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| LTC4065/LTC4065A Standalone 750mA Li-Ion Battery Charger in 2 x 2 DFN FEATURES DESCRIPTIO Complete Linear Charger in 2mm x 2mm DFN Package C/10 Charge Current Detection Output Timer Termination Charge Current Programmable up to 750mA with 5% Accuracy No External MOSFET, Sense Resistor or Blocking Diode Required Preset 4.2V Float Voltage with 0.6% Accuracy Constant-Current/Constant-Voltage Operation with Thermal Feedback to Maximize Charging Rate Without Risk of Overheating ACPR Pin Indicates Presence of Input Supply (LTC4065A Only) Charge Current Monitor Output for Gas Gauging Automatic Recharge Charges Single Cell Li-Ion Batteries Directly from USB Port 20A Supply Current in Shutdown Mode Soft-Start Limits Inrush Current Tiny 6-Lead (2mm x 2mm) DFN Package The LTC(R)4065 is a complete constant-current/constantvoltage linear charger for single-cell lithium-ion batteries. Its 2mm x 2mm DFN package and low external component count make the LTC4065 especially well-suited for portable applications. Furthermore, LTC4065 is specifically designed to work within USB power specifications. The CHRG pin indicates when charge current has dropped to ten percent of its programmed value (C/10). An internal timer terminates charging according to battery manufacturer specifications. No external sense resistor or blocking diode is required due to the internal MOSFET architecture. Thermal feedback regulates charge current to limit the die temperature during high power operation or high ambient temperature conditions. When the input supply (wall adapter or USB supply) is removed, the LTC4065 automatically enters a low current state, dropping battery drain current to less than 1A. With power applied, LTC4065 can be put into shutdown mode, reducing the supply current to less than 20A. The full-featured LTC4065 also includes automatic recharge, low-battery charge conditioning (trickle charging), soft-start (to limit inrush current) and an open-drain status pin to indicate the presence of an adequate input voltage (LTC4065A only). The LTC4065 is available in a tiny 6-lead, low profile (0.75mm) 2mm x 2mm DFN package. APPLICATIO S Wireless PDAs Cellular Phones Portable Electronics , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATIO VIN 4.3V TO 5.5V C1 1F R2* 1 VCC R1 510 Standalone Li-Ion Battery Charger 500mA BAT LTC4065 CHRG PROG EN GND + R3 2k 4.2V Li-Ion BATTERY 4065 TA01 *SERIES 1 RESISTOR ONLY NEEDED FOR INDUCTIVE INPUT SUPPLIES 4065f U U U 1 LTC4065/LTC4065A ABSOLUTE (Note 1) AXI U RATI GS PACKAGE/ORDER I FOR ATIO TOP VIEW GND 1 CHRG 2 BAT 3 7 6 PROG 5 EN/ACPR* 4 VCC VCC t < 1ms and Duty Cycle < 1% ................. - 0.3V to 7V Steady State ........................................... - 0.3V to 6V BAT, CHRG ................................................. -0.3V to 6V EN (LTC4065), ACPR (LTC4065A) .. -0.3V to VCC + 0.3V PROG.............................................. -0.3V to VCC + 0.3V BAT Short-Circuit Duration ...........................Continuous BAT Pin Current ................................................. 800mA PROG Pin Current ............................................... 800A Junction Temperature (Note 6) ............................ 125C Operating Temperature Range (Note 2) .. - 40C to 85C Storage Temperature Range ................ - 65C to 125C DC PACKAGE 6-LEAD (2mm x 2mm) PLASTIC DFN TJMAX = 125C, JA = 102C/W (NOTE 3) EXPOSED PAD (PIN 7) IS GND, MUST BE SOLDERED TO PCB *EN PIN 5 ON LTC4065EDC, ACPR PIN 5 ON LTC4065AEDC ORDER PART NUMBER LTC4065EDC LTC4065AEDC DC PART MARKING LBPG LBVJ Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25C. VCC = 5V, VBAT = 3.8V, VEN = 0V (LTC4065 only) unless otherwise specified. (Note 2) SYMBOL VCC ICC ICCMS ICCUV VFLOAT IBAT IBMS IBUV VUVLO VPROG VASD VMSH VMSL REN PARAMETER VCC Supply Voltage Quiescent VCC Supply Current VCC Supply Current in Shutdown VCC Supply Current in Undervoltage Lockout VBAT Regulated Output Voltage BAT Pin Current Battery Drain Current in Shutdown Mode CONDITIONS (Note 4) VBAT = 4.5V (Forces IBAT and IPROG = 0) VEN = 5V (LTC4065) or Float PROG (LTC4065A) VCC < VBAT, VCC = 3.5V, VBAT = 4V IBAT = 2mA IBAT = 2mA, 0C < TA < 85C RPROG = 10k (0.1%), Current Mode RPROG = 2k (0.1%), Current Mode VEN = VCC (LTC4065), VPROG > VMS,PROG (LTC4065A) MIN 3.75 TYP 120 20 6 MAX 5.5 250 40 11 4.225 4.242 112 525 1 4 3.8 3.2 1.02 1.02 100 45 1 UNITS V A A A V V mA mA A A V V V V mV mV V V 4.175 4.158 88 475 -1 0 3.4 2.8 0.98 0.98 60 15 4.2 4.2 100 500 0 1 3.6 3.0 1 1 82 32 Battery Drain Current in Undervoltage VCC = 3.5V, VBAT = 4V Lockout VCC Undervoltage Lockout Voltage PROG Pin Voltage Automatic Shutdown Threshold Voltage Manual Shutdown High Voltage (LTC4065) Manual Shutdown Low Voltage (LTC4065) EN Pin Input Resistance VCC Rising VCC Falling RPROG = 2k, IPROG = 500A RPROG = 10k, IPROG = 100A (VCC - VBAT), VCC Low to High (VCC - VBAT), VCC High to Low VEN Rising VEN Falling 0.6 0.95 1.5 3.3 2 U M 4065f W U U WW W LTC4065/LTC4065A ELECTRICAL CHARACTERISTICS The denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25C. VCC = 5V, VBAT = 3.8V, VEN = 0V (LTC4065 only) unless otherwise specified. (Note 2) SYMBOL IPROG VMS,PROG tSS ITRKL VTRKL VTRHYS VRECHRG VUVCL1 VUVCL2 tTIMER PARAMETER PROG Pin Pull-Up Current (LTC4065A) PROG Shutdown Threshold Voltage (LTC4065A Only) Soft-Start Time Trickle Charge Current Trickle Charge Threshold Voltage Trickle Charge Hysteresis Voltage Recharge Battery Threshold Voltage (VCC - VBAT) Undervoltage Current Limit Termination Timer Recharge Time Low-Battery Trickle Charge Time VACPR IACPR VCHRG ICHRG IC/10 TLIM RON fBADBAT DBADBAT ACPR Pin Output Low Voltage (LTC4065A) ACPR Pin Input Current (LTC4065A) CHRG Pin Output Low Voltage CHRG Pin Input Current End of Charge Indication Current Level Junction Temperature in Constant Temperature Mode Power FET "ON" Resistance (Between VCC and BAT) Defective Battery Detection CHRG Pulse Frequency Defective Battery Detection CHRG Pulse Frequency Duty Ratio IBAT = 200mA VBAT = 2.5V IACPR = 5mA VCC = 4V, VACPR = 4V, VBAT = 4.5V ICHRG = 5mA VBAT = 4.5V, VCHRG = 5V RPROG = 2k (Note 5) VFLOAT - VRECHRG, 0C < TA < 85C IBAT = 90% Programmed Charge Current IBAT = 10% Programmed Charge Current CONDITIONS VPROG > 1V VPROG Rising MIN TYP 3 MAX UNITS A 3.7 4 180 4.3 V s VBAT = 2V, RPROG = 2k (0.1%) VBAT Rising 35 2.7 70 180 90 3 1.5 0.75 50 2.9 90 100 220 125 4.5 2.25 1.125 60 0 60 0 65 3.05 130 330 150 6 3 1.5 105 1 105 1 0.115 mA V mV mV mV mV Hrs Hrs Hrs mV A mV A mA/mA C m Hz % 0.085 0.1 115 450 2 80 Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LTC4065/LTC4065A are guaranteed to meet performance specifications from 0C to 70C. Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: Failure to solder the exposed backside of the package to the PC board ground plane will result in a thermal resistance much higher than 102C/W. Note 4: Although the LTC4065 functions properly at 3.75V, full charge current requires an input voltage greater than the desired final battery voltage per the VUVCL1 specification. Note 5: IC/10 is expressed as a fraction of measured full charge current with indicated PROG resistor. Note 6: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed 125C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. 4065f 3 LTC4065/LTC4065A TYPICAL PERFOR A CE CHARACTERISTICS Battery Regulation (Float) Voltage vs Battery Charge Current 4.24 4.23 4.22 VFLOAT (V) VCC = 5V TA = 25C RPROG = 2k 4.24 4.23 4.22 VFLOAT (V) 4.20 4.19 4.18 4.17 4.16 0 100 200 300 IBAT (mA) 400 500 4065 G01 4.20 4.19 4.18 4.17 4.16 -50 - 25 50 25 TEMPERATURE (C) 0 75 100 4065 G02 VFLOAT (V) 4.21 Charge Current vs Supply Voltage (Constant Current Mode) 200 175 150 RPROG = 10k VBAT = 3.8V TA = 25C IBAT (mA) IBAT (mA) IBAT (mA) 125 100 75 50 25 0 4 4.5 5 5.5 SUPPLY VOLTAGE (V) 6 4065 G04 PROG Pin Voltage vs Temperature (Constant Current Mode) 1.02 VCC = 5V VBAT = 3.8V RPROG = 10k 1.01 VPROG (V) VPROG (V) 1.00 0.6 0.4 RDS (m) 0.99 0.98 -50 -25 50 25 0 TEMPERATURE (C) 4 UW 75 4065 G07 Battery Regulation (Float) Voltage vs Temperature 4.24 4.23 4.22 4.21 4.20 4.19 4.18 4.17 4.16 Regulated Output (Float) Voltage vs Supply Voltage TA = 25C IBAT = 2mA RPROG = 2k 4.21 4 5 4.5 5.5 SUPPLY VOLTAGE (V) 6 4065 G03 Charge Current vs Battery Voltage 600 500 400 300 200 100 0 0 1 2 3 VBAT (V) 4 5 4065 G05 Charge Current vs Temperature with Thermal Regulation (Constant Current Mode) 600 500 400 300 200 100 VCC = 5V VBAT = 3.8V RPROG = 2k 0 100 50 TEMPERATURE (C) 150 4065 G06 VCC = 5V TA = 25C RPROG = 2k THERMAL CONTROL LOOP IN OPERATION 0 -50 PROG Pin Voltage vs Charge Current 1.2 1.0 0.8 450 Power FET On Resistance vs Temperature 550 VCC = 4V IBAT = 400mA VCC = 5V TA = 25C RPROG = 2k 500 400 0.2 0 0 100 200 300 IBAT (mA) 400 500 4065 G08 350 100 300 -50 -25 0 25 50 TEMPERATURE (C) 75 100 4065 G09 4065f LTC4065/LTC4065A TYPICAL PERFOR A CE CHARACTERISTICS Undervoltage Lockout Threshold Voltage vs Temperature 4.0 3.8 RISE 3.5 VMS (V) ICCMS (A) VCC (V) 3.3 3.0 2.8 2.5 -50 FALL -25 50 0 25 TEMPERATURE (C) EN Pin Current (LTC4065) 4.0 3.5 3.0 40 60 VCC = 5V TA = 25C IBAT (mA) 2.0 1.5 1.0 30 20 10 RPROG = 10k IBAT (mA) 2.5 IEN (A) 0.5 0 0 2 2.5 3 3.5 VEN (V) 4 CHRG Pin Output Low Voltage vs Temperature 140 120 100 VCC = 5V ICHRG = 5mA VCHRG (mV) 80 60 40 20 0 -50 VACPR (mV) -25 50 25 0 TEMPERATURE (C) UW 75 4065 G16 Manual Shutdown Threshold Voltage vs Temperature (LTC4065) 1.0 Manual Shutdown Supply Current vs Temperature 40 VCC = 5V VEN = 5V 0.9 RISE 0.8 FALL 0.7 30 20 10 0.6 100 0.5 -50 -25 50 25 0 TEMPERATURE (C) 75 100 4065 G11 0 -50 -25 0 25 50 TEMPERATURE (C) 75 100 4065 G12 Trickle Charge Current vs Supply Voltage VBAT = 2V TA = 25C RPROG = 2k 60 50 40 30 20 10 Trickle Charge Current vs Temperature VCC = 5V VBAT = 2V RPROG = 2k 50 RPROG = 10k 4.5 5 4065 G13 4 4.5 5 5.5 SUPPLY VOLTAGE (V) 6 4065 G14 0 -50 -25 50 25 0 TEMPERATURE (C) 75 100 4065 G15 ACPR Pin Output Low Voltage vs Temperature (LTC4065A Only) 140 120 100 80 60 40 20 0 -50 VCC = 5V IACPR = 5mA 75 100 4065 G10 -25 50 25 0 TEMPERATURE (C) 75 100 4065 G17 4065f 5 LTC4065/LTC4065A TYPICAL PERFOR A CE CHARACTERISTICS Timer Accuracy vs Temperature 1 0 TIMER ACCURACY (%) VCC = 5V 2.0 1.5 -2 -3 -4 -5 -6 -7 -50 -25 50 25 TEMPERATURE (C) 0 75 100 4065 G18 TIMER ACCURACY (%) -1 PROG Pin Shutdown Threshold vs Temperature (LTC4065A Only) 5.0 5.0 VCC = 5V 4.5 4.5 4.0 3.5 3.0 2.5 3.0 -50 2.0 -25 0 25 50 TEMPERATURE (C) 75 100 4065 G20 VRMS(PROG) (V) 4.0 3.5 VMS(PROG) (V) 6 UW Timer Accuracy vs Supply Voltage TA = 25C 1.0 0.5 0 -0.5 -1.0 -1.5 -2.0 4 5 4.5 5.5 SUPPLY VOLTAGE (V) 6 4065 G19 PROG Pin Shutdown Voltage vs Supply Voltage (LTC4065A Only) TA = 25C 4 4.5 5 5.5 SUPPLY VOLTAGE (V) 6 4065 G21 4065f LTC4065/LTC4065A PI FU CTIO S GND (Pin 1): Ground. CHRG (Pin 2): Open-Drain Charge Status Output. The charge status indicator pin has three states: pull-down, pulse at 2Hz and high impedance state. This output can be used as a logic interface or as an LED driver. 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, the CHRG pin is forced to a high impedance state. If the battery voltage remains below 2.9V for one quarter of the charge time, the battery is considered defective and the CHRG pin pulses at a frequency of 2Hz. BAT (Pin 3): Charge Current Output. Provides charge current to the battery and regulates the final float voltage to 4.2V. An internal precision resistor divider on this pin sets the float voltage and is disconnected in shutdown mode. VCC (Pin 4): Positive Input Supply Voltage. This pin provides power to the charger. VCC can range from 3.75V to 5.5V. This pin should be bypassed with at least a 1F capacitor. When VCC is within 32mV of the BAT pin voltage, the LTC4065 enters shutdown mode, dropping IBAT to about 1A. EN (Pin 5, LTC4065 Only): Enable Input Pin. Pulling this pin above the manual shutdown threshold (VMS is typically 0.82V) puts the LTC4065 in shutdown mode. In shutdown mode, the LTC4065 has less than 20A supply current and less than 1A battery drain current. Enable is the default state, but the pin should be tied to GND if unused. ACPR (Pin 5, LTC4065A Only): Open-Drain Power Supply Status Output. When VCC is greater than the undervoltage lockout threshold (3.6V) and VBAT + 80mV (if VBAT > 3.6V), the ACPR pin will be pulled down to ground; otherwise the pin is high impedance. PROG (Pin 6): Charge Current Program and Charge Current Monitor Pin. Connecting a 1% resistor, RPROG, to ground programs the charge current. When charging in constant-current mode, this pin servos to 1V. In all modes, the voltage on this pin can be used to measure the charge current using the following formula: U U U IBAT = VPROG * 1000 RPROG Floating the PROG pin sets the charge current to zero (LTC4065) or puts the part in shutdown mode (LTC4065A). In shutdown mode, the LTC4065A has less than 20A supply current and about 1A battery drain current. Exposed Pad (Pin 7): Ground. The Exposed Pad must be soldered to the PCB ground to provide both electrical contact and rated thermal performance. 4065f 7 LTC4065/LTC4065A SI PLIFIED BLOCK DIAGRA S VCC 4 VCC TDIE + TA D3 115C EN RENB 0.82V - M2 x1 M1 x1000 3.6V 5 + C1 SHUTDOWN D1 D2 BAT 3 - - REF 1.2V R3 MA CA PROG 0.1V + C/10 - R4 1V MP 0.1V R2 CHARGE CONTROL 2 CHRG R5 ENABLE LOBAT BAT SHUTDOWN PROG 6 RPROG 1 GND OSCILLATOR 4056 F01a LOGIC 2.9V Figure 1a. LTC4065 Block Diagram 8 - + W + - + - W + C2 UVLO - + R1 VA + 1.2V COUNTER 4065f LTC4065/LTC4065A SI PLIFIED BLOCK DIAGRA S VCC 4 VCC + C2 5 ACPR D3 - 3.6V + C3 - REF PROG 0.1V R3 VBAT + 80mV 1.2V CA + C/10 - R4 1V MP 0.1V R2 ENABLE 1.2V CHARGE CONTROL 2 CHRG R5 2.9V LOBAT BAT + C1 4V PROG 6 RPROG 1 SHUTDOWN OSCILLATOR GND 4056 F01b - Figure 1b. LTC4065A Block Diagram OPERATIO The LTC4065 is a linear battery charger designed primarily for charging single cell lithium-ion batteries. Featuring an internal P-channel power MOSFET, the charger uses a constant-current/constant-voltage charge algorithm with programmable current. Charge current can be programmed up to 750mA with a final float voltage accuracy of 0.6%. The CHRG open-drain status output indicates if C/10 has been reached. No blocking diode or external sense resistor is required; thus, the basic charger circuit requires only two external components. The ACPR pin (LTC4065A) monitors the status of the input voltage with an open-drain output. An internal termination timer and trickle charge low-battery conditioning adhere to battery manufacturer safety guidelines. Furthermore, the LTC4065 is capable of operating from a USB power source. An internal thermal limit reduces the programmed charge current if the die temperature attempts to rise above a preset value of approximately 115C. This feature protects the LTC4065 from excessive temperature and allows the user to push the limits of the power handling capability of a given circuit board without risk of damaging the LTC4065 or external components. Another benefit of the LTC4065 thermal limit is that charge current can be set according to 4065f - + W D1 + - + - U W + TA TDIE M2 x1 M1 x1000 D2 - 115C BAT 3 - MA + R1 VA + LOGIC COUNTER 9 LTC4065/LTC4065A OPERATIO typical, not worst-case, ambient temperatures for a given application with the assurance that the charger will automatically reduce the current in worst-case conditions. The charge cycle begins when the following conditions are met: the voltage at the VCC pin exceeds 3.6V and approximately 80mV above the BAT pin voltage, a program resistor is present from the PROG pin to ground and the EN pin (LTC4065 only) is pulled below the shutdown threshold (typically 0.82V). If the BAT pin voltage is below 2.9V, the charger goes into trickle charge mode, charging the battery at one-tenth the programmed charge current to bring the cell voltage up to a safe level for charging. If the BAT pin voltage is above 4.1V, the charger will not charge the battery as the cell is near full capacity. Otherwise, the charger goes into the fast charge constant-current mode. When the BAT pin approaches the final float voltage (4.2V), the LTC4065 enters constant-voltage mode and the charge current begins to decrease. When the current drops to 10% of the full-scale charge current, an internal comparator turns off the N-channel MOSFET on the CHRG pin and the pin assumes a high impedance state. An internal timer sets the total charge time, tTIMER (typically 4.5 hours). When this time elapses, the charge cycle terminates and the CHRG pin assumes a high impedance state. To restart the charge cycle, remove the input voltage and reapply it, momentarily force the EN pin above VMS (typically 0.82V) for LTC4065, or momentarily float the PROG pin and reconnect it (LTC4065A). The charge cycle will automatically restart if the BAT pin voltage falls below VRECHRG (typically 4.1V). When the input voltage is not present, the battery drain current is reduced to less than 4A. The LTC4065 can also be shut down by pulling the EN pin above the shutdown threshold voltage. To put LTC4065A in shutdown mode, float the PROG pin. This reduces input quiescent current to less than 20A and battery drain current to less than 1A. Programming Charge Current The charge current is programmed using a single resistor from the PROG pin to ground. The battery charge current is 1000 times the current out of the PROG pin. The 10 U program resistor and the charge current are calculated using the following equations: RPROG = 1000 * 1V ICHG , ICHG = 1000 V RPROG The charge current out of the BAT pin can be determined at any time by monitoring the PROG pin voltage and using the following equation: IBAT = VPROG * 1000 RPROG Undervoltage Lockout (UVLO) An internal undervoltage lockout circuit monitors the input voltage and keeps the charger in undervoltage lockout until VCC rises above 3.6V and approximately 80mV above the BAT pin voltage. The 3.6V UVLO circuit has a built-in hysteresis of approximately 0.6V and the automatic shutdown threshold has a built-in hysteresis of approximately 50mV. During undervoltage lockout conditions, maximum battery drain current is 4A and maximum supply current is 11A. Shutdown Mode The LTC4065 can be disabled by pulling the EN pin above the shutdown threshold (approximately 0.82V). The LTC4065A can be disabled by floating the PROG pin. In shutdown mode, the battery drain current is reduced to less than 1A and the supply current to about 20A. Timer and Recharge The LTC4065 has an internal termination timer that starts when an input voltage greater than the undervoltage lockout threshold is applied to VCC, or when leaving shutdown the battery voltage is less than the recharge threshold. At power-up or when exiting shutdown, if the battery voltage is less than the recharge threshold, the charge time is set to 4.5 hours. If the battery voltage is greater than the recharge threshold at power-up or when exiting shutdown, the timer will not start and charging is prevented since the battery is at or near full capacity. 4065f LTC4065/LTC4065A OPERATIO Once the charge cycle terminates, the LTC4065 continuously monitors the BAT pin voltage using a comparator with a 2ms filter time. When the average battery voltage falls below 4.1V (which corresponds to 80% to 90% battery capacity), a new charge cycle is initiated and a 2.25 hour timer begins. This ensures that the battery is kept at, or near, a fully charged condition and eliminates the need for periodic charge cycle initiations. The CHRG output assumes a strong pull-down state during recharge cycles until C/10 is reached when it transitions to a high impendance state. Trickle Charge and Defective Battery Detection At the beginning of a charge cycle, if the battery voltage is low (below 2.9V), the charger goes into trickle charge, reducing the charge current to 10% of the full-scale current. If the low-battery voltage persists for one quarter of the total time (1.125 hour), the battery is assumed to be defective, the charge cycle is terminated and the CHRG pin output pulses at a frequency of 2Hz with a 80% duty cycle. If for any reason the battery voltage rises above 2.9V, the charge cycle will be restarted. To restart the charge cycle (i.e., when the defective battery is replaced with a discharged battery), simply remove the input voltage and reapply it, temporarily pull the EN pin above the shutdown threshold (LTC4065), or momentarily float the PROG pin and reconnect it (LTC4065A). CHRG Status Output Pin The charge status indicator pin has three states: pulldown, pulse at 2Hz (see Trickle Charge and Defective Battery Detection) and high impedance. The pull-down state indicates that the LTC4065 is in a charge cycle. A high impedance state indicates that the charge current has dropped below 10% of the full-scale current or the LTC4065 is disabled. Figure 2 shows the CHRG status under various conditions. Power Supply Status Indicator (ACPR, LTC4065A Only) The power supply status output has two states: pull-down and high impedance. The pull-down state indicates that VCC is above the undervoltage lockout threshold (see Undervoltage Lockout). When this condition is not met, U the ACPR pin is high impedance indicating that the LTC4065A is unable to charge the battery. Charge Current Soft-Start and Soft-Stop The LTC4065 includes a soft-start circuit to minimize the inrush current at the start of a charge cycle. When a charge cycle is initiated, the charge current ramps from zero to the full-scale current over a period of approximately 180s. Likewise, internal circuitry slowly ramps the charge current from full-scale to zero when the charger is shut off or self terminates. This has the effect of minimizing the transient current load on the power supply during start-up and charge termination. Constant-Current/Constant-Voltage/ Constant-Temperature The LTC4065/LTC4065A use a unique architecture to charge a battery in a constant-current, constant-voltage and constant-temperature fashion. Figures 1a and 1b show simplified block diagrams of the LTC4065 and LTC4065A, respectively. Three of the amplifier feedback loops shown control the constant-current, CA, constantvoltage, VA, and constant-temperature, TA modes. A fourth amplifier feedback loop, MA, is used to increase the output impedance of the current source pair; M1 and M2 (note that M1 is the internal P-channel power MOSFET). It ensures that the drain current of M1 is exactly 1000 times greater than the drain current of M2. Amplifiers CA and VA are used in separate feedback loops to force the charger into constant-current or constantvoltage mode, respectively. Diodes D1 and D2 provide priority to either the constant-current or constant-voltage loop; whichever is trying to reduce the charge current the most. The output of the other amplifier saturates low which effectively removes its loop from the system. When in constant-current mode, CA servos the voltage at the PROG pin to be precisely 1V. VA servos its inverting input to an internal reference voltage when in constant-voltage mode and the internal resistor divider, made up of R1 and R2, ensures that the battery voltage is maintained at 4.2V. The PROG pin voltage gives an indication of the charge current during constant-voltage mode as discussed in "Programming Charge Current". 4065f 11 LTC4065/LTC4065A OPERATIO POWER ON Transconductance amplifier, TA, limits the die temperature to approximately 115C when in constant-temperature mode. Diode D3 ensures that TA does not affect the charge current when the die temperature is below approximately 115C. The PROG pin voltage continues to give an indication of the charge current. In typical operation, the charge cycle begins in constantcurrent mode with the current delivered to the battery equal to 1000V/RPROG. If the power dissipation of the 12 U ENABLE NO IS EN > SHUTDOWN THRESHOLD? YES SHUTDOWN MODE CHRG HIGH IMPEDANCE IF VCC > 3.6V AND VCC > VBAT + 80mV? YES UVLO NO CHRG HIGH IMPEDANCE UVLO MODE VBAT 2.9V TRICKLE CHARGE MODE 1/10 FULL CHARGE CURRENT CHRG STRONG PULL-DOWN 1/4 CHARGE CYCLE (1.125 HOURS) DEFECTIVE BATTERY IS VBAT < 2.9V? NO 2.9V < VBAT < 4.1V FAST CHARGE MODE FULL CHARGE CURRENT CHRG STRONG PULL-DOWN CHARGE CYCLE (4.5 HOURS) RECHARGE IS VBAT < 4.1V? NO VBAT > 4.1V STANDBY MODE NO CHARGE CURRENT CHRG HIGH IMPEDANCE YES BAD BATTERY MODE NO CHARGE CURRENT CHRG PULSES (2Hz) VCC < 3V OR EN > SHDN THRESHOLD YES RECHARGE MODE FULL CHARGE CURRENT CHRG STRONG PULL-DOWN 1/2 CHARGE CYCLE (2.25 HOURS) 4065 F02 Figure 2. State Diagram of LTC4065 Operation LTC4065/LTC4065A results in the junction temperature approaching 115C, the amplifier (TA) will begin decreasing the charge current to limit the die temperature to approximately 115C. As the battery voltage rises, the LTC4065/LTC4065A either return to constant-current mode or enter constant-voltage mode straight from constanttemperature mode. Regardless of mode, the voltage at the PROG pin is proportional to the current delivered to the battery. 4065f LTC4065/LTC4065A APPLICATIO S I FOR ATIO Undervoltage Charge Current Limiting (UVCL) The LTC4065/LTC4065A includes undervoltage charge (VUVCL1) current limiting that prevents full charge current until the input supply voltage reaches approximately 200mV above the battery voltage. This feature is particularly useful if the LTC4065 is powered from a supply with long leads (or any relatively high output impedance). For example, USB-powered systems tend to have highly variable source impedances (due primarily to cable quality and length). A transient load combined with such impedance can easily trip the UVLO threshold and turn the charger off unless undervoltage charge current limiting is implemented. Consider a situation where the LTC4065 is operating under normal conditions and the input supply voltage begins to droop (e.g., an external load drags the input supply down). If the input voltage reaches VBAT + VUVCL1 (approximately 220mV above the battery voltage), undervoltage charge current limiting will begin to reduce the charge current in an attempt to maintain VUVCL1 between the VCC input and the BAT output of the IC. The LTC4065 will continue to operate at the reduced charge current until the input supply voltage is increased or voltage mode reduces the charge current further. Operation from Current Limited Wall Adapter By using a current limited wall adapter as the input supply, the LTC4065 dissipates significantly less power when programmed for a current higher than the limit of the supply as compared to using a non-current limited supply at the same charge current. Consider a situation where an application demands a 600mA charge current for an 800mAh Li-Ion battery. If a typical 5V (non-current limited) input supply is available then the peak power dissipation inside the part can exceed 1W. Now consider the same scenario, but with a 5V input supply with a 600mA current limit. To take advantage of the supply, it is necessary to program the LTC4065 to charge at a current above 600mA. Assume that the LTC4065 is programmed for 650mA (i.e., RPROG = 1.54k) to ensure that part tolerances maintain a programmed current higher U than 600mA. Since the LTC4065 will demand a charge current higher than the current limit of the voltage supply, the supply voltage will drop to the battery voltage plus 600mA times the "on" resistance of the internal PFET. The "on" resistance of the LTC4065 power device is approximately 450m with a 5V supply. The actual "on" resistance will be slightly higher due to the fact that the input supply will drop to less than 5V. The power dissipated during this phase of charging is less than 240mW. That is a 76% improvement over the non-current limited supply power dissipation. USB and Wall Adapter Power Although the LTC4065/LTC4065A allow charging from a USB port, a wall adapter can also be used to charge Li-Ion batteries. Figure 3 shows an example of how to combine wall adapter and USB power inputs. A P-channel MOSFET, MP1, is used to prevent back conducting into the USB port when a wall adapter is present and Schottky diode, D1, is used to prevent USB power loss through the 1k pull-down resistor. Typically a wall adapter can supply significantly more current than the 500mA-limited USB port. Therefore, an N-channel MOSFET, MN1, and an extra program resistor are used to increase the charge current to 750mA when the wall adapter is present. 5V WALL ADAPTER 750mA ICHG USB POWER 500mA ICHG 4 MP1 3 ICHG SYSTEM LOAD BAT LTC4065 VCC PROG MN1 4.02k 1k 4065 F03 W UU 6 + Li-Ion BATTERY 2k Figure 3. Combining Wall Adapter and USB Power Stability Considerations The LTC4065/LTC4065A contain two control loops: constant-voltage and constant-current. The constant-voltage loop is stable without any compensation when a battery is connected with low impedance leads. Excessive lead 4065f 13 LTC4065/LTC4065A APPLICATIO S I FOR ATIO length, however, may add enough series inductance to require a bypass capacitor of at least 1F from BAT to GND. Furthermore, a 4.7F capacitor with a 0.2 to 1 series resistor from BAT to GND is required to keep ripple voltage low when the battery is disconnected. High value capacitors with very low ESR (especially ceramic) may reduce the constant-voltage loop phase margin. Ceramic capacitors up to 22F may be used in parallel with a battery, but larger ceramics should be decoupled with 0.2 to 1 of series resistance. In constant-current mode, the PROG pin is in the feedback loop, not the battery. Because of the additional pole created by the PROG pin capacitance, capacitance on this pin must be kept to a minimum. With no additional capacitance on the PROG pin, the charger is stable with program resistor values as high as 25k. However, additional capacitance on this node reduces the maximum allowed program resistor. The pole frequency at the PROG pin should be kept above 100kHz. Therefore, if the PROG pin is loaded with a capacitance, CPROG, the following equation should be used to calculate the maximum resistance value for RPROG: RPROG 2 * 105 1 * CPROG Average, rather than instantaneous, battery current may be of interest to the user. For example, if a switching power supply operating in low current mode is connected in parallel with the battery, the average current being pulled out of the BAT pin is typically of more interest than the instantaneous current pulses. In such a case, a simple RC filter can be used on the PROG pin to measure the average battery current as shown in Figure 4. A 10K resistor has been added between the PROG pin and the filter capacitor to ensure stability. LTC4065 PROG GND 10k RPROG 4065 F04 CFILTER CHARGE CURRENT MONITOR CIRCUITRY Figure 4. Isolating Capacitive Load on the PROG Pin and Filtering 4065f 14 U Power Dissipation The conditions that cause the LTC4065/LTC4065A to reduce charge current through thermal feedback can be approximated by considering the power dissipated in the IC. For high charge currents, the LTC4065/LTC4065A power dissipation is approximately: PD = (VCC - VBAT) * IBAT Where PD is the power dissipated, VCC is the input supply voltage, VBAT is the battery voltage and IBAT is the charge current. It is not necessary to perform any worst-case power dissipation scenarios because the LTC4065 will automatically reduce the charge current to maintain the die temperature at approximately 115C. However, the approximate ambient temperature at which the thermal feedback begins to protect the IC is: TA = 115C - PD * JA TA = 115C - (VCC - VBAT) * IBAT * JA Example: Consider an LTC4065/LTC4065A operating from a 5V wall adapter providing 750mA to a 3.6V Li-Ion battery. The ambient temperature above which the LTC4065/LTC4065A will begin to reduce the 750mA charge current is approximately: TA = 115C - (5V - 3.6V) * (750mA) * 60C/W TA = 115C - 1.05W * 60C/W = 115C - 63C TA = 52C The LTC4065/LTC4065A can be used above 70C, but the charge current will be reduced from 750mA. The approximate current at a given ambient temperature can be calculated: IBAT = 115C - TA ( VCC - VBAT ) * JA W UU Using the previous example with an ambient temperature of 73C, the charge current will be reduced to approximately: IBAT = 115C - 73C 42C = = 500mA (5V - 3.6V ) * 60C/W 84C/A LTC4065/LTC4065A APPLICATIO S I FOR ATIO Furthermore, the voltage at the PROG pin will change proportionally with the charge current as discussed in the Programming Charge Current section. It is important to remember that LTC4065/LTC4065A applications do not need to be designed for worst-case thermal conditions since the IC will automatically reduce power dissipation when the junction temperature reaches approximately 115C. Board Layout Considerations In order to deliver maximum charge current under all conditions, it is critical that the exposed metal pad on the backside of the LTC4065/LTC4065A package is soldered to the PC board ground. Correctly soldered to a 2500mm2 double-sided 1 oz. copper board the LTC4065/LTC4065A has a thermal resistance of approximately 60C/W. Failure to make thermal contact between the Exposed Pad on the PACKAGE DESCRIPTIO DC Package 6-Lead Plastic DFN (2mm x 2mm) (Reference LTC DWG # 05-08-1703) R = 0.115 TYP 0.56 0.05 (2 SIDES) 2.00 0.10 (4 SIDES) PIN 1 CHAMFER OF EXPOSED PAD 3 0.25 0.05 0.50 BSC 1.42 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WCCD-2) 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 0.200 REF 0.75 0.05 1 (DC6) DFN 1103 0.675 0.05 2.50 0.05 1.15 0.05 0.61 0.05 (2 SIDES) PACKAGE OUTLINE 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. U backside of the package and the copper board will result in thermal resistances far greater than 60C/W. As an example, a correctly soldered LTC4065/LTC4065A can deliver over 750mA to a battery from a 5V supply at room temperature. Without a backside thermal connection, this number could drop to less than 500mA. VCC Bypass Capacitor 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 live power source. For more information, refer to Application Note 88. 0.38 0.05 4 6 PIN 1 BAR TOP MARK (SEE NOTE 6) 0.25 0.05 0.50 BSC 1.37 0.05 (2 SIDES) 0.00 - 0.05 BOTTOM VIEW--EXPOSED PAD 4065f U W UU 15 LTC4065/LTC4065A RELATED PARTS PART NUMBER Battery Chargers LTC1734 LTC1734L LTC4002 LTC4050 LTC4052 LTC4053 LTC4054 LTC4057 LTC4058 LTC4059 LTC4059A LTC4061 LTC4061-4.4 LTC4062 LTC4063 LTC4411/LTC4412 Power Management LTC3405/LTC3405A LTC3406/LTC3406A LTC3411 LTC3440 LTC4413 300mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converter 600mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converter 1.25A (IOUT), 4MHz, Synchronous Step-Down DC/DC Converter 600mA (IOUT), 2MHz, Synchronous Buck-Boost DC/DC Converter Dual Ideal Diode in DFN 95% Efficiency, VIN: 2.7V to 6V, VOUT = 0.8V, IQ = 20A, ISD < 1A, ThinSOT Package 95% Efficiency, VIN: 2.5V to 5.5V, VOUT = 0.6V, IQ = 20A, ISD < 1A, ThinSOT Package 95% Efficiency, VIN: 2.5V to 5.5V, VOUT = 0.8V, IQ = 60A, ISD < 1A, MS Package 95% Efficiency, VIN: 2.5V to 5.5V, VOUT = 2.5V, IQ = 25A, ISD < 1A, MS Package 2-Channel Ideal Diode ORing, Low Forward ON Resistance, Low Regulated Forward Voltage, 2.5V VIN 5.5V Lithium-Ion Linear Battery Charger in ThinSOTTM Lithium-Ion Linear Battery Charger in ThinSOT Switch Mode Lithium-Ion Battery Charger Lithium-Ion Linear Battery Charger Controller Monolithic Lithium-Ion Battery Pulse Charger USB Compatible Monolithic Li-Ion Battery Charger Standalone Linear Li-Ion Battery Charger with Integrated Pass Transistor in ThinSOT Lithium-Ion Linear Battery Charger Standalone 950mA Lithium-Ion Charger in DFN 900mA Linear Lithium-Ion Battery Charger 900mA Linear Lithium-Ion Battery Charger Standalone Li-Ion Charger with Thermistor Interface Standalone Li-Ion Charger with Thermistor Interface Standalone Linear Li-Ion Battery Charger with Micropower Comparator Li-Ion Charger with Linear Regulator Low Loss PowerPathTM Controller in ThinSOT Simple ThinSOT Charger, No Blocking Diode, No Sense Resistor Needed Low Current Version of LTC1734, 50mA ICHRG 180mA Standalone, 4.7V VIN 24V, 500kHz Frequency, 3 Hour Charge Termination Features Preset Voltages, C/10 Charger Detection and Programmable Timer, Input Power Good Indication, Thermistor Interface No Blocking Diode or External Power FET Required, 1.5A Charge Current Standalone Charger with Programmable Timer, Up to 1.25A Charge Current Thermal Regulation Prevents Overheating, C/10 Termination, C/10 Indicator, Up to 800mA Charge Current Up to 800mA Charge Current, Thermal Regulation, ThinSOT Package C/10 Charge Termination, Battery Kelvin Sensing, 7% Charge Accuracy 2mm x 2mm DFN Package, Thermal Regulation, Charge Current Monitor Output 2mm x 2mm DFN Package, Thermal Regulation, Charge Current Monitor Output, ACPR Function 4.2V, 0.35% Float Voltage, Up to 1A Charge Current, 3mm x 3mm DFN 4.4V (Max), 0.4% Float Voltage, Up to 1A Charge Current, 3mm x 3mm DFN 4.2V, 0.35% Float Voltage, Up to 1A Charge Current, 3mm x 3mm DFN Up to 1A Charge Current, 100mA, 125mV LDO, 3mm x 3mm DFN Automatic Switching Between DC Sources, Load Sharing, Replaces ORing Diodes DESCRIPTION COMMENTS ThinSOT and PowerPath are trademarks of Linear Technology Corporation. 4065f 16 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 LT/TP 0705 500 * PRINTED IN THE USA www.linear.com (c) LINEAR TECHNOLOGY CORPORATION 2005 |
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