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lx2205 p roduction d ata s heet microsemi analog mixed signal group 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 1 copyright ? 2007 rev. 1.0a, 2007-03-02 www. microsemi . com 1a li-ion battery charger with power source management tm ? l l x x 2 2 2 2 0 0 5 5 descri pt i on the lx2205 is a complete single cell lithium ion or lithium polymer battery charger and power source manager. in addition to battery charging, power flow control is provided from up to three sources: a wall adapter, a standard usb power plug or the battery. the battery charge current and termination current are independently adjustable. the controller also includes status indicators which show when the controller is powered by an external adapter in addition to charge in progress, and charge completed. the usb input is current limited at two logically selectable levels (100ma and 500ma). when powered by a usb input, the battery is charged with the excess usb current that is not consumed by the system load. if the load exceeds the usb current limit, the battery will discharge to assist the usb power source to power the load. the controller can logically suspend the usb power to allow the system to operate from the battery without loading the usb. when a wall adapter is applied, it takes precedent over the usb power input and disables the usb input to prevent current flow from the adapter to the usb port. important: for the most current data, consult microsemi s website: http://www.microsemi.com patents pending. k ey feat u r es ? single cell li-ion battery charger ? power source management ? up to 1a charging current ? integrated power mosfet ? usb current compliance ? 25a quiescent current in discharge mode ? taper current termination ? protection features: o usb reverse current blocking o unsafe battery temp lockout o internal ic temperature limiter o usb current limiter appli c at i on s ? navigation devices ? portable usb devices ? multi-media player ? pda phones ? digital cameras produ ct h i gh li gh t lx2205 usb power wall adapter system load li-ion susp mdc dc ok ucl tfb bat usb sys suspend high/low ccp adapter present gnd shdn shutdown chg ctp cus done cmp charge/ discharge thermistor pack age order i n fo lq plastic mlp 4 x 4mm 16 pin t a ( c) rohs compliant / pb-free -40 to 85 LX2205ILQ note: available in tape & reel. append the lett ers tr to the part num ber. (i.e. LX2205ILQ-tr) downloaded from: http:///
lx2205 p roduction d ata s heet microsemi analog mixed signal group 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 2 copyright ? 2007 rev. 1.0a, 2007-03-02 www. microsemi . com 1a li-ion battery charger with power source management tm ? l l x x 2 2 2 2 0 0 5 5 absolu t e m ax i m u m rat i n gs supply voltages (mdc, sy s, usb) ................................................................ -0.3v to 7v battery voltage (bat ) ..................................................................................... -0.3v to 6v all other pins .............................................................................................-0.3v to v supply usb curre nt ............................................................................................................. 600ma bat discharge current ................................................................................................1.6a operating ambient temperature range (t a ) ..............................................-45 c to 125 c maximum operating junction temperature (t j ) ....................................................... 150 c storage temperat ure rang e.........................................................................-65 c to 150 c lead temperature (sol dering 10 s econds) ................................................................. 300 c package peak temp. for solder reflow (40 seconds maximum exposure) ... 260c (+0 -5) note: exceeding these ratings could cause damage to the device. all voltages are with respect to ground. currents are positive into, negative out of specified terminal . t h erm al dat a lq plastic 4 x 4mm 16-pin thermal resistance - junction to a mbient , ja 28 c/w* junction temperature calculation: t j = t a + (p d x ja ). *the ja numbers are guidelines for the thermal performan ce of the device/pc-board system. all of the above assume no ambient airflow. see lay out guidelines section for important details. pack age pi n ou t cmp bat sys usb mdc shdn susp ucl cus gnd ccp ctp dc ok chg done tfb 12 3 4 5678 9 10 11 12 13 14 15 16 connect bottom pad to gnd lq p ackage (top view) rohs / pb-free 100% matte tin pin finish fu n ct i on al pi n descri pt i on name pin description bat 2 battery connection - this pin is wired to the positive terminal of a single cell lithium ion/polymer battery. ccp 11 charge current programming pin - a resistor (r ccp ) is connected between this pin and gnd. the constant charging current is determined by the following relationship: r ccp = 50.648 x i ccl -1.0855 with r ccp in k ? and i ccp in amps. chg 14 charge indicator - this pin is a logic low level when the battery is being char ged, provided v sys is 4.4v. it is capable of driving the series combination of an led and resistor that is powered from the sys pin. cmp 1 compensation C connect a 0.1f capacitor from cmp to sys. ctp 12 charge termination programming pin C a resistor (r ctp ) is connected between this pin and gnd. the charge termination taper current is determined by the following relationship : r ctp =0.7354 x i term -1.0876 with r ctp in k ? and i term in amps. cus 9 usb current limit programming pin C a resistor (r cus ) is connected between this pin and gnd. the high level usb charge current is determined by the following relationship: i usb = 1050 / r cus . ok dc 13 main dc present C a low level on this logic output indicates that the main dc power source (typically the wall adapter) is applied. done 15 done indicator - this pin is a logic low level when the battery charge cycle is c omplete. it is capable of driving the series combination of an led and resistor that is powered from the sys pin. gnd 10 common ground C used as chip ground and as a reference for the battery retur n. downloaded from: http:///
lx2205 p roduction d ata s heet microsemi analog mixed signal group 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 3 copyright ? 2007 rev. 1.0a, 2007-03-02 www. microsemi . com 1a li-ion battery charger with power source management tm ? l l x x 2 2 2 2 0 0 5 5 fu n ct i on al pi n descri pt i on (con t i n u ed) name pin description mdc 5 main dc input C this input is a voltage monitoring input (and not a high current input). its purpose is to determine the presence of the main dc input to provide lockout for the usb power input. shdn 6 shutdown C pulling this pin high will disable the entire device including the batter y discharge path and place the device in a low power sleep mode. this pin has an internal pull-down. susp 7 suspend (usb) C pulling this pin high will prevent current from being drawn from the usb input pin. the rest of the chip functions are unaffected. this pin has an internal pull-down. sys 3 system power node C this pin provides power to user system. sys voltage provided will range from the battery voltage to the wall adapter and/or usb voltage. tfb 16 temperature feedback C charging is suspended when the tfb pin falls below 29% (typ) of v sys or rises above 74% (typ) of v sys . chg and done pins remain in their prior state during a tfb event. connecting the tfb pin to gnd disables the tfb function. usb 4 usb power input C usb compliant input. ucl 8 usb current limit C a high logic level will select the high usb current level determined by the programming of the cus pin. a low logic level will select a level that is 20% of the high usb current level. this pin has an internal pull-down. downloaded from: http:///
lx2205 p roduction d ata s heet microsemi analog mixed signal group 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 4 copyright ? 2007 rev. 1.0a, 2007-03-02 www. microsemi . com 1a li-ion battery charger with power source management tm ? l l x x 2 2 2 2 0 0 5 5 elect ri cal ch a ract eri st i cs unless otherwise specified, the following specificat ions apply over the operating temperature -40oc t a 85 oc and the following test conditions: v mdc = v usb = 5v, v sys =open, v susp = v shdn = low, v ucl = high, v bat = 3.9v, r ccp = 49.9k, r cus = 2.26k, r ctp = 20k lx2205 parameter symbol test conditions min typ max units ` main circuitry input voltage v supply usb or sys 4.35 6 v under voltage charging lockout v sys ( uvlo) rising input; v bat = 3.2v 3.55 3.7 3.95 v sys uvlo hysteresis guaranteed by design 140 mv usb uvlo v usb ( uvlo) rising input; v bat = 3.2v 4.25 4.30 4.34 v v bat = v cvl ; (battery charged), v sys = 5.0v 1.5 2.5 ma sys input supply current i sys shdn = high (shutdown mode), v sys = 5.0v 25 a v bat = v cvl ; (battery charged), , v mdc = 0v 2 ma susp = high (suspend mode), , v mdc = 0v 25 a shdn = high (shutdown mode), , v mdc = 0v 25 a usb input supply current i usb v mdc = 0v, v usb = 0v -1.5 -6 a v bat = v cvl ; (battery charged) 0.5 10 a v mdc =0v; susp = high (suspend mode) 25 50 a shdn = high (shutdown mode) 0.5 10 a battery drain current i bat v usb = 0v; v mdc = 0v; discharge with no load 25 50 a ` battery charger constant voltage charge voltage v cvl 4.16 4.2 4.24 v ctp bias voltage v ctp i bat > 100ma 1.30 v ccp bias voltage v ccp 1.25 v i ccl v sys = 5.0v 0.85 0.98 1.10 a v mdc =0v 465 ma v mdc =0v; i sys = 200ma (out of pin) 261 ma max battery charge current i bat v mdc =0v; ucl = low 92 ma conditioning current i cond v bat =2.5v, as a % of i ccl 2.5 5 7.5 % conditioning current threshold voltage v cct 2.55 2.7 2.9 v charge termination current i bat 40 50 60 ma top off charge droop threshold v drp expressed as a % of v cvl 96 97 98 % downloaded from: http:///
lx2205 p roduction d ata s heet microsemi analog mixed signal group 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 5 copyright ? 2007 rev. 1.0a, 2007-03-02 www. microsemi . com 1a li-ion battery charger with power source management tm ? l l x x 2 2 2 2 0 0 5 5 elect ri cal ch a ract eri st i cs (con t i n u ed) unless otherwise specified, the following specificat ions apply over the operating temperature -40oc t a 85 oc and the following test conditions: v mdc = v usb = 5v, v sys =open, v susp = v shdn = low, v ucl = high, v bat = 3.9v, r ccp = 49.9k, r cus = 2.26k, r ctp = 20k lx2205 parameter symbol test conditions min typ max units ` usb current limit usb low current limit i usb v mdc = 0v, ucl = low 85 93 100 ma usb high current limit i usb v mdc = 0v 425 463 500 ma reverse leakage current i leak v usb = 0v 2 10 a cus bias voltage v cus 2.5 v ` logic chg , done logic high output v oh v sys = 5.0v, i oh = -25ua 4.0 4.5 v chg , done logic low output v ol v sys = 5.0v, i ol = 5ma 0.4 v logic hi, 1.2 input logic : ucl, susp, shdn v log(in) logic lo 0.4 v logic hi, v log = 2v 0 2 4 input logic current : ucl, susp, shdn i log(in) logic lo, v log = 0v -2 0 2 a logic hi, 10k to 3.3v 3.2 output logic : ok dc v log(out) logic lo, i log = 100a 0.4 v ` thermal die protection battery charger thermal limiter t ctl 140 c ` bi-directional pass element control discharge switch on resistance r ds(on) i bat = -1a 275 m ? charging threshold v chg v sys C v bat 40 mv discharging threshold v dch v bat C v sys 40 mv pass element switch mode delay t sw chargeCtoCdischarge or dischargeCtoCcharge 2.5 s charging headroom v sys C v bat , i bat = 5ma 80 mv discharging headroom v bat C v sys , i bat = -20ma 80 mv ` mdc input ok dc voltage threshold v mdc rising 4.0 4.15 4.3 v hysteresis v mdc(hys) 35 mv mdc input current i mdc 15 35 a ` battery temperature monitor rising threshold ; as % of v sys 73 75 77 % cold temp fault threshold v tfb(cold) falling threshold; as % of v sys 71 73 75 % falling threshold; as % of v sys 27 28.5 30 % hot temp fault threshold v tfb(hot) rising threshold; as % of v sys 28 29.5 31 % tfb disable voltage threshold v tfb(dis) 70 100 150 mv downloaded from: http:///
lx2205 p roduction d ata s heet microsemi analog mixed signal group 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 6 copyright ? 2007 rev. 1.0a, 2007-03-02 www. microsemi . com 1a li-ion battery charger with power source management tm ? l l x x 2 2 2 2 0 0 5 5 ch arger con t rol flow d i agram start v sys > v bat yes discharge mode no v bat >60% condition charge mode no yes constant current charge mode temp < 140 reduce charge current i usb< i ucl no no v bat > v cv yes no i bat v bat , uvlo, susp, or shdn change state. switch off i ucl determined by the state of ucl. uvlo yes no shdn yes no dc ok no yes susp yes no dc ok yes i sys< i max no constant voltage charge mode temp < 140 reduce charge current i usb< i ucl no no dc ok yes i sys< i max no voltage monitoring mode (state). v bat <97% yes no usb suspend a tmp fault causes the charger to suspend charging. once the fault clears, charging resumes at the same point. yes yes yes yes yes yes no no downloaded from: http:///
lx2205 p roduction d ata s heet microsemi analog mixed signal group 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 7 copyright ? 2007 rev. 1.0a, 2007-03-02 www. microsemi . com 1a li-ion battery charger with power source management tm ? l l x x 2 2 2 2 0 0 5 5 si m pli fi ed block di agram input current limit wall adapter usb power system load battery charger ideal diode li-ion usb control susp mdc dc ok supervisor ucl battery temperature monitor tfb bat usb sys suspend high/low cus ctp ccp shdn shutdown ground gnd taper current setting charge current setting usb current setting battery temp sys cmp compensation chg done charge status indicators downloaded from: http:///
lx2205 p roduction d ata s heet microsemi analog mixed signal group 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 8 copyright ? 2007 rev. 1.0a, 2007-03-02 www. microsemi . com 1a li-ion battery charger with power source management tm ? l l x x 2 2 2 2 0 0 5 5 appli cat i on ci rcu i t s usb power 100k 88.7k 49.9k 12.4k lx2205 wall adapter system load li-ion susp mdc dc ok ucl tfb bat usb sys suspend high/low ccp adapter present gnd shdn shutdown chg ctp cus done cmp thermistor 9.09k 2.26k 2.4k 2.4k 0.1uf 10uf 10uf 10uf 10k 953k si5441bdc 1k figure 3 C ac adapter and usb supply (charge and discharge mo des) with 1a charging and 100ma termination current. in this application, the wall adapter vo ltage is not well regulated and can dip to less than 4.7v. for this case, a reverse blocking mosfet is used instead of the reverse blocking diode, shown in the produc t highlight. this extends the operating range of the lx2205 because the drop across the mosfet is minimal. it also increas es efficiency by eliminating the power loss of the schottky diode. 10k 8.87k 100k 1.24k lx2205 system load li-ion mdc dc ok tfb bat sys ccp gnd chg ctp cus done cmp thermistor 20k 2.26k 2.4k 2.4k 0.1uf 10uf 10uf q1 bss84 usb power susp ucl usb suspend high/low shdn shutdown 10uf 95.3k figure 4 C this application uses only a usb input with 500ma and 100ma maximum current limit levels and a 50ma termination current level. mosfet q1 turns off the tfb resistor string when not in charge mode to prevent battery drain; this is particularly helpful when using a small thermistor resistance value in the battery pack. downloaded from: http:///
lx2205 p roduction d ata s heet microsemi analog mixed signal group 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 9 copyright ? 2007 rev. 1.0a, 2007-03-02 www. microsemi . com 1a li-ion battery charger with power source management tm ? l l x x 2 2 2 2 0 0 5 5 t h eory of o perat i on b attery c harger g eneral d escription the lx2205 is designed to charge a single cell lithium ion or lithium polymer battery using two steps: a constant current step followed by a cons tant voltage step. the basic charger function uses the sys pin as an input and bat pin as the output. the lx2205 charger has a programmable maximum current (programmable by the resistor value between the ccp pin and gnd) which is the maximum charging current during the constant current mode of the charging profile. the charger will terminate constant voltage charging once the current drops below the taper current setting (programmable by the resistor value between ctp pin and gnd). two step charger profile: 5 43 2 1 800600 400 200 1000 time 0 chg voltage battery current battery voltage volts ma c onditioning c urrent c harge m ode a conditioning current is applied to a battery that is deeply discharged and has a terminal voltage less than 60% of the constant voltage level. the conditioning current is 5% of the ccp programmable constant current level. once the battery terminal voltage exceeds the 60% level, the full constant current level is applied (unless charging current is limited by one of the other charger control loops). c harge t ermination m ode to increase system battery life and avoid float charging, the lx2205 disconnects the ch arger once the battery has been fully charged. the charge termination state occurs at the end of constant voltage mode. the charge status indicators change state when charging is completed. states chg done charge in process on off charge completed off on input power removed off off using the taper current to te rminate the charge cycle is particularly advantageous in an isolated battery topology such as the lx2205, becaus e when an external power source is applied to the appliance with the appliance turned on, the power to the appliance and the power to the battery take separate paths. this separate path allows the battery charge current to be monitore d accurately. compared with charger controllers that rely on a fixed timeout period terminating by taper current allow for the shortest possible battery charge time. t op o ff c harge m ode once the charger has completed a charge cycle, if power remains applied, the lx2205 enters a voltage monitoring mode. in this mode the lx2205 monitors the battery terminal voltage and applies a top off charge if the battery voltage drops by more than 3% of v cvl . this feature is especially important for charging systems in equipment where usage is infrequent. usb c harge m ode and c urrent l imit the lx2205 is fully compliant with, and supports, the usb specifications C the low power peripheral (100ma) and high power peripheral (500ma). the ucl logic input selects the usb charge current level. the lx2205 senses the current flowing from the usb terminal to the sys terminal. the lx2205 will first try to reduce the combined usb load by scali ng back the battery charging current. once the charger has scaled back the charge current to zero, if the load demands more current than the usb bus can supply the v sys voltage will drop down to the battery voltage level and the battery will supply the additional current demand. this is illustrated in the following two charts. battery current w ith 500ma usb current limit -400 -300 -200 -100 0 100 200 300 400 500 600 0 200 400 600 800 system load current (ma) battery charge (discharge) usb limit battery downloaded from: http:///
lx2205 p roduction d ata s heet microsemi analog mixed signal group 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 10 copyright ? 2007 rev. 1.0a, 2007-03-02 www. microsemi . com 1a li-ion battery charger with power source management tm ? l l x x 2 2 2 2 0 0 5 5 t h eory of o perat i on battery current w ith 100m a usb current lim it -80 -60 -40 -20 0 20 40 60 80 100 120 0 40 80 120 160 system load current (ma) battery charge (discharge) usb limit battery r educed usb c harge t ime the isolated battery topology reduces charge time from the usb port when the appliance is turned on while also charging. because the system power rail can be a higher voltage than the battery voltage, the system will require less power from the usb source which leaves more power available to charge the battery quickly. for example, if the system draws 1w, and the us b input is 5v, the system draws 1w/5v = 200ma from the usb source; this leaves 300ma to charge the battery. in a topology where the load connects directly to the battery (as is done with conventional non-isolated linear chargers), if the average battery voltage is 3.7v, the system will draw 1w/3.7v = 270ma from the usb source, this leaves only 230ma to charge the battery. in this case the lx2205 will charge the battery 30% faster. usb s uspend when the susp pin is pulled high, less than 25 a is pulled from the usb port. the rest of the lx2205, however, continues to function normally. if an adapter is applied, the effect of susp is negligible. if the system is running off both usb and the battery and susp is logic high, the system load will be transferred 100% to the battery. shdn when shdn is logic high, the lx2205 is placed in a total shutdown mode; no curren t will flow between sys, usb and bat. quiescent current is 25 a during shutdown. chg and done are high impedance (off) in shdn mode. ucl the ucl pin is used to select the current limit level for the usb input. when the ucl pin is a logic high the maximum current level as determined by the cus resistor is selected; when the ucl pin is a logic low, the current limit is set to 20% of the maximum level. p ower or-ing (sys to bat and bat t o sys) when the power is removed from both mdc and usb, the battery current flows from bat to sys and thus provides power to the load without the need for any external switches or monitoring circuits. there is a circuit equivalent of an ideal diode (patent-pending bi-directional mosfet) in the lx2205 between the bat pin and sys pin. this ideal diode appears as a low impedance to high forward current and presents a high impedance to low discharge currents or potentially reverse charge currents. for small forward currents, the ideal diode regulates a small forward voltage. this small voltage allows the power sense circuitry to determine whether an input power source is present even if the current through the ideal diode is less than 1ma. this feature makes it virtually impossible to charge the batte ry (unregulated) in reverse through the ideal diode and also enables the battery to assist a current limited input power source without chattering even if only a fe w ma of battery current are required. downloaded from: http:///
lx2205 p roduction d ata s heet microsemi analog mixed signal group 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 11 copyright ? 2007 rev. 1.0a, 2007-03-02 www. microsemi . com 1a li-ion battery charger with power source management tm ? l l x x 2 2 2 2 0 0 5 5 t h eory of o perat i on / a p pli cat i on n ot e mdc, usb or-ing, uvlo a nd dc ok the power path from the usb input to the sys pin consists of a current limiter and a bidirectional switch (capable of blocking current in either direction). the usb input is switched off when at least one of the following conditions exists: 1. v usb < v usb uvlo 2. usb suspend pin is asserted. 3. v mdc > v usb 4. v mdc > v ok dc _threshold the mdc input is a monitoring input only, it is not a high current input. when th e voltage at sys exceeds the uvlo level, (typically 3.7v), the charger portion of the circuit is activated. the ok dc output is pulled low when both of the following conditions are true: 1. v mdc > v ok dc _threshold 2. v sys > v bat therefore when using a current limited wall adapter it is possible to charge the battery and not assert the ok dc output. p rotection f eatures conditioning current mode C if the battery terminal voltage is less than 2.7v, the battery charger will reduce the charge current to 5% of full s cale. this also protects the appliance from overheating by trying to drive the full charging current into a short circuited battery. under voltage lockout C the charger remains inactive until the under voltage lockout threshold is exceeded at the sys pin. thermal control loop C the power dissipation of the charger is limited by reducing the charge current with a control loop to prevent the die temperature from exceeded approximately 140 c. reverse current blocking C current will not flow out of the usb pin. shutdown mode C if the shdn pin is logic high, the charger enters a shutdown mode to prevent draining the battery. battery temperature lockout C if an unsafe temperature is sensed by the tfb input wi ndow comparator, battery charging is suspended. l ayout g uidelines ? it is important when la ying out the lx2205 to place 10f ceramic capacitors as close to the sys, usb and vbat ic terminals as possible to filter switching transients. ? it is important to provide a low thermal impedance path from the thermal pad on the bottom of the lx2205 package to the ground plane of the circuit board to maximize heat dissipation. generally this is accomplished by the use of multiple thermal vias. ? the compensation capacitor should be placed close to the cmp pin and connected with a short trace. c harge c urrent p rogramming the ccp, ctp, and cus programming pins are used to program the constant charge current, termination current, and usb current, respectively. these pins utilize regulated output voltages that produce a program current across an external resistor to gnd. the following tables are guidelines for selecting the proper resistor values: constant charge current (in ma) r ccp 50 1270k 100 604k 200 294k 300 187k 400 137k 500 107k 600 88.7k 700 75.0k 800 63.4k 900 56.2k 1000 49.9k* * r ccp minimum value termination current (in ma) r ctp 5 237k 10 105k 20 51.1k 40 24.9k 60 15.8k 80 11.8k 100 9.09k 120 7.50k 140 6.34k 160 5.49k 180 4.75k 200 4.22k downloaded from: http:///
lx2205 p roduction d ata s heet microsemi analog mixed signal group 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 12 copyright ? 2007 rev. 1.0a, 2007-03-02 www. microsemi . com 1a li-ion battery charger with power source management tm ? l l x x 2 2 2 2 0 0 5 5 appli cat i on n ot e b attery t emperature m onitor the lx2205 has an input to monitor the battery temperature during battery charging. the sys voltage must be used to bias this circuitry. during the occurrence of a tmp fault, the charge cycle is suspended; however the status indicators state remains unchanged. a typical lithium ion battery should only be charged within a temperature range of 0c to 60c. for this calculation example, a vi shay nths0402n01n1003j thermistor was used. this thermistor has the value of 327k ? at 0c, 100k ? at 25c and 24.9k ? at 60c. the thermistor must be biased with a thevenin voltage source and series resistance to achiev e the proper tmp thresholds. a fixed value resistor is added in series with the thermistor to prevent it from becoming too low impedance at high temperatures and causing the tmp input to default to off. using a value of r min that is ? the thermistor high temperature trip resistance valu e works well; therefore, for this example, set the value of r min to: 12.4k = 2 60 c t min r r = = . this has the effect of adding a fixed 12.4k to the thermistor resistance va lues so it becomes 339k ? at 0c, 112k ? at 25c and 37.3k ? at 60c. the equations for r th and v th are, using cold temperature fault threshold average of 74% and the hot temperature fault threshold average of 29% of v sys : () () ( ) 916 .0 74.0 29.0 74.0 29.0 60 0 60 0 = = ? ? = = = = = k r r r r v v c t c t c t c t sys th k r k r c t th 6.80 1 74.0 0 = ? ? ? ? ? ? ? = = to finish the design it is n ecessary to create the thevenin voltage and resistance using a voltage divider from the sys pin. the values of r1 and r2 can be calculated as: k k r r th 88 1 = = k r r r r r th th 958 1 1 2 = ? = actual standard 1% resistor values are: 953k and 88.7k. the final circuit for this example is: v sys 88.7k r ntc 12.4k tmp 953k the tmp voltages with this circuit are: temp ( c) rntc vtmp (% vsys) -20 971k 85% 0 327k 74% 25 100k 53% 60 24.9k 29% 80 12.6k 22% downloaded from: http:///
lx2205 p roduction d ata s heet microsemi analog mixed signal group 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 13 copyright ? 2007 rev. 1.0a, 2007-03-02 www. microsemi . com 1a li-ion battery charger with power source management tm ? l l x x 2 2 2 2 0 0 5 5 t y pi ca l c h a r gi n g cu rr en t v s ba t t ery v o l t age t y pi ca l c h ar gi n g cu r r en t v s v sy s 0 0.2 0.4 0.6 0.8 1 1.2 3.2 3.4 3.6 3.8 4 4.2 batt e r y v o lt ag e charge current (a) 0 0.2 0.4 0.6 0.8 1 1.2 4.2 4.6 5 5.4 5.8 sys voltage charge current (a) v bat = 3.9v t y pi c a l u s b cu r r en t l i m i t v s u s b v ol t ag e t y p i ca l v cv l di st ri b u t i on 0 50 100 150 200 250 300 350 400 450 500 44 . 555 . 56 input voltage usb current limit (ma) usb low usb hi 0 250 500 750 1000 1250 1500 4.16 4.17 4.18 4.19 4.20 4.21 4.22 4.23 4.24 v cvl typical distribution frequency v sy s = 5v t a = 25c ch arge t o di sch arge swi t ch ov er dc ok i bat v sys downloaded from: http:///
lx2205 p roduction d ata s heet microsemi analog mixed signal group 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 14 copyright ? 2007 rev. 1.0a, 2007-03-02 www. microsemi . com 1a li-ion battery charger with power source management tm ? l l x x 2 2 2 2 0 0 5 5 pack age di m en si on s lq 16-pin mlpq plastic (4x4mm ep / 114x114cu exposed pad) e d e b e2 d2 a a3 a1 l k m illimeters i nches dim min max min max a 0.80 1.00 0.031 0.039 a1 0 0.05 0 0.002 a3 0.18 0.30 0.007 0.012 b 0.23 0.38 0.009 0.015 d 4.00 bsc 0.157 bsc e 4.00 bsc 0.157 bsc e 0.65 bsc 0.026 bsc d2 2.55 2.80 0.100 0.110 e2 2.55 2.80 0.100 0.110 k 0.20 - 0.008 - l 0.30 0.50 0.012 0.020 note: 1. dimensions do not include mold flash or protrusions; these shall not exceed 0.155mm(.006) on any side. lead dimension shall not include solder coverage. production data C information contained in this document is proprietary to microsemi and is current as of publication date. this document may not be modified in any way without the express written consent of microsemi. product processing does not necessarily include testing of all parameters. microsemi reserves the right to change the configuration and performance of the product and to discontinue product at any time. downloaded from: http:///

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