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MP2612 2a,24v input, 600khz 2-3 cells switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 1 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. the future of analog ic technology description the MP2612 is a monolithic switching charger for 2-3 cells series li-ion cells battery with a built-in internal power mosfet. it achieves up to 2a charge current with current mode control for fast loop response and easy compensation. the charge current can be programmed by sensing the current through an accurate sense resistor. MP2612 regulates the charge current and charge voltage using two control loops to realize high accuracy cc charge and cv charge. fault condition protection includes cycle- by- cycle current limiting and thermal shutdown. other safety features include battery temperature monitoring, charge status indication and programmable timer to finish the charging cycle. the MP2612 requires a minimum number of readily available standard external components. the MP2612 is available in 16-pin 4mm x 4mm qfn package. features ? charges 2-3 cells series li-ion battery packs ? wide operating input range ? up to 2 a programmable charging current ? 0.75% v batt accuracy ? 0.2 ? internal power mosfet switch ? up to 90% efficiency ? fixed 600khz frequency ? preconditioning for fully depleted batteries ? charging operation indicator ? input supply and battery fault indicator ? thermal shutdown ? cycle-by-cycle over current protection ? battery temperature monitor and protection applications ? distributed power systems ? chargers for 2-cell or 3-cell li-ion batteries ? pre-regulator for linear regulators ? smart phones ? net-book for mps green status, please visit mps website under quality assurance. ?mps? and ?the future of analog ic technology? are registered trademarks o f monolithic power systems, inc. typical application figure 1?standalone switching charger
MP2612 ? 2a, 24v input, 600khz 2-3cell switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 2 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. l rs1 vin vref33 vref25 cells chgok acok ntc en compv compi gnd tmr batt csp bst sw off on c2 22uf c3 1uf c4 2.2nf c5 2.2nf c6 0.1uf c7 0.1uf r1 r2 r3 10k 10k r4 2.5k r5 750 4.7uh 100m d1 c1 4.7uf r ntc v in 2-3 cells battery d2 9v to 24v (9v min for 2-cell) MP2612 rg1 rg2 vcc shdn gnd nc out2 out1 mp8110 rg2 rs2 20m rg1 m2 c8 m3 22uf v sys figure 2?switching charger with power path management (1) notes: 1) acok should be pulled up to vin in the power path management application.
MP2612 ? 2a, 24v input, 600khz 2-3cell switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 3 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. ordering information part number* package top marking free air temperature (t a ) MP2612er 4mm x 4mm qfn16 2612er -20 ? c to +85 ? c *for tape & reel, add suffix ?z (eg. MP2612er?z); for rohs compliant packaging, add suffix ?lf (eg. mp MP2612er?lf?z) package reference top view pin 1 id ntc acok chgok vref33 gnd csp batt compi 1 2 3 4 13 14 15 16 8 7 6 5 12 11 10 9 exposed pad on backside vref25 en cells compv vin sw bst tmr absolute maxi mum ratings (2) supply voltage v in ....................................... 26v v sw ........................................ -0.3v to v in + 0.3v v bst ...................................................... v sw + 6v v csp , v batt, ................................... -0.3v to +18v v acok , v chgok, .............................. -0.3v to +26v all other pins .................................. -0.3v to +6v continuous power dissipation (t a =+25 ? c) (3) ............................................................. 2.7w junction temperature ............................... 150 ? c lead temperature .................................... 260 ? c storage temperature ............... -65 ? c to +150 ? c recommended operating conditions (4) supply voltage v in .............................. 9v to 24v maximum junction temp. (t j ) ............. +125 ?? c thermal resistance (5) ja jc 4x4 qfn16 ............................. 46 ...... 10 ... ? c/w notes: 2) exceeding these ratings may damage the device. 3) 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 power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. internal thermal shutdown circuitry protects the device from permanent damage. 4) the device is not guaranteed to function outside of its operating conditions. 5) measured on jesd51-7 4-layer board.
MP2612 ? 2a, 24v input, 600khz 2-3cell switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 4 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. electrical characteristics (6) v in = 19v, t a = +25 ? c, cells=0v, unless otherwise noted. parameters symbol condition min typ max units terminal battery voltage v batt cells=0v 8.337 8.4 8.463 v cells= vref33 12.505 12.6 12.695 csp batt current i csp ,i batt charging disabled 1 a switch on resistance r ds ( on ) 0.2 ? switch leakage en = 4v, v sw = 0v 0 10 a peak current limit cc (6) 4.1 a trickle 2 a cc current i cc rs1=100m ? 1.8 2.0 2.2 a trickle charge current i trickle 10% i cc trickle charge voltage threshold 2.8 v/cell trickle charge hysteresis 350 mv termination current threshold i bf 5% 10% 15% i cc oscillator frequency f sw cells=0v, v batt =4.5v 600 khz fold-back frequency v batt =0v 190 khz maximum duty cycle 90 % maximum current sense voltage (csp to batt) v sense 170 200 230 mv minimum on time (6) t on cells=0v, v batt =5v 100 ns under voltage lockout threshold rising 3 3.2 3.4 v under voltage lockout threshold hysteresis 200 mv open-drain sink current v drain =0.3v 5 ma dead-battery indication stay at trickle mode c tmr =0.1 f 30 min termination delay time after i bf reached, c tmr =0.1 f 1 min recharge threshold at v batt v rechg 4.0 v/cell recharge hysteresis 100 mv ntc low temp rising threshold r ntc =ncp18xh103(0c) 73 %vref33 ntc high temp falling threshold r ntc =ncp18xh103(50c) 30 %vref33 vin min head-room (reverse blo cking) vin-vbatt 180 mv en input low voltage 0.4 v en input high voltage 1.8 v en input current en =4v 4 a en =0v 0.2
MP2612 ? 2a, 24v input, 600khz 2-3cell switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 5 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. electrical characteristics (continued) v in = 19v, t a = +25 ? c, cells=0v, unless otherwise noted. parameters symbol condition min typ max units supply current (shutdown) en =4v 0.16 ma en =4v, consider vref33 pin output current, r 3 =10k,r ntc =10k 0.32 ma supply current (quiescent) en =0v, cells=0v 2.0 ma thermal shutdown ( 6 ) 150 c vref25 output voltage 2.5 v vref33 output voltage 3.3 v vref33 load regulation i load =0 to 10ma 30 mv notes: 6) guaranteed by design.
MP2612 ? 2a, 24v input, 600khz 2-3cell switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 6 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. typical performanc e characteristics v in =19v, c1=4.7 f, c2=22 f, l=4.7 h, rs1=100m ? , real battery load, t a =25oc, unless otherwise noted. 7.5 7.6 7.7 7.8 7.9 8 8.1 8.2 8.3 8.4 8.5 0 20 40 60 80 100 120 t ime s (min) battery voltage(v) 0 0.5 1 1.5 2 2.5 battery current(a) i batt v batt 2 cells charge current vs. battery voltage cv load 3 cells charge current vs. battery voltage cv load 2 cells battery charge curve 3 cells battery charge curve 0 0.5 1 1.5 2 2.5 0246810 battery voltage(v) charge current(a) v in =12v v in =19v v in =24v 11 11.2 11.4 11.6 11.8 12 12.2 12.4 12.6 12.8 0 50 100 150 t ime s (min) battery voltage(v) battery current(a) 0 0.5 1 1.5 2 2.5 02468101214 battery voltage(v) charge current(a) 0 0.5 1 1.5 2 2.5 v batt i batt v in =19v v in =24v ntc control window 0 0.5 1 1.5 2 2.5 3 81216202428 v in (v) v ntc (v) low temp on high temp on high temp off low temp off 0 0.5 1 1.5 2 2.5 00.5 11.5 22.5 i chg (a) i sys (a)
MP2612 ? 2a, 24v input, 600khz 2-3cell switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 7 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. typical performanc e characteristics (continued) v in =19v, c1=4.7 f, c2=22 f, l=4.7 h, rs1=100m ? , real battery load, t a =25oc, unless otherwise noted. efficiency (%) efficiency vs. i chg 2 cells, v batt =8.4v efficiency vs. i chg 3 cells, v batt =12.6v efficiency vs. v in 2 cells, v batt =7.4v i chg (a) charge current vs. te mpe rature 2 cells, v batt =7.4v 1.2 1.4 1.6 1.8 2 2.2 -20 0 20 40 60 80 batt float voltage vs. te mpe rature 2 cells 8 8.1 8.2 8.3 8.4 8.5 -20 0 20 40 60 80 60 70 80 90 100 efficiency (%) efficiency (%) 60 70 80 90 100 0 0.4 0.8 1.2 1.6 2 i chg (a) v in (v) v in (v) 0 0.4 0.8 1.2 1.6 2 v in =12v v in =15v v in =19v v in =24v v in =24v v in =15v v in =19v 80 83 86 89 92 95 510152025 batt float voltage vs. v in 2 cells 8 8.1 8.2 8.3 8.4 8.5 813182328 v batt (v) v batt (v) v batt (v)
MP2612 ? 2a, 24v input, 600khz 2-3cell switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 8 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. typical performanc e characteristics (continued) v in =19v, c1=4.7 f, c2=22 f, l=4.7 h, rs1=100m ? , real battery load, t a =25oc, unless otherwise noted. v in 10v/div. v batt 5v/div. v sw 10v/div. i batt 200ma/div. v in 10v/div. v batt 5v/div. v sw 10v/div. i batt 2a/div. v in 10v/div. v batt 5v/div. v sw 10v/div. i batt 2a/div. v en 5v/div. v batt 5v/div. v sw 10v/div. i batt 2a/div. v en 5v/div. v batt 5v/div. v sw 10v/div. i batt 2a/div. v sw 10v/div. i batt 2a/div. v in 10v/div. v batt 5v/div. v sw 10v/div. i batt 500ma/div. v in 10v/div. v batt 5v/div. v sw 10v/div. i batt 1a/div. steady state waveform trickle charge 2 cells, v batt =5v steady state waveform cc charge 2 cells, v batt =7.4v steady state waveform cv charge 2 cells, v batt =8.4v power on waveform 2 cells, i chg =2a,v batt =8v power off waveform 2 cells, i chg =2a,v batt =8v en on waveform 2 cells, i chg =2a,v batt =8v en off waveform 2 cells, i chg =2a,v batt =8v v ntc 2v/div. v batt 5v/div. v tmr 500mv/div. i batt 2a/div. v in 10v/div. v batt 5v/div. ntc control , v batt =7.4v timer out 2 cells, v batt =7.4v, c tmr =1nf
MP2612 ? 2a, 24v input, 600khz 2-3cell switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 9 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. typical performanc e characteristics (continued) v in =19v, c1=4.7 f, c2=22 f, l=4.7 h, rs1=110m ? , rs2=20m ? , real battery load, t a =25oc, unless otherwise noted. v in 10v/div. v batt 5v/div. i sys 1a/div. i batt 1a/div. v in 10v/div. v sw 10v/div. i sys 500ma/div. i batt 1a/div. v in 10v/div. v batt 5v/div. v sys 5v/div. i batt 1a/div. v in 10v/div. v batt 5v/div. v sys 5v/div. i batt 1a/div. power path management current sharing 2 cells, i chg =2a, v batt =7.4v power path management steady state 2 cells, i chg =2a, v batt =8v, i sys =0.8a
MP2612 ? 2a, 24v input, 600khz 2-3cell switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 10 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. pin functions pin # name description 1 ntc thermistor input. connect a resistor from th is pin to the pin vref33 and the thermistor from this pin to ground. 2 acok valid input supply indicator. a logic low on this pin indicates the presence of a valid input supply. 3 chgok charging completion indicator. a logic low indicates charging operation. the pin will become an open drain once the charging is complete. 4 vref33 internal linear regulator 3.3v reference output. bypass to gnd with a 1 f ceramic capacitor. 5 vref25 internal linear 2.5v referenc e circuit. please keep this pin floating. 6 en on/off control input. 7 cells command input for the number of li-ion cells. connect this pin to vref33 for 3-cell operation or ground the pin for 2-cell operation. do not leave this pin float. 8 compv v-loop compensation. decouple th is pin with a capacitor and a resistor. 9 compi i-loop compensation. decouple this pin with a capacitor and a resistor. 10 batt positive battery terminal. 11 csp battery current sense positive input. connect a resistor r sen between csp and batt. the full charge current is: ?? ?? m ? rs1 200mv a i chg ? . 12 gnd ground. this pin is the voltage reference for the regulated output voltage. for this reason care must be taken in its layout. this node should be placed outside of the switching diode (d2) to the input ground path to prevent swit ching current spikes from inducing voltage noise into the part. 13 tmr set time constant. 0.1ua current ch arges and discharges the external cap. 14 bst bootstrap. this capacitor is needed to driv e the power switch?s gate above the supply voltage. it is connected between sw and bs pins to form a floating supply across the power switch driver. 15 sw switch output. 16 in supply voltage. the MP2612 operates from a 9v to 24v unregulated input to charge 2~3 cell li-ion battery. capacitor is needed to prevent large voltage spikes from appearing at the input.
MP2612 ? 2a, 24v input, 600khz 2-3cell switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 11 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. block diagram figure 3?function block diagram
MP2612 ? 2a, 24v input, 600khz 2-3cell switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 12 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. operation the MP2612 is a peak current mode controlled switching charger for use with li-ion batteries. figure 3 shows the block diagram. at the beginning of a cycle, m1 is off. the comp voltage is higher than the current sense result from amplifier a1?s output and the pwm comparator?s output is low. the rising edge of the 600 khz clk signal sets the rs flip-flop. its output turns on m1 thus connecting the sw pin and inductor to the input supply. the increasing inductor current is sensed and amplified by the current sense amplifier a1. ramp compensation is summed to the output of a1 and compared to comp by the pwm comparator. when the sum of a1?s output and the slope compensation signal exceeds the comp voltage, the rs flip-flop is reset and m1 is turned off. the external switching diode d2 then conducts the inductor current. if the sum of a1?s output and the slope compensation signal does not exceed the comp voltage, then the falling edge of the clk resets the flip-flop. the MP2612 have two internal linear regulators power internal circuit, vref33 and vref25. the output of 3.3v reference voltage can also power external circuitry as long as the maximum current (50ma) is not exceeded. a 1 f bypass capacitor is required from vref33 to gnd to ensure stability. the output of 2.5v reference voltage can not carry any load. in typical application, vref25 should be float and no capacitor is required. it can only connect to a capacitor which is smaller than 100pf. charge cycle (mode change: trickle ? cc ? cv) the battery current is sensed via rs1 (figure 3) and amplified by a2. the charge will start in ?trickle charging mode? (10% of the r sen programmed current i cc ) until the battery voltage reaches 2.8v/cell. if the charge stays in the ?trickle charging mode? till ?timer out? condition is triggered, the charge is terminated. otherwise, the output of a2 is then regulated to the level set by rs1 . the charger is operating at ?constant current charging mode.? the duty cycle of the switcher is determined by the compi voltage that is regulated by the amplifier gmi. when the battery voltage reaches the ?constant voltage mode? threshold, the amplifier gmv will regulate the comp pin, and then the duty cycle. the charger will then operate in ?constant voltage mode.? automatic recharge a programmable time delay after the battery charging current drops below the termination threshold, the charger will cease charging and the chgok pin becomes an open drain. if for some reason, the battery voltage is lowered to 4.0v/cell, recharge will automatically kick in. 0.1uf c 1min delay n terminatio tmr ? ? charger status indication MP2612 has two open-drain status outputs: chgok and acok . the acok pin pulls low when an input voltage is greater than battery voltage 300mv and over the under voltage lockout threshold. chgok is used to indicate the status of the charge cycle. table 1 describes the status of the charge cycle based on the chgok and acok outputs. table 1 D charging status indication acok chgok charger status low low in charging low high end of charge, high high vinMP2612 uses internal timer to terminate the charge if the timer times out. the timer duration is programmed by an external capacitor at the tmr pin. the trickle mode charge time is:
MP2612 ? 2a, 24v input, 600khz 2-3cell switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 13 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. 0.1uf c 30mins t tmr tickle_tmr ? ? the total charge time is: 0.1uf c 3hours t tmr total_tmr ? ? negative thermal coefficient (ntc) thermistor the MP2612 has a built-in ntc resistance window comparator, which allows MP2612 to sense the battery temperature via the thermistor packed internally in the battery pack to ensure a safe operating environment of the battery. a resistor with appropriate value should be connected from vref33 to ntc pin and the thermistor is connected from ntc pin to gnd. the voltage on ntc pin is determined by the resistor divider whose divide ratio depends on the battery temperature. when the voltage of pin ntc falls out of ntc window range, MP2612 will stop the charging. the charger will restart if the temperature goes back into ntc window range. power path management using mp8110 together with MP2612 can implement a switching charger circuit with power path management function, which realizes the current sharing of the charger and system load (figure 2). in another word, mp8110 senses the system current and feeds back to MP2612 and MP2612 reduces charge current according to the increase of the system current. however, after the charge current decrease to 0, the system current can only be limited by the adapter. the system current is satisfied first and always. it chooses the adapter as its power source when the adapter plugs in, and the battery is the backup power source when the adapter is removed. figure 4 to 8 shows the charge profile, operation waveform and flow chart, respectively.
MP2612 ? 2a, 24v input, 600khz 2-3cell switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 14 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. charge profile and power pa th management function figure 4?li-ion battery charge profile figure 5 ? power path management function- current sharing
MP2612 ? 2a, 24v input, 600khz 2-3cell switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 15 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. operation flow chart figure 6? normal charging operation flow chart
MP2612 ? 2a, 24v input, 600khz 2-3cell switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 16 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. operation flow chart ( continued ) figure 7? power path management operation flow chart
MP2612 ? 2a, 24v input, 600khz 2-3cell switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 17 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. operation flow chart (continued) charge mode? v batt >v batt_tc v batt >v batt_full battery full? i chg =150 o c? tj<=130 o c? charge current thermal shutdown, acok& chgok are high fault protection yes charger recovery, return to normal operation yes no yes no yes no charge termination, acok& chgok are high yes ntc fault? no timer out ? no figure 8? fault protection flow chart
MP2612 ? 2a, 24v input, 600khz 2-3cell switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 18 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. application information setting the charge current 1. standalone switching charger the charge current of MP2612 is set by the sense resistor rs1 (figure1). the charge current programmable formula is as following: ?? ?? m ? rs1 200mv a i chg ? (1) 2. switching charger with power path management when MP2612 is applied together with mp8110, the charge current setting should be calibrated (figure2). figure 8 shows mp8110 sensing the system current and feeding back to the MP2612. figure 8? system current sensing circuit the gain of mp8110 is set as: rg1 rgs1 gain ? (2) the voltage of out1 pin, v out1 can be calculated from: rg1 rgs1 rs2 i gain rs2 i v sys sys out1 ? ? ? ? ? ? (3) when the system current increased i sys , to satisfy the charge current decreased i sys accordingly, the relationship should be: rg1 rs1 rgs1 rs2 i rs1 v i sys out1 bat ? ? ? ? ? (4) because i sys = i batt , we can get: rg1 rgs1 rs2 rs1 ? (5) r gs1/2 causes charge current sense error as it changes the sense gain of a2, which can be calculated from: ?? ?? ?? k ? rgs k ? 2 k ? 12.3 g a2 ? ? (6) the charge current is set as: ?? ?? m ? rs1 g 1230 a i a2 chg ? ? (7) then the influence of r gs1 to the charge current is: ?? ?? ?? m ? rs1 10 ? rgs 2000 a i chg ? ? ? (8) to decrease the power loss of the sensing circuit, choose rs2 as small as possible, 20m is recommended. too small r g1 results in too big current sense error of mp8110, 50 ? is at least. substitute these two values into equation (5), then the calibrated charge current set formula in power path application is got from equation (8): ?? ?? ?? m ? rs1 10 m ? rs1 2.5 2000 a i chg ? ? ? ? (9) following table is the calculated rs1 and r gs1 value for setting different charge current. table2?i chg set in power path application i chg (a) r gs ( ? ) rs1(m ? ) 2 280 110 1.5 402 160 1 665 260 0.8 909 360 0.5 2k 800 if choose different rs2 and r g1 , re-calculated from equation (5) and equation (8), then get the different equation (9) and the table.
MP2612 ? 2a, 24v input, 600khz 2-3cell switching li-ion battery charger MP2612 rev. 1.0 www.monolithicpower.com 19 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. also, any relationship between i sys and i batt can be realized by re-calculate equation (4),(5) and (8). selecting the inductor a 1h to 10h inductor is recommended for most applications. the inductance value can be derived from the following equation. out in out in l osc v(vv) l vif ?? ? ?? ? (10) where i l is the inductor ripple current. v out is the 2/3 cell battery voltage. choose inductor current to be approximately 30% if the maximum charge current, 2a. the maximum inductor peak current is: ? ?? l l(max) chg i ii 2 (11) under light load conditions below 100ma, larger inductance is recommended for improved efficiency. for optimized efficiency, the inductor dc resistance is recommended to be less than 200m ? . ntc function as figure 9 shows, the low temperature threshold and high temperature threshold are preset internally via a resistive divider, which are 73%vref33 and 30%vref33. for a given ntc thermistor, we can select appropriate r3 and r6 to set the ntc window. in detail, for the thermistor (ncp18xh103) noted in above electrical characteristic, at 0oc, r ntc_cold = 27.445k; at 50oc, r ntc_hot = 4.1601k. assume that the ntc window is between 0oc and 50oc, the following equations could be derived: 73% vref33 v r6//r r3 r6//r th_low ntc_cold ntc_cold ? ? ? (12) 30% vref33 v r6//r r3 r6//r th_high ntc_hot ntc_hot ? ? ? (13) according to equation (12) and equation (13), we can find that r3 = 9.63k and r6 = 505k. to be simple in project, making r3=10k and r6 no connect will approximately meet the specification. ntc vref33 low temp threshold high temp threshold r ntc r3 r6 v th_low v th_high figure 9? ntc function block selecting the input capacitor the input capacitor reduces the surge current drawn from the input and also the switching noise from the device. the input capacitor impedance at the switching frequency should be less than the input source impedance to prevent high frequency switching current passing to the input. ceramic capacitors with x5r or x7r dielectrics are highly recommended because of their low esr and small temperature coefficients. for most applications, a 4.7f capacitor is sufficient. selecting the output capacitor the output capacitor keeps output voltage ripple small and ensures regulation loop stability. the output capacitor impedance should be low at the switching frequency. ceramic capacitors with x5r or x7r dielectrics are recommended. pc board layout the high frequency and high current paths (gnd, in and sw) should be placed to the device with short, direct and wide traces. the input capacitor needs to be as close as possible to the in and gnd pins. the external feedback resistors should be placed next to the fb pin. keep the switching node sw short and away from the feedback network.
MP2612 ? 2a, 24v input, 600khz switching li-ion battery charger mps confidential and proprietary information ? internal use only notice: the information in this document is subject to change wi thout notice. please contact m ps for current specifications. users should warrant and guarantee that third party intellectual property rights ar e not infringed upon when integrating mps products into any application. mps will not assume any legal responsibility for any said applications. MP2612 rev. 1.0 www.monolithicpower.com 20 9/7/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. package information qfn16 (4mm x 4mm) side view top view 1 16 13 12 9 85 4 bottom view 3.90 4.10 2.15 2.45 3.90 4.10 2.15 2.45 0.65 bsc 0.25 0.35 0.80 1.00 0.00 0.05 0.20 ref pin 1 id marking 2.30 0.65 0.35 recommended land pattern 3.80 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 vggc. 5) drawing is not to scale. pin 1 id see detail a pin 1 id option a 0.45x45 o typ. pin 1 id option b r0.25 typ. detail a pin 1 id index area 1.00 0.50 0.70

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