1 r ev.1. 2 10 - general description features maximum absolute ratings application ELM650DA is a step down switching regulator, which has a built-in 40v p-channel power mosfet for delivering output current. elm650a is designed to allow for operating a wide supply voltage range from 8v to 36v and capable of delivering 2a output current. ELM650DA features programmable cv/cc mode control functions, the cv mode (constant voltage) function to provide a regulated voltage output and the cc mode (constant current) function provide a current limitation function, it is suitable for the dc/dc switching power applications when requested the current limitation function. caution: permanent damage to the device may occur when ratings above maximum absolute ones are used. e lm 650 d a cc/cv mode 36v step down 2a dc/dc converter ? cc/cv mode control ? soft start function for start-up ? output over-voltage protection ? over temperature protection ? fold back short-circuit protection ? high efficiency operation ? input voltage r ange : 8v to 36v ? input voltage surge : 40 v ? fixed operating frequency : 100khz ? voltage reference accuracy : 1% ? current limit accuracy : 4 % ? package : sop- 8 ? car charger ? portable charger applications ? dc/dc converters with current limited ? general purpose cv/cc power supply parameter symbol limit unit vcc to gnd vcc - 0.3 to +40.0 v lx to vcc lx + 0.3 to -40.0 v vsen to gnd vsen - 0.3 to + 7.0 v i sen+ to gnd isen+ - 0.3 to + 7.0 v i sen- to gnd isen- - 0.3 to +7.0 v ovp to gnd ovp - 0.3 to + 7.0 v comp to gnd comp - 0.3 to + 7.0 v o utput current icc 3 a power dissipation at ta <60 c pd 0.75 w operationg temperature top -40 to +85 c storage temperature range tstg - 60 to 150 c * taping direction is one way. elm 650da - n symbol a package d : sop-8 b product version a c taping d irection n : refer to pkg file ELM650DA - n a b c selection guide
2 r ev.1. 2 10 - b lock diagram r e f e r e n c e g e n e r a t o r g a t e d r v c o n t r o l l o g i c + - p w m c o m p . s o f t s t a r t c u r r e n t a m p . + - - + - e r r o r a m p . r a m p o t p - + - + l x v c c 5 6 2 v s e n 1 g n d v s s 0 . 4 v 1 . 1 8 v 8 c o m p 1 . 1 8 v 7 o v p 4 3 i s e n - i s e n + pin con figuration pin no. pin name pin description 1 gnd gnd 2 vsen the voltage sense input 3 i sen- the current sense negative input 4 isen+ the current sense positive input 5 lx regulator output 6 vcc the input supply voltage 7 ovp the over- voltage sense input 8 comp the e/a output pin for frequency compensation so p - 8 ( top view) 4 3 2 1 5 6 7 8 e lm 650 d a cc/cv mode 36v step down 2a dc/dc con verter
3 r ev.1. 2 10 - s tandard circuit e l m 6 5 0 d a c o m p g n d v c c o v p l x i s e n + i s e n - v s e n c 2 + d 1 a r 2 c 5 r 3 r 4 r 6 r 5 l 1 g n d v o u t c 4 c 3 r 1 c 1 + v i n 1 2 8 3 7 4 6 5 u 1 e lm 650 d a cc/cv mode 36v step down 2a dc/dc con verter functional descriptions 1. cv/cc mode control ELM650DA provides cv/cc function. the cv (constant voltage) function is implemented to deliver a regu - lated output voltage for the output terminal, and the cc (constant current) function is to limit output current to be a limited value to prevent the device damaged due to output short circuit or over current condition. 2. soft start function ELM650DA is composed of built-in internal soft start function to prevent a large surge current happening when during start-up period due to the surge current charging output filter capacitors. 3. output over-voltage protection ELM650DA provides output over-voltage protection function. when output over-voltage happens, ELM650DA shuts down and recovers to normal state automatically if output over-voltage is released. 4. output short-circuit protection ELM650DA provides output short-circuit protection function. when output short-circuit happens, ELM650DA shuts down and recovers to normal state automatically if output short-circuit is released. marking s o p - 8 mark content 650 product no.code a to o a ssembly lot no.
4 r ev.1. 2 10 - parameter symbol c ondition min. typ. max. unit input voltage section input voltage vin 8 36 v input no load current ino-load iout=0a 10 ma oscillator section operating frequency fosc 90 110 k hz duty cycle range duty 95 % error amplifier section reference voltage of the voltage error amplifier vvsen 1.168 1.180 1.192 v reference voltage of the current error amplifier visen 107.5 112.0 116.5 mv tran conductance of error amplifier gmerr 150 a/v output over voltage protection section reference voltage of the over voltage comparator vovp 1.145 1.180 1.215 v output short circuit protection section reference voltage of the short circuit fold back comparator vscp 0.4 v mosfet section drain-source breakdown voltage v(br)dss vgs=0v, iout=250 a -40 v drain-source on-state resistance rds (on) vin=24v, iout=1a 200 m electrical characteristics vin=12v, iout=1.0a, top=25 c , unless otherwise specified e lm 650 d a cc/cv mode 36v step down 2a dc/dc con verter application circuits e l m 6 5 0 d a c o m p g n d v c c o v p l x i s e n + i s e n - v s e n r 5 r 6 r 9 l 2 1 2 8 3 7 4 6 5 u 1 l 4 r 2 c 6 d 1 r 3 r 4 c 7 + c 8 r 7 r 1 0 r 8 l e d v o u t + v o u t - l 3 r 1 c 1 0 c 4 c 5 + c 2 c 3 c 1 g n d v i n c 9 + l 1 1 2 3 4
5 r ev.1. 2 10 - device description value q'ty c1 input ecap, 47 f/35v, 6.3*7mm 47 f/35v 1 c2 input ecap, 100 f/35v, 6.3*7mm 100 f/35v 1 c3 mlcc, 0603, x7r 104 1 c4 mlcc, 0603, x7r 473 1 c5 mlcc, 0603, npo 47pf 1 c6 mlcc, 0805, x7r 102 1 c7 output ecap, 220 f/6.3v, 6.3*7mm 220 f/6.3v 1 c8 mlcc, 0603, x7r na 0 c9 mlcc, 0603, x7r 104 1 c10 mlcc, 0603, x7r 104 1 d1 schottky diode, smb, 40v/5a sb54 1 l1 dr choke, 4*6mm 15 h 1 l2 power inductor, t- 5052b, l= 100 h wire=0.65 100 h 1 l3 t core, 6*3*3, 0.5*2c*3ts 22 h 1 l4 smd bead core , 0805, 220 3000ma bead 1 led led, green led 1 r1 chip r , 0603 , 5% 100k 1 r2 chip r , 0805 , 5% 10r 1 r3 chip r , 0603 , 5% 51r 1 r4 chip r , 0603 , 5% 51r 1 r5 chip r , 1206 , 1% 0.045r 1 r6 chip r , 0603 , 1% 390k 1 r7 chip r , 0603 , 1% 118k 1 r8 chip r , 0603 , 5% 470r 1 r9 chip r , 0603 , 5% 120r 1 r10 chip r , 0603 , 5% 1k 1 u1 buck controller, cc/cv function, vin 8~36v, sop-8 ELM650DA 1 bom list for a pplication circuits e lm 650 d a cc/cv mode 36v step down 2a dc/dc con verter r v s e n 1 v o u t r v s e n 2 e l m 6 5 0 d a v s e n app lica tion notes fig-1: output voltage setting 1. output voltage setting figure 1 shows the connections for setting the output voltage value. typically, selecting the proper ratio of the two feedback resistors rvsen1 and rvsen2 by using rvsen2 118k and determining vsen from the following equation: rvsen1 = rvsen2 ( vout / 1.18v - 1 )
6 r ev.1. 2 10 - e lm 650 d a cc/cv mode 36v step down 2a dc/dc con verter e l m 6 5 0 d a i s e n + i s e n - i c c v o u t r s 2. cc current setting the constant current value of ELM650DA is set by a rs resistor which is connected between isen+ and isen- pin. the output current of cc mode and rs resistor are set by the following equation: rs = 0.112 / icc when output voltage is set over 6v, the voltage of the v(isen+), v(isen-) should be set under 6v by the follow - ing equation: visen = (1/ks) vout 6v, ks = (rs 1 + rs 2 ) / rs 2 = (rs 3 + rs 4 ) / rs 4 also ks = (rs 1 + rs 2 ) / rs 2 , and rs = ks 0.112/icc at this time. fig- 2 : c onstant current mode setting 3. input capacitor selection the bulk input capacitor selection is based on the voltage rating, the rms current carrying capability, and the required input voltage ripple. the capacitor voltage rating is recommended with 1.5 times for the maximum input voltage as conservative guideline, depending on the application condition. the capacitor rms current rating is considered for stress condition, and the trapezoid current waveform as the simplified formula is described: irms = iout(max) * ( vout / vin ) vin = input voltage ; vout = output voltage ; iout(max) = maximum output current. the capacitor values with respect to the required input voltage ripple if neglect esr is described: c = iout(max) * t / v t = capacitor supplied charging time ; v = allowable input voltage ripple. r s 4 r s 1 r s 2 i s e n + i s e n - r s 3 r s v o u t fig- 3 : c onstant current mode setting ( at vout 6v )
7 r ev.1. 2 10 - e lm 650 d a cc/cv mode 36v step down 2a dc/dc con verter 4 . output rectifier selection the output rectifier is selected by the consideration of the reverse voltage rating, the current rating and the re - verse recovery time and forward voltage drop for the power loss. the reverse voltage rating should be at least 1.25 times the maximum input voltage for the consideration of voltage arc. the current rating should be larger than the maximum inductor current. the diode conduction loss is due to the forward conduction and is described: pcond = iout(max) * vf * ( 1 - vout / vin ) vin = input voltage ; vout = output voltage ; iout(max) = maximum output current ; vf = diode forward voltage. the diode reverse recovery loss is due to the reverse recovery from the forward conduction to the reverse blocking state, and is described: prr = qrr * vin / tsw vin = input voltage ; qrr = diode reverse recovery charge ; tsw = switching period. 5. output inductor selection the output inductor is selected for the trade-offs between the output inductor current ripple, dc resistance for power loss, load transient response time, and the physical size. the output inductor current ripple determines the output voltage ripple requirement, and the inductors dc re - sistance concerns the power loss. the larger the inductor value, the smaller the inductor ripple current, but the slower the transient response time, the larger the inductor dc resistance, and hence the larger the power loss. the inductance value is described: l = vout * ( 1 - vout / vin ) * tsw / ll vin = input voltage ; vout = output voltage ; tsw = switching period ; ll = inductor ripple current. 6. output capacitor selection the output capacitor is selected for the trade-offs between output ripple voltage requirement, the output volt - age rating, the rms current rating, the esr and esl for the load transient, and the physical size. the capacitor voltage rating is recommended with 1.5 times for the maximum output voltage as conservative guideline . the capacitor rms current rating is considered for stress condition and the trapezoid current waveform as the simplified formula is described: irms = il / 23 ; il = inductor ripple current. the output ripple voltage with respect to the capacitor esr is described: v = i * ( esr + tsw / ( 8 * c ) ) i = capacitor ripple current which is equivalent to the inductor ripple current ; esr = capacitor equivalent series resistance ; tsw = switching period. 7. pc board layout consideration good pc board layout is very important in switching converter design. if designed improperly, the pc board could radiate excessive noise and contribute to the converter instability.
8 r ev.1. 2 10 - c o m p v c c o v p l x i s e n + i s e n - v s e n r 5 r 6 r 9 l 2 2 8 3 7 4 6 5 u 1 r 2 d 1 r 3 r 4 c 7 + c 8 r 7 l e d l 3 + c 2 c 1 g n d v i n c 1 0 + l 1 1 3 4 e l m 6 5 0 d a g n d r 1 c 1 1 c 5 c c 4 1 c c 6 l 4 b d d a e c 3 c 9 2 r 1 2 r 1 1 r 1 4 r 1 3 r 1 5 1 2 3 4 v o u t + v o u t - r 8 u s b r 1 0 fig- 4 : pc board layout guidelines fig- 5 : the pcb layout of car charger with ELM650DA controller e lm 650 d a cc/cv mode 36v step down 2a dc/dc con verter follows below pc board layout guidelines could get better performance: 1) path a : the vout- is returned to input bulk capacitor c2, by passing through output capacitor c7. 2) path b : the output rectifier d1, together with snubber r2 and c2, are shunt to common ground and returned to input bulk capacitor c2. 3) path c and d : the decoupling capacitor c11, the compensation network r1, c4, c5, the voltage feedback network r6, r7, c8, and the overvoltage sensing network r8, r9, are connected to ic ground, and returned to input bulk capaci - tor c2 and output capacitor c7. 4) path e : input capacitor c2 is returned to input ground, after all ground networks are following the above paths de - signed.
9 r ev.1. 2 10 - e lm 650 d a cc/cv mode 36v step down 2a dc/dc con verter typical c haracteristics ? vout=5v : cin=47f, cout=220f, l=100h, r1=100k , r2=0.0625 , r3=390k r4=118k , r5= 470 , r6= 12 0 , c3 = 0.047 f, c 4 = 47 p f, top=25c -30 0 30 60 90 108 110 112 114 116 118 iload=short top ( ? ) visen (mv) current reference-top vin=12v vin=24v 5 10 15 20 25 30 35 109 110 111 112 113 114 115 116 iload=short vin (v) visen (mv) current reference-vin -30 0 30 60 90 1.16 1.17 1.18 1.19 1.20 top ( ? ) vref (v) voltage reference-top vin=12v vin=24v iload=1a 5 10 15 20 25 30 35 1.175 1.180 1.185 1.190 1.195 1.200 iload=1a vin (v) vref (v) voltage reference-vin
10 r ev.1. 2 10 - 0.001 0.01 0.1 1 10 0 20 40 60 80 100 vin=12v iout (a) efficiency (%) efficiency-iout vin=24v 5 10 15 20 25 30 35 100.2 100.4 100.6 100.8 101.0 101.2 101.4 101.6 101.8 102.0 iload=1a vin (v) frequency (khz) frequency-vin 0.001 0.01 0.1 1 10 0 1 2 3 4 5 6 vin=12v iout (a) vout (v) vout-iout vin=24v e lm 650 d a cc/cv mode 36v step down 2a dc/dc con verter
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