LTC1732-4/LTC1732-4.2 Lithium-Ion Linear Battery Charger Controller U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LTC ®1732 is a complete constant-current/constantvoltage linear charger controller for lithium-ion (Li-Ion) batteries. Nickel-cadmium (NiCd) and nickel metalhydride (NiMH) batteries can also be charged with constant current using external termination. Charge current can be programmed with 7% (max) accuracy using external sense and program resistors. An internal resistor divider and precision reference set the final float voltage with 1% accuracy. The SEL pin allows users to charge either 4.1V or 4.2V cells. Complete Linear Charger Controller for 1-Cell Lithium-Ion Batteries Preset Charge Voltage with 1% Accuracy Programmable Charge Current C/10 Charge Current Detection Output Programmable Charge Termination Timer Small, Thin 10-Pin MSOP Package Select Pin Charges 4.1V or 4.2V Cells (LTC1732-4) Input Supply (Wall Adapter) Detection Output 4.5V to 12V Input Voltage Range Automatic Sleep Mode When Input Supply is Removed (Only 7µA Battery Drain) Automatic Trickle Charge of Low Voltage Cells Programmable for Constant-Current-Only Mode Battery Insertion Detect 4.05V Recharge Threshold for 4.2V Cells (LTC1732-4.2) 3.8V Recharge Threshold for 4.1V or 4.2V Cells (LTC1732-4) When the input supply is removed, the LTC1732 automatically enters a low current sleep mode, dropping the battery drain current to 7µA. 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 LTC1732 begins a new charge cycle when a discharged battery is connected to the charger or when the input power is applied. In addition, if the battery remains connected to the charger and the cell voltage drops below 3.8V for the LTC1732-4 or below 4.05V for the LTC1732-4.2, a new charge cycle will automatically begin. U APPLICATIO S ■ ■ ■ Cellular Phones Handheld Computers Charging Docks and Cradles The LTC1732 is available in the 10-pin MSOP package. , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATIO Single Cell 4.2V Li-Ion Battery Charger VIN = 6V MBRM120T3 R2 1k R1 1k 8 2 VCC SEL SENSE 3 DRV CHRG RSENSE 0.2Ω 9 7 Q1 Si9430DY LTC1732-4 10 4 CTIMER 0.1µF ACPR BAT TIMER PROG GND 5 1µF IBAT = 500mA 1 6 RPROG* 19.6k 10µF + 4.2V Li-Ion CELL 1732 TA01 *SHUTDOWN INVOKED BY FLOATING THE PROG PIN 1 LTC1732-4/LTC1732-4.2 W U U U W W W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) Input Supply Voltage (VCC) ................................... 13.2V SENSE, DRV, BAT, SEL, TIMER, PROG, CHRG, ACPR ......................................... – 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 ORDER PART NUMBER TOP VIEW BAT SEL CHRG TIMER GND 1 2 3 4 5 10 9 8 7 6 ACPR SENSE VCC DRV PROG LTC1732EMS-4 LTC1732EMS-4.2 MS10 PART MARKING MS10 PACKAGE 10-LEAD PLASTIC MSOP LTNJ LTUA TJMAX = 140°C, θJA = 180°C/W Consult factory 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 = 6V unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN VCC Input Supply Voltage ICC Input Supply Current Charger On, Current Mode Shutdown Mode Sleep Mode (Battery Drain Current) ● ● VBAT Regulated Output Voltage LTC1732-4; 5V ≤ VCC ≤ 12V, VSEL = GND LTC1732-4/LTC1732-4.2; 5V ≤ VCC ≤ 12V, VSEL = VCC ● ● IBAT Current Mode Charge Current RPROG = 19.6k, RSENSE = 0.2Ω RPROG = 19.6k, RSENSE = 0.2Ω ● ● TYP 4.5 MAX UNITS 12 V 1 1 7 3 3 20 mA mA µA 4.059 4.158 4.1 4.2 4.141 4.242 465 415 500 535 585 mA mA V V RPROG = 97.6k, RSENSE = 0.2Ω 60 100 140 mA ITRIKL Trickle Charge Current VBAT = 2V, RPROG = 19.6k, ITRIKL = (VCC – VSENSE)/0.2Ω ● 30 50 110 mA VTRIKL Trickle Charge Threshold Voltage From Low to High ● 2.35 2.457 2.55 V VUV VCC Undervoltage Lockout Voltage From Low to High ● 4.1 4.5 ∆VUV VCC Undervoltage Lockout Hysteresis VMSD Manual Shutdown Threshold Voltage PROG Pin Low to High PROG Pin High to Low VASD Automatic Shutdown Threshold Voltage (VCC – VBAT) High to Low (VCC – VBAT) Low to High VDIS Voltage Mode Disable Threshold Voltage VDIS = VCC – VTIMER IPROG PROG Pin Current Internal Pull-Up Current, No RPROG PROG Pin Source Current, ∆VPROG ≤ 5mV 200 VPROG PROG Pin Voltage RPROG =19.6k VACPR ACPR Pin Output Low Voltage IACPR = 5mA ICHRG CHRG Pin Weak Pull-Down Current VCHRG = 1V VCHRG CHRG Pin Output Low Voltage ICHRG = 5mA VSEL SEL Pin Threshold 2 2.457 2.446 30 40 54 69 V V 90 100 V 300 µA µA 2.457 15 ● 0.3 mV mV 0.4 2.5 ● V mV V 0.7 1.2 V 35 55 µA 0.6 1.2 V 2 V LTC1732-4/LTC1732-4.2 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 6V unless otherwise noted. SYMBOL PARAMETER CONDITIONS IC/10 End of Charge Indication Current Level RPROG = 19.6k, RSENSE = 0.2Ω tTIMER TIMER Accuracy CTIMER = 0.1µF VRECHRG Recharge Battery Voltage Threshold per Cell VBAT from High to Low (LTC1732-4) VBAT from High to Low (LTC1732-4.2) Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. MIN 25 ● 3.72 3.95 TYP MAX UNITS 50 100 mA 10 % 3.80 4.05 V V Note 2: The LTC1732E 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. U W TYPICAL PERFOR A CE CHARACTERISTICS Trickle Charge Current vs VCC RPROG =19.6kΩ RSEN = 0.2Ω VBAT = 2V TA = 25°C 110 VCC = 6V RPROG = 19.6kΩ 50 45 2.460 4 6 8 12 10 2.450 –50 25 50 75 0 TEMPERATURE (°C) –25 VCC (V) 1732 G01 110 60 ITRKL (mA) TTIMER (%) 55 100 95 25 50 75 0 TEMPERATURE (°C) 100 125 4 6 8 10 12 VCC (V) 1732 G04 100 125 RPROG =19.6kΩ RSEN = 0.2Ω VBAT = 2V VCC = 6V 50 45 90 –25 25 50 75 0 TEMPERATURE (°C) Trickle Charge Current vs Temperature 105 2.465 2.455 –25 1732 G03 CTIMER = 0.1µF VBAT = 3V TA = 25°C VCC = 6V VTRKL (V) 90 –50 125 Timer Accuracy vs VCC 2.470 2.250 –50 100 1732 G02 Trickle Charge Threshold Voltage vs Temperature 2.460 100 95 2.455 40 VCC = 6V CTIMER = 0.1µF 105 2.465 VPROG (V) ITRKL (mA) 55 Timer Accuracy vs Temperature Program Voltage vs Temperature 2.470 TTIMER (%) 60 1732 G05 40 –50 –25 25 50 75 0 TEMPERATURE (°C) 100 125 1732 G06 3 LTC1732-4/LTC1732-4.2 U W TYPICAL PERFOR A CE CHARACTERISTICS Trickle Charge Threshold Voltage vs VCC Battery Charge Current vs Temperature 530 RPROG =19.6kΩ RSEN = 0.2Ω VBAT = 3V VCC = 6V 510 500 Program Pin Voltage vs VCC 2.480 RPROG =19.6kΩ TA = 25°C 2.475 VTRKL (V) IBAT (mA) 520 2.480 2.470 2.470 2.465 2.465 2.460 2.460 490 2.455 2.455 480 2.450 2.450 470 2.445 2.445 460 –50 –25 25 50 75 0 TEMPERATURE (°C) 100 125 2.440 2.440 4 6 8 4 12 10 8 6 Recharge Threshold Voltage vs Temperature Battery Charge Current vs VCC 4.1 520 RPROG =19.6kΩ = 0.2Ω R 515 SEN VBAT = 3V T = 25°C 510 A VCC = 6V LTC1732-4.2 VRECHRG (V) 4.0 500 495 3.9 3.8 490 LTC1732-4 485 480 4 6 8 10 12 VCC (V) 1732 G10 4 12 1732 G09 1732 G08 505 10 VCC (V) VCC (V) 1732 G07 IBAT (mA) RPROG =19.6kΩ TA = 25°C VBAT = 3V 2.475 VPROG (V) 540 3.7 –50 –25 25 50 75 0 TEMPERATURE (°C) 100 125 1732 G11 LTC1732-4/LTC1732-4.2 U U U PIN FUNCTIONS BAT (Pin 1): Battery Sense Input. A bypass capacitor of 10µF or more is required to keep the loop stable when the battery is not connected. A precision internal resistor divider on this pin sets the final float potential. The resistor divider is disconnected in sleep mode to reduce the current drain on the battery. SEL (Pin 2): 4.1V/4.2V Battery Selection Input Pin. Grounding this pin will set the output float voltage to 4.1V per cell, while connecting to VCC will set the voltage to 4.2V per cell. For the LTC1732-4.2, the SEL pin must be connected to VCC. CHRG (Pin 3): 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 more than 15ms, the N-channel MOSFET turns off and a 35µA 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 4): 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 (hours) = (CTIMER • 3 hours)/(0.1µF). When the TIMER pin is connected to VCC, the timer is disabled, the constantvoltage mode is disabled and the chip will operate in constant-current mode only. Shorting the TIMER pin to GND will disable the internal timer function and the C/10 function. GND (Pin 5): Ground. PROG (Pin 6): 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 7): Drive Output Pin for the P-Channel MOSFET or PNP Transistor. If a PNP pass transistor is used, select a high beta transistor to minimize the charge current error due to the base current. VCC (Pin 8): Positive Input Supply Voltage. When VBAT is within 54mV of VCC, the LTC1732 is forced into sleep mode, dropping ICC to 7µA. VCC ranges from 4.5V to 12V. Bypass this pin with a 1µF capacitor. SENSE (Pin 9): 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 • 800Ω)/(RPROG • IBAT) ACPR (Pin 10): Wall Adapter Present Output. When the input voltage (wall adapter) greater than the undervoltage lockout threshold is applied to the LTC1732, this pin is pulled to ground by an internal N-channel MOSFET that is capable of sinking 5mA to drive an external LED. 5 LTC1732-4/LTC1732-4.2 W BLOCK DIAGRA VCC 8 3.8V (LTC1732-4) 4.05V (LTC1732-4.2) + UNDERVOLTAGE LOCKOUT VUV = 4.1V C5 – RSENSE SENSE + 3 + – 800Ω 80Ω C1 – CHRG 9 54mV + C4 – – C/10 STOP UVLO RECHRG C/10 + SHDN 4 TIMER 720Ω LOGIC DRV CA SLP OSCILLATOR BAT LBO COUNTER 1 C2 SEL VREF 2 – ACPR + + C3 – VA VCC A1 – + 10 7 + ACPR – 35µA 2.5µA VREF 2.457V CHARGE 6 BATTERY CURRENT IBAT = (2.457V • 800Ω)/(RPROG • RSENSE) 6 PROG RPROG GND 5 1732 BD LTC1732-4/LTC1732-4.2 U OPERATIO The LTC1732 is a linear battery charger controller. 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 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 on the 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 terminate. 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. 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 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 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 LTC1732 can function as a current source by pulling the TIMER pin to VCC. When in the constant-current only mode, the voltage amplifier, timer, C/10 comparator 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 this pin high and clamp it at 3.5V. When the input voltage is not present, the charger goes into a sleep mode, dropping ICC to 7µA. This greatly reduces the current drain on the battery and increases the standby time. 7 LTC1732-4/LTC1732-4.2 U W U U APPLICATIONS INFORMATION Charger Conditions The charger is off when any of the following conditions exist: the VCC pin voltage is less than 4.1V, the dropout voltage (VCC – VBAT) is less than 54mV, or if the program resistor is floating. The DRV pin is pulled up to VCC thus keeping the MOSFET off, and the internal resistor divider is disconnected to reduce the 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 200mV of hysteresis. Trickle Charge and Defective Battery Detection At the beginning of the charging sequence, if the battery voltage is below 2.457V, the charger goes into trickle mode. The charge current is dropped 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, the charging will be terminated and the CHRG pin output is forced to a high impedance state. Shutdown The LTC1732 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 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 = 2.457V 800Ω • RPROG 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 = 0.2Ω, then calculate: 8 RPROG = (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 cycle. The length of the timer is programmed by an external capacitor at the TIMER pin. The total charge time is: Time = (3 Hours)(CTIMER/0.1µF) The timer starts when an 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 disable only the timer function, short the TIMER pin to GND. Battery Detection and Recharge LTC1732-4: replacing the battery before the timer has expired will reset the timer, thus starting a new charge cycle, provided the cell voltage of the new battery is less than 3.8V. If the new battery is greater than 3.8V, the timer will not be reset and charging will continue for the remaining portion of the time period. Replacing the battery after the timer has expired will start a new charge cycle, regardless of the battery voltage, provided the previous battery voltage exceeded 3.9V before the timer expired. After a complete charge cycle has occurred (VBAT > 3.9V), and the battery remains connected to the charger, a new charge cycle will begin if the battery voltage drops below 3.8V because of a load on the battery or self discharge. LTC1732-4.2: replacing the battery before the timer has expired will reset the timer, thus starting a new charge cycle, provided the cell voltage of the new battery is less than 4.05V. If the new battery is greater than 4.05V, the timer will not be reset and charging will continue for the remaining portion of the time period. Replacing the battery after the timer has expired will start a new charge cycle, regardless of the battery voltage, provided the previous battery voltage exceeded 4.1V before the timer expired. LTC1732-4/LTC1732-4.2 U W U U APPLICATIONS INFORMATION After a complete charge cycle has occured (VBAT > 4.1V), and the battery remains connected to the charger, a new charge cycle will begin if the battery voltage drops below 4.05V because of a load on the battery or self discharge. For either version, to force a new charge cycle, regardless of previous conditions, momentarily lift the program resistor or remove and reapply the input power. 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 35µA current source to ground is connected to the CHRG pin. A 15ms time delay is included to help prevent false triggering due to transient currents. The end-of-charge comparator is disabled in trickle charge mode. After the timer expires, the charge cycle ends, and the pin goes into a high impedance state. The timer is used to terminate the charge cycle. 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 8 VCC 400k LTC1732 CHRG 3 µPROCESSOR forcing the OUT pin into a high impedance state, the current source will pull the pin low through the 400k resistor. When the internal timer has expired, the CHRG pin will change to high impedance state and the 400k resistor will then pull the pin high to indicate the charging has stopped. ACPR Output Pin The LTC1732 has an ACPR output pin to indicate that the input supply (wall adapter) is higher than 4.1V and 54mV above the voltage at the BAT pin. When both conditions are met, the ACPR pin is pulled down to ground by an N-channel MOSFET that is capable of driving an LED. Otherwise, this pin is in a high impedance state. End of Charge (C/10) Output The LTC1732 includes a comparator to monitor the charge current to detect an end-of-charge condition. This comparator does not terminate the charge cycle, but provides an 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 35µA current source to ground. A 15ms time delay is included to help prevent false triggering due to transient currents. The end-of-charge comparator is disabled in trickle charge mode. 2k OUT Output Voltage Selection IN 1732 F01 Figure 1. Microprocessor Interface When the LTC1732 is in charge mode, the CHRG pin is pulled low by the 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 35µA current source is connected to the CHRG pin. The IN pin will then be pulled high by the 2k pull-up. By The float voltage at the BAT pin can be selected by the SEL pin. Shorting the SEL pin to ground will set the float voltage to 4.1V, while connecting it to VCC sets it to 4.2V. This feature allows the charger to be used with different types of Li-Ion cells. When charging 4.1V cells, use the LTC1732-4 with the SEL pin grounded. The LTC1732-4 can also be used for charging 4.2V cells by connecting the SEL pin to VCC. The recharge threshold level is preset to 3.8V, thus allowing either 4.1V or 4.2V cells to be charged. Because the recharge threshold voltage level of the LTC1732-4.2 is preset for 4.05V, this version is not recommended for 4.1V cells. 9 LTC1732-4/LTC1732-4.2 U U W U APPLICATIONS INFORMATION Gate Drive Typically the LTC1732 controls an external P-channel MOSFET to supply current to the battery. An external PNP transistor can also be used as the pass transistor instead of the P-channel MOSFET. Due to the low transconductance of the current amplifier (CA), a high gain Darlington PNP transistor is required to avoid excessive charge current error. The transconductance 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 RPROG = 19.6k (100mV across RSENSE). This represents a 1.6% error in charge current. Constant-Current Only Mode The LTC1732 can be used as a programmable current source by connecting 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 charging by floating the PROG pin. Stability The charger is stable without any compensation when a P-channel MOSFET is used as the pass transistor and the battery is present. A 10µF tantalum 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. If a PNP transistor is used for the pass transistor, a 1000pF capacitor is required from the DRV pin to VCC. To help stablize the voltage loop a 10µF tantalum capacitor at the BAT pin is also recommended when a battery is not present. U TYPICAL APPLICATIO S Li-Ion Linear Charger Using a PNP Transistor VIN = 6V MBRM120T3 R1 1k R2 1k C1 1nF 8 3 10 VCC CHRG SENSE ACPR DRV CTIMER 0.1µF TIMER BAT PROG SEL GND 2 5 RSENSE 0.2Ω C3 1µF Q2 ZTX749 9 7 Q1 2N5087 LTC1732-4 4 R3 10k IBAT = 500mA 1 6 RPROG 19.6k C2 10µF + 4.1V Li-Ion CELL 1732 TA02 10 LTC1732-4/LTC1732-4.2 U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. MS10 Package 10-Lead Plastic MSOP (LTC DWG # 05-08-1661) 0.118 ± 0.004* (3.00 ± 0.102) 10 9 8 7 6 0.118 ± 0.004** (3.00 ± 0.102) 0.193 ± 0.006 (4.90 ± 0.15) 1 2 3 4 5 0.034 (0.86) REF 0.043 (1.10) MAX 0.007 (0.18) 0° – 6° TYP 0.021 ± 0.006 (0.53 ± 0.015) SEATING PLANE 0.007 – 0.011 (0.17 – 0.27) 0.0197 (0.50) BSC 0.005 ± 0.002 (0.13 ± 0.05) MSOP (MS10) 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 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 LTC1732-4/LTC1732-4.2 U TYPICAL APPLICATIO Single Cell 4.1V, High Efficiency 1.5A Li-Ion Battery Charger VIN 6V D2 MBRS130LT3 1k R1 1k 8 3 10 VCC CHRG SENSE ACPR DRV 9 C1 0.1µF TIMER BAT PROG SEL GND 2 5 R3 0.082Ω 1/4W R2 4.7Ω 7 1 LTC1693-5 4 LTC1732-4 4 + C4 0.47µF 2 8 7 C2 22µF D1 Q2 MBRS130LT3 Si2305DS 1 15µH CDRH6D28-150NC 6 R4 19.6k + 1-CELL Li-Ion BATTERY + C3 220µF 1732 TA03 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 LTC1541 Op Amp, Comparator and Reference with 5µA ICC Low Cost Linear Charger—See Design Note 188 LT1620 Rail-to-Rail Current Sense Amplifier Precise Output Current Programming, Up to 32V VOUT, Up to 10A IOUT LTC1729 Termination Controller for Li-Ion Time or Charge Current Termination, Automatic Charger/Battery Detection, Status Output, Preconditioning, 8-Lead MSOP LTC1730 Li-Ion Pulse Charger Minimum Heat Dissipation; No Reverse Current Diode Needed; No MOSFET Required; Limits Charge Current for Safety LTC1734 ThinSOTTM Li-Ion Linear Battery Charger Only Two External Components; Charge Termination and Gas Gauging Provided by Monitoring VPROG Pin. ThinSOT is a trademark of Linear Technology Corporation. 12 Linear Technology Corporation sn1732 1732fs LT/TP 0501 2K • PRINTED IN THE USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com LINEAR TECHNOLOGY CORPORATION 2000 LTC1732-8.4 Lithium-Ion Linear Battery Charger Controller U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Complete Linear Charger Controller for 2-Cell Lithium-Ion Batteries Preset Charge Voltage with ±1% Accuracy Programmable Charge Current C/10 Charge Current Detection Output Programmable Charge Termination Timer Small, Thin 10-Pin MSOP Package Input Supply (Wall Adapter) Detection Output 8.8V to 12V Input Voltage Range Automatic Sleep Mode When Input Supply Is Removed (Only 10µA Battery Drain) Automatic Trickle Charging of Low Voltage Cells Programmable for Constant-Current-Only Mode Battery Insertion Detect and Automatic Charging of Low-Battery Automatic Battery Recharge U APPLICATIO S ■ ■ ■ ■ The LTC ®1732-8.4 is a complete constant-current/constant-voltage linear charge controller for lithium-ion (Li-Ion) batteries. Nickel-cadmium (NiCd) and nickel metalhydride (NiMH) batteries can also be charged with constant current using external termination. Charge current can be programmed with ±7% accuracy using external sense and program resistors. An internal resistor divider and precision reference set the final float voltage with ±1% accuracy. When the input supply is removed, the LTC1732-8.4 automatically enters a low current sleep mode, dropping the battery drain current to 10µA. 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 4.9V. The LTC1732-8.4 begins a new charge cycle when a discharged battery is connected to the charger or when the input power is applied. In additon, if the battery remains connected to the charger and the cell voltage drops below 8.05V, a new charge cycle will begin. Cellular Phones Handheld Computers Charging Docks and Cradles Digital Cameras and Camcorders The LTC1732-8.4 is available in the 10-pin MSOP package. , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATIO 400mA 2-Cell 8.4V Li-Ion Battery Charger Typical Li-Ion Charge Cycle VIN = 10V CONSTANT CURRENT R2 1k 2 8 SEL VCC SENSE 3 DRV CHRG RSENSE 0.25Ω 9 7 Q1 Si9430DY LTC1732-8.4 10 4 CTIMER 0.1µF ACPR BAT TIMER PROG GND 5 1µF IBAT = 400mA 1 6 RPROG* 19.6k 10µF *SHUTDOWN INVOKED BY FLOATING THE PROG PIN + 8.4V Li-Ion BATTERY 1732-8.4 TA01 9 CONSTANT VOLTAGE BATTERY VOLTAGE 400 8 400mA HR BATTERY 300 CHARGE CURRENT 200 CHRG LED OFF 100 0 0 0.5 2.0 1.5 1.0 TIME (HOURS) 7 BATTERY VOLTAGE(V) R1 1k CHARGE CURRENT (mA) MBRM120T3 TIMER STOPS 2.5 6 3.0 1732-8.4 TA01b 17328f 1 LTC1732-8.4 W U U U W W W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) Input Supply Voltage (VCC) ................................... 13.2V SENSE, DRV, BAT, SEL, TIMER, PROG, CHRG, ACPR ................. – 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 ORDER PART NUMBER TOP VIEW BAT SEL CHRG TIMER GND 1 2 3 4 5 10 9 8 7 6 ACPR SENSE VCC DRV PROG LTC1732EMS-8.4 MS10 PART MARKING MS10 PACKAGE 10-LEAD PLASTIC MSOP LTWW TJMAX = 140°C, θJA = 180°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 CONDITIONS MIN VCC Input Supply Voltage ICC Input Supply Current Charger On, Current Mode Shutdown Mode Sleep Mode (Battery Drain Current) ● ● VBAT Regulated Output Float Voltage 9V ≤ VCC ≤ 12V, VSEL = VCC ● 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 10 3 3 30 mA mA µA 8.316 8.4 8.484 465 415 500 535 585 mA mA 60 100 140 mA V ITRIKL Trickle Charge Current VBAT = 4V, RPROG = 19.6k, ITRIKL = (VCC – VSENSE)/0.2Ω ● 30 50 125 mA VTRIKL Trickle Charge Threshold Voltage From Low to High ● 4.7 4.9 5.1 V VUV VCC Undervoltage Lockout Voltage From Low to High ● 8.2 8.7 V ∆VUV VCC Undervoltage Lockout Hysteresis VMSD Manual Shutdown Threshold Voltage PROG Pin Low to High PROG Pin High to Low VASD Automatic Shutdown Threshold Voltage (VCC – VBAT) High to Low (VCC – VBAT) Low to High VDIS Voltage Mode Disable Threshold Voltage VDIS = VCC – VTIMER IPROG PROG Pin Current Internal Pull-Up Current, No RPROG PROG Pin Source Current, ∆VPROG ≤ 5mV 400 VPROG PROG Pin Voltage RPROG =19.6k VACPR ACPR Pin Output Low Voltage IACPR = 5mA ICHRG CHRG Pin Weak Pull-Down Current VCHRG = 1V VCHRG CHRG Pin Output Low Voltage IDRV Drive Pin Current mV 2.457 2.446 30 40 54 69 V V 90 100 mV mV 0.4 V 300 µA µA 2.5 ● 2.457 V 0.6 1.2 V 35 55 µA ICHRG = 5mA 0.6 1.2 V VDRV = VCC – 2V 26 15 µA 17328f 2 LTC1732-8.4 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 MIN IC/10 10% Charge Current Indication Level RPROG = 19.6k, RSENSE = 0.2Ω tTIMER TIMER Accuracy CTIMER = 0.1µF VRECHRG Recharge Threshold Voltage VBAT from High to Low Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. ● 25 7.85 TYP MAX UNITS 50 100 mA 10 % 8.05 V Note 2: The LTC1732EMS-8.4 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. U W TYPICAL PERFOR A CE CHARACTERISTICS Trickle Charge Current vs Temperature 60 60 RPROG = 19.6K RSENSE = 0.2Ω VBAT = 4V TA = 25° 55 ITRKL (mA) ITRKL (mA) 55 50 Trickle Charge Threshold Voltage vs VCC 4.96 RPROG = 19.6K RSENSE = 0.2Ω VBAT = 4V VCC = 9V RPROG = 19.6K TA = 25° 4.95 4.94 VTRKL (V) Trickle Charge Current vs VCC 50 4.93 4.92 4.91 45 45 4.90 4.89 40 9 10 11 12 40 –50 –25 0 25 50 75 100 125 1732-8.4 G01 9 10 11 12 VCC (V) TEMPERATURE (°C) VCC (V) 4.88 1732-8.4 G02 1732-8.4 G03 17328f 3 LTC1732-8.4 U W TYPICAL PERFOR A CE CHARACTERISTICS Trickle Charge Threshold Voltage vs Temperature 110 110 VCC = 9V 4.93 CTIMER = 0.1µF VCC = 9V CTIMER = 0.1µF VBAT = 6V TA = 25° 105 4.92 4.91 tTIMER (%) 105 tTIMER (%) VTRKL (V) Timer Accuracy vs Temperature Timer Accuracy vs VCC 4.94 100 95 95 4.90 –50 –25 25 0 50 75 100 90 125 9 10 11 25 75 50 Battery Charge Current vs Temperature 540 530 IBAT (mA) 520 500 RPROG = 19.6K RSENSE = 0.2Ω VBAT = 6V VCC = 9V RPROG = 19.6K VBAT = 6V TA = 25° 2.47 510 500 490 480 490 125 Program Pin Voltage vs VCC 2.48 VPROG (V) RPROG = 19.6K RSENSE = 0.2Ω VBAT = 6V TA = 25° 100 1732-8.4 G06 1732-8.4 G05 Battery Charge Current vs VCC 510 0 TEMPERATURE (°C) 1732-8.4 G04 520 90 –50 –25 12 VCC (V) TEMPERATURE (°C) IBAT (mA) 100 2.46 2.45 470 480 9 10 11 460 –50 –25 12 VCC (V) 0 25 50 75 100 2.44 9 10 11 12 VCC (V) TEMPERATURE (°C) 1732-8.4 G08 1732-8.4 G07 Program Pin Voltage vs Temperature 1732-8.4 G09 Recharge Threshold Voltage vs Temperature 8.25 2.470 VCC = 9V RPROG = 19.6k VCC = 9V 8.15 VRECHRG (V) 2.465 VPROG (V) 125 2.460 7.95 2.455 2.450 –50 –25 8.05 0 25 50 75 100 125 7.85 –50 –25 0 25 50 75 100 125 TEMPERATURE (°C) TEMPERATURE (°C) 1732-8.4 G10 1732-8.4 G11 17328f 4 LTC1732-8.4 U U U PIN FUNCTIONS BAT (Pin 1): Battery Sense Input. A bypass capacitor of 10µF or more is required to keep the loop stable when the battery is not connected. A precision internal resistor divider sets the final float voltage. The resistor divider is disconnected in sleep mode to reduce the current drain on the battery. SEL (Pin 2): This pin must be connected to VCC. CHRG (Pin 3): Open-Drain Charge Status Output. When the battery is charging, 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 more than 15ms, the N-channel MOSFET turns off and a 35µA current source is connected from the CHRG pin to GND. When the timer runs out or the input supply is removed, the current source is disconnected and the CHRG pin is forced into a high impedance state. TIMER (Pin 4): 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 timer is disabled, thus the constantvoltage mode is turned off and the IC will operate in constant-current mode only. Shorting the TIMER pin to GND will disable the internal timer function and the C/10 function. PROG (Pin 6): 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 7): 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). VCC (Pin 8): Input Supply Voltage. VCC can range from 8.8V to 12V. 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 9): 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 • 800Ω)/(RPROG • IBAT) ACPR (Pin 10): Wall Adapter Present Output. When the input voltage (wall adapter) is applied to the LTC1732-8.4, this pin is pulled to ground by an internal N-channel MOSFET which is capable of sinking 5mA to drive an external LED (See Applications Information Section). GND (Pin 5): Ground. 17328f 5 LTC1732-8.4 W BLOCK DIAGRA VCC 8 + UNDERVOLTAGE LOCKOUT VCC = 8.2V 8.05V C5 – RSENSE SENSE + 3 + – 800Ω 80Ω C1 – CHRG 9 54mV + C4 – – C/10 STOP RECHRG C/10 + TIMER DRV CA SLP OSCILLATOR BAT LBO COUNTER 1 4.9V SEL* VREF 2 – ACPR + + C3 A1 – VA VCC – + 10 7 C2 + SHDN 4 720Ω UVLO ACPR – 35µA VREF 2.457V 2.5µA CHARGE 6 BATTERY CURRENT IBAT = (2.457V • 800Ω)/(RPROG • RSENSE) PROG GND 5 1732-8.4 BD RPROG *THE LTC1732-8.4 IS OPTIMIZED FOR 2-CELL (8.4V) Li-Ion BATTERIES. CONNECT THE SEL PIN TO VCC. FOR CHARGING 8.2V BATTERIES USING THE LTC1732, PLEASE CONTACT THE FACTORY 17328f 6 LTC1732-8.4 U OPERATIO The LTC1732-8.4 is a linear battery charger controller. 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 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 voltage 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. A charge cycle 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 4.9V, the charger goes into trickle charge mode. The trickle charge current is 10% of the full-scale current. If the battery 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 4.9V. 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 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 charge cycle is terminated and the CHRG pin is forced to a high impedance state. To restart the charge cycle, remove the input voltage and reapply it, or float the PROG pin momentarily. Replacing the battery while in the charge mode will cause the timer to be reset if the voltage of the new battery is below 8.05V. If the voltage is above 8.05V, the timer will continue for the remaining charge time. In the case when a time out has occurred, a new battery with a voltage of less than 8.05V can be inserted and charged automatically with the full programmed charge time. For batteries like lithium-ion that require accurate final float voltage, the internal 2.457V reference, voltage amplifier and the resistor divider provide regulation with ±1% (max) accuracy. For NiMH and NiCd batteries, the LTC1732-8.4 can be used as a current source by pulling the TIMER pin to VCC. When in the constant-current only mode, the voltage amplifier, timer, C/10 comparator 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 this pin high and clamp it at 3.5V. When the input voltage is not present, the charger goes into a sleep mode, dropping ICC to 10µA. This greatly reduces the current drain on the battery and increases the standby time. 17328f 7 LTC1732-8.4 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 dropout voltage (VCC – VBAT) is less than 54mV, 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 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 below 4.9V, the charger goes into trickle mode. The charge current drops to 10% of the full-scale current. If the low voltage persists for one quarter of the total charge time, the battery is considered defective, the charge cycle is terminated and the CHRG pin output is forced to a high impedance state. Shutdown The LTC1732-8.4 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 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 = (IPROG)(800Ω/RSENSE) = (2.457V/RPROG)(800Ω/RSENSE) or RPROG = (2.457V/IBAT)(800Ω/RSENSE) 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 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 terminates the charge cycle. Typically, when charging at a 1C rate, a discharged Li-Ion battery will become fully charged in 3 hours. For lower charge current rates, extend the timer accordingly.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) or CTIMER = 0.1µF • Time (Hours)/3 (Hours) The timer starts when an 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 go into a high impedance state to indicate that 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 a charge cycle starts, the CHRG pin is pulled 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 35µA 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 pullup resistors, a microprocessor can detect three states from this pin (charging, C/10 and stop charging). See Figure 1 and Table 1. where RPROG is the total resistance from the PROG pin to ground. 17328f 8 LTC1732-8.4 U U W U APPLICATIONS INFORMATION V+ VDD 8 VCC 400k CHRG 3 µPROCESSOR 2k LTC1732-8.4 OUT IN 1732-8.4 F01 Figure 1. Microprocessor Interface Table 1. Microprocessor Interface IN OUT CHARGE STATUS LOW HIGH Charge LOW Hi-Z C/10 HIGH Hi-Z Stop Charging When the LTC1732-8.4 is in charge mode, the CHRG pin is pulled low 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 35µA current source is connected to the CHRG pin. The IN pin is then pulled high by the 2k pull-up. By forcing the OUT pin into a high impedance state, the current source pulls the pin low through the 400k resistor. When the internal timer has expired, the CHRG pin changes to high impedance and the 400k resistor pulls the pin high to indicate that charging has stopped. ACPR Output Pin The LTC1732-8.4 has an ACPR output pin to indicate that the input supply (wall adapter) is higher than 8.2V and 55mV above the voltage at the BAT pin. When both conditions are met, the ACPR pin is pulled to ground by an N-channel MOSFET that is capable of driving an LED. Otherwise, this pin is high impedance. CHRG Status Output Pin (C/10) The LTC1732-8.4 includes 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 an 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 35µA current source to ground. After an internal time delay of 15ms, this state is latched. This delay helps prevent false triggering due to transient currents. The end-of-charge comparator is disabled in trickle charge mode. Gate Drive Typically the LTC1732-8.4 controls an external P-channel MOSFET to supply current to the battery. 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 RPROG = 19.6k (100mV across RSENSE), it represents 1.67% of error in charging current. 17328f 9 LTC1732-8.4 U W U U APPLICATIONS INFORMATION Constant-Current Only Mode VCC Bypass Capacitor The LTC1732-8.4 can be used as a programmable current source by connecting 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. Many types of capacitors can be used for input bypassing. However, caution must be exercised when using multilayer ceramic capacitors. Because of the self resonant and high Q characteristics of some types of ceramic capacitors, high voltage transients can be generated under some start-up conditions, such as connecting the charger input to a hot power source. To minimize these transients, only ceramic capacitors with X5R or X7R dielectric are recommended. Also, adding 1Ω or 2Ω in series with the ceramic capacitor will further reduce these start-up transients. For more information refer to Application Note 88. Battery Detection The LTC1732-8.4 can detect the insertion of a new battery. When a battery with voltage of less than 8.05V is inserted, the LTC1732-8.4 resets the timer and a new charge cycle begins. If the voltage of the new battery is above 8.05V, the charging will not start if the TIMER has already timed out. If a new battery (with a voltage above 8.05V) is inserted while in the charging process, the timer will not be reset and charging will continue until the timer runs out. After a time out has occurred and the battery remains connected, a new charge cycle will begin if the battery voltage drops below 8.05V due to self-discharge or external loading. 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. If a PNP transistor is used for 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. 17328f 10 LTC1732-8.4 U PACKAGE DESCRIPTIO MS Package 10-Lead Plastic MSOP (Reference LTC DWG # 05-08-1661) 0.889 ± 0.127 (.035 ± .005) 5.23 (.206) MIN 3.2 – 3.45 (.126 – .136) 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 0.50 3.05 ± 0.38 (.0197) (.0120 ± .0015) BSC TYP RECOMMENDED SOLDER PAD LAYOUT WITHOUT EXPOSED PAD OPTION 0.254 (.010) 10 9 8 7 6 3.00 ± 0.102 (.118 ± .004) NOTE 4 4.88 ± 0.10 (.192 ± .004) DETAIL “A” 0.497 ± 0.076 (.0196 ± .003) REF 0° – 6° TYP GAUGE PLANE 1 2 3 4 5 0.53 ± 0.01 (.021 ± .006) DETAIL “A” 0.86 (.034) REF 1.10 (.043) MAX 0.18 (.007) SEATING PLANE 0.17 – 0.27 (.007 – .011) 0.50 (.0197) TYP 0.13 ± 0.05 (.005 ± .002) MSOP (MS) 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 17328f 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 LTC1732-8.4 U TYPICAL APPLICATIO 2-Cell 8.4V Linear Charger Using a PNP Pass Transistor VIN = 10V MBRM120T3 R2 2k CHARGE STATUS 2k 2 3 10 SEL VCC 9 CHRG SENSE LTC1732-8.4 7 DRV R1 10k RSENSE 0.25Ω TIMER CTIMER* 0.1µF PROG C3 1µF Q2 ZTX749 Q1 2N5087 ACPR BAT 4 C1 1nF 8 IBAT = 400mA 1 6 GND RPROG 19.6k 5 *AVX 0603ZC104KAT1A + 2-CELL Li-ION C2 10µF 1732 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 LTC1571-1/ LTC1571-2/ LTC1571-5 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 LT1620 Rail-to-Rail Current Sense Amplifier Precise Output Current Programming, Up to 32VOUT, Up to 10A IOUT LTC1729 Termination Controller for Li-Ion Time or Charge Current Termination, Automatic Charger/Battery Detection, Status Output, Preconditioning, 8-Lead MSOP LTC1730/ LTC4052 Complete Li-Ion Pulse Battery Charger with Internal FET and Thermal Regulation Efficient 1.5A Charger with Many Features Including Overcurrent Battery Protection LTC1731 Complete Li-Ion Linear Battery Charger Controller Single Cell and 2-Cell Li-Ion, C/10 Detection, Complete Charger LTC1732-4/ LTC1732-4.2 Complete Linear Battery Charger Controller for Single Cell Li-Ion Battery No Firmware Required, AC Adapter Indicator Automatic Charge and Recharge LTC1733 CompleteLi-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/ LTC1734L ThinSOT Li-Ion Linear Charger Only Two External Components, VPROG Tracks ICHARGE No Diode Needed, No Sense Resistor Needed, 50mA to 700mA Charge Current LTC4050 Complete Li-Ion Linear Charger with Thermistor Interface No Firmware Required, AC Adapter Indicator Automatic Charge and Recharge LTC4053 USB Compatible Li-Ion Linear Battery Charger Operate from Wall Adapter Input and/or USB Input, 100mA/500mA up to 1.25A Charge Current, Thermal Limit Prevent Over Heating, Standalone Charger. LTC4412 Low Loss PowerPathTM Controller in ThinSOTTM Automatic Switching Between DC Sources, Load Sharing, Replaces ORing Diodes ThinSot and PowerPath are trademarks of Linear Technology Corporation. 17328f 12 Linear Technology Corporation LT/TP 0203 2K • PRINTED IN THE USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2001