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general description the max5033 easy-to-use, high-efficiency, high-voltage, step-down dc-dc converter operates from an input volt - age up to 76v and consumes only 270a quiescent cur - rent at no load. this pulse-width modulated (pwm) con - verter operates at a fixed 125khz switching frequency at heavy loads, and automatically switches to pulseskipping mode to provide low quiescent current and high efficiency at light loads. the max5033 includes internal frequency compensation simplifying circuit implementation. the device uses an internal low-onresistance, high-voltage, dmos transistor to obtain high efficiency and reduce overall system cost. this device includes undervoltage lockout, cycle-by-cycle current limit, hiccup-mode output short-circuit protection, and thermal shutdown. the max5033 delivers up to 500ma output current. the output current may be limited by the maximum power dissipation capability of the package. external shutdown is included, featuring 10a (typ) shutdown current. the max5033a/b/c versions have fixed output voltages of 3.3v, 5v, and 12v, respectively, while the max5033d fea - tures an adjustable output voltage, from 1.25v to 13.2v. the max5033 is available in space-saving 8-pin so and 8-pin plastic dip packages and operates over the auto - motive (-40c to +125c) temperature range. applications consumer electronics industrial distributed power features wide 7.5v to 76v input voltage range fixed (3.3v, 5v, 12v) and adjustable (1.25v to 13.2v) voltage versions 500ma output current efficiency up to 94% internal 0.4 high-side dmos fet 270a quiescent current at no load, 10a shutdown current internal frequency compensation fixed 125khz switching frequency thermal shutdown and short-circuit current limit 8-pin so and pdip packages this product is available in both leaded(pb) and lead(pb)-free packages. to order the lead(pb)-free package, add a + after the part number. part temp range pin- package output voltage (v) max5033ausa 0c to +85c 8 so 3.3 max5033aupa 0c to +85c 8 pdip max5033aasa -40c to +125c 8 so max5033busa 0c to +85c 8 so 5.0 max5033bupa 0c to +85c 8 pdip max5033basa -40c to +125c 8 so max5033cusa 0c to +85c 8 so 12 max5033cupa 0c to +85c 8 pdip max5033casa -40c to +125c 8 so max5033dusa 0c to +85c 8 so adj max5033dupa 0c to +85c 8 pdip max5033dasa -40c to +125c 8 so max5033 gnd bst lx v in sgnd fb d150sq100 vd 220h v out 5v, 0.5a v in 7.5v to 76v 47f 0.1f 0.1f 33f on off r1r2 on/off 1 2 3 4 bst vd sgnd fb 8 7 6 5 lxv in gnd on/off max5033 so/pdip pin coniguration max5033 500ma, 76v, high-efficiency, maxpower step-down dc-dc converter 19-2979; rev 5; 4/14 typical application circuit ordering information evaluation kit available downloaded from: http:///
(voltages referenced to gnd, unless otherwise specified.) v in .........................................................................-0.3v to +80v sgnd ....................................................................-0.3v to +0.3v lx.................................................................-0.8v to (v in + 0.3v) bst...............................................................-0.3v to (v in + 10v) bst (transient < 100ns)................................-0.3v to (v in + 15v) bst to lx................................................................-0.3v to +10v bst to lx (transient < 100ns) ................................-0.3v to +15v on/ off ..................................................................-0.3v to +80v vd...........................................................................-0.3v to +12v fb max5033a/max5033b/max5033c...................-0.3v to +15v max5033d.........................................................-0.3v to +12v v out short-circuit duration (v in 40v).....................indefinite vd short-circuit duration..............................................indefinite continuous power dissipation (t a = +70c) 8-pin pdip (derate 9.1mw/c above +70c)..............727mw 8-pin so (derate 5.9mw/c above +70c)..................471mw operating temperature range max5033_u_ _...................................................0c to +85c max5033_a_ _..............................................-40c to +125c storage temperature range.............................-65c to +150c junction temperature.......................................................+150c lead temperature (soldering, 10s)...................................+300c soldering temperature (reflow) so, pdip lead(pb)-free...............................................+260c so, pdip containing lead (pb)....................................+240c (v in = +12v, v on/ off = +12v, i out = 0, t a = 0c to +85c , unless otherwise noted. typical values are at t a = +25c. see the typical operating circuit .) parameter symbol conditions min typ max units input voltage range v in max5033a 7.5 76.0 v max5033b 7.5 76.0 max5033c 15 76 max5033d 7.5 76.0 undervoltage lockout uvlo 5.2 v output voltage v out max5033a, v in = 7.5v to 76v, i out = 20ma to 500ma 3.185 3.3 3.415 v max5033b, v in = 7.5v to 76v, i out = 20ma to 500ma 4.85 5.0 5.15 max5033c, v in = 15v to 76v, i out = 20ma to 500ma 11.64 12 12.36 feedback voltage v fb v in = 7.5v to 76v, max5033d 1.192 1.221 1.250 v eficiency v in = 12v, i load = 500ma, max5033a 86 % v in = 12v, i load = 500ma, max5033b 90 v in = 24v, i load = 500ma, max5033c 94 v in = 12v, v out = 5v, i load = 500ma, max5033d 90 quiescent supply current i q v fb = 3.5v, v in = 7.5v to 76v, max5033a 270 440 a v fb = 5.5v, v in = 7.5v to 76v, max5033b 270 440 v fb = 13v, v in = 15v to 76v, max5033c 270 440 v fb = 1.3v, max5033d 270 440 shutdown current i shdn v on/ off = 0v, v in = 7.5v to 76v 10 45 a peak switch current limit i lim (note 1) 0.95 1.5 2.1 a switch leakage current i ol v in = 76v, v on/ off = 0v, v lx = 0v 1 a max5033 500ma, 76v, high-eficiency, maxpower step-down dc-dc converter www.maximintegrated.com maxim integrated 2 absolute maximum ratings stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. electrical characteristics (max5033_u_ _) downloaded from: http:///
(v in = +12v, v on/ off = +12v, i out = 0, t a = t j = -40c to +125c , unless otherwise noted. typical values are at t a = +25c. see the typical operating circuit .) (note 2) (v in = +12v, v on/ off = +12v, i out = 0, t a = 0c to +85c , unless otherwise noted. typical values are at t a = +25c. see the typical operating circuit .) parameter symbol conditions min typ max units switch on-resistance r ds(on) i switch = 500ma 0.4 0.80 ? pfm threshold i pfm minimum switch current in any cycle 35 65 95 ma fb input bias current i b max5033d -150 +0.01 +150 na on/ off control input on/ off input-voltage threshold v on/ off rising trip point 1.53 1.69 1.85 v on/ off input-voltage hysteresis v hyst 100 mv on/ off input current i on/ off v on/ off = 0v to v in 10 150 na on/ off operating voltage range v on/ off 76 v oscillator oscillator frequency f osc 109 125 135 khz maximum duty cycle d max max5033d 95 % voltage regulator regulator output voltage vd v in = 8.5v to 76v, i l = 0ma 6.9 7.8 8.8 v dropout voltage 7.5v v in 8.5v, i l = 1ma 2.0 v load regulation vd/i vd 0 to 5ma 150 ? package thermal characteristics thermal resistance (junction to ambient) ja so package (jedec 51) 170 c/w dip package (jedec 51) 110 thermal shutdown thermal-shutdown junction temperature t sh +160 c thermal-shutdown hysteresis t hyst 20 c parameter symbol conditions min typ max units input voltage range v in max5033a 7.5 76.0 v max5033b 7.5 76.0 max5033c 15 76 max5033d 7.5 76.0 undervoltage lockout uvlo 5.2 v output voltage v out max5033a, v in = 7.5v to 76v, i out = 20ma to 500ma 3.185 3.3 3.415 v max5033b, v in = 7.5v to 76v, i out = 20ma to 500ma 4.825 5.0 5.175 max5033c, v in = 15v to 76v, i out = 20ma to 500ma 11.58 12 12.42 max5033 500ma, 76v, high-eficiency, maxpower step-down dc-dc converter www.maximintegrated.com maxim integrated 3 electrical characteristics (max5033_a_ _) electrical characteristics (max5033_u_ _) (continued) downloaded from: http:///
(v in = +12v, v on/ off = +12v, i out = 0, t a = t j = -40c to +125c , unless otherwise noted. typical values are at t a = +25c. see the typical operating circuit .) (note 2) note 1: switch current at which the current limit is activated. note 2: all limits at -40c are guaranteed by design, not production tested. parameter symbol conditions min typ max units feedback voltage v fb v in = 7.5v to 76v, max5033d 1.192 1.221 1.250 v eficiency v in = 12v, i load = 500ma, max5033a 86 % v in = 12v, i load = 500ma, max5033b 90 v in = 24v, i load = 500ma, max5033c 94 v in = 12v, v out = 5v, i load = 500ma, max5033d 90 quiescent supply current i q v fb = 3.5v, v in = 7.5v to 76v, max5033a 270 440 a v fb = 5.5v, v in = 7.5v to 76v, max5033b 270 440 v fb = 13v, v in = 15v to 76v, max5033c 270 440 v fb = 1.3v, max5033d 270 440 shutdown current i shdn v on/ off = 0v, v in = 7.5v to 76v 10 45 a peak switch current limit i lim (note 1) 0.95 1.5 2.1 a switch leakage current i ol v in = 76v, v on/ off = 0v, v lx = 0v 1 a switch on-resistance r ds(on) i switch = 500ma 0.4 0.80 ? pfm threshold i pfm minimum switch current in any cycle 35 65 110 ma fb input bias current i b max5033d -150 +0.01 +150 na on/ off control input on/ off input-voltage threshold v on/ off rising trip point 1.50 1.69 1.85 v on/ off input-voltage hysteresis v hyst 100 mv on/ off input current i on/ off v on/ off = 0v to v in 10 150 na on/ off operating voltage range v on/ off 76 v oscillator oscillator frequency f osc 105 125 137 khz maximum duty cycle d max max5033d 95 % voltage regulator regulator output voltage vd v in = 8.5v to 76v, i l = 0ma 6.5 7.8 9.0 v dropout voltage 7.5v v in 8.5v, i l = 1ma 2.0 v load regulation vd/i vd 0 to 5ma 150 ? package thermal characteristics thermal resistance (junction to ambient) ja so package (jedec 51) 170 c/w dip package (jedec 51) 110 thermal shutdown thermal-shutdown junction temperature t sh +160 c thermal-shutdown hysteresis t hyst 20 c max5033 500ma, 76v, high-eficiency, maxpower step-down dc-dc converter www.maximintegrated.com maxim integrated 4 electrical characteristics (max5033_a_ _) (continued) downloaded from: http:///
(v in = 12v, v on/ off = 12v, t a = -40c to +125c, unless otherwise noted. typical values are at t a = +25c. see the typical operating circuit , if applicable.) v out vs. temperature (max5033basa, v out = 5v) max5033 toc02 temperature (c) v out (v) 4.95 5.00 5.05 5.104.90 i out = 0.1a i out = 0.5a 100 50 0 -50 150 -25 25 75 125 line regulation (max5033casa, v out = 12v) max5033 toc03 input voltage (v) v out (v) 50 60 70 40 30 20 11.9 12.0 12.1 12.2 12.3 12.411.8 10 80 i out = 0a i out = 0.5a line regulation (max5033basa, v out = 5v) max5033 toc04 input voltage (v) v out (v) 46 56 66 36 26 16 4.95 5.00 5.05 5.104.90 6 76 i out = 0a i out = 0.5a load regulation (max5033casa, v out = 12v) max5033 toc05 i load (ma) v out (v) 400 300 200 100 11.9 12.0 12.1 12.2 12.3 12.411.8 0 500 v in = 24v v in = 76v load regulation (max5033basa, v out = 5v) max5033 toc06 i load (ma) v out (v) 400 300 200 100 4.95 5.00 5.05 5.104.90 0 500 v in = 7.5v, 24v v in = 76v efficiency vs. load current (max5033basa, v out = 5v) max5033 toc07 load current (ma) efficiency (%) 400 300 200 100 30 5040 20 10 7060 100 9080 0 0 500 v in = 7.5v v in = 12v v in = 24v v in = 48v v in = 76v v out vs. temperature (max5033casa, v out = 12v) max5033 toc01 temperature (c) v out (v) 11.9 12.0 12.1 12.2 12.3 12.411.8 100 50 0 -50 150 -25 25 75 125 i out = 0.1a i out = 0.5a efficiency vs. load current (max5033casa, v out = 12v) max5033 toc08 load current (ma) efficiency (%) 400 300 200 100 30 5040 20 10 7060 100 9080 0 0 500 v in = 15v v in = 24v v in = 48v v in = 76v output current limit vs. temperature max5033 toc09 temperature (c) output current limit (a) 0.8 1.1 1.4 1.7 2.00.5 max5033basa5% drop in v out 100 50 0 -50 150 -25 25 75 125 max5033 500ma, 76v, high-eficiency, maxpower step-down dc-dc converter maxim integrated 5 www.maximintegrated.com typical operating characteristics downloaded from: http:///
(v in = 12v, v on/ off = 12v, t a = -40c to +125c, unless otherwise noted. typical values are at t a = +25c. see the typical operating circuit , if applicable.) output current limit vs. input voltage max5033 toc10 input voltage (v) output current limit (a) 66 56 46 36 26 16 0.8 1.1 1.4 1.7 2.00.5 6 76 max5033basav out = 5v 5% drop in v out quiescent supply current vs. temperature max5033 toc11 temperature (c) quiescent supply current (a) 240 280 320 360 400200 100 50 0 -50 150 -25 25 75 125 quiescent supply current vs. input voltage max5033 toc12 input voltage (v) quiescent supply current (a) 230 260 290 320 350200 66 46 26 6 16 36 56 76 shutdown current vs. temperature max5033 toc13 temperature (c) shutdown current (a) 5 10 15 20 25 0 100 50 0 -50 150 -25 25 75 125 shutdown current vs. input voltage max5033 toc14 input voltage (v) shutdown current (a) 5 10 15 20 25 0 66 46 26 6 16 36 56 76 output voltage vs. input voltage max5033 toc15 v in (v) v out (v) 12 9 6 3 3 6 9 12 15 0 0 15 max5033casav out = 12v v on/off = v in i out = 0.3a i out = 0.5a max5033basa load-transient response max5033 toc16 400s/div b a a: v out , 200mv/div, ac-coupled b: i out , 500ma/div, 100ma to 500ma v out = 5v max5033basa load-transient response max5033 toc17 400s/div b a a: v out , 100mv/div, ac-coupled b: i out , 200ma/div, 100ma to 250ma v out = 5v max5033basa load-transient response max5033 toc18 400s/div b a a: v out , 100mv/div, ac-coupled b: i out , 500ma/div, 250ma to 500ma v out = 5v max5033 500ma, 76v, high-eficiency, maxpower step-down dc-dc converter maxim integrated 6 www.maximintegrated.com typical operating characteristics (continued) downloaded from: http:///
(v in = 12v, v on/ off = 12v, t a = -40c to +125c, unless otherwise noted. typical values are at t a = +25c. see the typical operating circuit , if applicable.) max5033basa lx waveforms max5033 toc19 4ms/div b 0 a a: switch voltage (lx pin) 20v/div, v in = 48v b: inductor current, 200ma/div, (i out = 500ma) max5033basa lx waveforms max5033 toc20 4s/div b0 a0 a: switch voltage, 20v/div, v in = 48v b: inductor current, 100ma/div (i out = 30ma) max5033basa lx waveforms max5033 toc21 4s/div b a a: switch voltage (lx pin), 20v/div, v in = 48v b: inductor current, 100ma/div (i out = 0) 0 0 max5033basa startup waveform (i o = 0) max5033 toc22 1ms/div b a a: v on/off , 2v/div b: v out , 2v/div max5033basa startup waveform (i o = 0.5a) max5033 toc23 1ms/div b a a: v on/off , 2v/div b: v out , 2v/div peak switch current limit vs. input voltage max5033 toc24 input voltage (v) peak switch current limit (a) 56 66 46 36 26 16 0.8 1.1 1.4 1.7 2.00.5 6 76 max5033basav out = 5v 5% drop in v out max5033 500ma, 76v, high-eficiency, maxpower step-down dc-dc converter maxim integrated 7 www.maximintegrated.com typical operating characteristics (continued) downloaded from: http:///
pin name function 1 bst boost capacitor connection. connect a 0.1f ceramic capacitor from bst to lx. 2 vd internal regulator output. bypass vd to gnd with a 0.1f ceramic capacitor. 3 sgnd internal connection. sgnd must be connected to gnd. 4 fb output sense feedback connection. for ixed output voltage (max5033a, max5033b, max5033c), connect fb to v out . for adjustable output voltage (max5033d), use an external resistive voltage- divider to set v out . v fb regulating set point is 1.22v. 5 on/ off shutdown control input. pull on/ off low to put the device in shutdown mode. drive on/ off high for normal operation. 6 gnd ground. 7 v in input voltage. bypass v in to gnd with a low-esr capacitor as close to the device as possible. 8 lx source connection of internal high-side switch. enable lx bst v in on/off v ref regulator (for driver) regulator (for analog) osc ramp high-side current sense i ref-pfm i ref-lim cpfm 1.69v cilim fb x1 v ref eamp control logic cpwm vd gnd r h r l clk sgnd max5033 type 3 compensation thermal shutdown ramp max5033 500ma, 76v, high-eficiency, maxpower step-down dc-dc converter www.maximintegrated.com maxim integrated 8 pin descriptionsimpliied block diagram downloaded from: http:///
detailed description the max5033 step-down dc-dc converter operates from a 7.5v to 76v input voltage range. a unique volt - age- mode control scheme with voltage feed-forward and an internal switching dmos fet provides high efficiency over a wide input voltage range. this pulse - width modulated converter operates at a fixed 125khz switching frequency. the device also features automatic pulse-skipping mode to provide low quiescent current and high efficiency at light loads. under no load, the max5033 consumes only 270a, and in shutdown mode, consumes only 10a. the max5033 also features undervoltage lockout, hiccup-mode output shortcircuit protection, and thermal shutdown. shutdown mode drive on/ off to ground to shut down the max5033. shutdown forces the internal power mosfet off, turns off all internal circuitry, and reduces the v in supply cur - rent to 10a (typ). the on/ off rising threshold is 1.69v (typ). before any operation begins, the voltage at on/ off must exceed 1.69v (typ). the on/ off input has 100mv hysteresis.undervoltage lockout (uvlo) use the on/ off function to program the uvlo threshold at the input. connect a resistive voltage-divider from v in to gnd with the center node to on/ off as shown in figure 1. calculate the threshold value by using the fol - lowing formula: uvlo(th) r1 v 1 1.85v r2 ?? =+ ???? the minimum recommended v uvlo(th) is 6.5v, 7.5v, and 13v for the output voltages of 3.3v, 5v, and 12v, respectively. the recommended value for r2 is less than 1m. if the external uvlo threshold-setting divider is not used, an internal undervoltage-lockout feature monitors the supply voltage at v in and allows operation to start when v in rises above 5.2v (typ). this feature can be used only when v in rise time is faster than 2ms. for slower v in rise time, use the resistive divider at on/ off . boost high-side gate drive (bst) connect a flying bootstrap capacitor between lx and bst to provide the gate-drive voltage to the high-side n-channel dmos switch. the capacitor is alternately charged from the internally regulated output-voltage vd and placed across the high-side dmos driver. use a 0.1f, 16v ceramic capacitor located as close to the device as possible. on startup, an internal low-side switch connects lx to ground and charges the bst capacitor to vd. once the bst capacitor is charged, the internal low-side switch is turned off and the bst capacitor voltage provides the necessary enhancement voltage to turn on the high-side switch. thermal-overload protection the max5033 features integrated thermal-overload pro - tection. thermal-overload protection limits total power dis - sipation in the device, and protects the device in the event of a fault condition. when the die temperature exceeds +160c, an internal thermal sensor signals the shutdown logic, turning off the internal power mosfet and allow - ing the ic to cool. the thermal sensor turns the internal power mosfet back on after the ics die temperature cools down to +140c, resulting in a pulsed output under continuous thermaloverload conditions. applications information setting the output voltage the max5033a/b/c have preset output voltages of 3.3v, 5.0v, and 12v, respectively. connect fb to the preset output voltage (see the typical operating circuit). the max5033d offers an adjustable output voltage. set the output voltage with a resistive voltage-divider connect - ed from the circuits output to ground (figure 1). connect the center node of the divider to fb. choose r4 less than 15k, then calculate r3 as follows: out (v 1.22) r3 r4 1.22 ? = figure 1. adjustable output voltage max5033d gnd bst lx v in sgnd fb d150sq100 vd 220h v out 5v, 0.5a v in 7.5v to 76v 47f 0.1f 0.1f c out 33f r1r2 r3 41.2k ? r4 13.3k ? on/off max5033 500ma, 76v, high-eficiency, maxpower step-down dc-dc converter www.maximintegrated.com maxim integrated 9 downloaded from: http:///
the max5033 features internal compensation for opti - mum closed-loop bandwidth and phase margin. with the preset compensation, it is strongly advised to sense the output immediately after the primary lc. inductor selection the choice of an inductor is guided by the voltage differ - ence between v in and v out , the required output current, and the operating frequency of the circuit. use an inductor with a minimum value given by: in out outmax sw (v v ) d l 0.3 i f ? = where: d = v out /v in , i outmax is the maximum output current required, and f sw is the operating frequency of 125khz. use an inductor with a maximum saturation cur - rent rating equal to at least the peak switch current limit (i lim ). use inductors with low dc resistance for higher efficiency. selecting a rectiier the max5033 requires an external schottky rectifier as a freewheeling diode. connect this rectifier close to the device using short leads and short pc board traces. choose a rectifier with a continuous current rating greater than the highest expected output current. use a rectifier with a voltage rating greater than the maximum expected input voltage, v in . use a low forward-voltage schottky rectifier for proper operation and high efficiency. avoid higher than necessary reverse-voltage schottky rectifiers that have higher forward-voltage drops. use a schottky rectifier with forward-voltage drop (v fb ) less than 0.45v at +25c and maximum load current to avoid forward biasing of the internal body diode (lx to ground). internal body-diode conduction may cause excessive junction temperature rise and thermal shutdown. use table 1 to choose the proper rectifier at different input voltages and output current. input bypass capacitor the discontinuous input-current waveform of the buck converter causes large ripple currents in the input capaci - tor. the switching frequency, peak inductor current, and the allowable peak-to-peak voltage ripple that reflects back to the source dictate the capacitance requirement. the max5033 high switching frequency allows the use of smaller-value input capacitors. the input ripple is comprised of v q (caused by the capacitor discharge) and v esr (caused by the esr of the capacitor). use low-esr aluminum electrolytic capacitors with high ripple-current capability at the input. assuming that the contribution from the esr and capaci - tor discharge is equal to 90% and 10%, respectively, calculate the input capacitance and the esr required for a specified ripple using the following equations: esr in l out out in q sw in out out l in sw out v esr i i 2 i d(1 d) c vf where : (v v ) v i vf l v d ? = ? ?? + ???? ? = ? ? ?= = in v i out is the maximum output current of the converter and f sw is the oscillator switching frequency (125khz). for example, at v in = 48v and v out = 3.3v, the esr and input capacitance are calculated for the input peak-topeak ripple of 100mv or less, yielding an esr and capacitance value of 130m and 27f, respectively. low-esr, ceramic, multilayer chip capacitors are rec - ommended for size-optimized application. for ceramic capacitors, assume the contribution from esr and capac - itor discharge is equal to 10% and 90%, respectively. the input capacitor must handle the rms ripple current without significant rise in temperature. the maximum capacitor rms current occurs at about 50% duty cycle. table 1. diode selection v in (v) diode part number manufacturer 7.5 to 36 15mq040n ir b240a diodes incorporated b240 central semiconductor mbrs240, mbrs1540 on semiconductor 7.5 to 56 30bq060 ir b360a diodes incorporated cmsh3-60 central semiconductor mbrd360, mbr3060 on semiconductor 7.5 to 76 50sq100, 50sq80 ir mbrm5100 diodes incorporated max5033 500ma, 76v, high-eficiency, maxpower step-down dc-dc converter www.maximintegrated.com maxim integrated 10 downloaded from: http:///
ensure that the ripple specification of the input capacitor exceeds the worst-case capacitor rms ripple current. use the following equations to calculate the input capaci - tor rms current: 22 crms prms avgin i i i = ? where : ( ) ( ) 22 prms pk dc pk dc out out avgin in ll pk out dc out out in d i i i i i 3 vi i v ii i i , i i 22 v and d v = + + = ?? =+=? = i prms is the input switch rms current, i avgin is the input average current, and is the converter efficiency. the esr of aluminum electrolytic capacitors increases significantly at cold temperatures. use a 1f or greater value ceramic capacitor in parallel with the aluminum electrolytic input capacitor, especially for input voltages below 8v. output filter capacitor the worst-case peak-to-peak and rms capacitor ripple current, allowable peak-to-peak output ripple voltage, and the maximum deviation of the output voltage during load steps determine the capacitance and the esr require - ments for the output capacitors. the output capacitance and its esr form a zero, which improves the closed-loop stability of the buck regulator. choose the output capacitor so the esr zero frequency (f z ) occurs between 20khz to 40khz. use the following equation to verify the value of f z . capacitors with 100m to 250m esr are recommended to ensure the closed - loop stability while keeping the output ripple low. z out out 1 f 2 c esr = the output ripple is comprised of v oq (caused by the capacitor discharge) and v oesr (caused by the esr of the capacitor). use low-esr tantalum or aluminum electrolytic capacitors at the output. assuming that the contributions from the esr and capacitor discharge equal 80% and 20%, respectively, calculate the output capaci - tance and the esr required for a specified ripple using the following equations: oesr out l l out oq sw v esr i i c 2.2 v f ? = ? ? ? the max5033 has an internal soft-start time (t ss ) of 400s. it is important to keep the output rise time at startup below t ss to avoid output overshoot. the output rise time is directly proportional to the output capacitor. use 68f or lower capacitance at the output to control the overshoot below 5%. in a dynamic load application, the allowable deviation of the output voltage during the fast-transient load dictates the output capacitance value and the esr. the output capacitors supply the step load current until the controller responds with a greater duty cycle. the response time (t response ) depends on the closedloop bandwidth of the converter. the resistive drop across the capacitor esr and capacitor discharge cause a voltage droop dur - ing a step load. use a combination of low-esr tantalum and ceramic capacitors for better transient load and ripple/noise performance. keep the maximum output- voltage deviation above the tolerable limits of the elec - tronics being powered. assuming a 50% contribution from the output capacitance discharge and the esr drop, use the following equations to calculate the required esr and capacitance value: oesr out step step response out oq v esr i it c v ? = = ? where i step is the load step and t response is the response time of the controller. controller response time is approximately one-third of the reciprocal of the closed- loop unity-gain bandwidth, 20khz (typ). pcb layout considerations proper pcb layout is essential. minimize ground noise by connecting the anode of the schottky rectifier, the input bypass-capacitor ground lead, and the output filter-capacitor ground lead to a single point (star-ground configuration). a ground plane is required. minimize lead lengths to reduce stray capacitance, trace resistance, and radiated noise. in particular, place the schottky rectifier diode right next to the device. also, place bst and vd bypass capacitors very close to the device. use the pcb copper plane connecting to v in and lx for heatsinking. max5033 500ma, 76v, high-eficiency, maxpower step-down dc-dc converter www.maximintegrated.com maxim integrated 11 downloaded from: http:///
figure 2. fixed output voltages table 2. typical external components selection (circuit of figure 2) v in (v) v out (v) i out (a) external components 7.5 to 76 3.3 0.5 c in = 47f, panasonic, eevfk2a470q c out = 47f, vishay sprague, 594d476x_016c2t c bst = 0.1f, 0805 r1 = 1m 1%, 0805r2 = 384k 1%, 0805 d1 = 50sq100, ir l1 = 150h, coilcraft inc., do5022p-154 7.5 to 76 5 0.5 c in = 47f, panasonic, eevfk2a470q c out = 33f, vishay sprague, 594d336x_016c2t c bst = 0.1f, 0805 r1 = 1m 1%, 0805r2 = 384k 1%, 0805 d1 = 50sq100, ir l1 = 220h, coilcraft inc., do5022p-224 15 to 76 12 0.5 c in = 47f, panasonic, eevfk2a470q c out = 15f, vishay sprague, 594d156x_025c2t c bst = 0.1f, 0805 r1 = 1m 1%, 0805r2 = 384k 1%, 0805 d1 = 50sq100, ir l1 = 330h, coilcraft inc., do5022p-334 max5033 gnd bst lx v in sgnd fb d1 vd l1 v out v in c in 0.1f 0.1f c out r1r2 on/off max5033 500ma, 76v, high-eficiency, maxpower step-down dc-dc converter www.maximintegrated.com maxim integrated 12 application circuit downloaded from: http:///
table 2. typical external components selection (circuit of figure 2) (continued) v in (v) v out (v) i out (a) external components 9 to 14 3.3 0.5 c in = 100f, panasonic, eevfk1e101p c out = 47f, vishay sprague, 594d476x_016c2t c bst = 0.1f, 0805 r1 = 1m 1%, 0805r2 = 274k 1%, 0805 d1 = b220/a, diodes incorporated l1 = 150h, coilcraft inc., do5022p-154 5 0.5 c in = 100f, panasonic, eevfk1e101p c out = 33f, vishay sprague, 594d336x_016c2t c bst = 0.1f, 0805 r1 = 1m 1%, 0805r2 = 274k 1%, 0805 d1 = b220/a, diodes incorporated l1 = 220h, coilcraft inc., do5022p-224 18 to 36 3.3 0.5 c in = 100f, panasonic, eevfk1h101p c out = 47f, vishay sprague, 594d476x_016c2t c bst = 0.1f, 0805 r1 = 1m 1%, 0805r2 = 130k 1%, 0805 d1 = b240/a, diodes incorporated l1 = 150h, coilcraft inc., do5022p-154 5 0.5 c in = 100f, panasonic, eevfk1h101p c out = 33f, vishay sprague, 594d336x_016c2t c bst = 0.1f, 0805 r1 = 1m 1%, 0805r2 = 130k 1%, 0805 d1 = b240/a, diodes incorporated l1 = 220h, coilcraft inc., do5022p-224 12 0.5 c in = 100f, panasonic, eevfk1h101p c out = 15f, vishay sprague, 594d156x_025c2t c bst = 0.1f, 0805 r1 = 1m 1%, 0805r2 = 130k 1%, 0805 d1 = b240/a, diodes incorporated l1 = 330h, coilcraft inc., do5022p-334 max5033 500ma, 76v, high-eficiency, maxpower step-down dc-dc converter www.maximintegrated.com maxim integrated 13 downloaded from: http:///
table 3. component suppliers figure 3. load temperature monitoring with on/ off (requires accurate v in ) supplier phone fax website avx 843-946-0238 843-626-3123 www.avxcorp.com coilcraft 847-639-6400 847-639-1469 www.coilcraft.com diodes incorporated 805-446-4800 805-446-4850 www.diodes.com nichicon 858-824-1515 858-824-1525 www.nichicon.com panasonic 714-373-7366 714-737-7323 www.panasonic.com sanyo 619-661-6835 619-661-1055 www.sanyo.com tdk 847-803-6100 847-390-4405 www.component.tdk.com vishay 402-563-6866 402-563-6296 www.vishay.com max5033 c in 47f c out 33f l1 220h fb v out 5v at 0.5a bst lx sgnd 0.1f 0.1f gnd v in 12v v in ptc* rt ct d1b240 vd *locate ptc as close to heat-dissipating components as possible. on/off max5033 500ma, 76v, high-eficiency, maxpower step-down dc-dc converter www.maximintegrated.com maxim integrated 14 downloaded from: http:///
figure 4. dual-sequenced dc-dc converters (startup delay determined by r1/r1, ct/ct and rt/rt) max5033b c in 47f c out 68f l1 220h fb v out 5v at 0.5a bst lx sgnd 0.1f 0.1f gnd v in 7.5v to 36v v in r1 rt ct d1b240 vd on/off max5033a c' in 68f c' out 68f l1' 150h fb v' out 3.3v at 0.5a bst lx sgnd 0.1f 0.1f gnd v in r1' rt' ct' d1'b240 vd on/off max5033 500ma, 76v, high-eficiency, maxpower step-down dc-dc converter www.maximintegrated.com maxim integrated 15 chip information process: bicmos downloaded from: http:///
package type package code outline no. land pattern no. 8 pdip p8+3 21-0043 8 so s8+5 21-0041 90-0096 max5033 500ma, 76v, high-eficiency, maxpower step-down dc-dc converter www.maximintegrated.com maxim integrated 16 package information for the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages . note that a +, #, or - in the package code indicates rohs status only. package drawings may show a different su ffix character, but the drawing pertains to the package regardless of rohs status. downloaded from: http:///
revision number revision date description pages changed 0 9/03 initial release 1 5/04 new product update 1C7, 10 2 6/04 removed future product asterisk and made speciication changes 1, 2, 3 3 1/07 modiied absolute maximum ratings speciications 2 4 4/10 corrected inconsistencies in absolute maximum ratings and electrical characteristics table 1, 2, 3, 4, 17 5 4/14 no /v opns; removed automotive reference in applications section 1 maxim integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim integrated product. no circuit patent licenses are implied. maxim integrated reserves the right to change the circuitry and speciications without n otice at any time. the parametric values (min and max limits) shown in the electrical characteristics table are guaranteed. other parametric values quoted in this data sheet are provided for guidance. maxim integrated and the maxim integrated logo are trademarks of maxim integrated products, inc. max5033 500ma, 76v, high-eficiency, maxpower step-down dc-dc converter ? 2014 maxim integrated products, inc. 17 revision history for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim integrateds website at www.maximintegrated.com. downloaded from: http:///

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