View EMC5754_1754036.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

preliminary EMC5754 elite micropower inc. elite micropower inc. reserves the right to make ch anges to improve reliability or manufacturability w ithout notice, and customers are advised to obtain the latest vers ion of relevant information prior to placing orders dsc5754_v2.1 june 10 th 2008 page 1 of 17 www.elitemicropower.com standalone linear li-ion battery charger with thermal regulation in sot-25 general description the EMC5754 is a complete linear charger for single cell lithium-ion batteries. with small sot-25 package an d few external components, EMC5754 is well suited for portable applications. in addition, the EMC5754 is specifically designed to work within usb power specifications. no external sense resistor and blocking diode are required. charging current can be programmed externally with a single resistor. the built-in the rmal regulation facilitates charging with maximum power without risk of overheating. the EMC5754 always preconditions the battery with 1/10 of the programmed charge current at the beginning of a charge cycle, until 40 s after it verifies that the battery can be fast-charged. the EMC5754 automatically terminates the charge cycle when the charge current drops to 1/10th the programmed value after the final float voltage is reached. the EMC5754 consumes zero reverse current from the battery at standby, shutdown and sleep modes. this feature reduces the charge and discharge cycles on the battery, further prolonging the battery life. t he EMC5754 can also be used as a ldo when battery is removed. other features include shutdown mode, charge current monitor, under voltage lockout, automatic recharge and status indicator. features programmable charge current up to 1a no mosfet, sense resistor or blocking diode required complete linear charger in sot-25 for single cell lithium-ion batteries typical zero reverse current from battery thermal regulation maximizes charge rate without risk of overheating charges single cell li-ion batteries directly from usb port act as a ldo when battery is removed preset 4.2v charge voltage with 1% accuracy automatic recharge charge status indicator c/10 charge termination 45 a shutdown supply current 2.9v trickle charge threshold soft-start limits inrush current rohs compliant and pb-free applications wireless handsets hand-held instruments portable information appliances bluetooth application charging docks and cradles typical application diagram typical performance characteristics i bat (ma) complete charge cycle (850mah battery) 580 ma charger ldo mode (battery removed) time (1000s/div) v bat (v) micro bridge technology co.,ltd.
preliminary EMC5754 elite micropower inc. elite micropower inc. reserves the right to make ch anges to improve reliability or manufacturability w ithout notice, and customers are advised to obtain the latest vers ion of relevant information prior to placing orders dsc5754_v2.1 june 10 th 2008 page 2 of 17 www.elitemicropower.com pin configuration sot-25(top view) order information EMC5754--00vf05grr 00 operation vf05 sot-25 package grr rohs package commercial grade temperature rating: -40 to 85c package in tape & reel marking & packing information package type marking product id transport media sot-25 EMC5754-00vf05grr 3k units tape & reel micro bridge technology co.,ltd.
preliminary EMC5754 elite micropower inc. elite micropower inc. reserves the right to make ch anges to improve reliability or manufacturability w ithout notice, and customers are advised to obtain the latest vers ion of relevant information prior to placing orders dsc5754_v2.1 june 10 th 2008 page 3 of 17 www.elitemicropower.com pin functions name sot-25 function chgb 1 open-drain charge status output. an internal n- channel mosfet connects chgb pin to ground when the battery is charging. after the char ge cycle is comp leted, the internal n-channel mosfet is replaced by a weak pull-down of approximately 24 a, indicating an ac present condition. when the EMC5754 detects an under volta ge lockout condition, chgb is forced high impedance. gnd 2 ground bat 3 charge current output and battery voltage feedback. this pin provides charge current to the battery a nd regulates the final float voltage to 4.2v. an in ternal precision resistor divider from this pin sets the float voltage which is disconnected in standby, shutdown and sleep modes. vin 4 positive input supply voltage. provides power to th e charger. vin c an range from 4.25v to 5.5v and should be bypassed with at least a 1 f capacitor. when vin drops to within 30mv above the bat pin voltage, the EMC5754 enters shutdown mode, dropping i bat to less than 1 a. prog 5 charge current program, charge current monitor and shutdown pin. the charge current is programmed by connecting a 1%resistor, r prog , to ground. when charging in constant- current mode, this pin servos to 1v. in all modes, the voltage on this pin can be used to measure the charge current using the follow ing formula: i bat =(v prog /r prog )*960 the prog pin can also be use d to shut down the charger. disconnecting the progr am resistor from ground allows a 0.4 a current to pull the prog pin high. when it reache s the 1.18v shutdown threshold voltage, the charger enter s shutdown mode. this pin is also clamped to approximately 2.4v. reconnecting r prog to ground will return the charger to normal operation. connecti ng the prog pin to a voltage between 0.2v and 0.4v can force EMC5754 into ldo mode. the prog pin must not be directly shorted to ground at any condition. micro bridge technology co.,ltd.
preliminary EMC5754 elite micropower inc. elite micropower inc. reserves the right to make ch anges to improve reliability or manufacturability w ithout notice, and customers are advised to obtain the latest vers ion of relevant information prior to placing orders dsc5754_v2.1 june 10 th 2008 page 4 of 17 www.elitemicropower.com absolute maximum ratings (notes 1, 2) vi n , v b a t , v c h g b -0. 3v t o 6 .0 v v prog (note 3) -0.3v to vin +0.3v bat short-circuit duration continu ous bat pin current 1a prog pin current 1ma storage temperature range -65c to160c junction temperature (tj) 150 c lead temperature (10 sec.) 260c thermal resistance ( ja ) sot-25 (note 5) operating ratings temperature range -40c to 85c supply voltage 4.25v to 5. 5v note: devices are esd sensitive. the leads should b e shorted together or the device placed in conducti ve foam during storage or handling to prevent electrostatic damage to the device. electrical characteristics unless otherwise specified, t a =25c and vin=5v. symbol parameter conditions min typ max units v in input voltage 4.25 5.5 v charge mode, r prog =10k (note 4) 150 260 330 a standby mode (charge terminated) 50 106 150 a i cc input supply current shutdown mode (r prog not connected, v in preliminary EMC5754 elite micropower inc. elite micropower inc. reserves the right to make ch anges to improve reliability or manufacturability w ithout notice, and customers are advised to obtain the latest vers ion of relevant information prior to placing orders dsc5754_v2.1 june 10 th 2008 page 5 of 17 www.elitemicropower.com v chgb chgb pin output low voltage i chgb =5ma 0.23 0.6 v v rechrg recharge battery threshold voltage v float -v rechrg 160 mv t ilm junction temperature in constan t temperature mode 120 o c r on power fet on resistance 550 m t ss soft-start time i bat =0 to i bat =960v/r prog 100 s t recharge recharge comparator filter time v bat high to low 0.75 2.4 4.5 ms t term termination comparator filter time i bat falling below i chg /10 0.4 1.1 2.5 ms i prog prog pin pull-up current 0.4 a note 1: absolute maximum ratings indicate limits beyond whi ch damage may occur. electrical specifications are not applicable when the device is operated outside of i ts rated operating conditions. note 2: all voltages are defined and measured with respect to the potential at the ground pin. note 3: can not exceed 6.0v. note 4: supply current includes prog pin current (approxima tely 100 a) but does not include any current delivered to the battery through the bat pin (approximately 9 6ma). note 5: 80 o c/w to150 o c/w, depending on pcb layout. functional block diagram micro bridge technology co.,ltd.
preliminary EMC5754 elite micropower inc. elite micropower inc. reserves the right to make ch anges to improve reliability or manufacturability w ithout notice, and customers are advised to obtain the latest vers ion of relevant information prior to placing orders dsc5754_v2.1 june 10 th 2008 page 6 of 17 www.elitemicropower.com state diagram typical applications usb/wall adapter power li-ion charger full featured single cell li-ion charger li-ion charger with external power dissipation basic li-ion charger with reverse polarity input pr otection micro bridge technology co.,ltd.
preliminary EMC5754 elite micropower inc. elite micropower inc. reserves the right to make ch anges to improve reliability or manufacturability w ithout notice, and customers are advised to obtain the latest vers ion of relevant information prior to placing orders dsc5754_v2.1 june 10 th 2008 page 7 of 17 www.elitemicropower.com turn off the led after charge is terminated *the formula for r1 is a v r m 35 1 1 < , where v1 is the turn-on threshold voltage of the led device. micro bridge technology co.,ltd.
preliminary EMC5754 elite micropower inc. elite micropower inc. reserves the right to make ch anges to improve reliability or manufacturability w ithout notice, and customers are advised to obtain the latest vers ion of relevant information prior to placing orders dsc5754_v2.1 june 10 th 2008 page 8 of 17 www.elitemicropower.com typical performance characteristics unless otherwise specified, v in = 5v, t a = 25c. v float (v) i bat (ma) regulated output (float) voltage vs temperature temperature ( o c) v bat (v) i bat (ma) charge current vs supply voltage charge current vs ambient temperature temperature ( o c) vin (v) regulated output (float) voltage vs supply voltage r prog =10k i bat (ma) v bat =4v v float (v) vin (v) v bat =4v thermal regulation thermal regulation chgb pin i-v curve (strong pull-down state) v bat =4v i chgb (ma) v chgb (v) charge current vs battery voltage micro bridge technology co.,ltd.
preliminary EMC5754 elite micropower inc. elite micropower inc. reserves the right to make ch anges to improve reliability or manufacturability w ithout notice, and customers are advised to obtain the latest vers ion of relevant information prior to placing orders dsc5754_v2.1 june 10 th 2008 page 9 of 17 www.elitemicropower.com typical performance characteristics unless otherwise specified, v in = 5v, t a = 25c. (continued) load transient (battery removed) v prog =0.2v, i bat =2ma~150ma 400 s/div v prog =0.2v, i bat =4ma v bat (50mv/div) vin (v), tr=tf=5 s 400 s/div line transient (battery removed) 5.5 4.5 v bat (50mv/div) i bat (100ma/div), tr=tf=20 s temperature ( o c) chgb pin current vs temperature (strong pull-down state) i chgb (ma) v bat =4v v chgb =1v chgb pin i-v curve (weak pull-down state) v bat =4.3v i chgb ( a) v chgb (v) temperature ( o c) chgb pin current vs temperature (weak pull-down state) i chgb ( a) v bat =4.3v v chgb =5v trickle charge current vs temperature i trickle (ma) temperature ( o c) v bat =2.5v r prog =2k r prog =10k micro bridge technology co.,ltd.
preliminary EMC5754 elite micropower inc. elite micropower inc. reserves the right to make ch anges to improve reliability or manufacturability w ithout notice, and customers are advised to obtain the latest vers ion of relevant information prior to placing orders dsc5754_v2.1 june 10 th 2008 page 10 of 17 www.elitemicropower.com typical performance characteristics unless otherwise specified, v in = 5v, t a = 25c. (continued) trickle charge current vs supply voltage v in (v) i trickle (ma) trickle charge threshold vs temperature v trickle (v) temperature ( o c) r prog =10k recharge voltage threshold vs temperature v rechrg (v) temperature ( o c) r prog =10k regulated output (float) voltage vs charge curren t r prog =1.25k v float (v) i bat (ma) v bat =2.5v r prog =2k r prog =10k prog pin voltage vs supply voltage (constant current mode) v in (v) v prog (v) v bat =4v r prog =10k prog pin voltage vs temperature temperature ( o c) v prog (v) v bat =4v r prog =10k micro bridge technology co.,ltd.
preliminary EMC5754 elite micropower inc. elite micropower inc. reserves the right to make ch anges to improve reliability or manufacturability w ithout notice, and customers are advised to obtain the latest vers ion of relevant information prior to placing orders dsc5754_v2.1 june 10 th 2008 page 11 of 17 www.elitemicropower.com typical performance characteristics unless otherwise specified, v in = 5v, t a = 25c. (continued) charge current vs prog pin voltage v prog (v) i bat (ma) prog pin pull-up current vs temperature and supply voltage i prog ( a) temperature ( o c) prog pin current vs prog pin voltage (pull-up current) i prog ( a) prog pin current vs prog pin voltage (clamp current) v bat =2.5v r prog =2k r prog =10k power fet on resistance vs temperature r ds(on) (m ) temperature ( o c) r prog =2k v in =4.2v v in =5.5v v bat =4.3v v prog =0v v prog (v) v bat =4.3v v bat =4.3v i prog ( a) v prog (v) v in =4.2v i bat =100ma r prog =2k micro bridge technology co.,ltd.
preliminary EMC5754 elite micropower inc. elite micropower inc. reserves the right to make ch anges to improve reliability or manufacturability w ithout notice, and customers are advised to obtain the latest vers ion of relevant information prior to placing orders dsc5754_v2.1 june 10 th 2008 page 12 of 17 www.elitemicropower.com operation the EMC5754 is a single cell lithium-ion battery ch arger using a constant-current/constant-voltage algorithm . it can deliver up to 1a of charge current (using a goo d thermal pcb layout) with a final float voltage accu racy of 1%. the EMC5754 includes an internal p-channel power mosfet and thermal regulation circuitry. no blocking diode or external current sense resistor i s required; thus, the basic charger circuit requires only two external components. furthermore, the EMC5754 i s capable of operating from a usb power source. normal charge cycle a charge cycle begins when the voltage at the vin p in rises above the uvlo threshold level and a 1% progr am resistor is connected from the prog pin to ground o r when a battery is connected to the charger output. if the bat pin is less than 2.9v, the charger enters t rickle charge mode. in this mode, the EMC5754 supplies approximately 1/10 the programmed charge current to bring the battery voltage up to a safe level for fu ll current charging. when the bat pin voltage rises ab ove 2.9v, the charger enters constant-current mode, whe re the programmed charge current is supplied to the battery. when the bat pin approaches the final floa t voltage (4.2v), the EMC5754 enters constant-voltage mode and the charge current begins to decrease. when the charge current drops to 1/10 of the programmed value, the charge cycle ends. programming charge current the charge current is programmed using a single res istor from the prog pin to ground. the battery charge current is 960 times the current out of the prog pi n. the program resistor and the charge current are calcula ted using the following equations: prog chg chg prog r v i i v r 960 , 960 = = the charge current out of the bat pin can be determined at any time by monitoring the prog pin voltage using the following equation: 960 = prog prog bat r v i charge termination a charge cycle is terminated when the charge curren t falls to 1/10th the programmed value after the fina l float voltage is reached. this condition is detected by u sing an internal, filtered comparator to monitor the pro g pin. when the prog pin voltage falls below 100mv fo r longer than t term (typically 1.1ms), charging is terminated. the charge current is latched off and t he EMC5754 enters standby mode, where the input supply current drops to 106 m a. (note: c/10 termination is disabled in trickle charging and thermal limiting m odes). the EMC5754 draws no current from the battery in standby mode . this feature reduces the charge and discharge cycles on the battery, further prolonging the battery life. any external source (v prog ) that holds the prog pin above 100mv will prevent the EMC5754 from terminating a charge cycle. however, if the prog pi n is controlled by external source, current sourcing fro m the bat pin can be infinity (until the internal power m osfet is burned out or the bat pin voltage is close to its f inal float voltage), and the formula for charge current is not valid anymore. therefore, controlling the prog pin by external source below 1.1v should be avoided when a battery is connected to bat pin. however, with no battery present, forcing v prog to 0.2v~0.4v enables EMC5754 to act as a ldo (ldo mode). in the ldo mode, load current at the bat pin is recommended to be below 150ma to avoid overheating. when charging, transient loads on the bat pin can cause the prog pin to fall below 100mv for short periods of time before the dc charge current has dropped to 1/10th the programmed value. the 1.1ms filter time (t term ) on the termination comparator ensures that transient loads of this nature do not result i n premature charge cycle termination. once the average charge current drops below 1/10th the programmed value, the EMC5754 terminates the charge cycle and ceases to provide any current through the bat pin. this is the standby mode, and all loads on the bat pin must be supplied by the batter y. in the standby mode, any signal below the manual shutdown threshold voltage (typically 1.18v) on the prog pin is transparent to EMC5754. the EMC5754 constantly monitors the bat pin voltage in standby mode. if this voltage drops below the 4.05v recharge threshold (v rechrg ), another charge cycle begins and current is once again supplied to the battery. to manually restart a charge cycle when in standby mode, the input voltage must be removed and reapplied, or the charger must be shut down and restarted using the prog pin. charge status indicator (chgb) the charge status output has three different states : strong pull-down (~10ma), weak pull-down (~24 m a) and high impedance. the strong pull-down state indicate s that the EMC5754 is in a charge cycle. once the charge cycle has terminated, the pin state is determined by undervoltage lockout conditions. a weak pull-down indicates that vin meets the uvlo conditions and the EMC5754 is ready to charge. high impedance indicates that the EMC5754 is in undervoltage lockout mode: either vin is less than 80mv above the bat pin voltage or insufficient volt age is applied to the vin pin. a microprocessor can be used to distinguish between these three statesthis meth od is discussed in the applications information sectio n. thermal limiting an internal thermal feedback loop reduces the programmed charge current if the die temperature attempts to rise above a preset value of approximat ely 120c. this feature protects the EMC5754 from exces sive temperature and allows the user to push the limits of the power handling capability of a given circuit board without risk of damaging the EMC5754. the charge current can be set according to typical (not worst- case) ambient temperature with the assurance that the micro bridge technology co.,ltd.
preliminary EMC5754 elite micropower inc. elite micropower inc. reserves the right to make ch anges to improve reliability or manufacturability w ithout notice, and customers are advised to obtain the latest vers ion of relevant information prior to placing orders dsc5754_v2.1 june 10 th 2008 page 13 of 17 www.elitemicropower.com charger will automatically reduce the current in worst-case conditions. sot power considerations are discussed further in the applications information s ection. undervoltage lockout (uvlo) an internal undervoltage lockout circuit monitors t he input voltage and keeps the charger in shutdown mod e until vin rises above the undervoltage lockout thre shold. the uvlo circuit has a built-in hysteresis of 200mv . furthermore, to protect against reverse current in the power mosfet, the uvlo circuit keeps the charger in shutdown mode if vin falls to within 30mv of the ba ttery voltage. if the uvlo comparator is tripped, the cha rger will not come out of shutdown mode until vin rises 80mv above the battery voltage. manual shutdown at any point in the charge cycle, the EMC5754 can b e put into shutdown mode by removing r prog thus floating the prog pin. this reduces the battery drain curren t to about to 0 a and the supply current to less than 45 a. a new charge cycle can be initiated by reconnecting t he program resistor. in manual shutdown, the chgb pin is in a weak pull-down state as long as vin is high enough to ex ceed the uvlo conditions. the chgb pin is in a high impedance state if the EMC5754 is in undervoltage lockout mode: either vin is within 80mv of the bat pin voltage or insufficient voltage is applied to the v in pin. automatic recharge once the charge cycle is terminated, the EMC5754 continuously monitors the voltage on the bat pin us ing a comparator with a 2ms filter time (t recharge ). a charge cycle restarts when the battery voltage falls below 4.05v (which corresponds to approximately 80% to 90 % battery capacity). this ensures that the battery is kept at or near a fully charged condition and eliminates th e need for periodic charge cycle initiations. chgb ou tput enters a strong pulldown state during recharge cycl es. =================================================== ========================================== application information stability considerations the constant-voltage mode feedback loop is stable without an output capacitor provided a battery is connected to the charger output. with no battery present, an output capacitor is recommended to reduce ripple voltage. when using high value, low e sr ceramic capacitors, it is recommended to add a 1 resistor in series with the capacitor. no series re sistor is needed if tantalum capacitors are used. in constant-current mode, the prog pin is in the feedback loop, not the battery. the constant-curren t mode stability is affected by the impedance at the prog pin. with no additional capacitance on the prog pin, the charger is stable with program resist or values as high as 100k. however, additional capacitance on this node reduces the maximum allowed program resistor. the pole frequency at the prog pin should be kept above 100khz. therefore, if the prog pin is loaded with a capacitance, c prog , the following equation can be used to calculate the maximum resistance value for r prog : ?;= ?;= 3 ? ? ? 5 10 2 1 average, rather than instantaneous, charge current may be of interest to the user. for example, if a switching power supply operating in low current mod e is connected in parallel with the battery, the average current being pulled out of the bat pin is typicall y of more interest than the instantaneous current pulses . in such a case, a simple rc filter can be used on the prog pin to measure the average battery current as shown in figure 1. a 10k resistor has been added between the prog pin and the filter capacitor to ensure stability. power dissipation the conditions that cause the EMC5754 to reduce charge current through thermal feedback can be approximated by considering the power dissipated in the ic. nearly all of this power dissipation is gen erated by the internal mosfetthis is calculated to be approximately: p d = (vin C v bat ) ? i bat where p d is the power dissipated, vin is the input supply voltage, v bat is the battery voltage and i bat is the charge current. the approximate ambient temperature at which the thermal feedback begins to protect the ic is: t a = 120 o c C p d ja t a = 120 o c C (vin C v bat ) ? i bat ? ja example: an EMC5754 operating from a 5v usb supply is programmed to supply 500ma full-scale current to a discharged li-ion battery with a voltage of 3.7v. assuming ja is 100 o c/w, the ambient temperature at which the EMC5754 will begin to reduce the charge current is approximately: t a = 120 o c C (5v C 3.7v) ? (500ma) ?100 o c/w figure 1. isolating capacitive load on prog pin and filtering micro bridge technology co.,ltd.
preliminary EMC5754 elite micropower inc. elite micropower inc. reserves the right to make ch anges to improve reliability or manufacturability w ithout notice, and customers are advised to obtain the latest vers ion of relevant information prior to placing orders dsc5754_v2.1 june 10 th 2008 page 14 of 17 www.elitemicropower.com t a = 120 o c C 0.65w ?100 o c/w = 120 o c C 65 o c t a = 55 o c the EMC5754 can be used above 55 o c ambient, but the charge current will be reduced from 500ma. the approximate current at a given ambient temperature can be approximated by: ja bat a o bat v vin t c i q - - = ) ( 120 using the previous example with an ambient temperature of 70 o c, the charge current will be reduced to approximately: ma i a c c w c c c i bat o o o o o bat 384 / 130 50 / 100 )7.3 5( 70 120 = = - - = moreover, when thermal feedback reduces the charge current, the voltage at the prog pin is also reduce d proportionally as discussed in the operation sectio n. it is important to remember that EMC5754 applications do not need to be designed for worst-case thermal conditions since the ic will automatically reduce p ower dissipation when the junction temperature reaches approximately 120 o c. thermal considerations because of the small size of the sot package, it is very important to use a good thermal pc board layout to maximize the available charge current. the thermal path for the heat generated by the ic is from the d ie to the copper lead frame, through the package leads, (especially the ground lead) to the pc board copper . the pc board copper is the heat sink. the footprint copper pads should be as wide as possible and expan d out to larger copper areas to spread and dissipate the heat to the surrounding ambient. feedthrough vias t o inner or backside copper layers are also useful in improving the overall thermal performance of the charger. other heat sources on the board, not relat ed to the charger, must also be considered when designing a pc board layout because they will affec t overall temperature rise and the maximum charge current. increasing thermal regulation current reducing the voltage drop across the internal mosfe t can significantly decrease the power dissipation in the ic. this has the effect of increasing the current d elivered to the battery during thermal regulation. one metho d is by dissipating some of the power through an externa l component, such as a resistor or diode. example: an EMC5754 operating from a 5v wall adapter is programmed to supply 1a full-scale curre nt to a discharged li-ion battery with a voltage of 3. 7v. assuming q ja is 100 o c/w, the approximate charge current at an ambient temperature of 25 o c is: ma w c v v c c i o o o bat 730 / 100 ) 7.3 5( 25 120 = - - = by dropping voltage across a resistor in series wit h a 5v wall adapter (shown in figure 2), the on-chip power dissipation can be decreased, thus increasing the thermally regulated charge current ja bat cc bat s o o bat v r i v c c i q - - - = ) ( 25 120 solving for ibat using the quadratic formula. ] ) 120 ( 4 ) ( ) [( 2 1 2 ja a o cc bat s bat s cc bat t c r v v v v r i q - - - - - = (note: large values of r cc will result in no solution for i bat . this indicates that the EMC5754 will not generate enough heat to require th ermal regulation.) using r cc = 0.25 ? , v s = 5v, v bat = 3.7v, t a = 25c and q ja = 100c/w we can calculate the thermally regulated charge current to be: i bat = 879.5ma while this application delivers more energy to the battery and reduces charge time in thermal mode, it may actually lengthen charge time in voltage mode i f vin becomes low enough to put the EMC5754 into dropout. this technique works best when r cc values are minimized to keep component size small and avoid dropout. remember to choose a resistor with adequat e power handling capability. vin bypass capacitor many types of capacitors can be used for input bypassing, however, caution must be exercised when using multilayer ceramic capacitors. because of the self-resonant and high q characteristics of some ty pes of ceramic capacitors, high voltage transients can be generated under some start-up conditions, such as connecting the charger input to a live power source . adding a 1.5 ? resistor in series ? with an x5r ceramic capacitor will minimize start-up voltage transients . charge current soft-start the EMC5754 includes a soft-start circuit to minimi ze the inrush current at the start of a charge cycle. when a charge cycle is initiated, the charge current ramps from zero to the full-scale current over a period of approximately 100 m s. this has the effect of minimizing the transient current load on the power supply duri ng start-up. figure 2. a circuit to maximize thermal mode charge current micro bridge technology co.,ltd.
preliminary EMC5754 elite micropower inc. elite micropower inc. reserves the right to make ch anges to improve reliability or manufacturability w ithout notice, and customers are advised to obtain the latest vers ion of relevant information prior to placing orders dsc5754_v2.1 june 10 th 2008 page 15 of 17 www.elitemicropower.com chgb status output pin the chgb pin can provide an indication that the inp ut voltage is greater than the undervoltage lockout threshold level. a weak pull-down current of approximately 24 a indicates that sufficient voltage is applied to vin to begin charging. when a discharged battery is connected to the charger, the constant current portion of the charge cycle begins and the chgb pin pulls to ground. the chgb pin can sink up to 10ma to drive an led that indicates that a charge c ycle is in progress. when the battery is nearing full charge, the charge r enters the constant-voltage portion of the charge c ycle and the charge current begins to drop. when the charge current drops below 1/10 of the programmed current, the charge cycle ends and the strong pull-down is replaced by the 24 a pull-down, indicating that the charge cycle has ended. if the input volta ge is removed or drops below the undervoltage lockout threshold, the chgb pin becomes high impedance. figure 3 shows that by using two different value pu ll-up resistors, a microprocessor can detect all three st ates from this pin. to detect when the EMC5754 is in charge mode, force the digital output pin (out) high and measure the voltage at the chgb pin. the internal n-channel mosfet will pull the pin voltage low even with the 2k pull-up resistor. once the charge cycle terminates, the n-channel mosfet is turned off and a 24 a current source is connected to the chgb pin. the in pin wil l then be pulled high by the 2k pull-up resistor. to determine if there is a weak pull-down current, the out pin should be forced to a high impedance state. the weak current source will pull the in pin low throug h the 800k resistor; if chgb is high impedance, the in pi n will be pulled high, indicating that the part is in a uv lo state. reverse polarity input voltage protection in some applications, protection from reverse polar ity voltage on vin is desired. if the supply voltage is high enough, a series blocking diode can be used. in oth er cases, where the voltage drop must be kept low a p-channel mosfet can be used (as shown in figure 4) . usb and wall adapter power the EMC5754 allows charging from both a wall adapte r and a usb port. figure 5 shows an example of how to combine wall adapter and usb power inputs. a p-channel mosfet, mp1, is used to prevent back conducting into the usb port when a wall adapter is present and a schottky diode, d1, is used to preven t usb power loss through the 1k pull-down resistor. typically a wall adapter can supply more current th an the 500ma-limited usb port. therefore, an n-channel mosfet, mn1, and an extra 10k program resistor are used to increase the charge current to 580ma when t he wall adapter is present. figure 5. combining wall adapter and usb power figure 4. low loss input reverse polarity protectio n figure 3. using a microprocessor to determine chgb s tate micro bridge technology co.,ltd.
preliminary EMC5754 elite micropower inc. elite micropower inc. reserves the right to make ch anges to improve reliability or manufacturability w ithout notice, and customers are advised to obtain the latest vers ion of relevant information prior to placing orders dsc5754_v2.1 june 10 th 2008 page 16 of 17 www.elitemicropower.com physical dimensions sot-25 o 2 symbpls min. nom. max. a 1.05 1.20 1.35 a1 0.05 0.10 0.15 a2 1.00 1.10 1.20 b 0.30 0.50 c 0.08 0.20 d 2.80 2.90 3.00 e 2.60 2.80 3.00 e1 1.50 1.60 1.70 e 0.95 bsc e1 1.90 bsc l 0.30 0.45 0.55 l1 0.60 ref ? 0 5 10 2 6 8 10 unit: mm micro bridge technology co.,ltd.
preliminary EMC5754 elite micropower inc. elite micropower inc. reserves the right to make ch anges to improve reliability or manufacturability w ithout notice, and customers are advised to obtain the latest vers ion of relevant information prior to placing orders dsc5754_v2.1 june 10 th 2008 page 17 of 17 www.elitemicropower.com ? copyright 2007 all rights reserved. no part of this document may be reproduced or dupli cated in any form or by any means without the prior permission of emp. the contents contained in this document are believe d to be accurate at the time of publication. emp as sumes no responsibility for any error in this document, and reserves the right to change the products or specif ication in this document without notice. the information contained herein is presented only as a guide or examples for the application of our p roducts. no responsibility is assumed by emp for any infringeme nt of patents, copyrights, or other intellectual pr operty rights of third parties which may result from its use. no license, either express, implied or otherwise, is granted un der any patents, copyrights or other intellectual property rights of emp or others. any semiconductor devices may have inherently a cer tain rate of failure. to minimize risks associated with customer's application, adequate design and operating safeguar ds against injury, damage, or loss from such failur e, should be provided by the customer when making application de signs. emp's products are not authorized for use in critic al applications such as, but not limited to, life s upport devices or system, where failure or abnormal operation may dir ectly affect human lives or cause physical injury o r property damage. if products described here are to be used f or such kinds of application, purchaser must do its own quality assurance testing appropriate to such applications. micro bridge technology co.,ltd.

▲Up To Search▲

Price & Availability of EMC5754

	To Download EMC5754 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .