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mp2674 li-ion battery charger protection circuit mp2674 rev. 0.9 www.monolithicpower.com 1 11/8/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. the future of analog ic technology description the mp2674 is a high-performance single cell li-ion/li-polymer battery charger protection circuit. by integrating high voltage input protection into the ic, the mp2674 can tolerate an input surge up to +30v. the device features input over voltage protection (ovp), battery over voltage protection (bovp) and over charge current protection (ocp). the device also provides fault indications to the system when any of the protection events happens. for guaranteed safe operation, the mp2674 monitors its own internal temperature and turns off the mosfet bridging vin and out when the die temperature exceeds 150 o c. the mp2674 is available in an 8-pin 2mmx2mm qfn package. features ? input surge up to 30v ? input over voltage protection in 1s. ? proprietary battery over-voltage protection ? programmable charge current protection limit value. ? temperature monitoring and protection ? fault indication ? 2mmx2mm qfn package applications ? cell phones ? mp3 players ? smart phones ? pda ? digital cameras ? desktop chargers ?mps? and ?the future of analog ic technology? are registered trademarks of monolithic power systems, inc. typical application mp2674 vin ilim gnd out vb flt c in r flt r ilim linear battery charger r vb + battery pack input c out
mp2674 ? charge system protection circuit mp2674 rev. 0.9 www.monolithicpower.com 2 11/8/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. ordering information part number* package top marking free air temperature (t a ) mp2674eg qfn8 (2mm x 2mm) 2q -20 c to +85 c * for tape & reel, add suffix ?z (e.g. mp2674eg?z): for rohs compliant packaging, add suffix ?lf (e.g. mp2674eg?lf?z). package reference top view vin gnd flt nc 1 2 3 4 out ilim vb gnd 8 7 6 5 absolute maxi mum ratings (1) v in to gnd.......................................-0.3v to 30v out and vb to gnd.........................-0.3v to 7v other pins (ilim, flt )...................-0.3v to 5.5v continuous power dissipation ...(t a = +25c) (2) ....................................................?....1.25w junction temperature ...............................150 c lead temperature (solder).......................260 c storage temperature............... -65 c to +150 c recommended operating conditions (3) supply voltage v in ..........................4.3v to 5.5v operating current range?????.0a to 1.5a operating junct. temp (t j )...... -20 c to +125 c thermal resistance (4) ja jc qfn8 (2mm x 2mm) .............. 100 ..... 55... c/w notes: 1) exceeding these ratings may damage the device. 2) the maximum allowable power dissipation is a function of the maximum junction temperature t j (max), the junction-to- ambient thermal resistance ja , and the ambient temperature t a . the maximum allowable continuous power dissipation at any ambient temperature is calculated by p d (max) = (t j (max)-t a )/ ja . exceeding the maximum allowable powe r dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. internal thermal shutdown circuitry protects the device from permanent damage. 3) the device is not guaranteed to function outside of its operating conditions. 4) measured on jesd51-7, 4-layer pcb.
mp2674 ? charge system protection circuit mp2674 rev. 0.9 www.monolithicpower.com 3 11/8/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. electrical characteristics v in = 5v, t a = +25 c, unless otherwise noted. parameter symbol condition min typ max units power-on reset rising vin threshold v por 2.35 2.43 2.50 v por hysteresis 110 mv when enabled 0.6 ma vin bias current i vin when disabled 25 a protection input over-voltage protection (ovp) v ovp 5.6 5.80 6.0 v input ovp hysteresis 50 mv input ovp falling threshold 5.45 v input ovp propagation delay 1 s over-current protection i ocp v vb = 3v, r ilim = 25k ? 0.78 0.90 1.10 a overcurrent protection blanking time bt ocp 170 s battery over-voltage protection threshold v bovp 4.29 4.37 4.475 v battery ovp threshold hysteresis 55 mv battery ovp falling threshold 4.225 v battery ovp blanking time bt bovp 180 s vb pin leakage current v vb = 4.34v 20 na over temperature protection rising threshold 150 c over temperature protection falling threshold 110 c logic f l t output logic low sink 5ma current 0.25 0.8 v f l t parasitic series resistor 60 ? f l t output logic high leakage current 1.5 a power mosfet on resistance r ds(on) measured at 200ma, 200 300 m ?
mp2674 ? charge system protection circuit mp2674 rev. 0.9 www.monolithicpower.com 4 11/8/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. pin functions 8-pin qfn name description 1 vin input power source. vi n can withstand 30v input. 2, 5 gnd system ground. 3 nc no connect. keep it floating. 4 flt open-drain logic output. this pin turns low when any protection event occurs. connect a pull-up resistor to vin pin. higher than 10k ? is recommended. 6 vb battery voltage monitoring input. connect this pin to the battery pack positive terminal via an isolation resistor. 7 ilim over-current protection threshold setting. connect a resistor between this pin and gnd to set the ocp threshold. 8 out output pin and input pi n of the protected charger.
mp2674 ? charge system protection circuit mp2674 rev. 0.9 www.monolithicpower.com 5 11/8/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. typical performanc e characteristics v in =5v, r ilim =24.9k ? , r vb =200k ? , r f l t =100k ? , t a =25 o c, unless otherwise noted. v in 2v/div. v out 2v/div. i out 200ma/div. i out 200ma/div. v in 5v/div. v in 2v/div. v bat 5v/div. v out 2v/div. flt 5v/div. v in v bat input ovp v in steps from 5v to 20v without load input ovp ramp up v in slowly without load input ovp start up ramp up v in slowly from 0v to 6.6v without load vb 2v/div. battery ovp no load, shut dwon permanently after 16 times ocp before start up shut dwon permanently after 16 times zoom in of ocp before start up flt 5v/div. v in 2v/div. v out 2v/div. flt 5v/div. i out 500ma/div. v in 2v/div. v out 2v/div. flt 5v/div. i out 500ma/div. v in 2v/div. v out 2v/div. flt 5v/div. i out 200ma/div. v in 2v/div. v out 2v/div. flt 5v/div. i out 200ma/div. v out 2v/div. flt 5v/div.
mp2674 ? charge system protection circuit mp2674 rev. 0.9 www.monolithicpower.com 6 11/8/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. typical performanc e characteristics (continued) v in =5v, r ilim =24.9k ? , r vb =200k ? , r f l t =100k ? , t a =25 o c, unless otherwise noted. supply current vs. v in limit current vs. r ilim 0 50 100 150 200 250 300 350 400 450 500 01234567 input voltage(v) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 50 100 150 200 250
mp2674 ? charge system protection circuit mp2674 rev. 0.9 www.monolithicpower.com 7 11/8/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. block diagram cp1 1.2v 0.8v r2 r1 input v in q4 r q1 q2 q3 ilim vb r vb out r ilim flt gnd -- + cp3 -- + cp2 -- + ea -- + logic fet driver por pre-reg ref linear battery charger + figure 1?function block diagram
mp2674 ? charge system protection circuit mp2674 rev. 0.9 www.monolithicpower.com 8 11/8/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. operation the mp2674 is designed to provide a redundant safety protection to a li-ion battery from failures of the charging system. the ic continuously monitors the input voltage, the battery voltage, and the charge current. when any of the above three parameters exceeds its limit, the ic turns off an internal n-channel mosfet to remove the power from the charging system. the threshold of charge current protection is user-programmable. additionally, the ic also monitors its own die temperature and turns off the n-channel mosfet if the temperature exceeds 150 c. together with the battery charging ic and the protection module in a battery pack, the charging system has triple-level protection from over-charging the li-ion battery and is two?fault tolerant. the mp2674 protects up to 30v input voltage. power up the mp2674 has a power-on reset (por) threshold of 2.43v with a built-in hysteresis of 110mv. when the input voltage is below the por threshold, the internal power fet is off. the ic resets itself and waits for approximately 10ms after the input voltage exceeds the por threshold, then, if the input voltage and battery voltage are safe, the ic begins to soft-start the internal power fet. the 10ms delay allows any transient at the input during a hot insertion of the power supply to settle down before the ic starts to operate. the soft-start slowly turns on the power fet to reduce the inrush current as well as the input voltage drop during the transition. input over-voltage protection (ovp) the input voltage is continuously monitored by the comparator cp1 in the block diagram (figure 1). the ovp threshold is set by a resistive divider consisting of r1 and r2 and an accurate reference generated by the ic itself. the protection threshold is set to 5.8v. when the input voltage exceeds the threshold, the cp1 outputs a logic signal to turn off the power fet within 1s to prevent the high input voltage from damaging the electronics in the handheld system. the hysteresis for the input ovp threshold is given in the electrical specification. when the input over-voltage condition is removed, the power fet is turned on again by running through the soft-start. because of the 10ms second delay before the soft-start, the output is never enabled if the input rises above the ovp threshold quickly. over-current protection (ocp) the current in the power fet is limited to prevent charging the battery with an excessive current. the current is sensed using the voltage drop across the power fet after the fet is turned on. the reference of the ocp is generated using a sensing fet q2, as shown in figure 1. the current in the sensing fet is forced to a value which can be programmed by an external resistor connected to the ilim pin. the size of the power fet q1 is 31,250 times the size of the sensing fet q2. therefore, when the current in the power fet is 31,250 times the current in the sensing fet, the drain voltage of the power fet falls below that of the sensing fet. the comparator cp2 then outputs a signal to turn off the power fet. the ocp threshold can be programmed using the following formula: l i m i l i m i l i m 0 . 8 v 2 5 0 0 0 i 3 1 2 5 0 r r =? = the ocp comparator cp2 has a built-in 170s delay to prevent false triggering by transient signals. when ocp happened, vo shuts down for about 40ms and take 10ms delay to soft start as the ocp condition is removed. the ocp function also has a 4-bit binary counter that accumulates during an ocp event. when the total count reaches 16, the power pfet is turned off permanently unless the input power is recycled. battery over-voltage protection (bovp) the battery voltage ovp threshold is internally set to 4.37v. the threshold has 55mv built-in hysteresis. the comparator cp3, as shown in figure 1, monitors the vb pin and issues an over-voltage signal to turn off the internal power fet when the battery voltage exceeds the battery ovp threshold. the comparator cp3 has a built-in 180s blanking time to prevent any transient voltage from triggering the ovp. if the ovp situation still exists after the blanking
mp2674 ? charge system protection circuit mp2674 rev. 0.9 www.monolithicpower.com 9 11/8/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. time, the power fet is turned off. there is an internal 4-bit binary counter monitoring the occurrence of the battery over-voltage event. if the battery over-voltage occurs 16 times, the power fet is turned off permanently. recycling the input power will reset the counter and restart the mp2674. the resistor between the vb pin and the battery, r vb , as shown in the typical applications circuit, is an important component. this resistor provides a current limit in case the vb pin is shorted to the input voltage under a failure mode. the vb pin leakage current under normal operation is negligible to allow a resistance of 200k ? to 1m ? being used. thermal protection the mp2674 monitors its own die temperature to prevent thermal failures. when the internal temperature reaches 150c, the internal n- channel power mosfet is turned off. the ic does not resume operation until the internal temperature drops below 110c. warning indication output the flt pin is an open-drain output that indicates a low signal when any of the four protection events happens. 1. input over voltage 2. battery over voltage 3. output over current 4. thermal protection to pull the f l t pin voltage low when fault, a recommended 10k ? to 200k ? resistor should be used as the pull up resistor.
mp2674 ? charge system protection circuit mp2674 rev. 0.9 www.monolithicpower.com 10 11/8/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. application information for safe and effective charging, some strict requirements have to be satisfied during charging li-ion batteries such as high precise power source for charging (4.2v50mv), the accuracy should be higher than 1%. for highly used capacity, the voltage of the battery should be charged to the value (4.2v) as possible as could. otherwise, the performance and the life of the battery suffers overcharge. additionally, the pre-charge for depleted batteries, charging voltage, charging current, as well as the temperature detection and protection, are required for linear battery chargers. the output of most mps linear chargers has a typical i-v curve and provides overcharge, input over voltage, over temperature protection. the function of the mp2674 is to add a redundant protection layer such that, under any fault condition, the charging system output does not exceed the i-v limits that the battery required. additionally, mp2674 provides full protection for these chargers whose protection function is not so complete especially those without input surge voltage sustain. mp2674 guarantees the safety of the charge system with its perfect 4 protection functions: ovp, bovp, ocp and otp the mp2674 is a simple device that requires few external components, in addition to the linear charger circuit as shown in the typical application circuit. the selection of mp2674?s external components is shown as follow, and the selection of the current limit resistor r ilim has been introduced in the over-current protection section. c in and c out selection the input capacitor (c in ) is for decoupling. higher value of c in reduces the voltage drop or the over shoot during transients. the ac adapter is inserted live (hot insertion) and sudden step down of the current in the power fet will cause the input voltage overshoot. during an input ovp, the fet is turned off in less than 1s and can lead to significant over shoot. higher capacitance of c in reduces this type of over shoot. however, the over shoot caused by a hot insertion is not very dependent on the decoupling capacitance value. usually, the input decoupling capacitor is recommended to use a dielectric ceramic capacitor with a value between 1f to 4.7f. the output of the mp2674 and the input of the charging circuit typically share one decoupling capacitor. the selection of that capacitor is mainly determined by the requirement of the charging circuit. when using the mp2602 family chargers, a 1f to 4.7uf ceramic capacitor is recommended. r vb selection r vb limits the current from the vb pin to the battery terminal in case the mp2674 fails. the recommended value is between 200k ? to 1m ? . with 200k ? resistance, during the failure operation, assuming the vb pin voltage is 30v and the battery voltage is 4.2v. the worst case the current flowing from the vb pin to the charger output is, (30v - 4.2v)/200k ? = 130a, such small current can be easily absorbed by the bias current of other components. increasing the r vb value reduces the worst case current, but at the same time increases the error for the 4.37v battery ovp threshold. as the typical vb pin leakage current is 20na, the error of the battery ovp threshold can be calculated as 4.37v+20naxr vb . with the 200k ? resistor, the worst-case additional error is 4mv and with a 1m ? resistor, the worst-case additional error is 20mv. .
mp2674 ? charge system protection circuit notice: the information in this document is subject to change wi thout notice. users should warra nt and guarantee that third party intellectual property rights are not infringed upon w hen integrating mps products into any application. mps will not assume any legal responsibility for any said applications. mp2674 rev. 0.9 www.monolithicpower.com 11 11/8/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. package information qfn8 (2mmx2mm) top view 1 8 54 bottom view 1.90 2.10 1.90 2.10 0.50 bsc 0.20 0.30 pin 1 id marking 0.50 0.25 recommended land pattern 1.90 note: 1) all dimensions are in millimeters. 2) exposed paddle size does not include mold flash. 3) lead coplanarity shall be 0.10 millimeter max. 4) jedec reference is mo-220, variation vccd. 5) drawing is not to scale. pin 1 id 0.10x45 o typ. 0.70 0.30 0.40 pin 1 id index area side view 0.00 0.05 0.80 1.00 0.20 ref 0.75 0.25 0.35 0.45

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