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for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. general description the max618 cmos, pwm, step-up dc-dc converter generates output voltages up to 28v and accepts inputs from +3v to +28v. an internal 2a, 0.3 ? switch eliminates the need for external power mosfets while supplying output currents up to 500ma or more. a pwm control scheme combined with idle mode? oper- ation at light loads minimizes noise and ripple while maximizing efficiency over a wide load range. no-load operating current is 500a, which allows efficiency up to 93%. a fast 250khz switching frequency allows the use of small surface-mount inductors and capacitors. a shut- down mode extends battery life when the device is not in use. adaptive slope compensation allows the max618 to accommodate a wide range of input and output voltages with a simple, single compensation capacitor. the max618 is available in a thermally enhanced 16- pin qsop package that is the same size as an industry- standard 8-pin so but dissipates up to 1w. an evaluation kit (max618evkit) is available to help speed designs. applications automotive-powered dc-dc converters industrial +24v and +28v systems lcd displays palmtop computers features adjustable output voltage up to +28v up to 93% efficiency wide input voltage range (+3v to +28v) up to 500ma output current at +12v 500 a quiescent supply current 3 a shutdown current 250khz switching frequency small 1w, 16-pin qsop package max618 28v, pwm, step-up dc-dc converter ________________________________________________________________ maxim integrated products 1 16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8 gnd gnd pgnd pgnd pgnd gnd vl in gnd top view max618 qsop lx lx comp lx shdn fb gnd + pgnd lx fb vl v out up to 28v comp in shdn gnd v in 3v to 28v max618 typical operating circuit + denotes a lead(pb)-free/rohs-compliant package. 19-1462; rev 1; 12/09 pin configuration ordering information idle mode is a trademark of maxim integrated products. 16 qsop pin-package temp. range -40c to +85c max618eee+ part evaluation kit available
max618 28v, pwm, step-up dc-dc converter 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v in = +6v, pgnd = gnd, c vl = 4.7f, t a = 0c to +85c , unless otherwise noted. typical values are at t a = +25c.) stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. in to gnd ...............................................................-0.3v to +30v lx to gnd ..............................................................-0.3v to +30v vl to gnd ................................................................-0.3v to +6v shdn , comp, fb to gnd ............................-0.3v to (vl + 0.3v) pgnd to gnd.....................................................................0.3v continuous power dissipation (t a = +70c) (note 1) 16-pin qsop (derate 15mw/c above +70c)...................1w operating temperature range ...........................-40c to +85c junction temperature ......................................................+150c storage temperature range .............................-65c to +150c soldering temperature (reflow) .......................................+260c note 1: with part mounted on 0.9 in. 2 of copper. shutdown supply current i in 38 a v in = 28v, v fb = 1.6v, shdn = gnd maximum duty cycle dc 90 95 % parameter symbol min typ max units vl output voltage v vl 2.9 3.05 3.2 v supply current, full load i in 2.5 3.5 ma supply current, full load, vl connected to in i in 5 6.5 ma vl load regulation ? v vl 25 40 mv vl undervoltage lockout 2.58 2.7 2.8 v fb set voltage v fb 1.47 1.5 1.53 v fb input bias current i fb 150 na supply current, no load input voltage v in 328 v i in 500 700 a line regulation ? v out 0.01 0.08 %/v load regulation ? v out 0.2 % lx voltage v lx 28 v lx switch current limit i lxon 1.7 2.2 2.7 a idle mode current-limit threshold 0.25 0.35 0.45 a lx on-resistance r lxon 0.3 0.6 ? lx leakage current i lxoff 0.02 10 a comp maximum output current i comp 100 200 a comp current vs. fb voltage transconductance 0.8 1 mmho shdn input logic low v il 0.8 v shdn input logic high v ih 2.0 v shutdown input current 1 a switching frequency f 200 250 300 khz conditions v in = 3v to 6v, v out = 12v v in = 3.5v or 28v, no load v out = 12v, i load = 10ma to 500ma v in = 3.4v to 28v, v fb = 1.4v, shdn = vl, v vl < v in v in = 3v to 5.5v, v fb = 1.4v, shdn = vl = in i load = 0 to 2ma, v fb = 1.6v rising edge, 1% hysteresis pwm mode v fb = 1.6v v lx = 28v fb = gnd v in = 3v to 28v, v fb = 1.6v, shdn = vl ? fb = 0.1v shdn = gnd or vl
max618 28v, pwm, step-up dc-dc converter _______________________________________________________________________________________ 3 electrical characteristics (v in = +6v, pgnd = gnd, c vl = 4.7f, t a = -40c to +85c , unless otherwise noted.) (note 2) 100 0 0.1 1 10 100 1000 efficiency vs. output current (v out = 12v) 20 30 10 max618 toc01 output current (ma) efficiency (%) 40 50 60 70 80 90 v in = 8v v in = 5v v in = 3v 100 0 0.1 1 10 100 1000 efficiency vs. output current (v out = 28v) 20 30 10 max618 toc02 output current (ma) efficiency (%) 40 50 60 70 80 90 v in = 12v v in = 5v v in = 3v typical operating characteristics (circuit of figure 1, t a = +25c.) note 2: specifications to -40c are guaranteed by design, not production tested. parameter symbol min typ max units supply current, full load i in 4 ma supply current, full load, vl connected to in i in 7.5 ma supply current shutdown i in 10 a vl output voltage v vl 2.85 3.3 v supply current, no load input voltage v in 328 v i in 800 a vl undervoltage lockout v vl 2.55 2.85 v fb set voltage v fb 1.455 1.545 v lx voltage range v lxon 28 v lx switch current limit i lxon 1.4 3 a lx on-resistance r lxon 0.6 ? switching frequency f 188 312 khz conditions rising edge, 1% hysteresis v in = 3.4v to 28v, v fb = 1.4v, shdn = vl, vl < v in v in = 3v to 5.5, v fb = 1.4v, shdn = vl = in v in = 28v, v fb = 1.6v, shdn = gnd pwm mode v in = 3.5v or 28v, no load v in = 3v to 28v, v fb = 1.6v, shdn = vl
max618 28v, pwm, step-up dc-dc converter 4 _______________________________________________________________________________________ 0 v out (100mv/div) v lx (10v/div) i l (1a/div) medium-load switching waveforms max618 toc07 v in = 5v, v out = 12v, i out = 200ma 2 s/div 0 v out (100mv/ div) v lx (10v/div) i l (1a/div) heavy-load switching waveforms max618 toc08 v in = 5v, v out = 12v, i out = 500ma 2 s/div 3v 6v v out (50mv/div) v in (5v/div) line-transient response max618 toc09 i out = 200ma, v out = 12v 2ms/div typical operating characteristics (continued) (circuit of figure 1, t a = +25c.) 0 v out (200mv/div) i out (100ma/div) load-transient response max618 toc10 v in = 5v, v out = 12v 5ms/div 5v 12v 0 shdn (2v/div) v out (2v/div) shutdown response max618 toc11 v in = 5v, v out = 12v, i load = 500ma 500 s/div 0 0.4 0.2 0.6 1.2 1.4 1.0 0.8 1.6 2 4567 389101112 maximum output current vs. input voltage max618 toc12 input voltage (v) maximum output current (a) v out = 12v 0.40 0.45 0.55 0.50 0.60 0.65 010 5 15202530 no-load supply current vs. input voltage max618 toc04 input voltage (v) supply cirrent (ma) 300 400 350 500 450 550 600 650 700 -50 -10 10 -30 30507090110 supply current vs. temperature max618 toc05 temperature ( c) supply current ( a) v in = 8v v in = 5v v in = 3v includes capacitor leakage current 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 212 7 17222732 shutdown current vs. supply voltage max618 toc06 supply voltage (v) shutdown current ( a)
_______________ detailed description the max618 pulse-width modulation (pwm) dc-dc converter with an internal 28v switch operates in a wide range of dc-dc conversion applications including boost, sepic, and flyback configurations. the max618 uses fixed-frequency pwm operation and maxims pro- prietary idle mode control to optimize efficiency over a wide range of loads. it also features a shutdown mode to minimize quiescent current when not in operation. pwm control scheme and idle mode operation the max618 combines continuous-conduction pwm operation at medium to high loads and idle mode oper- ation at light loads to provide high efficiency over a wide range of load conditions. the max618 control scheme actively monitors the output current and auto- matically switches between pwm and idle mode to optimize efficiency and load regulation. figure 2 shows a functional diagram of the max618s control scheme. the max618 normally operates in low-noise, continu- ous-conduction pwm mode, switching at 250khz. in pwm mode, the internal mosfet switch turns on with each clock pulse. it remains on until either the error comparator trips or the inductor current reaches the 2a switch-current limit. the error comparator compares the feedback-error signal, current-sense signal, and slope- compensation signal in one circuit block. when the switch turns off, energy transfers from the inductor to max618 28v, pwm, step-up dc-dc converter _______________________________________________________________________________________________________ 5 pin description pgnd ecb1q503l lx fb 1 f 4.7 f v l c out c p r1 r2 c ind v out in l shdn gnd comp up to 28v 3v to 28v v in c comp max618 v out r1 r2 c ind lc out c p c comp 8v 402k ? 93.1k ? 150 f12 h 150 f 220pf 0.082 f 12v 715k ? 100k ? 100 f15 h 100 h 56pf 0.1 f 28v 574k ? 32.4k ? 86 f39 h33 f 47pf 0.47 f figure 1. single-supply operation feedback input. connect a resistor-divider network to set v out . fb threshold is 1.5v. fb 7 ldo regulator supply input. in accepts inputs up to +28v. bypass to gnd with a 1f ceramic capacitor as close to pins 10 and 12 as possible. in 10 internal 3.1v ldo regulator output. bypass to gnd with a 4.7f capacitor. vl 11 power ground, source of internal n-channel switch pgnd 13, 14, 15 compensation input. bypass to gnd with the capacitance value shown in table 2. comp 6 shutdown input. a logic low puts the max618 in shutdown mode and reduces supply current to 3a. shdn must not exceed vl. in shutdown, the output falls to v in less one diode drop. shdn 5 pin drain of internal n-channel switch. connect the inductor between in and lx. lx 2, 3, 4 ground gnd 1, 8, 9, 12, 16 function name
max618 the output capacitor. output current is limited by the 2a mosfet current limit and the max618s package power-dissipation limit. see the maximum output current section for details. in idle mode, the max618 improves light-load efficien- cy by reducing inductor current and skipping cycles to reduce the losses in the internal switch, diode, and inductor. in this mode, a switching cycle initiates only when the error comparator senses that the output volt- age is about to drop out of regulation. when this occurs, the nmos switch turns on and remains on until the inductor current exceeds the nominal 350ma idle mode current limit. refer to table 1 for an estimate of load currents at which the max618 transitions between pwm and idle mode. compensation scheme although the higher loop gain of voltage-controlled architectures tends to provide tighter load regulation, current-controlled architectures are generally easier to compensate over wide input and output voltage ranges. the max618 uses both control schemes in par- allel: the dominant, low-frequency components of the error signal are tightly regulated with a voltage-control loop, while a current-control loop improves stability at higher frequencies. compensation is achieved through the selection of the output capacitor (c out ), the inte- grator capacitor (c comp ), and the pole capacitor (c p ) from fb to gnd. c p cancels the zero formed by c out and its esr. refer to the capacitor selection section for guidance on selecting these capacitors. vl low-dropout regulator the max618 contains a 3.1v low-dropout linear regula- tor to power internal circuitry. the regulators input is in and its output is vl. the in to vl dropout voltage is 100mv, so that when in is less than 3.2v, vl is typically 100mv below in. the max618 still operates when the ldo is in dropout, as long as vl remains above the 2.7v undervoltage lockout. bypass vl with a 4.7f ceramic capacitor placed as close to the vl and gnd pins as possible. 28v, pwm, step-up dc-dc converter 6 _______________________________________________________________________________________ shdn max618 idle mode current limit pwm current limit error comparator 250khz oscillator slope compensation linear regulator current- sense circuit pgnd in lx out r 14r vl fb comp in vl nmos reference integrator gnd shutdown pwm logic thermal shutdown figure 2. functional diagram
max618 28v, pwm, step-up dc-dc converter _______________________________________________________________________________________ 7 45678910111213141516171819202122232425262728 3 0.20 0.20 0.18 0.15 0.12 0.10 0.09 0.08 0.07 0.06 0.05 0.04 0.04 0.04 0.03 0.03 0.03 0.03 0.03 0.02 0.02 0.02 0.02 0.02 0.02 4 0.18 0.21 0.20 0.17 0.15 0.13 0.12 0.10 0.09 0.08 0.07 0.07 0.06 0.05 0.05 0.04 0.04 0.04 0.03 0.03 0.03 0.03 0.03 0.03 5 0.16 0.20 0.21 0.19 0.17 0.16 0.14 0.13 0.11 0.10 0.09 0.09 0.08 0.07 0.07 0.06 0.06 0.05 0.05 0.04 0.04 0.04 0.04 6 0.15 0.20 0.21 0.20 0.19 0.18 0.16 0.15 0.13 0.12 0.11 0.10 0.10 0.09 0.08 0.08 0.07 0.07 0.06 0.06 0.05 0.05 7 0.17 0.19 0.21 0.21 0.20 0.19 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.10 0.10 0.09 0.08 0.08 0.07 0.07 0.07 8 0.19 0.18 0.20 0.21 0.20 0.20 0.19 0.17 0.16 0.15 0.14 0.13 0.13 0.12 0.11 0.10 0.10 0.09 0.09 0.08 9 0.20 0.17 0.20 0.21 0.21 0.20 0.19 0.18 0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.12 0.11 0.10 0.10 10 0.21 0.16 0.19 0.20 0.21 0.21 0.20 0.19 0.18 0.17 0.17 0.16 0.15 0.14 0.13 0.13 0.12 0.11 11 0.22 0.15 0.19 0.20 0.21 0.21 0.20 0.20 0.19 0.18 0.17 0.17 0.16 0.15 0.14 0.14 0.13 12 0.23 0.15 0.18 0.20 0.21 0.21 0.21 0.20 0.20 0.19 0.18 0.18 0.17 0.16 0.15 0.15 13 0.24 0.16 0.17 0.19 0.20 0.21 0.21 0.20 0.20 0.19 0.19 0.18 0.17 0.17 0.16 14 0.25 0.17 0.17 0.19 0.20 0.21 0.21 0.21 0.20 0.20 0.19 0.19 0.18 0.17 15 0.25 0.18 0.16 0.18 0.20 0.20 0.21 0.21 0.21 0.20 0.20 0.19 0.19 16 0.26 0.19 0.16 0.18 0.19 0.20 0.21 0.21 0.21 0.20 0.20 0.20 17 0.26 0.20 0.15 0.17 0.19 0.20 0.20 0.21 0.21 0.21 0.20 18 0.27 0.20 0.15 0.17 0.19 0.20 0.20 0.21 0.21 0.21 19 0.27 0.21 0.16 0.17 0.18 0.19 0.20 0.21 0.21 20 0.27 0.21 0.17 0.16 0.18 0.19 0.20 0.20 21 0.28 0.22 0.17 0.16 0.18 0.19 0.20 22 0.28 0.22 0.18 0.15 0.17 0.19 23 0.28 0.23 0.18 0.15 0.17 24 0.28 0.23 0.19 0.15 25 0.29 0.24 0.19 26 0.29 0.24 27 0.29 v out v in table 1. pwm/idle-mode transition load current (i out in amps) vs. input and output voltage
max618 28v, pwm, step-up dc-dc converter 8 _______________________________________________________________________________________ gnd lx c out l pgnd r2 r1 c p vl comp c comp in shdn up to 28v v ind up to 28v c ind in out max618 2.7v to 5.5v 4.7 f 1 f fb lx c ind c out l pgnd gnd r1 vl comp c comp in shdn up to 28v v ind up to 28v out max618 in 3v to 28v 4.7 f 1 f r2 c p fb figure 3. dual-supply operation (v in = 2.7v to 5.5v) figure 4. dual-supply operation (v in = 3v to 28v) table 2. input configurations vl can be overdriven by an external supply between 2.7v and 5.5v. in systems with +3.3v or +5v logic power supplies available, improve efficiency by power- ing vl and v in directly from the logic supply as shown in figure 3. operating configurations the max618 can be connected in one of three configura- tions described in table 2 and shown in figures 1, 3, and 4. the vl linear regulator allows operation from a single supply between +3v and +28v as shown in figure 1. the circuit in figure 3 allows a logic supply to power the max618 while using a separate source for dc-dc conversion power (inductor voltage). the logic supply (between 2.7v and 5.5v) connects to vl and in. vl = in; voltages of 3.3v or more improve efficiency by pro- viding greater gate drive for the internal mosfet. the circuit in figure 4 allows separate supplies to power in and the inductor voltage. it differs from the connection in figure 3 in that the max618 chip supply is not limited to 5.5v. circuit figure 1 input voltage connects to in and inductor. connection v in range 3v to v out (up to 28v) v in inductor voltage benefits/comments ? single-supply operation. ? shdn must be connected to or pulled up to vl. on/off control requires an open-drain or open-collector connection to shdn. figure 3 figure 4 0 to v out (up to 28v) 0 to v out (up to 28v) ? increased efficiency. ? shdn can be driven by logic powered from the supply con- nected to in and vl, or can be connected to or pulled up to vl. ? input power source (inductor voltage) is separate from the max618s bias (v in = vl) and can be less than or greater than v in . ? input power source (inductor voltage) is separate from the max618s bias (v in ) and can be less than or greater than v in . ? shdn must be connected to or pulled up to vl. on/off control requires an open-drain or open-collector connection to shdn. in and inductor volt- age supplied by sepa- rate sources. in and vl connect together. inductor volt- age supplied by a separate source. 2.7v to 5.5v 3v to 28v
shutdown mode in shutdown mode ( shdn = 0), the max618s feed- back and control circuit, reference, and internal biasing circuitry turn off and reduce the in supply current to 3a (10a max). when in shutdown, a current path remains from the input to the output through the exter- nal inductor and diode. consequently, the output falls to v in less one diode drop in shutdown. shdn may not exceed vl. for always-on operation, connect shdn to vl. to add on/off control to the circuit of figure 1 or 4, pull shdn to vl with a resistor (10k ? to 100k ? ) and drive shdn with an open-drain logic gate or switch as shown in figure 5. alternatively, the circuit of figure 3 allows direct shdn drive by any logic-level gate powered from the same supply that powers vl and in, as shown in figure 6. __________________design procedure the max618 operates in a number of dc-dc converter configurations including step-up, sepic, and flyback. the following design discussion is limited to step-up converters. setting the output voltage two external resistors (r1 and r2) set the output volt- age. first, select a value for r2 between 10k ? and 200k ? . calculate r1 with: where v fb is 1.5v. determining the inductor value the max618s high switching frequency allows the use of a small value inductor. the recommended inductor value is proportional to the output voltage and is given by the following: after solving for the above equation, round down as necessary to select a standard inductor value. when selecting an inductor, choose one rated to 250khz, with a saturation current exceeding the peak inductor current, and with a dc resistance under 200m ? . ferrite core or equivalent inductors are gener- ally appropriate (see max618 ev kit data sheet). calculate the peak inductor current with the following equation: note that the peak inductor current is internally limited to 2a. diode selection the max618s high switching frequency demands a high-speed rectifier. schottky diodes are preferred for most applications because of their fast recovery time and low forward voltage. make sure that the diodes peak current rating exceeds the 2a peak switch cur- rent, and that its breakdown voltage exceeds the out- put voltage. ii v v 2s v l vv lx(peak) out out in in out i =+ ? ? ? ? ? ? ? n n out v () ? ? ? ? ? ? l v out = ? 710 5 rr v v out fb 12 1 =? ? ? ? ? ? ? max618 28v, pwm, step-up dc-dc converter _______________________________________________________________________________________ 9 max618 vl 100k on/off control open-drain logic shdn max618 in vl system logic on/off control shdn system logic supply figure 5. adding on/off control to circuit of figure 1 or 4 figure 6. adding on/off control to circuit of figure 3
max618 28v, pwm, step-up dc-dc converter 10 ______________________________________________________________________________________ maximum output current the max618s 2.2a lx current limit determines the output power that can be supplied for most applica- tions. in some cases, particularly when the input volt- age is low, output power is sometimes restricted by package dissipation limits. the max618 is protected by a thermal shutdown circuit that turns off the switch when the die temperature exceeds +150c. when the device cools by 10c, the switch is enabled again. table 3 details output current with a variety of input and output voltages. each listing in table 3 is either the limit set by an lx current limit or by package dissipation at +85c ambient, whichever is lower. the values in table 3 assume a 40m ? inductor resistance. capacitor selection input capacitors the input bypass capacitor, c ind , reduces the input ripple created by the boost configuration. high-imped- ance sources require high c ind values. however, 68f is generally adequate for input currents up to 2a. low esr capacitors are recommended because they will decrease the ripple created on the input and improve efficiency. capacitors with esr below 0.3 ? are gener- ally appropriate. in addition to the input bypass capacitor, bypass in with a 1f ceramic capacitor placed as close to the in and gnd pins as possible. bypass vl with a 4.7f ceramic capacitor placed as close to the vl and gnd pins as possible. output capacitor use table 4 to find the minimum output capacitance necessary to ensure stable operation. in addition, choose an output capacitor with low esr to reduce the output ripple. the dominant component of output ripple is the product of the peak-to-peak inductor ripple cur- rent and the esr of the output capacitor. esr below 50m ? generates acceptable levels of output ripple for most applications. integrator capacitor the compensation capacitor (c comp ) sets the domi- nant pole in the max618s transfer function. the proper compensation capacitance depends upon output capacitance. table 5 shows the capacitance value needed for the output capacitances specified in table 4. however, if a different output capacitor is used (e.g., a standard value), then recalculate the value of capaci- tance needed for the integrator capacitor with the fol- lowing formula: pole compensation capacitor the pole capacitor (c p ) cancels the unwanted zero introduced by c out s esr, and thereby ensures stabil- ity in pwm operation. the exact value of the pole capacitor is not critical, but it should be near the value calculated by the following equation: where r esr is c out s esr. layout considerations proper pc board layout is essential due to high current levels and fast switching waveforms that radiate noise. use the max618 evaluation kit or equivalent pc layout to perform initial prototyping. breadboards, wire-wrap, and proto-boards are not recommended when proto- typing switching regulators. it is important to connect the gnd pin, the input bypass capacitor ground lead, and the output filter capacitor ground lead to a single point to minimize ground noise and improve regulation. also, minimize lead lengths to reduce stray capacitance, trace resis- tance, and radiated noise, with preference given to the feedback circuit, the ground circuit, and lx. place the feedback resistors as close to the fb pin as possible. place a 1f input bypass capacitor as close as possi- ble to in and gnd. refer to the max618 evaluation kit for an example of proper board layout. chip information process: bicmos package information for the latest package outline information and land patterns, go to www.maxim-ic.com/packages . note that a +, #, or - in the package code indicates rohs status only. package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. c rc(r1r2) r1 r2 p esr out = + ? ? c c table c c table comp comp out out = ? () () 5 4 package type package code document no. 16 qsop ef16+8f 21-0055
max618 28v, pwm, step-up dc-dc converter ______________________________________________________________________________________ 11 45678910111213141516171819202122232425262728 3 0.77 0.59 0.49 0.41 0.34 0.29 0.25 0.22 0.20 0.18 0.17 0.15 0.14 0.13 0.12 0.12 0.11 0.10 0.10 0.09 0.09 0.08 0.08 0.08 0.07 4 0.96 0.76 0.64 0.56 0.49 0.43 0.38 0.34 0.31 0.28 0.26 0.24 0.22 0.21 0.19 0.18 0.17 0.16 0.16 0.15 0.14 0.14 0.13 0.12 5 1.09 0.89 0.76 0.67 0.60 0.54 0.50 0.45 0.41 0.37 0.34 0.32 0.30 0.28 0.26 0.25 0.23 0.22 0.21 0.20 0.19 0.18 0.18 6 1.18 0.99 0.85 0.76 0.68 0.63 0.58 0.54 0.50 0.46 0.42 0.39 0.37 0.34 0.32 0.31 0.29 0.28 0.26 0.25 0.24 0.23 7 1.26 1.07 0.93 0.83 0.76 0.70 0.65 0.60 0.57 0.53 0.50 0.46 0.43 0.41 0.38 0.36 0.35 0.33 0.31 0.30 0.29 8 1.32 1.13 1.00 0.90 0.82 0.76 0.71 0.66 0.62 0.59 0.56 0.53 0.50 0.47 0.44 0.42 0.40 0.38 0.36 0.35 9 1.37 1.19 1.06 0.96 0.88 0.81 0.76 0.71 0.67 0.64 0.61 0.58 0.55 0.53 0.50 0.47 0.45 0.43 0.41 10 1.41 1.24 1.11 1.01 0.93 0.86 0.81 0.76 0.72 0.68 0.65 0.62 0.59 0.57 0.55 0.52 0.50 0.47 11 1.44 1.28 1.15 1.05 0.97 0.91 0.85 0.80 0.76 0.72 0.69 0.66 0.63 0.61 0.58 0.56 0.54 12 1.47 1.31 1.19 1.10 1.02 0.95 0.89 0.84 0.80 0.76 0.73 0.70 0.67 0.64 0.62 0.60 13 1.49 1.34 1.23 1.13 1.05 0.99 0.93 0.88 0.83 0.80 0.76 0.73 0.70 0.67 0.65 14 1.52 1.37 1.26 1.16 1.09 1.02 0.96 0.91 0.87 0.83 0.79 0.76 0.73 0.71 15 1.53 1.40 1.29 1.19 1.12 1.05 0.99 0.94 0.90 0.86 0.82 0.79 0.76 16 1.55 1.42 1.31 1.22 1.14 1.08 1.02 0.97 0.93 0.89 0.85 0.82 17 1.57 1.44 1.33 1.25 1.17 1.11 1.05 1.00 0.95 0.91 0.88 18 1.58 1.46 1.36 1.27 1.20 1.13 1.07 1.02 0.98 0.94 19 1.59 1.47 1.37 1.29 1.22 1.15 1.10 1.05 1.00 20 1.60 1.49 1.39 1.31 1.24 1.18 1.12 1.07 21 1.61 1.50 1.41 1.33 1.26 1.20 1.14 22 1.62 1.51 1.42 1.35 1.28 1.22 23 1.63 1.53 1.44 1.36 1.29 24 1.64 1.54 1.45 1.38 25 1.64 1.55 1.46 26 1.65 1.56 27 1.66 v in v out table 3. typical output current vs. input and output voltages
max618 28v, pwm, step-up dc-dc converter 12 ______________________________________________________________________________________ 45678910111213141516171819202122232425262728 3 173 128 100 80 65 54 46 40 35 31 28 25 23 21 19 18 17 15 15 14 13 12 12 11 10 4 151 118 96 80 68 59 51 45 39 35 32 29 27 24 23 21 20 18 17 16 15 15 14 13 5 132 107 90 77 67 59 52 46 41 37 34 31 29 26 25 23 21 20 19 18 17 16 15 6 117 97 83 72 64 57 51 46 42 38 35 32 30 28 26 24 23 21 20 19 18 17 7 104 89 77 68 61 55 50 45 42 39 35 33 30 28 26 25 23 22 21 20 19 8 9482726458524844413835333129272524222120 9 86766761555046423937343230292725242321 10 79 70 63 57 52 48 44 41 38 36 34 32 30 28 27 25 24 23 11 73 66 59 54 50 46 43 40 37 35 33 31 29 28 26 25 24 12 68 62 56 51 47 44 41 38 36 34 32 30 29 27 26 25 13 64 58 53 49 45 42 39 37 35 33 31 29 28 27 25 14 60 55 50 47 43 40 38 36 34 32 30 29 27 26 15 56 52 48 44 42 39 37 35 33 31 29 28 27 16 53 49 46 43 40 37 35 33 32 30 29 27 17 50 47 44 41 38 36 34 32 31 29 28 18 48 45 42 39 37 35 33 31 30 28 19 46 43 40 38 36 34 32 30 29 20 43 41 38 36 34 33 31 29 21 42 39 37 35 33 32 30 22 40 38 36 34 32 31 23 38 36 34 33 31 24 37 35 33 32 25 35 34 32 26 34 33 27 33 v in v out table 4. minimum c out for stability (f)
max618 28v, pwm, step-up dc-dc converter ______________________________________________________________________________________ 13 45678910111213141516171819202122232425262728 3 40 46 54 64 73 83 94 105 118 130 143 157 172 187 203 219 236 253 271 290 309 329 349 370 391 4 42 45 51 58 66 74 82 91 100 109 119 130 141 152 164 176 188 201 214 228 242 257 272 287 5 43 45 49 54 60 67 75 81 88 96 103 111 120 128 137 147 156 166 176 187 197 209 220 6 44 45 48 52 57 62 68 74 80 86 92 99 105 112 119 127 134 142 150 159 167 176 7 45454750545863687479859095101107113119125132139146 8 464547495256606468737883889398103108113119124 9 4646474851545761646873778286919599104109 10 47 46 46 48 50 52 55 58 61 65 69 72 77 81 85 89 93 97 11 47 46 46 48 49 51 54 56 59 62 65 69 72 76 80 84 88 12 48 47 47 47 49 50 52 55 57 60 63 66 69 72 75 79 13 48 47 47 47 48 50 52 54 56 58 61 63 66 69 72 14 49 47 47 47 48 49 51 53 55 57 59 61 64 66 15 49 47 47 47 48 49 50 52 53 55 57 59 62 16 49 48 47 47 48 49 50 51 53 54 56 58 17 49 48 47 47 48 48 49 51 52 53 55 18 50 48 47 47 48 48 49 50 51 53 19 50 48 47 47 48 48 49 50 51 20 50 48 48 47 48 48 49 49 21 50 49 48 47 48 48 48 22 50 49 48 48 48 48 23 50 49 48 48 48 24 51 49 48 48 25 51 49 48 26 51 49 27 51 v out v in table 5. minimum c comp for stability (nf)
max618 28v, pwm, step-up dc-dc converter maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 14 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2009 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision history revision number revision date description pages changed 0 6/99 initial release 1 12/09 updated part to lead-free, added soldering temperatures (reflow), and corrected error in equation 1, 2, 10

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