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aat3688 usb port lithium-ion/polymer battery charger 3688.2006.10.1.5 1 batterymanager ? general description the aat3688 batterymanager? is a highly inte- grated single cell lithium-ion/polymer battery charger ic designed to operate with usb port inputs. it requires the minimum number of external components. the aat3688 precisely regulates battery charge voltage and current for 4.2v lithium-ion/polymer battery cells. depending on the usb port type, the aat3688 charge current can be programmed for two separate levels up to 500ma. an optional charge reduction loop is built in to allow users to charge the battery with available current from a usb port, while keeping the port voltage regulated. 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 any one of 14 various status states to a microcontroller. the aat3688 is available in a pb-free, thermally- enhanced, space-saving 12-pin 3x3mm tdfn package and is rated over the -40c to +85c tem- perature range. features ? usb charger ? programmable up to 500ma max ? 4.0v to 5.5v input voltage range ? high level of integration with internal: ? charging device ? reverse blocking diode ? current sensing ? automatic recharge sequencing ? charge reduction loop for usb charging ? battery temperature monitoring ? full battery charge auto turn-off ? over-voltage protection ? emergency thermal protection ? power on reset and soft start ? serial interface status reporting ? 12-pin 3x3mm tdfn package applications ? bluetooth? headsets ? cellular telephones ? digital still cameras ? hand-held pcs ? mp3 players ? personal data assistants (pdas) ? other lithium-ion/polymer battery-powered devices typical application aat3688 c2 10 f batt- temp usb input battery pack serial data usb usbsel gnd ts bat batt+ usb hi/lo select stat1 r seth usbh r setl usbl chr en stat2 data enable
aat3688 usb port lithium-ion/polymer battery charger 2 3688.2006.10.1.5 pin descriptions pin configuration tdfn33-12 (top view) pin # name type function 1 usb in usb power supply input. 2 bat in/out battery charging and sensing. 3 gnd ground ground connection. 4 chr in/out resistor divider to set usb voltage regulation for charge reduction mode. leave this pin open for default 4.5v usb regulation point. tie to usb pin to disable this function. 5 en in enable pin. logic high enables the ic. 6 ts in/out connect to 10k ntc thermistor. 7 data in/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 usbsel in when usb is present, use this pin to toggle between usbh and usbl charging levels. 11 usbl in/out connect resistor here to set charge current for low-current usb port. 12 usbh in/out connect resistor here to set charge current for high-current usb port. ep exposed paddle (bottom); connect to gnd directly beneath package. usb bat gnd 1 chr en ts usbh usbl usbsel stat1 stat2 data 2 3 4 5 6 12 11 10 9 8 7
aat3688 usb port lithium-ion/polymer battery charger 3688.2006.10.1.5 3 absolute maximum ratings 1 thermal information 2 symbol description value units ja maximum thermal resistance (3x3mm tdfn) 50 c/w p d maximum power dissipation 2.0 w symbol description value units v p usb input voltage, <30ms, duty cycle <10% -0.3 to 7.0 v v p usb input voltage, continuous -0.3 to 6.0 v v n bat, usbsel, usbh, usbl, stat1, stat2, data, ts, chr, en -0.3 to v vp + 0.3 v t j operating junction temperature range -40 to 150 c t lead maximum soldering temperature (at leads) 300 c 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.
aat3688 usb port lithium-ion/polymer battery charger 4 3688.2006.10.1.5 electrical characteristics 1 v adp = 5v, t a = -25c to +85c, unless otherwise noted. typical values are at t a = 25c. symbol description conditions min typ max units operation usb input voltage range 4.0 5.5 v v uvlo under-voltage lockout rising edge 3.0 v under-voltage lockout hysteresis 150 mv i op operating current cc charge current = 500ma 0.75 1.5 ma i sleep sleep mode current v bat = 4.25v 0.3 1.0 a i leakage reverse leakage current from v bat = 4v, usb pin open 1.0 a bat pin voltage regulation v bat _ eoc 1 end of charge voltage accuracy 4.158 4.2 4.242 v v bat /v bat eoc voltage tolerance 0.5 % v min preconditioning voltage threshold 2.8 3.0 3.15 v v rch battery recharge voltage threshold v bat _ eoc - 0.1 v v usb _ chr usb charge reduction regulation no connection on chr pin 4.3 4.5 4.64 v v chr chr pin voltage accuracy 1.9 2.0 2.1 v current regulation i ch charge current 50 500 ma i ch /i ch charge current regulation 10 % tolerance v usbh usbh pin voltage cc mode 2.0 v v usbl usbl pin voltage cc mode 2.0 v k iuh current set factor: i charge /i usbh 2000 k iul current set factor: i charge /i usbl 2000 charging devices r ds(on)u usb charging transistor v in = 5.5v 0.4 0.5 0.65 on resistance 1. the aat3688 output charge voltage is specified over the 0 to 70c ambient temperature range; operation over the -25c to +8 5c temperature range is guaranteed by design.
aat3688 usb port lithium-ion/polymer battery charger 3688.2006.10.1.5 5 electrical characteristics 1 v adp = 5v, t a = -25c to +85c, unless otherwise noted. typical values are at t a = 25c. symbol description conditions min typ max units logic control / protection v usbsel(h) input high threshold 1.6 v v usbsel(l) input low threshold 0.4 v v en(h) input high threshold 1.6 v v en(l) input low threshold 0.4 v 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 for usbh mode 10 % for usbl mode 50 i term /i chg charge termination threshold current for usbh mode 7.5 % i term /i chg charge termination threshold current for usbl mode 35 % 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_data data pin sink current data pin is active low state 3.0 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 ovsd over-temperature shutdown threshold 145 c 1. the aat3688 output charge voltage is specified over the 0 to 70c ambient temperature range; operation over the -25c to +8 5c temperature range is guaranteed by design.
aat3688 usb port lithium-ion/polymer battery charger 6 3688.2006.10.1.5 typical characteristics preconditioning charge current vs. temperature (usbh; usbh = 8.06k ) temperature ( 40 45 50 55 60 -50 -25 0 25 50 75 100 preconditioning threshold voltage vs. temperature temperature ( 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 vs. temperature temperature ( 4.158 4.179 4.200 4.221 4.242 -50 -25 0 25 50 75 100 recharge voltage vs. temperature temperature ( 4.040 4.050 4.060 4.070 4.080 4.090 4.100 4.110 4.120 4.130 4.140 -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 5.25 5.5 i fastcharge vs. r set r set (k 10 100 1000 1 10 100 1000 usbl usbh
aat3688 usb port lithium-ion/polymer battery charger 3688.2006.10.1.5 7 typical characteristics fast charge current vs. supply voltage (usbh; usbh = 8.06k ) supply voltage (v) i ch (ma) 0 100 200 300 400 500 600 4.40 4.50 4.60 4.70 4.80 4.90 5.00 0 c 25 c 70 c fast charge current vs. supply voltage (usbl; usbl = 40.2k ) supply voltage (v) i ch (ma) 0 20 40 60 80 100 120 4 4.5 5.5 6.5 56 v bat = 3.3v v bat = 3.5v v bat = 3.9v fast charge current vs. supply voltage (usbh; usbh = 8.06k ) supply voltage (v) i ch (ma) 0 100 200 300 400 500 600 4 4.25 4.5 4.75 5 5.25 5.5 5.75 6 v bat = 3.5v v bat = 3.3v v bat = 3.9v charging current vs. battery voltage (usbl; usbl = 40.2k ) battery voltage (v) i ch (ma) 0 20 40 60 80 100 120 2.5 3 3.5 4 4. 5 charging current vs. battery voltage (usbh; usbh = 8.06k 0 100 200 300 400 500 600 2.5 3 3.5 4 4.5 fast charge current vs. temperature (usbh; usbh = 8.06k ) temperature ( 440 450 460 470 480 490 500 510 520 530 540 -50 -25 0 25 50 75 100
aat3688 usb port lithium-ion/polymer battery charger 8 3688.2006.10.1.5 typical characteristics v il vs. supply voltage usbsel (falling) supply voltage (v) v il (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 5.2 5.4 5.6 5.8 6 -40 c +25 c +85 c v ih vs. supply voltage usbsel (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 5.2 5.4 5.6 5.8 6 -40 c +25 c +85 c v il vs. supply voltage en pin (falling) supply voltage (v) v il (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 5.2 5.4 5.6 5.8 6 -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 5.2 5.4 5.6 5.8 6 -40 c +25 c +85 c usb charge current vs. time (usbh; usbh = 8.06k 02 46810 charge reduction mode activated usb supply current vs. usbh resistor usbh resistor (k ) i q (ma) 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 1 10 100 100 0 constant current pre-conditioning
aat3688 usb port lithium-ion/polymer battery charger 3688.2006.10.1.5 9 typical characteristics 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 75 100
aat3688 usb port lithium-ion/polymer battery charger 10 3688.2006.10.1.5 functional block diagram functional description the aat3688 is a highly integrated single cell lithi- um-ion/polymer battery charger ic designed to operate from usb port v bus supplies, while requir- ing a minimum number of external components. the device precisely regulates battery charge volt- age and current for 4.2v lithium-ion/polymer bat- tery cells. the aat3688 is specifically designed to be pow- ered from a usb port v bus supply, but it can also be powered from any input voltage source capable supplying 4.5v to 5.5v for loads up to 500ma. depending on the usb port type, the aat3688 constant charge current can be externally pro- grammed for two levels, usb high and usb low, for maximum constant current charge levels up to 500ma. typically, the usb charge levels are set at 500ma and 100ma for the usbh and usbl modes; however, the user may program either mode to any level they desire below 500ma. the usbh/l mode has an automatic charge reduction loop control to allow users to charge the battery with limited available current from a usb port while maintaining the regulated port voltage. this sys- tem assures the battery charge function will not overload a usb port while charging if other system demands also share power with the respective port supply. 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 14 various charge states to a system microcontroller. 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. in addition to internal charge controller thermal protection, the aat3688 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 simple status leds or via the data pin function. charge control current compare reverse blocking cv/ precharge usb usbsel constant current bat uvlo over- temperature protect charge status stat2 stat1 ts window comparator 80a usbh usbl serial data data gnd charge reduction loop chr en ic enable
aat3688 usb port lithium-ion/polymer battery charger 3688.2006.10.1.5 11 charging operation the aat3688 has four basic modes for the battery charge cycle and is powered from the usb input: pre-conditioning/trickle charge; constant current/fast charge; constant voltage; and end of charge. for ref- erence, figure 1 shows the current versus voltage profile during charging phases. battery preconditioning before the start of charging, the aat3688 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. in addition, the cell temperature, as reported by a thermistor connected to the ts pin from the bat- tery, 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 aat3688 checks the state of the battery. if the cell voltage is below the preconditioning voltage threshold (v min ), the aat3688 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 500ma, then the preconditioning mode (trickle charge) current will be 50ma. cell precon- ditioning is a safety precaution for a deeply dis- charged battery and also aids in limiting power dis- sipation 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 aat3688 begins the constant current fast charging phase. the fast charge constant current (i cc ) amplitude is determined by the selected charge mode usbh or usbl and is programmed by the user via the r seth and r setl resistors. the aat3688 remains in con- stant current charge mode until the battery reaches the voltage regulation point, v bat . constant voltage charging the system transitions to a constant voltage charg- ing mode when the battery voltage reaches output charge regulation threshold (v bat ) during the con- stant current, fast charge phase. the regulation voltage level is factory programmed to 4.2v ( 1%). the charge current in the constant voltage mode drops as the battery cell under charge reaches 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 volt- age 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 threshold (v rch ). when the input supply is disconnected, the charg- er will also automatically enter power-saving sleep mode. only consuming an ultra-low 0.3a in sleep mode, the aat3688 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 aat3688 input volt- age drops, the device will enter the sleep mode and automatically resume charging once the input sup- ply has recovered from its 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
aat3688 usb port lithium-ion/polymer battery charger 12 3688.2006.10.1.5 system operation flow chart no no no no no no no no 0 1 yes yes yes yes yes yes switch on sleep mode uvlo v p > v uvlo yes yes usb power usb low current loop usb high current loop usb detect usbsel= ? power on reset fault conditions monitor ov, ot shut down mode battery temp. fault usb voltage regulation enable battery temperature monitor v ts1 < ts < v ts2 recharge test v rch > v bat preconditioning test v min > v bat low current conditioning charge usb voltage test v usb < 4.5v usb loop current reduction in usb charging mode current charging mode voltage charging mode current phase test v eoc > v bat voltage phase test i bat > i term charge completed
aat3688 usb port lithium-ion/polymer battery charger 3688.2006.10.1.5 13 application information usb system power charging the usb charge mode provides two programma- ble fast charge levels up to 500ma for each, usb high and usb low, usbh and usbl, respectively. the usbh or usbl modes may be externally selected by the usb select pin (usbsel). when the usbsel pin is connected to a logic high level, the usbh level will be active. conversely, when usbsel is pulled to a logic low level (ground), the usbl level will be used for fast charging. typically usbh is set for 500ma and usbl is set for 100ma. however, these two usb charge levels may be user programmed to any level between 50ma and 500ma by selecting the appropriate resistor values for r seth and r setl . refer to table 1 for recom- mended r seth and r setl values for the desired usb input constant current charge levels. usb charge reduction in many instances, product system designers do not know the real properties of a potential usb port to be used to supply power to the battery charger. typical powered usb ports commonly found on desktop and notebook pcs should supply up to 500ma. in the event a usb port being used to sup- ply the charger is unable to provide the pro- grammed fast charge current, or if the system under charge must also share supply current with other functions, the aat3688 will automatically reduce usb fast charge current to maintain port integrity and protect the host system. the usb charge reduction system becomes active when the voltage on the usb input falls below the usb charge reduction threshold (v usbchr ), which is typically 4.5v. regardless of which usb charge function is selected (usbh or usbl), the charge reduction system will reduce the fast charge cur- rent level in a linear fashion until the voltage sensed on the usb input recovers above the charge reduction threshold voltage. the usb charge reduction threshold (v usbchr ) may be externally set to a value lower than 4.5v by placing a resistor divider network between v usb and ground with the center connected to the chr pin. the usb charge reduction feature may be disabled by connecting a 10k resistor from the chr pin directly to the usb input pin. the following equation may be used to approximate a usb charge reduction threshold below 4.5v: eq. 1: where r11/r12 << 1m . table 1: recommended r set values. figure 2: internal equivalent circuit for the chr pin. usbh usbl i cc r set (k )r set (k ) 50 86.6 86.6 75 57.6 57.6 100 42.2 42.2 200 21.0 20.5 300 13.7 13.7 400 10.2 10.2 500 8.06 8.06 v usbchr = 2.0v r12 r12 + r11 1.025m 825k r11 r12 v chr = 2.0 v v usb usb chr
aat3688 usb port lithium-ion/polymer battery charger 14 3688.2006.10.1.5 usb input charge inhibit and resume the aat3688 uvlo and power on reset feature will function when the usb input pin voltage level drops below the uvlo threshold. at this point, the charger will suspend charging and shut down. when power is re-applied to the usb pin or the uvlo condition recovers, the system charge con- trol will assess the state of charge on the battery cell and will automatically resume charging in the appropriate mode for the condition of the battery. enable / disable the aat3688 provides an enable function to con- trol the charger ic on and off. the enable (en) pin is an active high. when pulled to a logic low level, the aat3688 will be shut down and forced into the sleep state. charging will be halted regardless of the battery voltage or charging state. when the device is re-enabled, the charge control circuit will automatically reset and resume charging functions with the appropriate charging mode based on the battery charge state and measured cell voltage. programming charge current the fast charge constant current charge level for the usb input is programmed with set resistors placed between the usbh and usbl pins and ground. the accuracy of the fast charge, as well as the precondi- tioning trickle charge current, is dominated by the tolerance of the set resistors used. for this reason, 1% tolerance metal film resistors are recommended for programming the desired constant current level. the usb input fast charge constant current charge control provides for two current set levels, usbh and usbl. the usbsel pin is used to select the high or low charge current levels in the usb charge mode. when the usbsel pin is pulled to a voltage level above the v usbsel(h) threshold, the usbh cur- rent level will be selected. conversely, this pin should be pulled below the v usbsel(l) to enable the usbl charge level. typically, the two r seth and r setl for the usbh and usbl functions are fixed for 500ma and 100ma usb fast charge levels. however, these two charge levels may be set to any level between 50ma and 500ma, depending upon the system design requirements for a given usb charge application. refer to table 1 and figure 3 for recommended r seth and r setl values. figure 3: i fastcharge vs. r set . protection circuitry 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 aat3688 charge control will shut down the device until voltage on the bat pin drops below the over-voltage protec- tion threshold (v ovp ). the aat3688 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; the actual fault condition may also be read via the data pin signal. over-temperature shutdown the aat3688 has a thermal protection control cir- cuit which will shut down charging functions should the internal die temperature exceed the preset thermal limit threshold. r set (k 10 100 1000 1 10 100 1000 usbl usbh
aat3688 usb port lithium-ion/polymer battery charger 3688.2006.10.1.5 15 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 charging operation. the aat3688 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 negative temperature coefficient (ntc) thermistors which are typically integrated into the battery package. most commonly used ntc thermistors used in battery packs are approximate- ly 10k at room temperature (25c). the ts pin has been specifically designed to source 80a of current to the thermistor. the voltage on the ts pin that results from the resistive load should stay with- in a window from 335mv to 2.32v. if the battery becomes too hot during charging due to an internal fault, the thermistor will heat up and reduce in value, thus pulling the ts pin voltage lower than the ts1 threshold, and the aat3688 will halt charging and 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. battery charge status indication the aat3688 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 aat3688 also provides a bi-directional data reporting function so that a system microcontroller may interrogate the data pin and read any one of 14 system states. status indicator display simple system charging status may be displayed using one or two leds in conjunction with the stat1 and stat2 pins on the aat3688. these two pins are simple switches to connect the display 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 "charging" or "not charging." this can be accomplished by just using the stat1 pin and a single led. using two leds and both stat pins simply gives the user more information for charging states. refer to table 2 for led dis- play definitions. table 2: led display status conditions. 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.
aat3688 usb port lithium-ion/polymer battery charger 16 3688.2006.10.1.5 the led anodes should be connected to v usb . the leds should be biased with as little current as necessary to create reasonable illumination; there- fore, a ballast resistor should be placed between each of the led cathodes and the stat1/2 pins. led current consumption will add to the over-ther- mal power budget for the device package, hence it is recommended to keep the led drive current to a minimum. 2ma should be sufficient to drive most low-cost green, red, or multi-color leds. it is not recommended to exceed 8ma for driving an indi- vidual status led. the required ballast resistor value can be estimat- ed using the following formulas: eq. 2: example: note: red led forward voltage (v f ) is typically 2.0v @ 2ma. table 2 shows the four status led display conditions. digital charge status reporting the aat3688 has a comprehensive digital data reporting system by use of the data pin feature. this function can provide detailed information regarding the state 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 14 possible return pulse counts in which the micro- controller can look up based on the serial report shown in table 3. the data pin function is active low and should nor- mally be pulled high to v usb . this data line may also be pulled high to the same level as the high state for the logic i/o port on the system microcon- troller. 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 timing 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 value of the pull-up resistor used is too high, the strobe pulse from the system microcontroller may exceed the maximum pulse time and the data output con- trol could issue false status reports. a 1.5k resis- tor is recommended when pulling the data pin high to 5.0v at the v usb input. if the data line is pulled high to a voltage level less than 5.0v, the pull-up resistor may be calculated based on a rec- ommended minimum pull-up current of 3ma. use the following formula: eq. 3: v pull-up r pull-up 3ma (5.0v - 2.0 v) r b(stat1) = = 1.5k 2ma (v usb - v f(led) ) r b(stat1/2) = i led(stat1/2)
aat3688 usb port lithium-ion/polymer battery charger 3688.2006.10.1.5 17 table 3: serial data report table. figure 4: data pin application circuit. n data report status 1 chip over-temperature shutdown 2 battery temperature fault 3 over-voltage turn off 4 not used 5 not used 6 not used 7 not used 8 not used 9 not used 10 not used 11 not used 12 not used 13 usbh battery condition mode 14 usbh charge reduction in constant current mode 15 usbh constant current mode 16 usbh constant voltage mode 17 usbh end of charging 18 usbl battery condition mode 19 usbl charge end of charging reduction in constant current mode 20 usbl constant current mode 21 usbl constant voltage mode 22 usbl end of charging 23 data report error aat3688 status control 1.8v to 5.0v data pin r pull_up p gpio port gpio in in out out
aat3688 usb port lithium-ion/polymer battery charger 18 3688.2006.10.1.5 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 aat3688 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 the t d ata specification. timing diagram thermal considerations the aat3688 is packaged in a pb-free, 3x3mm tdfn package which can provide up to 2.0w of power dissipation when it is properly bonded to a printed circuit 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 affect 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. 4: where: p d = total power dissipation by the device v in = input voltage level, v usb 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. 5: 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 t a = t j - ( ja p d ) p d = [(v in - v bat ) i cc + (v in i op )]
aat3688 usb port lithium-ion/polymer battery charger 3688.2006.10.1.5 19 where: t a = ambient temperature in degrees c t j = maximum device junction temperature protected by the thermal limit control p d = total power dissipation by the device ja = package thermal resistance in c/w example: for an application where the fast charge current is set to 500ma, v usb = 5.0v and the worst case bat- tery voltage at 3.0v, what is the maximum ambient temperature at which the thermal limiting will become active? given: v adp = 5.0v v bat = 3.0v i cc = 500ma i op = 0.75ma t j = 140c ja = 50c/w using equation 4, calculate the device power dissi- pation for the stated condition: eq. 6: the maximum ambient temperature before the aat3688 thermal limit protection will shut down charging can now be calculated using equation 5: eq. 7: therefore, under the stated conditions for this worst case power dissipation example, the aat3688 will suspend charging operations when the ambient operating temperature rises above 89.81c. capacitor selection input capacitor in general, it is good design practice to place a decoupling capacitor between the v usb pin and ground. an input capacitor in the range of 1f to 22f 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 aat3688 usb input is to be used in a system with an external power supply source rather than a usb port v bus , such as a typical ac-to-dc wall adapter, then a c in capacitor in the range of 10f 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. likewise, a 10f or greater input capacitor is recommended for the usb input to help buffer the effects of usb source power switch- ing noise and input cable impedance. output capacitor the aat3688 only requires a 1f ceramic capaci- tor on the bat pin to maintain circuit stability. this value should be increased to 10f or more if the battery connection is made any distance from the charger output. if the aat3688 is to be used in applications where the battery can be removed from the charger, such as in the case of desktop charging cradles, an output capacitor greater than 10f 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 aat3688 bat pin. to minimize voltage drops on the pcb, keep the high current carrying traces adequately wide. for maximum power dis- sipation of the aat3688 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 aat3688 evaluation board for a good layout example (see figures 5 and 6). p d = (5.0v - 3.0v) (500ma) + (5.0v 0.75ma) = 1.00375w t a = 140 c - ( 50 c/w 1.00375w) = 89.81 c
aat3688 usb port lithium-ion/polymer battery charger 20 3688.2006.10.1.5 aat3688 evaluation board layout figure 5: aat3688 evaluation board figure 6: aat3688 evaluation board component side layout. solder side layout.
aat3688 usb port lithium-ion/polymer battery charger 3688.2006.10.1.5 21 aat3688 evaluation board schematic diagram grn led d2 red led d1 8.06k r8 1.5k r5 1.5k r6 1.5k r9 open r3 10k r4 42.2k r7 10f c1 1 2 3 usbsel j2 sw1 lo hi dat a 1 2 3 on/off j1 usb 1 bat 2 gnd 3 chr 4 en 5 ts 6 data 7 stat2 8 stat1 9 usbsel 10 usbl 11 usbh 12 aat3688 u1 1 2 tb1 bat gnd ts usb gnd tdfn33-12 1 2 3 4 5 mini-b 10f c2 gnd id d+ d- vbus 1 2 3 tb2 open r2 open r1
aat3688 usb port lithium-ion/polymer battery charger 22 3688.2006.10.1.5 aat3688 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, usb,gnd tblok2 phoenix contact 277-1274-nd 2.54mm, 2 pos 1 connecting terminal block, bat, gnd, ts tblok3 phoenix contact 277-1273-nd 2.54mm, 3 pos 1 usb 2.0 receptacle, 5 pos usb usb-mini-b hirose electronic h2959ct-nd co. ltd. 2 capacitor, ceramic, 10f c1, c2 0805 murata 490-1717-1-nd 6.3v 10% x5r 0805 1 typical red led, super d1 1206led chicago miniature cmd15-21src/tr8 bright lamp 1 typical green led d2 1206led chicago miniature cmd15-21vgc/tr8 lamp 2 header, 3-pin j1, j2 header2mm-3 sullins 6821-0-0001-00-00-08-0 1 resistor, 10k 1/16w 5% r4 0603 panasonic/ecg p10kcfct-nd 0603 smd 3 resistor, 1.5k 1/16w r5, r6, r9 0603 panasonic/ecg p1.5khtr-nd 1% 0603 smd 1 resistor, 42.2k 1/16w r7 0603 panasonic/ecg p42.2khtr-nd 1% 0603 smd 1 resistor, 8.06k 1/16w r8 0603 panasonic/ecg p8.06khct-nd 1% 0603 smd 1 switch tact 6mm spst sw1 switch itt industries/ ckn9012-nd h = 5.0mm c&k div. 1 aat3688 usb port lithium- u1 tdfn33-12 analogictech aat3688iwp ion/polymer battery charger
ordering information package information all dimensions in millimeters. package marking 1 part number (tape and reel) 2 tdfn33-12 pkxyy aat3688iwp-4.2-t1 aat3688 usb port lithium-ion/polymer battery charger 3688.2006.10.1.5 23 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold . 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. 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.

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