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1 ltc4069 4069fa descriptio u wireless pdas cellular phones portable electronics standalone 750ma li-ion battery charger in 2 2 dfn with ntc thermistor input 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 4.2v 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 20 a supply current in shutdown mode soft-start limits inrush current tiny 6-lead (2mm 2mm) dfn package features applicatio s u typical applicatio u the ltc ? 4069 is a complete constant-current/constant- voltage linear charger for single-cell lithium-ion batteries. the 2mm 2mm dfn package and low external compo- nent count make the ltc4069 especially well-suited for portable applications. furthermore, ltc4069 is specifi- cally 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 manufac- turer specifications. no external sense resistor or blocking diode is required due to the internal mosfet architecture. thermal feed- back 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 automatically enters a low current state, dropping battery drain current to less than 1 a. with power applied, ltc4069 can be put into shutdown mode, reducing the supply current to less than 20 a. the ltc4069 also includes automatic recharge, low- battery charge conditioning (trickle charging), soft-start (to limit inrush current) and an ntc thermistor input used to monitor battery temperature. the ltc4069 is available in a tiny 6-lead, low profile (0.75mm) 2mm 2mm dfn package. standalone li-ion battery charger + v cc r1 510 ? 500ma r prog 2k 4069 ta01 4.2v li-ion battery v in 4.3v to 5.5v 1 f ltc4069 chrg ntc bat prog gnd r nom 100k r ntc 100k , 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. time (hours) 0 charge current (ma) 200 400 600 100 300 500 1234 4069 ta01b 3.00 battrey voltage (v) 3.50 4.00 4.50 3.25 3.75 4.25 5 0.5 0 1.5 2.5 3.5 4.5 constant current constant voltage v cc = 5v r prog = 2k chrg transition charge termination complete charge cycle (1000mah battery)
2 ltc4069 4069fa symbol parameter conditions min typ max units v cc v cc supply voltage (note 4) 3.75 5.5 v i cc quiescent v cc supply current v bat = 4.5v (forces i bat and i prog = 0) 120 250 a i ccms v cc supply current in shutdown float prog 20 40 a i ccuv v cc supply current in undervoltage v cc < v bat , v cc = 3.5v, v bat = 4v 611 a lockout v float v bat regulated output voltage i bat = 2ma 4.175 4.2 4.225 v i bat = 2ma, 0 c < t a < 85 c 4.158 4.2 4.242 v i bat bat pin current r prog = 10k (0.1%), current mode 88 100 112 ma r prog = 2k (0.1%), current mode 475 500 525 ma i bms battery drain current in shutdown floating prog, v cc > v bat C1 0 1 a mode i buv battery drain current in undervoltage v cc = 3.5v, v bat = 4v 014 a lockout v uvlo v cc undervoltage lockout voltage v cc rising 3.4 3.6 3.8 v v cc falling 2.8 3.0 3.2 v v prog prog pin voltage r prog = 2k, i prog = 500 a 0.98 1 1.02 v r prog = 10k, i prog = 100 a 0.98 1 1.02 v v asd automatic shutdown threshold (v cc C v bat ), v cc low to high 60 82 100 mv voltage (v cc C v bat ), v cc high to low 15 32 45 mv i prog prog pin pull-up current v prog > 1v 3 a v cc t < 1ms and duty cycle < 1% ................. C 0.3v to 7v steady state ........................................... C 0.3v to 6v bat, chrg ................................................. C0.3v to 6v prog, ntc ..................................... C0.3v to v cc + 0.3v bat short-circuit duration ........................... continuous bat pin current ................................................. 800ma prog pin current ............................................... 800 a junction temperature (note 6) ............................ 125 c operating temperature range (note 2) .. C 40 c to 85 c storage temperature range ................ C 65 c to 125 c absolute axi u rati gs w ww u package/order i for atio uu w (note 1) ltc4069edc t jmax = 125 c, ja = 60 c/w (note 3) exposed pad (pin 7) is gnd must be soldered to pcb the denotes specifications which apply over the full operating temperature range, otherwise specifications are t a = 25 c. v cc = 5v, v bat = 3.8v, v ntc = 0v unless otherwise specified. (note 2) electrical characteristics order part number dc part marking consult ltc marketing for parts specified with wider operating temperature ranges. 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/ top view 7 dc package 6-lead (2mm 2mm) plastic dfn 4 5 6 3 2 1 gnd chrg bat prog ntc v cc lbzx
3 ltc4069 4069fa symbol parameter conditions min typ max units v ms,prog prog shutdown threshold voltage v prog rising 3.7 4 4.3 v t ss soft-start time 170 s i trkl trickle charge current v bat = 2v, r prog = 2k (0.1%) 35 50 65 ma v trkl trickle charge threshold voltage v bat rising 2.7 2.9 3.05 v v trhys trickle charge hysteresis voltage 90 mv ? v rechrg recharge battery threshold voltage v float C v rechrg , 0 c < t a < 85 c 70 100 130 mv ? v uvcl1 (v cc C v bat ) undervoltage current i bat = 90% programmed charge current 180 220 330 mv ? v uvcl2 limit i bat = 10% programmed charge current 90 125 150 mv t timer termination timer 3 4.5 6 hrs recharge timer 1.5 2.25 3 hrs low-battery trickle charge time v bat = 2.5v 0.75 1.125 1.5 hrs v chrg chrg pin output low voltage i chrg = 5ma 60 105 mv i chrg chrg pin leakage current v bat = 4.5v, v chrg = 5v 01 a i c/10 end of charge indication current r prog = 2k (note 5) 0.08 0.095 0.11 ma/ma level t lim junction temperature in constant 115 c temperature mode r on power fet on resistance i bat = 350ma 450 m ? (between v cc and bat) f badbat defective battery detection chrg 2 hz pulse frequency d badbat defective battery detection chrg 75 % pulse frequency duty ratio i ntc ntc pin current v ntc = 2.5v 1 a v cold cold temperature fault threshold rising voltage threshold 0.76 ? v cc v voltage hysteresis 0.015 ? v cc v v hot hot temperature fault threshold falling voltage threshold 0.35 ? v cc v voltage hysteresis 0.017 ? v cc v v ntc-dis ntc disable threshold voltage falling threshold; v cc = 5v 82 mv v dis-hys ntc disable hysteresis voltage 50 mv f ntc fault temperature chrg pulse 2hz frequency d ntc fault temperature chrg pulse 25 % frequency duty ratio the denotes specifications which apply over the full operating temperature range, otherwise specifications are t a = 25 c. v cc = 5v, v bat = 3.8v, v ntc = 0v unless otherwise specified. (note 2) electrical characteristics 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 is guaranteed to meet performance specifications from 0 c to 70 c. specifications over the C40 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 functions properly at 3.75v, full charge current requires an input voltage greater than the desired final battery voltage per the ? v uvcl1 specification. note 5: i c/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.
4 ltc4069 4069fa typical perfor a ce characteristics uw battery regulation (float) voltage vs battery charge current i bat (ma) 0 v float (v) 4.19 4.20 4.21 300 500 4069 g01 4.18 4.17 4.16 100 200 400 4.22 4.23 4.24 v cc = 5v t a = 25 c r prog = 2k temperature ( c) C50 v float (v) 4.23 25 4069 g02 4.20 4.18 C25 0 50 4.17 4.16 4.24 4.22 4.21 4.19 75 100 supply voltage (v) 4 v float (v) 4.20 4.21 4.22 6 4069 g03 4.19 4.18 4.16 4.5 5 5.5 4.17 4.24 4.23 t a = 25 c i bat = 2ma r prog = 2k battery regulation (float) voltage vs temperature battery regulation (float) voltage vs supply voltage charge current vs supply voltage (constant current mode) charge current vs battery voltage charge current vs ambient temperature with thermal regulation (constant current mode) supply voltage (v) 4 0 i bat (ma) 25 50 75 100 125 150 175 200 4.5 5 5.5 6 4069 g04 r prog = 10k v bat = 3.8v t a = 25 c v bat (v) 0 0 i bat (ma) 100 200 300 400 500 600 1234 4069 g05 5 v cc = 5v t a = 25 c r prog = 2k prog pin voltage vs temperature (constant current mode) prog pin voltage vs charge current power fet on resistance vs temperature temperature ( c) C50 v prog (v) 1.01 1.02 25 75 4069 g07 1.00 C25 0 50 100 0.99 0.98 v cc = 5v v bat = 3.8v r prog = 10k i bat (ma) 0 0 v prog (v) 0.2 0.4 0.6 0.8 1.0 1.2 100 200 300 400 4069 g08 500 v cc = 5v t a = 25 c r prog = 2k temperature ( c) C50 300 r ds (m ? ) 350 400 450 500 550 C25 02550 4069 g09 75 100 v cc = 4v i bat = 400ma temperature ( c) C50 0 i bat (ma) 100 200 300 400 050 100 150 4069 g06 500 600 thermal control loop in operation v cc = 5v v bat = 3.8v r prog = 2k
5 ltc4069 4069fa typical perfor a ce characteristics uw chrg pin output low voltage vs temperature temperature ( c) C50 80 100 140 25 75 4069 g10 60 40 C25 0 50 100 20 0 120 v chrg (mv) v cc = 5v i chrg = 5ma trickle charge current vs supply voltage supply voltage (v) 4 0 i bat (ma) 10 20 30 40 50 60 4.5 5 5.5 6 4069 g14 r prog = 2k r prog = 10k v bat = 2v t a = 25 c trickle charge current vs temperature temperature ( c) C50 i bat (ma) 40 50 60 25 75 4069 g15 30 20 C25 0 50 100 10 0 r prog = 2k r prog = 10k v cc = 5v v bat = 2v undervoltage lockout threshold voltage vs temperature temperature ( c) C50 2.50 v cc (v) 2.75 3.00 3.25 3.50 4.00 C25 025 rise fall 50 4069 g16 75 100 3.75 timer accuracy vs temperature timer accuracy vs supply voltage temperature ( c) C50 timer accuracy (%) C4 C3 C2 25 75 4069 g18 C5 C6 C7 C25 0 50 C1 0 1 100 v cc = 5v supply voltage (v) 4 timer accuracy (%) 0 1.0 6 4069 g19 C1.0 C2.0 4.5 5 5.5 2.0 C0.5 0.5 C1.5 1.5 t a = 25 c prog pin shutdown voltage threshold vs temperature prog pin shutdown voltage vs supply voltage temperature ( c) C50 3.0 v ms(prog) (v) 3.5 4.0 4.5 5.0 C25 0 25 50 4069 g20 75 100 v cc = 5v supply voltage (v) 4 v ms(prog) (v) 2.0 3.0 4.0 5.0 2.5 3.5 4.5 4.5 5 5.5 4069 g21 6 t a = 25 c
6 ltc4069 4069fa uu u 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 (75% duty cycle). when the ntc pin voltage rises above 0.76 ? v cc or drops below 0.35 ? v cc , 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 4.2v. an internal precision resistor divider on this pin sets the float voltage and is disconnected in shutdown mode. v cc (pin 4): positive input supply voltage. this pin provides power to the charger. v cc can range from 3.75v to 5.5v. this pin should be bypassed with at least a 1 f capacitor. when v cc is within 32mv of the bat pin voltage, the ltc4069 enters shutdown mode, dropping i bat to about 1 a. 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 v cc . when the voltage at this pin drops below 0.35 ? v cc at hot temperatures or rises above 0.76 ? v cc 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 ? v cc disables the ntc feature. there is approximately 3 c of temperature hysteresis associ- ated with each of the input comparators thresholds. prog (pin 6): charge current program and charge cur- rent monitor pin. connecting a 1% resistor, r prog , 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: i v r bat prog prog = ? 1000 floating the prog pin puts the charger in shutdown mode. in shutdown mode, the ltc4069 has less than 20 a supply current and about 1 a battery drain current. exposed pad (pin 7): ground. the exposed pad must be soldered to the pcb ground to provide both electrical con- tact and rated thermal performance.
7 ltc4069 4069fa figure 1. ltc4069 block diagram operatio u the ltc4069 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 low-battery conditioning adhere to battery manufacturer safety guidelines. furthermore, the ltc4069 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 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 or external components. another benefit of the ltc4069 thermal limit is that charge current can be set according to typical, not worst-case, ambient temperatures for a given C + C + C+ C+ 2 + mp m2 1 m1 1000 v cc v cc r1 r2 min enable r3 r4 r5 2.9v chrg 6 prog 1 gnd 4069 f01 r prog bat 1v prog c/10 c1 C + ta t die 115 c 0.1v 1.2v suspend d3 too hot too cold ntc_en 0.1v d2 3.6v d1 1.2v C+ ref ca ma lobat 5 r7 ntc r8 r9 r10 v cc v cc C + uvlo 3 4 bat logic counter oscillator charge control C+ C + c3 C + c2 c5 va 4v C + shutdown suspend or and r nom r ntc c4 si plified w block diagra w
8 ltc4069 4069fa operatio u application with the assurance that the charger will auto- matically reduce the current in worst-case conditions. the charge cycle begins when the voltage at the v cc 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 ? v cc and 0.35 ? v cc or below 0.016 ? v cc . 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 ltc4069 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, t timer (typi- cally 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 v rechrg (typically 4.1v). to manu- ally restart the charge cycle, remove the input voltage and reapply it, or momentarily float the prog pin and recon- nect 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: r v i i v r prog chg chg prog == 1000 1 1000 ?, 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: i v r bat prog prog = ? 1000 undervoltage lockout (uvlo) an internal undervoltage lockout circuit monitors the input voltage and keeps the charger in undervoltage lockout until v cc 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 shut- down threshold has a built-in hysteresis of approximately 50mv. during undervoltage lockout conditions, maxi- mum battery drain current is 4 a and maximum supply current is 11 a. shutdown mode the ltc4069 can be disabled by floating the prog pin. in shutdown mode, the battery drain current is reduced to less than 1 a and the supply current to about 20 a. timer and recharge the ltc4069 has an internal termination timer that starts when an input voltage greater than the undervoltage lockout threshold is applied to v cc , 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 pre- vented since the battery is at or near full capacity. once the charge cycle terminates, the ltc4069 continu- ously monitors the bat pin voltage using a comparator with a 2ms filter time. when the battery voltage falls below 4.1v (which corresponds to 80% to 90% battery capac- ity), 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 peri- odic charge cycle initiations. also, if the battery voltage
9 ltc4069 4069fa operatio u 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 dis- charged battery), 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: pull- down, 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 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 ltc4069 is disabled. figure 2 shows the chrg status under various conditions. charge current soft-start and soft-stop the ltc4069 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 170 s. likewise, internal circuitry slowly ramps the charge cur- rent 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 uses a unique architecture to charge a battery in a constant-current, constant-voltage and con- stant-temperature fashion. figure 1 shows a simplified block diagram of the ltc4069. 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 constant- voltage 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. transconductance amplifier, ta, limits the die tempera- ture to approximately 115 c when in constant-tempera- ture mode. diode d3 ensures that ta does not affect the charge current when the die temperature is below approxi- mately 115 c. the prog pin voltage continues to give an indication of the charge current. in typical operation, the charge cycle begins in constant- current mode with the current delivered to the battery equal to 1000v/r prog . if the power dissipation of the ltc4069 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 either returns to constant-current mode or enters constant- voltage mode straight from constant-temperature mode.
10 ltc4069 4069fa operatio u figure 2. state diagram of ltc4069 operation 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, r ntc , between the ntc pin and ground and a resistor, r nom , from the ntc pin to v cc . r nom should be a 1% resistor with a value equal to the value of the chosen ntc ther- mistor at 25 c (this value is 10k for a vishay nths0603no1n1002j thermistor). the ltc4069 goes into hold mode when the value of the ntc thermistor drops to 0.53 times the value of r nom , which corresponds to approximately 40 c, and when the value of the ntc thermistor increases to 3.26 times the value of r nom , 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 nths0603no1n1002j 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. if v cc > 3.6v and v cc > v bat + 80mv? uvlo uvlo mode 1/10 full charge current chrg strong pull-down trickle charge mode full charge current chrg strong pull-down fast charge mode is v bat < 2.9v? defective battery is v bat < 4.1v? recharge no charge current chrg pulses (2hz) bad battery mode full charge current chrg strong pull-down recharge mode chrg high impedance yes yes no no 4069 f02 v bat 2.9v 1/4 charge cycle (1.125 hours) v cc < 3v charge cycle (4.5 hours) 1/2 charge cycle (2.25 hours) 2.9v < v bat < 4.1v v bat > 4.1v yes no no charge current chrg high impedance standby mode power on battery charging suspended chrg pulses (2hz) ntc fault temperature ok temperature not ok temperature not ok
11 ltc4069 4069fa undervoltage charge current limiting (uvcl) the ltc4069 includes undervoltage charge ( ? v uvcl1 ) current limiting that prevents full charge current until the input supply voltage exceeds approximately 200mv above the battery voltage. this feature is particularly useful if the ltc4069 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 imped- ance can easily trip the uvlo threshold and turn the charger off unless undervoltage charge current limiting is implemented. consider a situation where the ltc4069 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 v bat + ? v uvcl1 (approximately 220mv above the battery voltage), undervoltage charge current limiting will begin to reduce the charge current in an attempt to maintain ? v uvcl1 between the v cc input and the bat output of the ic. the ltc4069 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 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 chargers 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 to charge at a current above 600ma. assume that the ltc4069 is programmed for 750ma (i.e., r prog = 1.33k) to ensure that part tolerances maintain a pro- grammed current higher than 600ma. since the ltc4069 applicatio s i for atio wu uu figure 3. ntc circuit information operatio u 4069 f03 r nom r ntc v cc C + C + C + too cold too hot ntc_enable 0.76 ? v cc 0.35 ? v cc 0.016 ? v cc 6 ntc
12 ltc4069 4069fa 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 ltc4069 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 ltc4069 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 contains two control loops: constant-volt- age and constant-current. the constant-voltage loop is stable without any compensation when a battery is con- nected with low impedance leads. excessive lead length, however, may add enough series inductance to require a bypass capacitor of at least 1 f from bat to gnd. further- more, a 4.7 f 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 ce- ramic) may reduce the constant-voltage loop phase mar- gin. ceramic capacitors up to 22 f 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, addi- tional 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, c prog , the following equation should be used to calculate the maximum resis- tance value for r prog : r c prog prog 1 210 5 ?? 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 figure 5. isolating capacitive load on the prog pin and filtering applicatio s i for atio wu uu figure 4. combining wall adapter and usb power v cc mp1 mn1 1k 2k 4.02k i chg d1 li-ion battery system load 4069 f04 ltc4069 bat usb power 500ma i chg 5v wall adapter 750ma i chg prog + 4069 f05 c filter charge current monitor circuitry r prog ltc4069 prog gnd 10k
13 ltc4069 4069fa battery current as shown in figure 5. a 10k resistor has been added between the prog pin and the filter capacitor to ensure stability. power dissipation the conditions that cause the ltc4069 to reduce charge current through thermal feedback can be approximated by considering the power dissipated in the ic. for high charge currents, the ltc4069 power dissipation is approximately: p d = (v cc C v bat ) ? i bat where p d is the power dissipated, v cc is the input supply voltage, v bat is the battery voltage and i bat is the charge current. it is not necessary to perform any worst-case power dissipation scenarios because the ltc4069 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: t a = 115 c C p d ? ja t a = 115 c C (v cc C v bat ) ? i bat ? ja example: consider an ltc4069 operating from a 5v wall adapter providing 750ma to a 3.6v li-ion battery. the ambient temperature above which the ltc4069 will begin to reduce the 750ma charge current is approximately: t a = 115 c C (5v C 3.6v) ? (750ma) ? 60 c/w t a = 115 c C (1.05w ? 60 c/w) = 115 c C 63 c t a = 52 c the ltc4069 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: i ct vv bat a cc bat ja = () 115 C C? applicatio s i for atio wu uu using the previous example with an ambient temperature of 73 c, the charge current will be reduced to approxi- mately: i cc vv cw c ca ma bat = () = = 115 73 536 60 42 84 500 C C. ? / / 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 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 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 2500mm 2 double-sided 1 oz. copper board the ltc4069 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 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. v cc bypass capacitor 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 capaci- tors, 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.
14 ltc4069 4069fa thermistors the ltc4069 ntc trip points are designed to work with thermistors whose resistance-temperature characteris- tics follow vishay dales r-t curve 1. the vishay nths0603no1n1002j is an example of such a ther- mistor. however, vishay dale has many thermistor prod- ucts that follow the r-t curve 1 characteristic in a variety of sizes. furthermore, any thermistor whose ratio of r cold to r hot is about 5 will also work (vishay dale r-t curve 1 shows a ratio of r cold to r hot of 3.266/0.5325 = 6.13). power conscious designs may want to use thermistors whose room temperature value is greater than 10k. vishay dale has a number of values of thermistor from 10k to 100k that follow the r-t curve 1. using different r-t curves, such as vishay dale r-t curve 2, is also pos- sible. this curve, combined with ltc4069 internal thresh- olds, gives temperature trip points of approximately 0 c (falling) and 40 c (rising), a delta of 40 c. this delta in temperature can be moved in either direction by changing the value of r nom with respect to r ntc . increasing r nom will move both trip points to higher temperatures. to calculate r nom for a shift to lower temperature for ex- ample, use the following equation: r r ratc nom cold ntc = 3 266 25 . ? where r cold is the resistance ratio of r ntc at the desired cold temperature trip point. if you want to shift the trip points to higher temperatures use the following equation: r r ratc nom hot ntc = 0 5325 25 . ? where r hot is the resistance ratio of r ntc at the desired hot temperature trip point. here is an example using a 100k r-t curve 2 thermistor from vishay dale. the difference between the trip points is 40 c, from before, and we want the cold trip point to be 0 c, which would put the hot trip point at 40 c. the r nom needed is calculated as follows: r r ratc nom cold ntc = = 3 266 25 2 816 3 . ? . .. ?. 266 10 8 62 kk = the nearest 1% value for r nom 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 40 c respectively. to extend the delta between the cold and hot trip points, a resistor, r1, can be added in series with r ntc (see figure 6). the values of the resistors are calculated as follows: r rr r nom cold hot = ? ? = 3 266 0 5325 0 5325 3 266 1 .. . . ?? ? ? ? ? ? ? ? () ? 0 5325 . ?r r r cold hot hot where r nom is the value of the bias resistor and r hot and r cold are the values of r ntc at the desired temperature trip points. continuing the example from before with a desired trip point of 50 c: 4069 f06 r nom 8.87k r ntc 10k v cc C + C + C + too cold too hot ntc_enable r1 604 ? 0.76 ? v cc 0.35 ? v cc 0.016 ? v cc 6 ntc figure 6. ntc circuits applicatio s i for atio wu uu
15 ltc4069 4069fa 2.00 0.10 (4 sides) 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 0.38 0.05 bottom viewexposed pad 0.56 0.05 (2 sides) 0.75 0.05 r = 0.115 typ 1.37 0.05 (2 sides) 1 3 6 4 pin 1 bar top mark (see note 6) 0.200 ref 0.00 C 0.05 (dc6) dfn 1103 0.25 0.05 1.42 0.05 (2 sides) recommended solder pad pitch and dimensions 0.61 0.05 (2 sides) 1.15 0.05 0.675 0.05 2.50 0.05 package outline 0.25 0.05 0.50 bsc 0.50 bsc pin 1 chamfer of exposed pad u package descriptio dc package 6-lead plastic dfn (2mm 2mm) (reference ltc dwg # 05-08-1703) 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 represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. r rr k nom cold hot = ? ? = ? 3 266 0 5325 10 2 816 0 .. ?. . 44086 3 266 0 5325 88 887 () ? = .. .,. kkis %. ? . . the nearest value rk 1 10 0 5325 326 1 = 66 0 5325 2 816 0 4086 0 4086 ? ? ? ? ? ? ? ? () ? . ?. . . ,%. = 604 604 1 ? is the nearest value ntc trip point error when a 1% resistor is used for r hot , 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 tempera- ture coefficient of C4%/ 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. 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, r cold , and the value of the thermistor at 40 c, r hot . the formula is: temperature error c tol r r cold hot () . ? = + 1 614 ?? ? ? ? ? ? ? 1 100 ? tc for example, the vishay nths0603n01n1003j thermistor with a tolerance of 5%, tc of C5%/ c and r cold /r hot of 6.13, has a cold trip point error of: temperature error c () . . ?. = + ? ? ? 1005 614 613 1 ?? ? ? ? ? ? 100 5 .,. = ? 095 105 cc applicatio s i for atio wu uu
16 ltc4069 4069fa ? linear technology corporation 2005 lt 0406 rev a ? printed in the usa related parts linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com part number description comments battery chargers ltc1734 lithium-ion linear battery charger in thinsot tm simple thinsot charger, no blocking diode, no sense resistor needed ltc1734l lithium-ion linear battery charger in thinsot low current version of ltc1734, 50ma i chrg 180ma ltc4002 switch mode lithium-ion battery charger standalone, 4.7v v in 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 thermal regulation prevents overheating, c/10 termination, with integrated pass transistor in thinsot 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 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 4.2v, 0.35% float voltage, up to 1a charge current, 3mm 3mm dfn micropower comparator 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 ltc4411/ltc4412 low loss powerpath tm controller in thinsot automatic switching between dc sources, load sharing, replaces oring diodes power management ltc3405/ltc3405a 300ma (i out ), 1.5mhz, synchronous step-down 95% efficiency, v in : 2.7v to 6v, v out = 0.8v, i q = 20 a, i sd < 1 a, dc/dc converter thinsot package ltc3406/ltc3406a 600ma (i out ), 1.5mhz, synchronous step-down 95% efficiency, v in : 2.5v to 5.5v, v out = 0.6v, i q = 20 a, i sd < 1 a, dc/dc converter thinsot package ltc3411 1.25a (i out ), 4mhz, synchronous step-down 95% efficiency, v in : 2.5v to 5.5v, v out = 0.8v, i q = 60 a, i sd < 1 a, dc/dc converter ms package ltc3440 600ma (i out ), 2mhz, synchronous buck-boost 95% efficiency, v in : 2.5v to 5.5v, v out = 2.5v, i q = 25 a, i sd < 1 a, dc/dc converter ms package ltc4413 dual ideal diode in dfn 2-channel ideal diode oring, low forward on resistance, low regulated forward voltage, 2.5v v in 5.5v thinsot and powerpath are trademarks of linear technology corporation.

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