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mp26123 2a,24v input, 600khz 2/3-cell switching li-ion battery charger mp26123 rev. 1.01 www.monolithicpower.com 1 10/28/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. the future of analog ic technology description the mp26123 is a monolithic dc-dc step- down switching charger for 2- or 3-cell li-ion battery packs. it has an integrated high-side power mosfet can output up to a 2a charge current. it also has peak-current?mode control for fast loop response and easy compensation. the mp26123 uses a sense resistor to control a programmable charge current, and accurately regulates the charge current and charge voltage using two control loops. the mp26123 has multiple fault condition protections that include cycle-by-cycle current limiting and thermal shutdown. other safety features include battery temperature monitoring and protection, charge status indication and programmable timer to cease the charging cycle when timer out. the mp26123 requires a minimal number of readily-available external components. the mp26123 is available in a 4mm x 4mm 16- pin qfn package. features ? charges 2- or 3-cell li-ion battery packs ? wide operating input range ? programmable charging current of up to 2a ? 0.75% v batt accuracy ? 0.2 ? integrated power mosfet ? up to 90% efficiency ? fixed 600khz frequency ? preconditioning for fully depleted batteries ? charging status indicator ? input supply fault indicator ? thermal shutdown ? cycle-by-cycle over-current protection ? battery temperature monitor and protection applications ? mobile internet device ? portable media player ? netbook ? charger for 2- or 3-cell li-ion batteries ? distributed power systems 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
mp26123 ? 2a, 24v input, 600khz 2-3 cell switching li-ion battery charger mp26123 rev. 1.01 www.monolithicpower.com 2 10/28/2011 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 ) MP26123DR qfn16 (4x4mm) m26123 -40c to +85c *for tape & reel, add suffix ?z (e.g. MP26123DR?z) for rohs compliant packaging, add suffix ?lf (e.g. mp MP26123DR?lf?z) package reference top view exposed pad on backside pin 1 id vcc ntc acok chgok gnd csp batt compi 1 2 3 4 13 14 15 16 8 7 6 5 compv cells en vref33 tmr bst sw vin 12 11 10 9 absolute maxi mum ratings (1) supply voltage vcc, vin ............................ 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 = 25c) (2) ............................................................. 2.7w junction temperature ...............................150c lead temperature ....................................260c storage temperature............... -65c to +150c recommended operating conditions (3) supply voltage v in ..............................9v to 24v maximum junction temp. (t j ) ..................125c thermal resistance (4) ja jc qfn16 (4x4mm) ..................... 46 ...... 10... 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 cont inuous 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 circui try 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 board.
mp26123 ? 2a, 24v input, 600khz 2-3 cell switching li-ion battery charger mp26123 rev. 1.01 www.monolithicpower.com 3 10/28/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. electrical characteristics v in = 19v, t a = 25c, cells=0v, unless otherwise noted. parameters symbol condition min typ max units cells=0v 8.337 8.4 8.463 terminal battery voltage v batt cells=float 12.505 12.6 12.695 v 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 1 a cc (5) 4.1 a peak current limit 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 v tc 3 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 =7v 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 (5) t on 100 ns under-voltage lockout threshold rising 3 3.2 3.4 v under-voltage lockout threshold hysteresis 200 1000 mv open-drain sink current v drain =0.3v 5 ma dead battery indicator in trickle mode c tmr =0.1 f 30 min recharge threshold at v batt v rechg 4.0 v/cell recharge hysteresis 100 mv ntc low-temp rising threshold r ntc =ncp18x103, 0c 70.5 73.5 76.5 %of vref33 ntc high-temp falling threshold r ntc =ncp18x103, 50c 27.5 29.5 31.5 %of vref33 vin min head-room (reverse blocking) vin ? v batt 180 mv
mp26123 ? 2a, 24v input, 600khz 2-3 cell switching li-ion battery charger mp26123 rev. 1.01 www.monolithicpower.com 4 10/28/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. electrical characteristics ( continued ) v in = 19v, t a = 25c, cells=0v, unless otherwise noted. parameters symbol condition min typ max units en input low voltage 0.4 v en input high voltage 1.8 v en =4v 4 en input current en =0v 0.2 a en =4v 0.5 ma supply current (shutdown) en =4v, consider vref33 pin output current, r 3 =10k,r ntc =10k 0.665 ma supply current (quiescent) en =0v, cells=0v 2.0 ma thermal shutdown (5) 150 c vref33 output voltage 3.3 v vref33 load regulation i load =0 to 10ma 30 mv notes: 5) guaranteed by design.
mp26123 ? 2a, 24v input, 600khz 2-3 cell switching li-ion battery charger mp26123 rev. 1.01 www.monolithicpower.com 5 10/28/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. pin functions pin # name description 1 vcc ic supply voltage. 2 ntc thermistor input. connect a resistor from this pin to vref33, and the thermistor from this pin to ground. 3 acok valid input supply indicator. open drain out put. add pull-up resistor. logic low indicates the presence of a valid input supply. 4 chgok charging status indicator. open drain output. add pull-up resistor. logic low indicates normal charging. logic high indicates either a completed charge process or suspended process because of some fault. 5 vref33 internal linear regulator, 3.3v reference output. bypass to gnd with a 1 f ceramic capacitor. 6 en on/off control input. 7 cells command input for the number of li-ion cells. connect to vref33 or float for 3-cell operation. ground for 2-cell operation. 8 compv v-loop compensation. decouple this 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-charge current-sense?p ositive input. connect a resistor rs1 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. this node should be placed outside of the switching diode (d2) to the input ground path to prevent switching current spikes from inducing voltage noise into the part. 13 tmr set safe timer period. 0.1a current charge s and discharges the external capacitor decoupled to gnd. the capacitor value programs the timer period. 14 bst bootstrap. requires a charged capacitor to driv e the power switch?s gate above the supply voltage. connect a capacitor between sw and bst pi ns to form a floating supply across the power switch driver. 15 sw switch output. 16 vin regulator input voltage. the mp26123 regulates a 9v-to-24v input to a voltage suitable for charging either a 2- or 3-cell li-ion battery. requires capacitors to prevent large voltage spikes from appearing at the input.
mp26123 ? 2a, 24v input, 600khz 2-3 cell switching li-ion battery charger mp26123 rev. 1.01 www.monolithicpower.com 6 10/28/2011 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/simulation battery load, t a =25c, unless otherwise noted.
mp26123 ? 2a, 24v input, 600khz 2-3 cell switching li-ion battery charger mp26123 rev. 1.01 www.monolithicpower.com 7 10/28/2011 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/simulation battery load, t a =25c, unless otherwise noted.
mp26123 ? 2a, 24v input, 600khz 2-3 cell switching li-ion battery charger mp26123 rev. 1.01 www.monolithicpower.com 8 10/28/2011 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/simulation battery load, t a =25c, unless otherwise noted.
mp26123 ? 2a, 24v input, 600khz 2-3 cell switching li-ion battery charger mp26123 rev. 1.01 www.monolithicpower.com 9 10/28/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. functional block diagram figure 1?functional block diagram
mp26123 ? 2a, 24v input, 600khz 2-3 cell switching li-ion battery charger mp26123 rev. 1.01 www.monolithicpower.com 10 10/28/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. operation the mp26123 is a peak-current?mode controlled switching charger for use with li-ion batteries. at the beginning of a cycle, m1 is off, and the comp voltage is higher than the output of current sense amplifer, a1. the pwm comparator?s output is low, and the rising edge of the 600khz clk signal sets the rs flip-flop, which turns on m1, thus connecting the sw pin and the inductor to the input supply. as the inductor current increases, the output of a1 increases. while the sum of a1?s output and the slope compensation remains below the comp voltage, the falled edge of the clk resets the rs flip-flop. when this signal exceeds the comp voltage, the rs flip-flop resets and turns m1 off. the external switching diode d2 then conducts the inductor current. the mp26123 uses comp to select the smaller value of gmi and gmv to implement either current loop control or voltage loop control. current loop control occurs when the battery voltage is low, which results in the saturation of the gmv output. gmi compares the charge current (as a voltage sensed through rs1) against the reference voltage to regulate the charge current to a constant value. when the battery voltage charges up to the reference voltage, the output of gmv goes low and initiates voltage loop control to control the duty cycle to regulate the output voltage. the mp26123 has an internal linear regulator? vref33?to power internal circuitry. it can also power external circuitry as long as the load does not exceed the maximum current (30ma). connect a 1 f bypass capacitor from vref33 to gnd to ensure stability. charge cycle (mode change: trickle ? cc ? cv) at the start of a charging cycle, the mp26123 monitors v batt . if v batt is lower than the trickle- charge threshold, v tc (typically 3.0v/cell), the charging cycle will start in ?trickle-charge mode? (10% of the rs1 programmed constant-charge current, i cc ) until the battery voltage reaches v tc . if the charge stays in the ?trickle-charging mode? until ?time out? condition is triggered, charging terminates and will not resume until the input power or en signal refreshes. otherwise, gmi regulates the charge current 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 constant- voltage?mode threshold, gmv regulates the comp pin and the duty cycle for constant voltage mode. when the charge current drops to the battery-full threshold, i bf (typical 10% cc), the battery is defined as fully charged, the charger stops charging, and chgok goes high to indicate the charge-full condition. if the total charge time exceeds the timer period, the charging terminates at once and will resume when either the input power or en signal can restart the charger. figure 2 shows the typical charge profile of mp26123. figure 2?li-ion battery charge profile
mp26123 ? 2a, 24v input, 600khz 2-3 cell switching li-ion battery charger mp26123 rev. 1.01 www.monolithicpower.com 11 10/28/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. automatic recharge after the battery has completely recharged, the charger disables all blocks except the battery voltage monitor to limit leakage current. if the battery voltage falls below 4.0v/cell, the chip will begin recharging using soft-start. the timer will then reset to avoid timer-related charging disruptions. charger status indication mp26123 has two open-drain status outputs: acok and chgok . the acok pin goes low when the ic supply voltage vcc exceeds the under-voltage lockout threshold and the regulated voltage vin is 300mv higher than v batt to make sure the regulator can operate normally. chgok indicates charge status. table 1 describes acok and chgok outputs under different charge conditions. table 1 D charging status indication acok chgok charger status low low in charging low high end of charge, ntc fault, timer out, thermal shutdown, en disable high high vin ?v batt <0.3v. v cc mp26123 ? 2a, 24v input, 600khz 2-3 cell switching li-ion battery charger mp26123 rev. 1.01 www.monolithicpower.com 12 10/28/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. d2 r6 10k figure 3?mp26123 with power-path management
mp26123 ? 2a, 24v input, 600khz 2-3 cell switching li-ion battery charger mp26123 rev. 1.01 www.monolithicpower.com 13 10/28/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. operation flow chart figure 4? normal charging operation flow chart
mp26123 ? 2a, 24v input, 600khz 2-3 cell switching li-ion battery charger mp26123 rev. 1.01 www.monolithicpower.com 14 10/28/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. operation flow chart (continued) figure 5?fault protection flow chart
mp26123 ? 2a, 24v input, 600khz 2-3 cell switching li-ion battery charger mp26123 rev. 1.01 www.monolithicpower.com 15 10/28/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. application information setting the charge current the charge current of mp26123 is set by the sense resistor rs1 (see typical application), and determined with the following equation: ?? ?? m ? rs1 200mv a i chg ? (1) selecting the inductor use a 1h to 10h inductor for most applications. the inductance value can be derived from the following equation. out in out in l osc v(vv) l vif ?? ? ?? ? (2) where i l is the inductor ripple current. choose i l to be approximately 30% of the maximum charge current, 2a. v out is the 2- or 3-cell battery voltage. the maximum inductor peak current is: ? ?? l l(max) chg i ii 2 (3) under light load conditions below 100ma, use a larger inductor value to improve efficiency. select an inductor with a dc resistance of less than 200m ? to optimize efficiency. ntc function as figure 6 shows, the low temperature threshold and high-temperature threshold are preset internally to 73.5%vref33 and 29.5%vref33 using a resistive divider. for a given ntc thermistor, we can select appropriate r3 and r6 resistors to set the ntc window. for the thermistor (ncp18xh103) noted in above electrical characteristic, at 0c, r ntc_cold = 27.445k; at 50c, r ntc_hot = 4.1601k. assuming that the ntc window is between 0c and 50c, we can derive the following equations: ntc _ cold th _ low ntc _ cold r6 //r v 73.5% r3 r6 // r vref33 ?? ? (4) th _ high ntc _ hot ntc _ hot v r6 //r 29.5% r3 r6 // r vref33 ?? ? (5) according to equation (4) and equation (5), we determine r3 = 9.63k and r6 = 505k. for simplification, select r3=10k and r6 no connect to approximate the specification. ntc vref33 low temp threshold high temp threshold r ntc r3 r6 v th_low v th_high figure 6? 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. chose an input capacitor with an impedance at the switching frequency less than the input source impedance to prevent high- frequency?switching current. use ceramic capacitors with x5r or x7r dielectrics with low esr and small temperature coefficients. a 4.7f capacitor is sufficient for most applications. selecting the output capacitor the output capacitor limits output voltage ripple and ensures regulation loop stability. the output capacitor impedance should be low at the switching frequency. use ceramic capacitors with x5r or x7r dielectrics. pc board layout connect the high frequency and high current paths (gnd, in and sw) to the device with short, wide, and direct traces. place the input capacitor as close as possible to the in and gnd pins. place the external feedback resistors next to the fb pin. keep the switching node sw short and away from the feedback network.
mp26123 ? 2a, 24v input, 600khz 2-3 cell switching li-ion battery charger notice: the information in this document is subject to change wi thout notice. please contact m ps for current specifications. users should warrant and guaran tee that third party intellectual property right s are not infringed upon when integrating mps products into any application. mps will not assume any legal responsibility for any said applications. mp26123 rev. 1.01 www.monolithicpower.com 16 10/28/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. package information qfn16 (4 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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