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LTC1731-4.1/LTC1731-4.2 Single Cell Lithium-Ion Linear Battery Charger Controllers
FEATURES
s s s s s s s
DESCRIPTIO
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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 (7A Battery Drain) Automatic Trickle Charging of Low Voltage Cells Programmable for Constant-Current-Only Mode
The LTC (R)1731 is a complete constant-current/constantvoltage linear charger controller for single cell lithium-ion batteries. Nickel-cadmium (NiCd) and nickel-metal-hydride (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 automatically enters a low current sleep mode, dropping the battery drain current to typically 7A. 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 LTC1731 is available in the 8-pin MSOP and SO packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
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Cellular Phones Handheld Computers Charging Docks and Cradles Programmable Current Source
TYPICAL APPLICATIO
500mA Li-Ion Battery Charger
VIN = 6V MBRM120T3 7 1k CHARGE STATUS VCC SENSE 2 CHRG DRV 8 6 RSENSE 0.2 Q1 Si9430DY IBAT = 500mA
LTC1731-4.2 3 CTIMER 0.1F TIMER BAT PROG GND 4 1 5 RPROG* 19.6k
+ Li-ION
CELL
*SHUTDOWN INVOKED BY FLOATING THE PROG PIN
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1F 10F
1731 TA01
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LTC1731-4.1/LTC1731-4.2
ABSOLUTE MAXIMUM RATINGS
Input Supply Voltage (VCC) ................................... 13.2V Input Voltage (SENSE, DRV, BAT, TIMER, PROG) .................................. - 0.3V to 13.2V Output Voltage (CHRG) ......................... - 0.3V to 13.2V
PACKAGE/ORDER INFORMATION
TOP VIEW BAT CHRG TIMER GND 1 2 3 4 8 7 6 5 SENSE VCC DRV PROG
ORDER PART NUMBER
BAT 1
LTC1731EMS8-4.1 LTC1731EMS8-4.2 MS8 PART MARKING LTJK LTKQ
MS8 PACKAGE 8-LEAD PLASTIC MSOP
TJMAX = 150C, JA = 200C/W
Consult factory 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 TA = 25C. VCC = 6V unless otherwise noted.
SYMBOL VCC ICC PARAMETER Input Supply Voltage Input Supply Current Charger On, Current Mode Shutdown Mode Sleep Mode (Battery Drain Current) LTC1731-4.1 (5V VCC 12V) LTC1731-4.2 (5V VCC 12V) RPROG = 19.6k, RSENSE = 0.2 RPROG = 19.6k, RSENSE = 0.2 RPROG = 97.6k, RSENSE = 0.2 VBAT = 2V, RPROG = 19.6k, ITRIKL = (VCC - VSENSE)/0.2 From Low to High From Low to High PROG Pin Low to High PROG Pin High to Low CONDITIONS
q q q q q q q q q
ELECTRICAL CHARACTERISTICS
VBAT IBAT
Regulated Output Voltage Current Mode Charge Current
ITRIKL VTRIKL VUV VUV VMSD
Trickle Charge Current Trickle Charge Threshold Voltage VCC Undervoltage Lockout Voltage VCC Undervoltage Lockout Hysteresis Manual Shutdown Threshold Voltage
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(Note 1)
Operating Temperature Range (Note 2) .....- 40 to 85C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
TOP VIEW 8 7 6 5 SENSE VCC DRV PROG
ORDER PART NUMBER LTC1731ES8-4.1 LTC1731ES8-4.2 S8 PART MARKING 173141 173142
CHRG 2 TIMER 3 GND 4
S8 PACKAGE 8-LEAD PLASTIC SO
TJMAX = 150C, JA = 125C/W
MIN 4.5
TYP 1 1 7
MAX 12 3 2 20 4.141 4.242 535 585 130 100 2.55 4.5
UNITS V mA mA A V V mA mA mA mA V V mV V V
4.059 4.158 465 415 70 30 2.35
4.1 4.2 500 100 50 2.457 4.1 200 2.457 2.446
LTC1731-4.1/LTC1731-4.2
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 6V unless otherwise noted.
SYMBOL VASD VDIS IPROG VPROG ICHRG VCHRG IC/10 tTIMER VCLAMP PARAMETER Automatic Shutdown Threshold Voltage Voltage Mode Disable Threshold Voltage PROG Pin Current PROG Pin Load Regulation PROG Pin Voltage CHRG Pin Weak Pull-Down Current CHRG Pin Output Low Voltage End of Charge Indication Current Level TIMER Accuracy DRV Pin Clamp Voltage CONDITIONS (VCC - VBAT) High to Low (VCC - VBAT) Low to High VDIS = VCC - VTIMER Internal Pull-Up Current, No RPROG PROG Pin Source Current, VPROG 5mV RPROG =19.6k VCHRG = 1V ICHRG = 5mA RPROG = 19.6k, RSENSE = 0.2 CTIMER = 0.1F VCLAMP = VCC - VDRV, IDRIVE = 50A
q q q
ELECTRICAL CHARACTERISTICS
MIN 30 40
TYP 54 69 2.5
MAX 90 100 0.4
UNITS mV mV V A A V
300 2.457 50 25 100 0.6 50 10 6.5 150 1.2 100
A V mA % V
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
Note 2: The LTC1731E is guaranteed to meet performance specifications from 0C to 70C. Specifications over the - 40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls. Guaranteed I grade parts are available, consult factory.
TYPICAL PERFOR A CE CHARACTERISTICS
Trickle Charge Current vs Input Supply
60 RPROG = 19.6k RSENSE = 0.2 VBAT = 2V TA = 25C
VPROG (V)
55
ITRKL (mA)
50
2.460
tTIMER (%)
45
40
4
6
8 VCC (V)
10
UW
1731 G01
Program Pin Voltage vs Temperature
2.470 VCC = 6V RPROG = 19.6k 110
Timer Accuracy vs Temperature
VCC = 6V CTIMER = 0.1F
2.465
105
100
2.455
95
12
2.450 -50 -25
0
25 50 75 100 125 150 TEMPERATURE (C)
1731 G02
90 -50 -25
0
25 50 75 100 125 150 TEMPERATURE (C)
1731 G03
3
LTC1731-4.1/LTC1731-4.2 TYPICAL PERFOR A CE CHARACTERISTICS
Trickle Charge Threshold Voltage vs Temperature
2.470 VCC = 6V 110
2.465
tTIMER (%)
VTRKL (V)
2.460
100
ITRKL (mA)
2.455
2.450 -50 -25
0
25 50 75 100 125 150 TEMPERATURE (C)
1731 G04
Battery Charge Current vs Temperature
540 RPROG = 19.6k 530 RSENSE = 0.2 VBAT = 3V 520 VCC = 6V 2.480
IBAT (mA)
VTRKL (V)
510 500 490 480 470 460 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C)
1731 G07
Program Pin Voltage vs Input Supply
2.480 RPROG = 19.6k 2.475 VBAT = 3V TA = 25C 2.470
VPROG (V)
2.460 2.455 2.450 2.445 2.440 4 6 8 VCC (V)
1731 G09
IBAT (mA)
2.465
4
UW
Timer Accuracy vs Input Supply
VBAT = 3V CTIMER = 0.1F TA = 25C 60
Trickle Charge Current vs Temperature
RPROG = 19.6k RSENSE = 0.2 VBAT = 2V 55 VCC = 6V
105
50
95
45
90
4
6
8 VCC (V)
10
12
1731 G05
40 -50 -25
0
25 50 75 100 125 150 TEMPERATURE (C)
1731 G06
Trickle Charge Threshold Voltage vs Input Supply
RPROG = 19.6k 2.475 TA = 25C 2.470 2.465 2.460 2.455 2.450 2.445 2.440 4 6 8 VCC (V)
1731 G08
10
12
Battery Charge Current vs Input Supply
520 RPROG = 19.6k 515 RSENSE = 0.2 VBAT = 3V 510 TA = 25C 505 500 495 490 485 10 12 480 4 6 8 VCC (V)
1731 G10
10
12
LTC1731-4.1/LTC1731-4.2
PIN FUNCTIONS
BAT (Pin 1): Battery Sense Input. A bypass capacitor of at least 10F 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 100A 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)/(0.1F). When the TIMER pin is connected to VCC, the constant-voltage mode and the timer are disabled, the chip will operate in constantcurrent 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 connecting a resistor, RPROG to ground. The charge current is IBAT = (VPROG * 800)/(RPROG * RSENSE). The IC can be forced into shutdown by floating the PROG pin. An internal 2.5A current source will pull the pin above the shutdown threshold voltage when the program resistor (RPROG) 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 VCC. VCC (Pin 7): Positive Input Supply Voltage. When VBAT is within 54mV of VCC, the LTC1731 is forced into sleep mode, dropping ICC to 7A. VCC ranges from 4.5V to 12V. Bypass this pin with a 1F capacitor. SENSE (Pin 8): 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 * 800)/(RPROG * IBAT)
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LTC1731-4.1/LTC1731-4.2
BLOCK DIAGRA
2
CHRG
C/10 STOP C/10 100A SHDN LOGIC SLP
720
3
OSCILLATOR VREF
COUNTER
+
C3
+
A1
-
-
2.5A VREF 2.457V CHARGE PROG RPROG GND
5 BATTERY CURRENT IBAT = (2.457V * 800)/(RPROG * RSENSE)
6
+
VCC
VA
-
+
TIMER
LBO
C2
-
+
-
W
VCC 7 RSENSE
+
C1 80 800
SENSE
8
-
C4
+ - + -
CA
54mV
DRV BAT
6 1
4
1731 BD
LTC1731-4.1/LTC1731-4.2
OPERATIO
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 (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 800 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 (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 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 RSENSE and RPROG.
APPLICATIONS INFORMATION
Charge Termination 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. Shutdown The LTC1731 can be forced into shutdown by floating the PROG pin and allowing the internal 2.5A current source to pull the pin above the 2.457V shutdown threshold 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 fullscale 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.
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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 impedance 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 VCC. 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 (ICC = 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 ICC to 7A. This greatly reduces the current drain on the battery and increases the standby time.
7
LTC1731-4.1/LTC1731-4.2
APPLICATIONS INFORMATION
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)(800/RSENSE) = (2.457V/RPROG)(800/RSENSE) 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 charge current. RSENSE = 0.1V/0.5A = 0.2, then calculate: RPROG = (2.457V/500mA)(800/0.2) = 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)(CTIMER/0.1F) 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 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 100A 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
V+ 7 VCC LTC1731 CHRG 2 100k 2k OUT IN
1731 F01
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PROCESSOR
Figure 1. Microprocessor Interface
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 resistor. Once the charge current drops to 10% of the full-scale current (C/10), the N-channel MOSFET is turned off and a 100A 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 Low Low High Low High OUT High Hi-Z High Hi-Z Hi-Z STATUS Charging Charging C/10 C/10 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 comparator trips and turns off the N-channel MOSFET at the CHRG pin and switches in a 100A current source to ground.
LTC1731-4.1/LTC1731-4.2
APPLICATIONS INFORMATION
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 controls an external P-channel MOSFET to supply current to the battery. The DRV pin is internally clamped to 6.5V below VCC. 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 0.6A/mV. For every 1A 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 LTC1731 can be used as a programmable current source by forcing 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. Stability The charger is stable without any compensation when a P-channel MOSFET is used as the pass transistor. However, a 10F 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 VCC. This capacitor is needed to help stablize the voltage loop. A 10F capacitor at the BAT pin is also recommended when a battery is not present.
TYPICAL APPLICATIO
Using CHRG Pin to Indicate Charge Status
OPTIONAL: FOR REVERSE INPUT PROTECTION VIN = 6V MMSD4148 MBRM120T3 7 4.7k 2.2k 1k 2 VCC SENSE CONDITION NO WALL ADAPTER CHARGING (I > C/10) CHARGING (I < C/10) TIMER EXPIRED GREEN AMBER OFF OFF OFF ON ON OFF ON OFF 1k CHRG DRV 8 6 RSENSE 0.2 Si9430DY
MMBT3906
GREEN
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1.5k MMBT3906 20k
1F
LTC1731-4.2 3 AMBER 0.1F TIMER BAT PROG GND 4 1 5 RPROG 19.6k
+ Li-ION
CELL
10F
1731 TA04
9
LTC1731-4.1/LTC1731-4.2
PACKAGE DESCRIPTIO
0.007 (0.18) 0.021 0.006 (0.53 0.015)
* 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
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Dimensions in inches (millimeters) unless otherwise noted. MS8 Package 8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
0.118 0.004* (3.00 0.102)
8
76
5
0.193 0.006 (4.90 0.15)
0.118 0.004** (3.00 0.102)
1 0.043 (1.10) MAX 0 - 6 TYP SEATING PLANE
23
4 0.034 (0.86) REF
0.009 - 0.015 (0.22 - 0.38)
0.0256 (0.65) BSC
0.005 0.002 (0.13 0.05)
MSOP (MS8) 1100
LTC1731-4.1/LTC1731-4.2
PACKAGE DESCRIPTIO U
Dimensions in inches (millimeters) unless otherwise noted.
S8 Package 8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 - 0.197* (4.801 - 5.004) 8 7 6 5
0.228 - 0.244 (5.791 - 6.197)
0.150 - 0.157** (3.810 - 3.988)
1 0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0- 8 TYP
2
3
4
0.053 - 0.069 (1.346 - 1.752)
0.004 - 0.010 (0.101 - 0.254)
0.014 - 0.019 (0.355 - 0.483) TYP *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
0.016 - 0.050 (0.406 - 1.270)
0.050 (1.270) BSC
SO8 1298
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.
11
LTC1731-4.1/LTC1731-4.2
TYPICAL APPLICATIO S
Linear Charger Using a PNP Transistor
VIN = 6V MBRM120T3 R2 1k C1 1nF R1 10k RSENSE 0.2 Q2 ZTX749 Q1 2N5087 IBAT = 500mA 3 C5 1F CER 8 6 C4 0.47F R2 4.7 R3 0.082 1/4W D1 Q2 Si2305DS MBRS130LT3 LTC1693-5 1
7 VCC SENSE 2 CHRG DRV 8 6
LTC1731-4.2 3 CTIMER 0.1F TIMER BAT PROG GND 4 1 5 RPROG 19.6k
RELATED PARTS
PART NUMBER LT(R)1510-5 LT1512 LT1571-1/LT1571-2 LT1571-5 LT1620/LT1621 LTC1730 LTC1729 LTC1732 LTC1734 DESCRIPTION 500kHz Constant-Voltage/Constant-Current Battery Charger SEPIC Battery Charger 200kHz/500kHz Constant-Current/Constant-Voltage Battery Charger Family Rail-to-Rail Current Sense Amplifier Integrated Pulse Charger for 1-Cell Li-Ion Battery Termination Controller for Li-Ion Constant-Current/Constant-Voltage Li-Ion Linear Battery Charger SOT-23 Li-Ion Battery Charger COMMENTS Most Compact, Up to 1.5A, Charges NiCd, NiMH, Li-Ion Cells VIN Can Be Higher or Lower Than Battery Voltage, 1.5A Switch Up to 1.5A Charge Current for 1- or 2-Cell Li-Ion Batteries, Preset and Adjustable Battery Voltages, C/10 Charge Detection Precise Output Current Programming, Up to 32V VOUT 0.35 Internal N-FET Requires No Blocking Diode Time or Charge Current Termination, Automatic Charger/Battery Detection, Status Output, Preconditioning, 8-Lead MSOP Stand Alone Battery, No C or Firmware Required, Auto Recharge of Low Battery, 10-Pin MSOP, Input Supply Detection Needs Only Two External Components, Monitors Charge Current, No Reverse Diode or Sense Resistor Required
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com
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1.5A Single Cell Switching Battery Charger
VIN 5V TO 6V D2 MBRS130LT3 C3 1F C2 22F CER
R5 1k
7 VCC
SENSE 2 CHRG DRV
LTC1731-4.2 TIMER GND PROG 4 BAT C1* 0.1F 22H CDRH6D38-220NC
+
Li-ION CELL
C2 10F
1731 TA02
5 R4 18.2k 1%
+ Li-ION
BATTERY
+
C3 100F
1731 TA03
*AVX 0603ZC104KAT1A
1731f LT/TP 0301 4K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1999

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