LTC4069-4.4 Standalone 750mA Li-Ion Battery Charger in 2 × 2 DFN with NTC Thermistor Input DESCRIPTION FEATURES n n n n n n n n n n n n n Complete Linear Charger in 2mm × 2mm DFN Package C/10 Charge Current Detection Output Timer Charge Termination Charge Current Programmable Up to 750mA with 5% Accuracy No External MOSFET, Sense Resistor or Blocking Diode Required NTC Thermistor Input for Temperature Qualified Charging Preset 4.4V Float Voltage with 0.6% Accuracy Constant-Current/Constant-Voltage Operation with Thermal Feedback to Maximize Charge Rate Without Risk of Overheating Charge Current Monitor Output for Gas Gauging Automatic Recharge Charges Single-Cell Li-Ion Batteries Directly from USB Port 20μA Supply Current in Shutdown Mode Soft-Start Limits Inrush Current Tiny 6-Lead (2mm × 2mm) DFN Package APPLICATIONS n n n The LTC®4069-4.4 is a complete constant-current/ constant-voltage linear charger for high capacity single-cell lithium-ion batteries with a 4.4V float voltage. The 2mm × 2mm DFN package and low external component count make the LTC4069-4.4 especially well-suited for portable applications. Furthermore, LTC4069-4.4 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 LTC4069-4.4 automatically enters a low current state, dropping battery drain current to less than 1μA. With power applied, LTC4069-4.4 can be put into shutdown mode, reducing the supply current to less than 20μA. The LTC4069-4.4 also includes automatic recharge, lowbattery charge conditioning (trickle charging), soft-start (to limit inrush current) and an NTC thermistor input used to monitor battery temperature. Wireless PDAs Cellular Phones Portable Electronics , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 6522118, 6700364. TYPICAL APPLICATION The LTC4069-4.4 is available in a tiny 6-lead, low profile (0.75mm) 2mm × 2mm DFN package. Complete Charge Cycle (1100mAh Battery) 550 Standalone Li-Ion Battery Charger 4.5 CONSTANT-CURRENT 500 450 VCC RNOM 100k R1 510Ω LTC4069-4.4 CHRG PROG NTC RNTC 100k BAT + GND 1μF 4.4V Li-Ion BATTERY* RPROG 2k 4069 TA01 4.3 CHRG TRANSITION 400 4.2 350 CONSTANT300 VOLTAGE 4.1 250 3.9 200 3.8 150 3.7 CHARGE 3.6 TERMINATION 3.5 4.0 100 VCC = 5V RPROG = 2K 50 *E.G. SANYO BATTERIES: UF553436T OR UF553450T 4.4 0 0 0.5 1 1.5 2 2.5 3 3.5 TIME (HOURS) BATTERY VOLTAGE (V) 500mA VIN 4.5V TO 5.5V CHARGE CURRENT (mA) n 3.4 4 4.5 5 4069 TA01b 406944fa 1 LTC4069-4.4 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) TOP VIEW VCC t < 1ms and Duty Cycle < 1% ................. – 0.3V to 7V Steady State............................................ – 0.3V to 6V BAT, CHRG .................................................. –0.3V to 6V PROG, NTC ..................................... – 0.3V to VCC + 0.3V BAT Short-Circuit Duration............................Continuous BAT Pin Current .................................................. 800mA PROG Pin Current ................................................ 800μA Junction Temperature (Note 6) ............................ 125°C Operating Temperature Range (Note 2)....– 40°C to 85°C Storage Temperature Range.................. –65°C to 125°C GND 1 CHRG 2 6 PROG 7 BAT 3 5 NTC 4 VCC DC PACKAGE 6-LEAD (2mm s 2mm) PLASTIC DFN TJMAX = 125°C, θJA = 60°C/W (NOTE 3) EXPOSED PAD (PIN 7) IS GND MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LTC4069EDC-4.4#PBF LTC4069EDC-4.4#TRPBF LCKQ 6-Lead (2mm X 2mm) Plastic DFN –40°C to 85°C Consult LTC Marketing for parts specified with wider operating temperature ranges. Consult LTC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. VCC = 5V, VBAT = 3.8V, VNTC = 0V unless otherwise specified. (Note 2) SYMBOL PARAMETER CONDITIONS VCC VCC Supply Voltage (Note 4) l MIN ICC Quiescent VCC Supply Current VBAT = 4.5V (Forces IBAT and IPROG = 0) l TYP 3.75 MAX UNITS 5.5 V 120 250 μA 20 40 μA 6 11 μA 4.375 4.358 4.4 4.4 4.425 4.442 V V 100 500 112 525 mA mA ICCMS VCC Supply Current in Shutdown Float PROG l ICCUV VCC Supply Current in Undervoltage Lockout VCC < VBAT, VCC = 3.5V, VBAT = 4V l VFLOAT VBAT Regulated Output Voltage IBAT = 2mA IBAT = 2mA, 0°C < TA < 85°C IBAT BAT Pin Current RPROG = 10k (0.1%), Current Mode RPROG = 2k (0.1%), Current Mode l l 88 475 IBMS Battery Drain Current in Shutdown Mode Floating PROG, VCC > VBAT l –1 0 1 μA IBUV Battery Drain Current in Undervoltage Lockout VCC = 3.5V, VBAT = 4V l 0 1 4 μA VUVLO VCC Undervoltage Lockout Voltage VCC Rising VCC Falling l l 3.4 2.8 3.6 3 3.8 3.2 V V VPROG PROG Pin Voltage RPROG = 2k, IPROG = 500μA RPROG = 10k, IPROG = 100μA l l 0.98 0.98 1 1 1.02 1.02 V V VASD Automatic Shutdown Threshold Voltage (VCC – VBAT), VCC Low to High (VCC – VBAT), VCC High to Low 60 15 80 30 100 45 mV mV 406944fa 2 LTC4069-4.4 ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. VCC = 5V, VBAT = 3.8V, VNTC = 0V unless otherwise specified. (Note 2) SYMBOL PARAMETER CONDITIONS IPROG PROG Pin Pull-Up Current VPROG > 1V MIN TYP MAX 3 l VMS, PROG PROG Shutdown Threshold Voltage tSS Soft-Start Time VPROG Rising ITRKL Trickle Charge Current VBAT = 2V, RPROG = 2k (0.1%) VTRKL Trickle Charge Threshold Voltage VBAT Rising VTRHYS Trickle Charge Hysteresis Voltage 3.7 4 μA 4.3 170 l UNITS V μs 35 50 65 2.7 2.9 3.05 90 mA V mV ΔVRECHRG Recharge Battery Threshold Voltage VFLOAT – VRECHRG , 0°C < TA < 85°C 70 100 130 mV ΔVUVCL1 ΔVUVCL2 (VCC – VBAT) Undervoltage Current Limit IBAT = 90% Programmed Charge Current IBAT = 10% Programmed Charge Current 180 90 220 125 330 150 mV mV tTIMER Termination Timer l 3 4.5 6 Hrs Recharge Timer l 1.5 2.25 3 Hrs 0.75 Low-Battery Trickle Charge Time VBAT = 2.5V l 1.125 1.5 Hrs VCHRG CHRG Pin Output Low Voltage ICHRG = 5mA l 60 105 mV ICHRG CHRG Pin Leakage Current VBAT = 4.5V, VCHRG = 5V l 0 1 μA RPROG = 2k (Note 5) l 0.095 0.11 IC/10 End of Charge Indication Current Level TLIM Junction Temperature in Constant Temperature Mode RON Power FET On-Resistance (Between VCC and BAT) fBADBAT 0.08 mA/mA 115 °C 450 mΩ Defective Battery Detection CHRG Pulse Frequency 2 Hz DBADBAT Defective Battery Detection CHRG Pulse Frequency Duty Ratio 75 % IBAT = 350mA INTC NTC Pin Current VNTC = 2.5V VCOLD Cold Temperature Fault Threshold Voltage Rising Voltage Threshold Hysteresis 0.76 • VCC 0.015 • VCC V V VHOT Hot Temperature Fault Threshold Voltage Falling Voltage Threshold Hysteresis 0.35 • VCC 0.017 • VCC V V VNTC-DIS NTC Disable Threshold Voltage Falling Threshold; VCC = 5V 1 μA 82 mV VDIS-HYS NTC Disable Hysteresis Voltage 50 mV fNTC Fault Temperature CHRG Pulse Frequency 2 Hz DNTC Fault Temperature CHRG Pulse Frequency Duty Ratio 25 % Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LTC4069-4.4 is guaranteed to meet performance specifications from 0°C to 85°C. Specifications over the –40°C to 85°C 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 rated. Note 4: Although the LTC4069-4.4 functions properly at 3.75V, full charge current requires an input voltage greater than the desired final battery voltage per the ΔVUVCL1 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 125°C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. 406944fa 3 LTC4069-4.4 TYPICAL PERFORMANCE CHARACTERISTICS VCC = 5V TA = 25°C RPROG = 2k VFLOAT (V) VFLOAT (V) 4.42 4.40 4.44 4.42 4.42 4.40 4.38 4.38 4.36 4.44 VFLOAT (V) 4.44 Battery Regulation (Float) Voltage vs Supply Voltage Battery Regulation (Float) Voltage vs Temperature Battery Regulation (Float) Voltage vs Charge Current 100 0 200 300 IBAT (mA) 400 500 4.36 –50 –25 0 50 25 TEMPERATURE (°C) 75 4.36 100 5 4.5 5.5 SUPPLY VOLTAGE (V) 4 6 4069 G02 Charge Current vs Supply Voltage (Constant-Current Mode) 4069 G03 Charge Current vs Ambient Temperature with Thermal Regulation (Constant-Current Mode) Charge Current vs Battery Voltage 600 RPROG = 10k VBAT = 3.8V TA = 25°C 175 4.40 4.38 4069 G01 200 VCC = 5V IBAT = 2mA RPROG = 2k 600 VCC = 5V TA = 25°C RPROG = 2k 500 500 400 100 75 IBAT (mA) 400 125 IBAT (mA) IBAT (mA) 150 300 THERMAL CONTROL LOOP IN OPERATION 300 200 200 100 100 50 25 4 4.5 5 5.5 SUPPLY VOLTAGE (V) 0 6 1 2 3 VBAT (V) 4 5 0 100 50 TEMPERATURE (°C) 150 4069 G06 4069 G05 4069 G04 PROG Pin Voltage vs Charge Current PROG Pin Voltage vs Temperature (Constant-Current Mode) 1.02 0 –50 0 0 VCC = 5V VBAT = 3.8V RPROG = 2k 1.2 VCC = 5V VBAT = 3.8V RPROG = 10k Power FET On-Resistance vs Temperature 550 VCC = 5V TA = 25°C RPROG = 2k 1.0 VCC = 4V IBAT = 400mA 500 1.01 1.00 RDS (mΩ) VPROG (V) VPROG (V) 0.8 0.6 450 400 0.4 0.99 350 0.2 0.98 –50 –25 50 25 0 TEMPERATURE (°C) 75 100 4069 G07 0 0 100 200 300 IBAT (mA) 400 500 4069 G08 300 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 4069 G09 406944fa 4 LTC4069-4.4 TYPICAL PERFORMANCE CHARACTERISTICS Undervoltage Lockout Threshold Voltage vs Temperature Trickle Charge Current vs Supply Voltage 4.00 60 3.75 60 VBAT = 2V TA = 25°C 50 40 3.25 FALL 3.00 30 20 2.75 RPROG = 10k 50 0 25 TEMPERATURE (°C) 75 4 100 4.5 5 5.5 SUPPLY VOLTAGE (V) 60 40 20 1.5 –1 1.0 –2 –3 –4 –5 –25 50 25 0 TEMPERATURE (oC) 75 100 –7 –50 –25 0 50 25 TEMPERATURE (°C) 75 4069 G10 0.5 0 –0.5 –1.0 –2.0 100 4 5 4.5 5.5 SUPPLY VOLTAGE (V) 4069 G18 PROG Pin Shutdown Voltage Threshold vs Temperature 5.0 TA = 25°C –1.5 6 4069 G19 PROG Pin Shutdown Voltage vs Supply Voltage 5.0 VCC = 5V TA = 25°C 4.5 4.5 VMS(PROG) (V) 0 –50 VCC = 5V 0 –6 VMS(PROG) (V) VCHRG (mV) 80 100 Timer Accuracy vs Supply Voltage 2.0 TIMER ACCURACY (%) TIMER ACCURACY (%) VCC = 5V ICHRG = 5mA 75 4069 G15 Timer Accuracy vs Temperature 1 100 50 25 0 TEMPERATURE (°C) –25 4069 G14 CHRG Pin Output Low Voltage vs Temperature 120 0 –50 6 4069 G16 140 RPROG = 10k 10 0 –25 30 20 10 2.50 –50 RPROG = 2k 40 IBAT (mA) IBAT (mA) 3.50 VCC = 5V VBAT = 2V 50 RPROG = 2k RISE VCC (V) Trickle Charge Current vs Temperature 4.0 4.0 3.5 3.0 3.5 2.5 3.0 –50 2.0 –25 0 25 50 TEMPERATURE (°C) 75 100 4069 G20 4 4.5 5 5.5 SUPPLY VOLTAGE (V) 6 4069 G21 406944fa 5 LTC4069-4.4 PIN FUNCTIONS 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. The pin becomes high impedance when any of the following conditions occur: the charge current drops below 10% of full-scale current, the timer ends, or the charger is shut down. 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 (75% duty cycle). When the NTC pin voltage rises above 0.76 • VCC or drops below 0.35 • VCC , the CHRG pin pulses at a frequency of 2Hz (25% duty cycle). BAT (Pin 3): Charge Current Output. Provides charge current to the battery and regulates the final float voltage to 4.4V. 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 1μF capacitor. When VCC is within 30mV of the BAT pin voltage, the LTC4069-4.4 enters shutdown mode, dropping IBAT to about 1μA. NTC (Pin 5): Input to the NTC (Negative Temperature Coefficient) Thermistor Temperature Monitoring Circuit. Under normal operation, connect a thermistor from the NTC pin to ground and a resistor of equal value from the NTC pin to VCC . When the voltage at this pin drops below 0.35 • VCC at hot temperatures or rises above 0.76 • VCC at cold, charging is suspended, the internal timer is frozen and the CHRG pin output will start to pulse at 2Hz. Pulling this pin below 0.016 • VCC disables the NTC feature. There is approximately 3°C of temperature hysteresis associated with each of the input comparator’s thresholds. 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: IBAT = VPROG • 1000 RPROG Floating the PROG pin puts the charger in shutdown mode. In shutdown mode, the LTC4069-4.4 has less than 20μA supply current and about 1μA 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. 406944fa 6 LTC4069-4.4 SIMPLIFIED BLOCK DIAGRAM VCC 4 VCC VCC TDIE + 115°C – TA R7 – + VCC + M2 1s TOO COLD C1 OR SUSPEND AND R8 RNOM D3 UVLO C5 M1 1000s – 3.6V D2 D1 + NTC BAT C2 5 TOO HOT – RNTC – 3 + + MA CA + NTC_EN C3 1.2V MP – 1.2V REF R10 PROG 0.1V + – R2 R3 1V CHARGE CONTROL R4 0.1V C/10 ENABLE R5 2 VA R1 + + – – R9 CHRG 2.9V BAT SUSPEND – + + 4V COUNTER SHUTDOWN C4 LOBAT LOGIC – PROG 6 GND 1 OSCILLATOR 4069 F01 RPROG Figure 1. LTC4069-4.4 Block Diagram OPERATION The LTC4069-4.4 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. An internal termination timer and trickle charge lowbattery conditioning adhere to battery manufacturer safety guidelines. Furthermore, the LTC4069-4.4 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 115°C. This feature protects the LTC4069-4.4 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 LTC4069-4.4 or external components. Another benefit of the LTC4069-4.4 thermal limit is that charge current can be set according to typical, not worst-case, ambient 406944fa 7 LTC4069-4.4 OPERATION 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 voltage at the VCC pin rises above 3.5V and approximately 80mV above the BAT pin voltage, a 1% program resistor is connected from the PROG pin to ground and the NTC pin voltage stays between 0.76 • VCC and 0.35 • VCC or below 0.016 • VCC. 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 4.3V, 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 (4.4V), the LTC4069-4.4 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. The charge cycle will automatically restart if the BAT pin voltage falls below VRECHRG (typically 4.3V). To manually restart the charge cycle, remove the input voltage and reapply it, or momentarily float the PROG pin and reconnect it. 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 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 4μA and maximum supply current is 11μA. Shutdown Mode The LTC4069-4.4 can be disabled by floating the PROG pin. In shutdown mode, the battery drain current is reduced to less than 1μA and the supply current to about 20μA. Timer and Recharge The LTC4069-4.4 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 and 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 temperature is either too high or too low, the timer will pause until the battery returns to normal temperature. If the battery 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. Once the charge cycle terminates, the LTC4069-4.4 continuously monitors the BAT pin voltage using a comparator with a 2ms filter time. When the battery voltage falls below 4.3V (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. Also, if the 406944fa 8 LTC4069-4.4 OPERATION battery voltage does not exceed the recharge threshold voltage when the timer ends, the timer resets and a 2.25 hour recharge cycle begins. 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 75% 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 less than 2.9V), simply remove the input voltage and reapply it or momentarily float the PROG pin and reconnect it. CHRG Status Output Pin The charge status indicator pin has three states: pulldown, pulse at 2Hz (see Trickle Charge and Defective Battery Detection and Battery Temperature Monitoring) and high impedance. The pull-down state indicates that the LTC4069-4.4 is in a charge cycle. A high impedance state indicates that the charge current has dropped below 10% of the full-scale current, the timer has ended the charge cycle, or the LTC4069-4.4 is disabled. Figure 2 shows the CHRG status under various conditions. Charge Current Soft-Start and Soft-Stop The LTC4069-4.4 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 170μs. 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 LTC4069-4.4 uses a unique architecture to charge a battery in a constant-current, constant-voltage and constant-temperature fashion. Figure 1 shows a Simplified Block Diagram of the LTC4069-4.4. Three of the amplifier feedback loops shown control the constant-current (CA), constant-voltage (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 4.4V. The PROG pin voltage gives an indication of the charge current during constant-voltage mode as discussed in “Programming Charge Current”. Transconductance amplifier, TA, limits the die temperature to approximately 115°C when in constant-temperature mode. Diode D3 ensures that TA does not affect the charge current when the die temperature is below approximately 115°C. 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 LTC4069-4.4 results in the junction temperature approaching 115°C, the amplifier (TA) will begin decreasing the charge current to limit the die temperature to approximately 115°C. As the battery voltage rises, the LTC4069-4.4 either returns to constant-current mode or enters constant-voltage mode 406944fa 9 LTC4069-4.4 OPERATION UVLO UVLO MODE NO POWER ON IF VCC > 3.6V AND VCC > VBAT + 80mV? VBAT > 4.3V YES STANDBY MODE NTC FAULT TEMPERATURE NOT OK TEMPERATURE OK VBAT ≤ 2.9V 2.9V < VBAT < 4.3V TRICKLE CHARGE MODE FAST CHARGE MODE 1/10 FULL CHARGE CURRENT CHRG STRONG PULL-DOWN FULL CHARGE CURRENT CHRG STRONG PULL-DOWN 1/4 CHARGE CYCLE (1.125 HOURS) NO CHARGE CURRENT CHRG HIGH IMPEDANCE BATTERY CHARGING SUSPENDED CHRG PULSES (2Hz) TEMPERATURE NOT OK CHRG HIGH IMPEDANCE NO CHARGE CYCLE (4.5 HOURS) DEFECTIVE BATTERY NO RECHARGE IS VBAT < 4.3V? IS VBAT < 2.9V? YES YES BAD BATTERY MODE NO CHARGE CURRENT CHRG PULSES (2Hz) VCC < 3V RECHARGE MODE FULL CHARGE CURRENT CHRG STRONG PULL-DOWN 1/2 CHARGE CYCLE (2.25 HOURS) 4069 F02 Figure 2. State Diagram of LTC4069-4.4 Operation straight from constant-temperature mode. Regardless of mode, the voltage at the PROG pin is proportional to the current delivered to the battery. Battery Temperature Monitoring via NTC The battery temperature is measured by placing a negative temperature coefficient (NTC) thermistor close to the battery pack. The NTC circuitry is shown in Figure 3. To use this feature, connect the NTC thermistor, RNTC , between the NTC pin and ground and a resistor, RNOM , from the NTC pin to VCC . RNOM should be a 1% resistor with a value equal to the value of the chosen NTC thermistor at 25°C (this value is 100k for a Vishay NTHS0603N01N1003J thermistor). The LTC4069-4.4 goes into hold mode when the value of the NTC thermistor drops to 0.53 times the value of RNOM , which corresponds to approximately 40°C, and when the value of the NTC thermistor increases to 3.26 times the value of RNOM , which corresponds to approximately 0°C. Hold mode freezes the timer and stops the charge cycle until the thermistor indicates a return to a valid temperature. For a Vishay NTHS0603N01N1003J thermistor, this value is 32.6k which corresponds to approximately 0°C. The hot and cold comparators each have approximately 3°C of hysteresis to prevent oscillation about the trip point. When the charger is in Hold mode (battery temperature is either too hot or too cold) the CHRG pin pulses in a 2Hz, 25% duty cycle frequency unless the charge task is finished or the battery is assumed to be defective. If the NTC pin is grounded, the NTC function will be disabled. 406944fa 10 LTC4069-4.4 OPERATION VCC RNOM 0.76 • VCC 6 NTC RNTC – + TOO COLD – 0.35 • VCC + TOO HOT + NTC_ENABLE 0.016 • VCC – 4069 F03 Figure 3. NTC Circuit Information APPLICATIONS INFORMATION Undervoltage Charge Current Limiting (UVCL) The LTC4069-4.4 includes undervoltage charge (ΔVUVCL1) current limiting that prevents full charge current until the input supply voltage exceeds approximately 220mV above the battery voltage. This feature is particularly useful if the LTC4069-4.4 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 LTC4069-4.4 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 + ΔVUVCL1 (approximately 220mV above the battery voltage), undervoltage charge current limiting will begin to reduce the charge current in an attempt to maintain ΔVUVCL1 between the VCC input and the BAT output of the IC. The LTC4069-4.4 will continue to operate at the reduced charge current until the input supply voltage is increased or constant-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 LTC4069-4.4 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 used, the charger’s peak power dissipation can exceed 1W. Now consider the same scenario, but with a 5V input supply with a 600mA current limit. To take advantage of the current limited supply, it is necessary to program the LTC4069-4.4 to charge at a current above 600mA. Assume that the LTC4069-4.4 is programmed for 750mA (i.e., RPROG = 1.33k) to ensure that part tolerances maintain 406944fa 11 LTC4069-4.4 APPLICATIONS INFORMATION a programmed current higher than 600mA. Since the LTC4069-4.4 will demand a charge current higher than the current limit of the input supply, the supply voltage will drop to the battery voltage plus 600mA times the onresistance of the internal PFET. The on-resistance of the LTC4069-4.4 power device is approximately 450mΩ 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 180mW. That is a 82% improvement over the non-current limited supply power dissipation. USB and Wall Adapter Power Although the LTC4069-4.4 allows charging from a USB port, a wall adapter can also be used to charge Li-Ion batteries. Figure 4 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. Stability Considerations The LTC4069-4.4 contains two control loops: constantvoltage and constant-current. The constant-voltage loop is stable without any compensation when a battery is connected with low impedance leads. Excessive lead 5V WALL ADAPTER 750mA ICHG USB POWER 500mA ICHG ICHG SYSTEM LOAD BAT D1 High value capacitors with very low ESR (especially ceramic) may reduce the constant-voltage loop phase margin. Ceramic capacitors up to 22μF may be used in parallel with a battery, but larger ceramics should be decoupled with 0.2Ω to 1Ω 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 ≤ 1 • CPROG 2π • 105 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 5. A 10k resistor has been added between the PROG pin and the filter capacitor to ensure stability. LTC4069-4.4 VCC MP1 length, however, may add enough series inductance to require a bypass capacitor of at least 1μF from BAT to GND. Furthermore, a 4.7μF capacitor with a 0.2Ω to 1Ω series resistor from BAT to GND is required to keep ripple voltage low when the battery is disconnected. + PROG MN1 4.02k Li-Ion BATTERY LTC4069-4.4 10k PROG 2k GND 1k 4069 F04 Figure 4. Combining Wall Adapter and USB Power RPROG CFILTER CHARGE CURRENT MONITOR CIRCUITRY 4069 F05 Figure 5. Isolating Capacitive Load on the PROG Pin and Filtering 406944fa 12 LTC4069-4.4 APPLICATIONS INFORMATION Power Dissipation The conditions that cause the LTC4069-4.4 to reduce charge current through thermal feedback can be approximated by considering the power dissipated in the IC. For high charge currents, the LTC4069-4.4 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 LTC4069-4.4 will automatically reduce the charge current to maintain the die temperature at approximately 115°C. However, the approximate ambient temperature at which the thermal feedback begins to protect the IC is: TA = 115°C – PD • θJA TA = 115°C – (VCC – VBAT) • IBAT • θJA Example: Consider an LTC4069-4.4 operating from a 5V wall adapter providing 750mA to a 3.6V Li-Ion battery. The ambient temperature above which the LTC40694.4 will begin to reduce the 750mA charge current is approximately: TA = 115°C – (5V – 3.6V) • (750mA) • 60°C/W 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 LTC4069-4.4 applications do not need to be designed for worst-case thermal conditions since the IC will automatically limit power dissipation when the junction temperature reaches approximately 115°C. 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 LTC4069-4.4 package is soldered to the PC board copper and extending out to relatively large copper areas or internal copper layers connected using vias. Correctly soldered to a 2500mm2 double-sided 1 oz. copper board the LTC4069-4.4 has a thermal resistance of approximately 60°C/W. Failure to make thermal contact between the Exposed Pad on the backside of the package and the copper board will result in thermal resistances far greater than 60°C/W. As an example, a correctly soldered LTC4069-4.4 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. TA = 115°C – (1.05W • 60°C/W) = 115°C – 63°C VCC Bypass Capacitor TA = 52°C Many types of capacitors can be used for input bypassing; however, caution must be exercised when using multi-layer 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. The LTC4069-4.4 can be used above 70°C, but the charge current will be reduced from 750mA. The approximate current at a given ambient temperature can be calculated: IBAT = 115°C – TA ( VCC – VBAT ) • θJA Using the previous example with an ambient temperature of 73°C, the charge current will be reduced to approximately: IBAT = 115°C – 73°C 42°C = = 500mA (5V – 3.6V ) • 60°C/W 84°C/A 406944fa 13 LTC4069-4.4 APPLICATIONS INFORMATION To calculate RNOM for a shift to lower temperature for example, use the following equation: VCC RNOM 8.87k 0.76 • VCC 6 – + NTC RNOM = TOO COLD where RCOLD is the resistance ratio of RNTC at the desired cold temperature trip point. If you want to shift the trip points to higher temperatures use the following equation: R1 604Ω – RNTC 10k 0.35 • VCC + TOO HOT RNOM = + NTC_ENABLE 0.016 • VCC RCOLD • RNTC at 25 °C 3 . 266 – 4069 F06 Figure 6. NTC Circuits Thermistors The LTC4069-4.4 NTC trip points are designed to work with thermistors whose resistance-temperature characteristics follow Vishay Dale’s “R-T Curve 1.” The Vishay NTHS0603N01N1003J is an example of such a thermistor. However, Vishay Dale has many thermistor products that follow the “R-T Curve 1” characteristic in a variety of sizes. Furthermore, any thermistor whose ratio of RCOLD to RHOT is about 6 will also work (Vishay Dale R-T Curve 1 shows a ratio of RCOLD to RHOT of 3.266/0.5325 = 6.13). Designers may want to use thermistors whose room temperature value is different than 100k. Vishay Dale has a number of values of thermistor from 32k to 100k that follow the “R-T Curve 1.” Using different R-T curves, such as Vishay Dale “R-T Curve 2”, is also possible. This curve, combined with LTC4069-4.4 internal thresholds, gives temperature trip points of approximately –3°C (falling) and 42°C (rising), a delta of 45°C. This delta in temperature can be moved in either direction by changing the value of RNOM with respect to RNTC. Increasing RNOM will move both trip points to higher temperatures. RHOT • RNTC at 25 °C 0 . 5325 where RHOT is the resistance ratio of RNTC at the desired hot temperature trip point. Here is an example using a 10k R-T Curve 2 thermistor from Vishay Dale. The difference between the trip points is 45°C, from before, and we want the cold trip point to be 0°C, which would put the hot trip point at 45°C. The RNOM needed is calculated as follows: RNOM = = RCOLD • RNTC at 25 °C 3 . 266 2 . 816 • 10k = 8 . 62k 3 . 266 The nearest 1% value for RNOM is 8.66k. This is the value used to bias the NTC thermistor to get cold and hot trip points of approximately 0°C and 45°C respectively. To extend the delta between the cold and hot trip points, a resistor, R1, can be added in series with RNTC (see Figure 6). The values of the resistors are calculated as follows: RNOM = RCOLD − RHOT 3 . 266 − 0 . 5325 0 . 5325 ⎛ ⎞ • (RCOLD − RHOT ) − RHOT R1 = ⎜ ⎝ 3 . 266 − 0 . 5325 ⎟⎠ where RNOM is the value of the bias resistor and RHOT and RCOLD are the values of RNTC at the desired temperature trip points. Continuing the example from before with a desired trip point of 50°C: 406944fa 14 LTC4069-4.4 10k • ( 2.816 − 0.44086 ) RCOLD − RHOT = 3.266 − 0.5325 3.266 − 0.5325 = 8.8k, 8.87k is the nearest 1% value. RNOM = 0.5325 ⎞ ⎛ • ( 2.816 − 0.4086 ) − 0.4086 R1 = 10k • ⎜ ⎝ 3.266 − 0.5325 ⎟⎠ = 604Ω, 604 is the nearest 1% value. The cold trip point error depends on the tolerance of the NTC thermistor and the degree to which the ratio of its value at 0°C and its value at 40°C varies from 6.14 to 1. Therefore, the cold trip point error can be calculated using the tolerance, TOL, the temperature coefficient of the thermistor at 0°C, TC (in %/°C), the value of the thermistor at 0°C, RCOLD , and the value of the thermistor at 40°C, RHOT. The formula is: NTC Trip Point Error When a 1% resistor is used for RHOT, the major error in the 40°C trip point is determined by the tolerance of the NTC thermistor. A typical 100k NTC thermistor has ±10% tolerance. By looking up the temperature coefficient of the thermistor at 40°C, the tolerance error can be calculated in degrees centigrade. Consider the Vishay NTHS0603N01N1003J thermistor, which has a temperature coefficient of – 4%/°C at 40°C. Dividing the tolerance by the temperature coefficient, ±5%/(4%/°C) = ±1.25°C, gives the temperature error of the hot trip point. Temperature Error(°C) = ⎛ 1+ TOL RCOLD ⎞ − 1⎟ • 100 ⎜⎝ 6.14 • R ⎠ HOT TC For example, the Vishay NTHS0603N01N1003J thermistor with a tolerance of ±5%, TC of –5%/°C and RCOLD/RHOT of 6.13, has a cold trip point error of: ⎛ 1+ 0.05 ⎞ ⎜⎝ 6.14 • 6.13 − 1⎟⎠ • 100 Temperature Error(°C) = −5 = −0.95°C, 1.05°C PACKAGE DESCRIPTION DC Package 6-Lead Plastic DFN (2mm × 2mm) (Reference LTC DWG # 05-08-1703) R = 0.115 TYP 0.56 ± 0.05 (2 SIDES) 0.675 ±0.05 2.50 ±0.05 1.15 ±0.05 0.61 ±0.05 (2 SIDES) PIN 1 BAR PACKAGE TOP MARK OUTLINE (SEE NOTE 6) 0.38 ± 0.05 4 2.00 ±0.10 (4 SIDES) PIN 1 CHAMFER OF EXPOSED PAD 3 0.25 ± 0.05 0.50 BSC 0.200 REF 1 (DC6) DFN 1103 0.25 ± 0.05 0.50 BSC 0.75 ±0.05 1.37 ±0.05 (2 SIDES) 1.42 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 6 0.00 – 0.05 BOTTOM VIEW—EXPOSED PAD 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 406944fa 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. 15 LTC4069-4.4 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1734 Lithium-Ion Linear Battery Charger in ThinSOTTM Simple ThinSOT Charger, No Blocking Diode, No Sense Resistor Needed LTC1734L Lithium-Ion Linear Battery Charger in ThinSOT Low Current Version of LTC1734, 50mA ≤ ICHRG ≤ 180mA LTC4002 Switch Mode Lithium-Ion Battery Charger Standalone, 4.7V ≤ VIN ≤ 24V, 500kHz Frequency, 3 Hour Charge Termination LTC4050 Lithium-Ion Linear Battery Charger Controller Features Preset Voltages, C/10 Charger Detection and Programmable Timer, Input Power Good Indication, Thermistor Interface LTC4052 Monolithic Lithium-Ion Battery Pulse Charger No Blocking Diode or External Power FET Required, ≤1.5A Charge Current LTC4053 USB Compatible Monolithic Li-Ion Battery Charger Standalone Charger with Programmable Timer, Up to 1.25A Charge Current LTC4054 Standalone Linear Li-Ion Battery Charger with Integrated Pass Transistor in ThinSOT Thermal Regulation Prevents Overheating, C/10 Termination, C/10 Indicator, Up to 800mA Charge Current LTC4057 Lithium-Ion Linear Battery Charger Up to 800mA Charge Current, Thermal Regulation, ThinSOT Package LTC4058 Standalone 950mA Lithium-Ion Charger in DFN C/10 Charge Termination, Battery Kelvin Sensing, ±7% Charge Accuracy Battery Chargers LTC4059/LTC4059A 900mA Linear Lithium-Ion Battery Charger 2mm × 2mm DFN Package, Thermal Regulation, Charge Current Monitor Output, Version A has ACPR Function LTC4061 Standalone Li-Ion Charger with Thermistor Interface 4.2V, ±0.35% Float Voltage, Up to 1A Charge Current, 3mm × 3mm DFN LTC4061-4.4 Standalone Li-Ion Charger with Thermistor Interface 4.4V (Max), ±0.4% Float Voltage, Up to 1A Charge Current, 3mm × 3mm DFN LTC4062 Standalone Linear Li-Ion Battery Charger with Micropower Comparator 4.2V, ±0.35% Float Voltage, Up to 1A Charge Current, 3mm × 3mm DFN LTC4063 Li-Ion Charger with Linear Regulator Up to 1A Charge Current, 100mA, 125mV LDO, 3mm × 3mm DFN LTC4065/LTC4065A Standalone Li-Ion Battery Charger 4.2V, ±0.6% Float Voltage, Up to 750mA Charge Current, 2mm × 2mm DFN, Version A has ACPR Function LTC4069 Standalone Li-Ion Battery Charger with NTC Thermistor Input in 2 × 2 DFN 4.2V, ±0.6% Float Voltage, Up to 750mA Charge Current, Timer Termination, + C/10 Detection Output LTC4411/LTC4412 Low Loss PowerPathTM Controller in ThinSOT Automatic Switching Between DC Sources, Load Sharing, Replaces ORing Diodes Power Management LTC3405/LTC3405A 300mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converter 95% Efficiency, VIN: 2.7V to 6V, VOUT = 0.8V, IQ = 20μA, ISD < 1μA, ThinSOT Package LTC3406/LTC3406A 600mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converter 95% Efficiency, VIN: 2.5V to 5.5V, VOUT = 0.6V, IQ = 20μA, ISD < 1μA, ThinSOT Package LTC3411 1.25A (IOUT), 4MHz, Synchronous Step-Down DC/DC Converter 95% Efficiency, VIN: 2.5V to 5.5V, VOUT = 0.8V, IQ = 60μA, ISD < 1μA, MS Package LTC3440 600mA (IOUT), 2MHz, Synchronous Buck-Boost DC/DC Converter 95% Efficiency, VIN: 2.5V to 5.5V, VOUT = 2.5V, IQ = 25μA, ISD < 1μA, MS Package LTC4413 Dual Ideal Diode in DFN 2-Channel Ideal Diode ORing, Low Forward ON Resistance, Low Regulated Forward Voltage, 2.5V ≤ VIN ≤ 5.5V ThinSOT is a trademark of Linear Technology Corporation. 406944fa 16 Linear Technology Corporation LT 0908 REV A• PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2005