View MIC45212_7725525.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

MIC45212 - 1/ - 2 26v/14a dc - to - dc power module hyper speed control is a trademark of micrel, inc . hyperlight load is a registered trademark of micrel, inc. micrel inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? tel +1 (408) 944 - 0800 ? fax + 1 (408) 474 - 1000 ? http://www.micrel.com april 28, 2014 revision - 1.0 general description micrels mic 45212 is a synchronous step - down regulator module, featuring a unique adaptive on - time control architecture. the module incorporates a dc - to - dc controller, power mosfets, bootstrap diode, bootstrap capacitor , and an inductor in a single package; simplifying the design and layout process for the end user. this highly - integrated solution expedites system design and improves product time - to - market. the internal mosfets and inductor are optimized to achieve high efficiency at a low output voltage. t he fully - optimized design can deliver up to 14 a current under a wide input voltage range of 4.5v to 26v, without requiring additional cooling. the mic 45212 - 1 uses micrel s hyperlight load ? (hll) while the mic 45212 - 2 uses micrel s hyper speed control ? architecture , which enables ultra - fast load transient response , allowing for a reduction of output capacitance. the mic 45212 offers 1% output accuracy that can be adjusted from 0.8v to 5.5v with two external resistors. additional features include thermal shutdown protection , input undervoltage lockout, adjustable current limit, and short circuit protection. the mic 45212 allows for safe start - up into a pre - biase d output. datasheet and other support documentation can be found on micrels web site at: www.micrel.com . features ? no compensation required ? up to 14 a output current ? >93% peak efficiency ? output voltage: 0.8v to 5.5v with 1% accuracy ? adjustable switching frequency from 200khz to 600khz ? enable input and open - drain power good output ? hyper speed control ? (mic 45212 - 2) architecture enables fast transient response ? hyperlight load ? (mic 45212 - 1) improves light load efficiency ? supports safe startup into pre - biased output ? cispr22, class b compliant ? C 40 ? c to +125 ? c junction temperature range ? thermal - shutdown protection ? short - circuit protection with hiccup mode ? adjustable current limit ? available in 64 - pin 12 mm 12 mm 4 mm qfn package applications ? high power density point - of - load conversion ? servers, routers , n etworking , and base stations ? fpgas, dsp, and low - voltage asic power supplies ? industrial and medical equipment typical application 10 20 30 40 50 60 70 80 90 100 0 2 4 6 8 10 12 14 16 18 20 efficiency (%) output current (a) efficiency vs. output current (MIC45212 - 1) f sw = 600khz 5.0v out 3.3v out 2.5v out 1.8v out 1.2v out 1.0v out 0.8v out 1.5v out
micrel, inc. mic 45212 april 28, 2014 2 revision - 1.0 ordering information ( 1 ) part number switching f requency features junction temperature range package lead finish mic 45212 - 1 ym p 2 00khz to 600khz hyper light load C 40c to +125c 64 - pin 12 mm 12 mm 4 mm qfn pb - free mic 45212 - 2ym p 200khz to 600khz hyper speed control C 40c to +125c 64 - pin 12 mm 12 mm 4 mm qfn pb - free note: 1. devices are esd sensitive. handling precautions are recommended. human body model, 1.5k ? in series with 100pf. pin configuration 64 - pin 12 mm 12 mm 4 mm qfn (top view) v o u t p v i n g n d v i n e n p g o o d f b f r e q 5 v d d 5 v d d g n d b s t b s t n c b s t a n o d e v o u t v o u t v o u t v o u t v o u t v o u t v o u t v o u t v o u t p v i n p v i n p v i n p v i n p v i n p v i n p v i n p v i n p v i n p v i n s w s w s w s w s w p g n d p g n d i l i m p v d d p v d d g n d v o u t v o u t v o u t v o u t v o u t s w s w s w s w s w s w s w s w r i a r i a r i b a n o d e a n o d e 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2 5 1 5 2 5 3 5 4 5 5 5 6 5 7 5 8 5 9 6 0 6 1 6 2 6 3 6 4 3 3 3 4 3 5 3 6 3 7 3 8 3 9 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 5 0 m i c 4 5 2 1 2
micrel, inc. mic 45212 april 28, 2014 3 revision - 1.0 pin description pin number pin name pin function 1, 56, 64 gnd analog ground. connect bottom feedback resistor to gnd. gnd and pgnd should be connected together at a low impedance point. 2, 3 pvdd pvdd: supply input for the internal low - side power mosfet driver. 4 ilim current limit: connect a resistor between ilim and sw to program the current limit. 5, 6 pgnd power ground. pgnd is the re turn path for the step - down power module power stage. the pgnd pin connects to the sources of internal low - side power mosfet, the negative terminals of input capacitors, and the negative terminals of output capacitors. 7 - 11, 38 - 45 sw the sw pin connects directly to the switch node. due to the high - speed switching on this pin, the sw pin should be routed away from sensitive nodes. the sw pin also senses the current by monitoring the voltage across the low - side mosfet during off time. 12 - 22 pvin power inp ut voltage: connection to the drain of the internal high side power mosfet. connect an input capacitor from pvin to pgnd. 2 3 - 37 vout power output voltage: connected to the internal inductor, the output capacitor should be connected from this pin to pgnd a s close to the module as possible. 46, 47 ria ripple injection pin a. leave floating, no connect ion . 48 rib ripple injection pin b. connect this pin to fb . 49 - 51 anode anode bootstrap diode: anode connection of internal bootstrap diode, this pin should be connected to the pvdd pin. 5 2 - 54 bst connection to the internal bootstrap circuitry and high side power mosfet drive circuitry. leave floating, no connect ion . 55 nc no connection. 5 7 fb feedback: input to the transconductance amplifier of the control loop. the fb pin is referenced to 0.8v. a resistor divider connecting the feedback to the output is used to set the desired output voltage. connect the bottom resistor from fb to gnd. 5 8 pg power good: open drain output. if used, connect to an external pull - up resistor of at least 10kohm between pg and the external bias voltage. 59 en enable: a logic signal to enable or disable the step - down regulator module operation. the en pin is ttl/cmos compatible. logic high = enable, logic low = disable or shu tdown. do not leave floating 6 0 vin internal 5v linear regulator input. a 1f ceramic capacitor from vin to gnd is required for decoupling. 6 1 freq switching frequency adjust: use a resistor divider from vin to gnd to program the switching frequency. connecting freq to vin sets freq=600khz. 62, 63 5vdd internal +5v linear regulator output. powered by vin, 5vdd is the internal supply bus for the device. in the applications with vin<+5.5v, 5 vdd should be tied to vin to by pass the lin ear regulator.
micrel, inc. mic 45212 april 28, 2014 4 revision - 1.0 absolute maximum ratings ( 2 ) v pvin , v vin to pgnd ................................ ....... ? 0.3v to +30v v pvdd , v 5vdd , v anode to pgnd ......................... ? 0.3v to +6v v sw , v freq , v ilim , v en to pgnd ............ ? 0.3v to (v in +0.3v) v bst to v sw ................................ ........................ ? 0.3v to 6v v bst to pgnd ................................ .................. ? 0.3v to 36v v pg to pgnd ................................ .. ? 0.3v to ( 5 v dd + 0.3v) v fb , v rib to pgnd .......................... ? 0.3v to ( 5 v dd + 0.3v) pgnd to gnd ................................ .............. ? 0.3v to +0.3v junction temperature ................................ .............. +150c storage temperature (t s ) ......................... ? 65 ? c to +150 ? c le ad temperature (soldering, 10s ) ............................ 260c operating ratings ( 3 ) supply voltage ( v pvin , v v in ) .............................. 4. 5 v to 26v output current ................................ ............................... 14a enable input (v en ) ................................ .................. 0v to v in power good (v pg ) ................................ ............. 0v to 5 v dd junction temperature (t j ) ........................ ? 40 ? c to +125 ? c junction thermal resistance ( 4 ) 12 mm 12 mm 4 mm qfn - 64 ( ? ja ) ............ 12.6 c/w 12 mm 12 mm 4 mm qfn - 64 ( ? jc ) .............. 3.5 c/w electrical characteristics ( 5 ) v in = v en = 12v, v out = 3.3v, v bst ? v sw = 5v, t j = +25oc. bold values indicate ? 40oc ? t j ? +125oc, unless otherwise noted. parameter condition min . typ . max . units power supply input input voltage range ( v p v in , v in ) 4.5 2 6 v quiescent supply current (mic 45212 - 1) v fb = 1.5v 0.75 ma quiescent supply current (mic 45212 - 2) v fb = 1.5v 2.1 3 ma operating current v pv in = v in = 12v, v out = 1.8v, i out = 0a, f sw = 600khz MIC45212 - 1 0.37 m a MIC45212 - 2 54 shutdown supply current sw = unconnected, v en = 0v 0.1 10 a 5vdd output 5vdd output voltage v in = 7v to 26 v, i 5vdd = 10ma 4.8 5. 1 5.4 v 5vdd uvlo threshold v 5vdd rising 3.8 4.2 4.6 v 5vdd uvlo hysteresis v 5vdd falling 400 mv ldo load regulation i 5vdd = 0 to 40ma 0.6 2 3.6 % reference feedback reference voltage t j = 25 c 0.792 0.8 0.808 v ? j 125 0.784 0.8 0.816 fb bias current v fb = 0.8v 5 500 na enable control en logic level high 1.8 v en logic level low 0.6 v en hysteresis 200 mv en bias current v en = 12v 5 10 a notes: 2. exceeding the absolute maximum rating may damage the device. 3. the device is not guaranteed to function outside operating range. 4. ? ja and ? jc were measured using the mic 45212 evaluation board. 5. specification for packaged product only.
micrel, inc. mic 45212 april 28, 2014 5 revision - 1.0 electrical characteristics ( 5 ) (continued) v in = v en = 12v, v out = 3.3v, v bst ? v sw = 5v, t j = +25oc. bold values indicate ? 40oc ? t j ? +125oc, unless otherwise noted. parameter condition min . typ . max . units oscillator switching frequency v freq = v i n , i out = 2a 400 600 750 khz v freq = 50%v i n , i out = 2a 350 maximum duty cycle 85 % minimum duty cycle v fb = 1 v 0 % minimum off - time 140 200 260 ns soft - start soft - start time 3 ms short - circuit protection current - limit threshold v fb = 0.79v ? ? 0 mv short - circuit threshold v fb = 0v ? ? 9 mv current limit source current v fb = 0.79v 50 70 90 a short circuit source current v fb = 0v 25 35 45 a leakage sw, bst leakage current 10 a freq leakage current 10 a power good (pg) pg threshold voltage sweep v fb from low - to - high 85 90 95 % v out pg hysteresis sweep v fb from high - to - low 6 % v out pg delay time sweep v fb from low - to - high 100 s pg low voltage v fb < 90% v nom , i pg = 1ma 70 200 mv thermal protection overt emperature shutdown t j rising 160 c overt emperature shutdown hysteresis 1 5 c
micrel, inc. mic 45212 april 28, 2014 6 revision - 1.0 typical characteristics 0.00 0.20 0.40 0.60 0.80 1.00 4.5 8.8 13.1 17.4 21.7 26 supply current (ma) input voltage (v) vin operating supply current vs. input voltage (MIC45212 - 1) v out = 1.8v i out = 0a f sw = 600khz 0 20 40 60 80 100 -50 -25 0 25 50 75 100 125 supply current (ma) temperature ( c) vin operating supply current vs. temperature (MIC45212 - 2) v in = 12v v out = 1.8v i out = 0a 0 10 20 30 40 50 4.5 8.8 13.1 17.4 21.7 26 shutdown current (a) input voltage (v) vin shutdown current vs. input voltage v en = 0v r10 = open 0 2 4 6 8 10 -50 -25 0 25 50 75 100 125 vdd supply voltage (v) temperature ( c) vdd supply voltage vs. temperature v in = 12v v out = 1.8v i out = 0a 0.0 0.4 0.8 1.2 1.6 2.0 -50 -25 0 25 50 75 100 125 enable threshold (v) temperature ( c) enable threshold vs. temperature falling rising v in = 12v v out = 1.8v 0 2 4 6 8 10 -50 -25 0 25 50 75 100 125 en bias current (a) temperature ( c) en bias current vs. temperature v in = 12v v out = 1.8v i out = 0a 0.5 0.6 0.7 0.8 0.9 1.0 1.1 -50 -25 0 25 50 75 100 125 feeback voltage (v) temperature ( c) feedback voltage vs. temperature v in = 12v v out = 1.8v i out = 0a 1.5 1.6 1.7 1.8 1.9 2.0 2.1 -50 -25 0 25 50 75 100 125 output voltage (v) temperature ( c) output voltage vs. temperature v in = 12v v out = 1.8v i out = 0a 300 400 500 600 700 800 900 -50 -25 0 25 50 75 100 125 switching frequency (khz) temperature ( c) switching frequency vs. temperature v in = 12v v out = 1.8v i out = 2a
micrel, inc. mic 45212 april 28, 2014 7 revision - 1.0 typical characteristics (continued) 0 2 4 6 8 10 12 14 16 18 20 -50 -25 0 25 50 75 100 125 current limit (a) temperature ( c) output peak current limit vs. temperature v in =12v v out = 1.8v f sw = 600khz r ilim = 1.69k ? 10 20 30 40 50 60 70 80 90 100 0 2 4 6 8 10 12 14 16 18 20 efficiency (%) output current (a) efficiency vs. output current (MIC45212 - 1, v in = 5v) f sw = 600khz 3.3v out 2.5v out 1.8v out 1.2v out 1.0v out 0.8v out 1.5v out 10 20 30 40 50 60 70 80 90 100 0 2 4 6 8 10 12 14 16 18 20 efficiency (%) output current (a) efficiency vs. output current (MIC45212 - 1, v in = 12v) f sw = 600khz 5.0v out 3.3v out 2.5v out 1.8v out 1.2v out 1.0v out 0.8v out 1.5v out 10 20 30 40 50 60 70 80 90 100 0 2 4 6 8 10 12 14 16 18 20 efficiency (%) output current (a) efficiency vs. output current (MIC45212 - 1, v in = 24v) f sw = 600khz 5.0v out 3.3v out 2.5v out 1.8v out 1.2v out 1.0v out 0.8v out 1.5v out 10 20 30 40 50 60 70 80 90 100 0 2 4 6 8 10 12 14 16 18 20 efficiency (%) output current (a) efficiency vs. output current (MIC45212 - 2, v in = 5v) f sw = 600khz 3.3v out 2.5v out 1.8v out 1.5v out 1.2v out 1.0v out 0.8v out 10 20 30 40 50 60 70 80 90 100 0 2 4 6 8 10 12 14 16 18 20 efficiency (%) output current (a) efficiency vs. output current (MIC45212 - 2, v in = 12v) f sw = 600khz 5.0v out 3.3v out 2.5v out 1.8v out 1.5v out 1.2v out 1.0v out 0.8v out 10 20 30 40 50 60 70 80 90 100 0 2 4 6 8 10 12 14 16 18 20 efficiency (%) output current (a) efficiency vs. output current (MIC45212 - 2, v in = 24v) f sw = 600khz 5.0v out 3.3v out 2.5v out 1.8v out 1.2v out 1.0v out 0.8v out 1.5v out 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 2 4 6 8 10 12 14 ic power dissipation (w) output current (a) ic power dissipation vs. output current vin = 5v f sw = 600khz 3.3v out 2.5v out 1.8v out 1.5v out 1.0v out 0.8v out 1.2v out 0 1 2 3 4 5 6 7 0 2 4 6 8 10 12 14 ic power dissipation (w) output current (a) ic power dissipation vs. output current vin = 12v f sw = 600khz 3.3v out 2.5v out 1.8v out 1.5v out 1.0v out 0.8v out 1.2v out 5.0v out
micrel, inc. mic 45212 april 28, 2014 8 revision - 1.0 typical characteristics (continued) 0 1 2 3 4 5 6 7 8 9 10 11 0 2 4 6 8 10 12 14 ic power dissipation (w) output current (a) ic power dissipation vs. output current vin = 24v f sw = 600khz 3.3v out 2.5v out 1.8v out 1.5v out 1.0v out 0.8v out 1.2v out 5.0v out 1.5 1.6 1.7 1.8 1.9 2.0 2.1 4.5 8.8 13.1 17.4 21.7 26.0 output voltage (v) input voltage (v) line regulation v out = 1.8v i out = 14a 1.780 1.785 1.790 1.795 1.800 1.805 1.810 0 5 10 15 output voltage (v) output current (a) load regulation (MIC45212 - 1) v out = 1.8v f sw = 600khz
micrel, inc. mic 45212 april 28, 2014 9 revision - 1.0 functional characteristics
micrel, inc. mic 45212 april 28, 2014 10 revision - 1.0 functional characteristics (continued)
micrel, inc. mic 45212 april 28, 2014 11 revision - 1.0 functional characteristics (continued)
micrel, inc. mic 45212 april 28, 2014 12 revision - 1.0 functional diagram
micrel, inc. mic 45212 april 28, 2014 13 revision - 1.0 functional description the mic 45212 is an adaptive on - time synchronous buck regulator module built for high - input voltage to low - output voltage conversion applications. the mic 45212 is designed to operate over a wide input voltage range, from 4.5v to 26v, and the output is adjustable with an external resistor divider. an adaptive on - time control scheme is employed to obtain a constant switching frequency in steady state and to simplify the control compensation. hiccup mode over - current protection is implemented by sensing low - side mosfets r ds(on) . the device features internal soft - start, enable, uvlo, and thermal shutdown. the module has integrated switching fets, inductor, bootstrap diode, resistor , capacitor , and controller. theory of operation as shown in figure 1 , in association with eq uation 1 , the output voltage is sensed by the mic 45212 feedback pin fb via the voltage divider r fb 1 and r fb 2 , and compared to a 0.8v reference voltage , v ref , at the error comparator through a low - gain transconductance (g m ) amplifier. if the feedback voltage decreases and falls below 0.8v, then the error comparator will trigger the control logic and generate an on - time period. the on - time period length is prede termined by the fixed t on estimator circuitry: figure 1 . output voltage sense via fb pin eq. 1 where v out is the output voltage, v in is the power stage input voltage, and f sw is the switching frequency. at the end of the on - time period, the internal high - side driver turns off the high - side mosfet and the low - side driver turns on the low - side mosfet. the off - time period length depends upon the feedback voltage in most cases. when the feedback voltage decreases and the output of the g m amplifier falls below 0.8v, the on - time period is triggered and the off - time period ends. if the off - time period determined by the feedback voltage is less than the minimum off - time t off(min) , wh ich is about 200ns, the mic 45212 control logic will apply the t off(min) instead. t off(min) is required to maintain enough energy in the boost capacitor (c bst ) to drive the high - side mosfet. the maximum duty cycle is obtained from the 200ns t off(min ) : eq. 2 where: t s = 1/f sw . it is not recommended to use mic 45212 with an off - time close to t off(min) during steady - state operation. the adaptive on - time control scheme results in a constant switching frequency in the mic 45212 during steady state operation . also, the minimum t on results in a lower switching frequency in high v in to v out applications. during load transients, the switching frequency is changed due to the varying off - time. to illustrate the control loop operation, we will analyze both the steady - state and load transient scenarios. for easy analysis, the gain of the g m amplifier is assumed to be 1. with this assumption, the inverting input of the error comparator is the same as the feedback voltage. figure 2 shows the mic 45212 control loop timing during steady - state operation. during steady - state, the g m amplifier senses the feedback voltage ripple, which is proporti onal to the output voltage ripple plus injected voltage ripple, to trigger the on - time period. the on - time is predetermined by the t on estimator . the termination of the off - time is controlled by the feedback voltage. at the valley of the feedback voltage r ipple, which occurs when v f b falls below v ref , the off period ends and the next on - time period is triggered through the control logic circuitry. sw in o ut ) esti m ated ( on f v v t ? ? s s ) m i n ( o ff s m ax t ns 200 1 t t t d ? ? ? ?
micrel, inc. mic 45212 april 28, 2014 14 revision - 1.0 figure 2 . mic 45212 control loop timing figure 3 shows the operation of the mic 45212 during a load transient. the output voltage drops due to the sudden load increase, which causes the v fb to be less than v ref . this will cause t he error comparator to trigger an on - time period. at the end of the on - time period, a minimum off - time t off(min ) is generated to charge the bootstrap capacitor (c bst ) since the feedback voltage is still below v ref . then, the next on - time period is triggere d due to the low feedback voltage. therefore, the switching frequency changes during the load transient, but returns to the nominal fixed frequency once the output has stabilized at the new load current level. with the varying duty cycle and switching freq uency, the output recovery time is fast and the output voltage deviation is small. note that the instantaneous switching frequency during load transient remains bounded and cannot increase arbitrarily. the minimum is limited by t on + t off (min) .since the variation in v out is relativel y limited during load transient , t on stays virtually close to its steady - state value. figure 3 . mic 45212 load transient response unlike true current - mode control, the mi c 45212 uses the output voltage ripple to trigger an on - time period. the output voltage ripple is proportional to the inductor current ripple if the esr of the output capacitor is large enough. in order to meet the stability requirements, the mic 45212 feedback voltage ripp le should be in phase with the inductor current ripple and are large enough to be sensed by the g m amplifier and the error comparator. the recommended feedback voltage ripple is 20mv~100mv over full input voltage range. if a low esr output capacitor is sel ected, then the feedback voltage ripple may be too small to be sensed by the g m amplifier and the error comparator. also, the output voltage ripple and the feedback voltage ripple are not necessarily in phase with the inductor current ripple if the esr of the output capacitor is very low. in these cases, ripple injection is required to ensure proper operation. please refer to ripple injection subsection in the application information section for more details about the ripple injection technique. discontinuous mode ( mic 45212 - 1 only) in continuous mode , the inductor current is always greater than zero; however, at light loa ds , the mic 45212 - 1 is able to force the inductor current to operate in discontinuous mode. discontinuous mode is where the inductor current falls to zero , as indicated by trace (i l ) shown in figure 4 . during this period , the efficiency is optimized by shutting down all the non - essential circuits and minimizing the supply current as the switching frequency is reduced . the mic 45212 - 1 wakes up and turns on the high - side mosfet when the feedback voltage v fb drop s below 0.8v. the mic 45212 - 1 has a zero c ross ing c omparator (zc) that monitors the inductor current by sensing the voltage drop across the low - side mosfet during its on - time. if the v fb > 0.8v and the inductor current goes slightly negative, then the mic 45212 - 1 automatically powers down most of the ic circuitry and goes into a low - power mode. once the mic 45212 - 1 goes into discontinuous mode, both dl and dh are low, which turns off the h igh - side and low - side mosfets. the load current is supplied by the output capacitors and v out drops. if the drop of v out causes v fb to go below v ref , then all the circuits will wake up into normal continuous mode. first , the b ias currents of most circuits reduced during the discontinuous mode are restored, and then a t on pulse is triggered before the drivers are turned on to avoid any possible glitches. finally, the high - side driver is turned on. figure 4 shows the control loop timing in discontinuous mode.
micrel, inc. mic 45212 april 28, 2014 15 revision - 1.0 figure 4 . mic 45212 - 1 control loop timing (discontinuous mode) during discontinuous mode, the bias current of most circuits is substantially reduced. as a result, the total power supply current during discontinuous mode is only about 350 a , allowing the mic 45212 - 1 to achieve high efficiency in light load applications. soft - start soft - start reduces the input power supply surge current at startup by controlling the output voltage rise time. the input surge appears while the output capacitor is charged up. the mic 45212 implements an internal digital soft - start by making the 0.8v reference voltage v ref ramp from 0 to 100% in about 4 ms with 9.7mv steps . therefore, the output voltage is controlled to increase slowly by a stair - case v fb ramp. once the soft - start cycle ends, the related circuitry is disabled to reduce current consumption. pv dd must be powered up at the same time or after v in to make the soft - start function correctly. current limit the mic 45212 uses the r ds(on) of the low - side mosfet and external resistor connected from ilim pin to sw node to set the current limit. figure 5 . mic 45212 current - limiting circuit in each switching cycle of the mic 45212 , the inductor current is sensed by monitoring the low - side mosfet in the off period. the sensed voltage v ilim is compared with the power ground (pgnd) after a blanking time of 150ns. in this way the drop voltage over the resistor r15 (v cl ) is compared with the drop over the bottom fet generating the shor t current limit. the small capacitor (c15) connected from ilim pin to pgnd filters the switching node ringing during the off - time allowing a better short limit measurement. the time constant created by r15 and c6 should be much less than the minimum off ti me. the v cl drop allows programming of short limit through the value of the resistor (r15). if the absolute value of the v oltage drop on the bottom fet becomes greater than v c l , and the v ilim falls below pgnd , an over - current is triggered causing the ic to enter hiccup mode . the hiccup sequence including the soft start reduces the stress on the switching fets and protects the load and supply for severe short conditions. the short - circuit current limit can be programmed by using equation 3. eq. 3 where: i clim = desired current limit r ds(on) = on - resistance of low - side power mosfet, 6 m typically . v cl = current - limit threshold (typical absolute value is 14mv per the electrical characteristics table ). ? ? cl cl ) on ( ds pp l cli m i v r ) 5 . 0 i i ( r15 ? ? ? ? ? ?
micrel, inc. mic 45212 april 28, 2014 16 revision - 1.0 i cl = current - limit source current (typical value is 70 a, per the electrical characteristics table). i l(pp) = inductor current peak - to - peak, since the inductor is integrated use eq uation 4 to calculate the inductor ripple current. the peak - to - peak inductor current ripple is: eq. 4 the mic 45212 has a 1.0h inductor integrated into the module. in case of a hard short, the short limit is folded down to allow an indefinite hard short on the output without any destructive effect. it is mandatory to make sure that the inductor current used to charge the output capacitance during soft start is under the folded s hort limit; otherwise the supply will go in hiccup mode and may not finishin the soft start successfully. the mosfet r ds(on) varies 30% to 40% with temperature; therefore, it is recommended to add a 50% margin to i clim in equation 3 to avoid false current limiting due to increased mosfet junction temperature rise. with r15= 1.69 k ? and c15=15pf, the t ypical output current limit is 16.8 a. l f v ) v (v v i sw i n( m ax) o ut i n( m ax) o ut l( pp) ? ? ? ? ? ?
micrel, inc. mic 45212 april 28, 2014 17 revision - 1.0 application information setting the switching frequency the mic 45212 switching frequency can be adjusted by chang ing the value of resistors r1 and r2. figure 6 . switching frequency adjustment equation 5 gives the estimated switching frequency: eq. 5 where: f o = 600khz(typical per electrical characteristic table) r1= 100k is recommended. r2 needs to be selected in order to set the required switching frequency. figure 7 . switching frequency vs. r2 the switching frequency also depends upon vin, vout and load conditions as mic 45212 uses and adaptive on - time architecture as explained in theory of operation. output capacitor selection the type of the output capacitor is usually determined by the application and its equivalent series resistance (esr). voltage and rms current capabili ty are two other important factors for selecting the output capacitor. recommended capacitor types are mlcc, os - con and poscap. the output capacitors esr is usually the main cause of the output ripple. the mic 45212 requires ripple injection and the output capacitor esr affects the control loop from a stability point of view. the maximum value of esr is calculated as in equation 6: eq. 6 where: v out(pp) = peak - to - peak output voltage ripple i l(pp) = peak - to - peak inductor current ripple 2 1 2 r r r f f o sw ? ? ? l(pp) out(pp) c i v esr out ? 0 100 200 300 400 500 600 700 800 10.00 100.00 1000.00 10000.00 sw freq (khz) r2 (k ? ) switching frequency v out = 5v vin = 12v r1 = 100k ?
micrel, inc. mic 45212 april 28, 2014 18 revision - 1.0 the total output ripple is a combination of the esr and output capacitance. the total ripple is calculated in equation 7: eq. 7 where: d = duty cycle c out = output capacitance value f sw = switching frequency as described in the theory of operation subsection in the functional description , the mic 45212 requires at least 20mv peak - to - peak ripple at the fb pin to make the g m amplifier and the error comparator behave properly. also, the output voltage ripple should be in phase with the inductor current. therefore, the output voltage ripple caused by the output capacitors value should be much smaller than the ripple caused by t he output capacitor esr. if low - esr capacitors, such as ceramic capacitors, are selected as the output capacitors, a ripple injection method should be applied to provide enough feedback voltage ripple. please refer to ripple injection subsection in the application information section for more details. the output capacitor rms current is calculated in equation 8: eq. 8 the pow er dissipated in the output capacitor is: eq. 9 input capacitor selection the input capacitor for the power stage input pvin should be selected for ripple curr ent rating and voltage rating. the input voltage ripple will primarily depend on the input capacitors esr. the peak input current is equal to the peak inductor current, so: v in = i l(pk) esr c in eq. 10 the input capacitor must be rated for the input current ripple. the rms value of input capacitor current is determined at the maximum output current. assuming the peak - to - peak inductor current ripple is low: eq.11 the power dissipated in the input capacitor is: p diss(c in ) = i c in (rms) 2 esr c in eq. 12 the general rule is to pick the capacitor with a ripple current rating equal to or gre ater than the calculated worst case rms capacitor current. equation 13 should be used to calculate the input capacitor. also it is recommended to keep some margin on the calculated value: eq. 13 where: dv = the input ripple f sw = s witching frequency ? ? 2 c l(pp) 2 sw out l(pp) out(pp) out esr i 8 f c i v ? ? ? ? ? ? ? ? ? ? ? ? ? 12 i i l(pp) (rms) c o ut ? o ut o ut o ut c 2 ( rm s) c ) di ss( c esr i p ? ? d) (1 d i i out(max) (rms) c in ? ? ? ? dv f d sw in ? ? ? ? ) 1 ( i c out(max)
micrel, inc. mic 45212 april 28, 2014 19 revision - 1.0 output voltage setting components the mic 45212 requires two resistors to set the output voltage as shown in figure 8 : figure 8 . voltage - divider configuration the output voltage is determined by equation 14: eq. 14 where: v fb = 0.8v a typical value of r fb 1 used on the standard evaluation board is 10k. if r1 is too large, it may allow noise to be introduced into the voltage feedback loop. if r fb 1 is too small in value, it will decrease the efficiency of the power supply, especially at light loads. once r fb 1 is selected, r fb 2 can be calculated using equation 15: eq. 15 for fixed r fb1 = 10k?, output voltage can be selected by r fb2 . table 1 provides r fb2 values for some common output voltages. table 1 . vout programming resistor look - up table r fb 2 vout open 0.8v 40.2 k ? 1.0v 20 k ? 1.2v 11.5 k ? 1.5v 8.0 6 k ? 1.8v 4.75 k ? 2.5v 3.24 k ? 3.3v 1.91 k ? 5.0v ripple injection the v fb ripple required for proper operation of the mic 45212 g m amplifier and error comparator is 20mv to 100mv. however, the output voltage ripple is generally too small to provide enough ripple amplitude at the fb pin and this issue is more visible in lower output voltage applications . if the feedback voltage ripple is so small that the g m amplifier and error comparator cannot sense it, then the mic 45212 will lose control and the output voltage is not regulated. in order to have some amount of v fb ripple, a ripple injection method is applied for low output voltage ripple applications. the applications are divided into two situations according to the amo unt of the feedback voltage ripple: 1. enough ripple at the feedback voltage due to the large esr of the output capacitors: as shown in figure 9 , the conv erter is stable without any ripple injection. figure 9 . enough ripple at fb from esr ? ? ? ? ? ? ? ? ? ? ? 2 fb 1 fb fb out r r 1 v v fb out fb1 fb fb2 v v r v r ? ? ?
micrel, inc. mic 45212 april 28, 2014 20 revision - 1.0 the feedback voltage ripple is: eq. 16 where: i l(pp) = the peak - to - peak value of the inductor current ripple 2. virtually no or inadequate ripple at the fb pin voltage due to the very - lo w esr of the output capacitors , such is the case with ceramic output capacitor. in this case, the v fb ripple waveform needs to be generated by injecting suitable signal. mic 45212 has provisions to enable an internal series rc injection network, r inj and c inj as shown in figure 10 by connecting rib to fb pin. this network injects a square - wave current waveform into fb pin, which by means of integration across the capacitor (c14) generates an ap propriate saw tooth fb rip ple waveform. figure 10 . internal ripple injection at fb via rib pin the injected ripple is: eq.17 eq.18 where: v in = power stage input voltage d = duty cycle f sw = switching frequency ? = (r fb 1 //r fb 2 //r inj ) ? c14 r inj = 10 k ? c inj = 0.1 f in equations 18 and 19, it is assumed that the time constant associated with c14 must be much greater than the switching period: eq. 19 if the voltage divider resistors r fb 1 and r fb 2 are in the k range, then a c14 of 1nf to 100nf can easily satisfy the large time constant requirements. l(pp) out c fb2 fb1 fb2 fb(pp) i esr r r r v ? ? ? ? ? ? ? ? ? ? ? sw div in fb(pp) f 1 d) - (1 d k v v fb2 fb1 inj fb2 fb1 div //r r r //r r k ? ? 1 t f 1 sw ?? ? ? ? ?
micrel, inc. mic 45212 april 28, 2014 21 revision - 1.0 thermal measurements and safe operating area (soa) measuring the ics case temperature is recommended to ensure it is within its operating limits. although this might seem like a very elementary task, it is easy to get erroneous results. the most common mistake is to use the standard thermal couple that comes with a thermal meter. this thermal couple wire gauge is large, typically 22 gauge, and behaves like a heatsink, resulting in a lower case measurement. two methods of temperature measurement are using a smaller thermal couple wire or an infrared thermometer. if a thermal couple wire is used, it must be constructed of 36 - gauge wire or higher (smaller wire size) to minimize the wire heat - sinking effect. in addition, the thermal couple tip must be covered in either thermal grease or thermal glue to make sure that the thermal couple junction is making good contact with the case of the ic. omega brand thermal couple (5sc - tt - k - 36 - 36) is adequate for most applications. wherever possible, an infrared thermometer is recommended. the measurement spot size of most infrared thermometers is too large for an accurate reading on a sm all form factor ics. however, an ir thermometer from optris has a 1mm spot size, which makes it a good choice for measuring the hottest point on the case. an optional stand makes it easy to hold the beam on the ic for long periods of time. the safe operating area (soa) of the mic 45212 is shown in figure 11 , figure 12 , figure 13 , figure 14 , and figure 15 . these thermal measurements were taken on mic 45212 evaluation board. since the mic 45212 is an entire system comprised of switching regulator controller, mosfets and inductor, the part needs to be considered as a system. the soa curves will give guidance to reasonable use of the mic 45212 . soa curves should only be used as a point of reference . soa data was acquired using the mic 45212 e valuation board. thermal performance depends on the pcb layout, board size, copper thickness, number of thermal vias, and actual airflow.
micrel, inc. mic 45212 april 28, 2014 22 revision - 1.0 figure 11 . mic 45212 power derating vs. airflow (5v in to 1.5v out ) figure 12 . mic 45212 power derating vs. airflow (12v in to 1.5v out ) figure 13 . mic 45212 power derating vs. airflow (12v in to 3.3v out ) figure 14 . mic 45212 power derating vs. airflow (24v in to 1.5v out ) figure 15 . mic 45212 power derating vs. airflow (24v in to 3.3v out ) 6 7 8 9 10 11 12 13 14 15 60 65 70 75 80 85 90 95 100 105 110 115 120 max. output current (a) ambient temperature ( c) MIC45212 power derating vs. airflow (5v in to 1.5v out ) 0 lfm 200 lfm 400 lfm 6 7 8 9 10 11 12 13 14 15 70 75 80 85 90 95 100 105 110 115 120 max. output current (a) ambient temperature ( c) MIC45212 power derating vs. airflow (12v in to 1.5v out ) 0 lfm 200 lfm 400 lfm 6 7 8 9 10 11 12 13 14 15 60 65 70 75 80 85 90 95 100 105 110 115 120 max. output current (a) ambient temperature ( c) MIC45212 power derating vs. airflow (12v in to 3.3v out ) 0 lfm 200 lfm 400 lfm 6 7 8 9 10 11 12 13 14 15 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 max. output current (a) ambient temperature ( c) MIC45212 power derating vs. airflow (24v in to 1.5v out ) 0 lfm 200 lfm 400 lfm 6 7 8 9 10 11 12 13 14 15 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 max. output current (a) ambient temperature ( c) MIC45212 power derating vs. airflow (24v in to 3.3v out ) 0 lfm 200 lfm 400 lfm
micrel, inc. mic 45212 april 28, 2014 23 revision - 1.0 pcb layout guidelines warning: to minimize emi and output noise, follow these layout recommendations. pcb l ayout is critical to achieve reliable, stable and efficient performance. a ground plane is required to control emi and minimize the inductance in power, signal and return paths. figure 16 is optimized from a small form factor point of view shows top and bottom layer of a four layer pcb. it is rec ommended to use mid layer 1 as a continuous ground plane. figure 16 . top and bottom layer of a four - layer board the following guidelines should be followed to insure proper oper ation of the mic 45212 module : ic ? the analog ground pin (gnd) must be connected directly to the ground planes. place the ic close to the point - of - load (pol). ? use thick traces to route the input and output power lines. ? analog and power grounds should be kept separate and connected at only one location with a low impedance . input capacitor ? place the input capacitors on the same side of the board and as close to the ic as possible. ? place several vias to the ground plane close to the input capacitor ground terminal. ? use either x7r or x5r diele ctric input capacitors. do not use y5v or z5u type capacitors. ? do not replace the ceramic input capacitor with any other type of capacitor. any type of capacitor can be placed in parallel with the ceramic input capacitor. ? if a non - ceramic input capacitor i s placed in parallel with the input capacitor, it must be recommended for switching regulator applications and the operating voltage . ? in hot - plug applications, a n electrolytic bypass capacitor must be used to limit the over - voltage spike seen on the inpu t supply with power is suddenly applied. if hot - plugging is the normal operation of the system, using an appropriate hot - swap ic is recommended. rc snubber (optional) ? depending on the operating conditions, a rc snubber on the same side of the board can be used. place the rc and as close to the sw pin as possible if needed. sw node ? do not route any digital lines underneath or close to the sw node. ? keep the switch node (sw) away from the feedback (fb) pin. output capacitor ? use a wide trace to connect the output capacitor ground terminal to the input capacitor ground terminal. ? phase margin will change as the output capacitor value and esr changes. ? the feedback trace should be separate from the power trace and connected as close as possible to the output ca pacitor. sensing a long high - current load trace can degrade the dc load regulation.
micrel, inc. mic 45212 april 28, 2014 24 revision - 1.0 pcb layout recommendations top ? copper layer 2
micrel, inc. mic 45212 april 28, 2014 25 revision - 1.0 pcb layout recommendations (continued) copper layer 3 bottom ?
micrel, inc. mic 45212 april 28, 2014 26 revision - 1.0 simplified pcb design recommendations 1. periphery i/o pad layout & large pad for exposed heatsink the board design should begin with copper/metal pads that sit beneath the periphery leads of a mounted qfn. the board pads should extend outside the qfn package edge a distance of approximately 0.20mm per side. total pad length = 12.00mm + (0.20mm per side x 2 sides) = 12.40 mm . after completion of the periphery pad design, the larger exposed pads will be designe d to create the mounting surface of the qfn exposed heatsink. the primary transfer of heat out of the qfn will be directly through the bottom surface of the exposed heatsink. to aid in the transfer of generated heat into the pcb, the use of an array of pla ted through - hole vias beneath the mounted part is recommended. the typical via hole diameter is 0.30 mm to 0.35mm, with center - to - center pitch of 0.80mm to 1.20 mm. note: exposed metal t race is the mirror image of package bottom v iew. 2. solder paste stencil design (recomme nd stencil thickness is 125m 25 m ) the solder stencil aperture openings should be smaller than the periphery or large pcb exposed pads to reduce any chance of build - up of excess solder at the large exposed pad area which can result to solder bridging. the suggested reduction of the stencil aperture opening is typically 0.20mm smaller than exposed metal trace. comment : cyan colored shaded pad indicate s exposed trace keep out area .
micrel, inc. mic 45212 april 28, 2014 27 revision - 1.0 critical requirement C do not duplicate land pattern for exposed m etal trace as solder s tencil o pening because the design and dimension values are different. 3. stacked - up of pad layout and solder paste stencil
micrel, inc. mic 45212 april 28, 2014 28 revision - 1.0 evaluation board schematic
micrel, inc. mic 45212 april 28, 2014 29 revision - 1.0 bill of materials item part number manufacturer description qty. c1 b41851 epcos ( 6 ) 220 f /35v ale capacitor (optional) 1 c 2, c3 grm32er71h475ka12 murata ( 7 ) 4.7 f /50v, x7r, 1210, ceramic capacitor 2 12105c475kaz2a avx ( 8 ) c3225x7r1h475k tdk ( 9 ) c4, c8 grm188r71h04ka93d murata 0.1 f /50v, x7r, 0603, ceramic capacitor 1 06035c104kat2a avx c1608x7r1h104k tdk c5, c6 grm32er60j107me20l murata 100 f /6.3v, x5r, 1210, ceramic capacitor 2 12106d107mat2a avx c3225x5r0j107m tdk c7, c13 (open) c14 c1608c0g1h222jt tdk 2.2nf/50v, x7r, 0603 1 c15 grm1885c1h150ja01d murata 15pf/50v, x7r, 0603 1 c1608c0g1h150f080aa tdk r1 0 ? 1 r2, r12, r13 (open) r3 crcw06031k91fkea vishay ( 10 ) 1.91k ? , 1%, 1/10w, 0603 1 r4 crcw06033k24fkea vishay 3.24k ?, 1%, 1/10w, 0603 1 r5 crcw06034k75fkea vishay 4.75k ?, 1%, 1/10w, 0603 1 r6 crcw06038k06fkea vishay 8.06k ?, 1%, 1/10w, 0603 1 r7 crcw060311k5fkea vishay 11.5k ?, 1%, 1/10w, 0603 1 r8 crcw06020k0fkea vishay 20k ?, 1%, 1/10w, 0603 1 r9 crcw060340k2fkea vishay 40.2k ?, 1%, 1/10w, 0603 1 r10 crcw0603100k0fkea vishay 100k ?, 1%, 1/10w, 0603 1 r11 crcw060349k9fkea vishay 49.9k ?, 1%, 1/10w, 0603 1 r14 crcw060310k0fkea vishay 10k ?, 1%, 1/10w, 0603 1 r15 crcw06031k37fkea vishay 1.69 k ?, 1%, 1/10w, 0603 1 r16 crcw060349r9fkea vishay 49.9 ?, 1%, 1/10w, 0603 1 u1 MIC45212 - 1ymp micrel, inc. ( 11 ) 26v/14a dc - to - dc module 1 MIC45212 - 2ymp 1 notes: 6. epcos: www.epcos.com 7. murata: www.murata.com 8. avx: www.avx.com 9. tdk: www.tdk.com 10. vishay: www.vishay.com 11. micrel, inc.: www.micrel.com
micrel, inc. mic 45212 april 28, 2014 30 revision - 1.0 package information ( 12 ) 64 - pin 12 mm 12mm qfn note: 12. package information is correct as of the publication date. for updates and most current information, go to www.micrel.com .
micrel, inc. mic 45212 april 28, 2014 31 revision - 1.0 micrel, inc. 2180 fortune drive san jose, ca 95131 usa tel +1 (408) 944 - 080 0 fax +1 (408) 474 - 1000 web http://www.micrel.com micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in th is data sheet. this information is not intended as a warranty and micrel does not assume responsibility for its use. micrel reserves the right to change circuitry, specifications and descriptions at any time without notice. no license, whether express, implied, arising by estoppel or otherwis e, to any intellectual property rights is granted by this document. except as provided in micrels terms and conditions of sale for such products, micrel assumes no liability purchasers use or sale of micrel products for use in life support appliances, devices or systems is a purchasers own risk and purchaser agrees to fully ? 20 14 micrel, incorporated.

▲Up To Search▲

Price & Availability of MIC45212

	To Download MIC45212 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .