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ltc4053-4.2 1 4053f n cellular telephones n handheld computers n charging docks and cradles n mp3 players n digital cameras n charges single-cell li-ion batteries directly from usb port n thermal regulation maximizes charge rate without risk of overheating* n programmable charge current with 7% accuracy n low dropout operation n no external mosfet, sense resistor or blocking diode required n programmable charge termination timer n preset charge voltage with 1% accuracy n c/10 charge current detection output n ac present logic output n 25 m a supply current in shutdown mode n automatic recharge n tiny thermally enhanced 10-pin msop package n charge current monitor useful for gas gauging* n thermistor input for temperature qualified charging usb compatible lithium-ion battery charger with thermal regulation the ltc ? 4053 is a standalone linear charger for lithium- ion batteries that can be powered directly from a usb port. the ic contains an on-chip power mosfet and eliminates the need for an external sense resistor and blocking diode. thermal regulation automatically adjusts charge current to limit die temperature during high power or high ambient temperature conditions. this feature protects the end product and the ltc4053 from thermal stress while the ic charges the battery at maximum rate without interruption. the charge current and charge time can be set externally with a single resistor and capacitor, respectively. when the input supply (wall adapter or usb supply) is removed, the ltc4053 automatically enters a low current sleep mode, dropping the battery drain current to less than 5 m a. the ltc4053 also includes ntc temperature sensing, c/10 detection circuitry, ac present logic, low battery charge conditioning (trickle charging) and shutdown (25 m a supply current). the ltc4053 is available in a 10-pin thermally enhanced msop package. , ltc and lt are registered trademarks of linear technology corporation. usb port 4.35v to 5.5v 4.7 f 4053ta01 4 2 usb control c li-ion battery system load + 0.1 f 15k 100ma/ 500ma suspend 3.74k shdn v cc gnd ntc 9 8 7 56 prog ltc4053-4.2 bat timer usb powered standalone li-ion charger *us patent 6522118 charge current vs input voltage v cc (v) 4.0 i bat (ma) 600 500 400 300 200 100 0 4.5 5.0 4053 g04 5.5 t a = 25 c r prog = 3k v bat = 3.95v v bat = 4.15v v bat = 4.05v features descriptio u applicatio s u typical applicatio u .com .com .com
ltc4053-4.2 2 4053f input supply voltage (v cc ) ....................................... 7v bat ........................................................................... 7v ntc, shdn, timer, prog ............ C0.3v to v cc + 0.3v chrg, fault, acpr .................................. C0.3v to 7v bat short-circuit duration .......................... continuous bat current (note 2) ............................................. 1.3a prog current (note 2) ....................................... 1.3ma junction temperature .......................................... 125 c operating temperature range (note 3) ...C40 c to 85 c storage temperature range ................ C 65 c to 150 c lead temperature (soldering, 10 sec)................. 300 c absolute axi u rati gs w ww u package/order i for atio uu w (note 1) electrical characteristics the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v cc = 5v symbol parameter conditions min typ max units v cc v cc supply voltage l 4.25 6.5 v i cc v cc supply current charger on; current mode; r prog = 30k (note 5) l 12 ma shutdown mode; v shdn = 0v l 25 50 m a sleep mode v cc < v bat or v cc 4v l 25 50 m a v bat v bat regulated float voltage l 4.158 4.2 4.242 v i bat battery pin current r prog = 3k; current mode l 465 500 535 ma r prog = 15k; current mode l 93 100 107 ma shutdown mode; v shdn = 0v 1 3 m a sleep mode v cc < v bat or v cc < (v uv C d v uv ) 1 3 m a i trikl trickle charge current v bat < 2v; r prog = 3k l 35 50 65 ma v trikl trickle charge trip threshold v bat rising 2.48 v d v trikl trickle charge trip hysteresis 100 mv v uv v cc undervoltage lockout voltage v cc rising l 4 4.25 v d v uv v cc undervoltage lockout hysteresis 200 mv v msd manual shutdown threshold voltage shdn pin voltage 0.6 1.3 v v asd automatic shutdown threshold voltage (v cc - v bat ) high to low 35 mv (v cc - v bat ) low to high 70 mv consult ltc marketing for parts specified with wider operating temperature ranges. order part number ltc4053emse-4.2 t jmax = 125 c, q ja = 40 c/w (note 4) exposed pad is ground. (must be soldered to pcb). 1 2 3 4 5 chrg v cc fault timer gnd 10 9 8 7 6 acpr bat shdn prog ntc top view mse exposed pad package 10-lead plastic msop mse part marking ltzt .com .com .com .com
ltc4053-4.2 3 4053f note 1: absolute maximum ratings are those values beyond which the life of a device may be impaired. note 2: the absolute maximum bat current rating of 1.3a is guaranteed by design and current density calculations. the absolute maximum prog current rating is guaranteed to be 1/1000 of bat current rating by design. note 3: the ltc4053e is guaranteed to meet performance specifications from 0 c to 70 c. specifications over the C40 c to 85 c operating symbol parameter conditions min typ max units v prog prog pin voltage r prog = 3k, i prog = 500 m a 1.5 v i chrg chrg pin weak pulldown current v chrg = 1v 15 30 50 m a v chrg chrg pin output low voltage i chrg = 5ma 0.35 0.6 v v acpr acpr pin output low voltage i acpr = 5ma 0.35 0.6 v v fault fault pin output low voltage i fault = 5ma 0.35 0.6 v i c/10 end of charge indication current level r prog = 3k 44 50 56 ma t timer timer accuracy c timer = 0.1 m f10% v rechrg recharge battery voltage threshold battery voltage falling 4.035 v v ntc-hot ntc pin hot threshold voltage v ntc falling 2.5 v v hot-hys ntc pin hot hysteresis voltage 80 mv v ntc-cold ntc pin cold threshold voltage v ntc rising 4.375 v v cold-hys ntc pin cold hystersis voltage 80 mv v ntc-dis ntc pin disable threshold voltage v ntc rising 100 mv v dis-hys ntc pin disable hystersis voltage 10 mv t lim junction temperature in 105 c constant-temperature mode r on power mosfet on resistance 375 m w temperature range are assured by design, characterization and correlation with statistical process controls. note 4: failure to solder the exposed backside of the package to the pc board will result in a thermal resistance much higher than 40 c/w. note 5: supply current includes prog pin current (approximately 50 m a) but does not include any current delivered to the battery through the bat pin (approximately 50ma). electrical characteristics the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v cc = 5v .com .com .com .com
ltc4053-4.2 4 4053f typical perfor a ce characteristics uw battery regulation voltage vs battery charge current i bat (ma) 4.16 v bat (v) 4.18 4.20 4.22 4.17 4.19 4.21 100 200 300 400 4053 g01 500 50 0 150 250 350 450 v cc = 5v t a = 25 c r prog = 3k temperature ( c) ?0 4.06 v bat (v) 4.08 4.12 4.14 4.16 50 4.24 4053 g02 4.10 0 ?5 75 100 25 125 4.18 4.20 4.22 v cc = 5v r prog = 3k i bat = 10ma v cc (v) 4 v bat (v) 4.5 5 5.5 6 4053 g03 6.5 4.210 4.208 4.206 4.204 4.202 4.200 4.198 4.196 4.194 4.192 4.190 7 v cc = 5v r prog = 3k i bat = 10ma battery regulation voltage vs temperature battery regulation voltage vs v cc charge current vs input voltage charge current vs battery voltage charge current vs ambient temperature with thermal regulation v cc (v) 4.0 i bat (ma) 600 500 400 300 200 100 0 4.5 5.0 4053 g04 5.5 t a = 25 c r prog = 3k v bat = 3.95v v bat = 4.15v v bat = 4.05v v bat (v) 0 i bat (ma) 150 450 500 550 1 2 2.5 4053 g05 50 350 250 100 400 0 300 200 0.5 1.5 3.5 4.5 3 4 v cc = 5v t a = 25 c r prog = 3k temperature ( c) ?0 0 i bat (ma) 200 400 600 ?5 0 25 50 4053 g06 75 800 1000 100 300 500 700 900 100 thermal control loop in operation v cc = 5v v bat = 3.5v r prog = 1.5k undervoltage lockout voltage vs temperature shutdown supply current vs temperature manual shutdown threshold voltage vs temperature temperature ( c) ?0 v uv (v) 3.95 3.97 3.98 3.99 4.05 4.02 0 50 75 4053 g07 3.96 4.03 4.04 4.01 4.00 ?5 25 100 125 temperature ( c) ?0 i cc ( a) 20 25 30 25 75 4053 g08 15 10 ?5 0 50 100 125 5 0 v shdn = 0v v cc = 6.5v v cc = 5.5v v cc = 4.5v temperature ( c) ?0 v msd (v) 0.80 0.90 0.95 1.00 1.30 1.15 0 50 75 4053 g09 0.85 1.20 1.25 1.10 1.05 ?5 25 100 125 v cc = 6v v cc = 5.5v v cc = 4.5v v cc = 5v .com .com .com .com
ltc4053-4.2 5 4053f typical perfor a ce characteristics uw prog pin voltage vs charge current prog pin voltage vs v cc constant current mode prog pin voltage vs temperature constant current mode charge current (ma) 0 v prog (v) 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 400 4052 g10 100 200 300 500 350 50 150 250 450 v cc = 5v t a = 25 c r prog = 3k v cc (v) 4 1.485 v prog (v) 1.490 1.495 1.500 1.505 1.515 4.5 5 5.5 6 4053 g11 6.5 7 1.510 v bat = 3.5v t a = 25 c r prog = 3k temperature ( c) ?0 1.485 v prog (v) 1.490 1.495 1.500 1.505 1.515 ?5 02550 4053 g12 75 100 1.510 v cc = 5v v bat = 4v r prog = 3k trickle charge current vs temperature chrg pin weak pull-down current vs temperature chrg pin output low voltage vs temperature temperature ( c) 50 ?5 7 i bat (% of programmed current) 9 12 0 50 75 4053 g13 8 11 10 25 100 125 v bat = 2v t a = 25 c r prog = 3k temperature ( c) ?0 25 i chrg ( a) 26 28 29 30 35 32 0 50 75 ltc1323 ?tpc05 27 33 34 31 ?5 25 100 125 v cc = 5v i bat < c/10 temperature ( c) ?0 v chrg (v) 0.4 0.5 0.6 25 75 4053 g15 0.3 0.2 ?5 0 50 100 125 0.1 0 v cc = 5v i chrg = 5ma timer error vs temperature temperature ( c) ?0 ? t timer (%) ? ? ? 0 5 2 0 50 75 ltc1323 ?tpc05 ? 3 4 1 ?5 25 100 125 v cc = 5v c timer = 0.1 f timer error vs v cc v cc (v) 4 ? t timer (%) ? ? 1 4.5 5 5.5 6 4056 g17 6.5 3 5 ? ? 0 2 4 7 t a = 25 c c timer = 0.1 f .com .com .com .com
ltc4053-4.2 6 4053f uu u pi fu ctio s chrg: open-drain charge status output. when the battery is being charged, the chrg pin is pulled low by an internal n-channel mosfet. when the charge current drops to 10% of the full-scale current, the n-channel mosfet latches off and a 30 m a current source is con- nected from the chrg pin to ground. the c/10 latch can be cleared by grounding the shdn pin, momentarily, or toggling v cc . when the timer runs out or the input supply is removed, the current source is disconnected and the chrg pin is forced high impedance. v cc : positive input supply voltage. when v cc is within 35mv of v bat or less than the undervoltage lockout threshold, the ltc4053 enters sleep mode, dropping i bat to less than 3 m a. v cc can range from 4.25v to 6.5v. bypass this pin with at least a 4.7 m f ceramic capacitor to ground. fault: open-drain fault status output. the fault open- drain logic signal indicates that the charger has timed out under trickle charge conditions or the ntc comparator is indicating an out-of-range battery temperature condition. if v bat is less that 2.48v, trickle charging begins whereby the charge current drops to one tenth of its programmed value and the timer period is reduced by a factor of four. when one fourth of the timing period has elapsed, if v bat is still less than 2.48v, trickle charging stops and the fault pin latches to ground. the fault can be cleared by toggling v cc , momentarily grounding the shdn pin or pulling the bat pin above 2.48v. if the ntc comparator is indicating an out-of-range battery temperature condition, the fault pin will pull to ground until the temperature returns to the acceptable range. timer: timer capacitor. the timer period is set by placing a capacitor, c timer , to ground. the timer period is: time (hours) = (c timer ? 3 hr)/(0.1 m f) short the timer pin to ground to disable the internal timer function. gnd: ground. the exposed backside of the package is also ground and must be soldered to the pc board for maxi- mum heat transfer. ntc: input to the ntc (negative temperature coefficient) thermistor temperature monitoring circuit. with an ex- ternal 10k w ntc thermistor to ground and a 1% resistor to v cc , this pin can sense the temperature of the battery pack and stop charging when it is out of range. when the voltage at this pin drops below (0.5)?(v cc ) at hot tempera- tures or rises above (0.875)?(v cc ) at cold, charging is suspended and the internal timer is frozen. the chrg pin output status is not affected in this hold state. the fault pin will be pulled to ground, but not latched. when the temperature returns to an acceptable range, charging will resume and the fault pin will be released. the ntc feature can be disabled by grounding the ntc pin. prog: charge current program and charge current moni- tor pin. the charge current is programmed by connecting a resistor, r prog to ground. when in constant-current mode, the ltc4053 servos the prog pin voltage to 1.5v. in all modes the voltage on the prog pin can be used to measure the charge current as follows: i bat = (v prog /r prog ) ? 1000. shdn: shutdown input pin. pulling the shdn pin to ground will put the ltc4053 into standby mode where the bat drain current is reduced to less than 3 m a, and the supply current is reduced to less than 25 m a. for normal operation, pull the shdn pin up to v cc . bat: charge current output. a bypass capacitor of at least 1 m f with a 1 w series resistor is required to keep the loop stable when the battery is not present. a precision internal resistor divider sets the final float potential on this pin. the internal resistor divider is disconnected in sleep and shutdown mode. acpr: open-drain power supply status output. when v cc is greater than the undervoltage lockout threshold and at least 35mv above v bat , the acpr pin will pull to ground. otherwise, the pin is high impedance. .com .com .com .com
ltc4053-4.2 7 4053f si plified w block diagra w figure 1 2.485v + + + + + 4053 bd hot cold disable stop fault charge oscillator counter timer c timer ntc ntc chrg acpr fault 30 a 2.485v to bat ref + c/10 acpr ta ca c2 c3 va ma prog bat v cc gnd r1 r3 r4 r5 r2 30 a 1.5v 0.15v 105 c t die d1 d2 d3 m2 1 m1 1000 mp r prog shdn logic shdn 2 6 1 10 3 475 8 9 c/10 .com .com .com .com
ltc4053-4.2 8 4053f the ltc4053 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 and a programmable timer for charge termination. charge current can be programmed up to 1.25a with a final float voltage accuracy of 1%. no blocking diode or sense resistor is required thus dropping the external component count to three for the basic charger circuit. the chrg, acpr, and fault open-drain status outputs provide information regarding the status of the ltc4053 at all times. an ntc thermistor input pro- vides the option of charge qualification using battery temperature. an internal thermal limit reduces the programmed charge current if the die temperature attempts to rise above a preset value of approximately 105 c. this feature protects the ltc4053 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 ltc4053 or the external components. another benefit of the ltc4053 thermal limit is that charge current can be set according to typical, not worst-case, ambient temperatures for a given 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 the uvlo level, a program resistor is con- nected from the prog pin to ground, and the shdn pin is pulled above the shutdown threshold. at the beginning of the charge cycle, if the battery voltage is below 2.48v, the charger goes into trickle charge mode to bring the cell voltage up to a safe level for charging. the charger goes into the fast charge constant-current mode once the voltage on the bat pin rises above 2.48v. in constant- current mode, the charge current is set by r prog . when the battery approaches the final float voltage, the charge current begins to decrease as the ltc4053 enters the constant-voltage mode. when the current drops to 10% of the full-scale charge current, an internal compara- tor latches off the mosfet on the chrg pin and connects a weak current source to ground (30 m a) to indicate a near end-of-charge (c/10) condition. the c/10 latch can be cleared by grounding the shdn pin momentarily, or momentarily removing and reapplying v cc . an external capacitor on the timer pin sets the total charge time. 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, or momentarily force the shdn pin to 0v. the charge cycle will also restart if the bat pin voltage falls below the recharge threshold. for lithium-ion and similar batteries that require an accu- rate final float voltage, the internal reference, voltage amplifier and the resistor divider provide regulation with 1% (max) accuracy. when the input voltage is not present, the charger goes into a sleep mode, dropping battery drain current, i bat , to less than 5 m a. this greatly reduces the current drain on the battery and increases the standby time. the charger can be shut down (i cc = 25 m a) by forcing the shdn pin to 0v. operatio u .com .com .com .com
ltc4053-4.2 9 4053f for example, if 500ma charge current is required, calculate: r prog = 1500v/0.5a = 3k w for best stability over temperature and time, 1% metal- film resistors are recommended. if the charger is in constant-temperature or constant- voltage mode, the battery current can be monitored by measuring the prog pin voltage as follows: i chg = (v prog / r prog ) ? 1000 usb and wall adapter power although the ltc4053 allows charging from a usb port, a wall adapter can also be used to charge li-ion batteries. figure 2 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 3k program resistor can be used to increase the charge current to 1a when the wall adapter is present. applicatio s i for atio wu u u undervoltage lockout (uvlo) an internal undervoltage lockout circuit monitors the input voltage and keeps the charger in shutdown mode until v cc rises above the undervoltage lockout threshold. the uvlo circuit has a built-in hysteresis of 150mv. furthermore, to protect against reverse current in the power mosfet, the uvlo circuit keeps the charger in shutdown mode if v cc falls to within 35mv of the battery voltage. if the uvlo comparator is tripped, the charger will not come out of shutdown until v cc rises 70mv above the battery voltage. trickle charge and defective battery detection at the beginning of a charge cycle, if the battery voltage is low (below 2.48v) 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 charge time, the battery is assumed to be defective, the charge cycle is terminated, the chrg pin output assumes a high impedance state, and the fault pin pulls low. the fault can be cleared by toggling v cc , temporarily forcing the shdn pin to 0v, or temporarily forcing the bat pin voltage above 2.48v. shutdown the ltc4053 can be shut down (i cc = 25 m a) by pulling the shdn pin to 0v. for normal operation, pull the shdn pin above the manual shutdown threshold voltage level. do not leave this pin open. in shutdown the internal linear regulator is turned off, and the internal timer is reset. programming charge current the formula for the battery charge current (see figure 1) is: i chg = (i prog ) ? 1000 = (1.5v / r prog ) ? 1000 or r prog = 1500v/i chg where r prog is the total resistance from the prog pin to ground. under trickle charge conditions, this current is reduced to 10% of the full-scale value. figure 2. combining wall adapter and usb power 4053 f02 1k 3k li-ion battery 5v wall adapter 1a i chg 3k ltc4053 bat v cc 2 9 7 i chg prog + system load usb power 500ma i chg d1 mn1 mp1 .com .com .com .com
ltc4053-4.2 10 4053f programming the timer the programmable timer is used to terminate the charge cycle. the timer duration is programmed by an external capacitor at the timer pin. the total charge time is: time (hours) = (3 hours) ? (c timer /0.1 m f) or c timer = 0.1 m f ? time (hours)/3 (hours) the timer starts when an input voltage greater than the undervoltage lockout threshold level is applied and the shdn pin is greater than the manual shutdown threshold voltage level. after a time-out occurs, the charge current stops, and the chrg output assumes a high impedance state to indicate that the charging has stopped. connect- ing the timer pin to ground disables the timer function. recharge after a charge cycle has terminated, if the battery voltage drops below the recharge threshold of 4.05v a new charge cycle will begin. the recharge circuit integrates the bat pin voltage for a few milliseconds to prevent a transient from restarting the charge cycle. if the battery voltage remains below 2.48v during trickle charge for 1/4 of the programmed time, the battery may be defective and the charge cycle will end. in addition, the recharge comparator is disabled and a new charge cycle will not begin unless the input voltage is toggled off-then- on, the shdn pin is momentarily pulled to ground, or the bat pin is pulled above the 2.48v trickle charge threshold. open-drain status outputs the ltc4053 has three open-drain status outputs: acpr, chrg and fault. the acpr pin pulls low when an input voltage greater than the undervoltage lockout threshold is applied and becomes high impedance when power (v in < v uv ) is removed. chrg and fault work together to indicate the status of the charge cycle. table 1 describes the status of the charge cycle based on the chrg and fault outputs. applicatio s i for atio wu uu table 1. fault chrg description high low charge cycle has started, c/10 has not been reached and charging is proceeding normally. low low charge cycle has started, c/10 has not been reached, but the charge current and timer have been paused due to an ntc out-of- temperature condition. high 30 m a c/10 has been reached and charging is pull-down proceeding normally. low 30 m a c/10 has been reached but the charge current pull-down and timer have paused due to an ntc out-of- temperature condition. high high normal timeout (charging has terminated). low high if fault goes low and chrg goes high impedance simultaneously, then the ltc4053 has timed out due to a bad cell (v bat <2.48v after one-quarter the programmed charge time). if chrg goes high impedance first, then the ltc4053 has timed out normally (charging has terminated), but ntc is indicating an out- of-temperature condition. chrg status output pin when the charge cycle starts, the chrg pin is pulled to ground by an internal n-channel mosfet capable of driving an led. when the charge current drops to 10% of the full-scale current (c/10), the n-channel mosfet is latched off and a weak 30 m a current source to ground is connected to the chrg pin. after a time-out occurs, the pin assumes a high impedance state. by using two different value pull-up resistors a microprocessor can detect three states from this pin (charging, c/10 and time- out). see figure 3. when the ltc4053 is in charge mode, the chrg pin is pulled low by the internal n-channel mosfet. to detect this mode, force the digital output pin, out, high and measure the voltage at the chrg pin. the n-channel mosfet will pull the pin low even with the 2k pull-up resistor. once the charge current drops to 10% of the .com .com .com .com
ltc4053-4.2 11 4053f + + + 4053 f04 r ntc 10k r hot 1% 7/8 v cc 1/2 v cc 3/160 v cc too cold too hot disable ntc ltc4053 v cc ntc thermistors the ltc4053 ntc trip points were designed to work with thermistors whose resistance-temperature characteris- tics follow vishay dales r-t curve 2. the vishay nths0603n02n1002j is an example of such a ther- mistor. however, vishay dale has many thermistor prod- ucts that follow the r-t curve 2 characteristic in a variety of sizes. futhermore, any thermistor whose ratio of r cold to r hot is about 7.0 will also work (vishay dale r-t curve 2 shows a ratio of r cold to r hot of 2.816/0.4086 = 6.9). ntc layout considerations it is important that the ntc thermistor not be in close thermal contact with the ltc4053. because the ltc4053 package can reach temperatures in excess of the 50 c trip point, the ntc function can cause a hysteretic oscillation which turns the charge current on and off according to the package temperature rather than the battery temperature. this problem can be eliminated by thermally coupling the ntc thermistor to the battery and not to the ltc4053. furthermore, it is essential that the v cc connection to r hot is made according to standard kelvin sense tech- niques. since v cc is a high current path into the ltc4053, it is essential to minimize voltage drops between the v cc input pin and the top of r hot . applicatio s i for atio wu uu figure 4 figure 3. microprocessor interface 4053 f03 400k 2k 3 8 ltc4053 in v cc v dd out chrg v + processor full-scale current (c/10), the n-channel mosfet is turned off and a 30 m a current source is connected to the chrg pin. the in pin will then be pulled high by the 2k pull-up. by forcing the out pin to a high impedance state, the current source will pull the pin low through the 400k resistor. when the internal timer has expired, the chrg pin will assume a high impedance state and the 400k resistor will then pull the pin high to indicate that charging has terminated. ntc thermistor 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 4. to use this feature, connect a 10k ntc thermistor between the ntc pin and ground and a resistor (r hot ) from the ntc pin to v cc . r hot should be a 1% resistor with a value equal to the value of the chosen ntc thermistor at 50 c (this value is 4.1k for a vishay nths0603n02n1002j thermistor). the ltc4053 goes into hold mode when the resistance of the ntc thermistor drops below 4.1k which should be approximately 50 c. the hold mode freezes the timer and stops the charge cycle until the thermistor indicates a return to a valid temperature. as the temperature drops, the resistance of the ntc thermistor rises. the ltc4053 is designed to go into hold mode when the value of the ntc thermistor increases to seven times the value of r hot . for a vishay nths0603n02n1002j thermistor, this value is 28.7k which corresponds to approximately 0 c. the hot and cold comparators each have approximately 2 c of hysteresis to prevent oscillation about the trip point. the ntc function can be disabled by grounding the ntc pin. .com .com .com .com
ltc4053-4.2 12 4053f constant-current/constant-voltage/ constant-temperature the ltc4053 uses a unique architecture to charge a battery in a constant-current, constant-voltage, constant- temperature fashion. figure 1 shows a simplified block diagram of the ltc4053. 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, ta, and va are used in three separate feedback loops to force the charger into constant-current, temperature, or voltage mode, respectively. diodes, d1, d2, and d3 provide priority to whichever loop is trying to reduce the charge current the most. the outputs of the other two amplifiers saturate low which effectively re- moves their loops from the system. when in constant- current mode, ca servos the voltage at the prog pin to be precisely 1.50v (or 0.15v when in trickle-charge mode). ta limits the die temperature to approximately 105 c when in constant-temperature mode and the prog pin voltage gives an indication of the charge current as dis- cussed in programming charge current. va servos its inverting input to precisely 2.485v 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. again, the prog pin voltage gives 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 1500v/r prog . if the power dissipation of the ltc4053 results in the junction temperature approaching 105 c, the amplifier (ta) will begin decreasing the charge current to limit the die temperature to approximately 105 c. as the battery voltage rises, the ltc4053 either returns to constant-current mode or it enters constant- voltage mode straight from constant-temperature mode. applicatio s i for atio wu uu ntc trip point errors when a 1% resistor is used for r hot , the major error in the 50 c trip point is determined by the tolerance of the ntc thermistor. a typical 10k ntc thermistor has a 10% tolerance. by looking up the temperature coefficient of the thermistor at 50 c, the tolerance error can be calculated in degrees centigrade. consider the vishay nths0603n02n1002j thermistor which has a temperature coefficient of C3.3%/ c at 50 c. dividing the tolerance by the temperature coefficient, 10%/ (3.3%/ c) = 3 c, gives the temperature error of the hot trip point. the cold trip point is a little more complicated because its 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 50 c varies from 7 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 50 c, r hot . the formula is: temperature error ( c) = 1 7 1 100 + ? ? ? ? tol r r tc cold hot for example, the vishay nths0603n02n1002j thermistor with a tolerance of 10%, tc of C4.5%/ c, and r cold / r hot of 6.89, has a cold trip point error of: temperature error ( c) = 1010 7 6 89 1 100 45 ? ? ? ? . . . = C1.8 c, +2.5 c if a thermistor with a tolerance less than 10% is used, the trip point errors begin to depend on errors other than thermistor tolerance including the input offset voltage of the internal comparators of the ltc4053 and the effects of internal voltage drops due to high charging currents. .com .com .com .com
ltc4053-4.2 13 4053f regardless of mode, the voltage at the prog pin is proportional to the current being delivered to the battery. power dissipation the conditions that cause the ltc4053 to reduce charge current due to the thermal protection feedback can be approximated by considering the power dissipated in the ic. for high charge currents, the ltc4053 power dissipa- tion 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 battery charge current. it is not necessary to perform any worst- case power dissipation scenarios because the ltc4053 will automatically reduce the charge current to maintain the die temperature at approximately 105 c. however, the approximate ambient temperature at which the thermal feedback begins to protect the ic is: t a = 105 c C p d q ja t a = 105 c C (v cc C v bat ) ? i bat ? q ja example: consider an ltc4053 operating from a 5v wall adapter providing 1.2a to a 3.75v li-ion battery. the ambient temperature above which the ltc4053 will begin to reduce the 1.2a charge current is approximately: t a = 105 c C (5v C 3.75v) ? 1.2a ? 40 c/w t a = 105 c C 1.5w ? 40 c/w = 105 c C 60 c = 45 c the ltc4053 can be used above 45 c, but the charge current will be reduced below 1.2a. the approximate charge current at a given ambient temperature can be approximated by: i ct vv bat a cc bat ja = 105 ( ) q consider the above example with an ambient temperature of 55 c. the charge current will be reduced to approxi- mately: i cc vvcw c ca a bat = = = 105 55 5 3 75 40 50 50 1 (. ) / / applicatio s i for atio wu uu 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 ltc4053 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 105 c. board layout considerations the ability to deliver maximum charge current under all conditions require that the exposed metal pad on the backside of the ltc4053 package be soldered to the pc board ground. correctly soldered to a 2500mm 2 double- sided 1oz. copper board the ltc4053 has a thermal resistance of approximately 40 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 40 c/w. as an example, a correctly soldered ltc4053 can deliver over 1250ma 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 hot power source. for more information refer to application note 88. stability the constant-voltage mode feedback loop is stable without any compensation provided that a battery is connected. however, a 1 m f capacitor with a 1 w series resistor to gnd is recommended at the bat pin to keep ripple voltage low when the battery is disconnected. in the constant-current mode it is the prog pin that is in the feedback loop and not the battery. the constant- current mode stability is affected by the impedance at the .com .com .com .com
ltc4053-4.2 14 4053f prog pin. with no additional capacitance on the prog pin, stability is acceptable with program resistor values as high as 50k. however, additional capacitance on this node reduces the maximum allowed program resistor. the pole frequency at the prog pin should be kept above 500khz. therefore, if the prog pin is loaded with a capacitance, c, the following equation should be used to calculate the maximum resistance value for r prog : r prog < 1/(6.283 ? 5 10 5 ? c) 5 7 r prog c filter charge current monitor circuitry 10k ltc4053 4053 f05 gnd prog figure 5. isolating capacitive load on prog pin and filtering applicatio s i for atio wu uu 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 is added between the prog pin and the filter capacitor and monitoring circuit to ensure stability. .com .com .com .com
ltc4053-4.2 15 4053f package descriptio u mse package 10-lead plastic msop (reference ltc dwg # 05-08-1663) msop (mse) 0802 0.53 0.01 (.021 .006) seating plane 0.18 (.007) 1.10 (.043) max 0.17 0.27 (.007 ?.011) typ 0.13 0.076 (.005 .003) 0.86 (.034) ref 0.50 (.0197) bsc 12 3 45 4.90 0.15 (1.93 .006) 0.497 0.076 (.0196 .003) ref 8 9 10 10 1 7 6 3.00 0.102 (.118 .004) (note 3) 3.00 0.102 (.118 .004) note 4 note: 1. dimensions in millimeter/(inch) 2. drawing not to scale 3. dimension does not include mold flash, protrusions or gate burrs. mold flash, protrusions or gate burrs shall not exceed 0.152mm (.006") per side 4. dimension does not include interlead flash or protrusions. interlead flash or protrusions shall not exceed 0.152mm (.006") per side 5. lead coplanarity (bottom of leads after forming) shall be 0.102mm (.004") max 0.254 (.010) 0 ?6 typ detail ? detail ? gauge plane 5.23 (.206) min 3.2 ?3.45 (.126 ?.136) 0.889 0.127 (.035 .005) recommended solder pad layout 0.305 0.038 (.0120 .0015) typ 2.083 0.102 (.082 .004) 2.794 0.102 (.110 .004) 0.50 (.0197) bsc bottom view of exposed pad option 1.83 0.102 (.072 .004) 2.06 0.102 (.081 .004) 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. .com .com .com .com
ltc4053-4.2 16 4053f linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 l fax: (408) 434-0507 l www.linear.com ? linear technology corporation 2001 lt/tp 0403 2k ? printed in usa li-ion battery charger with reverse polarity input protection ltc4053-4.2 bat prog v cc shdn timer gnd ntc 0.1 f 4.7 f 8 2 4 9 7 5 4053 f07 6 i bat = 1a 1-cell li-ion battery 5v wall adapter 1.5k 1% + acpr fault bat prog chrg ntc timer gnd v in = 5v 4k 1% 3k 1% r ntc 10k 4.7 f 1 f 0.1 f i bat = 500ma 4053 f08 1k 1k 1k shdn li-ion cell v cc 82 10 3 9 7 5 4 6 1 1 ltc4053-4.2 full featured single cell li-ion charger usb/wall adapter power li-ion battery charger suspend 0.1 f 15k 4.7 f 1 f 4053 f06 1k li-ion cell usb power 5v wall adapter 100ma/ 500ma c 3.74k ltc4053-4.2 bat shdn v cc timer gnd 2 9 8 7 5 ntc 6 4 i bat prog 1 + typical applicatio s u related parts part number description comments lt1571 200khz/500khz switching battery charger up to 1.5a charge current; preset and adjustable battery voltages ltc1729 lithium-ion battery charger termination controllers time or charge current termination, preconditioning 8-lead msop ltc1730 lithium-ion battery pulse charger no blocking diode required, current limit for maximum safety ltc1731 lithium-ion linear battery charger controller simple charger uses external fet, features preset voltages, c/10 charger detection and programmable timer ltc1732 lithium-ion linear battery charger controller simple charger uses external fet, features preset voltages, c/10 charger detection and programmable timer, input power good indication ltc1733 monolithic lithium-ion linear battery charger standalone charger with programmable timer, up to 1.5a charge current 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 controller 50ma to 180ma, no blocking diode, no sense resistor needed ltc4050 lithium-ion linear battery charger controller simple charger uses external fet, thermistor input for battery temperature sensing ltc4052 lithium-ion linear battery pulse charger fully integrated, standalone pulse charger, minimal heat dissipation, overcurrent protection ltc4054 standalone lithium-ion linear battery charger in up to 800ma charge current, thermal regulation, usb compatible, thinsot charge termination ltc4056 standalone lithium-ion linear battery charger up to 700ma charge current, charge termination, continuous charging with controller in thinsot poorly regulated or high impedance input supplies thinsot is a trademark of linear technology corporation. .com .com .com

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