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1/17 www.rohm.com 2010.06 - rev. a ? 2010 rohm co., ltd. all rights reserved. single-chip type with built-in fet switching regulators output 2a more high-efficiency step-down switching regulator with built-in power mos fet bd91361muv description rohm?s high efficiency step-down swit ching regulator bd91361muv is a power supply designed to produce a low voltage including 0.8 volts from 5.5/3.3 volts power supply line. offers high efficiency with our original pulse skip control technolog y and synchronous rectifier. employs a current mode control system to provide faster transient response to sudden change in load. features 1) offers fast transient response with current mode pwm control system. 2) offers highly efficiency for all load range with synchronous rectifier (nch/nch fet) and sllm tm (simple light load mode) 3) incorporates soft-start function. 4) incorporates thermal protection and ulvo functions. 5) incorporates short-current protec tion circuit with time delay function. 6) incorporates shutdown function icc=0a(typ.) 7) employs small surface mount package: vqfn020v4040 applications power supply for lsi including dsp, micro computer and asic absolute maximum rating (ta=25 ) parameter symbol ratings unit v cc voltage v cc -0.3 +7 * 1 v pv cc voltage pv cc -0.3 +7 * 1 v bst voltage v bst -0.3 +13 v bst_sw voltage v bst - sw -0.3 +7 v en voltage v en -0.3 +7 v sw,ith voltage v sw , v ith -0.3 +7 v power dissipation 1 pd1 0.34 * 2 w power dissipation 2 pd2 0.70 * 3 w power dissipation 3 pd3 2.21 * 4 w power dissipation 4 pd4 3.56 * 5 w operating temperature range topr -40 +105 storage temperature range tstg -55 +150 maximum junction temperature tj +150 *1 pd should not be exceeded. *2 ic only *3 1-layer. mounted on a 74.2mm 74.2mm 1.6mm glass-epoxy board, occupied area by copper foil : 10.29mm 2 *4 4-layer. mounted on a 74.2mm 74.2mm 1.6mm glass-epoxy board, 1st and 4th copper foil area : 10.29mm 2 , 2nd and 3rd copper foil area : 5505mm 2 *5 4-layer. mounted on a 74.2mm 74.2mm 1.6mm glass-epoxy board, occupied area by copper foil : 5505mm 2 , in each layers no.10027eat44
technical note 2/17 www.rohm.com 2010.06 - rev. a ? 2010 rohm co., ltd. all rights reserved. bd91361muv
technical note 3/17 www.rohm.com 2010.06 - rev. a ? 2010 rohm co., ltd. all rights reserved. bd91361muv 2.10.1 c0.2 0.5 1.0 15 6 10 11 15 16 20 4.0 0.1 4.0 0.1 2.10.1 0.40.1 0.25 +0.05 -0.04 0.02 +0.03 -0.02 1.0max. (0.22) 0.08 s s lot no. d 9 1 3 6 1 output pgnd gnd gm amp r s q osc + v cc vcc clk slope en current comp soft start current sense/ protect + driver logic + ith r ith c ith pvcc sw pv cc bst v cc input adj vref uvlo tsd scp selector r1 r2 vid<0> vid<1>
technical note 4/17 www.rohm.com 2010.06 - rev. a ? 2010 rohm co., ltd. all rights reserved. bd91361muv characteristic curves (reference data) 0.0 0.4 0.8 1.2 1.6 2.0 012345 input voltage:v cc [v] output voltage:vout[v] 0.0 0.4 0.8 1.2 1.6 2.0 0246810 output current:i out [a] output voltage:vout[v] v out =1.2v v out =1.2v ta = 2 5 fig.10 ta-v en fig.11 ta-i cc fig.9ta-r onn ,r onp ta = 2 5 io=3a 0.0 0.4 0.8 1.2 1.6 2.0 01 23 45 en voltage:ven[v] output voltage:vout[v] v cc =5v ta = 2 5 io=0a v out =1.2v 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 -40 -20 0 20 40 60 80 100 temperature:ta[ ] en voltage:ven[v] 0 50 100 150 200 250 300 350 400 -40-20 0 20406080100 temperature:ta[ ] circuit current:icc[ a] v cc =5v v cc =5v 1.15 1.16 1.17 1.18 1.19 1.20 1.21 1.22 1.23 1.24 1.25 -40-20 0 20406080100 temperature:ta[ ] output voltage:vout[v] 0 200 400 600 800 1000 1200 -40-20 0 20406080100 temperature:ta[ ] frequency:fosc[khz] fig.8 ta-fosc 30 40 50 60 70 80 90 100 10 100 1000 10000 output current:i out [ma] efficiency: [%] fig.7 efficiency fig.3 vcc-vou t fig.5 i out -v out v cc =5v io=0a v out =1.2v v cc =5v ta = 2 5 v cc =5v fig. 6 ta-v out fig.4 v en -v out vout=1.2 v cc = 5.5v v cc =2.7v 40 50 60 70 80 -40 -20 0 20 40 60 80 100 temperature:ta[ ] on resistance:r on [ ] v cc =3.3v high side low side
technical note 5/17 www.rohm.com 2010.06 - rev. a ? 2010 rohm co., ltd. all rights reserved. bd91361muv sw v out vcc=5 v ta = 2 5 sllm tm control vout=1.2v fig.12 power supply voltage- operating frequency v out =1.2v vcc=5 v ta = 2 5 io=0 a v out v cc =pv cc =en fig.13 soft start waveform fig.14 sw waveform io=0ma v out i out v out i out vcc=5 v ta = 2 5 v out =1.2v fig. 16 transient response io=1a4a(20s) vcc=5v t a =2 5 v out =1.2v fig.17 transient response io=4a1a(20s) sw fig.15 sw waveform io=4a vcc=5v ta = 2 5 pwm control v out =1.2v v out =1.2v v out =1.2v fig.18 change response fig.19 change response vid[1:0]=(0,0) (1,1) vid[1:0]=(1,1) (0,0) 1.2v 1.44v 1.44v 1.2v 0.7 0.8 0.9 1 1.1 2.7 3.4 4.1 4.8 5.5 input voltage:v cc [v] frequency:f osc [mhz] ta = 2 5
technical note 6/17 www.rohm.com 2010.06 - rev. a ? 2010 rohm co., ltd. all rights reserved. bd91361muv information on advantages advantage 1 : offers fast transient response with current mode control system. voltage drop due to sudden change in load was reduced by about 50%. fig.20 comparison of transient response advantage 2 : offers high efficiency for all load range. ? for lighter load: utilizes the current mode contro l mode called sllm for lighter load, which r educes various dissipation such as switching dissipation (p sw ), gate charge/discharge dissipation, esr dissipation of output capacitor (p esr ) and on-resistance dissipation (p ron ) that may otherwise cause degradation in efficiency for lighter load. achieves efficiency improvement for lighter load. ? for heavier load: utilizes the synchronous rectifying mode and the low on-re sistance mos fets incorporated as power transistor. on resistance of high side mos fet : 82m (typ.) on resistance of low side mos fet : 70m (typ.) achieves efficiency improvement for heavier load. offers high efficiency for all load rang e with the improvements mentioned above. advantage 3 : ? supplied in smaller package due to small-sized power mos fet incorporated. reduces a mounting area required. fig.22 example application fig.21 efficiency ? output capacitor co required for current mode control: 22f ceramic capacitor ? inductance l required for the operating frequency of 1 mhz: 2.2h inductor ? incorporates fet + boot strap diode 0.001 0.01 0.1 1 0 50 100 pwm sllm tm inprovement by sllm system improvement by synchronous rectifier efficiency [%] output current io[a] conventional product (load response i o =1a 3a) bd91361muv (load response i o =1a 3a) v out i out 145mv v out i out 62mv output pgnd gnd gm amp r s q + v cc vcc clk slope en current comp soft start current sense/ protect + driver logic + ith r ith c ith pvcc sw pvcc bst vcc input adj vid<0> uvlo scp r1 r2 tsd vid<1> selector vref 15mm 20mm r 2 c ith c f co l r 1 r ith rf c bst c in
technical note 7/17 www.rohm.com 2010.06 - rev. a ? 2010 rohm co., ltd. all rights reserved. bd91361muv operation bd91361muv is a synchronous rectifying st ep-down switching regulator that achi eves faster transient response by employing current mode pwm control system. it utilizes switch ing operation in pwm (pulse width modulation) mode for heavier load, while it utilizes sllm (simple light load mode) operation for lighter load to improve efficiency. synchronous rectifier it does not require the power to be dissipated by a rectifier externally connected to a conventional dc/dc converter ic, and its p.n junction shoot-through protection circuit limits the shoot-through current during op eration, by which the power dissipation of the set is reduced. current mode pwm control synthesizes a pwm control signal with a inductor current feedback loop added to the voltage feedback. ? pwm (pulse width modulation) control the oscillation frequency for pwm is 1 mhz. set signal form osc turns on a highside mos fet (while a lowside mos fet is turned off), and an inductor current i l increases. the current comparator (current comp) receives two signals, a current feedback control sign al (sense: voltage converted from i l ) and a voltage feedback control signal (fb), and issues a reset signal if both input signals are identical to each other, and turns off the highside mos fet (while a lowside mos fet is turned on) for the rest of the fixed period. the pwm control repeat this operation. ?sllm tm (simple light load mode) control when the control mode is shifted from pwm for heavier load to the one for lighter load or vise versa, the switching pulse is designed to turn off with the device held operated in norm al pwm control loop, which allows linear operation without voltage drop or deterioration in transient response during the mode switching from light load to heavy load or vise versa. although the pwm control loop continues to operate with a set signal from osc and a reset signal from current comp, it is so designed that the reset si gnal is held issued if shifted to the light load mode, with which the switching is tuned off and the switching pulses are th inned out under control. activating t he switching intermittently reduces the switching dissipation and improves the efficiency. fig.23 diagram of current mode pwm control fig.24 pwm switching timing chart fig.25 sllm tm switching timing chart osc level shift driver logic rq s i l sw ith current comp gm amp. set reset fb load sense v out v out curren t comp set reset sw v out pvcc gnd gnd gnd i l (ave) v out (ave) sense fb curren t comp set reset sw v out pvcc gnd gnd gnd 0a v out (ave) sense fb i l not switching i l
technical note 8/17 www.rohm.com 2010.06 - rev. a ? 2010 rohm co., ltd. all rights reserved. bd91361muv description of operations ? soft-start function en terminal shifted to ?high? activates a soft-starter to gradually establish the output voltage with the current limited durin g startup, by which it is possible to prevent an ov ershoot of output voltage and an inrush current. ? shutdown function with en terminal shifted to ?low?, the device turns to standby mode, and all the function blocks including reference voltage circuit, internal oscillator and drivers are turned to off. circuit current during standby is 0f (typ.). ? uvlo function detects whether the input voltage sufficient to secure the output voltage of this ic is supplied. and the hysteresis width of 50mv (typ.) is provided to prevent output chattering. fig.26 soft start, shutdown, uvlo timing chart ? short-current protection circuit with time delay function turns off the output to protect the ic fr om breakdown when the incorporated current limiter is activated continuously for the fixed time(t latch ) or more. the output thus held tuned off may be recovered by restarting en or by re-unlocking uvlo. fig.27 short-current protection circuit with time delay timing chart hysteresis 50mv ts s ts s ts s soft start standby mode operating mode standby mode operating mode standby mode operating mode standby mode uvlo en uvlo uvlo v cc en v out 1/2v out 1msec output voltage off latch output current in non-control output current in control by limit value (with fall of the output voltage, limit value goes down) en timer latch en standby mode operated mode standby mode operated mode en v out limi t i l until output voltage goes up the half of vo or over, timer latch is not operated. (no timer latch, only limit to the output current)
technical note 9/17 www.rohm.com 2010.06 - rev. a ? 2010 rohm co., ltd. all rights reserved. bd91361muv switching regulator efficiency efficiency ? may be expressed by the equation shown below: efficiency may be improved by reducing the swit ching regulator power dissipation factors p d as follows: dissipation factors: 1) on resistance dissipation of inductor and fet : pd(i 2 r) 2) gate charge/discharge dissipation : pd(gate) 3) switching dissipation : pd(sw) 4) esr dissipation of capacitor : pd(esr) 5) operating current dissipation of ic : pd(ic) 1)pd(i 2 r)=i out 2 (r coil +r on ) (r coil [ ] : dc resistance of inductor, r on [ ] : on resistance of fet, i out [a] : output current.) 2)pd(gate)=cgs f v (cgs[f] : gate capacitance of fet, f[h] : switching frequency, v[v] : gate driving voltage of fet) 4)pd(esr)=i rms 2 esr (i rms [a] : ripple current of capacitor, esr[ ] : equivalent series resistance.) 5)pd(ic)=vin i cc (i cc [a] : circuit current.) = v out i out vin iin 100[%]= p out pin 100[%]= p out p out +p d 100[%] vin 2 c rss i out f i drive 3)pd(sw)= (c rss [f]:reverse transfer capacitance of fet, i drive [a]:peak current of gate.)
technical note 10/17 www.rohm.com 2010.06 - rev. a ? 2010 rohm co., ltd. all rights reserved. bd91361muv about setting the output voltage output voltage shifts step by step as often as bit setting to control the overshoot/undershoot that happen when changing the setting value of output voltage. from the bit switching until output voltage reach to setting value, 8 steps(max) delay will occur. ) switching 2 bit synchronously ) switching the bit during counting ) switching 2 bit with the time lag fig.28 timing chart of setting the output voltage it is possible to set output voltage, shown the diagram 1 below, by setting vid<0> <1> 0 or 1. vid<1:0> terminal is set to vid<1:0>=(0,0) originally by the pull down resistor with high impedance inside ic. by pulling up/ pulling down about 10k , the original value is changeable optionally. diagram 1. table of output voltage setting vid<1> vid<0> v out 0 0 v out 0 1 0.9*v out 1 0 1.1*v out 1 1 1.2*v out *after 10s(max) from the bit change, v out change starts. *requiring time for one step (10% shift of v out ) of v out is 10s(max). *from the bit switching until output voltage reach to setting value, t vid (max)=0.04ms delay will occur. vout vid<2:0> (0,1) (1,1) 0.96 v 0.72v tvid (max)=0.04ms vout count stop about 10s from switching the last bit vid<1> vid<0> <1> vout <0> count stop about 10s from bit switching vout count stop about 10s from bit switching vid<1> vid<0> 5 s ( max )
technical note 11/17 www.rohm.com 2010.06 - rev. a ? 2010 rohm co., ltd. all rights reserved. bd91361muv consideration on permissible dissipation and heat generation as this ic functions with high efficiency without significant heat generation in most applications, no special consideration is needed on permissible dissipation or heat generation. in case of extreme conditions, however, including lower input voltage, higher output voltage, heavier load, and/or higher temperature, the permissible dissipation and/or heat generation must be carefully considered. for dissipation, only conduction losses due to dc resistance of inductor and on resistance of fet are considered. because the conduction losses are considered to play the leading role among other dissipation mentioned above including gate charge/discharge dissipation and switching dissipation. if v cc =3.3v, v out =1.8v, r onh =60m , r onl =55m i out =4a, for example, d=v out /v cc =1.8/3.3=0.545 r on =0.545 0.06+(1-0.545) 0.055 =0.0327+0.0250 =0.0577[ ] p=4 2 0.0577=0.2309[w] as r onh is greater than r onl in this ic, the dissipation increases as the on duty becomes greater. with the consideration on the dissipation as above, thermal des ign must be carried out with sufficient margin allowed. fig.29 thermal derating curve (vqfn020v4040) p=i out 2 r on r on =d r onp +(1-d)r onn d : on duty (=v out /v cc ) r onh : on resistance of highside mos fet r onl : on resistance of lowside mos fet i out : output current 0 1 2 3 4 0 25 50 75 100 125 150 ambient temperature:ta [] power dissipation:pd [w] 105 4 layers (copper foil area : 5505mm 2 ) copper foil in each layers. j-a=35.1 /w 4 layers (1 st and 4 th copper foil area : 10.29m 2 ) (2 nd and 3 rd copper foil area: 5505m 2 ) j-a=56.6 /w 1 layer (copper foil area : 10.29m 2 ) j-a=178.6 /w ic only. j-a=367.6 /w 2.21w 3.56w 0.70w 0.34w
technical note 12/17 www.rohm.com 2010.06 - rev. a ? 2010 rohm co., ltd. all rights reserved. bd91361muv selection of components externally connected 1. selection of inductor (l) current exceeding the current rating of the inductor results in magnetic saturation of the inductor, which decreases efficiency. the inductor must be selected allowing suffic ient margin with which the peak current may not exceed its current rating. if v cc =5.0v, v out =1.2v, f=1mhz, i l =0.2 3a=0.6a, for example,(bd91361muv) select the inductor of low resistance component (such as dcr and acr) to minimize dissipation in the inductor for better efficiency. 2. selection of output capacitor (c o ) 3. selection of input capacitor (cin) a low esr 22f/10v ceramic capacitor is recommended to reduc e esr dissipation of input ca pacitor for better efficiency. the inductance significantly depends on output ripple current. a s seen in the equation (1), the ripple current decreases as the inductor and/or swit ching frequency increases. i l = (v cc -v out )v out l v cc f [ a ] ??? ( 1 ) appropriate ripple current at output should be 20% more or less of the maximum output current. i l =0.2 i out max. [a] ???(2) l= (v cc -v out )v out i l v cc f [ h ] ??? ( 3 ) (i l : output ripple current, and f: switching frequency) output capacitor should be selected with the consideration on the stability region and the equivalent series resistance required to smooth ripple voltage. output ripple voltage is determined by the equation (4) : v out = i l esr [v]??? (4) (i l : output ripple current, esr: equivalent series resistance of output capacitor) rating of the capacitor should be determined allowing sufficient margin against output voltage. a 22f to 100f ceramic capacitor is recommended. less esr allows reduction in output ripple voltage. fig.31 output capacitor i l v out fig.30 output ripple current i l v cc il l co v cc l co v out esr fig.32 input capacitor v out v cc l co cin input capacitor to select must be a low esr capacitor of the capacitance sufficient to cope with high ripple current to prevent high transient voltage. the ripple current irms is given by the equation (5): i rms =i out v out ( v cc -v out ) v cc [a] ??? ( 5 ) when vcc=2 v out , i rms = i out 2 < worst case > i rms(max.) i rms =2 1.8 ( 3.3-1.8 ) 3.3 =1.49 [ a rms ] if v cc =3.3v, v out =1.8v, and i outmax.= 3a, (bd91361muv) ( 5-1.2 ) 1.2 0.6 5 1m l= =1.52 2.0[h]
technical note 13/17 www.rohm.com 2010.06 - rev. a ? 2010 rohm co., ltd. all rights reserved. bd91361muv 4. determination of rith, cith that works as a phase compensator as the current mode control is designed to limit a inductor current, a pole (phase lag) appears in the low frequency area due to a cr filter consisting of a output capacitor and a load resistance, while a zero (phase lead) appears in the high frequency area due to the output capacitor and its esr. so, the phases are easily compensated by adding a zero to the power amplifier output with c and r as described bel ow to cancel a pole at the power amplifier. fig.35 typical application stable feedback loop may be achieved by canceling the pol e fp (min.) produced by the output capacitor and the load resistance with cr zero correction by the error amplifier. fz (amp.) = fp (min.) 2 r ith c ith 1 = 2 r omax. c o 1 gain [db] phase [deg] fig.33 open loop gain characteristics a 0 0 -90 a 0 0 -90 fz(amp.) fig.34 error amp phase compensation characteristics fp(min.) fp(max.) fz(esr) i out min. i out max. gain [db] phase [deg] fp= 2 r o c o 1 fz (esr) = 2 e sr c o 1 pole at power amplifie r when the output current decreases, the load resistance ro increases and the pole frequency lowers. fp (min.) = 2 r omax. c o 1 [hz] with lighter load fp (max.) = 2 r omin. c o 1 [hz] with heavier load zero at power amplifie r fz (amp.) = 2 r ith c ith 1 increasing capacitance of the output capacitor lowers the pole frequency while the zero frequency does not change. (this is because when the capacitance is doubled, the capacitor esr reduces to half.) gnd,pgnd sw pv cc en a dj ith v cc v out cin r ith c ith l esr c o r o v out c bst v cc c f r f vid<1> vid<0> v cc v cc r2 r1
technical note 14/17 www.rohm.com 2010.06 - rev. a ? 2010 rohm co., ltd. all rights reserved. bd91361muv 5. determination of output voltage the output voltage v out is determined by the equation (6): v out =(r2/r1+1) v adj ???(6) v adj : voltage at adj terminal (0.8v typ.) with r1 and r2 adjusted, the output vo ltage may be determined as required. adjustable output voltage range : 0.8v 3.3v fig.36 determination of output voltage use 1 k ? 100 k ? resistor for r1. if a resistor of the resistance higher than 100 k ? is used, check the assembled set carefully for ripple voltage etc. bd91361muv cautions on pc board layout fig.38 layout diagram lay out the input ceramic capacitor cin closer to the pi ns pvcc and pgnd, and the output capacitor co closer to the pin pgnd. lay out cith and rith between the pi ns ith and gnd as neat as possible with least necessary wiring. vqfn020v4040 (bd91361muv) has thermal pad on the reverse of the package. the package thermal performance may be enhanced by bonding t he pad to gnd plane which take a large area of pcb. sw 6 1 a dj l co r2 r1 output fig.37 minimum input voltage in each output voltage the lower limit of input voltag e depends on the output voltage. basically, it is recommended to use in the condition : vccmin = vout+1.2v. fig.37. shows the necessary output current value at the lower limit of input voltage. (dcr of inductor : 20m ) this data is the characteristic va lue, so it? doesn?t guarantee the operation range, vo=2.5v vo=2.0v vo=1.8v 2.7 2.9 3.1 3.3 3.5 3.7 0 1 2 3 input voltage : vcc[v] output current : iout[a]
technical note 15/17 www.rohm.com 2010.06 - rev. a ? 2010 rohm co., ltd. all rights reserved. bd91361muv recommended components lists on above application symbol part value manufacturer series l coil 2.0uh sumida cdr6d28mnnp-2r0nc c in ceramic capacitor 22uf murata grm32eb11a226ke20 c o ceramic capacitor 22uf murata grm31cb30j226ke18 c ith ceramic capacitor v out =1.2v 1000pf murata crm18 series r ith resistance 6.8k rohm mcr03 series cf ceramic capacitor 1000 pf murata grm18 series rf resistance 10 rohm mcr03 series c bst ceramic capacitor 0.1uf murata grm18 series the parts list presented above is an example of recommend ed parts. although the parts are sound, actual circuit characteristics should be checked on your application carefully before use. be sure to allow sufficient margins to accommodate variations between external devices and this ic when employing the depicted circuit with other circuit constants modified. both static and transient characteristics should be considered in establishing these margins. when switching noise is substantial and may impact the system, a low pass filter should be inserted between the vcc and pvcc pins, and a schottky barrier diode or snubber established between the sw and pgnd pins. i/o equivalence circuit fig.39 i/o equivalence circuit ? en pin en ? sw pin pv cc sw pv cc pv cc ? ith pin ith v cc ? adj pin a dj pv cc bst ? bst pin pv cc sw ? vid pin ( vid<0>, vid<1> are the same composition vid
technical note 16/17 www.rohm.com 2010.06 - rev. a ? 2010 rohm co., ltd. all rights reserved. bd91361muv notes for use 1. absolute ma ximum ratings while utmost care is taken to quality control of this pr oduct, any application that may exceed some of the absolute maximum ratings including the voltage applied and the operatin g temperature range may result in breakage. if broken, short-mode or open-mode may not be identified. so if it is expected to encounter with special mode that may exceed the absolute maximum ratings, it is requested to take necessary sa fety measures physically including insertion of fuses. 2. electrical potential at gnd gnd must be designed to have the lowest elec trical potential in any operating conditions. 3. short-circuiting between terminals, and mismounting when mounting to pc board, care must be taken to avoid mistak e in its orientation and alignment. failure to do so may result in ic breakdown. short-circuiting due to foreign matters entered between output te rminals, or between output and power supply or gnd may also cause breakdown. 4. thermal shutdown protection circuit thermal shutdown protection circuit is the circuit designed to isolate the ic from thermal runaway, and not intended to protect and guarantee the ic. so, the ic the thermal shutdown protection circui t of which is once activated should not be used thereafter for any operation originally intended. 5. inspection with the ic set to a pc board if a capacitor must be connected to the pin of lower impedanc e during inspection with the ic set to a pc board, the capacitor must be discharged after each process to avoid stre ss to the ic. for electrostatic protection, provide proper grounding to assembling processes with special care taken in handling and storage. when connecting to jigs in the inspection process, be sure to turn off the power supply before it is connected and removed. 6. input to ic terminals this is a monolithic ic with p + isolation between p-substrate and each element as illustrated below. this p-layer and the n-layer of each element form a p-n junction, and various parasitic elements are formed. if a resistor is joined to a transistor terminal as shown in fig 40. p-n junction works as a parasitic diode if t he following relationship is satisfied; gnd>terminal a (at resistor side), or gnd>terminal b (at transistor side); and if gnd>terminal b (at npn transistor side), a parasitic npn transistor is activated by n-layer of ot her element adjacent to the above-mentioned parasitic diode. the structure of the ic inevitably forms parasitic elements, the activation of which may cause interference among circuits, and/or malfunctions contributing to breakdow n. it is therefore requested to take care not to use the device in such manner that the voltage lower than g nd (at p-substrate) may be applied to t he input terminal, which may result in activation of parasitic elements. fig.40 simplified structure of monorisic ic 7. ground wiring pattern if small-signal gnd and large-current gnd are provided, it will be recommended to separate the large-current gnd pattern from the small-signal gnd pattern and establish a si ngle ground at the reference poi nt of the set pcb so that resistance to the wiring pattern and voltage fluctuations due to a large current will cause no fluc tuations in voltages of the small-signal gnd. pay attention not to cause fluctuations in the gnd wiring pattern of external parts as well. 8 . selection of inductor it is recommended to use an inductor with a series resistance element (dcr) 50m or less. especially, in case output voltage is set 1.6v or more, note that use of a high dcr i nductor will cause an inductor loss , resulting in decreased output voltage. should this condition continue for a specified period (soft start time + timer latch time), output short circuit protection will be activated a nd output will be latched off. when using an inductor over 50m , be careful to ensure adequate margins for variation between external devices and this ic, including transient as well as static characteristics. furthermore, in any case, it is recommended to start up the out put with en after supply voltage is within operation range. resistor transistor (npn) n n n p + p + p psubstrate gnd parasitic element pin a n n p + p + p psubstrate gnd parasitic element pin b c b e n gnd pin a parasitic element pin b other adjacent elements e bc gnd parasitic element
technical note 17/17 www.rohm.com 2010.06 - rev. a ? 2010 rohm co., ltd. all rights reserved. bd91361muv ordering part number b d 9 1 3 6 1 m u v - e 2 part no. part no. 9136 1 (36: adjustable (0.8 ~ 3.3v)) package muv : vqfn020v4040 packaging and forming specification e2: embossed tape and reel ? order quantity needs to be multiple of the minimum quantity. embossed carrier tape tape quantity direction of feed the direction is the 1pin of product is at the upper left when you hold reel on the left hand and you pull out the tape on the right hand 2500pcs e2 () direction of feed reel 1pin (unit : mm) vqfn020v4040 2.10.1 1 15 11 20 16 5 10 6 0.5 1.0 0.25 +0.05 - 0.04 2.10.1 0.40.1 c0.2 1.0max 0.02 +0.03 - 0.02 (0.22) 4.00.1 4.00.1 1pin mark 0.08 s s
r1010 a www.rohm.com ? 2010 rohm co., ltd. all rights reserved. notice rohm customer support system http://www.rohm.com/contact/ thank you for your accessing to rohm product informations. more detail product informations and catalogs are available, please contact us. notes no copying or reproduction of this document, in part or in whole, is permitted without the consent of rohm co.,ltd. the content specied herein is subject to change for improvement without notice. the content specied herein is for the purpose of introducing rohm's products (hereinafter "products"). if you wish to use any such product, please be sure to refer to the specications, which can be obtained from rohm upon request. examples of application circuits, circuit constants and any other information contained herein illustrate the standard usage and operations of the products. the peripheral conditions must be taken into account when designing circuits for mass production. great care was taken in ensuring the accuracy of the information specied in this document. however, should you incur any damage arising from any inaccuracy or misprint of such information, rohm shall bear no responsibility for such damage. the technical information specied herein is intended only to show the typical functions of and examples of application circuits for the products. rohm does not grant you, explicitly or implicitly, any license to use or exercise intellectual property or other rights held by rohm and other parties. rohm shall bear no responsibility whatsoever for any dispute arising from the use of such technical information. the products specied in this document are intended to be used with general-use electronic equipment or devices (such as audio visual equipment, ofce-automation equipment, commu- nication devices, electronic appliances and amusement devices). the products specied in this document are not designed to be radiation tolerant. while rohm always makes efforts to enhance the quality and reliability of its products, a product may fail or malfunction for a variety of reasons. please be sure to implement in your equipment using the products safety measures to guard against the possibility of physical injury, re or any other damage caused in the event of the failure of any product, such as derating, redunda ncy, re control and fail-safe designs. rohm shall bear no responsibility whatsoever for your use of any product outside of the prescribed scope or not in accordance with the instruction manual. the products are not designed or manufactured to be used with any equipment, device or system which requires an extremely high level of reliability the failure or malfunction of which may result in a direct threat to human life or create a risk of human injury (such as a medical instrument, transportation equipment, aerospac e machinery, nuclear-reactor controller, fuel- controller or other safety device). rohm shall bear no responsibility in any way for use of any of the products for the above special purposes. if a product is intended to be used for any such special purpose, please contact a rohm sales representative before purchasing. if you intend to export or ship overseas any product or technology specied herein that may be controlled under the foreign exchange and the foreign trade law, you will be required to obtain a license or permit under the law.

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