LTC1731-8.2/LTC1731-8.4 Lithium-Ion Linear Battery Charger Controller U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LTC ®1731-8.2/LTC1731-8.4 are complete constantcurrent/constant-voltage linear charger controllers for 2cell lithium-ion (Li-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 7% accuracy. An internal resistor divider and precision reference set the final float potential with 1% accuracy. The output float voltages are set internally to 8.2V (LTC1731-8.2) or 8.4V (LTC1731-8.4). 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 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) 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 battery voltage exceeds 4.95V. U APPLICATIO S ■ ■ ■ ■ Cellular Phones Handheld Computers Charging Docks and Cradles Programmable Current Source The LTC1731-8.2/LTC1731-8.4 are available in the 8-pin MSOP and SO packages. For 1-cell Li-Ion battery charging, see the LTC1731-4.1 and LTC1731-4.2 data sheets. , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATIO 400mA Li-Ion Charger Typical Li-Ion Charge Cycle VIN = 9V CONSTANT CURRENT CHARGE STATUS VCC SENSE 2 DRV CHRG RSENSE 0.2Ω 8 6 Q1 Si9430DY LTC1731-8.4 3 CTIMER 0.1µF TIMER BAT PROG GND 4 1µF IBAT = 400mA 1 5 RPROG* 19.6k + 2-CELL BATTERY VOLTAGE 400 8 400mA HR BATTERY 300 CHARGE CURRENT 200 CHRG LED OFF 100 7 TIMER STOPS 10µF Li-ION 0 1731 TA01 *SHUTDOWN INVOKED BY FLOATING THE PROG PIN 9 CONSTANT VOLTAGE BATTERY VOLTAGE(V) 7 2k CHARGE CURRENT (mA) MBRM120T3 0 0.5 2.0 1.5 1.0 TIME (HOURS) 2.5 6 3.0 1731 TA01b sn1731 17318fs 1 LTC1731-8.2/LTC1731-8.4 W W U W ABSOLUTE MAXIMUM RATINGS (Note 1) Input Supply Voltage (VCC) ................................... 13.2V SENSE, DRV, BAT, TIMER, PROG ............ – 0.3V to VCC CHRG ..................................................... – 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 U W U PACKAGE/ORDER INFORMATION ORDER PART NUMBER TOP VIEW BAT CHRG TIMER GND 1 2 3 4 8 7 6 5 SENSE VCC DRV PROG LTC1731EMS8-8.2 LTC1731EMS8-8.4 MS8 PACKAGE 8-LEAD PLASTIC MSOP MS8 PART MARKING TJMAX = 150°C, θJA = 200°C/W LTSW LTPE ORDER PART NUMBER TOP VIEW BAT 1 8 SENSE CHRG 2 7 VCC TIMER 3 6 DRV GND 4 5 PROG LTC1731ES8-8.2 LTC1731ES8-8.4 S8 PART MARKING S8 PACKAGE 8-LEAD PLASTIC SO 173182 173184 TJMAX = 150°C, θJA = 125°C/W Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 9V unless otherwise noted. SYMBOL PARAMETER VCC Input Supply Voltage CONDITIONS MIN ICC Input Supply Current Charger On, Current Mode Shutdown Mode Sleep Mode (Battery Drain Current) ● ● VBAT Regulated Output Voltage LTC1731-8.2 (9V ≤ VCC ≤ 12V) LTC1731-8.4 (9V ≤ VCC ≤ 12V) ● ● IBAT Current Mode Charge Current RPROG = 19.6k, RSENSE = 0.2Ω RPROG = 19.6k, RSENSE = 0.2Ω RPROG = 97.6k, RSENSE = 0.2Ω ● ● TYP 8.8 MAX UNITS 12 V 1 1 15 3 2 30 mA mA µA 8.118 8.316 8.2 8.4 8.282 8.484 465 415 70 500 500 100 535 585 130 mA mA mA V V ITRIKL Trickle Charge Current VBAT = 4V, RPROG = 19.6k, ITRIKL = (VCC – VSENSE)/0.2Ω ● 30 50 100 mA VTRIKL Trickle Charge Threshold Voltage BAT Rising ● 4.7 4.95 5.1 V VUV VCC Undervoltage Lockout Voltage VCC Rising ● 8.2 8.8 V ∆VUV VCC Undervoltage Lockout Hysteresis VCC Falling VMSD Manual Shutdown Threshold Voltage PROG Pin Rising PROG Pin Falling 2.457 2.446 V V IDRV Drive Pin Current VDRV = VCC – 2V 26 µA 200 mV sn1731 17318fs 2 LTC1731-8.2/LTC1731-8.4 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 9V unless otherwise noted. SYMBOL PARAMETER CONDITIONS VASD Automatic Shutdown Threshold Voltage (VCC – VBAT) Falling (VCC – VBAT) Rising MIN TYP MAX UNITS 30 40 54 69 90 100 mV mV VDIS Voltage Mode Disable Threshold Voltage VDIS = (VCC – VTIMER) 0.4 V IPROG PROG Pin Current Internal Pull-Up Current, No RPROG PROG Pin Load Regulation PROG Pin Source Current, ∆VPROG ≤ 5mV VPROG PROG Pin Voltage RPROG =19.6k ICHRG CHRG Pin Weak Pull-Down Current VCHRG = 1V VCHRG CHRG Pin Output Low Voltage ICHRG = 5mA IC/10 End of Charge Indication Current Level RPROG = 19.6k, RSENSE = 0.2Ω tTIMER TIMER Accuracy CTIMER = 0.01µF 10 % VCLAMP DRV Pin Clamp Voltage VCLAMP = VCC – VDRV, IDRIVE = 50µA 6.5 V ● µA 2.5 ● µA 300 2.457 50 Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. ● 25 V 100 150 µA 0.6 1.2 V 50 100 mA 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. U W TYPICAL PERFOR A CE CHARACTERISTICS Trickle Charge Current vs Temperature 60 55 ITRKL (mA) 55 ITRKL (mA) 60 RPROG = 19.6K RSENSE = 0.2Ω VBAT = 4V TA = 25° 50 Trickle Charge Threshold Voltage vs VCC 4.96 RPROG = 19.6K RSENSE = 0.2Ω VBAT = 4V VCC = 9V 4.94 50 4.93 4.92 4.91 45 45 RPROG = 19.6K TA = 25° 4.95 VTRKL (V) Trickle Charge Current vs VCC 4.90 4.89 40 9 10 11 12 VCC (V) 40 –50 –25 0 25 50 75 100 125 9 10 11 12 VCC (V) TEMPERATURE (°C) 1731 G01 4.88 1731 G06 1731 G08 sn1731 17318fs 3 LTC1731-8.2/LTC1731-8.4 U W TYPICAL PERFOR A CE CHARACTERISTICS Trickle Charge Threshold Voltage vs Temperature Timer Accuracy vs VCC 4.94 110 VCC = 9V CTIMER = 0.1µF VBAT = 6V TA = 25° CTIMER = 0.1µF VCC = 9V 105 4.92 4.91 tTIMER (%) 105 tTIMER (%) VTRKL (V) 4.93 Timer Accuracy vs Temperature 110 100 95 95 4.90 –50 –25 25 0 75 50 100 90 125 9 10 11 75 540 530 520 125 Program Pin Voltage vs VCC 2.48 RPROG = 19.6K RSENSE = 0.2Ω VBAT = 6V VCC = 9V RPROG = 19.6K VBAT = 6V TA = 25° 2.47 510 VPROG (V) RPROG = 19.6K RSENSE = 0.2Ω VBAT = 6V TA = 25° 100 1731 G04 Battery Charge Current vs Temperature IBAT (mA) IBAT (mA) 50 1731 G05 Battery Charge Current vs VCC 500 25 0 TEMPERATURE (°C) 1731 G03 510 90 –50 –25 12 VCC (V) TEMPERATURE (°C) 520 100 500 2.46 490 490 2.45 480 470 480 9 10 11 460 –50 –25 12 VCC (V) 2.44 0 25 50 75 100 125 1731 G09 9 10 11 12 VCC (V) TEMPERATURE (°C) 1731 G07 1731 G10 Program Pin Voltage vs Temperature 2.470 RPROG = 19.6k VCC = 9V VPROG (V) 2.465 2.460 2.455 2.450 –50 –25 0 25 50 75 100 125 TEMPERATURE (°C) 1731 G02 sn1731 17318fs 4 LTC1731-8.2/LTC1731-8.4 U U U PIN FUNCTIONS 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 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 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 VCC. VCC (Pin 7): Input Supply Voltage. VCC ranges from 8.8V to 12V when charging. If VCC drops below VBAT + 54mV, for example when the input supply is disconnected, then the IC enters sleep mode with ICC < 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: RSENSE = (VPROG • 800Ω)/(RPROG • IBAT) sn1731 17318fs 5 LTC1731-8.2/LTC1731-8.4 W BLOCK DIAGRA VCC 7 RSENSE SENSE + 80Ω C1 2 + – 800Ω – CHRG 8 54mV + C4 – – C/10 STOP C/10 TIMER + DRV CA SLP OSCILLATOR BAT – SHDN 3 720Ω LOGIC LBO COUNTER 6 1 C2 + 100µA 4.9V VREF – + – VA VCC A1 – + + C3 VREF 2.457V 2.5µA CHARGE 5 BATTERY CURRENT IBAT = (2.457V • 800Ω)/(RPROG • RSENSE) PROG GND 4 1731 BD RPROG sn1731 17318fs 6 LTC1731-8.2/LTC1731-8.4 U OPERATIO The LTC1731-8.2/LTC1731-8.4 are linear battery charger controllers. 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 that creates 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 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 RSENSE and RPROG. 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 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 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 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 15µA. This greatly reduces the current drain on the battery and increases the standby time. sn1731 17318fs 7 LTC1731-8.2/LTC1731-8.4 U W U U APPLICATIONS INFORMATION Charger Conditions The charger is off when any of the following conditions exist: the VCC pin is less than 8.2V, the droput voltage (VCC - VBAT) is less than 54mV, the PROG pin is floating, or the timer has ended. 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 8.2V. To prevent oscillation around VCC = 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 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 is then pulled up to VCC 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: IBAT = (2.457V/RPROG)(800Ω/RSENSE) 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)(CTIMER/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 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 to ground by an internal N-channel MOSFET that can drive an LED. When the charge current drops to 10% of the fullscale 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 microprocessor can detect three states from this pin (charging, C/10 and stop charging). See Figure 1. V+ VDD 7 VCC 100k LTC1731-8.4 CHRG 2 µPROCESSOR 2k OUT IN 1731 F01 where RPROG is the total resistance from the PROG pin to ground. Figure 1. Microprocessor Interface 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 sn1731 17318fs 8 LTC1731-8.2/LTC1731-8.4 U W U U APPLICATIONS INFORMATION 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 fullscale 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 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 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 RPROG = 19.6k and 100mV across RSENSE, 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 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 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 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. sn1731 17318fs 9 LTC1731-8.2/LTC1731-8.4 U PACKAGE DESCRIPTION MS8 Package 8-Lead Plastic MSOP (Reference LTC DWG # 05-08-1660) 0.889 ± 0.127 (.035 ± .005) 5.23 (.206) MIN 3.2 – 3.45 (.126 – .136) 0.42 ± 0.04 (.0165 ± .0015) TYP 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 0.65 (.0256) BSC 8 7 6 5 0.52 (.206) REF RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 3.00 ± 0.102 (.118 ± .004) NOTE 4 4.88 ± 0.1 (.192 ± .004) DETAIL “A” 0° – 6° TYP GAUGE PLANE 0.53 ± 0.015 (.021 ± .006) DETAIL “A” 1 2 3 4 1.10 (.043) MAX 0.86 (.34) REF 0.18 (.077) SEATING PLANE 0.22 – 0.38 (.009 – .015) 0.65 (.0256) BCS 0.13 ± 0.05 (.005 ± .002) MSOP (MS8) 1001 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 sn1731 17318fs 10 LTC1731-8.2/LTC1731-8.4 U PACKAGE DESCRIPTION S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 8 7 6 5 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) SO8 1298 1 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0.053 – 0.069 (1.346 – 1.752) 0°– 8° TYP 0.016 – 0.050 (0.406 – 1.270) 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 2 3 4 0.004 – 0.010 (0.101 – 0.254) 0.050 (1.270) BSC 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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 11 LTC1731-8.2/LTC1731-8.4 U TYPICAL APPLICATIO Linear Charger Using a PNP Transistor VIN = 9V MBRM120T3 R2 2k C1 1nF 7 CHARGE STATUS VCC SENSE 2 DRV CHRG R1 10k RSENSE 0.25Ω Q2 ZTX749 8 6 Q1 2N5087 LTC1731-8.4 3 TIMER CTIMER* 0.1µF BAT PROG C3 1µF IBAT = 400mA 1 5 GND + RPROG 19.6k 4 2-CELL Li-ION *AVX 0603ZC104KAT1A C2 10µF 1731 TA02 RELATED PARTS 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 VIN Can Be Higher or Lower Than Battery Voltage, 1.5A Switch LT1571-1/-2/-5 200kHz/500kHz 1.5A Constant-Current/Constant-Voltage Battery Charger Charges 1- or 2-Cell Li-Ion Batteries, Preset and Adjustable Battery Voltages, C/10 Charge Detection LTC1615 SOT-23 Step-Up Switching Regulator 1.2V ≤ VIN ≤ 15V; Up to 34 Output; IQ = 20µA LT1620 Rail-to-Rail Current Sense Amplifier Precise Output Current Programming, Up to 32V VOUT LTC1682 Low Noise Doubler Charge Pump Output Noise = 60µVRMS; 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 and Thermal Regulation Efficient 1.5A Charger with Many Features Including 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; VPROG Tracks ICHARGE No Diode Needed, No Sense Resistor Needed LTC1754 ThinSOT Charge Pump IOUT = 50mA; 2V ≤ VIN ≤ 4.4V; for Backlight White LED LTC4050 Complete Li-Ion Charger with Thermistor Interface No Firmware required, AC Adapter Indicator Automatic Charge and Recharge sn1731 17318fs 12 Linear Technology Corporation LT/TP 0602 2K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com © LINEAR TECHNOLOGY CORPORATION 2000