preliminary datasheet LP28300 LP28300 ? 01 version 1.1 datasheet sep.-2010 www.lowpowersemi.com page 1 of 10 2a synchronous buck li-ion charger general description the LP28300 is a 2a li-ion battery charger intended for5v wall adapters. it utilizes a 1.5mhz synchronous buck converter topology to reduce power dissipation during charging. low power dissipation, an internal mosfet allow a physically small charger that can be embedded in a wide range of handheld applications. the LP28300 includes complete charge termination circuitry, automatic recharge and a 1% 4.2v float voltage. input short-circuit protection is included so no blocking diode is required. battery charge current, charge timeout and end-of-charge indication parameters are set with external components. additional features include shorted cell detection, temperature qualified charging and overvoltage protection. the LP28300 is available in a low profile (0.75mm) 10-lead(3mm 3mm) dfn package. order information LP28300 - f: pb-free package type qv: tdfn-10 applications ? portable media players ? cellular and smart mobile phone ? pda/dsc ? handheld battery-powered devices ? handheld computers ? charging docks and cradles features ? very low power dissipation ? 2a maximum charge current ? no external mosfets and blocking diode required ? constant-current/constant-voltage operation with thermal regulation to maximize charge rate without risk of overheating ? charges single cell li-ion batteries directly from usb port ? drainage charge current thermal regulation status outputs for led or system interface ? optional battery temperature monitoring before and during charge automatic sleep mode for low-power ? consumption available in 3mm 3mm tdfn-10 package ? rohs compliant and 100% lead (pb)-free typical application circuit marking information please see website.
preliminary datasheet LP28300 lp28 300 ? 0 1 version 1. 1 d atasheet sep . - 20 10 www.lowpowersemi.com page 2 of 10 functional pin description package type pin configurations tdfn- 10 vin 7 LP28300 vin 6 sns 3 11 8 1 gnd 10 9 4 2 batt en sw nc stat pgnd 5 ts pin description pin pin number description vin 1,7 positive supply voltage input. this pin connects to the power devices inside the chip. v in ranges from 4v to 5.5v for normal operation. operation down to the under-voltage lockout threshold is allowed with current limited wall adapters. decouple with a 10f or larger surface mounted ceramic capacitor. ts 2 ntc (negative temperature coefficient) thermistor input. with an external 10k ? ntc thermistor to ground, this pin senses the temperature of the battery pack and stops the charger when the temperature is out of range. to disable the temperature qualification function, ground the ntc pin. en 3 enable input pin. pulling the en pin high places the LP28300 into a low power state where the bat drain current drops to less than 3a and the supp ly current is reduced to less than 50a. for normal operation, pull the pin low. stat 4 open-drain charge status output. when the battery is charging, the stat pin is pulled low by an internal n-channel mosfet. when the charge cycle is completed, when the LP28300 detects an under voltage lockout condition, stat is forced high impedance. batt 5 battery charger output terminal. connect a 22f ceramic chip capacitor between bat and pgnd to keep the ripple voltage small. sns 6 internal sense resistor. connect to external inductor. current amplifier sense input. a sense resistor, r sense , must be connected between the sense and bat pins. the maximum charge current is equal to 100mv/r sense . nc 8 no connector. sw 9 switch node connection. this pin connects to the drains of the internal main and synchronous power mosfet switches. connect to external inductor. gnd 10 ground. pgnd 11 power ground pad.
preliminary datasheet LP28300 LP28300 ? 01 version 1.1 datasheet sep.-2010 www.lowpowersemi.com page 3 of 10 typical application circuits 1r 10 uf batt v in en stat sw sns batt ts gnd pgnd 10uf 10uh r sns 100mr 10k r ts 1uf 22uf 1cell 1 2 7 3 4 5 6 9 10 11 LP28300 v in 1r 10 uf v in en stat sw sns batt ts gnd pgnd 10uf 10uh r sns 100mr 10k r ts 1uf 22uf 1 2 7 3 4 5 6 9 10 11 LP28300 v in batt v in v in v in en stat sw sns batt ts gnd pgnd 10uf 10uh r sns2 r sns1 ? 100mr 10k r ts 1uf 22uf 1 2 7 3 4 5 6 9 10 11 LP28300 v in batt v in 1r 10 uf 200mr q1 ? usb charge ctrl h:usb charging, i set =500ma l:dc adapter charging, i set =1300ma
preliminary datasheet LP28300 lp28 300 ? 0 1 version 1. 1 d atasheet sep . - 20 10 www.lowpowersemi.com page 4 of 10 function block diagram absolute maximum ratings ? input voltage to gnd (vin) ----------------------------- ------------------------------------------------ 2.6v to 6.5v ? bat, i set , stat (vx) ---------------------------------------- -------------------------------- 0.3v to vin+0.3v ? bat short-circuit duration ----------------------- -------------------------------- --------------------- continuous ? bat pin current ------------------------------------ ------------------------------------- ----------------- 2500ma ? maximum junction temperature ---------------------- ------------------------------------- ----------------- 125c ? operating junction temperature range (tj) --- -------------------------------------------------- -40 to 85 c ? maximum soldering temperature (at leads, 10 sec) ----------------------------------- ------------------- 260 c thermal information ? maximum power dissipation (pd,ta<40 c ) ------------------------------- ------------------------------- 2w ? thermal resistance (ja) -------------------- ----------------------------------- --------------------------- 46 /w vin vin gnd en gnd sns sw batt stat
preliminary datasheet LP28300 lp28 300 ? 0 1 version 1. 1 d atasheet sep . - 20 10 www.lowpowersemi.com page 5 of 10 electrical characteristics (the specifications which apply over the fu ll operating temperature range, otherwise specifications are at ta = 25c. vcc = 5v, unless otherwise noted.) symbol parameter conditions min typ. max units v in adapter /usb voltage range 2.65 5 6 v i cc input supply current charge mode (note 4), r iset = 10k standby mode (charge terminated) 300 2000 ua shutdown mode (r iset not connected, 200 500 v cc < v bat , or v cc < v uv ) 25 50 v float regulated output (float) voltage 0c t a 85c, i bat = 40ma 4.158 4.2 4.242 v i bat bat pin current r sns = 100m ? , current mode 860 1000 1120 ma r sns = 68m ? , current mode 1300 1470 1620 standby mode, v bat = 4.2v shutdown mode (r iset not connected) sleep mode, v cc = 0v 0 -2.5 1 1 -6 2 2 ua i trikl trickle charge current v bat < v trikl , r sns = 100m ? (note 5) 80 100 120 ma v trikl trickle charge threshold voltage r sns = 100m ? , v bat rising (note 5) 2.8 2.9 3.0 v v trhys trickle charge hysteresis voltage r sns = 100m ? , (note 5) 60 80 110 mv v sns sns pin voltage r iset = 10k, current mode 88 100 116 mv i stat stat pin weak pull-down current v stat = 5v 8 20 35 ua v stat stat pin output low voltage i stat = 5ma 0.35 0.6 v v restat recharge battery threshold voltage v float - v restat 100 150 200 mv t lim junction temperature in constant temperature mode 120 c t ss soft-start time i bat = 0 to i bat =850v/r iset 100 us i sns i set pin pull-up current 3 ua
preliminary datasheet LP28300 lp28 300 ? 0 1 version 1. 1 d atasheet sep . - 20 10 www.lowpowersemi.com page 6 of 10 typical operating characteristics
preliminary datasheet LP28300 lp28 300 ? 0 1 version 1. 1 d atasheet sep . - 20 10 www.lowpowersemi.com page 7 of 10 operation the LP28300 is a constant current, constant voltage li-ion battery charger controller that uses a current mode pwm step-down (buck) switching architecture. the charge current is set by an external sense resistor (r sense ) across the sense and bat pins. the final battery float voltage is internally set to 4.2v per cell. for batteries like lithium-ion that require accurate final float voltage, the internal 2.4v reference, voltage amplifier and the resistor divider provide regulation with 1% accuracy. figure 1.typical charge profile a charge cycle begins when the voltage at the vcc pin rises above the uvlo level and is 250mv or more greater than the battery voltage. at the beginning of the charge cycle, if the battery voltage is less than the trickle charge threshold, 2.9v for the 4.2 version, the charger goes into trickle charge mode. the trickle charge current is internally set to 15% of the full-scale current. if the battery voltage stays low for 30 minutes, the battery is considered faulty and the charge cycle is terminated. when the battery voltage exceeds the trickle charge threshold, the charger goes into the full-scale constant current charge mode. in constant current mode, the charge current is set by the external sense resistor r sense and an internal 100mv reference; when the battery voltage approaches the programmed float voltage, the charge current will start to decrease. when the current drops to 25% of the full-scale charge current, an internal comparator turns off the internal pull-down n-channel mosfet at the stat pin, and connects a weak current source to ground to indicate a near end-of-charge condition. a 10k ? ntc (negative temperature coefficient) thermistor can be connected from the ntc pin to ground for battery temperature qualification. the charge cycle is suspended when the temperature is outside of the 0c to 50c window. shutdown the LP28300 can be shut down by pulling the comp pin to ground which pulls the gate pin high turning off the external p-channel mosfet. when the comp pin is released, the internal timer is reset and a new charge cycle starts. in shutdown, the output of the chrg pin is high impedance and the quiescent current remains at 1.5ma. removing the input power supply will put the charger into sleep mode. if the voltage at the vcc pin drops below (vbat + 250mv) or below the uvlo level, the LP28300 goes into a low current (icc = 10a) sleep mode, reducing the battery drain current. automatic recharge once the charge cycle is terminated, the LP28300 continuously monitors the voltage on the bat pin using 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 the need for periodic charge cycle initiations. stat output enters a strong pull-down state during recharge cycles. battery temperature detection a negative temperature coefficient (ntc) thermistor located close to the battery pack can be used to monitor battery temperature and will not allow charging unless the battery temperature is within an acceptable range. connect a 10k ? thermistor from the ts pin to ground. if the
preliminary datasheet LP28300 lp28 300 ? 0 1 version 1. 1 d atasheet sep . - 20 10 www.lowpowersemi.com page 8 of 10 temperature rises to 50c, the resistance of the ntc will be approximately 4.2k ? . with the 85a pull-up current source, the hot temperature voltage threshold is 360mv. for cold temperature, the voltage threshold is set at 2.4v which is equal to 0c (rts 28k ? ) with 85a of pull-up current. if the temperature is outside the window, the gate pin will be pulled up to vcc and the timer frozen while the output status at the stat pin remains the same. the charge cycle begins or resumes once the temperature is within the acceptable range. short the ts pin to ground to disable the temperature qualification feature. however the user may modify these thresholds by adding two external resistor. see figure 3. figure 2. temperature sensing configuration figure 3. temperature sensing thresholds input and output capacitors since the input capacitor is assumed to absorb all input switching ripple current in the converter, it must have an adequate ripple current rating. worst-case rms ripple current is approximately one-half of output charge current. actual capacitance value is not critical. solid tantalum capacitors have a high ripple current rating in a relatively small surface mount package, but caution must be used when tantalum capacitors are used for input bypass. high input surge currents can be created when the adapter is hot-plugged to the charger and solid tantalum capacitors have a known failure mechanism when subjected to very high turn-on surge currents. selecting the highest possible voltage rating on the capacitor will minimize problems. consult with the manufacturer before use. the selection of output capacitor c out is primarily determined by the esr required to minimize ripple voltage and load step transients. the output ripple ? v out is approximately bounded by: ????? since ? i l increases with input voltage, the output ripple is highest at maximum input voltage. typically, once the esr requirement is satisfied, the capacitance is adequate for filtering and has the necessary rms current rating. switching ripple current splits between the battery and the output capacitor depending on the esr of the output capacitor and the battery impedance. emi considerations usually make it desirable to minimize ripple current in the battery leads. ferrite beads or an inductor may be added to increase battery impedance at the 500khz switching frequency. if the esr of the output capacitor is 0.2 ? and the battery impedance is raised to 4 ? with a bead or inductor, only 5% of the current ripple will flow in the battery. inductor selection a high (1.5mhz) operating frequency was chosen for the buck switcher in order to minimize the size of the inductor. however, take care to use inductors with low core losses at this frequency. a good
preliminary datasheet LP28300 lp28 300 ? 0 1 version 1. 1 d atasheet sep . - 20 10 www.lowpowersemi.com page 9 of 10 choice is the ihlp-2525ah-01from vishay dale. to calculate the inductor ripple current: where v bat is the battery voltage, v in is the input voltage, l is the inductance and f is the pwm oscillator frequency(typically 1.5mhz). maximum inductor ripple current occurs at maximum vin and v bat = v in /2. peak inductor current will be: where i bat is the maximum battery charging current. when sizing the inductor make sure that the peak current will not exceed the saturation current of the inductors. also, ? i l should never exceed 0.4(i bat ) as this may interfere with proper operation of the output short-circuit protection comparator. 1.5h provides reasonable inductor ripple current in a typical application. with 1.5h and2a charge current: and layout considerations switch rise and fall times are kept under 5ns for maximum efficiency. to minimize radiation, the sw pin and input bypass capacitor leads (between v in and pgnd) should be kept as short as possible. a ground plane should be used under the switching circuitry to prevent inter plane coupling. the exposed pad must be connected to the ground plane for proper power dissipation. the other paths contain only dc and/or 1.5mhz tri-wave ripple current and are less critical. with the exception of the input and output filter capacitors(which should be connected to pgnd) all other components that return to ground should be connected to gnd.
preliminary datasheet LP28300 lp28 300 ? 0 1 version 1. 1 d atasheet sep . - 20 10 www.lowpowersemi.com page 10 of 10 packaging information
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