mA)
500
600
700
LIMITS AT 6mV DUE TO
PROGRAMMING PIN PULL-UP
CURRENT (I
PROGPU
)
150
V
CC
= 8V
V
PROG
(mV)
V
PROG
(V)
1.0
4
U W
100
1734 G04
I
BAT1
vs V
BAT
210
V
CC
= 5V
T
A
= 25°C
R
PROG
= 7.5k
PNP = FCX589
750
I
BAT2
vs V
BAT
V
CC
= 5V
T
A
= 25°C
R
PROG
= 2.15k
PNP = FCX589
700
BAT PIN MUST BE DISCONNECTED
AND GROUNDED TO FORCE
CC MODE IN THIS REGION
125
190
0
1
3
2
V
BAT
(V)
4
5
1734 G05
650
0
1
3
2
V
BAT
(V)
4
5
1734 G06
Program Pin Pull-Up Current
vs V
PROG
V
CC
= 8V
T
A
= 25°C
1.6
Program Pin Voltage
vs Charge Current (200mA)
V
CC
= 5V
T
A
= 25°C
1.4
R
PROG
= 7.5k
PNP = FCX589
1.2
1.0
0.8
0.6
0.4
LIMITS AT 25mV DUE TO
PROGRAMMING PIN PULL-UP
CURRENT (I
PROGPU
)
0
50
100
I
BAT1
(mA)
1635 G08
1734 F09
3.2
3.0
2.8
0.2
2.6
100
125
2
3
4
5
V
PROG
(V)
6
7
8
0
150
200
1734 G07
Program Pin Voltage for I
BAT1
/10
vs Temperature and Supply Voltage
R
PROG
= 7.5k
PNP = FCX589
160
Program Pin Voltage for I
BAT2
/10
vs Temperature and Supply Voltage
R
PROG
= 2.15k
PNP = FCX589
V
CC
= 8V
150
V
CC
= 4.55V
V
CC
= 4.55V
140
–50 –25
50
25
0
75
TEMPERATURE (°C)
100
125
140
–50 –25
50
25
0
75
TEMPERATURE (°C)
100
125
1734 G10
1734 G11
1734 G12
LTC1734
PIN FUNCTIONS
I
SENSE
(Pin 1):
Sense Node for Charge Current. Current
from V
CC
passes through the internal current sense resis-
tor and reappears at I
SENSE
to supply current to the
external PNP emitter. The PNP collector provides charge
current to the battery.
GND (Pin 2):
Ground. Provides a reference for the internal
voltage regulator and a return for all internal circuits.
When in the constant voltage mode, the LTC1734 will
precisely regulate the voltage between the BAT and GND
pins. The battery ground should connect close to the GND
pin to avoid voltage drop errors.
V
CC
(Pin 3):
Positive Input Supply Voltage. This pin
supplies power to the internal control circuitry and exter-
nal PNP transistor through the internal current sense
resistor. This pin should be bypassed to ground with a
capacitor in the range of 1µF to 10µF.
PROG (Pin 4):
Charge Current Programming, Charge
Current Monitor and Manual Shutdown Pin. Provides a
virtual reference voltage of 1.5V for an external resistor
(R
PROG
) tied between this pin and ground that programs
the battery charge current when the charger is in the
constant current mode. The typical charge current will be
1000 times greater than the current through this resistor
(I
BAT
= 1500/R
PROG
). This pin also allows for the charge
current to be monitored. The voltage on this pin is propor-
tional to the charge current where 1.5V corresponds to the
full programmed currrent. Floating this pin allows an
internal current source to pull the pin voltage above the
shutdown threshold voltage. Because this pin is in a signal
path, excessive capacitive loading can cause AC instabil-
ity. See the Applications Information section for more
details.
BAT (Pin 5):
Battery Voltage Sense Input. A precision
internal resistor divider sets the final float voltage on this
pin. This divider is disconnected in the manual shutdown
or sleep mode. When charging, approximately 34µA
flows into the BAT pin. To minimize float voltage errors,
avoid excessive resistance between the battery and the
BAT pin. For dynamically stable operation, this pin usually
requires a minimum bypass capacitance to ground of 5µF
to frequency compensate for the high frequency inductive
effects of the battery and wiring.
DRIVE (Pin 6):
Base Drive Output for the External PNP
Pass Transistor. Provides a controlled sink current that
drives the base of the PNP. This pin has current limiting
protection for the LTC1734.
BLOCK DIAGRA
VOLTAGE
REFERENCE
2.5V
UVLO
2.15V
+
SHUTDOWN
–
3µA
W
U
U
U
V
IN
1µF
3
V
CC
I
BAT
/1000
60Ω
I
BAT
0.06Ω
1
SHUTDOWN
I
SENSE
REF
–
A3
+
OUTPUT
DRIVER
TEMPERATURE AND
CURRENT LIMITING
6
DRIVE
SHUTDOWN
I
BAT
BAT
5
10µF
SINGLE
Li-Ion
CELL
C1
1.5V
+
A2
A1
+
–
2.5V
–
SHUTDOWN
4
2
1734 BD
PROG
R
PROG
GND
5
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