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ppmic bu www.belling.com.cn BL3406B rev 1.5 belling proprietary information. unauthorized photocopy and duplicatio n prohibited 10/2009 ?2009 belling all rights reserved 1 BL3406B 1.5 mhz, 800ma synchronous buck converter features highefficiency:upto96% 1.5mhzconstantswitchingfrequency currentmodeoperationforexcellent lineandloadtransientresponse noschottkydioderequired 2.5vto5.5vinputvoltagerange 1.0v,1.2v,1.5v,1.8v,2.5vand3.3v fixed/adjustableoutputvoltage 100%dutycycleindropoutmode lowquiescentcurrent:180a overtemperatureprotection shortcircuitprotection shutdownquiescentcurrent<1a spacesaving5pinthinsot23package applications cellularandsmartphones wirelesshandsetsanddslmodems microprocessorsanddspcoresupplies pdas digitalstillandvideocameras mp3/mp4/mp5players portableinstruments gpsreceivers description the BL3406B is a constant frequency, 1.5mhz, slope compensated current mode pwm stepdown converter working under an input voltage range of 2.5v to 5.5v. this feature makes the BL3406B suitable for singlecellliionbatterypoweredapplications. the internal synchronous rectifier is desired to increase efficiency without an external schottky diode. 100% duty cycle capability extendsbatterylifeinportabledevices,while the quiescent current is 180a at no load, and drops to < 1a in shutdown. pulse skippingmodeoperationincreasesefficiency at light loads, further extending battery life. theBL3406Bisofferedinalowprofile(1mm) 5pin, thin sot23 package, and is available in an adjustable version and fixed output versionsof1.0v,1.2v,1.5v,1.8v,2.5vand 3.3v. ordering information typical application BL3406BCxx x xxx run gnd sw v in v fb BL3406B-adj 4 1 2 3 5 l1 2.2 h c3 10uf c2 22pf r2 200k r1 100k v out 1.8v v in 2.7v4.2v c1 4.7uf figure1.BL3406Badjtypicalapplicationcircuit package trn:tsot235 rn:sot235 outputvoltage 10:1.0v 12:1.2v 15:1.5v 18:1.8v 25:2.5v 33:3.3v ad:adjustable features: p:standard(default, leadfree) c:customized
ppmic bu www.belling.com.cn BL3406B rev 1.5 belling proprieta ry information. unauthorized photocopy and duplicat ion prohibited 10/2009 ?2009 belling all rights reserved 2 BL3406B 1.5 mhz, 800ma synchronous buck converter absolute maximum rating (note 1) inputsupplyvoltage 0.3vto+6v run,v fb voltages 0.3vto+v in swvoltages 0.3vto(v in +0.3v) pchannelswitchsourcecurrent(dc) 1a nchannelswitchsinkcurrent(dc) 1a peakswsinkandsourcecurrent1.4a operatingtemperaturerange 40cto+85c junctiontemperature (note2) +125c storagetemperaturerange 65cto+150c leadtemperature(soldering,10s)+300c package information adjustable output version fixed output versi ons y 9 a b c d year 2009 2010 2011 2012 2013 w 1 26 27 28 53 54 week a y z a y z thermal resistance (note 4) package ? ja ? jc tsot235 220 c/w 110c/w sot235 250 c/w 130c/w note 1: absolutemaximumratingsarethosevaluesbeyondwh ichthelifeofadevicemaybeimpaired. note 2: t j iscalculatedfromtheambienttemperaturet a andpowerdissipationp d accordingtothefollowingformula: t j =t a +(p d )x(220c/w). note 3: y:yearofwafermanufacturingw:weekofwaferma nufacturing note 4: thermalresistanceisspecifiedwithapproximately 1squareof1ozcopper. 1 2 3 5 4 sot23-5 top view run gnd sw v fb v in marking partnumber topmark temprange BL3406Badj ajyw (note3) 40cto+85c 1 2 3 5 4 sot23-5 top view run gnd sw v out v in marking partnumber topmark temprange BL3406B1.0v aayw BL3406B1.2v abyw BL3406B1.5v acyw BL3406B1.8v adyw BL3406B2.5v aeyw BL3406B3.3v afyw 40cto+85c
ppmic bu www.belling.com.cn BL3406B rev 1.5 belling proprieta ry information. unauthorized photocopy and duplicat ion prohibited 10/2009 ?2009 belling all rights reserved 3 BL3406B 1.5 mhz, 800ma synchronous buck converter pin description pin name function 1 run regulatorenablecontrolinput.driverunabove1. 5vtoturnonthepart. driverunbelow0.3vtoturnitoff.inshutdown, allfunctionsaredisabled drawing<1asupplycurrent.donotleaverunfloat ing. 2 gnd ground 3 sw powerswitchoutput.itistheswitchnodeconnect iontoexternalinductor.this pinconnectstothedrainsoftheinternalpchanne landnchannelmosfet switches. 4 v in supplyinputpin.mustbecloselydecoupledtognd ,pin2,witha2.2for greaterceramiccapacitor. 5 v fb /v out v fb (BL3406Badj):feedbackinputpin.connectfbtot hecenterpointofthe externalresistordivider.theregulatedvoltageo nthispinis0.6v. v out (BL3406B1.2/BL3406B1.5/BL3406B1.8) : outputvoltagefeedbackpin. aninternalresistivedividerdividestheoutputvo ltagedownforcomparisontothe internalreferencevoltage. block diagram
ppmic bu www.belling.com.cn BL3406B rev 1.5 belling proprietary information. unauthorized photocopy and duplicatio n prohibited 10/2009 ?2009 belling all rights reserved 4 BL3406B 1.5 mhz, 800ma synchronous buck converter electrical characteristics (note 5) (v in =v run =3.6v,ta=25c,unlessotherwisenoted.) parameter conditions min typ max unit inputvoltagerange 2.5 5.5 v inputdcsupplycurrent activemode shutdownmode v fb =0.5vorv out =90% v fb =0v,v in =4.2v 180 0.1 300 1.0 a a t a =+25c 0.5880 0.6000 0.6120 v t a =0ct a 85c 0.5865 0.6000 0.6135 v regulatedfeedback voltage t a =40ct a 85c 0.5850 0.6000 0.6150 v v fb inputbiascurrent v fb =0.65v 30 na referencevoltageline regulation v in =2.5vto5.5v 0.04 0.4 %/v BL3406B1.2,40ct a 85c 1.164 1.200 1.236 v regulatedoutputvoltage BL3406B1.8,40ct a 85c 1.746 1.800 1.854 v ?v ovl =v ovl Cv fb ,adjustableversion 20 50 80 mv outputovervoltage lockout ?v ovl =v ovl Cv out ,fixedversion 2.5 7.8 13 % outputvoltageline regulation v in =2.5vto5.5v 0.04 0.40 % outputvoltageload regulation 0.5 % peakinductorcurrent v in =3v,v fb =0.5vorv out =90% dutycycle<35% 1.2 a oscillatorfrequency v fb =0.6vorv out =100% 1.2 1.5 1.8 mhz r ds(on) ofpchmosfet i sw =300ma 0.40 0.50 r ds(on) ofnchmosfet i sw =300ma 0.35 0.45 swleakagecurrent v run =0v,v sw =0vor5v,v in =5v 0.01 1 a runthreshold 40ct a 85c 0.3 1.1 1.30 v runleakagecurrent 0.01 1 a note 5: 100%productiontestat+25c.specificationsover thetemperaturerangeareguaranteedbydesignand characterization.
ppmic bu www.belling.com.cn BL3406B rev 1.5 belling proprietary information. unauthorized photocopy and duplicatio n prohibited 10/2009 ?2009 belling all rights reserved 5 BL3406B 1.5 mhz, 800ma synchronous buck converter typical performance characteristics (testfigure1aboveunlessotherwisespecified) 0.1 1 10 100 1000 20 30 40 50 60 70 80 90 efficiency(%) outputcurrent(ma) vin=2.7v vin=3.6v vin=4.2v v out =1.8v l=2.2uh efficiency vs. output current 0 200 400 600 800 1000 1200 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 outputvoltage(v) loadcurrent(ma) output voltage vs. load current v in =3.6v t a =25 c 50 25 0 25 50 75 100 125 0.602 0.603 0.604 0.605 0.606 referencevoltage(v) temperature ( c ) v in =3.6v reference voltage vs. temperature 2.7 3.0 3.3 3.6 3.9 4.2 4.5 4.8 5.1 5.4 5.7 1.780 1.785 1.790 1.795 1.800 1.805 1.810 1.815 1.820 v out (v) v in (v) i load =10ma i load =100ma i load =600ma output voltage vs. input voltage supply current vs. supply voltage start_up from shutdown 2 3 4 5 6 195 200 205 210 215 220 225 230 235 240 245 dynamicsupplycurrent(ua) supplyvoltage(v) v out =1.8v i load =0a t a =25 c
ppmic bu www.belling.com.cn BL3406B rev 1.5 belling proprietary information. unauthorized photocopy and duplicatio n prohibited 10/2009 ?2009 belling all rights reserved 6 BL3406B 1.5 mhz, 800ma synchronous buck converter load step load step load step load step pulse skipping mode output short
ppmic bu www.belling.com.cn BL3406B rev 1.5 belling proprieta ry information. unauthorized photocopy and duplicat ion prohibited 10/2009 ?2009 belling all rights reserved 7 BL3406B 1.5 mhz, 800ma synchronous buck converter operation the BL3406B uses a constant frequency, current mode stepdown architecture. both the main switch (pchannel mosfet) and the synchronous rectifier (nchannel mosfet) are integrated internally. this stepdown dcdc converter can supply 800ma output current over a wide input voltage range from 2.5v to 5.5v. the over voltage comparator ovdet guards against transient overshoots >7.8% by turning the main switch off and keeping it off until the faultisremoved. current mode pwm control slope compensated current mode pwm control provides stable switching and cycle bycycle current limit for excellent load and line responses. during normal operation, the internalmainswitchisturnedonforacertain time to ramp the inductor current at each rising edge of the internal oscillator, and turned off when the peak inductor current reachesthecontrolledvalue.whenthemain switchisoff,thesynchronousrectifierwillbe turnedonimmediatelyandstayonuntileither the inductor current starts to reverse, as indicatedbythecurrentreversalcomparator, i rcmp ,orthebeginningofthenextclockcycle. pulse skipping mode operation at very light loads, the BL3406B will automatically enter pulse skipping mode to increase efficiency, further extending battery life.inthismode,thecontrolloopskipspwm pulseswhilemaintainingoutputinregulation, and the switching frequency depends on the load condition. this is a kind of pfm mode operation. dropout operation whentheinputvoltagedecreasestowardthe valueoftheoutputvoltage,theBL3406Bwill keep the main switch on for more than one switching cycle and increases the duty cycle (note 6) until it reaches 100%. the output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. at low input supply voltage, the r ds(on) ofthepchannelmosfetincreases, andtheefficiencyoftheconverterdecreases. cautionmustbeexercisedtoensuretheheat dissipated not to exceed the maximum junctiontemperatureoftheic. note 6 66 6 : thedutycycledofastepdownconverteris definedas: % 100 % 100 ? = in out osc on v v f t d wheret on isthemainswitchontime,andf osc istheoscillatorfrequency(1.5mhz). short circuit protection the BL3406B has short circuit protection. when output is shorted to ground, the oscillatorfrequencyisreducedtopreventthe inductor current from increasing beyond the pfet current limit. the pfet current limit is alsoreducedtolowertheshortcircuitcurrent. the frequency and current limit will return to the normal values once the short circuit condition is removed and the feedback voltagereaches0.6v. maximum load current the BL3406B will operate with input supply voltage as low as 2.5v, however the maximum load current decreases at lower input voltage due to large ir drop on the mainswitchandsynchronousrectifier.
ppmic bu www.belling.com.cn BL3406B rev 1.5 belling proprietary information. unauthorized photocopy and duplicatio n prohibited 10/2009 ?2009 belling all rights reserved 8 BL3406B 1.5 mhz, 800ma synchronous buck converter application information figure2belowshowsthebasicapplication circuitwithBL3406Bfixedoutputversions. run gnd sw v in v out BL3406B-18 4 1 2 3 5 l1 2.2 h c2 10uf v out 1.8v v in 2.7v4.2v c1 4.7uf figure2.basicapplicationcircuit withfixedoutputversions setting the output voltage figure 1 above shows the basic application circuit with BL3406B adjustable output version.the external resistor sets the output voltageaccordingtothefollowingequation: ) 1 2 1( 6.0 r r v v out + = table 1 resistor selection vs. output voltage setting vout r1 r2 1.0v 180 k (1%) 120 k (1%) 1.2v 180 k (1%) 180 k (1%) 1.5v 180 k (1%) 270 k (1%) 1.8v 180 k (1%) 360 k (1%) 2.5v 158 k (1%) 499 k (1%) 3.3v 180 k (1%) 810 k (1%) inductor selection the output inductor is selected to limit the ripple current to some predetermined value, typically 20%~40% of the full load current at the maximum input voltage. in continuous mode,theripplecurrentisdeterminedby: ) 1( 1 in out out l v v v l f i - = d a reasonable starting point for setting ripple current is ?i l =320ma (40% of 800ma). for output voltages above 2.0v, when efficiency at light load condition is important, the minimum recommended inductor is 2.2h. for optimum voltagepositioning load transients,chooseaninductorwithdcseries resistance below 150m. for higher efficiency at heavy loads (above 200ma), or minimal load regulation (but some transient overshoot), the resistance should be kept below 100m. the dc current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation. thus, a 1120maratedinductorshouldbeenoughfor mostapplications(800ma+320ma). input capacitor selection theinputcapacitorreducesthesurgecurrent drawn from the input and switching noise from the device. the input capacitor impedance at the switching frequency shall be less than input source impedance to prevent high frequency switching current passingtotheinput.incontinuousmode,the sourcecurrentofthemainswitchisasquare waveofdutycyclev out /v in .topreventlarge voltagetransients,alowesrinputcapacitor sizedforthemaximumrmscurrentmustbe used.themaximumrmscapacitorcurrentis givenby: in out in out omax rms v v v v i i 5.0 )] ( [ - ? this formula has a maximum at v in =2v out , where i rms = i out /2. this simple worstcase condition is commonly used for design because even significant deviations do not offer much relief. ceramic capacitors with x5r or x7r dielectrics are recommended duetotheirlowesrandhighripplecurrent. output capacitor selection theoutputcapacitorisrequiredtokeepthe outputvoltageripplesmallandtoensure regulationloopstability.theoutputcapacitor musthavelowimpedanceattheswitching
ppmic bu www.belling.com.cn BL3406B rev 1.5 belling proprietary information. unauthorized photocopy and duplicatio n prohibited 10/2009 ?2009 belling all rights reserved 9 BL3406B 1.5 mhz, 800ma synchronous buck converter frequency.ceramiccapacitorswithx5ror x7rdielectricsarerecommendeddueto theirlowesrandhighripplecurrent.the outputripplev out isdeterminedby: ? ?? ? ? ?? ? + - d 2 8 1 ) ( c f esr l f v v v v v osc osc in out in out out layout considerations whenlayingouttheprintedcircuitboard,the following checklist should be used to ensure proper operation of the BL3406B. these items are also illustrated graphically in figures 5 and 6. check the following in your layout: 1. the power traces, consisting of the gnd trace, the sw trace and the v in trace shouldbekeptshort,directandwide. 2. does the v fb pin connect directly to the feedback resistors? the resistive divider r1/r2mustbeconnectedbetweenthe(+) plateofcoutandground. 3.doesthe(+)plateofc in connecttov in as closely as possible? this capacitor provides the ac current to the internal powermosfets. 4. keep the switching node, sw, away from thesensitivev fb node. 5. keep the () plates of c in and c out as closeaspossible. figure3.BL3406Badjlayoutcircuit figure4.BL3406B1.8layoutcircuit figure5.BL3406Badjsuggestedlayout figure6.BL3406B1.8suggestedlayout run gnd sw v in v fb BL3406B-adj 4 1 2 3 5 l1 2.2 h c3 10uf c2 22pf r2 200k r1 100k v out 1.8v v in 2.7v4.2v c1 4.7uf run gnd sw v in v out BL3406B-18 4 1 2 3 5 l1 2.2 h c2 10uf v out 1.8v v in 2.7v4.2v c1 4.7uf
ppmic bu www.belling.com.cn BL3406B rev 1.5 belling proprieta ry information. unauthorized photocopy and duplicat ion prohibited 10/2009 ?2009 belling all rights reserved 10 BL3406B 1.5 mhz, 800ma synchronous buck converter package description dimensions in millimeters dimensions in inches symbol min max min max a 0.889 1.295 0.035 0.051 a1 0.000 0.152 0.000 0.006 b 1.397 1.803 0.055 0.071 b 0.356 0.559 0.014 0.022 c 2.591 2.997 0.102 0.118 d 2.692 3.099 0.106 0.122 e 0.838 1.041 0.033 0.041 h 0.080 0.254 0.003 0.010 l 0.300 0.610 0.012 0.024 sot235surfacemountpackage
ppmic bu www.belling.com.cn BL3406B rev 1.5 belling proprietary information. unauthorized photocopy and duplicatio n prohibited 10/2009 ?2009 belling all rights reserved 11 BL3406B 1.5 mhz, 800ma synchronous buck converter tsot235surfacemountpackage

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