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ws4502e 800ma, 4.2v li-ion battery charger descriptions the ws4502e is a complete constant-current / constant voltage linear charger for single cell lithium-ion batteries. no external sense resistor is needed, and no blocking diode is required due to the internal mosfet architecture. thermal feedback regulates the charge current to limit the die temperature during high power operation or high ambient temperature. the charge voltage is fixed at 4.2v, and the charge current can be programmed externally with a single resistor. the ws4502e automatically terminates the charge cycle when the charge current drops to 1/10 the programmed value after the final float voltage is reached. when the input supply (wall adapter or usb supply) is removed, the ws4502e automatically enters a low current state, dropping the battery drain current to less than 2ua. the ws4502e can be put into shutdown mode, reducing supply current to 50ua. the ws4502e is available in a small package with sot-23-5l. standard product is pb-free. features programmable charge current up to 800ma preset 4.2v charge voltage with 1% accuracy over-temperature protection under voltage lockout protection automatic recharge threshold 4.05v charge status output pin 2.9v trickle charge threshold soft-start limits inrush current applications wireless phone mp3/mp4 player bluetooth device sot-23-5l pin configuration (top view) ws45 yyww ws45 = dev ice code yy = year ww = week order information device package shipping ws4502e-5/tr sot-23-5l 3000/reel&tape 1 2 3 5 4 chgb gnd bat vcc prog 1 2 3 4 5 1 of 12 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
typical applications typical applications w/t led indicate typical applications w/t microprocessor detect pin descriptions block diagram pin number pin name function 1 chgb open-drain charge status output. when the battery is charging, the chgb pin is pulled low. when the charge cycle is completed or vcc is removed, the chgb is forced high impedance. 2 gnd ground 3 bat charge current output. provides charge current to the battery and regulates the final float voltage to 4.2v. 4 vcc power supply 5 prog charge current setting, charge current monitor and shutdown pin. the charging current is given by i bat = (1/r prog )*1000. the chip will be shutdown when prog pin floating vchg vcc prog chgb bat gnd 2k 1uf li-ion battery ws4502e 1 2 3 4 5 1k ws4502e 2 of 12 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
absolute maximum ratings thermal resistance characteristics note1: surface mounted on fr4 board usin g 1 in sq pad size, 2oz cu. note2: surface mounted on fr4 board using the minimum recommended pad size, 2oz cu. parameter symbol rating unit supply voltage vcc -0.3~7 v prog voltage v prog -0.3~vcc v bat voltage v bat -0.3~7 v chgb voltage v chgb -0.3~vcc v prog pin current i prog 800 ma power dissipation C note1 pd 0.5 w power dissipation C note2 pd 0.3 w junction temperature tj 150 o c operation temperature top -45~85 o c storage temperature tsg -65~125 o c lead temperature (soldering 10s) 260 o c symbol parameter max. unit r ja thermal resistance, junction to ambient C note1 125 o c/w r ja thermal resistance, junction to ambient C note2 415 o c/w ws4502e 3 of 12 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
electronics characteristics (vcc=5v, ta=25 o c, unless otherwise noted) symbol parameter condition min. typ. max. unit r prog =2k 300 2000 ua i splychrg charge mode supply current r prog =10k 300 2000 ua r prog =2k 450 500 550 ma i batchrg charge mode battery current r prog =10k 90 100 110 ma r prog =2k 0.90 1.00 1.10 v v progchrg prog pin voltage r prog =10k 0.90 1.00 1.10 v i splystby standby mode supply current 130 500 ua i batstby standby mode battery current -2.5 -6.0 ua i splyasd shutdown mode supply current 50 70 ua i batasd shutdown mode battery current 1 2 ua v float float voltage 4.183 4.2 4.273 v i trikl trickle charge current r prog =2k 20 50 70 ma v trikl trickle charge voltage threshold 2.8 2.9 3.0 v v trikl, hys trickle charge voltage hysteresis 60 100 120 mv v uvlo uvlo threshold 3.3 3.8 4.0 v v uvlo, hys uvlo hysteresis 150 200 300 mv v rechrg auto recharge battery voltage 4.0 4.05 4.1 v v chgb chgb pin output low voltage i chgb=5ma 0.25 0.6 v t lim junction temperature in constant temperature mode 165 o c r on power fet on resistance 600 m t ss soft-start time r prog =2k 100 us t rechrg recharge comparator filter time 0.75 2 4.5 ms t term termination comparator filter time 0.4 1 2.5 ms i prog prog pin pull-up current 3 ua ws4502e 4 of 12 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
typical characteristics (ta=25 o c, unless otherwise noted) prog pin vs. supply voltage (cc mode) charge current vs. prog pin voltage prog pin pull-up current vs. prog pin voltage prog pin vs. temperature prog pin pull-up current vs. temperature prog pin clamp current vs. prog pin voltage 4.0 4.5 5.0 5.5 6.0 6.5 7.0 1.000 1.005 1.010 1.015 1.020 1.025 1.030 v bat =4v r prog =10k v prog (v) v cc (v) -50 -25 0 25 50 75 100 0.985 0.990 0.995 1.000 1.005 1.010 1.015 v bat =4v r prog =10k v prog (v) temperature( o c) 0.00 0.25 0.50 0.75 1.00 1.25 0 100 200 300 400 500 600 i bat (ma) v prog (v) v cc =5v r prog =2k -50 -25 0 25 50 75 100 2.1 2.4 2.7 3.0 3.3 3.6 3.9 v cc =5v v bat =4.4v v prog =0v i prog (ua) temperature( o c) 2.0 2.1 2.2 2.3 2.4 2.5 2.6 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 v cc =5v v bat =4.4v i prog (ua) v prog (v) 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 -1000 -800 -600 -400 -200 0 i prog (ua) v prog (v) v cc =5v v bat =4.4v ws4502e 5 of 12 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
bat pin output float voltage vs. temperature bat pin output float voltage vs. charge current chgb pin current vs. temperature bat pin output float voltage vs. supply voltage chgb pin current vs. chgb pin voltage trickle charge current vs. temperature -50 -25 0 25 50 75 100 4.16 4.17 4.18 4.19 4.20 4.21 4.22 v cc =5v r prog =10k v float (v) temperature( o c) 4.0 4.5 5.0 5.5 6.0 6.5 7.0 4.185 4.190 4.195 4.200 4.205 4.210 4.215 v float (v) v cc (v) r prog =10k 0 100 200 300 400 500 600 700 4.10 4.12 4.14 4.16 4.18 4.20 4.22 4.24 4.26 v cc =5v v float (v) i bat (ma) 01234567 0 5 10 15 20 25 i chgb (ma) v chgb (v) v cc =5v v bat =4v -50 -25 0 25 50 75 100 5.0 7.5 10.0 12.5 15.0 17.5 20.0 v cc =5v v bat =4v v chrg =1v i chgb (ma) temperature( o c) -50 -25 0 25 50 75 100 0 10 20 30 40 50 r prog =10k r prog =2k i trickle (ma) temperature( o c) v cc =5v v bat =2.5v ws4502e 6 of 12 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
trickle charge current vs. supply voltage charge current vs. supply voltage charge current vs. temperature trickle charge threshold vs. temperature charge current vs. battery voltage recharge current threshold vs. temperature 4.04.55.05.56.06.57.0 0 10 20 30 40 50 r prog =10k r prog =2k i bat (ma) vcc (v) r prog =2k v bat =2.5v -50 -25 0 25 50 75 100 2.800 2.825 2.850 2.875 2.900 2.925 2.950 2.975 3.000 v cc =5v r prog =10k v trickle (v) temperature( o c) 4.0 4.5 5.0 5.5 6.0 6.5 7.0 0 100 200 300 400 500 600 r prog =2k r prog =10k i bat (ma) vcc (v) v bat =4v -50 -25 0 25 50 75 100 3.98 4.00 4.02 4.04 4.06 4.08 4.10 4.12 v cc =5v r prog =10k v rechrg (v) temperature( o c) 2.7 3.0 3.3 3.6 3.9 4.2 0 100 200 300 400 500 vcc=5v prog=2k i bat (ma) v bat (v) -50-25 0 255075100 0 100 200 300 400 500 600 r prog =2k r prog =10k i bat (ma) temperature( o c) v cc =5v v bat =4v ws4502e 7 of 12 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
power fet on resistance vs. temperature soft-start fully charge period waveform -50 -25 0 25 50 75 100 350 400 450 500 550 600 650 700 i bat =200ma r prog =2k r ds(on) (m ) temperature( o c) ws4502e 8 of 12 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
operation informations the ws4502e is a single cell lithium-ion battery charger using a constant-current / constant-voltage algorithm. it can deliver up to 0.8a of charge current (using a good thermal pcb layout) with a final float voltage accuracy of 1%. the ws4502e includes an in ternal p-channel power mosfet and thermal regulation circuitry. no blocking diode or external current sense resistor is required; thus, the basic charger circuit requires only two external components. furthermore, the ws4502e is capable of operating from a usb power source. normal charge cycle a charge cycle begins when the voltage at the vcc pin rises above the uvlo threshold level and a 1% program resistor is connected from the prog pin to ground or when a battery is connected to the charger output. if the bat pin is less than 2.9v, the charger enters trickle charge mode. in this mode, the ws4502e supplies approximately 1/10 the programmed charge current to bring the battery voltage up to a safe level for full current charging. when the bat pin voltage rises above 2.9v, the charger enters constant-current mode, where the programmed charge current is supplied to the battery. when the bat pin approaches the final float voltage, the ws4502e enters constant-voltage mode and the charge current begins to decrease. the charge cycle ends when the prog voltage is less than 100mv. programming charge current the charge current is programmed using a single resistor from the prog pin to ground. the battery charge current of constant current mode is 1000 times the current out of the prog pin. the program resistor and the charge current of constant current are calculated using the following equations: i chg = (1v/r prog )*1000 charge termination a charge cycle is terminated when the charge current falls to 1/10 of the programmed value after the final float voltage is reached. this condition is detected by using an internal, filtered comparator to monitor the prog pin. when the prog pin voltage falls below 100mv for longer than t term (typically 1ms), charging is terminated. the charge current is latched off and the ws4502e enters standby mode, where the input supply current drops to 130ua. (note: cc/10 termination is disabled in trickle charging mode and thermal limiting modes). 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 1/10 of the programmed value. the 1ms filter time (t term ) on the termination comparator ensures that transient loads of this nature do not result in premature charge cycle termination. once the average charge current drops below 1/10 of the programmed value, the ws4502e terminates the charge cycle and ceases to provide any current through the bat pin, the chip will be put into standby mode. in this state, all loads on the bat pin must be supplied by the battery. the ws4502e 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. the state diagram of a typical charge cycle is as below: ws4502e 9 of 12 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
charge status indicator (chgb) the charge status output indicator is an open drain circuit. the indicator has two different states: pull-down (~10ma), and high impedance. the pull-down state indicates that the ws4502e is in a charge cycle. high impedance indicates that the charge cycle is complete. the chgb also can be used to detect the charge states by a microprocessor with a pull-up resistor. shutdown mode at any point in the charge cycle, the ws4502e can be put into shutdown mode by removing rprog thus floating the prog pin. this reduces the battery drain current to less than 2ua and the supply current to less than 50ua. a new charge cycle can be initiated by reconnecting the program resistor. below is a recommend application. the ws4502e also be put into shutdown mode when vcc voltage down to uvlo threshold. in this state, the chgb pin is high impedance state. the chgb pin is also in a high impedance state if the charge cycle is completed. automatic recharge once the charge cycle is terminated, the ws4502e continuously monitors the voltage on the bat pin using a comparator with a 2ms filter time (t rechrg ). 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 the need for periodic charge cycle initiations. chgb output enters a pull-down state during recharge cycles. ws4502e 10 of 12 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
application informations 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. wh en using high value, low esr ceramic capacitors, it is recommended to add a 1 resistor in series with the capacitor. no series resistor is needed if tantalum capacitors are used. in constant-current mode, the prog pin is in the feedback loop, not the battery. the constant-current 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 resistor values as high as 10k. however, additional capacitance on this node reduces the maximum allowed program resistor thus it should be avoided. thermal limit an internal thermal feedback loop reduces the programmed charge current if the die temperature attempts to rise above a preset value of approximately 165c. this feature protects the ws4502e from excessive temperature and allows the user to push the limits of the power handling capability of a given circuit board without risk of damaging the ws4502e. the charge current can be set according to typical (not worst-case) ambient temperature with the assurance that the charger will automatically reduce the curre nt in worst-case conditions. power dissipation the conditions that cause the ws4502e to reduce charge current through thermal feed-back can be approximated by considering the power dissipated in the ic. nearly all of this power dissipation is generated by the internal mosfet. this is calculated to be approximately: p d = (vcc-v bat )*i bat it is important to remember that ws4502e applications do not be designed for worst-case thermal conditions since the ic will automatically reduce power dissipation when the junction temperature reaches approximately 165c (constant temperature mode). vcc bypass capacitor many types of capacitors can be used for input bypass, however, caution must be exercised when using multilayer ceramic capacitors. because of the self-resonant and high q characteristics of some types of ceramic capacitors, a 1uf/16v ceramic capacitor is recommended for this bypass capacitor. due to a high voltage transient will be generated under some start-up conditions, such as connecting the charger input to a live power source. charge current soft-start the ws4502e includes a soft-start circuit to minimize 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 50s. this has the effect of minimizing the transient current load on the power supply during start-up. ws4502e 11 of 12 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
package outline dimensions sot-23-5l dimensions in millimeters symbol min. max. a 1.050 1.250 a1 0.000 0.100 a2 1.050 1.150 b 0.300 0.500 c 0.100 0.200 d 2.820 3.020 e 1.500 1.700 e1 2.650 2.950 e 0.950(basic) e1 1.800 2.000 l 0.300 0.600 0 o 8 o ws4502e 12 of 12 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification

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