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aat3682 data sheet li-ion/polymer linear battery charger 1 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201884b ? skyworks proprietary information ? products and product information are subject to change without notice. ? apr il 25, 2012 general description the aat3682 is a lithium-ion/polymer linear battery charger. it is designed for compact portable applications with a single-cell battery. the aat3682 precisely regu- lates battery charge voltage and charge current, and offers an integrated pass device, minimizing the number of external components required. the aat3682 charges the battery in three different phases: preconditioning, constant current, and constant voltage. in preconditioning mode, the charge current has two different levels and is controlled by one external pin. battery charge temperature and charge state are care- fully monitored for fault conditions. a battery charge stable monitor output pin is provided to indicate the bat- tery charge status through a display led or interface to a system controller. the aat3682 has a sleep mode option for when the input supply is removed. in this mode, it draws only 2.0 a of typical current. the aat3682 is available in a pb-free, 16-pin qfn44 package and is specified over the -20c to +70c tem- perature range. features ? v in range: 4.7v to 6.0v ? low quiescent current, typically 0.5ma ? 1% accurate preset voltage ? up to 1a of charging current ? integrated pass device ? battery temperature monitoring ? fast trickle charge option ? deep discharge cell conditioning ? led charge status output or system microcontroller serial interface ? power-on reset ? lower power sleep mode ? status outputs for led or system interface indicates charge and fault conditions ? temperature range: -20c to +70c ? 16-pin qfn44 package applications ? cellular telephones ? digital still cameras ? hand-held pcs ? mp3 players ? personal data assistants (pdas) typical application vp gate drv csi vcc vss bat t2x bsense ts stat r sense c in = 10 f c out = 1 f led 1 r 2 = 1k batt+ batt- r t1 vp r t2 temp a dapter r 4 r 3
aat3682 data sheet li-ion/polymer linear battery charger 2 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201884b ? skyworks proprietary information ? products and product information are subject to change without notice. ? apr il 25, 2012 pin descriptions pin # symbol function 1 ts battery temperature sense input. 2, 3, 8, 12 n/c not connected. 4 stat battery charger status output. connect an led in series with 2.2k ? from stat to v in for a visual monitor battery charge state or connect to a microcontroller to monitor battery status. a 100k ? resistor should be placed between stat and v in for this function. 5 vss common ground connection. 6 drv battery charge control output. 7 t2x battery trickle charge control input. connect this pin to v ss to double the battery trickle charge cur- rent. leave this pin oating for normal trickle current (10% of full charge current). to enter micro- controller fast-read status, pull this pin high during power up. 9bat battery charge control output. current regulated output to charge the battery. for best operation, a 0.1 f ceramic capacitor should be placed between bat and gnd. 10 vss common ground connection. 11 gate input voltage for biasing the pass device. 13 vp battery charge power input. 14 csi current sense input. 15 bsense battery voltage sense input. 16 vcc aat3682 bias input power. ep exposed paddle (bottom); connect to gnd directly beneath the package. pin configuration qfn44-16 (top view) 1 2 3 4 12 11 10 9 5 6 7 8 16 15 14 13 ts n/c n/c stat vss dr v t2x n/c bat vss gate n/c aat3682 vp csi bsense vcc
aat3682 data sheet li-ion/polymer linear battery charger 3 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201884b ? skyworks proprietary information ? products and product information are subject to change without notice. ? apr il 25, 2012 1. stresses above those listed in absolute maximum ratings may cause permanent damage to the device. functional operation at c onditions other than the operating conditions specified is not implied. only one absolute maximum rating should be applied at any one tim e. 2. mounted on an fr4 board. 3. derate 20mw/c above 25c. absolute maximum ratings 1 symbol description value units v in v in relative to gnd -0.3 to 6.0 v v csi csi to gnd -0.3 to v cc + 0.3 v t2x t2x to gnd -0.3 to 5.5 bias, v bat bat to gnd -0.3 to v cc + 0.3 t j operating junction temperature range -40 to 85 c thermal information symbol description value units ? ja maximum thermal resistance 2, 3 50 c/w p d power dissipation (t a = 25c) 2.0 w
aat3682 data sheet li-ion/polymer linear battery charger 4 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201884b ? skyworks proprietary information ? products and product information are subject to change without notice. ? apr il 25, 2012 1. the aat3682 output charge voltage is specified over the 0c to 55c ambient temperature range; operation over -20c to 70c is guaranteed by design. 2. 1a of charging current is only for dynamic applications and not dc. in addition, the ambient temperature must be at or below 50c. electrical characteristics 1 v in = 5.0v, t a = -20c to +70c, unless otherwise noted. typical values are at t a = 25c. symbol description conditions min typ max units v in operation input voltage 4.7 6.0 v i cc operating current v in = 5.5v, v ch = 4.2 0.5 3.0 ma i sleep sleep mode current v in = 3.5v, v ch = 4.2 3.0 6.0 a i stat(hi) stat high level output leakage current v in = 5.5v -1.0 +1.0 a v stat(low) stat low level sink current v in = 5.5v, i sink = 5ma 0.3 0.6 v v ch output charge voltage regulation v bat = 4.2v t a = 25c 4.175 4.20 4.225 v see note 1 4.158 4.20 4.242 v cs charge current regulation v in = 5.5v, v ch = 4.2 90 100 110 mv i ch charge current 2 v in = 5.5v 1.0 a v min preconditioning voltage threshold v ch = 4.2v 3.04 3.1 3.16 v v trickle trickle charge current regulation t2x floating; v ch = 4.2v 10 mv t 2x trickle charge current gain t2x = v ss 1.8 v ts1 low temperature threshold 29.1 30 30.9 %v cc v ts2 high temperature threshold 58.2 60 61.8 %v cc v term charge termination threshold voltage 4 12 24 mv v rch battery recharge voltage threshold v ch = 4.2v 4.018 4.1 4.182 v v uvlo under-voltage lockout v in rising, t a = 25c 3.5 4.0 4.5 v v ovp over-voltage protection threshold 4.4 v v ocp over-current protection threshold 200 %v cs
aat3682 data sheet li-ion/polymer linear battery charger 5 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201884b ? skyworks proprietary information ? products and product information are subject to change without notice. ? apr il 25, 2012 typical characteristics battery recharge threshold voltage vs.temperature (r sense = 0.15 ) temperature (c) battery recharge threshold voltage (v) 3.80 3.85 3.90 3.95 4.00 4.05 4.10 4.15 4.20 -50 - 25 0 25 50 75 100 regulated output voltage vs. charge current (r sense = 0.15 ) ) charging current (ma) regulated output voltage (v) 4.15 4.17 4.19 4.21 4.23 4.25 0 100 200 300 400 500 600 700 regulated output voltage vs. input voltage (r sense = 0.15) input voltage (v) regulated output voltage (v) 4.00 4.10 4.20 4.30 4.40 4.0 4.5 5.0 5.5 6.0 6.5 regulated output voltage vs. temperature (r sense = 0.15) temperature (c) regulated output voltage (v) 4.100 4.125 4.150 4.175 4.200 4.225 4.250 -50 -25 0 25 50 75 100 trickle charge threshold voltage vs.temperature (r sense = 0.15) temperature (c) trickle charge threshold voltage (v) 2.8 2.9 3.0 3.1 3.2 3.3 3.4 -50 -25 0 25 50 75 100 trickle charge current vs. temperature (r sense = 0.15) temperature (c) trickle charge current (ma) 130 135 140 145 150 155 160 165 170 -50 -25 0 25 50 75 100
aat3682 data sheet li-ion/polymer linear battery charger 6 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201884b ? skyworks proprietary information ? products and product information are subject to change without notice. ? apr il 25, 2012 typical characteristics charging current vs. temperature (r sense = 0.15) temperature (c) charging current (ma) 650 660 670 680 690 700 -50 -25 0 25 50 75 100 charging current vs. input voltage (r sense = 0.15 with external schottky) input voltage (v) charging current (ma) 0 100 200 300 400 500 600 700 4.0 4.5 5.0 5.5 6.0 v bat = 4.1v v bat = 3.6v charging current vs. battery voltage (r sense = 0.15 with external schottky) battery voltage (v) charging current (ma) 0 100 200 300 400 500 600 700 2.5 3.0 3.5 4.0 4.5 5.0 v in = 4.5v v in = 4.75v v in = 5.5v trickle charge current vs. input voltage (r sense = 0.15; 1.8x mode) input voltage (v) trickle charge current (ma) 130 135 140 145 150 155 160 165 170 4.0 4.5 5.0 5.5 6.0 charging current vs. input voltage (r sense = 0.2 with external schottky) input voltage (v) charging current (ma) 0 100 200 300 400 500 600 4.0 4.5 5.0 5.5 6.0 v bat = 4.0v v bat = 3.6v trickle charge current vs. input voltage (r sense = 0.2; 1.8x mode) input voltage (v) trickle charge current (ma) 94 96 98 100 102 104 4 4.5 5 5.5 6
aat3682 data sheet li-ion/polymer linear battery charger 7 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201884b ? skyworks proprietary information ? products and product information are subject to change without notice. ? apr il 25, 2012 typical characteristics charging current vs. battery voltage (r sense = 0.2 with external schottky) battery voltage (v) charging current (ma) 0 100 200 300 400 500 600 2.5 3.0 3.5 4.0 4.5 5.0 v in = 4.5v v in = 4.75v v in = 5.5v safe operating area (t j(max) = 120c) charging current (a) maximum input voltage (v) 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 0.0 0.2 0.4 0.6 0.8 t amb = 85c schottky v f = 0.2v t amb = 70c t amb = 50c t amb = 40c safe operating area (t j(max) = 150c) charging current (a) maximum input voltage (v) 5.0 5.2 5.4 5.6 5.8 6.0 6.2 0 0.2 0.4 0.6 0.8 t amb = 85c t amb = 70c t amb = <50c schottky v f = 0.2v
aat3682 data sheet li-ion/polymer linear battery charger 8 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201884b ? skyworks proprietary information ? products and product information are subject to change without notice. ? apr il 25, 2012 functional description the aat3682 is a linear charger designed for single-cell lithium-ion/polymer batteries. it is a full-featured bat- tery management system ic with multiple levels of power savings, system communication, and protection integrated inside. refer to the block diagram above and the flow chart and typical charge profile graph (figures 1 and 2) in this section. cell preconditioning before the start of charging, the aat3682 checks sev- eral conditions in order to maintain a safe charging envi- ronment. the input supply must be above the minimum operating voltage, or under-voltage lockout threshold (v uvlo ), for the charging sequence to begin. also, the cell temperature, as reported by a thermistor connected to the ts pin, must be within the proper window for safe charging. functional block diagram mux t2x led signal generator microcontroller status generator microcontroller read enable charge status logic control power-on reset vss stat drv gate bat under-voltage lock out over-current / short-circuit protection 2x trickle charge control loop select mux driver v ref temperature sense comparator voltage comparator voltage loop error amp current loop error amp vp vcc bsense t2x ts csi
aat3682 data sheet li-ion/polymer linear battery charger 9 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201884b ? skyworks proprietary information ? products and product information are subject to change without notice. ? apr il 25, 2012 uvlo temperature test ts > v ts1 ts < v ts2 power on reset power on reset preconditioning test current phase test v ch >v bat v min >v bat v term r sense v uvlo shut down mode shut down mode yes no yes yes low current conditioning charge low current conditioning charge (trickle charge) temperature fault temperature fault no no current charging mode current charging mode yes voltage charging mode voltage charging mode < i bat no yes no charge complete latch off charge complete latch off figure 1: aat3682 operational flow chart.
aat3682 data sheet li-ion/polymer linear battery charger 10 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201884b ? skyworks proprietary information ? products and product information are subject to change without notice. ? apr il 25, 2012 preconditioning (trickle charge) phase constant current phase constant voltage phase output charge voltage (v ch ) preconditioning voltage threshold (v min ) regulation current (i charge(reg) ) trickle charge and termination threshold figure 2: typical charge profile. when these conditions have been met and a battery is connected to the bat pin, the aat3682 checks the state of the battery. if the cell voltage is below v min , the aat3682 begins preconditioning the cell. this is per- formed by charging the cell with 10% of the programmed constant current amount. for example, if the programmed charge current is 500ma, then the preconditioning mode (trickle charge) current will be 50ma. cell preconditioning is a safety precaution for deeply discharged cells and, furthermore, limits power dissipation in the pass transis- tor when the voltage across the device is largest. the aat3682 features an optional t2x mode, which allows faster trickle charging at approximately two times the default rate. this mode is selected by connecting the t2x pin to v ss . if an over-temperature fault is triggered, the fast trickle charge will be latched off, and the aat3682 will continue at the default 10% charge current. constant current charging the cell preconditioning continues until the voltage on the bat pin reaches v min . at this point, the aat3682 begins constant current charging (fast charging). current level for this mode is programmed using a current sense resistor r sense between the vcc and csi pins. the csi pin monitors the voltage across r sense to provide feed- back for the current control loop. the aat3682 remains in constant current charge mode until the battery reach- es the voltage regulation point, v ch . constant voltage charging when the battery voltage reaches v ch during constant current mode, the aat3682 transitions to constant volt- age mode. the regulation voltage is factory programmed to 4.2v. in constant voltage operation, the aat3682 monitors the cell voltage and terminates the charging cycle when the voltage across r sense decreases to approximately 10mv. charge cycle termination, recharge sequence after the charge cycle is complete, the aat3682 shuts off the pass device and automatically enters power- saving sleep mode. either of two possible conditions will bring the ic out of sleep mode: the battery voltage at the bat pin drops below v rch (recharge threshold volt- age) or the aat3682 is reset by cycling the input supply through the power-on sequence. falling below v rch sig- nals the ic that it is time to initiate a new charge cycle. sleep mode when the input supply is disconnected, the device auto- matically enters power-saving sleep mode. only con- suming an ultra-low 2 a current, the aat3682 minimizes battery drain when it is not charging. this feature is particularly useful in applications where the input supply level may fall below the battery charge or under-voltage lockout level. in such cases, where the aat3682 input voltage drops, the device will enter the sleep mode and automatically resume charging once the input supply has recovered from its fault condition. this makes the aat3682 well suited for usb battery charger applica- tions. charge inhibit the aat3682 charging cycle is fully automatic; however, it is possible to stop the device from charging even when all conditions are met for proper charging. switching the ts pin to either v in or gnd will force the aat3682 to turn off the pass device and wait for a voltage between the low and high temperature voltage thresholds.
aat3682 data sheet li-ion/polymer linear battery charger 11 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201884b ? skyworks proprietary information ? products and product information are subject to change without notice. ? apr il 25, 2012 sleep / charge complete temp., oc, ov fault battery conditioning constant current mode constant voltage mode off / off / off / off on / on / off / off on / on / on / on on / off / off / off on / on / on / off charge status output status led display on/off on off on off on off on off on off on/off on/off on/off figure 3: led display output. resuming charge and the v rch threshold the aat3682 will automatically resume charging under most conditions when a battery charge cycle is inter- rupted. events such as an input supply interruption or under voltage, removal and replacement of the battery under charge, or charging a partially drained battery are all possible. the aat3682 will monitor the battery volt- age and automatically resume charging in the appropri- ate mode based upon the measured battery cell voltage. this feature is useful for systems with an unstable input supply, which could be the case when powering a char- ger from a usb bus supply. it is also beneficial for charg- ing or ?topping off? partially discharged batteries. the only restriction on resuming charge of a battery is that the battery cell voltage must be below the battery recharge voltage threshold (v rch ) specification. there is v rch threshold hysteresis built into the charge control system. this is done to prevent the charger from errone- ously turning on and off once a battery charge cycle is complete. for example, the aat3682 has a typical v rch threshold of 4.1v. a battery under charge is above 4.1v, but is still in the constant voltage mode because it has not yet reached 4.2v to complete the charge cycle. if the battery is removed and then placed back on the charger, the charge cycle will not resume until the battery voltage drops below the v rch threshold. in another case, a bat- tery under charge is in the constant current mode and the cell voltage is 3.7v when the input supply is inadver- tently removed and then restored. the battery is below the v rch threshold and the charge cycle will immediately resume where it left off. led display charge status output the aat3682 provides a battery charge status output via the stat pin. stat is an open-drain serial data output capable of displaying five distinct status functions with one led connected between the stat pin and vp. there are four periods which determine a status word. under default conditions, each output period is one second long; thus one status word will take four seconds to dis- play through an led. the five modes include: 1. sleep/charge complete: the ic goes into sleep mode when no battery is present -or- when the charge cycle is complete. 2. fault: when an over-current (oc) condition is detected by the current sense and control circuit -or- when an over-voltage (ov) condition is detect- ed at the bat pin -or- when a battery over-temper- ature fault is detected on the temp pin. 3. battery conditioning: when the charge system is in 1x or 2x trickle charge mode. 4. constant current (cc) mode: when the system is in constant current charge mode. 5. constant voltage (cv) mode: when the system is in constant voltage charge mode. an additional feature of the led status display is for a battery not detected state. when the aat3682 senses there is no battery connected to the bat pin, the stat output will turn the led on and off at a rate dependent on the size of the output capacitor being used. the led cycles on for two periods then remains off for two peri- ods. see figure 3 below.
aat3682 data sheet li-ion/polymer linear battery charger 12 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201884b ? skyworks proprietary information ? products and product information are subject to change without notice. ? apr il 25, 2012 sleep / charge complete temp., oc, ov fault battery conditioning constant current mode constant voltage mode hi / hi / hi / hi lo / lo / hi / hi lo / lo / lo / lo lo / hi / hi / hi lo / lo / lo / hi charge status output status stat level figure 4: microcontroller interface logic output. high-speed data reporting an optional system microcontroller interface can be enabled by pulling the t2x pin up to 4.5v to 5.5v during the power-up sequence. the t2x pin should be pulled high with the use of a 100k ? resistor. if the input supply to v in will not exceed 5.5v, then the t2x pin may be tied directly to v in through a 100k ? resistor. since this is a ttl level circuit, it may not be pulled higher than 5.5v without risk of damage to the device. when the high-speed data report feature is enabled, the stat output periods are sped up to 40 s, making the total status word 160 s in length. see figure 4 below. an additional feature is the output status for the battery not detected state. when the aat3682 senses there is no battery connected to the bat pin, the stat pin cycles for two periods, then remains off for two periods. when in high-speed data reporting, the aat3682 will only trickle charge at the 2x trickle charge level. this is because the t2x pin is pulled high to enable the high- speed data reporting. a status display led may not be connected to the stat pin when the high-speed data reporting is being utilized. if both display modes are required, the display led must be switched out of the circuit before the t2x pin is pulled high. failing to do so could cause problems with the high-speed switching con- trol circuits internal to the aat3682. charge complete led status mode a simplified led status can be obtained by configuring the aat3682 for high-speed data reporting mode (t2x tied to vcc) and installing a 0.047 f capacitor from the stat pin to the vss pin (see figure 5). in this configura- tion, the led will be illuminated for all modes except the sleep/charge complete mode. in addition, the t2x input must be tied to vcc through a 100k ? resistor. in this mode, the trickle charge current will be 1.8x the normal trickle charge level. to reset the trickle charge current to the 1x level, the ts input must be temporarily toggled low. removing c3 forces the led status to gradually dim as the battery becomes fully charged (see figure 5). protection circuitry the aat3682 is a highly integrated battery management system ic including several protection features. in addi- tion to battery temperature monitoring, the ic constant- ly monitors for over-current and over-voltage conditions; if an over-current situation occurs, the aat3682 latches off the pass device to prevent damage to the battery or the system, and enters shutdown mode until the over- current event is terminated. an over-voltage condition is defined as a condition where the voltage on the bat pin exceeds the maximum battery charge voltage. if an over- voltage condition occurs, the ic turns off the pass device until voltage on the bat pin drops below the maximum battery charge constant voltage threshold. the aat3682 will resume normal operation after the over-current or over-voltage condition is removed. during an over-cur- rent or over-voltage event, the stat will report a fault signal. in the event of a battery over-temperature condi- tion, the ic will turn off the pass device and report a fault signal on the stat pin. after the system recovers from a temperature fault, the ic will resume operation in the 1x trickle charge mode to prevent damage to the system in the event a defective battery is placed under charge. once the battery voltage rises above the trickle charge to constant current charge threshold, the ic will resume the constant current mode.
aat3682 data sheet li-ion/polymer linear battery charger 13 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201884b ? skyworks proprietary information ? products and product information are subject to change without notice. ? apr il 25, 2012 1 2 j1 1 2 3 j2 1k r4 0.2 r2 1k r3 2.2k r1 100k r6 100k r5 d2 22f c1 10f c2 green led v in gnd d1 47nf c3 ts 1 n/c 2 n/c 3 stat 4 vss 5 drv 6 t2x 7 n/c 8 bat 9 vss 10 gate 11 n/c 12 vp 13 csi 14 bsense 15 vcc 16 aat3682 u1 100k r7 2 1 3 sw-t2x s1 1000pf c4 4.7f c5 remove capacitor for progressive dimming figure 5: evaluation board schematic. applications information choosing a sense resistor the charging rate recommended by lithium-ion/polymer cell vendors is normally 1c, with a 2c absolute maximum rating. charging at the highest recommended rate offers the advantage of shortened charging time without decreasing the battery?s lifespan. this means that the suggested fast charge rate for a 500mah battery pack is 500ma. refer to the safe operating area curves in the typical characteristics section of this datasheet to deter- mine the maximum allowable charge current for a given input voltage. the current sense resistor, r sense , programs the charge current according to the following equation: v cc - v csi r sense = i charge where i charge is the desired typical charge current during constant current charge mode. v cc - v csi is the voltage across r sense , shown in the electrical characteristics table as v cs . to program a nominal 500ma charge cur- rent during fast charge, a 200m ? value resistor should be selected. calculate the worst case power dissipated in the sense resistor according to the following equation: v cs 2 0.1v 2 p = = = 50mw r sense 0.2 a 500mw lrc type sense resistor from irc is adequate for this purpose. higher value sense resistors can be used, decreasing the power dissipated in the sense resis- tor and pass transistor. the drawback of higher value sense resistors is that the charge cycle time is increased, so tradeoffs should be considered when optimizing the design. thermistor the aat3682 checks battery temperature before starting the charge cycle, as well as during all stages of charging. this is accomplished by monitoring the voltage at the ts pin. either a negative temperature coefficient thermistor (ntc) or positive-temperature coefficient thermistor (ptc) can be used because the aat3682 checks to see
aat3682 data sheet li-ion/polymer linear battery charger 14 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201884b ? skyworks proprietary information ? products and product information are subject to change without notice. ? apr il 25, 2012 that the voltage at ts is within a voltage window bound- ed by v ts1 and v ts2 . please see the following equations for specifying resistors: r t1 and r t2 for use with ntc thermistor: r t1 = 5 ? r th ? r tc 3 (r tc - r th ) r t2 = 5 ? r th ? r tc (2 ? r tc ) - (7 ? r th ) r t1 and r t2 for use with ptc thermistor: r t1 = 5 ? r th ? r tc 3 (r th - r tc ) r t2 = 5 ? r th ? r tc (2 ? r th ) - (7 ? r tc ) where r tc is the thermistor?s cold temperature resis- tance and r th is the thermistor?s hot temperature resis- tance. see thermistor specifications for additional infor- mation. to ensure there is no dependence on the input supply changes, connect divider between vcc and vss. disabling the temperature-monitoring function is achieved by applying a voltage between v ts1 and v ts2 on the ts pin. capacitor selection input capacitor in general, it is good design practice to place a decou- pling capacitor between the vcc and vss pins. an input capacitor in the range of 1 f to 10 f is recommended. if the source supply is unregulated, it may be necessary to increase the capacitance to keep the input voltage above the under-voltage lockout threshold. if the aat3682 is to be used in a system with an external power supply source, such as a typical ac-to-dc wall adapter, then a c in capacitor in the range of 10 f should be used. a larger input capacitor in this application will minimize switching or power bounce effects when the power supply is ?hot plugged? in. output capacitor the aat3682 does not need an output capacitor for sta- bility of the device itself. however, a capacitor connected between bat and vss will control the output voltage when the aat3682 is powered up when no battery is connected. the aat3682 can become unstable if a high impedance load is placed across the bat pin to vss. such a case is possible with aging li-ion/poly battery cells. as cells age through repeated charge and dis- charge cycles, the internal impedance can rise over time. a 10 f or larger output capacitor will compensate for the adverse effects of a high impedance load and assure device stability over all operating conditions. power dissipation the voltage drop across the vp and bat pins multiplied times the charge current is used to determine the inter- nal power dissipation. the maximum power dissipation occurs when the input voltage is at a maximum and the battery voltage is at the minimum preconditioning volt- age threshold. this power is then multiplied times the package theta to determine the maximum junction tem- perature. the worst case power junction temperature is calculated as follows: p max = (v in(max) - v sense - v schottky - v bat(min) ) ? i chg(max) = (5.5v - 0.1v - 0.2v - 3.04v) ? 550ma = 1.2w this equation can be used to determine the maximum input voltage given the maximum junction and ambient temperature and desired charge current. t j(max) - t amb v in(max) = + v bat + v schottky + v cs = + 3.1v + 0.2v + 0.1v = 5.3v ? i chg(max) 120 c - 70 c 50 c/w ? 500ma operation under no-load under no-load conditions (i.e., when the aat3682 is powered with no battery connected between the bat pin and vss), the output capacitor is charged up very quick- ly by the trickle charge control circuit to the bat pin until the output reaches the recharge threshold (v rch ). at this point, the aat3682 will drop into sleep mode. the output capacitor will discharge slowly by the capacitor?s own internal leakage until the voltage seen at the bat pin drops below the v rch threshold. this 100mv cycle will
aat3682 data sheet li-ion/polymer linear battery charger 15 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201884b ? skyworks proprietary information ? products and product information are subject to change without notice. ? apr il 25, 2012 continue at approximately 3hz with a 0.1 f capacitor connected. a larger capacitor value will produce a slower voltage cycle. this operation mode can be observed by viewing the stat led blinking on and off at the rate established by the c out value. for desktop charger appli- cations, where it might not be desirable to have a ?char- ger ready? blinking led, a large c out capacitor in the range of 100 f or more would prevent the operation of this mode. the aat3682 features a charge status output. connecting a led to the stat pin will display all the three conditions of battery operation. once the adapter is connected to the battery charger, the led will be fully illuminated. as the battery charges, the led will gradually dim as it transitions to constant current mode and to constant voltage mode. table 1 summarizes the conditions. charge status led display no battery connected blinking battery condition 100% led light constant current 75% led light constant voltage 25% led light sleep/charge complete off table 1: charging status. for applications where gradual dimming of the led is not desired, adding c3 (refer to figure 5) between the stat pin and vss will alter the charging status. in addition, the aat3682 must be configured to operate in the high frequency stat mode by connecting the t2x pin to vcc via 100k ? resistor. as the battery is transitioning from trickle charge to con- stant current charge and constant voltage, the led will remain illuminated. once the battery is fully charged, the led will shut off, indicating completion of charge. table 2 summarizes the conditions. charge status led display no battery connected blinking battery condition on constant current on constant voltage on sleep/charge complete off table 2: charging status with c3 connected. reverse current blocking diode a reverse blocking diode is generally required for the circuit shown in figure 5. the blocking diode gives the system protection from a shorted input. if there is no other protection in the system, a shorted input could discharge the battery through the body diode of the internal pass mosfet. if a reverse blocking diode is added to the system, a device should be chosen that can withstand the maximum constant current charge current at the maximum system ambient temperature. additionally, the blocking diode will prevent the battery from being discharged to the uvlo level by the aat3682 in the event that power is removed from the input to the aat3682. for this reason, the blocking diode must be placed in the location shown in figure 5. diode selection typically, a schottky diode is used in reverse current blocking applications with the aat3682. other lower cost rectifier type diodes may also be used if sufficient input power supply headroom is available. the blocking diode selection should based on merits of the device forward voltage (v f ), current rating, input supply level versus the maximum battery charge volt- age, and cost. first, one must determine the appropriate minimum diode forward voltage drop: v in(min) = v bat(max) + v f(tran) + v f(diode) where: v in(min) = minimum input supply level v bat(max) = maximum battery charge voltage required v f(tran) = pass transistor forward voltage drop v f(diode) = blocking diode forward voltage based on the maximum constant current charge level set for the system, the next step is to determine the mini- mum current rating and power handling capacity for the blocking diode. the constant current charge level itself will dictate what the minimum current rating must be for a given blocking diode. the minimum power handling capacity must be calculated based on the constant cur- rent amplitude and the diode forward voltage (v f ): v f p d(min) = i cc where: p d(min) = minimum power rating for a diode selection
aat3682 data sheet li-ion/polymer linear battery charger 16 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201884b ? skyworks proprietary information ? products and product information are subject to change without notice. ? apr il 25, 2012 figure 6: evaluation board top side layout. figure 7: evaluation board bottom side layout. v f = diode forward voltage i cc = constant current charge level for the system schottky diodes schottky diodes are selected for this application because they have a low forward voltage drop, typically between 0.3v and 0.4v. a lower v f permits a lower voltage drop at the constant current charge level set by the system; less power will be dissipated in this element of the cir- cuit. a schottky diode allows for lower power dissipation, smaller component package sizes, and greater circuit layout densities. rectifier diodes any general purpose rectifier diode can be used with the aat3682 application circuit in place of a higher cost schottky diode. the design trade-off is that a rectifier diode has a high forward voltage drop. v f for a typical silicon rectifier diode is in the range of 0.7v. a higher v f will place an input supply voltage requirement for the battery charger system. this will also require a higher power rated diode since the voltage drop at the constant current charge amplitude will be greater. refer to the previously stated equations to calculate the minimum v in and diode p d for a given application.
aat3682 data sheet li-ion/polymer linear battery charger 17 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201884b ? skyworks proprietary information ? products and product information are subject to change without notice. ? apr il 25, 2012 reference symbol description footprint part number manufacturer u1 battery charger aat3682 qfn44-16 aat3682-4.2 skyworks c1 ceramic capacitor 20 f-10v-x5r 1210 grm32er61a226ka65l murata c2 ceramic capacitor 10 f-10v-x5r 0805 grm21br61a106ke19l c3 ceramic capacitor 0.047 f-10v-x7r 0805 vj0805y473kxqa vishay r1 resistor 2.2k ? 1/4w 0402 crcw04022211f r2 current sensing resistor 0.2 ? 1/4w 0805 rl1220s-r20-f ssm susumu r3 resistor 1.0k ? 1% 1/4w 0402 crcw04021003f vishay r4 resistor 1.0k ? 1% 1/4w 0402 crcw04021001f r5 resistor 100k ? 1% 1/4w 0402 crcw04021003f r6 resistor 100k ? 1% 1/4w 0402 crcw04021003f r7 resistor 100k ? 1% 1/4w 0402 crcw04021003f j1 4-pin socket connector 4 pin 277-1273-nd j2 6-pin socket connector 6 pin 277-1274-nd s1 jumper stand switch 2mm jumper S2105-40-ND d1 green led 1206 l62215ct-nd chicago miniature d2 3.0a schottky diode sma b340laditr-nd diodes incorporated
aat3682 data sheet li-ion/polymer linear battery charger 18 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201884a ? skyworks proprietary information ? products and product information are subject to change without notice. ? apr il 17, 2012 copyright ? 2012 skyworks solutions, inc. all rights reserved. information in this document is provided in connection with skyworks solutions, inc. (?skyworks?) products or services. these m aterials, including the information contained herein, are provided by skyworks as a service to its customers and may be used for informational purposes only by the customer. skyworks assumes no responsibility fo r errors or omissions in these materials or the information contained herein. sky- works may change its documentation, products, services, speci cations or product descriptions at any time, without notice. skyworks makes no commitment to update the materials or informati on and shall have no responsibility whatsoever for con icts, incompatibilities, or other dif culties arising from any future changes. no license, whether express, implied, by estoppel or otherwise, is granted to any intellectual property rights by this document . skyworks assumes no liability for any materials, products or information provided here- under, including the sale, distribution, reproduction or use of skyworks products, information or materials, except as may be p rovided in skyworks terms and conditions of sale. the materials, products and information are provided ?as is? without warranty of any kind, whether express, implied, statutory, or otherwise, including fitness for a particular purpose or use, merchantability, performance, quality or non-infringement of any intellectual property right; all such warranti es are hereby expressly disclaimed. skyworks does not warrant the accuracy or completeness of the information, text, graphics or other items contained within these materials. sk yworks shall not be liable for any damages, in- cluding but not limited to any special, indirect, incidental, statutory, or consequential damages, including without limitation , lost revenues or lost profits that may result from the use of the materials or information, whether or not the recipient of materials has been advised of the possibility of such damage. skyworks products are not intended for use in medical, lifesaving or life-sustaining applications, or other equipment in which the failure of the skyworks products could lead to personal injury, death, physical or en- vironmental damage. skyworks customers using or selling skyworks products for use in such applications do so at their own risk and agree to fully indemnify skyworks for any damages resulting from such improper use or sale. customers are responsible for their products and applications using skyworks products, which may deviate from published speci cations as a result of design defects, errors, or operation of products outside of pub- lished parameters or design speci cations. customers should include design and operating safeguards to minimize these and other risks. skyworks assumes no liabi lity for applications assistance, customer product design, or damage to any equipment resulting from the use of skyworks products outside of stated published speci cations or parameters. skyworks, the skyworks symbol, and ?breakthrough simplicity? are trademarks or registered trademarks of skyworks solutions, inc ., in the united states and other countries. third-party brands and names are for identi cation purposes only, and are the property of their respective owners. additional information, including relevant terms and co nditions, posted at www.skyworksinc.com, are incorporated by reference. 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold . 3. the leadless package family, which includes qfn, tqfn, dfn, tdfn and stdfn, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing process. a solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder c onnection. ordering information output voltage package marking 1 part number (tape and reel) 2 4.2v qfn44-16 mgxxy aat3682isn-4.2-t1 skyworks green? products are compliant with all applicable legislation and are halogen-free. for additional information, refer to skyworks de?ition of green , document number sq04-0074. package information 3 4.000 all dimensions in millimeters.

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