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general description the max16990/max16992 are high-performance, current-mode pwm controllers with 4 a (typ) shut - down current for wide input voltage range boost/sepic converters. the 4.5v to 36v input operating volt - age range makes these devices ideal in automotive applications such as for front-end preboost or sepic power supplies and for the first boost stage in high- power led lighting applications. an internal low-dropout regulator (pvl regulator) with a 5v output voltage enables the max16990/max16992 to operate directly from an automotive battery input. the input operating range can be extended to as low as 2.5v when the converter output is applied to the sup input. there are multiple versions of the devices offering one or more of the following functions: a synchronization output (synco) for two-phase operation, an overvoltage protection function using a separate input pin (ovp), and a reference input pin (refin) to allow on-the-fly output voltage adjustment. the max16990 and max16992 operate in different frequency ranges. all versions can be synchronized to an external master clock using the fset/sync input. in addition, the max16990/max16992 have a factory- programmable spread-spectrum option. both devices are available in compact 12-pin tqfn and 10-pin max ? packages. applications automotive led lighting automotive audio/navigation systems dashboards benefts and features minimized radio interference with 2.5mhz switching frequency above the am radio band space-efficient solution design with minimized external components ? 100khz to 1mhz (max16990) and 1mhz to 2.5mhz (max16992) switching-frequency ranges ? 12-pin tqfn (3mm x 3mm) and 10-pin max packages spread spectrum simplifies emi management design flexibility with available configurations for boost, sepic, and multiphase applications ? adjustable slope compensation ? current-mode control ? internal soft-start (9ms) protection features support robust automotive applications ? operating voltage range down to 4.5v (2.5v or lower in bootstrapped mode), immune to load-dump transient voltages up to 42v ? pgood output and hiccup mode for enhanced system protection ? overtemperature shutdown ? -40 c to +125 c operation typical application circuit 19-6632; rev 6; 8/15 ordering information appears at end of data sheet. max is a registered trademark of maxim integrated products, inc. MAX16992AUBA / b n n drv sup gnd 1f sw_out 8v/ 2a battery input 2.5v to 40v pgood pvl pgood pvl fset/sync fb en enable comp isns 1k? 22m? 12k? 13k? n 10k? 10k? p 17k? 91k? 22f 0.47h 47f ceramic 2.2f bootstrapped 2.2mhz application with low operating voltage max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers evaluation kit available
en, sup, ovp, fb to gnd .................................... -0.3v to +42v drv, synco, fset/sync, comp, pgood, isns, refin to gnd ............ -0.3v to (v pvl + 0.3v) pvl to gnd ............................................................... -0.3v to 6v continuous power dissipation (t a = +70 n c) f max on slb (derate 10.3mw/ n c above +70 n c) ....... 825mw f max on mlb (derate 12.9mw/ n c above +70 n c) .... 1031mw tqfn on slb (derate 13.2mw/ n c above +70 n c) ..... 1053mw tqfn on mlb (derate 14.7mw/ n c above +70 n c) .... 1176mw operating temperature range ........................ -40 n c to +125 n c maximum junction temperature ..................................... +150 n c storage temperature range ............................ -65 n c to +150 n c lead temperature (soldering, 10s) ................................ +300 n c soldering temperature (reflow) ...................................... +260 n c f max (single-layer board) junction-to-ambient thermal resistance ( b ja ) .......... 97 n c/w junction-to-case thermal resistance ( b jc ) ................. 5 n c/w f max (four-layer board) junction-to-ambient thermal resistance ( b ja ) .......... 78 n c/w junction-to-case thermal resistance ( b jc ) ..................... 5 n c/w tqfn (single-layer board) junction-to-ambient thermal resistance ( b ja ) .......... 76 n c/w junction-to-case thermal resistance ( b jc ) ................... 11 n c/w tqfn (four-layer board) junction-to-ambient thermal resistance ( b ja ) .......... 68 n c/w junction-to-case thermal resistance ( b jc ) ............... 11 n c/w absolute maximum ratings note 1: package thermal resistances were obtained using the method described in jedec specification jesd51-7, using a four-layer board. for detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial . stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress ratings only, and functional opera - tion 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. package thermal characteristics (note 1) electrical characteristics (v sup = 14v, t a = t j = -40 n c to +125 n c, unless otherwise noted. typical values are at t a =+25 n c.) (note 2) maxim integrated 2 parameter symbol conditions min typ max units power supply sup operating supply range v sup 4.5 36 v sup supply current in operation i cc v fb = 1.1v, no switching max16990 0.75 1.3 ma max16992 1.25 2 sup supply current in shutdown i shdn v en = 0v 4 7 f a ovp threshold voltage v ovp ovp rising 105 110 115 % of v fb ovp threshold voltage hysteresis v ovph 2.5 % of v fb ovp input current i ovp -1 +1 f a pvl regulator pvl output voltage v pvl 4.7 5 5.3 v pvl undervoltage lockout v uv sup rising 3.8 4 4.3 v pvl undervoltage-lockout hysteresis v uvh 0.4 v www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers
electrical characteristics (continued) (v sup = 14v, t a = t j = -40 n c to +125 n c, unless otherwise noted. typical values are at t a =+25 n c.) (note 2) maxim integrated 3 parameter symbol conditions min typ max units oscillator switching frequency f sw r fset = 69k i 360 400 440 khz r fset = 12k i 2000 2200 2400 spread-spectrum spreading factor ss b, d, and f versions q 6 % of f sw switching frequency range f swr when set with resistor on pin max16990 100 1000 khz max16992 1000 2500 fset/sync frequency range f sync using external sync signal max16990 220 1000 khz max16992 1000 2500 fset regulation voltage v fset 12k i < r fset < 69k i 0.9 v soft-start time t ss internally set 6 9 12 ms hiccup period t hiccup 55 ms maximum duty cycle dc max max16990, r fset = 69k i 93 % max16992, r fset = 12k i 85 minimum on-time t on 50 80 110 ns thermal shutdown thermal-shutdown temperature t s temperature rising 165 n c thermal-shutdown hysteresis t h 10 n c gate drivers drv pullup resistance r drvh i drv = 100ma 3 5.5 i drv pulldown resistance r drvl i drv = -100ma 1.4 2.5 i drv output peak current i drv sourcing, c drv = 10nf 0.75 a sinking, c drv = 10nf 1 regulation/current sense fb regulation voltage v fb v refin = v pvl across full line, load, and temperature range 0.99 1 1.01 v v refin = 2v 1.98 2 2.02 v refin = 0.5v 0.495 0.5 0.505 fb input current i fb -0.5 +0.5 f a isns threshold 212 250 288 mv isns leading-edge blanking time t blank max16990 60 ns max16992 40 current-sense gain a vi 8 v/v peak slope compensation current-ramp magnitude added to isns input 40 50 60 f a pgood threshold v pg percentage of final value rising 85 90 95 % falling 80 85 90 www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers
note 2: all devices 100% production tested at t a = +25 n c. limits over temperature are guaranteed by design. electrical characteristics (continued) (v sup = 14v, t a = t j = -40 n c to +125 n c, unless otherwise noted. typical values are at t a =+25 n c.) (note 2) maxim integrated 4 parameter symbol conditions min typ max units error amplifier refin input voltage range 0.5 2 v refin threshold for 1v fb regulation v pvl - 0.8 v pvl - 0.4 v pvl - 0.1 v error-amplifier g m a vea 700 f s error-amplifier output impedance r oea 50 m i comp output current i comp 140 a comp clamp voltage 2.7 3 3.3 v logic-level inputs/outputs pgood/synco output leakage current v pgood /v synco = 5v 0.5 f a pgood/synco output low level sinking 1ma 0.4 v en high input threshold en rising 1.7 v en low input threshold 1.2 v fset/sync high input threshold 2.5 v fset/sync low input threshold 1 v en and refin input current -1 +1 f a www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers
typical operating characteristics (v sup = 14v, t a = +25 n c, unless otherwise noted.) maxim integrated 5 pvl voltage vs. supply voltage max16990 toc04 supply voltage (v) pvl voltage (v) 28 20 12 4.2 4.1 4.3 4.5 4.4 4.6 4.7 4.8 4.9 5.0 5.1 5.2 4.0 4 36 i pvl = 10ma i pvl = 1ma max16990 internal oscillator frequency vs. temperature max16990 toc07 temperature (c) internal oscillator frequency (khz) 20 40 60 80 100 0 -20 385 390 395 400 405 410 415 420 380 -40 120 r set = 68.1ki pvl voltage vs. supply voltage max16990 toc05 supply voltage (v) pvl voltage (v) 6 5 4 3.2 3.4 3.8 3.6 4.0 4.2 4.4 4.6 4.8 5.0 5.2 3.0 3 7 i pvl = 10ma i pvl = 1ma max16992 internal oscillator frequency vs. supply voltage max16990 toc08 supply voltage (v) internal oscillator frequency (khz) 28 20 12 2100 2050 2150 2200 2250 2300 2350 2400 2000 4 36 r set = 12.1ki max16990 internal oscillator frequency vs. supply voltage max16990 toc06 supply voltage (v) internal oscillator frequency (khz) 28 20 12 392 396 394 398 400 402 404 406 408 410 390 4 36 r set = 68.1ki max16992 internal oscillator frequency vs. temperature max16990 toc09 temperature (c) internal oscillator frequency (khz) 20 40 60 80 100 0 -20 2130 2120 2110 2140 2150 2160 2170 2180 2190 2200 2100 -40 120 r set = 12.1ki supply current vs. supply voltage max16990 toc01 supply voltage (v) 2.2mhz supply current (ma) 400khz 28 20 12 0.2 0.4 0.6 0.8 1.0 1.2 1.4 0 4 36 v en = v sup v fb = 1.1v shutdown supply current vs. supply voltage max16990 toc02 supply voltage (v) v en = 0v shutdown supply current (a) 28 20 12 1 2 3 3 4 5 6 7 8 9 10 0 4 36 shutdown supply current vs. temperature max16990 toc03 temperature (c) shutdown supply current (a) 20 40 60 80 100 0 -20 3.8 4.0 4.2 4.4 4.6 4.8 5.0 5.2 3.6 -40 120 v en = 0v www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers
typical operating characteristics (continued) (v sup = 14v, t a = +25 n c, unless otherwise noted.) maxim integrated 6 startup response max16990 toc12 5v/div 5v/div 0v 0v 5v/div 0v 5v/div 0v v en v pvl v out v sup 2ms/div startup response (with switched output) max16990 toc14 5v/div 5v/div 0v 0v 5v/div 0v 5v/div 0v v en v sw_out v out v pgood 2ms/div startup response max16990 toc13 5v/div 5v/div 0v 0v 5v/div 0v 5v/div 0v v en v drv v out v pgood 2ms/div output load transient max16990 toc15 5v/div 5v/div 0v 0v 500mv/div (ac-coupled) 1a /div 0a i load v out v out v sup 50ms/div power-up response max16990 toc10 5v/div 5v/div 0v 0v 5v/div 0v 5v/div 0v v pgood v pvl v out v sup 2ms/div power-up response max16990 toc11 5v/div 5v/div 0v 0v 5v/div 0v 5v/div 0v v pgood v drv v out v sup 2ms/div www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers
typical operating characteristics (continued) (v sup = 14v, t a = +25 n c, unless otherwise noted.) maxim integrated 7 output voltage vs. refin voltage max16990 toc18 refin voltage (v) output voltage (v) 2.5 2.0 1.5 1.0 5 10 15 20 25 30 0 0.5 3.0 i out = 0a ovp shutdown max16990 toc20 5v/div 1v/div 0v 0v 5v/div 0v 5v/div 0v v pgood v drv v ovp v out 1s/div switching waveform max16990 toc19 5v/div 5v/div 0v 0v 5v/div 0v 1a /div 0a i load v lx v in v out 500ns/div hiccup mode max16990 toc21 5v/div 0v 5v/div 0v 5v/div 0v v pgood v drv v out 20ms/div line transient max16990 toc16 5v/div 5v/div 0v 0v 500mv/div (ac-coupled) 1a /div 0a i load v out v out v sup 20ms/div max16992 v sync vs. v synco max16990 toc17 2v/div 0v 2v/div 0v v synco v sync 200ns/div www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers
typical operating characteristics (continued) (v sup = 14v, t a = +25 n c, unless otherwise noted.) maxim integrated 8 0 100 200 300 400 500 600 700 800 900 1000 1100 0 100 200 300 internal oscillator frequqncy (khz) rset(k ) max16990 internal oscillator frequency vs. r set max16990/2 toc25 max16990 maximum duty cycle vs. temperature max16990 toc28 temperature (c) maximum duty cycle (%) 120 100 60 80 0 20 40 -20 94.7 94.9 95.1 95.3 95.5 95.7 95.9 94.5 -40 r set = 68.1ki current-limit threshold vs. temperature max16990 toc26 temperature (c) current-limit threshold (mv) 120 100 60 80 0 20 40 -20 242 244 246 248 250 252 254 256 258 260 240 -40 cold-crank input voltage transient max16990 toc29 5v/div 5v/div 0v 0v 1a /div 0a 5v/div 0v v pgood i load v out v in 20ms/div max16992 maximum duty cycle vs. temperature max16990 toc27 temperature (c) maximum duty cycle (%) 120 100 60 80 0 20 40 -20 87.5 88.0 88.5 89.0 89.5 90.0 90.5 91.0 87.0 -40 r set = 12.1ki max16990 efficiency max16990 toc22 supply voltage (v) efficiency (%) 7 6 5 55 60 65 70 75 80 85 90 95 100 50 4 8 i out = 100ma i out = 2a i out = 1a max16992 efficiency max16990 toc23 supply voltage (v) efficiency (%) 7 6 5 55 60 65 70 75 80 85 90 95 100 50 4 8 i out = 100ma i out = 1a i out = 2a max16992 internal oscillator frequency vs. r set max16990 toc24 r set (ki) internal oscillator frequqncy (khz) 25 20 15 1000 1200 1400 1600 1800 2000 2200 2400 2600 800 10 30 www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers
pin confgurations pin descriptions maxim integrated 9 max16990auba/b, MAX16992AUBA/b max16990atcc/d, max16992atcc/d max16990atce/f, max16992atce/f name function max-ep tqfn-ep tqfn-ep 1 1 1 sup power-supply input. place a bypass capacitor of at least 1 f f between this pin and ground. 2 3 3 en active-high enable input. this input is high-voltage capable or can alternatively be driven from a logic- level signal. 3 2 2 gnd ground connection 4 4 4 drv drive output for gate of nmos boost switch. the nominal voltage swing of this output is between pvl and gnd. 5 5 5 pvl output of 5v internal regulator. connect a ceramic capacitor of at least 2.2 f f from this pin to ground, placing it as close as possible to the pin. 6 6 6 isns current-sense input to regulator. connect a sense resistor between the source of the external switching fet and gnd. then connect another resistor between isns and the source of the fet for slope compensation adjustment. 12 11 10 4 5 gnd en 6 sup refin synco pgood 12 comp 3 98 7 fb isns pvl drv fset/sync tqfn (3mm x 3mm) max16990atce/f max16992atce/f top view + 12 11 10 4 5 gnd en 6 sup refin ovp pgood 12 comp 3 98 7 fb isns pvl drv fset/sync tqfn (3mm x 3mm) max16990atcc/d max16992atcc/d top view + 1 2 3 4 5 10 9 8 7 6 fb comp fset/sync pgood drv gnd en sup max top view isns pvl ep ep ep + max16990auba/b MAX16992AUBA/b www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers
pin descriptions (continued) maxim integrated 10 max16990auba/b, MAX16992AUBA/b max16990atcc/d, max16992atcc/d max16990atce/f, max16992atce/f name function max-ep tqfn-ep tqfn-ep 7 synco open-drain synchronization output. synco outputs a square-wave signal which is 180 n out-of-phase with the devices operational clock. connect a pullup resistor from this pin to pvl or to a 5v or lower supply when used. 7 ovp overvoltage protection input. when this pin goes above 110% of the fb regulation voltage, all switching is disabled. operation resumes normally when ovp drops below 107.5% of the fb regulation point. connect a resistor divider between the output, ovp, and gnd to set the overvoltage protection level. 8 8 refin reference input. when using the internal reference connect refin to pvl. otherwise, drive this pin with an external voltage between 0.5v and 2v to set the boost output voltage. 7 9 9 pgood open-drain power-good output. connect a resistor from this pin to pvl or to another voltage less than or equal to 5v. pgood goes high after soft-start when the output exceeds 90% of its final value. when en is low pgood is also low. after soft-start is complete, if pgood goes low and 16 consecutive current-limit cycles occur, the devices enter hiccup mode and a new soft-start is initiated after a delay of 44ms. 8 10 10 fset/ sync frequency set/synchronization. to set a switching frequency between 100khz and 1000khz (max16990) or between 1000khz and 2500khz (max16992), connect a resistor from this pin to gnd. to synchronize the converter, connect a logic signal in the range 220khz to 1000khz (max16990) or 1000khz to 2500khz (max16992) to this input. the external n-channel mosfet is turned on (i.e., drv goes high) after a short delay (60ns for 2.2mhz operation, 125ns for 400khz) when sync transitions low. 9 11 11 comp output of error amplifier. connect the compensation network between comp and gnd. 10 12 12 fb boost converter feedback. this pin is regulated to 1v when refin is tied to pvl or otherwise regulated to refin during boost operation. connect a resistor divider between the boost output, the fb pin and gnd to set the boost output voltage. in a two-phase converter connect the fb pin of the slave ic to pvl. www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers
pin descriptions (continued) functional diagram maxim integrated 11 max16990auba/b, MAX16992AUBA/b max16990atcc/d, max16992atcc/d max16990atce/f, max16992atce/f name function max-ep tqfn-ep tqfn-ep ep exposed pad. internally connected to gnd. connect to a large ground plane to maximize thermal performance. not intended as an electrical connection point. 5v regulator + reference uvlo pvl sup (ovp) en fset/sync (synco) pgood drv gnd en thermal isns ref. 250mv control logic oscillator thermal 50a x f sw blanking time v pvl - 0.4v 1v comp fb (refin) pgood comparator ota max16990 max16992 8 www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers
detailed description the max16990/max16992 are high-performance, current-mode pwm controllers for wide input voltage range boost/sepic converters. the input operating volt - age range of 4.5v to 36v makes these devices ideal in automotive applications such as for front-end preboost or sepic power supplies and for the first boost stage in high-power led lighting applications. an internal low-dropout regulator (pvl regulator) with an output volt - age of 5v enables the devices to operate directly from an automotive battery input. the input operating range can be as low as 2.5v when the converter output supplies the sup input. the input undervoltage lockout (uvlo) circuit moni - tors the pvl voltage and turns off the converter when the voltage drops below 3.6v (typ). an external resistor programs the switching frequency in two ranges from 100khz to 1000khz (max16990) or between 1000khz and 2500khz (max16992). the fset/sync input can also be used for synchronization to an external clock. the sync pulse width should be greater than 70ns. inductor current information is obtained by means of an external sense resistor connected from the source of the external n-channel mosfet to gnd. the devices include an internal transconductance error amplifier with 1% accurate reference. at startup the internal reference is ramped in a time of 9ms to obtain soft-start. the devices also include protection features such as hiccup mode and thermal shutdown as well as an optional overvoltage-detection circuit (ovp pin, c and d versions). current-mode control loop the max16990/max16992 offers peak current-mode control operation for best load step performance and simpler compensation. the inherent feed-forward characteristic is useful especially in automotive appli - cations where the input voltage changes quickly during cold-crank and load dump conditions. while the current-mode architecture offers many advantages, there are some shortcomings. in high duty-cycle operation, subharmonic oscillations can occur. to avoid this, the device offers programmable slope compensation using a single resistor between the isns pin and the current- sense resistor. to avoid premature turn-off at the begin - ning of the on-cycle the current-limit and pwm compara - tor inputs have leading-edge blanking. startup operation/uvlo/en the devices feature undervoltage lockout on the pvl- regulator and turn on the converter once pvl rises above 4v. the internal uvlo circuit has about 400mv hysteresis to avoid chattering during turn-on. once the converter is operating and if sup is fed from the output, the converter input voltage can drop below 4.5v. this feature allows operation at cold-crank voltages as low as 2.5v or even lower with careful selection of external com - ponents. the en input can be used to disable the device and reduce the standby current to less than 4 f a (typ). soft-start the devices are provided with an internal soft-start time of 9ms. at startup, after voltage is applied and the uvlo threshold is reached, the device enters soft-start. during soft-start, the reference voltage ramps linearly to its final value in 9ms. oscillator frequency/external synchronization/ spread spectrum use an external resistor at fset/sync to program the max16990 internal oscillator frequency from 100khz to 1mhz and the max16992 frequency between 1mhz and 2.5mhz. see tocs 24 and 25 in the typical operating characteristics section for resistor selection. the synco output is a 180 n phase-shifted version of the internal clock and can be used to synchro - nize other converters in the system or to implement a two-phase boost converter with a second max16990/ max16992. the advantages of a two-phase boost topol - ogy are lower input and output ripple and simpler thermal management as the power dissipation is spread over more components. see the multiphase operation section for further details. the devices can be synchronized using an external clock at the fset/sync input. a falling clock edge on fset/sync turns on the external mosfet by driving drv high after a short delay. the b, d, and f versions of the devices have spread- spectrum oscillators. in these parts the internal oscillator frequency is varied dynamically 6% around the switch - ing frequency. spread spectrum can improve system emi performance by reducing the height of peaks due to the switching frequency and its harmonics in the spectrum. the synco output includes spread-spectrum modulation when the internal oscillator is used on the b, d, and f versions. spread spectrum is not active when an external clock is applied to the fset/sync pin. maxim integrated 12 www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers
n-channel mosfet driver drv drives the gate of an external n-channel mosfet. the driver is powered by the internal regulator (pvl), which provides approximately 5v. this makes both the devices suitable for use with logic-level mosfets. drv can source 750ma and sink 1000ma peak current. the average current sourced by drv depends on the switching frequency and total gate charge of the external mosfet (see the power dissipation section). error amplifer the devices include an internal transconductance error amplifier. the noninverting input of the error amplifier is connected to the internal 1v reference and feedback is provided at the inverting input. high 700 f s open-loop transconductance and 50m output impedance allow good closed-loop bandwidth and transient response. moreover, the source and sink current capability of 140 f a provides fast error correction during output load transients. slope compensation the devices use an internal current-ramp generator for slope compensation. the internal ramp signal resets at the beginning of each cycle and slews at a typical rate of 50 f a x f sw . the amount of slope compensation needed depends on the slope of the current ramp in the inductor. see the current-sense resistor selection and setting slope compensation section for further information. current limit the current-sense resistor (r cs ) connected between the source of the mosfet and ground sets the current limit. the isns input has a voltage trip level (v cs ) of 250mv. when the voltage produced by the current in the induc - tor exceeds the current-limit comparator threshold, the mosfet driver (drv) quickly terminates the on-cycle. in some cases, a short time-constant rc filter could be required to filter out the leading-edge spike on the sense waveform in addition to the internal blanking time. the amplitude and width of the leading edge spike depends on the gate capacitance, drain capacitance, and switch - ing speed (mosfet turn-on time). hiccup operation the devices incorporate a hiccup mode in an effort to protect the external power components when there is an output short-circuit. if pgood is low (i.e., the output voltage is less than 85% of its set value) and there are 16 consecutive current-limit events, switching is stopped. there is then a waiting period of 44ms before the device tries to restart by initiating a soft-start. note that a short-circuit on the output places considerable stress on all the power components even with hiccup mode, so that careful component selection is important if this condition is encountered. for more complete protection against output short-circuits, a series pmos switch driven from pgood through a level-shifter can be employed (see figure 1 ). applications information inductor selection using the following equation, calculate the minimum inductor value so that the converter remains in continu - ous mode operation at minimum output current (i omin ): l min = (v in 2 x d x e )/(2 x f sw x v out x i omin ) where: d = (v out + v d - v in )/(v out + v d - v ds ) and: i omin is between 10% and 25% of i out a higher value of i omin reduces the required inductance; however, it increases the peak and rms currents in the switching mosfet and inductor. select i omin between 10% to 25% of the full load current. v d is the forward voltage drop of the external schottky diode, d is the duty cycle, and v ds is the voltage drop across the external switch. select an inductor with low dc resistance and with a saturation current (i sat ) rating higher than the peak switch current limit of the converter. input and output capacitors the input current to a boost converter is almost continuous and the rms ripple current at the input capacitor is low. calculate the minimum input capacitor value and maximum esr using the following equations: c in = d i l x d/(4 x f sw x d v q ) esr max = d v esr / d i l where d i l = ((v in - v ds ) x d)/(l x f sw ). v ds is the total voltage drop across the external mosfet plus the voltage drop across the inductor esr. d i l is peak-to-peak inductor ripple current as calculated above. d v q is the portion of input ripple due to the capacitor discharge and d v esr is the contribution due to esr of the capacitor. assume the input capacitor ripple contribution due to esr ( d v esr ) and capacitor discharge ( d v q ) are equal when using a combination of ceramic and aluminium capacitors. during the converter maxim integrated 13 www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers
turn-on, a large current is drawn from the input source especially at high output to input differential. the devices have an internal soft-start, however, a larger input capac - itor than calculated above could be necessary to avoid chattering due to finite hysteresis during turn-on. in a boost converter, the output capacitor supplies the load current when the main switch is on. the required output capacitance is high, especially at lower duty cycles. also, the output capacitor esr needs to be low enough to minimize the voltage drop due to the esr while supporting the load current. use the following equations to calculate the output capacitor, for a specified output ripple. all ripple values are peak-to-peak. esr = d v esr /i out c out = (i out x d max )/( d v q x f sw ) where i out is the output current, d v q is the portion of the ripple due to the capacitor discharge, and d v esr is the ripple contribution due to the esr of the capacitor. d max is the maximum duty cycle (i.e., the duty cycle at the minimum input voltage). use a combination of low-esr ceramic and high-value, low-cost aluminium capacitors for lower output ripple and noise. current-sense resistor selection and setting slope compensation set the current-limit threshold 20% higher than the peak switch current at the rated output power and minimum input voltage. use the following equation to calculate an initial value for r cs : r cs = 0.2/{1.2 x [((v out x i out )/ e )/v inmin + 0.5 x ((v out C v inmin )/v out ) x (v inmin /(f sw x l))]} where e is the estimated efficiency of the converter (use 0.85 as an initial value or consult the graph in the typical operating characteristics section); v out and i out are the output voltage and current, respectively; v inmin is the minimum value of the input voltage; f sw is the switching frequency; and l is the minimum value of the chosen inductor. figure 1. application with output short-circuit protection maxim integrated 14 max16990 MAX16992AUBA n drv sup gnd input pgood pvl en fset/ sync fb comp isns v out n pvl www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers
the devices use an internal ramp generator for slope compensation to stabilize the current loop when oper - ating at duty cycles above 50%. the amount of slope compensation required depends on the down-slope of the inductor current when the main switch is off. the inductor down-slope in turn depends on the input to out - put voltage differential of the converter and the inductor value. theoretically, the compensation slope should be equal to 50% of the inductor downslope; however, a little higher than 50% slope is advised. use the following equation to calculate the required compensating slope (mc) for the boost converter: mc = 0.5 x (v out C v in )/l a/s the internal ramp signal resets at the beginning of each cycle and slews at the rate of 50 f a x f sw . adjust the amount of slope compensation by choosing r scomp to satisfy the following equation: r scomp = (mc x r cs )/(50e-6 x f sw ) in some applications a filter could be needed between the current-sense resistor and the isns pin to augment the internal blanking time. set the rc time constant just long enough to suppress the leading edge spike of the mosfet current. for a given design, measure the lead - ing spike at the lowest input and rated output load to determine the value of the rc filter which can be formed from the slope-compensation resistor and an added capacitor from isns to gnd. mosfet selection the devices drive a wide variety of logic-level n-channel power mosfets. the best performance is achieved with low-threshold n-channel mosfets that specify on-resistance with a gate-source voltage (v gs ) of 5v or less. when selecting the mosfet, key parameters can include: 1) total gate charge (q g ). 2) reverse-transfer capacitance or charge (c rss ). 3) on-resistance (r ds(on) ). 4) maximum drain-to-source voltage (v ds(max) ). 5) maximum gate frequencies threshold voltage (v th(max) ). at high switching frequencies, dynamic characteristics (parameters 1 and 2 of the above list) that predict switch - ing losses have more impact on efficiency than r ds(on ), which predicts dc losses. qg includes all capacitances associated with charging the gate. the v ds(max) of the selected mosfet must be greater than the maximum output voltage setting plus a diode drop (or the maximum input voltage if greater) plus an additional margin to allow for spikes at the mosfet drain due to the inductance in the rectifier diode and output capacitor path. in addition, qg determines the current needed to drive the gate at the selected operating frequency via the pvl linear regulator and thus determines the power dissipation of the ic (see the power dissipation section). low-voltage operation the devices operate down to a voltage of 4.5v or less on their sup pins. if the system input voltage is lower than this the circuit can be operated from its own output as shown in the typical application circuit . at very low input voltages it is important to remember that input current will be high and the power components (inductor, mosfet and diode) must be specified for this higher input current. in addition, the current-limit of the devices must be set high enough so that the limit is not reached during the on- time of the mosfet which would result in output power limitation and eventually entering hiccup mode. estimate the maximum input current using the following equation: i inmax = ((v out x i out )/ e )/v inmin + 0.5 x ((v out C v inmin )/v out ) x (v inmin /(f sw x l)) where i inmax is the maximum input current; v out and i out are the output voltage and current, respectively; e is the estimated efficiency (which is lower at low input voltages due to higher resistive losses); v inmin is the minimum value of the input voltage; f sw is the switching frequency; and l is the minimum value of the chosen inductor. boost converter compensation refer to application note 5587: selecting external components and compensation for automotive step-up dc-dc regulator with preboost reference design . sepic operation for a reference example of using the devices in sepic mode, see figure 2 . maxim integrated 15 www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers
figure 2. sepic bootstrapped 400khz application with low operating voltage figure 3. application with independent output overvoltage protection maxim integrated 16 max16990auba max16990aubb n n drv sup gnd 1f battery input 2.5v- 40v pvl pgood pvl fset/sync fb en enable comp isns 470? 22m? 69k? 3k? 330pf 5v/2a 10k? 12k? 10h 22f 27h 33f 24x7f ceramic 2.2f synco refin max16990/ 2_atc n drv sup gnd v out input ovp pvl fset/ sync fb en enable comp isns www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers
overvoltage protection the c and d variants of the devices include the over - voltage protection input. when the ovp pin goes above 110% of the fb regulation voltage, all switching is dis - abled. for an example application circuit, see figure 3 . multiphase operation two boost phases can be implemented with no extra components using two ics as shown in figure 4 . in this circuit the synco output of the master device drives the sync input of the slave forcing it to operate 180 n out-of- phase. the fb pin of the slave device is connected to pvl, thus disabling its error amplifier. in this way the error amplifier of the master controls both devices by means of the comp signal and good current-sharing is attained between the two phases. when designing the pcb for a multiphase converter it is important to protect the comp trace in the layout from noisy signals by placing it on an inner layer and surrounding it with ground traces. using refin to adjust the output voltage the refin pin can be used to directly adjust the reference voltage of the boost converter, thus altering the output voltage. when not used, refin should be connected to pvl. because refin is a high-impedance pin, it is simple to drive it by means of an external digital- to-analog converter (dac) or a filtered pwm signal. figure 4. two-phase 400khz boost application with minimum component count maxim integrated 17 max16992_atc n max16992_atc drv sup gnd synco 2x47f ceramic 50v/1a vin pgood pvl fset/sync en comp isns 2200? 20m? 69k? fb 10k? 1f 10h 22f 2.2f n n drv sup gnd pgood pvl refin fset/ sync fb en enable comp isns 2200? 20m? synco 75k? 1500? 10h 1f 22f 2.2f www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers
ordering information /v denotes an automotive qualified part. + denotes a lead(pb)-free/rohs-compliant package. * ep = exposed pad. chip information process: bicmos package information for the latest package outline information and land patterns (foot - prints), go to www.maximintegrated.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. power dissipation the power dissipation of the ic comes from two sources: the current consumption of the ic itself and the current required to drive the external mosfet, of which the latter is usually dominant. the total power dissipation can be estimated using the following equation: p ic = v sup x i cc + (v sup C 5) x (q g x f sw ) where v sup is the voltage at the sup pin of the ic, i cc is the ic quiescent current consumption or typically 0.75ma (max16990) or 1.25ma (max16992), q g is the total gate charge of the chosen mosfet at 5v, and f sw is the switching frequency. p ic reaches it maximum at maximum v sup . maxim integrated 18 part frequency range ovp/ synco spread spectrum temp range pin-package max16990 auba/v+ 220khz to 1mhz none off -40 n c to +125 n c 10 f max-ep* max16990aubb/v+ 220khz to 1mhz none on -40 n c to +125 n c 10 f max-ep* max16990atcc/v+ 220khz to 1mhz ovp off -40 n c to +125 n c 12 tqfn-ep* max16990atcd/v+ 220khz to 1mhz ovp on -40 n c to +125 n c 12 tqfn-ep* max16990atce/v+ 220khz to 1mhz synco off -40 n c to +125 n c 12 tqfn-ep* max16990atcf/v+ 220khz to 1mhz synco on -40 n c to +125 n c 12 tqfn-ep* max16992 auba/v+ 1mhz to 2.5mhz none off -40 n c to +125 n c 10 f max-ep* max16992aubb/v+ 1mhz to 2.5mhz none on -40 n c to +125 n c 10 f max-ep* max16992atcc/v+ 1mhz to 2.5mhz ovp off -40 n c to +125 n c 12 tqfn-ep* max16992atcd/v+ 1mhz to 2.5mhz ovp on -40 n c to +125 n c 12 tqfn-ep* max16992atce/v+ 1mhz to 2.5mhz synco off -40 n c to +125 n c 12 tqfn-ep* max16992atcf/v+ 1mhz to 2.5mhz synco on -40 n c to +125 n c 12 tqfn-ep* package type package code outline no. land pattern no. 12 tqfn-ep t1233+4 21-0136 90-0019 10 f max-ep u10e+3 21-0109 90-0148 www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers
revision history ? 2015 maxim integrated products, inc. 19 revision number revision date description pages changed 0 3/13 initial release 1 4/13 added ep to max package in pin description 9C11 2 4/13 corrected errors in tocs 21 and 29 7, 8 3 7/13 removed future product asterisks from ordering information 18 4 2/15 update the benefits and features section 1 5 7/15 corrected value in figure 2, changing inductor value from 22 m f to 22 m h 16 6 8/15 corrected part number in typical application circuit 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 specifcations without notice 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. max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim integrateds website at www.maximintegrated.com.
maxim integrated 20 www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers
maxim integrated 21 www.maximintegrated.com max16990/max16992 36v, 2.5mhz automotive boost/ sepic controllers

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