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| rp500x series step-down dc/dc converters with synchronous rectifier no.ea-155-080522 1 outline the rp500x series are cmos-based step-down dc/dc converters with synchronous rectifier. each of these ics consists of an oscillator, a switching control circuit, a reference voltage unit, an error amplifier, a soft-start circuit, protection circuits, uvlo circuit, switching transistors, and so on. a low ripple, high efficiency step-down dc/dc converter can be easily composed of this ic with only an inductor and capacitors. in terms of the output voltage, since the feedback resistances are built-in, the voltage is fixed internally. 50mv(custom-made) step output can be set by laser-trim and 1.5% or 24mv tolerance depending on the output voltage is guaranteed. mode alternative circuit works automatically for improving the efficiency. considering fixed noise frequency, pwm fixed control type is also available. as protection circuits, the current limit circuit which limits peak current of lx at each clock cycle, and the latch type protection circuit which works if the term of the over-current condition keeps on a certain time exist. the latch-type protection circuit works to latch an internal driver with keeping it disable. to release the condition of the protection, after disabling this ic with a chip enable circuit, enable it again, or restart this ic with power-on or make the supply voltage at uvlo detector threshold level or lower than uvlo. since packages are dfn(plp)1820-6, sot23-6, wlcsp-6 (0.16 ), high density mounting on boards is possible. features input voltage range.............................................. 2.55v to 5.50v output voltage....................................................... 1.1v to 3.3v (it is possible in the range from1.1v to 3.3v with a step 0.1v) high accuracy output voltage .............................. 1.5% (vout 1.6v) 24mv (vout<1.6v) supply current ......................................................... typ.400 a(at pwm mode) typ.100 a(at pfm mode) oscillator frequency ............................................. typ. 1.2mhz built-in soft start function ..................................... typ . 0.1ms built-in latch type protection ................................ typ.1.5ms built-in uvlo function.......................................... typ. 2.2v two choices of switching mode ............................ automatic pwm/pfm mode change / pwm fixed packages............................................................... dfn(plp)1820-6, sot23-6w, wlcsp-6 (0.16 ) applications power source for portable equipment such as cellular, pda, dsc, notebook pc power source for hdd power source for li-ion battery-used equipment
rp500x 2 block diagram switching control current protection soft start vref l x v out v in ce pgnd oscillator pwm current feedback ramp compensation uvlo agnd chip enable rp500x 3 pin configuration sot-23-6w 1 2 3 6 4 5 2.8 2.9 dfn ( plp ) 1820-6 1 2 3 64 5 2.0 1.8 to p v i ew wl-csp-6 6 5 4 1 3 2 bump side pin descriptions wlcsp-6 / sot-23-6w pin no. symbol pin description 1 v out output 2 pgnd ground 3 l x lx switching 4 v in voltage supply 5 agnd ground 6 ce chip enable (high active) dfn(plp)1820-6 pin no. symbol pin description 1 ce chip enable (high active) 2 agnd ground 3 v in voltage supply 4 l x lx switching 5 pgnd ground 6 v out output * tab in the parts have gnd level. (they are connected to the back side of this ic.) do not connect to other wires or land patterns rp500x 4 absolute maximum ratings agnd=pgnd=0v symbol item rating unit v in v in supply voltage 6.5 v v lx lx pin voltage -0.3 to v in +0.3 v v ce ce pin input voltage -0.3 to v in +0.3 v v out vout pin voltage -0.3 to v in +0.3 v i lx lx pin output current 800 ma dfn(plp) 880 sot 430 p d power dissipation wlcsp 650 mw topt operating temp. range -40 to 85 c tstg storage temp. range -55 to 125 c ? absolute maximum ratings absolute maximum ratings are threshold limit values that must not be exceeded ever for an instant under any conditions. moreover, such values for any two items must not be reached simultaneously. operation above these absolute maximum ratings may cause degradation or permanent damage to the device. these are stress ratings only and do not necessarily imply functional operation these limits. ? selection guide in the rp500 series, output voltage, function options, etc. can be designated with user's request. part number can be designated as follows: rp500x xx x x - xx part number ? ?? ?? ?? ?? a b c d e ? code contents a designation of the package k: dfn(plp)1820-6 n: sot-23-6w z: wl-csp-6 b designation of output voltage designation is possible in the range from 1.1v to 3.3v with a step of 0.1v c designation of the function (with or without pwm/pfm alternative function, auto discharge function) 1:with pwm/pfm alternative, without auto discharge 2:without pwm/pfm alternative, without auto discharge 4:without pwm/pfm alternative function, with auto discharge function d frequency a: 1.2mhz e designation of the taping type tr:sot23-6w / dfn(plp)1820-6 e2:wlcsp-6 *0.05v step is also available as a custom code. rp500x 5 electrical characteristics topt=25c symbol item condition min. typ. max. unit v in operating input voltage 2.55 5.50 v v out step-down output voltage v in =v ce =3.6v or v set +1v v out 1.6v v out <1.6v -1.5% -0.024 +1.5% 0.024 v ? v out / ? t step-down output voltage temperature coefficient -40 c t opt 85 c 100 ppm/ c f osc oscillator frequency v in =v ce =3.6v or v set +1v -20% 1.2 +20% mhz i ss 1 supply current 1 v in =v ce =5.5v,v out =0 400 500 a i ss 2 supply current 2 v in =v ce =5.5v,v out =5.5v 100 160 a i stb standby current v in =5.5v,v ce =0v 0 5 a i ceh ce "h" input current v in =v ce =5.5v -1 0 1 a i cel ce "l" input current v in =5.5v,v ce =0v -1 0 1 a i vouth v out "h" input current v in =v out =5.5v,v ce =0v -1 0 1 a i voutl v out "l" input current v in =5.5v,v ce =v out =0v -1 0 1 a i lxleakh lx leakage current "h" v in =v lx =5.5v,v ce =0v -1 0 5 a i lxleakl lx leakage current "l" v in =5.5v,v ce =v lx =0v -5 0 1 a v ceh ce "h" input voltage v in =5.5v 1.0 v v cel ce "l" input voltage v in =5.5v 0.4 v r onp on resistance of pch tr. i lx =-100ma 0.3 ? r onn on resistance of nch tr. i lx =-100ma 0.38 ? maxdty max duty ratio 100 % t start soft-start time v in =v ce =3.6v or v set +1v 120 150 s i lxlim lx current limit v in =v ce =3.6v or v set +1v 600 900 ma t prot protection delay time v in =v ce =3.6v or v set +1v 0.5 1.5 5.0 ms v uvlo 1 uvlo detector voltage v in =v ce 2.1 2.2 2.3 v v uvlo 2 uvlo released voltage v in =v ce 2.2 2.3 2.4 v *) test circuit is "open loop" and v in =v ce =3.6v or v set +1v, agnd=pgnd=0v unless otherwise noted. rp500x 6 typical application 1 2 3 c out 10 f ce agnd 4 5 v in lx v out v in c in 10 h load pgnd 6 rp500 series parts recommendation l: 4.7h vlf3010at-4r7mr30 (tdk) c out : 10f ceramic c2012jb0j106k (tdk) c in : 10f c2012jb0j106k (tdk) when you use these ics, consider the following issues: set the same level as agnd and pgnd. set external components such as an inductor, c in , c out as close as possible to the ic, in particular, minimize the wiring to v in pin and pgnd pin. the wiring between v out and load and between l and v out should be separated. use an external capacitor c in between v in and gnd, and c out with a capacity of 10f or more ceramic type. choose an inductor with inductance range from 4.7 h to 10.0 h. the phase compensation has been made by these values with output capacitors. the recommendation characteristics of the inductor are low dc resistance, large enough permissible current, and strong against the magnetic saturation. inductance value may shift depending on an inductor. if the inductance value at an actual load current is low, lx peak current may increase and may overlap the lx current limit. as a result, over current protection may work. over current protection circuit may be affected by self-heating and heat radiation environment. reinforce the v in , pgnd, and v out lines sufficiently. large switching current may flow in these lines. if the impedance of v in and pgnd lines is too large, the internal voltage level in this ic may shift caused by the switching current, and the operation might be unstable. the performance of power source circuits using these ics extremely depends upon the peripheral circuits. pay attention in the selection of the peripheral circuits. in particular, design the peripheral circuits in a way that the values such as voltage, current, and power of each component, pcb patterns and the ic do not exceed their respected rated values.( such as the voltage, current, and power) rp500x 7 operation of the buck converter and the output current the dc/dc converter charges energy in the inductor when l x transistor is on, and discharges the energy from the inductor when l x transistor is off and controls with less energy loss, so that a lower output voltage than the input voltage is obtained. the operation will be explained with reference to the following diagrams: rp500x 8 output current and selection of external components the relation between the output current and external components is as follows: when p-channel tr. of l x is on: (wherein, ripple current p-p value is described as i rp , on resistance of p-channel tr. and n-channel tr. of l x are respectively described as ronp and ronn, and the dc resistor of the inductor is described as r l .) v in = v out + (r onp + r l ) x i out + l x i rp / ton ......................................................... equation 1 when p-channel tr. of l x is "off"(n-channel tr. is "on"): l x i rp / toff = r onn x i out + v out + r l x i out ......................................................... equation 2 put equation 2 to equation 1 and solve for on duty of p-channel transistor, ton/(toff + ton) = d on , d on = (v out + r onn x i out + r l x i out ) / (v in + r onn x i out ? r onp x i out ) .......... equation 3 ripple current is as follows: i rp = (v in ? v out ? r onp x i out ? r l x i out ) x d on / fosc / l ................................... equation 4 wherein, peak current that flows through l, and l x tr. is as follows: ilmax = i out + i rp / 2 .................................................................................................. equation 5 consider ilmax, condition of input and output and select external components. *the above explanation is directed to the calculation in an ideal case in continuous mode. rp500x 9 timing chart (1)soft-start time in the case of starting this ic with ce, the operation can be as in the timing chart below. when the voltage of ce pin is beyond the threshold level, the operation of the ic starts. the threshold voltage of ce pin is in between ce ?h? input voltage and ce ?l? input voltage described in the electrical characteristics table. soft-start circuit operates, and after the certain time, the reference voltage inside the ic is rising gradually up to the constant value. soft-start time is the time interval from ce starting point to the reference voltage level reaching point up to this constant level. soft start time is not always equal to the turn-on speed of dc/dc converter. the power supply capacity for this ic, load current, inductance and capacitance values affect the turn-on speed. in the case of starting with power supply, when the input voltage for v in is larger than uvlo released voltage, soft start circuit operates, and after that, the same explanation above is applied to the operation. turn-on speed is affected by next conditions; (1) v in voltage rising speed depending on the power supplier to the ic and input capacitor c in . (2) output capacitor c out value and load current value. v ceh ic voltage reference inside soft-start time v out voltage v cel ce pin: threshold level lx voltage ce pin input signal depending on power supply, load current, external components soft-start circuit operating rp500x 10 (2) under voltage lockout (uvlo) circuit the under voltage lockout circuit (uvlo) stops the switching operation of dc/dc converter if v in voltage becomes less than uvlo detector threshold. to restart the normal operation, v in voltage must be more than uvlo released voltage. the timing chart below describes the operation with varying v in . actually, the waveform of v out at uvlo working and releasing varies depending on the initial voltage of c out and load current situation. v out voltage v in voltage v uvlo2 ic inside reference voltage soft start time v uvlo1 lx voltage set v out rp500x 11 (3) over current protection circuit over current protection circuit supervises the current flowing pch transistor at each switching cycle, and if the current beyond the lx current limit, pch transistor is turned off. further, if the over current status continues equal or longer than protection delay time, the operation of dc/dc converter stops. or, when the lx limit current is exceeded even once when the driver operates by duty100%, the operation of dc/dc converter stops. to restart the operation, restart with power on or with ce pin control. lx current limit and protection delay time is affected by self-heating and ambient environment. if the output is short and the input voltage vin is drastically dropped or becomes unstable, the protection operation and delay time may vary. protection delay time lx current limit l current pch transistor current lx voltage rp500x 12 test circuits output voltage ss oscillator frequency supply current 1,2 standby current ce h / l input current vout h / l current ce agnd v in v out pgnd lx a ce agnd v in v out pgnd lx a ce agnd v in v out pgnd lx a ce agnd v in v out pgnd lx oscilloscope ce agnd v in v out pgnd lx oscilloscope ce agnd v in v out pgnd lx a rp500x 13 lx leakage current ce input voltage rp500x 14 typical characteristics 1)output voltage vs. output current rp500x152a rp500x121 a rp500x181a rp500x251a rp500x331a 1.0 1.1 1.2 1.3 1.4 1 10 100 1000 output current(ma) output voltage(v) vin=5v vin=3.6v 1.6 1.7 1.8 1.9 2.0 1 10 100 1000 output current(ma) output voltage(v) vin=5v vin=3.6v 2.3 2.4 2.5 2.6 2.7 1 10 100 1000 output current(ma) output voltage(v) vin=5v vin=3.6v 3.1 3.2 3.3 3.4 3.5 1 10 100 1000 output current(ma) output voltage(v) vin=5v vin=4.3v 1.3 1.4 1.5 1.6 1.7 1 10 100 1000 output current(ma) output voltage(v) vin=5v vin=3.6v rp500x 15 2) output voltage vs. input voltage 3) efficiency vs. output current rp500x121a rp500x181a rp500x121a rp500x251a rp500x331 a rp500x152 a 3.24 3.26 3.28 3.30 3.32 3.34 3.36 33.544.555.5 input voltage(v) output voltage(v) iout=1ma iout=50ma iout=200ma 1.47 1.48 1.49 1.50 1.51 1.52 1.53 33.544.555.5 input voltage(v) output voltage(v) iout=1ma iout=50ma iout=200ma 1.17 1.18 1.19 1.20 1.21 1.22 1.23 33.544.555.5 input voltage(v) output voltage(v) iout=1ma iout=50ma iout=200ma 2.44 2.46 2.48 2.50 2.52 2.54 2.56 2 .6 3 .1 3 .6 4.1 4.6 5.1 input voltage(v) out put vo lt age( v) iout=1ma iout=50ma iout=200ma 0 10 20 30 40 50 60 70 80 90 100 1 10 100 1000 output current(ma) efficiency(%) vin=5v vin=3.6v vin=2.5v 0 10 20 30 40 50 60 70 80 90 100 1 10 100 1000 output current(ma) ef ficiency(%) vin=5v vin=3.6v rp500x 16 4)supply current 1?2 vs. temperature 5)supply current 1?2 vs. input voltage v in =v ce =5.5v rp500x251a rp500x331a rp500x152a rp500x151 a rp500x151a 0 100 200 300 400 500 -50-25 0 255075100 temperature(c) supply current(a) iss1 iss2 0 100 200 300 400 500 2.5 3.5 4.5 5.5 input voltage(v) supply current(a) iss1 iss2 0 10 20 30 40 50 60 70 80 90 100 1 10 100 1000 output current(ma) efficiency(%) vin=5v vin=3.6v 0 10 20 30 40 50 60 70 80 90 100 1 10 100 1000 output current(ma) ef ficiency(%) vin=5v vin=4.3v 0 10 20 30 40 50 60 70 80 90 100 1 10 100 1000 output current(ma) ef ficiency(%) vin=5v vin=3.6v rp500x 17 6)dc/dc output waveform i out =1ma i out =200ma i out =1ma i out =200ma i out =1ma i ou t =200ma (c in =c out =cerami c10f?l=4.7 h) rp500x251a rp500x121a (c in =c out =cerami c10f?l=4.7 h) (c in =c out =cerami c10f?l=4.7 h) rp500x331a 1.14 1.16 1.18 1.2 1.22 1.24 1.26 00.511.5 time(ms) output voltage(v) 1.16 1.18 1.2 1.22 1.24 0123 time(s) output voltage(v) 2.44 2.46 2.48 2.5 2.52 2.54 2.56 0 0 .5 1 1.5 time(ms) output voltage(v) 2.46 2.48 2.5 2.52 2.54 0123 time(s) output voltage(v) 3.24 3.26 3.28 3.3 3.32 3.34 3.36 00.511.5 time(ms) out put v ol ta ge(v) 3.26 3.28 3.3 3.32 3.34 0123 time(s ) output voltage(v) rp500x 18 7)output voltage vs. temperature 8) osillator frequency vs. temperature 9) osillator frequency vs. input voltage v in =3.6v 10)soft-start time vs. temperature 11)uvlo detector threshold / released volta g rp500x151a rp500x331a rp500x161a rp500x151a rp500x151a rp500x151a 1.47 1.48 1.49 1.50 1.51 1.52 1.53 -50 -25 0 25 50 75 100 temperature(c) output voltage(v) 3.24 3.26 3.28 3.3 3.32 3.34 3.36 -50 -25 0 25 50 75 100 temperature(c) output voltage(v) 1050 1100 1150 1200 1250 1300 1350 2.5 3.5 4.5 5.5 input voltage(v) frequency(khz) -40 25 85 1050 1100 1150 1200 1250 1300 1350 -50 -25 0 25 50 75 100 temperature(c) frequency(khz) 100 110 120 130 140 150 160 -50 -25 0 25 50 75 100 temperature( ) soft-start time(us) 2.1 2.2 2.3 2.4 2.5 -50 -25 0 25 50 75 100 temperature( ) input voltage(v) uvlo detector threshold uvlo released voltage rp500x 19 12)ce input voltage vs. temperature 13)lx limit current vs. temperature 14)nch tr.on resistance vs. temperature 15)pch tr. on resistance vs. temperature 16)start-up waveform v in =3.6v v in =5v rp500x151a rp500x151a (c in =c out =ceramic10f?l=4.7h) rp500x111a rp500x251a rp500x151a rp500x151a 0.0 0.2 0.4 0.6 0.8 1.0 -50 -25 0 25 50 75 100 temperature(c) ce input threshold voltage(v) 600 700 800 900 1000 -50-250 255075100 temperature(c) lx limit current(ma) 0 0.1 0.2 0.3 0.4 0.5 0.6 -50 -25 0 25 50 75 100 temperature(c) nchtr. on resistance( ? ) 0 0.1 0.2 0.3 0.4 0.5 0.6 -50 -25 0 25 50 75 100 temperature(c) pchtr. on resistance( ? ) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 100 200 300 400 time(s) output voltage(v) 0 0.5 1 1.5 2 2.5 3 0 100 200 300 400 time(s) output voltage(v) rp500x 20 v in =5v v in =3.6v 17)load transient response i out =0ma to 200ma i out =200ma to0ma i out =100ma to 400ma i out =400ma to100ma rp500x331a rp500x152a rp500x121a (c in =c out =ceramic10f?l=4.7h?v in =3.6v) (c in =c out =ceramic10f?l=4.7h?v in =3.6v) rp500x121a 1.00 1.05 1.10 1.15 1.20 1.25 0 20406080100 time(s) output voltage(v) 0 200 400 600 800 1000 out put current(ma) output voltage output current 1. 05 1. 10 1. 15 1. 20 1. 25 1. 30 0 200 400 600 800 1000 time(s) output voltage(v) 0 200 400 600 800 1000 output current(ma) output voltage output current 0 1 2 3 4 0 100 200 300 400 time(s) output voltage(v) 0 0.5 1 1.5 2 0 100 200 300 400 time(s) out put voltage(v) 1.00 1.05 1.10 1.15 1.20 1.25 0 20406080100 time(s) output voltage(v) 0 200 400 600 800 1000 output current(ma) output voltage output current 1.05 1.10 1.15 1.20 1.25 1.30 0 20406080100 time(s) output voltage(v) 0 200 400 600 800 1000 output current(ma) ou tput v olt age output current rp500x 21 i out =0ma to 200ma i out =200ma to 0ma i out =100ma to 400ma i out =400ma to 100ma i out =0ma to 200ma i out =200ma to 0ma rp500x251a (c in =c out =ceramic10f?l=4.7h?v in =5.0v) rp500x331a (c in =c out =ceramic10f?l=4.7h?v in =5.0v) rp500x251a (c in =c out =ceramic10f?l=4.7h?v in =5.0v) 2.30 2.35 2.40 2.45 2.50 2.55 0 20406080100 time(s) output voltage(v) 0 200 400 600 800 1000 output current(ma) output voltage output current 2.35 2.40 2.45 2.50 2.55 2.60 0 200 400 600 800 1000 time(s) out put voltage(v) 0 200 400 600 800 1000 output current(ma) output voltage output current 2.30 2.35 2.40 2.45 2.50 2.55 0 20406080100 time(s) output voltage(v) 0 200 400 600 800 1000 output current(ma) output voltage output current 2.35 2.40 2.45 2.50 2.55 2.60 0 20406080100 time(s) out put voltage(v) 0 200 400 600 800 1000 output current(ma) ou tput v olt age ou tput current 3.10 3.15 3.20 3.25 3.30 3.35 020406080100 time(s) output voltege(v) 0 200 400 600 800 1000 output current(ma) output voltage output current 3. 15 3. 20 3. 25 3. 30 3. 35 3. 40 0 200 400 600 800 1000 time(s) output voltage(v) 0 200 400 600 800 1000 output current(ma) output voltage output current rp500x 22 i out =100ma to 400ma i out =400ma to 100ma i out =0ma to 200ma i out =200ma to 100ma i out =100ma to 400ma i out =400ma to 100ma rp500x331a (c in =c ou t =ceramic10f?l=4.7h?v in =5.0v) rp500x152a (c in =c ou t =ceramic10f?l=4.7h?v in =3.6v) rp500x152a (c in =c ou t =ceramic10f?l=4.7h?v in =3.6v) 3.10 3.15 3.20 3.25 3.30 3.35 0 20406080100 time(s) output volt age(v) 0 200 400 600 800 1000 output current(ma) output voltage output current 3.15 3.20 3.25 3.30 3.35 3.40 0 20406080100 time(s) out put voltage(v) 0 200 400 600 800 1000 output current(ma) output voltage output current 1.30 1.35 1.40 1.45 1.50 1.55 0 20406080100 time(s) output voltage(v) 0 200 400 600 800 1000 output current(ma) output voltage output current 1.35 1.40 1.45 1.50 1.55 1.60 0 200 400 600 800 1000 time(s) out put voltage(v) 0 200 400 600 800 1000 output current(ma) output voltage output current 1.30 1.35 1.40 1.45 1.50 1.55 0 20406080100 time(s) output voltage(v) 0 200 400 600 800 1000 output current(ma) output voltage output current 1.35 1.40 1.45 1.50 1.55 1.60 020406080100 time(s) output voltage(v) 0 200 400 600 800 1000 output current(ma) output voltage output current |
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