Final Electrical Specifications LTC4052-4.2 Lithium-Ion Battery Pulse Charger with Overcurrent Protection ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO Complete Standalone Pulse Charger for 1-Cell Lithium-Ion Batteries Requires No Microcontroller Internal 0.35Ω NMOS Switch Sense Resistor Limits Maximum Current for Safety Programmable Charge Termination Timer for Maximum Capacity Charging No Blocking Diode Required 1% Float Voltage Accuracy Near End-of-Charge (C/10) Detection Output Low Battery Drain when Input Supply Is Removed Automatic Trickle Charge for Low Battery Automatic Battery Refresh Thermal Shutdown Protection Small 8-Pin Thermally Enhanced MSOP Package U APPLICATIO S ■ ■ ■ ■ July 2002 U FEATURES Standalone Lithium-Ion Battery Charger Personal Information Appliances Cellular Telephones Cradle Chargers The LTC®4052 is a complete standalone pulse charger with integrated MOSFET for 1-cell lithium-ion batteries. An external sense resistor provides maximum charge current limiting as a safety precaution against a user connecting a wall adapter with the incorrect or no current limit. The internal MOSFET prevents reverse battery current from flowing if the input voltage is shorted to ground, eliminating the need for a blocking diode. As the battery accepts charge and approaches the programmed float voltage, the internal MOSFET begins switching off and on with the duty cycle gradually decreasing as the battery approaches a fully charged condition. A programmable timer ends the charge cycle. The near end-of-charge C/10 condition is indicated at the CHRG pin when the average charge current falls to one-tenth of the wallpack current. Removing the input voltage puts the LTC4052 into a sleep mode, dropping the battery current drain to less than 1µA (maximum). The LTC4052 is available in a tiny 8-pin thermally enhanced MSOP package. , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATIO Single Cell 4.2V, 1A, Standalone Li-Ion Battery Charger 1µF 1k 0.047µF LTC4052 RSENSE 0.05Ω GATE CHARGE STATUS 0.022µF CHRG ACPR SENSE BAT TIMER GND 1-CELL 4.2V Li-Ion BATTERY CTIMER 0.1µF BATTERY VOLTAGE (V) 10k VIN 4.0 CHARGE CURRENT (A) 4.7Ω 1k AC PRESENT LTC4052 Charge Profile 4.5 1.0 CHRG (V) VIN = 4.5V TO 10V WITH 1A CURRENT LIMIT 5 3.5 CONSTANT CURRENT 3.0 PULSING CURRENT CHARGE CYCLE ENDS 0.5 0 0 C/10 0 0.5 4052 TA01 1.0 1.5 2.0 TIME (HOURS) 2.5 3.0 4052 • TA01b 405242i 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. 1 LTC4052-4.2 U W W W ABSOLUTE AXI U RATI GS U W U PACKAGE/ORDER I FOR ATIO (Note 1) Input Supply Voltage (VIN)....................................... 12V BAT Voltage ...............................................– 0.3V to 12V GATE (Note 2) .............................................– 0.3V to 8V SENSE, TIMER .................................. – 0.3V to VIN +0.3V CHRG, ACPR .............................................– 0.3V to 12V SENSE, BAT Peak Current ...................................... 1.5A Operating Temperature Range (Note 3) .. – 40°C to 85°C Junction Temperature (Note 4) ............................. 125°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C ORDER PART NUMBER TOP VIEW SENSE 1 ACPR 2 VIN 3 GND 4 8 BAT 7 GATE 6 CHRG 5 TIMER LTC4052EMS8E-4.2 MSE EXPOSED PAD PACKAGE 8-LEAD PLASTIC MSOP MS8 PART MARKING TJMAX = 125°C, θJA = 35°C/W EXPOSED PAD IS GROUND. (MUST BE SOLDERED TO PCB). LTYY Consult LTC Marketing for parts specified with wider operating temperature ranges. DC ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 6V unless otherwise noted. SYMBOL PARAMETER VIN Supply Voltage Wall Adapter Open Circuit Voltage ● IIN Supply Current Fast Charge Mode ● VBAT Battery Float Voltage 0°C ≤ TA ≤ 85°C VRECHRG Recharge Battery Voltage Threshold CONDITIONS MIN TYP MAX 10 V 0.7 1.4 mA 4.5 UNITS ● 4.158 4.137 4.200 4.200 4.242 4.242 V V ● 3.990 3.969 4.050 4.050 4.110 4.110 V V Battery Voltage Falling 0°C ≤ TA ≤ 85°C VMARGIN VBAT – VRECHRG Margin ● 75 150 225 mV VIMAX Overcurrent Trip Voltage ● 90 105 120 mV ITRICKL Trickle Charge Current VBAT = 2V ● 14 24 34 mA VTRICKL Trickle Charge Trip Threshold VBAT Rising ● 2.35 2.45 2.55 V RDS(ON) Internal Switch On-Resistance VBAT = 2.6V VBAT = 4V 0.45 0.35 0.7 0.5 Ω Ω VGATE GATE Pin Voltage VBAT = 2.6V VBAT = 4V 6.5 10.5 TTIMER TIMER Period Accuracy CTIMER = 0.1µF, Fast Charge Mode ILEAK Battery Leakage Through Charger VBAT = 4V, VIN = 0V VSLEEP Sleep Threshold (VIN – VBAT) Low to High (VIN – VBAT) High to Low VACPR ACPR Pin Output Low Voltage IACPR = 3mA ● I LEAKACPR ACPR Pin Leakage Current VIN = 0, VACPR = 6V ● VCHRG CHRG Pin Output Low Voltage ICHRG = 3mA, Charging, C/10 Not Reached ● I LEAKCHRG CHRG Pin Leakage Current VIN = 0, VCHRG = 6V ● ICHRG CHRG Pin Pull-Down Current VCHRG = 1V, Charging, C/10 Reached TSHDN Thermal Shutdown Temperature ∆TSHDN Thermal Shutdown Hysteresis ±10 % 1 µA 45 15 70 mV mV 0.5 0.8 V 1 µA 0.5 0.8 V 1 µA 70 µA ● 20 0 20 V V 40 140 °C 5 °C 405242i 2 LTC4052-4.2 ELECTRICAL CHARACTERISTICS Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Absolute Maximum Rating for GATE pin applies only to externally applied voltage. During normal operation the LTC4052-4.2’s internal charge pump can generate GATE pin voltage exceeding absolute maximum but it is internally current limited. Note 3: The LTC4052EMS8E-4.2 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. Note 4: Junction temperature TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula: TJ = TA + (PD • θJA°C/W) U U U PI FU CTIO S SENSE (Pin 1): Overcurrent Sense Input. A sense resistor (RSENSE) should be connected from VIN to the SENSE pin to program the current limit level. When current limit is tripped, the pass transistor immediately turns off and turns back on after a 640ms time-out period (CTIMER = 0.1µF). The on-off cycle will continue as long as the overcurrent condition persists or until the timer runs out. If overcurrent protection is not needed, short SENSE to VIN. ACPR (Pin 2): Wall Adapter AC Present Open-Drain Output. When the input voltage (wall adapter) is applied to the LTC4052, this pin is pulled to ground by an internal N-channel MOSFET capable of driving an LED. VIN (Pin 3): Positive Input Supply Voltage (4.5V ≤ VIN ≤ 10V). Bypass this pin with a 1µF capacitor in series with a 4.7Ω resistor. GND (Pin 4): Electrical Ground Connection and provides a thermal path from the IC to the PC board copper. Use large copper pads and traces for maximum heat transfer. TIMER (Pin 5): Timer Set Pin. The timer period is set by a capacitor (CTIMER) to ground. The timer period is: tTIMER = (CTIMER • 3Hr)/(0.1µF). The minimum ON time, minimum OFF time and the overcurrent time-out period all scale with tTIMER. CHRG (Pin 6): Charge Status Open-Drain Output. When a depleted battery is being charged, the CHRG pin is pulled to ground by an internal N-channel MOSFET capable of driving an LED. Once the duty cycle at the GATE pin drops below 10%, the N-MOSFET turns off and a weak 40µA current source to ground turns on to indicate a near endof-charge C/10 condition. When a time-out occurs or the input supply is removed, the CHRG pin becomes high impedance. GATE (Pin 7): Gate Drive Output Pin for Internal and External Pass Transistors. An external N-MOSFET transistor can be connected in parallel with the internal transistor to reduce the on-resistance for higher charge current. In this case, an external blocking diode is required to prevent damage to the battery if VIN is shorted to ground. A 10µA current source pulls this pin up to the charge pump potential when turned on and a 40µA current source pulls it down to ground to turn it off. If an overcurrent condition is detected, the GATE pin is immediately pulled to ground. The voltage at this pin is internally clamped to 12V above the GND pin. A series RC network from the GATE to the VIN pin is required to control the slew rate at the VIN pin when the switch is turned on or off. The slew rate control prevents excessive current from the capacitor located in the wall adapter from flowing into the battery when the pass transistor is turned on. BAT (Pin 8): Battery Sense Input Pin. This pin is clamped to 4.7V if the battery is disconnected while charging. An internal resistor divider presets the final float voltage to 4.2V. If the BAT pin drops below 4.05V after the charge cycle has ended, the timer resets and a new charge cycle begins. 405242i 3 LTC4052-4.2 W BLOCK DIAGRA ACPR 2 45mV VIN 3 + – 105mV + 100ms FILTER BAT GND SLEEP IMAX – + – + 10mΩ – 4 VIN 1 SENSE 7 GATE 8 BAT 24mA CHARGE PUMP TRIPLER TIMER 5 OSCILLATOR TRICKLE FAST VMIN CLK + – CHRG 6 VRECHRG STOP – LOGIC + TIMERS 40µA C/10 + VFLOAT + – TEMP THERMAL SHUTDOWN REFERENCE VMAX + – 1.23V 1.23V 4052 BD U OPERATIO The LTC4052 is a complete lithium-ion battery pulse charger with an internal 0.35Ω N-MOSFET switch driven by an internal charge pump. The charge current is set by the current limit of the input supply (wall adapter). An external RSENSE sets the maximum allowable charge overcurrent and prevents a wall adapter with the wrong current limit from damaging the battery. If the current limit of the input supply is above IMAX, the charger will immediately terminate charging and will retry after 640ms (CTIMER = 0.1µF). If the battery is disconnected while in fast charge mode, the charge pump will be turned off when the voltage at the BAT pin rises above 4.7V and turned back on when the voltage drops below the float voltage. A charge cycle begins when the voltage at the VIN pin rises above the BAT pin by 45mV. The charger will go into trickle charge mode if the battery voltage is below 2.45V. The trickle charge current is preset to 24mA and is provided by an internal current source. In trickle mode, both the pass transistor and charge pump are off. 405242i 4 LTC4052-4.2 U OPERATIO When the cell voltage exceeds 2.45V, the charger goes into fast charge mode. In this mode, the charge pump turns on and ramps up the gate voltage of the pass transistor turning it on. The voltage at the VIN pin then ramps down to VBAT plus the voltage drop across the pass transistor and RSENSE, thus reducing the power dissipation in the pass transistor. The charge current is determined by the current limit of the input supply. When the battery voltage reaches the final float voltage, the pass transistor turns off for 100ms (minimum offtime). It remains off as long as the battery voltage stays above the float voltage after the 100ms off-time. After the minimum off-time, if the battery voltage drops below the float voltage, the pass transistor turns back on for at least 400ms (minimum on-time). As the battery approaches full charge, the off-time will get longer and the on-time will stay at 400ms. The voltage at the BAT pin will be slightly higher than the final float voltage due to the ESR associated with the battery pack. This voltage level should not turn on the overvoltage protection circuitry often located in the battery pack. When the duty cycle at the GATE pin drops below 10%, a comparator turns off the N-FET at the CHRG pin and connects a weak current source (40µA) to ground to indicate a near end-of-charge C/10 condition. The pulse charging will continue until the timer stops. An external capacitor at the TIMER pin sets the total charge time, the minimum on- and off-time and the overcurrent retry period. After a time-out has occurred, the charge cycle terminates and the CHRG pin is forced high impedance. After the charging stops, if the battery voltage drops below 4V, due to external loading or internal leakage, a new charge cycle will automatically resume. U W U U APPLICATIO S I FOR ATIO Input Voltage (Wall Adapter) Battery Charge Current The input voltage to the LTC4052 must have some method of current limit capability. The current limit level of the input power source must be lower than the overcurrent limit (IMAX) set by the sense resistor IMAX = 105mV/(RSENSE + 10mΩ). The 10mΩ represents bond wire resistance internal to the IC. If a wall adapter without current limit is used, or the current limit level is above IMAX, the charger will turn on briefly and then immediately turn off after the overcurrent condition is detected. This cycle will be resumed every 640ms (CTIMER = 0.1µF) until the total charge time has run out. If overcurrent protection is not needed, short the SENSE pin to VIN. The battery charge current is determined by the current limit of the input supply (wall adapter). However, this current must not exceed the maximum charge current, IMAX. If an overcurrent condition is detected, the charging is immediately terminated, the GATE pin is pulled to ground and the charge pump turns off. The charging will resume after a 640ms time off (CTIMER = 0.1µF). Trickle Charge and Defective Battery Detection At the beginning of the charge cycle, if the cell voltage is low (less than 2.45V) the charger goes into a 24mA trickle charge mode. If the low cell voltage persists for one quarter of the total charge time, the battery is considered defective and the charge cycle is terminated. The CHRG pin output is then forced to a high impedance state. Programming the Timer The programmable timer is used to terminate the charge cycle and sets the minimum ON/OFF time and the overcurrent time-off period. The length of the timer is programmed by an external capacitor from the TIMER pin to ground. The total charge time is: Time (Hours) = (3 Hours)(CTIMER/0.1µF) or CTIMER = 0.1µF • Time (Hours)/3 (Hours) The timer starts when the input voltage (at least 40mV greater than VBAT) is applied. After a time-out has occurred, the charging stops and the CHRG pin becomes high impedance. 405242i 5 LTC4052-4.2 U U W U APPLICATIO S I FOR ATIO CHRG Status Output Pin This open-drain output can report three different charger conditions: Charger Status CHRG Pin Behavior Not Charging High Impedance Charging Strong Pulldown Charging, C/10 Reached Weak 40µA Pulldown VIN Internal Pass Transistor VDD 3 VIN LTC4052 CHRG 620k 6 full charge. When the duty cycle falls below 10%, the comparator trips and turns off the N-MOSFET at the CHRG pin and switches in a weak (40µA) current source to ground. The 40µA turns off when the charge cycle terminates. C/10 detection is disabled in trickle charge mode. MICROPROCESSOR 2k OUT IN 4052 F01 Figure 1. Interfacing with Microprocessor Using a simple two-resistor network a microprocessor can distinguish all three states. See Figure 1. When the LTC4052 is charging a battery, an internal NMOSFET pulls the CHRG pin to ground. When C/10 is reached, the strong NMOS pulldown is replaced by a weak 40µA current source pulldown. When the LTC4052 is not charging a battery, the CHRG pin is high impedance. Using the network in Figure 1, the microprocessor can determine charger state using the following procedure: 1. Force the digital output pin, OUT, high and read the logic value at the digital input, IN. If IN reads low, a charger cycle is in progress. 2. If the IN pin is high, force the OUT pin to be high impedance, then read the logic level at the IN pin again. If IN is low, the charge cycle is still in progress, the timer is still running, but the charge current has dropped below 10% of the programmed value indicating that the charge cycle is nearly complete. 3. If the logic level at the IN pin is high, the charge cycle has ended. An N-channel MOSFET (0.35Ω) is included in the LTC4052 as the pass transistor. The gate of the MOSFET is controlled by an internal charge pump. The body is connected to ground instead of source terminal. There is no body diode from the BAT pin back to the VIN pin; therefore, no blocking diode is required in series with the battery or the input supply. This will not only reduce cost but also reduce the heat generated while in fast charge mode. An internal thermal shutdown circuit turns the pass transistor off when the die temperature exceeds approximately 140°C with 5°C of thermal hysteresis. Gate Drive The MOSFET gate drive consists of a regulated 10µA current source charge pump. A series RC network is required from the GATE pin to the VIN pin. When the MOSFET is turned on, the voltage at the VIN pin will start slewing down to a voltage equal to VBAT plus the voltage drop across the pass transistor and RSENSE. The slew rate is equal to 10µA/C. By ramping the VIN pin down slowly, the inrush current is reduced. The resistor in series with the capacitor is required to limit the transient current when the input supply is first applied. When the charge pump is turned off, a 50µA current source to ground will start pulling the GATE voltage down. Once the pass transistor is off, the voltage at the VIN pin will begin slewing up with the rate equal to 50µA/C. With this external capacitor, the voltage at the VIN pin is ramping at a controlled manner (Figure 2). For higher current applications an external power N-channel MOSFET can be connected in parallel with the internal pass transistor. Because the charge pump output is clamped to 12V above GND, the external MOSFET gate to source breakdown voltage should be rated for 16V or more. Near End-of-Charge C/10 Detection The LTC4052 includes a comparator to monitor the duty cycle at the GATE pin to detect when the battery is nearing 405242i 6 LTC4052-4.2 U W U U APPLICATIO S I FOR ATIO 10µA/C The power dissipated by the IC is: 50µA/C P = (IBAT • IBAT • RDS(ON)) + (VIN • IIN) VIN 50µA/C GATE VOLTAGE = 0.35 + 0.004 10µA/C 10µA/C 50µA/C = (1A • 1A • 0.35Ω) + (4V • 1mA) 4052 TA02 Figure 2. Slew Rate at GATE and VIN Pins with the RC Network from GATE to VIN Thermal Considerations The power handling capability is limited by the maximum rated junction temperature (125°C) and the amount of PC board copper used as a heat sink. The power dissipated by the device consists of two components: 1. Input supply current multiplied by the input voltage 2. The voltage drop across the switch (SENSE pin to BAT pin) multiplied by the charge current The LTC4052 has internal thermal shutdown designed to protect the IC from overtemperature conditions. For continuous charging in the fast charge mode, the maximum junction temperature must not be exceeded. It is important to give careful consideration to all sources of thermal resistance from junction to ambient. Additional heat sources mounted nearby must also be considered. Surface mount packages rely primarily on the PC board copper to dissipate the heat generated by the package to the surrounding air. Since the PC board copper is the heat sink, generous amounts of copper surrounding the package are recommended to increase the effectiveness of the heat sink. In addition, feedthrough vias or plated through holes (located directly beneath the package and elsewhere) connecting internal copper and backside copper layers help transfer and spread the heat generated by the package. Calculating Junction Temperature Example: Find the maximum junction temperature for a battery voltage of 4V (VIN will collapse to around VBAT in the fast charge mode), charge current of 1A and a maximum ambient temperature of 75°C. = 0.354W The LTC4052 is available in an enhanced 8-pin MSOP package which features an exposed copper pad on the bottom of the package allowing it to be soldered directly to the PC board copper for maximum heat transfer. This greatly reduces the thermal resistance and increases the power handling capability when compared to a standard MSOP package. The junction to aimbient thermal resistance of this package is approximately 35°C/W depending on the copper area. The junction temperature rise above ambient will be approximately: (0.354W)(35°C/W) = 12.39°C The maximum junction temperature will be equal to the maximum junction temperature rise above ambient plus the maximum ambient temperature or: TJMAX = 85°C + 12.39°C = 97.39°C ACPR Output Pin When the input voltage is 45mV higher than the voltage at the BAT pin, the ACPR pin is pulled to ground to indicate that the input supply (wall adapter) is applied. After the input supply is removed, this pin will become high impedance. An internal 100ms filter prevents the LTC4052 from turning off if the voltage at the VIN pin rings and gets too close to VBAT due to parasitic inductance. Stop Charging The charger is off when the voltage at the VIN pin is less than 45mV above VBAT (sleep mode). The charge pump and the internal pass transistor are turned off, and the internal resistor divider is disconnected to reduce the current drain on the battery in the sleep mode. 405242i 7 LTC4052-4.2 U TYPICAL APPLICATIO S External N-MOSFET for Higher Charge Current Minimum Component Count 4.2V Li-Ion Battery Charger VIN = 5V TO 10V WITH 2A CURRENT LIMIT VIN = 5V TO 10V WITH 600mA CURRENT LIMIT MBRS120T3 3 3 4.7Ω 1µF AC PRESENT STATUS 1k 1k 0.047µF LTC4052 SENSE CHARGE STATUS 6 2 CHRG GATE ACPR BAT RSENSE 25mΩ SENSE 7 CTIMER 0.1µF 6 NC Si2302DS 8 2 NC 1-CELL 4.2V Li-Ion BATTERY GND 5 0.047µF LTC4052 1 0.022µF TIMER 10k VIN 10k VIN 4 CHRG GATE ACPR BAT TIMER CTIMER 0.1µF 1 7 8 0.022µF GND 5 1-CELL 4.2V 600mA Li-Ion BATTERY 4 4052 TA04 4052 TA03 U PACKAGE DESCRIPTIO MS8E Package 8-Lead Plastic MSOP (Reference LTC DWG # 05-08-1662) BOTTOM VIEW OF EXPOSED PAD OPTION 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 0.889 ± 0.127 (.035 ± .005) 2.794 ± 0.102 (.110 ± .004) 8 7 6 5 0.52 (.206) REF 1 1.83 ± 0.102 (.072 ± .004) RECOMMENDED SOLDER PAD LAYOUT 5.23 (.206) MIN 0.42 ± 0.04 (.0165 ± .0015) TYP 2.083 ± 0.102 3.2 – 3.45 (.082 ± .004) (.126 – .136) 0.254 (.010) 3.00 ± 0.102 (.118 ± .004) NOTE 4 4.88 ± 0.1 (.192 ± .004) DETAIL “A” 2.06 ± 0.102 (.080 ± .004) 0° – 6° TYP GAUGE PLANE 0.65 (.0256) BSC 0.53 ± 0.015 (.021 ± .006) DETAIL “A” 1 2 3 4 8 1.10 (.043) MAX 0.86 (.34) REF 0.18 (.077) 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 SEATING PLANE 0.22 – 0.38 (.009 – .015) 0.13 ± 0.05 (.005 ± .002) 0.65 (.0256) BCS MSOP (MS8E) 1001 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1510-5 500kHz CC/CV Battery Charger Most Compact, Up to 1.5A, Charges NiCd, NiMH, Li-Ion Cells LTC1729 Termination Controller for Li-Ion Time or Charge Current Termination, Automatic Charger/Battery Detection Status Output, Preconditioning, 8-Lead MSOP LTC1730 Li-Ion Battery Pulse Charger with Thermistor Interface Battery Temperature Sensing, FAULT Output, SO-8 and SSOP-16 Packages LTC1731 Li-Ion Battery Charger Controller CC/CV Charges Li-Ion Cells, 8-Lead MSOP LTC1732 Li-Ion Battery Charger Controller CC/CV Charges Li-Ion Cells, Automatic Battery Detection, 10-Lead MSOP LTC1733 Li-Ion Battery Charger with Thermal Regulation Standalone Charger, Constant-Current/Constant-Voltage/ Constant-Temperature, Integrated MOSFET, No External Sense Resistor or Blocking Diodes LTC1734 ThinSOTTM Li-Ion Battery Charger Only Two External Components, Up to 700mA ICHARGE, No Reverse Current Diode Required, No Sense Resistor Required LTC4050 Li-Ion Battery Charger Controller with Thermistor Interface Drives External MOSFET, 10-Lead MSOP ThinSOT is a trademark of Linear Technology Corporation 8 405242i Linear Technology Corporation LT/TP 0702 1.5K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2001