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mic38300 heldo? 3a high efficiency low dropout regulator heldo is a trademark of micrel, inc. mlf and micro leadframe are registered trademark of amkor technology. micrel inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? tel +1 ( 408 ) 944-0800 ? fax + 1 (408) 474-1000 ? http://www.micrel.com june 2010 m9999-061010-d general description the mic38300 is a 3a peak, 2.2a continuous output current step down converter. this is the first device in a new generation of heldo? (high efficiency low dropout) regulators that provide the benefits of an ldo in respect to ease of use, fast transient performance, high psrr and low noise while offering the efficiency of a switching regulator. as output voltages move lower, the output noise and transient response of a switching regulator become an increasing challenge for designers. by combining a switcher whose output is slaved to the input of a high performance ldo, high efficiency is achieved with a clean low noise output. the mic38300 is designed to provide less than 5mv of peak to peak noise and over 70db of psrr at 1khz. furthermore, the architecture of the mic38300 is optimized for fast load transients that allow a maintenance of less than 30mv of output voltage deviation even during ultra fast load steps, making the mic38300 an ideal choice for low voltage asics and other digital ics. the mic38300 features a fully integrated switching regulator and ldo combo, operates with input voltages from 3.0v to 5.5v input and offers adjustable output voltages down to 1.0v. the mic38300 is offered in the small 28-pin 460.9mm mlf ? package and can operate from ?40c to +125c. datasheets and support documentation can be found on micrel?s web site at: www.micrel.com heldo? features ? 3a peak output current ? 2.2a continuous operating current ? input voltage range: 3.0v to 5.5v ? adjustable output voltage down to 1.0v ? output noise less than 5mv ? ultra fast transient performance ? unique switcher plus ldo architecture ? fully integrated mosfet switches ? micro-power shutdown ? easy upgrade from ldo as power dissipation becomes an issue ? thermal shutdown and current limit protection ? 4mm 6mm 0.9mm mlf ? package applications ? point-of-load applications ? networking, server, industrial power ? wireless base-stations ? sensitive rf applications ___________________________________________________________________________________________________________ typical application
micrel, inc. mic38300 june 2010 2 m9999-061010-d block diagram pvin sw switch control voltage reference vref ven-vref mic38300 swo lpf ldoin vout fb en agnd avin pgnd + - + - ordering information part number output current voltage (1) junction temperature range package MIC38300HYHL 3.0a adj ?40c to +125c pb-free 28-pin 4x6 mlf ? note : for additional voltage options, contact micrel.
micrel, inc. mic38300 june 2010 3 m9999-061010-d pin configuration sw 5 1 sw sw sw sw 2 3 4 10 6 7 8 9 24 28 27 26 25 23 11 19 22 21 20 18 16 13 14 15 17 12 sw swo swo swo swo swo sw fb epad avin lpf a gnd pgnd epad pgnd pgnd en pvin ldoout ldoout ldoin ldoin pvin 28-pin 4mm x 6mm mlf ? (ml) (top view) pin description pin number MIC38300HYHL pin name pin name 1, 2, 3, 4, 5 swo switch (output): this is the output of the pfm switcher. 6, 23, 24, 25, 26, 27, 28 sw switch node: attach external resi stor from lpf to increase hysteretic frequency. 7, 22 epad exposed heat-sink pad. connect externally to pgnd. 8 avin analog supply voltage: supply for the analog control circuitry. requires bypass capacitor to ground. nominal bypass capacitor is 1f. 9 lpf low pass filter: attach external re sistor from sw to increase hysteretic frequency. 10 agnd analog ground. 11 fb feedback: input to the error amplifier. connect to the external resistor divider network to set the output voltage. 12, 13 ldoout ldo output: output of voltage regulator. place capacitor to ground to bypass the output voltage. nominal bypass capacitor is 10f. 14, 15 ldoin ldo input: connect to sw output. requires a bypass capacitor to ground. nominal bypass capacitor is 10f. 16, 17 pvin input supply voltage (input): requires bypass capacitor to gnd. nominal bypass capacitor is 10f. 18 en enable (input): logic low will shut down the device, reducing the quiescent current to less than 50a. this pin can also be used as an under-voltage lockout function by connecting a resistor divider from en/uvlo pin to vin and gnd. it should be not left open. 19, 20, 21 pgnd power ground.
micrel, inc. mic38300 june 2010 4 m9999-061010-d absolute maximum ratings (1) supply voltage (v in ) .........................................................6v output switch voltage (v sw ) ...........................................6v ldo output voltage (v out ) .............................................6v logic input voltage (v en ) .................................?0.3v to vin power dissipation .................................. internally limited (3) storage temperature (t s )...................?65c t j +150c esd rating (4) .............................................................. 1.5kv operating ratings (2) supply voltage (v in ) ...................................... 3.0v to 5.5v junction temperature range .........?40c t j +125c enable input voltage (v en ) ................................. 0v to v in package thermal resistance 4mm 6mm mlf-28 ( ja ) .............................24c/w electrical characteristics (5) t a = 25c with v in = v en = 5v; i out = 10ma, v out = 1.8v. bold values indicate ?40c t j +125c, unless noted. parameter conditions min typ max units supply voltage range 3.0 5.5 v under-voltage lockout threshold turn-on 2.85 v uvlo hysteresis 100 mv quiescent current i out = 0a, not switching, open loop 1 ma turn-on time v out to 95% of nominal 200 500 s shutdown current v en = 0v 30 50 a feedback voltage 2.5% 0.975 1 1.025 v feedback current 5 na dropout voltage (v in ? v out ) i load = 2.2a; v out = 3v 0.85 1.2 v current limit v fb = 0.9v nom 3 5 a output voltage load regulation v out = 1.8v, 10ma to 2.2a 0.3 1 % output voltage line regulation v out = 1.8v, v in from 3.0v to 5.5v 0.35 0.5 %/v output ripple i load = 1.5a, c outldo = 20f, c outsw = 20f lpf=25k ? 2 mv over-temperature shutdown 150 c over-temperature shutdown hysteresis 15 c enable input (6) enable input threshold regulator enable 0.90 1 1.1 v enable hysteresis 20 100 200 mv enable input current 0.03 1 a notes: 1. exceeding the absolute maximum rating may damage the device. 2. the device is not guaranteed to function outside its operating rating. 3. the maximum allowable power dissipation of any t a (ambient temperature) is p d(max) = (t j(max) ? t a ) / ja . exceeding the maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. 4. devices are esd sensitive. handling precautions recommended. human body model, 1.5k in series with 100pf. 5. specification for packaged product only. 6. enable pin should not be left open.
micrel, inc. mic38300 june 2010 5 m9999-061010-d typical characteristics v in = 3.3v, v out = 1.8v, c out = 10f, r lpf = 25k ? , i out = 100ma, unless noted 0 10 20 30 40 50 60 70 80 90 10 100 1k 10k 100k frequency (hz) mic38300 psrr 1.780 1.785 1.790 1.795 1.800 1.805 1.810 1.815 1.820 0 0.5 1.0 1.5 2.0 2.5 3.0 load current (a) load regulation v in = 3.3v v out = 1.8v c out = 10f 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 012345 input voltage (v) output voltage vs. input voltage v out = 1.8v c out = 10f 10ma 2a 1.72 1.74 1.76 1.78 1.80 1.82 1.84 1.86 1.88 output voltage vs. temperature 20 40 60 80 temperature (c) v in = 3.3v c out = 10f i out = 10ma 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 -40 10 60 110 160 210 temperature (c) thermal shutdown v in = 3.3v v out = 1.8v c out = 10f 0 10 20 30 40 50 60 70 80 90 0 0.5 1.0 1.5 2.0 2.5 3.0 load current (a) mic38300 efficiency v in = 5v v out = 3.3v c out = 10f 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 0.5 1.0 1.5 2.0 2.5 3.0 load current (a) dropout voltage vs. load current v in = 3.3v c out = 20f r lpf 0.4 0.5 0.6 0.7 0.8 0.9 1.0 dropout voltage vs. temperature 20 40 60 80 temperature (c) v out = 4v c out = 20f 2a 1a 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 input voltage (v) current limit vs. input voltage v out = 1v c out = 20f r lpf 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 3.0 3.5 4.0 4.5 5.0 5.5 input voltage (v) enable threshold v out = 1.8v c out = 10f 0 10 20 30 40 50 60 33.544.555.5 operating current (ma) input voltage (v) operating current vs. input voltage v out = 1.8v c out = 10f
micrel, inc. mic38300 june 2010 6 m9999-061010-d typical characteristics v in = 3.3v, v out = 1.8v, c out = 10f, r lpf = 25k ? , i out = 100ma, unless noted 0 0.5 1 1.5 2 2.5 3 10 100 1000 switch frequency (mhz) rlpf resistance (kohms) switch frequency vs. rlpf resistance (3.3v-1.0v) 10ma 500ma 1a 1.5a 2a 0 0.5 1 1.5 2 2.5 3 10 100 1000 switch frequency (mhz) rlpf resistance (kohms) switch frequency vs. rlpf resistance (3.3v-1.8v) 10ma 500ma 1a 1.5a 2a 0 0.5 1 1.5 2 2.5 3 10 100 1000 switch frequency (mhz) rlpf resistance (kohms) switch frequency vs. rlpf resistance (5.0v-1.0v) 10ma 500ma 1a 1.5a 2a 0 0.5 1 1.5 2 2.5 3 10 100 1000 switch frequency (mhz) rlpf resistance (kohms) switch frequency vs. rlpf resistance (5.0v-1.8v) 10ma 500ma 1a 1.5a 2a 0 0.5 1 1.5 2 2.5 3 10 100 1000 switch frequency (mhz) rlpf resistance (kohms) switch frequency vs. rlpf resistance (5.0v-2.5v) 10ma 500ma 1a 1.5a 2a 0 0.5 1 1.5 2 2.5 3 3.5 -40-200 20406080 max output current (a) ambient temperature (c) max output current @ 110c case temp (1.0v vout) 5.5v 3.3v 5.0v 0 0.5 1 1.5 2 2.5 3 3.5 -40-200 20406080 max output current (a) ambient temperature (c) max output current @ 110c case temp (1.2v vout) 5.5v 3.3v 5.0v 0 0.5 1 1.5 2 2.5 3 3.5 -40-200 20406080 max output current (a) ambient temperature (c) max output current @ 110c case temp (1.8v vout) 5.5v 5.0v 0 0.5 1 1.5 2 2.5 3 3.5 -40-200 20406080 max output current (a) ambient temperature (c) max output current @ 110c case temp (2.5v vout) 5.5v 5.0v
micrel, inc. mic38300 june 2010 7 m9999-061010-d functional characteristics v in = 3.3v, v out = 1.8v, c out = 10f, inductor = 470nh; r lpf = 25k ? , i out = 100ma, unless noted
micrel, inc. mic38300 june 2010 8 m9999-061010-d emi performance v out =1.8v, i out =1.2a emi test ? horizontal front emi test ? vertical front additional components to mic38150 evaluation board (performance similar to mic38300): 1. input ferrite bead inductor. part number: blm21ag102sn1d 2. 0.1f and 0.01f ceramic bypass capacitors on pvin, sw, swo, and ldoout pins.
micrel, inc. mic38300 june 2010 9 m9999-061010-d application information enable input the mic38300 features a ttl/cmos compatible positive logic enable input for on/off control of the device. high enables the regulator while low disables the regulator. in shutdown the regulator consumes very little current (only a few microamperes of leakage). for simple applications the enable (en) can be connected to v in (in). input capacitor pvin provides power to the mosfets for the switch mode regulator section and the gate drivers. due to the high switching speeds, a 10f capacitor is recommended close to pvin and the power ground (pgnd) pin for bypassing. analog v in (avin) provides power to the analog supply circuitry. avin and pvin must be tied together externally. careful layout should be considered to ensure high frequency switching noise caused by pvin is reduced before reaching avin. a 1f capacitor as close to avin as possible is recommended. output capacitor the mic38300 requires an output capacitor for stable operation. as a cap ldo, the mic38300 can operate with ceramic output capacitors of 10f or greater. values of greater than 10f improve transient response and noise reduction at high frequency. x7r/x5r dielectric-type ceramic capacitors are recommended because of their superior temperature performance. x7r-type capacitors change capacitance by 15% over their operating temperature range and are the most stable type of ceramic capacitors. larger output capacitances can be achieved by placing tantalum or aluminum electrolytics in parallel with the ceramic capacitor. for example, a 100f electrolytic in parallel with a 10f ceramic can provide the transient and high frequency noise performance of a 100f ceramic at a significantly lower cost. specific undershoot/overshoot performance will depend on both the values and esr/esl of the capacitors. for less than 5mv noise performance at higher current loads, 20f capacitors are recommended at ldoin and ldoout. low pass filter pin the mic38300 features a low pass filter (lpf) pin for adjusting the switcher frequency. by tuning the frequency, the user can further improve output ripple without losing efficiency. adjusting the frequency is accomplished by connecting a resistor between the lpf and sw pins. a small value resistor would increase the frequency while a larger value resistor decreases the frequency. recommended r lpf value is 25k ? . please see typical characteristics for more details. adjustable regulator design adjustable regulator with resistors the adjustable mic38300 output voltage can be programmed from 1v to 5.0v using a resistor divider from output to the fb pin. resistors can be quite large, up to 100k ? because of the very high input impedance and low bias current of the sense amplifier. for large value resistors (>50k ? ) r1 should be bypassed by a small capacitor (c ff = 0.1f bypass capacitor) to avoid instability due to phase lag at the adj/sns input. the output resistor divider values are calculated by: ? ? ? ? ? ? + = 1 2 1 1 r r v v out efficiency considerations efficiency is defined as the amount of useful output power, divided by the amount of power supplied. 100 % _ ? ? ? ? ? ? ? ? = in in out out i v i v efficiency maintaining high efficiency serves two purposes. it reduces power dissipation in the power supply, reducing the need for heat sinks and thermal design considerations and it reduces consumption of current for battery powered applications. reduced current draw from a battery increases the devices operating time and is critical in hand held devices. there are two types of losses in switching converters; dc losses and switching losses. dc losses are simply the power dissipation of i 2 r. power is dissipated in the high side switch during the on cycle. power loss is equal to the high side mosfet r dson multiplied by the switch current 2 . during the off cycle, the low side n-channel mosfet conducts, also dissipating power. device operating current also reduces efficiency. the product of the quiescent (operating) current and the supply voltage is another dc loss. over 100ma, efficiency loss is dominated by mosfet r dson and inductor losses. higher input supply voltages will increase the gate to source threshold on the internal mosfets, reducing the internal rd dson . this improves efficiency by reducing dc losses in the device. all but the inductor losses are inherent to the device. in which
micrel, inc. mic38300 june 2010 10 m9999-061010-d case, inductor selection becomes increasingly critical in efficiency calculations. as the inductors are reduced in size, the dc resistance (dcr) can become quite significant. the dcr losses can be calculated as follows: l_p d = i out 2 dcr from that, the loss in efficiency due to inductor resistance can be calculated as follows; 100 _ 1 _ ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? + ? = d out out out out p l i v i v loss efficiency efficiency loss due to dcr is minimal at light loads and gains significance as the load is increased. inductor selection becomes a trade-off between efficiency and size in this case. current sharing circuit the following circuit allows two mic38300 heldo regulators to share the load current equally. heldo1 senses the output voltage at the load, on the other side of a current sense resistor. as the load changes, a voltage equal to the output voltage, plus the load current times the sense resistor, is developed at the v out terminal of heldo1. the op-amp (mic7300) inverting pin senses this voltage and compares it to the voltage on the v out terminal of heldo2. if the current through the current sense of heldo2 is less than the current through the current sense of heldo1, the inverting pin will be at a higher voltage than the non-inverting pin and the op-amp will drive the fb of heldo2 low. the low voltage sensed on heldo2 fb pin will drive the output up until the output voltage of heldo2 matches the output voltage of heldo1. since v out will remain constant and both heldo v out terminals and sense resistances are matched, the output currents will be shared equally current sharing circuit for 6a output
micrel, inc. mic38300 june 2010 11 m9999-061010-d package information 28-pin 4mm x 6mm mlf ? (ml)
micrel, inc. mic38300 june 2010 12 m9999-061010-d recommended landing pattern lp # hmlf46t-28ld-lp-1 all units are in mm tolerance 0.05 if not noted red circle indicates thermal via. size should be .300-.350 mm in diameter and it should be connected to gnd plane for maximum thermal performance. micrel, inc. 2180 fortune drive san jose, ca 95131 us a tel +1 (408) 944-0800 fax +1 (408) 474-1000 web http:/www.micrel.com the information furnished by micrel in this data sheet is believed to be accurate and reliable. however, no responsibility is a ssumed by micrel for its use. micrel reserves the right to change circuitry and specifications at any time without notification to the customer. micrel products are not designed or authorized for use as components in life support appliances, devices or systems where malfu nction of a product can reasonably be expected to result in personal injury. life support devices or systems are devices or systems that (a) are in tended for surgical implan t into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significan t injury to the user. a purchaser?s use or sale of micrel products for use in life support appliances, devices or systems is a purchaser?s own risk and purchaser agrees to fully indemnify micrel for any damages resulting from such use or sale. ? 2007 micrel, incorporated.

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