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general description the aat3687 batterymanager is a highly integrat- ed single-cell lithium-ion/polymer battery charger ic designed to operate with ac adapter inputs. it requires a minimum number of external compo- nents. the aat3687 precisely regulates battery charge voltage and current for 4.2v lithium- ion/polymer battery cells. adapter charge current rates can be programmed up to 1.5a. an active thermal management system regulates the fast charge constant current for all ambient tempera- ture and input vs. output voltage conditions. battery temperature and charge state are fully monitored for fault conditions. in the event of an over-voltage or over-temperature failure, the device will automatically shut down, thus protecting the charging device, control system, and the bat- tery under charge. status monitor output pins are provided to indicate the battery charge status by directly driving two external leds. a serial interface output is available to report 12 various charging status states to a microcontroller. the aat3687 is available in a pb-free, thermally- enhanced, space-saving 12-pin tdfn 3x3mm package and is rated over the -40c to +85c tem- perature range. features ? input voltage range: 4.0v to 5.5v ? up to 1.5a charging current ? adapter present indicator (adpp#) ? high level of integration with internal: ? charging device ? reverse blocking diode ? current sensing ? active thermal loop charge reduction ? automatic recharge sequencing ? battery temperature monitoring ? full battery charge auto turn-off / sleep mode ? over-voltage, over-temperature, and emergency thermal protection ? power on reset and soft start ? serial interface status report ? 12-pin 3x3mm tdfn package ? -40c to +85c temperature range applications ? cellular telephones ? digital still cameras ? hand held pcs ? mp3 players ? personal data assistants (pdas) ? other lithium-ion/polymer battery-powered devices aat3687 lithium-ion/polymer battery charger typical application 3687.2006.10.1.7 1 batterymanager ? aat3687 c out 10 f batt- temp battery pack adp adpset ct gnd ts bat batt+ r set r b1 r b2 c in 10 f c t 0.1 f a dapter stat1 led1 led2 stat2 data serial interface en enable adpp# adapter present +
pin descriptions pin configuration tdfn33-12 (top view) pin # name type function 1 bat out battery charging and sensing. 2 adp in adapter input. 3 gnd ground ground connection. 4 en in aat3687: enable pin. logic high enables the ic. aat3687-1, aat3687-2: enable pin. logic high enables the ic. en tied to internal 4m pull-up resistor to adp. 5 adpp# out adapter present indicator. this pin is open drain until adp pin reaches threshold. 6 ts in/out connect to 10k ntc thermistor. 7 data out status report to microcontroller via serial interface: open drain. 8 stat2 out battery charge status indicator pin to drive an led: active low, open drain. 9 stat1 out battery charge status indicator pin to drive an led: active low, open drain. 10 ct in/out timing capacitor to adjust internal watchdog timer. set maximum charge time for adapter powered trickle, cc, and cv charge modes. if timing function is not needed, terminate this pin to ground. 11 n/c no connection. 12 adpset in/out use resistor at this pin to set adapter charging current. ep exposed paddle (bottom); connect to gnd directly beneath package. aat3687 lithium-ion/polymer battery charger 2 3687.2006.10.1.7 bat adp gnd 1 en a dpp# ts adpse t n/c ct stat1 stat2 data 2 3 4 5 6 12 11 10 9 8 7
aat3687 feature options absolute maximum ratings 1 thermal information symbol description value units ja maximum thermal resistance 2 50 c/w p d maximum power dissipation 2.0 w symbol description value units v p adp input voltage, <30ms, duty cycle <10% -0.3 to 7.0 v v p adp input voltage, continuous -0.3 to 6.0 v v n bat, ts, adpset, adpp#, data, ct, en, stat1, stat2 -0.3 to v p + 0.3 v t j operating junction temperature range -40 to 150 c t lead maximum soldering temperature (at leads) 300 c internal pull-up can leave product trickle charge resistor on en pin ts pin open aat3687 yes no no aat3687-1 yes yes yes aat3687-2 no yes yes aat3687 lithium-ion/polymer battery charger 3687.2006.10.1.7 3 1. stresses above those listed in absolute maximum ratings may cause permanent damage to the device. functional operation at c ondi- tions other than the operating conditions specified is not implied. only one absolute maximum rating should be applied at any one time. 2. mounted on an fr4 board.
electrical characteristics 1 v adp = 5v, t a = -40c to +85c, unless otherwise noted. typical values are at t a = 25c. symbol description conditions min typ max units operation adp adapter voltage range 4.0 5.5 v v adpp adapter present indicator threshold 4.25 4.5 4.7 v voltage v uvlo under-voltage lockout (uvlo) rising edge 3.0 v uvlo hysteresis 150 mv i op operating current charge current = 100ma 0.75 1.5 ma i sleep sleep mode current aat3687: v bat = 4.25v 0.3 1.0 a aat3687-1, aat3687-2: 13 v bat = 4.25v i leakage reverse leakage current from v bat = 4v, adp pin open 1.0 a bat pin voltage regulation v bat _ eoc 1 end of charge voltage accuracy 4.158 4.20 4.242 v v ch /v ch output charge voltage tolerance 0.5 % v min preconditioning voltage threshold aat3687, aat3687-1 only 2.8 3.0 3.15 v v rch battery recharge voltage threshold v bat _ eoc - 0.1 v current regulation i ch charge current 100 1500 ma i ch /i ch charge current regulation tolerance 10 % v adpset adpset pin voltage cc mode 2.0 v k ia current set factor: i ch /i adpset 4000 charging devices r ds(on) adapter charging transistor v in = 5.5v 0.2 0.25 0.35 on resistance aat3687 lithium-ion/polymer battery charger 4 3687.2006.10.1.7 1. the aat3687 output charge voltage is specified over the 0 to 70c ambient temperature range; operation over the -40c to +8 5c temperature range is guaranteed by design.
electrical characteristics 1 v adp = 5v, t a = -40c to +85c, unless otherwise noted. typical values are at t a = 25c. symbol description conditions min typ max units logic control / protection v en(h) input high threshold 1.6 v v en(l) input low threshold 0.4 v i en(h) en input current aat3687-1, aat3687-2 only; 10 a v en = 5v v adpp# output low voltage adpp# pin sinks 500 a 0.4 v t c preconditioning and constant c ct = 100nf, v adp = 5.5v 3.0 hours current mode time out t p preconditioning time out aat3687, aat3687-1 only; 25 minutes c ct = 100nf, v adp = 5.5v t v constant voltage mode time out c ct = 100nf, v adp = 5.5v 3.0 hours v s tat output low voltage stat pin sinks 4ma 0.4 v i s tat stat pin current sink capability 8.0 ma v ovp over-voltage protection threshold 4.4 v i tk /i chg pre-charge current aat3687, aat3687-1 only 10 % i term /i chg charge termination threshold 7.5 % current i ts current source from ts pin 70 80 90 a ts1 ts hot temperature fault threshold 310 330 350 mv hysteresis 15 ts2 ts cold temperature fault threshold 2.2 2.3 2.4 v hysteresis 10 mv i d ata data pin sink current data pin is active low state 3 ma i adpp# adpp# current sink adpp# pin is active low state 8 ma v data(h) input high threshold 1.6 v v data(l) input low threshold 0.4 v sq pulse status request pulse width status request 200 ns t period system clock period 50 s f d ata data output frequency 20 khz t reg thermal loop regulation 90 c t loop _ in thermal loop entering threshold 110 c t loop _ out thermal loop exiting threshold 85 c t ovsd over-temperature shutdown 145 c threshold aat3687 lithium-ion/polymer battery charger 3687.2006.10.1.7 5 1. the aat3687 output charge voltage is specified over the 0 to 70c ambient temperature range; operation over the -40c to +8 5c temperature range is guaranteed by design.
typical characteristics aat3687 lithium-ion/polymer battery charger 6 3687.2006.10.1.7 fast charge current vs. temperature (adpset = 8.06k ) temperature ( 900 920 940 960 980 1000 1020 1040 1060 1080 1100 -50 -25 0 25 50 75 100 preconditioning i ch vs. temperature (adpset = 8.06k ) temperature ( 80 90 100 110 120 -50 -25 0 25 50 75 100 preconditioning threshold voltage vs. temperature temperature ( c) v min (v) 2.95 2.96 2.97 2.98 2.99 3.00 3.01 3.02 3.03 3.04 3.05 -50 -25 0 25 50 75 100 end of charge voltage regulation vs. temperature temperature ( c) v bat (v) 4.158 4.179 4.200 4.221 4.242 -50 -25 0 25 50 75 100 battery voltage vs. supply voltage supply voltage (v) v bat (v) 4.158 4.179 4.200 4.221 4.242 4.5 4.75 5.0 5.25 5.5 i fastcharge vs. r set r set (k ) i fastcharge (ma) 10 100 1000 10000 1 10 100
typical characteristics aat3687 lithium-ion/polymer battery charger 3687.2006.10.1.7 7 counter timeout vs. temperature (ct = 0.1 f) temperature ( -10 -8 -6 -4 -2 0 2 4 6 8 10 -50 -25 0 25 50 75 100 adapter mode supply current vs. adpset resistor adpset resistor (k ) i q (ma) 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 1 10 100 1000 pre-conditioning constant current v il vs. supply voltage en pin (falling) supply voltage (v) v ih (v) 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 5.8 6.0 -40 c +25 c +85 c v ih vs. supply voltage en pin (rising) supply voltage (v) v ih (v) 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 5.8 6.0 -40 c +25 c +85 c fast charge current vs. supply voltage (adpset = 8.06k ) supply voltage (v) i ch (ma) 0 200 400 600 800 1000 1200 4.0 4.5 5.0 5.5 6. 0 v bat = 3.3v v bat = 3.5v v bat = 3.9v charging current vs. battery voltage (adpset = 8.06k ; v in = 5.0v) battery voltage (v) i ch (a) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 2.5 2.9 3.3 3.7 4.1 4.5
typical characteristics aat3687 lithium-ion/polymer battery charger 8 3687.2006.10.1.7 temperature sense output current vs. temperature temperature ( c) ts pin current ( 72 74 76 78 80 82 84 86 88 -50 -25 0 25 50 75 10 0 ct pin capacitance vs. counter timeout time (hours) capacitance ( f) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 0246810 precondition timeout precondition + constant current timeout or constant voltage timeout
aat3687 lithium-ion/polymer battery charger 3687.2006.10.1.7 9 functional block diagram functional description the aat3687 is a highly integrated single-cell lithium- ion/polymer battery charger ic designed to operate with standard ac adapter input sources, while requir- ing a minimum number of external components. the aat3687 precisely regulates battery charge voltage and current for 4.2v lithium-ion/polymer battery cells. the adapter charge input constant current level can be programmed up to 1.5a for rapid charging appli- cations. the aat3687 is rated for operation from - 40c to +85c. in the event of operating ambient temperatures exceeding the power dissipation abili- ties of the device package for a given constant current charge level, the charge control will enter into thermal regulation. when the system thermal regulation becomes active, the programmed constant current charge amplitude will be automatically reduced to a safe level for the current operating condition. should the ambient operating temperature drop below the thermal loop threshold, the system will automatically resume charging at the full programmed constant cur- rent level. this intelligent thermal management sys- tem permits the aat3687 to operate and safely charge a battery cell over a wide range of ambient conditions while maximizing the greatest possible charge current for the given set of conditions. status monitor output pins are provided to indicate the battery charge state by directly driving two exter- nal leds. a serial interface output is also available to report any one of 12 distinct charge states to the sys- tem microcontroller. battery temperature and charge state are fully moni- tored for fault conditions. in the event of an over-volt- age or over-temperature failure, the device will auto- matically shut down, thus protecting the charging device, control system, and the battery under charge. in addition to internal charge controller thermal pro- tection, the aat3687 also provides a temperature sense feedback function (ts pin) from the battery to shut down the device in the event the battery exceeds its own thermal limit during charging. all fault events are reported to the user either by the sim- ple status leds or via the data pin function. 1. precharge applies to aat3687 and aat3687-1 only. charge control reverse blocking cv/ precharge 1 constant current current compare adp bat a dpset uvlo over- temperature protection charge status stat2 stat1 ts window comparator 80 a 4.2v serial data data watchdog timer ct voltage sense adpp# en gnd ic enable
aat3687 lithium-ion/polymer battery charger 10 3687.2006.10.1.7 charging operation the aat3687 has four basic modes for the battery charge cycle: pre-conditioning / trickle charge; con- stant current / fast charge; constant voltage; and end of charge (see figure 1.) (aat3687-2 does not have trickle charge.) battery preconditioning before the start of charging, the aat3687 checks several conditions in order to assure a safe charging environment. 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 from the battery, must be within the proper window for safe charging. when these conditions have been met and a battery is connected to the bat pin, the aat3687 checks the state of the battery. if the cell voltage is below the preconditioning voltage threshold (v min ), the charge control begins preconditioning the cell. the battery preconditioning trickle charge current is equal to the fast charge constant current divided by 10. for example, if the programmed fast charge current is 1.5a, then the preconditioning mode (trickle charge) current will be 150ma. cell precon- ditioning is a safety precaution for deeply dis- charged battery cells and also aids in limiting power dissipation in the pass transistor when the voltage across the device is at the greatest potential. fast charge / constant current charging battery cell preconditioning continues until the volt- age on the bat pin exceeds the preconditioning voltage threshold (v min ). at this point, the aat3687 begins the constant current fast charging phase. the fast charge constant current (i cc ) amplitude is programmed by the user via the r set resistor. the aat3687 remains in the constant current charge mode until the battery reaches the voltage regula- tion point, v bat . constant voltage charging the system transitions to a constant voltage charg- ing mode when the battery voltage reaches the output charge regulation threshold (v bat ) during the constant current fast charge phase. the regu- lation voltage level is factory programmed to 4.2v (1%). charge current in the constant voltage mode drops as the battery cell under charge reach- es its maximum capacity. end of charge cycle termination and recharge sequence when the charge current drops to 7.5% of the pro- grammed fast charge current level in the constant voltage mode, the device terminates charging and goes into a sleep state. the charger will remain in a sleep state until the battery voltage decreases to a level below the battery recharge voltage thresh- old (v rch ). when the input supply is disconnected, the charg- er will automatically transition into a power-saving sleep mode. only consuming an ultra-low 0.3 ain sleep mode (1 a for aat3687-1 and aat3687-2), the aat3687 minimizes battery drain when it is not charging. this feature is particularly useful in appli- cations where the input supply level may fall below the battery charge or under-voltage lockout level. in such cases where the aat3687 input voltage drops, the device will enter sleep mode and auto- matically resume charging once the input supply has recovered from the fault condition. figure 1: current vs. voltage profile during charging phases. constant current charge phase constant voltage charge phase preconditioning trickle charge phase charge complete voltage constant current mode voltage threshold regulated current trickle charge and termination threshold i = cc / 10 i = max cc
aat3687 lithium-ion/polymer battery charger 3687.2006.10.1.7 11 system operation flow chart application information adapter power input constant current charge levels up to 1.5a may be programmed by the user when powered from a suf- ficient input power source. the aat3687 will oper- ate from the adapter input over a 4.0v to 5.5v range. the constant current fast charge current for the adapter input is set by the r set resistor connected between the adpset and ground. refer to table 1 for recommended r set values for a desired con- stant current charge level. the presence of voltage on the adapter input is indicated by the adpp# pin function. this indicator pin uses an internal open drain device that will pull the adpp# pin low when yes yes yes yes yes yes yes yes no no no no no no no no no no set enable timing expire yes (aat3687) yes output adpp adp voltage adp > v adpp uvlo v p > v uvlo thermal loop sleep mode switch power on reset adp loop fault conditions monitor ov, ot battery temperature monitor v ts1 < ts < v ts2 recharge test v rch > v bat preconditioning test v min > v bat yes (aat3687-2) current phase test v eoc > v bat voltage phase test i bat > i term charge completed voltage charging mode current charging mode low current conditioning battery temperature shut down charge safety timer thermal loop current reduction device temperature monitor t j > 110 c
aat3687 lithium-ion/polymer battery charger 12 3687.2006.10.1.7 voltage is detected on the adp pin. the precise charging function of the aat3687 may be read from the data pin and/or status leds. please refer to the battery charge status indication discussion for further details on data reporting. thermal loop control due to the integrated nature of the linear charging control pass device for the adapter input, a special thermal loop control system has been employed to maximize charging current under all operating con- ditions. the thermal management system meas- ures the internal circuit die temperature and reduces the fast charge current when the device exceeds a preset internal temperature control threshold. once the thermal loop control becomes active, the fast charge current is initially reduced by a factor of 0.44. the initial thermal loop current can be estimated by the following equation: eq. 1: the thermal loop control re-evaluates the circuit die temperature in 330ms intervals and adjusts the fast charge current back up in small steps to the full fast charge current level or until an equilibrium current is discovered and maximized for the given ambient temperature condition. the thermal loop controls the system charge level; therefore, the aat3687 will always provide the highest level of constant current in the fast charge mode possible for any given ambient temperature condition. adapter input charge inhibit and resume the aat3687 has a uvlo and power on reset fea- ture so that the charger will suspend charging and shut down if the input supply to the adapter pin drops below the uvlo threshold. when power is re-applied to the adapter pin or the uvlo condi- tions recovers, the system charge control will assess the state of charge on the battery cell and will automatically resume charging in the appropri- ate mode for the condition of the battery. enable / disable the aat3687 provides an enable function to control the charger ic on and off. the enable (en) pin is active high. when pulled to a logic low level, the aat3687 will be shut down and forced into the sleep state. charging will be halted regardless of the bat- tery voltage or charging state. when the device is re- enabled, the charge control circuit will automatically reset and resume charging functions with the appro- priate charging mode based on the battery charge state and measured cell voltage on the bat pin. programming charge current the fast charge constant current charge level is user programmed with a set resistor placed between the adpset pin and ground. the accu- racy of the fast charge, as well as the precondi- tioning trickle charge current, is dominated by the tolerance of the set resistor used. for this reason, a 1% tolerance metal film resistor is recommended for the set resistor function. fast charge constant current levels from 50ma to 1.5a can be set by selecting the appropriate resis- tor value from table 1. table 1: recommended r set values. adp adp i cc r set (k )i cc r set (k ) 50 n/a 800 10.2 75 n/a 900 9.09 100 84.5 1000 8.06 200 43.2 1100 7.32 300 28.0 1200 6.65 400 21.0 1300 6.04 500 16.9 1400 5.62 600 13.3 1500 5.36 700 11.5 i tloop = i cc 0.44
aat3687 lithium-ion/polymer battery charger 3687.2006.10.1.7 13 figure 2: i fastcharge vs. r set . protection circuitry programmable watchdog timer the aat3687 contains a watchdog timing circuit to shut down charging functions in the event of a defective battery cell not accepting a charge over a preset period of time. typically, a 0.1 f ceramic capacitor is connected between the ct pin and ground. when a 0.1 f ceramic capacitor is used, the device will time out a shutdown condition if the trickle charge mode exceeds 25 minutes (aat3687 and aat3687-1 only) and a combined trickle charge plus fast charge mode of 3 hours. when the device transitions to the constant voltage mode, the timing counter is reset and will time out after an additional 3 hours if the charge current does not drop to the charge termination level. table 2: summary for a 0.1 f ceramic capacitor used for the timing capacitor. the ct pin is driven by a constant current source and will provide a linear response to increases in the timing capacitor value. thus, if the timing capacitor were to be doubled from the nominal 0.1 f value, the time-out periods would be doubled. if the programmable watchdog timer function is not needed, it can be disabled by terminating the ct pin to ground. the ct pin should not be left float- ing or un-terminated, as this will cause errors in the internal timing control circuit. the constant current provided to charge the timing capacitor is very small, and this pin is susceptible to noise and changes in capacitance value. therefore, the timing capacitor should be physical- ly located on the printed circuit board layout as close as possible to the ct pin. since the accura- cy of the internal timer is dominated by the capaci- tance value, a 10% tolerance or better ceramic capacitor is recommended. ceramic capacitor materials, such as x7r and x5r types, are a good choice for this application. over-voltage protection an over-voltage event is defined as a condition where the voltage on the bat pin exceeds the maximum battery charge voltage and is set by the over-voltage protection threshold (v ovp ). if an over-voltage condition occurs, the aat3687 charge control will shut down the device until the voltage on the bat pin drops below v ovp . the aat3687 will resume normal charging operation after the over-voltage condition is removed. during an over- voltage event, the stat leds will report a system fault, and the actual fault condition can be read via the data pin signal. over-temperature shutdown the aat3687 has a thermal protection control cir- cuit which will shut down charging functions should the internal die temperature exceed the preset thermal limit threshold. battery temperature fault monitoring in the event of a battery over-temperature condi- tion, the charge control will turn off the internal pass device and report a battery temperature fault on the data pin function. the stat leds will also dis- play a system fault. after the system recovers from a temperature fault, the device will resume charg- ing operation. the aat3687 checks battery temperature before starting the charge cycle, as well as during all stages of charging. this is accomplished by moni- toring the voltage at the ts pin. this system is intended for use with negative temperature coeffi- cient thermistors (ntc) which are typically inte- grated into the battery package. most of the com- monly used ntc thermistors in battery packs are mode time trickle charge (tc) 25 minutes (aat3687 time out (and aat3687-1 only) trickle charge (tc) + fast 3 hours charge (cc) time out constant voltage (vc) 3 hours mode time out r set (k ) i fastcharge (ma) 10 100 1000 10000 1 10 100
aat3687 lithium-ion/polymer battery charger 14 3687.2006.10.1.7 approximately 10k at room temperature (25c). the ts pin has been specifically designed to source 80 a of current to the thermistor. the volt- age on the ts pin resulting from the resistive load should stay within a window of 335mv to 2.32v. if the battery becomes too hot during charging due to an internal fault or excessive fast charge current, the thermistor will heat up and reduce in value, pulling the ts pin voltage lower than the ts1 threshold, and the aat3687 will signal the fault condition. if the use of the ts pin function is not required by the system, it should be terminated to ground using a 10k resistor. alternatively, on the aat3687-1 and aat3687-2, the ts pin may be left open. battery charge status indication the aat3687 indicates the status of the battery under charge with two different systems. first, the device has two status led driver outputs. these two leds can indicate simple functions such as no battery charge activity, battery charging, charge complete, and charge fault. the aat3687 also provides a bi-directional data reporting function so that a system microcontroller can interrogate the data pin and read any one of 12 system states. status indicator display simple system charging status states can be dis- played using one or two leds in conjunction with the stat1 and stat2 pins on the aat3687. these two pins are simple open drain switches used to connect the led cathodes to ground. it is not necessary to use both display leds if a user simply wants to have a single lamp to show "charg- ing" or "not charging." this can be accomplished by using the stat1 pin and a single led. using two leds and both stat pins simply gives the user more information to the charging states. refer to table 3 for led display definitions. the led anodes should be connected to v adp . the leds should be biased with as little current as necessary to create reasonable illumination; there- fore, a ballast resistor should be placed between the led cathodes and the stat1/2 pins. led cur- rent consumption will add to the overall thermal power budget for the device package, hence it is good to keep the led drive current to a minimum. 2ma should be sufficient to drive most low-cost green or red leds. it is not recommended to exceed 8ma for driving an individual status led. the required ballast resistor values can be esti- mated using the following formulas: eq. 2: example: eq. 3: note: red led forward voltage (v f ) is typically 2.0v @ 2ma table 3: led status indicator. event description stat1 stat2 charge disabled or low supply off off charge enabled without battery flash 1 flash 1 battery charging on off charge completed off on fault on on 1. flashing rate depends on output capacitance. (5.5v - 2.0 v) r b(stat1) = = 1.75k 2ma (v adp - v f(led) ) r b(stat1/2) = i led(stat1/2)
aat3687 lithium-ion/polymer battery charger 3687.2006.10.1.7 15 data timing the system microcontroller should assert an active low data request pulse for minimum duration of 200ns; this is specified by t lo(data) . upon sensing the rising edge of the end of the data request pulse, the aat3687 status data control will reply the data word back to the system microcontroller after a delay specified by the data report time specification t data(rpt) . the period of the following group of data pulses will be specified by t d ata . digital charge status reporting the aat3687 has a comprehensive digital data reporting system by use of the data pin feature. this function can provide detailed information regarding the status of the charging system. the data pin is a bi-directional port which will read back a series of data pulses when the system microcontroller asserts a request pulse. this sin- gle strobe request protocol will invoke one of 12 possible return pulse counts that the system micro- controller can look up based on the serial report data listed in table 4. the data pin function logic is active low and should normally be pulled high to v adp . this data line can also be pulled high to the same level as the high state for the logic i/o port on the system microcontroller. in order for the data pin control circuit to generate clean, sharp edges for the data output, and to maintain the integrity of the data tim- ing for the system, the pull-up resistor on the data line should be low enough in value so that the data signal returns to the high state without delay. if the pull-up resistor is too high, the strobe pulse from the system microcontroller could exceed the maximum pulse time and the data output control could issue false status reports. a 1.5k resistor is recommended when pulling the data pin high to 5.0v on the v adp input. if the data line is pulled high to a voltage level less than 5.0v, the pull-up resistor can be calculated based on a recommend- ed minimum pull-up current of 3ma. use the fol- lowing formula: eq. 4: figure 3: data pin application circuit. v pull-up r pull-up 3ma aat3687 status control 1.8v to 5.0v data pin r pull_up p gpio port gpio in in out out
aat3687 lithium-ion/polymer battery charger 16 3687.2006.10.1.7 timing diagram table 4: serial data report table. n data report status 1 chip over-temperature shutdown. 2 battery temperature fault. 3 over-voltage turn off. 4 not used. 5 adp watchdog time-out in battery condition mode. 6 adp battery condition mode. 7 adp watchdog time-out in constant current mode. 8 adp thermal loop regulation in constant current mode. 9 adp constant current mode. 10 adp watchdog time-out in constant voltage mode. 11 adp constant voltage mode. 12 adp end of charging. 23 data report error. sq sq pulse data system reset system start ck t sync t lat n=1 n=2 n=3 t off t data(rpt) = t sync + t lat < 2.5 p data t off > 2 p data p data
aat3687 lithium-ion/polymer battery charger 3687.2006.10.1.7 17 thermal considerations the aat3687 is offered in a 3x3mm tdfn pack- age which can provide up to 2.0w of power dissi- pation when it is properly bonded to a printed cir- cuit board and has a maximum thermal resistance of 50c/w. many considerations should be taken into account when designing the printed circuit board layout, as well as the placement of the charger ic package in proximity to other heat gen- erating devices in a given application design. the ambient temperature around the charger ic will also have an effect on the thermal limits of a bat- tery charging application. the maximum limits that can be expected for a given ambient condition can be estimated by the following discussion. first, the maximum power dissipation for a given situation should be calculated: eq. 5: where: p d = total power dissipation by the device v in = input voltage amplitude, v adp v bat = battery voltage as seen at the bat pin i cc = maximum constant fast charge current programmed for the application i op = quiescent current consumed by the charger ic for normal operation next, the maximum operating ambient temperature for a given application can be estimated based on the thermal resistance of the 3x3mm tdfn pack- age when sufficiently mounted to a pcb layout and the internal thermal loop temperature threshold. eq. 6: where: t a = ambient temperature in c t j = maximum device junction temperature below the thermal loop threshold p d = total power dissipation by the device ja = package thermal resistance in c/w example: for an application where the fast charge current for the adapter mode is set to 1a, v adp = 5.0v and the battery voltage at 3.6v, what is the maximum ambi- ent temperature at which the thermal loop will become active? given: v adp = 5.0v v bat = 3.6v i cc = 1a i op = 0.75ma t j = 110c ja = 50c/w using equation 5, calculate the device power dissi- pation for the stated condition: eq. 7: the maximum ambient temperature before the aat3687 thermal loop becomes active can now be calculated using equation 6: eq. 8: therefore, under the stated conditions for this worst case power dissipation example, the aat3687 will enter the thermal loop and lower the fast charge constant current when the ambient operating temperature rises above 39.8c. t a = 110 c - ( 50 c/w 1.40375w) = 39.8125 c p d = (5.0v - 3.6v) (1a) + (5.0v 0.75ma) = 1.40375w t a = t j - ( ja p d ) p d = [(v in - v bat ) i cc + (v in i op )]
aat3687 lithium-ion/polymer battery charger 18 3687.2006.10.1.7 capacitor selection input capacitor in general, it is good design practice to place a decoupling capacitor between the adp pin and ground. an input capacitor in the range of 1 f to 22 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 during device enable and when battery charging is initiated. if the aat3687 adapter input is to be used in a sys- tem with an external power supply source, such as a typical ac-to-dc wall adapter, then a c in capac- itor in the range of 10 f should be used. a larger input capacitor in this application will minimize switching or power transient effects when the power supply is "hot plugged" in. output capacitor the aat3687 only requires a 1 f ceramic capaci- tor on the bat pin to maintain circuit stability. this value should be increased to 10 f or more if the battery connection is made any distance from the charger output. if the aat3687 is to be used in applications where the battery can be removed from the charger, such as with desktop charging cradles, an output capacitor greater than 10 f may be required to prevent the device from cycling on and off when no battery is present. printed circuit board layout considerations for the best results, it is recommended to physi- cally place the battery pack as close as possible to the aat3687 bat pin. to minimize voltage drops on the pcb, keep the high current carrying traces adequately wide. for maximum power dissipation of the aat3687 3x3mm tdfn package, the metal substrate should be solder bonded to the board. it is also recommended to maximize the substrate contact to the pcb ground plane layer to further increase local heat dissipation. refer to the aat3687 evaluation board for a good layout exam- ple (see figures 4 and 5). aat3687 evaluation board layout figure 4: aat3687 evaluation board figure 5: aat3687 evaluation board component side layout. solder side layout.
aat3687 lithium-ion/polymer battery charger 3687.2006.10.1.7 19 aat3687 evaluation board schematic diagram d2 d1 red led red led grn led d3 0 r1 c1 10 f c2 10 f r2 10k r6 8.06k r7 1.5k r5 1.5k r4 1.5k r3 1.5k c3 0.1 f sw1 dat a ct 1 2 3 on/off termb3 termb2 termb2 j1 1 2 1 2 3 adp bat ts gnd gnd adp 2 en 4 gnd 310 bat 1 adpp# 5 ts 6 data 7 stat2 8 stat1 9 ct adpset 12 aat3687 u1 (tdfn33-12)
aat3687 lithium-ion/polymer battery charger 20 3687.2006.10.1.7 aat3687 evaluation board bill of materials (bom) quantity description desig. footprint manufacturer part number 1 test pin data pad mill-max 6821-0-0001-00-00-08-0 1 connecting terminal block, adp, gnd tblok2 phoenix contact 277-1274-nd 2.54mm, 2 position 1 connecting terminal block, bat, tblok3 phoenix contact 277-1273-nd 2.54mm, 3 position gnd, ts 2 capacitor, ceramic, 10 f c1, c2 0805 murata 490-1717-1-nd 6.3v 10% x5r 0805 1 capacitor, ceramic, 1 f c3 0603 murata 478-1244-2-nd 10% 25v x5r 0603 2 typical red led, ultra-bright d1, d3 1206led chicago miniature cmd15-21src/tr8 lamp 1 typical green led d2 1206led chicago miniature cmd15-21vgc/tr8 lamp 1 header, 3-pin j1 header2mm-3 sullins 6821-0-0001-00-00-08-0 1 resistor, 10k , 1/16w r2 0603 panasonic/ecg p10kcfct-nd 5% 0603 smd 1 resistor, 8.06k , 1/16w r6 0603 panasonic/ecg p8.06khct-nd 1% 0603 smd 4 resistor, 1.5k , 1/16w r3, r4, 0603 panasonic/ecg p1.5kcgct-nd 5% 0603 smd r5, r7 1 switch tact 6mm spst sw1 switch itt industries/ ckn9012-nd h = 5.0mm c&k div 1 aat3687 lithium-ion/polymer u1 tdfn33-12 analogictech aat3687iwp-4.2 battery charge controller
aat3687 lithium-ion/polymer battery charger 3687.2006.10.1.7 21 ordering information package information all dimensions in millimeters. trickle charge package marking 1 part number (tape and reel) 2 yes tdfn33-12 pixyy aat3687iwp-4.2-t1 yes tdfn33-12 tqxyy aat3687iwp-4.2-1-t1 no tdfn33-12 rtxyy aat3687iwp-4.2-2-t1 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold . top view bottom view detail "b" detail "a" side view 3.00 2.40 + all analogictech products are offered in pb-free packaging. the term ?pb-free? means semiconductor products that are in compliance with current rohs standards, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. for more information, please visit our website at http://www.analogictech.com/pbfree.
aat3687 lithium-ion/polymer battery charger 22 3687.2006.10.1.7 advanced analogic technologies, inc. 830 e. arques avenue, sunnyvale, ca 94085 phone (408) 737-4600 fax (408) 737-4611 ? advanced analogic technologies, inc. analogictech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an analogictech pr oduct. no circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. analogictech reserves the right to make changes to their products or specifi cations or to discontinue any product or service without notice. customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information b eing relied on is current and complete. all products are sold sub- ject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. analogictech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with anal ogictech?s standard warranty. testing and other quality con- trol techniques are utilized to the extent analogictech deems necessary to support this warranty. specific testing of all param eters of each device is not necessarily performed. analogictech and the analogictech logo are trademarks of advanced analogic technologies incorporated. all other brand and produ ct names appearing in this document are regis- tered trademarks or trademarks of their respective holders.

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