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mic2253 3.5a 1mhz high efficiency boost regulator with ovp and softstart mlf and micro leadframe are registered trademarks of amkor technology, 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 2011 m9999-042011-c general description the mic2253 is a high power density 1mhz pwm dc/dc boost regulator. the 3.5a minimum switch current limit combined with a 1mhz switching frequency allows the mic2253 to use smaller indu ctors and deliver high power in a tiny solution size. the 2.5v to 10v input voltage range of mic2253 allows direct operation from 1 and 2 cell li-ion as well as 3 to 4 cell nicad, nimh, alkaline or lithium batteries. maximum battery life is assured with a low 0.1a shutdown current. the mic2253 is available in a low profile 12-pin 3mm x 3mm mlf ? package. to prevent a high inrush current, a minimum 1ms soft-start period is set by default and the mic2253 has the ability to extend the soft-start period with an external capacitor. datasheet and support documentation can be found on micrel?s web site at: www.micrel.com. features ? 3.5a minimum switch current ? 1.245v 3% feedback voltage ? 2.5v to 10v input voltage ? output over-voltage protection (ovp) ? externally programmable soft-start ? output voltage up to 30v (max) ? fixed 1mhz operation ? <1% line regulation ? 0.1a shutdown current ? over temperature protection ? under-voltage lockout (uvlo) ? 12-pin 3mm x 3mm leadless mlf ? package ? ?40 c to +125 c junction temperature range applications ? mobile handsets ? portable media/mp3 players ? portable navigation devices (gps) ? wifi/wimax/wibro modules ? digital cameras ? wireless lan cards ? usb powered devices ? portable applications ___________________________________________________________________________________________________________ typical application
micrel, inc. mic2253 april 2011 2 m9999-042011-c ordering information part number marking code (2) ovp junction temp. range package lead finish mic2253-06yml 06 2253 6v ?40 to +125c 12-pin 3x3 mlf ? pb-free note: mlf ? is a green rohs compliant package. lead fini sh is nipdau. mold compound is halogen free. pin configuration 12-pin 3mm x 3mm mlf ? (ml) (top view) pin description pin number pin name pin function 1 nc no connect. not internally connected. 2 ss soft start (input). connect a capacitor to g nd to slowly turn on the device. the higher the capacitance, the longer the turn-on time. 3 fb feedback (input): output voltage sense node. connect external resistors to set the output voltage. nominal feedback voltage is 1.245v. 4 agnd analog ground 5,6 pgnd power ground 7,8 sw switch node: internal power bipolar collector. 9 ovp over-voltage protection (ovp): connec t to the output voltage to clamp the maximum output voltage. a resistor divider from this pin to ground could be used to raise the ovp level beyond 6v (max). 10 vin supply (input): 2.5v to 10v for internal circuitry. 11 en enable (input): applying 1.5v or gr eater enables the regulator. applying a voltage of 0.4v or less disables t he mic2253. do not leave floating. 12 comp compensation pin (input): add extern al r and c to gnd to stabilize the converter. ep hs pad exposed heat-sink pad.
micrel, inc. mic2253 april 2011 3 m9999-042011-c absolute maximum ratings (1) supply voltage (v in ) .......................................................12v switch voltage (v sw )....................................... ?0.3v to 34v enable voltage (v en )....................................... ?0.3v to 12v fb voltage (v fb )...............................................................6v switch current (i sw ) ..................................interna lly limited ambient storage temperature (t s ) ...........?65c to +150c esd rating (3) .................................................................. 2kv operating ratings (2) supply voltage (v in ).......................................... 2.5v to 10v enable voltage (v en ).............................................. 0v to v in junction temperature (t j ) ........................ ?40c to +125c package thermal impedance 3mm x 3mm mlf-12 ( ja ) .................................60c/w electrical characteristics (4) t a = 25c; v in = v en = 3.6v; unless otherwise noted. bold values indicate ?40c t j +125c. symbol parameter condition min typ max units v in supply voltage range 2.5 10 v v uvlo under-voltage lockout 1.8 2.1 2.4 v v ovp over-voltage protection 5.25 5.6 6.3 v i vin quiescent current v fb >1.245v, not switching 15 23 ma i sd shutdown current v en = 0v (5) 0.1 1 a v fb feedback voltage 1.208 1.245 1.283 v i fb feedback input current v fb = 1.245v -450 na line regulation 3.0v v in 4.5v 0.5 % d min minimum duty cycle 10 % d max maximum duty cycle 90 % i sw switch current limit v in = 3.6v 3.5 4.75 8 a v sw switch saturation voltage v in = 3.6v, i sw = 3.5a 350 500 mv i sw switch leakage current v en = 0v, v sw = 10v 0.01 10 a turn on 1.5 v en enable threshold turn off 0.4 v i en enable pin current v en = 10v 20 40 a f sw oscillator frequency 0.8 1 1.2 mhz i ss soft start v ss = 0v 30 a 150 c t j over-temperature threshold shutdown hysteresis 10 c notes: 1. absolute maximum ratings indicate limits beyond which damage to the component may occur. electrical specifications do not apply when operating the device outside of its operating ratings. the maximum a llowable power dissipation is a f unction of the maximum junctio n temperature, t j(max) , the junction-to-ambient thermal resistance, ja , and the ambient temperature, t a . the maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. 2. the device is not guaranteed to function outside its operating rating. 3. devices are esd sensitive. handling pr ecautions recommended. human body model, 1.5k ? in series with 100pf. 4. specification for packaged product only. 5. i sd = i vin
micrel, inc. mic2253 april 2011 4 m9999-042011-c typical characteristics frequency vs. input voltage 500 600 700 800 900 1000 1100 1200 1300 1400 1500 2.5 4.0 5.5 7.0 8.5 10.0 input voltage (v) frequency (khz) v out = 12v i out = 300ma l = 2.2h c = 22f frequency vs. temperature 700 800 900 1000 1100 1200 -40-20 0 20406080100120 temperature (c) frequency ( khz) v out = 5v v in = 3.6v load = 200ma feedback voltage vs. temperature 1.20 1.21 1.22 1.23 1.24 1.25 1.26 1.27 1.28 1.29 1.30 -40 -20 0 20 40 60 80 100 120 temperature (c) feedback voltage (v) v out = 5v v in = 3.6v load = 200ma load regulation 4.90 4.92 4.94 4.96 4.98 5.00 5.02 5.04 5.06 5.08 5.10 0 400 800 1200 1600 output current (ma) output voltage (v) v out = 5v l = 2.2h c = 22f t a = 25c current limit vs. input voltage 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0 2.5 4.0 5.5 7.0 8.5 10.0 input voltage (v) sw current limit (a) v out = 12v l = 2.2h c = 22f t a = 25c efficiency v out = 3.8v 0 10 20 30 40 50 60 70 80 90 100 0 600 1200 1800 2400 output current (ma) efficiency (%) v in =2.5v v in =3v v in =3.3v l = 2.2h c = 22f t a = 25c efficiency v out =12.0v 30 40 50 60 70 80 90 0 200 400 600 800 1000 1200 output current (ma) efficiency (%) v in =3.3v v in =4.2v v in =5v l = 2.2h c = 22f t a = 25c efficiency v out =15.0v 30 40 50 60 70 80 90 0 100 200 300 400 500 600 700 output current (ma) efficiency (%) v in =3.3v v in =4.2v v in =5v l = 2.2h c = 22f t a = 25c efficiency v out =5.0v 20 30 40 50 60 70 80 90 0 600 1200 1800 2400 output current (ma) efficiency (%) v in =2.5v v in =3.6v v in =4.5v l = 2.2h c = 22f t a = 25c quiescent current vs. temperature 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 16.0 16.5 17.0 -40 -20 0 20 40 60 80 100 120 temperature(c) quiescent current ( ma) v in = 3.6v v fb = 2.5v not switching quiescent current vs. input voltage 11.0 12.0 13.0 14.0 15.0 16.0 17.0 2.5 4.0 5.5 7.0 8.5 10.0 input voltage (v) quiescent current (ma) v fb = 2.5v not switching line regulation 11.5 11.6 11.7 11.8 11.9 12.0 12.1 12.2 12.3 12.4 12.5 2.54.05.57.08.510.0 input voltage (v) output voltage (v) v out = 12v l = 2.2h c = 22f t a = 25c load = 20ma
micrel, inc. mic2253 april 2011 5 m9999-042011-c typical characteristics (continued) enable t hreshold vs. input voltage 1.20 1.22 1.24 1.26 1.28 1.30 1.32 1.34 1.36 1.38 1.40 2.5 4.0 5.5 7.0 8.5 10.0 input voltage (v) enable threshold (v) v out = 12v i out = 20ma l = 2.2h c = 22f saturation voltage vs. switch current 0 50 100 150 200 250 300 350 400 450 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 switch current (a) saturation voltage (mv) v in = 2.5v t a = 25c
micrel, inc. mic2253 april 2011 6 m9999-042011-c functional characteristics
micrel, inc. mic2253 april 2011 7 m9999-042011-c functional diagram functional description the mic2253 is a constant frequency, pulse-width- modulated (pwm) peak current-mode step-up regulator. the device?s simplified control scheme is illustrated in the block diagram above. a reference voltage is fed into the pwm engine where the duty cycle output of the constant frequency pwm engine is computed from the error, or difference, between the ref and fb voltages. the pwm engine encompasses the necessary circuit blocks to implement a current-mode boost switching power supply. the necessary circuit blocks include, but are not limited to, an oscillator/ramp generator, slope compensation ramp generator, g m error amplifier, current amplifier, pwm comparator, and drive logic for the internal 3.5a bipolar power transistor. inside the pwm engine, the osc illator functions as a trigger for the pwm comparator that turns on the bipolar power transistor and resets the slope compensation ramp generator. the current amplifier is used to measure the power transistor?s current by amplifying the voltage signal from the sense resistor conne cted to the emitter of the bipolar power transistor. the output of the current amplifier is summed with the output of the slope compensation ramp generator where the result is connected to one of the inputs of the pwm comparator. the g m error amplifier measures the feedback voltage through the external resistor and amplifies the error between the detected voltage signal from the feedback and the internal reference voltage. the output of the g m error amplifier provides the voltage loop signal that is fed to the other input of the pwm comparator. when the current loop signal exceeds the voltage loop signal the pwm comparator turns off the power transistor. the next oscillator/clock period initiate s the next switching cycle, maintaining the constant frequency current-mode pwm control. the enable pin shuts down the output switching and disables control circuitry to reduce input current-to- leakage levels. enable pin input current is approximately zero, at zero volts. dc-to-dc pwm boost conversion the mic2253 is a constant-fre quency boost converter. it can convert a low dc input voltage to a high dc output voltage. figure 1 shows a typical circuit. boost regulation is achieved by turning on an internal switch, which draws current through the inductor. when the switch turns off, the inductor?s magnetic field collapses. this causes the current to be discharged into the output capacitor through an external schottky diode. the functional characteristics show input voltage ripple, output voltage ripple, sw voltage, and inductor current for 300ma load current. regulation is achieved by modulating the pulse width i.e., pulse-width modulation (pwm).
micrel, inc. mic2253 april 2011 8 m9999-042011-c figure 1. typical application circuit duty cycle considerations duty cycle refers to the switch on-to-off time ratio and can be calculated as follows for a boost regulator: out in v v - 1 = d however at light loads, t he inductor will completely discharge before the end of a switching cycle. the current in the inductor reaches zero before the end of the switching cycle. this is known as discontinuous conduction mode (dcm). dcm occurs when: 2 i v v i peak out in out < where ? ? ? ? ? ? ? ? < out in in out peak v v f l ) v - (v i in dcm, the duty cycle is smaller than in continuous conduction mode. in dcm the duty cycle is given by: in in out out v ) v (v i l 2 f d ? = the duty cycle required for voltage conversion should be less than the maximum duty cycl e of 90%. also, in light load conditions where the input voltage is close to the output voltage, the minimum duty cycl e can cause pulse skipping. this is due to the energy stored in the inductor causing the output to slightly overshoot the regulated output voltage. during the next cycle, the erro r amplifier detects the output as being high and skips the following pulse. this effect can be reduced by increasing the minimum load or by increasing the inductor value. increasing the inductor value also reduces the peak current. minimum duty cycle is typically 10%. over-voltage protection (ovp) the mic2253 provides a fixed 5.6v overvoltage protection. the overvoltage functionality will clamp the output voltage to a safe level in the event that a fault condition causes the output voltage to increase beyond control. to ensure the highest level of protection, the mic2253 ovp pin will shut the switch off when an overvoltage condition is detected, saving itself, the output capacitor, and downstre am devices from damage. two external resistors can be used to change the ovp from the range of 6v to 30v. be careful not to exceed the 30v rating of the switch. the ovp feature may be disabled by grounding the ovp pin. the ovp pin is connected internally to a reference voltage via a voltage divider circuit. for a 5.6v ovp setting, connect the ovp pin directly to the output voltage as shown in figure 1. to increase the ovp voltage above 5.6v, an external parallel resistor network can be configured, as shown in figure 2, with the following equation: r2 15k r2) r1 67k 1.245 v ovp + = ( figure 2. adjustable ovp circuit note: 1. the maximum value of r2 is 30k ? . soft start functionality the soft start time is dependant up on both c ss and the comp capacitor values. c comp is fixed for stable operation (typically 10nf); ther efore, if any increases in soft start are desired, this should be done using the c ss capacitor. the approximate total startup time is given by: ss ss c 85k 1ms t + =
micrel, inc. mic2253 april 2011 9 m9999-042011-c component selection inductor the mic2253 is designed to work with a 2.2h inductor. this is due to the unavoidable ?right half plane zero? effect for the continuous current boost converter topology. the frequency at which the right half plane zero occurs can be calculated as follows: 2 i l v v frhpz out out 2 in = the right half plane zero has the undesirable effect of increasing gain, while decreasing phase. this requires that the loop gain is rolled off before this has significant effect on the total loop response. this can be accomplished by either reducing inductance (increasing rhpz frequency) or increasing the output capacitor value (decreasing loop gain). output capacitor output capacitor selection is a trade-off between performance, size, and cost. increasing output capacitance will lead to an improved trans ient response, but also an increase in size and cost. x5r or x7r dielectric ceramic capacitors are recommended for designs with the mic2253. the output capacitor sets t he frequency of the dominant pole and zero in the power stage. the zero is given by: 2 esr r c 1 z f = for ceramic capacitors, the esr is very small. this puts the zero at a very high frequ ency where it can be ignored. fortunately, the mic2253 is current mode in operation which reduces the need for this output capacitor zero when compensating the feedback loop. the frequency of the pole caused by the output capacitor is given by: = 2 v c i fp out out diode selection the mic2253 requires an external diode for operation. a schottky diode is recommended for most applications due to their lower forward voltage drop and reverse recovery time. ensure the diode selected can deliver the peak inductor current and the maximum reverse voltage is rated greater than the output voltage. input capacitor a minimum 2.2f ceramic capa citor with an x5r or x7r dielectric is recommended for designing with the mic2253. increasing input capacitance will improve performance and greater noise immunity on the source. the input capacitor should be as close as possible to the inductor and the mic2253, with short traces for good noise performance. compensation the comp pin is connected to the output of the voltage error amplifier. the voltage error amplifier is a transconductance amplifier. adding a series rc-to- ground adds a zero at: 4 2 c r 2 1 fzero = the resistor should be set to approximately 600 ? . the capacitor typically ranges from 10nf to 100nf. adding an optional capacitor from comp pin-to-ground adds a pole at approximately: 3 2 c r 2 1 fpole = this capacitor typically is 100pf. generally, an rc to ground is all that is needed. the rc should be placed as close as possible to the compensation pin. the capacitor should be a ceramic with a x5r, x7r, or cog dielectric. refer to the mic2253 evaluation board document for component location. feedback resistors the feedback pin (fb) provi des the control path to the control the output. the fb pin is used to compare the output to an internal reference. output voltages are adjusted by selecting the appropriate feedback network values. the desired output voltage can be calculated as follows: ? ? ? ? ? ? ? ? + ? = 1 r r v v 2 1 ref out where v ref is equal to 1.245v.
micrel, inc. mic2253 april 2011 10 m9999-042011-c mic2253 sample schematic
micrel, inc. mic2253 april 2011 11 m9999-042011-c bill of materials item part number manufacturer description qty. c1608x5r1c225k tdk (1) capacitor, 2.2f, 16v, x5r, 0603 size grm188r61c225ke15 murata (2) capacitor, 2.2f, 16v, x5r, 0603 size c1 cl10a225k08nnn samsung (3) capacitor, 2.2f, 16v, x5r, 0603 size 1 c1608x7r1h104k/10 tdk capacitor, 0.1f, 16v, x7r, 0603 size grm188r71h104ka93 murata capacitor, 0.1f, 16v, x7r, 0603 size c2 cl10b104kb8nnn samsung capacitor, 0.1f, 16v, x7r, 0603 size 1 c1608c0g1h101j tdk capacitor, 100pf, 50v, c0g, 0603 size grm1885c1h101ja01 murata capacitor, 100pf, 50v, c0g, 0603 size cl10c101jb8nnn samsung capacitor, 100pf, 50v, c0g, 0603 size c3 06035a101at2a avx (4) capacitor, 100pf, 50v, c0g, 0603 size 1 c1608x5r1h103k tdk capacitor, 10nf, 50v, x5r, 0603 size cl10b103kb8nnn samsung capacitor, 10nf, 50v, x5r, 0603 size c4 06035c103ka12a avx capacitor, 10nf, 50v, x5r, 0603 size 1 cl21a226mpclrnc samsung capacitor, 22f, 10v, x5r, 0805 size c5 lmk212bj226mg-t taiyo yuden (5) capacitor, 22f, 10v, x5r, 0805 size 1 sk32 mcc (6) schottky diode, 3a, 20v d1 sk34 mcc schottky diode, 3a, 40v 1 ltf5022t-2r2n3r2 tdk inductor, 2.2h, 3.4a, 5.2 x 5.0 x 2.2mm rlf7030t-2r2m tdk inductor, 2,2h, 5.4a, 6.8 x 7.3 x 3.2mm l1 mos6020-222ml coilcraft (7) inductor, 2.2h, 3.56a, 6.0 x 7.1 x 2.4mm 1 r1 crcw06031002frti vishay (8) resistor, 10k ? , 1%, 1/16w, 0603 size 1 r2 crcw06036200frti vishay resistor, 620 ? , 1%, 1/16w, 0603 size 1 r4 crcw06031003frti vishay resistor, 100k ? , 1%, 1/16w, 0603 size 1 r5 crcw06033092frti vishay resistor, 30.9k ? , 1%, 1/16w, 0603 size 1 u1 mic2253-06yml micrel, inc. (9) 1mhz high efficiency boost regulator with ovp and softstart 1 notes: 1. tdk: www.tdk.com 2. murata: www.murata.com 3. samsung: www.sem.samsung.com 4. avx: www.avx.com 5. taiyo yuden: www.t-yuden.com 6. mcc: www.mccsemi.com 7. coilcraft: www.coilcraft.com 8. vishay: www.vishay.com 9. micrel, inc.: www.micrel.com
micrel, inc. mic2253 april 2011 12 m9999-042011-c recommended layout top layout bottom layout
micrel, inc. mic2253 april 2011 13 m9999-042011-c package information 12-pin 3mm x 3mm mlf ? (ml) micrel, inc. 2180 fortune drive san jose, ca 95131 usa tel +1 (408) 944-0800 fax +1 (408) 474-1000 web http://www.micrel.com micrel makes no representations or warranties with respect to t he accuracy or completeness of the information furnished in this data sheet. this information is not intended as a warranty and micrel does not assume responsibility for it s use. micrel reserves the right to change circuitry, specifications and descriptions at any time without notice. no license, whether expre ss, implied, arising by estoppel or other wise, to any intellectual property rights is granted by this document. except as provided in micrel?s terms and conditions of sale for such products, mi crel assumes no liability whatsoever, and micrel disclaims any express or implied warranty relating to the sale and/or use of micrel products including l iability or warranties relating to fitness for a particular purpose, merchantability, or infringement of an y patent, copyright or other intellectual p roperty right. micrel products are not designed or authori zed for use as components in life support app liances, devices or systems where malfu nction of a product can reasonably be expected to result in pers onal injury. life support devices or systems are devices or systems that (a) are int ended for surgical implant 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 produc ts for use in life support app liances, 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. ? 2009 micrel, incorporated.

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