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R5212D series step-down dc/dc converter with vr and reset no.ea-128-0510 1 outline the R5212D is cmos-based pwm step-down dc/dc converter combined with a voltage regulator (vr) and a voltage detector (vd), with low supply current. each of these ics consists of an oscillator, a pwm cont rol circuit, a voltage reference unit, an error amplifier, a soft-start circuit, a current limit circuit, a phase compensat ion circuit, a resistor net for voltage detect circuit, an output driver transistor, and so on. a low ripple, hi gh efficiency step-down dc/dc converter can be easily composed of this ic with some external co mponents, or an inductor, a diode, and capacitors. the oscillator frequency is 1.2mhz, therefore small induc tor and capacitor can be used with this ic. further, this ic equips the under voltage lockout function (uvlo) . if the input voltage becomes equal or less than 2.35v (typ.), the output of dc/dc converter turns off. howeve r, in the a/b version, embedded voltage regulator and detector continue to operate. in the c/d version, ld o output also turns off and only the voltage detector is working. the voltage regulator consists of a voltage reference unit, a resistor net for voltage detect circuit, an error amplifier, an output driver transistor, and so on. the input source voltage of the built-in voltage regulator is v in pin (a/b version) or v out1 pin, the output of dc/dc converter (c/d version). the built-in voltage detector supervises the input voltage and the output is n-channel open drain. power-on reset delay time is also included and interna lly set typically at 12ms (a/c version) or 50ms(b/d version). features ? range of input vo ltage ............................. 3. 0v~5.5v ? built-in soft-start function (typ. 1ms) and built-in power-on reset delay (typ. 12ms or 50ms) ? maximum output current........................... 500ma (dc/dc), 200ma (vr) ? accuracy output volt age .......................... 2.0% ( dc/dc and voltage regulator output) ? accuracy of volt age detector .................... 2.5% ? output voltage (vr)(a/b ve rsion) ............ stepwise setti ng with a step of 0.1v in the range of 2.0v to 3.6v (c/d version) ............ st epwise setting with a step of 0.1v in the range of 1.2v to 3.0v ? output voltage (dc/dc) (a/b version) ..... stepwise setting wi th a step of 0.1v in the range of 1.2v to 3.6v (c/d version) ..... stepwise setting with a step of 0.1v in the range of 2.5v to 3.6v ? output voltage (vd) .................................. stepwis e setting with a step of 0.1v in the range of 3.0v to 4.5v ? package .................................................... hson -6 (t = 0.9mm) applications ? power source for hand-held communication equipment, cd or dvd drives. ? power source for battery-powered equipment.
R5212D 2 block diagrams r5212xxxa/b 6 v in l x gnd v out1 1 4 3 v dout 5 v out2 2 current limit osc soft start u.v.l.o. delay circuit current limit vref vref vref output control logic R5212Dxxxc/d v in l x gnd v out1 5 v out2 v dout current limit & feedback osc vref u.v.l.o. vref vref current limit delay circuit 2 3 1 6 4 output control logic soft start R5212D 3 selection guide in the R5212D series, the output voltage combination for the ics can be selected at the user?s re-quest. the selection can be made with designating the part number as shown below; R5212Dxxx x-tr part number a b c code contents a output voltage combination code number b designation of optional function a: vr input pin = v in pin, vd delay = 12ms b: vr input pin = v in pin, vd delay = 50ms c: vr input pin = dc/dc output, vd delay = typ. 12ms d: vr input pin = dc/dc output, vd delay = typ. 50ms c designation of taping type: re fer to taping specification. R5212D 4 pin configuration hson-6 top view bottom view 654 123 45 6 32 1 pin descriptions pin no symbol pin description 1 l x switching pin (p-channel open-drain output type) 2 gnd ground pin 3 v dout output pin of voltage detector (n-channel open-drain out-put type) 4 v out1 dc/dc converter step-down output monitoring pin 5 v out2 output pin of voltage regulator 6 v in voltage supply pin ? tab in the parts have gnd level. (they are connected to the reverse side of this ic.) do not connect to other wires or land patterns. absolute maximum ratings (gnd = 0v) symbol item rating unit v in v in pin voltage 6.5 v v lx lx pin voltage ? 0.3 ~ v in + 0.3 v v out1 v out1 pin voltage ? 0.3 ~ v in + 0.3 v v out2 v out2 pin voltage ? 0.3 ~ v in + 0.3 v v dout v dout pin voltage ? 0.3 ~ 6.5 v i lx lx pin output current 800 ma i out2 v out2 pin output current 400 ma p d power dissipation (on board) ? 1 900 mw topt operating temperature range ? 40 ~ + 85 c tstg storage temperature range ? 55 ~ + 125 c ? 1 ) for power dissipation please refer to package information to be described. R5212D 5 electrical characteristics ? R5212Dxxxa topt = 25 c symbol item conditions min. typ. max. unit v in operating input voltage 3.0 5.5 v i dd supply current v in = 5.0v, v out1 = 0v 400 800 a v uvlo2 uvlo release voltage 2.35 2.50 2.65 v v uvlohys uvlo detector threshold voltage hysteresis 0.05 0.15 0.25 v ? dc/dc part topt = 25 c symbol item conditions min. typ. max. unit v out1 dc/dc output voltage v in = 5.0v, at no load open loop v out1 0.98 v out1 1.02 v ? v out1 / ? topt dc/dc output voltage temperature coefficient 40 c < = < = c 100 ppm / c fosc oscillator frequency v in = 5.0v 960 1200 1440 khz r lx lx on resistance v in = 5.0v, i lx = 100ma 0.4 0.8 ? i lxleak lx leakage current v in = v out1 = 5.5v, v lx = 0v 0.01 5.00 a i lxlim lx current limit v in = 5.0v 600 800 ma maxduty maximum duty cycle 100 % tstart soft-start time v in = 5.0v 0.35 1.00 3.00 ms ? vr part topt = 25 c symbol item conditions min. typ. max. unit v out2 vr output voltage v in = 5.0v, i out2 = 10ma v out2 0.98 v out2 1.02 v i out2 maximum output current of vr v in = 5.0v 200 ma v reg2 vr load regulation v in ? v out2 = 0v 1ma < = < = = 100ma 0.2 0.3 v i lim2 short current limit v out2 = 0v 50 ma ? v out2 / ? topt vr output voltage temperature coefficient 40 c < = < = c 100 ppm / c ? vd part topt = 25 c symbol item conditions min. typ. max. unit ? v det vd detector threshold ? v det 0.975 ? v det 1.025 v ?? v det / ? topt vd detector threshold temperature coefficient 40 c < = < = c 100 ppm / c v hys hysteresis range ? v det 0.05 v t plh vd output delay time for release v in = v dout =? v det 0.9 to 5.0 3 12 30 ms i doutl v dout ?l? output current v in = 2.0v, i out = 0.1v 2 7 20 ma R5212D 6 ? R5212Dxxxb topt = 25 c symbol item conditions min. typ. max. unit v in operating input voltage 3.0 5.5 v i dd supply current v in = 5.0v, v out1 = 0v 400 800 a v uvlo2 uvlo release voltage 2.35 2.50 2.65 v v uvlohys uvlo detector threshold voltage hysteresis 0.05 0.15 0.25 v ? dc/dc part topt = 25 c symbol item conditions min. typ. max. unit v out1 dc/dc output voltage v in = 5.0v, at no load open loop v out1 0.98 v out1 1.02 v ? v out1 / ? topt dc/dc output voltage temperature coefficient 40 c < = < = c 100 ppm / c fosc oscillator frequency v in = 5.0v 960 1200 1440 khz r lx lx on resistance v in = 5.0v, i lx = 100ma 0.4 0.8 ? i lxleak lx leakage current v in = v out1 = 5.5v, v lx = 0v 0.01 5.00 a i lxlim lx current limit v in = 5.0v 600 850 ma maxduty maximum duty cycle 100 % tstart soft-start time v in = 5.0v 0.35 1.00 3.00 ms ? vr part topt = 25 c symbol item conditions min. typ. max. unit v out2 vr output voltage v in = 5.0v, i out2 = 10ma v out2 0.98 v out2 1.02 v i out2 maximum output current of vr v in = 5.0v 200 ma v reg2 vr load regulation v in ? v out2 = 0v 1ma < = < = = 100ma 0.2 0.3 v i lim2 short current limit v out2 = 0v 50 ma ? v out2 / ? topt vr output voltage temperature coefficient 40 c < = < = c 100 ppm / c ? vd part topt = 25 c symbol item conditions min. typ. max. unit ? v det vd detector threshold ? v det 0.975 ? v det 1.025 v ?? v det / ? topt vd detector threshold temperature coefficient 40 c < = < = c 100 ppm / c v hys hysteresis range ? v det 0.05 v t plh vd output delay time for release v in = v dout =? v det 0.9 to 5.0 3 12 30 ms i doutl v dout ?l? output current v in = 2.0v, v dout = 0.1v 2 7 20 ma R5212D 7 ? R5212Dxxxc topt = 25 c symbol item conditions min. typ. max. unit v in operating input voltage 3.0 5.5 v i dd supply current v in = 5.0v, v out1 = 0v 400 800 a v uvlo2 uvlo release voltage 2.35 2.50 2.65 v v uvlohys uvlo detector threshold voltage hysteresis 0.05 0.15 0.25 v ? dc/dc part topt = 25 c symbol item conditions min. typ. max. unit v out1 dc/dc output voltage v in = 5.0v, at no load open loop v out1 0.98 v out1 1.02 v ? v out1 / ? topt dc/dc output voltage temperature coefficient 40 c < = < = c 100 ppm / c fosc oscillator frequency v in = 5.0v 960 1200 1440 khz r lx lx on resistance v in = 5.0v, i lx = 100ma 0.4 0.8 ? i lxleak lx leakage current v in = v out1 = 5.5v, v lx = 0v 0.01 5.00 a i lxlim lx current limit v in = 5.0v 600 850 ma maxduty maximum duty cycle 100 % tstart soft-start time v in = 5.0v 0.35 1.00 3.00 ms ? vr part topt = 25 c symbol item conditions min. typ. max. unit v out2 vr output voltage v out1 = 3.3v i out2 = 10ma v out2 0.98 v out2 1.02 v i out2 maximum output current of vr v in = 5.0v 200 ma v reg2 vr load regulation v in ? v out2 = 0v 1ma < = < = = 100ma 0.2 0.3 v i lim2 short current limit v out2 = 0v 50 ma ? v out2 / ? topt vr output voltage temperature coefficient 40 c < = < = c 100 ppm / c ? vd part topt = 25 c symbol item conditions min. typ. max. unit ? v det vd detector threshold ? v det 0.975 ? v det 1.025 v ?? v det / ? topt vd detector threshold temperature coefficient 40 c < = < = c 100 ppm / c v hys hysteresis range ? v det 0.05 v t plh vd output delay time for release v in = v dout =? v det 0.9 to 5.0 3 12 30 ms i doutl v dout ?l? output current v in = 2.0v, v dout = 0.1v 2 7 20 ma R5212D 8 ? R5212Dxxxd topt = 25 c symbol item conditions min. typ. max. unit v in operating input voltage 3.0 5.5 v i dd supply current v in = 5.0v, v out1 = 0v 400 800 a v uvlo2 uvlo release voltage 2.35 2.50 2.65 v v uvlohys uvlo detector threshold voltage hysteresis 0.05 0.15 0.25 v ? dc/dc part topt = 25 c symbol item conditions min. typ. max. unit v out1 dc/dc output voltage v in = 5.0v, at no load open loop v out1 0.98 v out1 1.02 v ? v out1 / ? topt dc/dc output voltage temperature coefficient 40 c < = < = c 100 ppm / c fosc oscillator frequency v in = 5.0v 960 1200 1440 khz r lx lx on resistance v in = 5.0v, i lx = 100ma 0.4 0.8 ? i lxleak lx leakage current v in = v out1 = 5.5v, v lx = 0v 0.01 5.00 a i lxlim lx current limit v in = 5.0v 600 850 ma maxduty maximum duty cycle 100 % tstart soft-start time v in = 5.0v 0.35 1.00 3.00 ms ? vr part topt = 25 c symbol item conditions min. typ. max. unit v out2 vr output voltage v out1 = 3.3v i out2 = 10ma v out2 0.98 v out2 1.02 v i out2 maximum output current of vr v in = 5.0v, v out1 = 3.3v 200 ma v reg2 vr load regulation v in ? v out2 = 0v 1ma < = < = = 100ma 0.2 0.3 v i lim2 short current limit v out2 = 0v 50 ma ? v out2 / ? topt vr output voltage temperature coefficient 40 c < = < = c 100 ppm / c ? vd part topt = 25 c symbol item conditions min. typ. max. unit ? v det vd detector threshold ? v det 0.975 ? v det 1.025 v ?? v det / ? topt vd detector threshold temperature coefficient 40 c < = < = c 100 ppm / c v hys hysteresis range ? v det 0.05 v t plh vd output delay time for release v in = v dout =? v det 0.9 to 5.0 10 50 120 ms i doutl v dout ?l? output current v in = 2.0v, v dout = 0.1v 2 7 20 ma R5212D 9 typical application and application hints R5212Dxxxx v out2 v dout v out1 v in gnd l x v out2 v dout v out1 d 1 l 1 c 2 c 1 r 1 c 3 examples of components symbol item (v out1 < = 1.6v) 4.7 h lqh43c series murata 4.7 h vlp5610 series tdk (v out1 > 1.6v) 6.8 h lqh43c series murata l 1 6.8 h vlp5610 series tdk d 1 rb491d(rohm) or ep05q03 (nihon inter) r 1 50k ? c 1 10 f ceramic capacitor c 2 10 f ceramic capacitor c 3 2.2 f ceramic capacitor R5212D 10 when you use these ics, cons ider the following issues; set external components as close as possible to the ic and minimize the connection between the components and the ic. in particular, a capacitor should be connected to between v in and gnd with the minimum connection. make sufficient grounding, and reinforce supplying. a lar ge switching current may flow through the connection of power supply, an inductor and the connection of v out1 . if the impedance of the connection of power supply or ground is high, the voltage level of power supply of the ic fluctuates with the switching current. this may cause unstable operation of the ic. use a capacitor with a capacity of 10 f or more for v in and gnd, and with low esr ce ramic type. in terms of v out1 , use a ceramic capacitor with a capacity of 10 f or more. for v out2 pin, use a ceramic capacitor with a capacitance of 2.2 f or around. choose an inductor that has a small d.c. resistance and large allowable current and which is hard to reach magnetic saturation. if the value of inductance of an inductor is extremely small, the il x , which flows through lx transistor and an inductor, may exceed the absol ute maximum rating at the maximum loading. use an inductor with appropriate inductance. use a diode of a schottky type with high switching speed, and also pay attention to its current capacity. if the spike noise of lx pin is too large, make snub ci rcuit (such as serial connection of cr) between lx and gnd, then the noise will be reduced. the time constant of the cr depends on the actu al pcb, so evaluate it on the actual pcb. if the load current of the voltage regulat or is small, because of the switch ing noise of dc/dc converter, the output voltage of v out2 may be large. to avoid this, use the voltage r egulator with a load current at least 0.5ma. in terms of ldo, the difference between the set out put voltage and input voltage should be 0.5v or more, the performance of power source circuits using t hese 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 eac h component, pcb patterns and the ic do not exceed their respected rated values. R5212D 11 operation of step-down dc/dc converter and output current the step-down dc/dc converter charges energy in the inductor when lx transistor is on, and discharges the energy from the inductor when lx transi stor 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: R5212D 12 ? discontinuous conduction mode and continuous conduction mode the maximum value (ilmax) and the minimum value (ilmin ) current which flow through the inductor is the same as those when lx tr. turns on and when it turns off. the difference between ilmax and il min, which is represented by ? i; ? i = ilmax ? ilmin = v out topen/l = (v in ? v out ) ton/l ........................................................e quation 1 where, t = 1/fosc = ton + toff duty (%) = ton/t 100 = ton fosc 100 topen < = toff in equation a, v out topen/l and (v in ? v out ) ton/l are respectively shown t he change of the current at on, and the change of the current at off. when the output current (i out ) is relatively small, topen < toff as illu strated in the above diagram. in this case, the energy is charged in the inductor during the time peri od of ton and is discharged in its entirely during the time period of toff, therefore ilmin becomes to zero (ilmin = 0). when i out is gradually increased, eventually, topen becomes to toff (topen = toff), and when i out is further increased, ilmin becomes larger than zero (ilmin>0). the former mode is referred to as the discontinuous mode and the latter mode is referred to as continuous mode. in the continuous mode, when equation 1 is solved for ton and assumed that the solution is tonc tonc = t v out /v in .............................................................................................................equat ion 2 when ton |