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1/15 www.rohm.com 2009.05 - rev.a ? 2009 rohm co., ltd. all rights reserved. large current external fet controller type switching regulators single/dual-output high-frequency step-down switching regulator(controller type) BD9842FV overview BD9842FV is an ic containing two circuits of switching regulator controller by pulse width modulation system. both of two circuits can be used fo r step-down dc/dc converter operation. in addition, the package is designed compact, and is optimum for compact power supply for many kinds of equipment. feature 1) high voltage resistance input (vcc=35v) 2) fet driver circuit is contained (step-down circuit 2 output). 3) error amplifier reference voltage (1.0v ? 1%) and reg output circuit (2.5v) are contained. 4) overcurrent detection circuit is contained. 5) soft start and pause period can be adjusted. 6) three modes of standby, master, and slave can be switched. (iccs = 0 ua typ in standby mode.) 7) on/off control is enabled independently for each channel. (dt terminal) application lcd, pdp, pc, av, printer, dvd, projector tv, fax, copy machine, measuring instrument, etc. absolute maximum rating item symbol rating unit supply voltage vcc 36 v permissible loss pd 812 *1 mw out terminal voltage resistance out vcc-7v to vcc v c5v terminal voltage resistance c5v vcc-7v to vcc v operation temperature range topr -40 to +105 c storage temperature range tstg -55 to +150 c joint temperature tjmax 150 c *1 when glass epoxy board 70.0 mm ? 70.0 mm ? 1.6 mm is installed onboard. r educed by 6.5 mw/c above ta=25 ? c. operating condition (ta=25 ? c) item symbol range unit supply voltage vcc 3.6 to 35 v output terminal voltage out c5v ? vcc v timing capacity cct 47 to 3000 pf oscillation frequency fosc 100 to 1500 khz stb input voltage stb 0 to vcc v no.09028eat06
BD9842FV technical note 2/15 www.rohm.com 2009.05 - rev.a ? 2009 rohm co., ltd. all rights reserved. electric characteristics (ta25 ? c, vcc=6v unless otherwise specified) item symbol standard value unit condition min. typ. max. [vref output unit] output voltage v ref 2.450 2.500 2.550 v i o =0.1 ma input stability line reg. 1 10 mv vcc=3.6 v 35 v load stability load reg. 2 10 mv i o =0.1 ma 2 ma current capacity i omax 2 13 ma v ref =(typ.) 0.95 [triangular wave oscillator] oscillation frequency f osc 95 106 117 khz c cp =1800 pf frequency fluctuation f dv 0 1 % vcc=3.6 v 35 v ct source current i ctso 190 200 210 a ct=1.75 v ct sink current i ctsi 190 200 210 a ct=1.75 v [soft start unit] ss source current i ssso 1.4 2 2.6 a ss=0.5 v ss sink current i sssi 5 12 ma ss=0.5 v [pause period adjusting circuit] dt input bias current i dt 0.1 1 a dt=1.75 v dt sink current i dtsi 1 3.3 ma dt=1.75 v, (ocp+)-(ocp-)=0.5 v [low input malfunction preventing circuit] threshold voltage v uth 3.0 3.2 3.4 v vcc start detection hysteresis v uhys 0.15 0.25 v [error amplifier] non-inverting input reference voltage v inv 0.99 1 1.01 v inv=fb reference voltage supply fluctuation dvinv 1 6 mv vcc=3.6 v 35 v inv input bias current i ib 0 1 a inv=1 v open gain av 70 85 db max output voltage v fbh 2.30 vref v min output voltage v fbl 0.6 1.3 v output sink current i fbsi 0.5 1.5 ma fb=1.25 v, inv=1.5 v output source current i fbso 50 105 a fb=1.25 v, inv=0.5 v [pwm comparator] input threshold voltage (fosc=100khz) vt 0 1.4 1.5 1.6 v on duty 0% vt 100 1.9 2 2.1 v on duty 100% [output unit] output on resistance h r onh 4.0 10 ? r onh =( v cc -out)/iout, iout=0.1 a output on resistance l r onl 3.3 10 ? r onl =(out-c5 v)/iout, iout=0.1 a c5v clamp voltage v clmp 4.5 5 5.5 v v clmp = v cc -c5v , v cc 7 v [overcurrent protection circuit] overcurrent detection threshold voltage v ocpth 0.04 0.05 0.06 v voltage between (ocp+) and (ocp-) ocp-input bias current i ocp - 0.1 10 a ocp+= v cc, ocp-= v cc -0.5 v overcurrent detection delay time tdocpth 200 400 ns ocp-= v cc v cc -0.2 v overcurrent detection minimum retention time tdocpre 0.8 1.6 ms ocp-= v cc -0.2 v v cc [standby changeover unit] single channel stop threshold voltage v dtthl 1.1 1.25 1.4 v dt terminal h/l standby mode setting range v stbl 0 0.5 v slave mode setting range v stbm 2.4 2.5 2.6 v active (master) mode setting range v stbh 3 v cc v stb flow-in current i stb 70 100 a stb=6 v [device overall] standby current i ccs 0 1 a stb=0 v average power consumption i cca 1.5 3 6 ma inv=0 v, fb=h, dt=1.75 v * radiation resistance de sign is not applied.
BD9842FV technical note 3/15 www.rohm.com 2009.05 - rev.a ? 2009 rohm co., ltd. all rights reserved. 2.480 2.485 2.490 2.495 2.500 2.505 2.510 2.515 2.520 0 5 10 15 20 25 30 35 40 supply voltage: vcc(v) reference voltage: vref(v) ta=25c 0 1 2 3 4 5 6 7 8 9 10 -50 -25 0 25 50 75 100 125 ambient temperature: ta(c) standby current: iccs(ua) vcc=6v 0 1 2 3 4 5 6 7 8 0 5 10 15 20 25 30 35 40 supply voltage: vcc(v) circuit current: icca(ma) ta=25c 0 1 2 3 4 5 6 7 8 -50 -25 0 25 50 75 100 125 ambient temperature: ta(c) circuit current: icca(ma) vcc=6v 2.480 2.485 2.490 2.495 2.500 2.505 2.510 2.515 2.520 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 reference output current: iref(ma) reference voltage: vref(v) ta=25c vcc=6v 2.480 2.485 2.490 2.495 2.500 2.505 2.510 2.515 2.520 -50 -25 0 25 50 75 100 125 ambient temperature: ta(c) reference output voltage: vref (v) vcc=6v 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 erramp input voltage: vinv(v) erramp input current: iib(a ) fig.7 uvlo threshold temperature characteristics fig.8 acteristics fig.11 fb output source current fig.12 fb output sink current fig.10 error amplifier reference voltage temperature characteristics fig.9 error amplifier input current ta=25 2.5 2.6 2.7 2.8 2.9 3 3.1 3.2 3.3 3.4 3.5 -50 -25 0 25 50 75 100 125 ambient temperature: ta(c) uvlo threshold: vuth(v) 0.99 0.992 0.994 0.996 0.998 1 1.002 1.004 1.006 1.008 1.01 -50 -25 0 25 50 75 100 125 ambient temperature: ta(c) erramp reference voltage: vinv(v) vcc=6v 0 20 40 60 80 100 120 140 0 1 2 3 4 erramp output voltage: vfb(v) fb source current: ifbso(a) ta=85c ta=25c ta=-40c vcc=6.0v -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 0.5 1 1.5 2 erramp output voltage: vfb(v) fb sinkt current: ifbsi(ma) vcc=6.0v ta=85c ta=25c ta=-40c phase gain -20 0 20 40 60 80 100 frequency [hz ] loop gain :closed [ db ] -270 -225 -180 -135 -90 -45 0 phase shift [ deg ] 100 1k 10k 100k 1m 10m vcc=6v phase gain reference data fig.1 standby current temperature characteristics fig.2 circuit current in operation fig.3 circuit current temperature characteristics in operation fig.4 vref supply voltage characteristics fig.5 vref current capability fig.6 vref temperature characteristics
BD9842FV technical note 4/15 www.rohm.com 2009.05 - rev.a ? 2009 rohm co., ltd. all rights reserved. 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 ss voltage: vss(v) ss source current: issso(a) vcc=6.0v 0 5 10 15 20 25 30 35 0 0.5 1 1.5 2 ss voltage: vss(v) ss sink current: isssi(ma) vcc=6.0v ta=85c ta=25c ta=-40c 80 90 100 110 120 -50 -25 0 25 50 75 100 125 ambient temperature: ta(c) frequency: fosc(khz) vcc=6v ccp=1800pf 0 1 2 3 4 5 6 7 0 0.5 1 1.5 2 2.5 dt input voltage: vdt(v) dt input current: idt(a) vcc=6.0v ta=25c 0 1 2 3 4 5 6 7 0 0.5 1 1.5 2 2.5 dt input voltage: vdt(v) dt sink current: idt(ma) ta=85c ta=25c ta=-40c vcc=6.0v fig.19 output duty-vdt characteristics (100khz) fig.23 stb flow-in current fig.24 overcurrent detection voltage temperature characteristics fig.21 output on resistance h (r onh ) fig.22 output on resistance l (r onh ) fig.20 output duty-vdt characteristics (1.5mhz) 0 10 20 30 40 50 60 70 80 90 100 1.4 1.6 1.8 2 2.2 dt input voltage: vdt(v) output duty cycle: duty(%) vcc=6.0v ta=25c 0 10 20 30 40 50 60 70 80 90 100 1.4 1.6 1.8 2 2.2 dt input voltage: vdt(v) output duty cycle:duty(%) vcc=6.0v ta=25c 0 5 10 15 20 25 30 35 40 vcc -0.05 -0.10 -0.15 -0.20 vout(v) ids(ma) ta=85c ta=25c ta=-40c vcc=6.0v vcc vcc vcc vcc ta=25c 0 5 10 15 20 25 30 35 40 c5v -0.05 -0.10 -0.15 -0.20 vout(v) ids(ma) ta=85c ta=25c ta=-40c vcc=6.0v c5v c5v c5v c5v vstb(v) istb(a) 0 100 200 300 400 500 600 700 800 0 5 10 15 20 25 30 35 40 ta=85c ta=25c ta=-40c vcc=35v 30 35 40 45 50 55 60 65 70 -50 -25 0 25 50 75 100 125 ambient temperature: ta(c) ocp threshold: vocpth(mv) vcc=6v reference data fig.14 ss sink current fig.13 ss source current fig.16 oscillation frequency temperature characteristics fig.17 dt bias current fig.18 dt sink current 0 1 2 3 4 5 -50-25 0 25 50 75100125 ambient temperature: ta(c) ss source current: issso(ua) vcc=6.0v fig.15 ss source current temperature characteristics
BD9842FV technical note 5/15 www.rohm.com 2009.05 - rev.a ? 2009 rohm co., ltd. all rights reserved. fig.26 c5v load regulation fig.27 c5v line regulation fig.25 c5v saturation voltage 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 0 50 100 150 200 250 ic5v(ma) vc5v(v) vcc=5.0v ta=25c 4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 5.4 5.5 0 5 10 15 20 25 30 35 40 ic5v(ma) vcc-vc5v(v) vcc=6.0v ta = 2 5 c 0 1 2 3 4 5 6 7 8 9 10 0 5 10 15 20 25 30 35 40 supply voltage: vcc(v) vcc-vc5v(v) ta=25c reference data block diagram fig.28 block diagram + + - err + + - pwm ls drv vref 2a vcc c5v + - + pwm ls drv vcc c5v + - + err vref 2a 1v10mv 50mv10mv ocp1 c5v vcc ocp + - ocp2 c5v vcc ocp - + vref vcc c5v reg (2.5v) vref dt1 fb1 ss1 inv1 ct inv2 ss2 fb2 dt2 vcc vcc stb ocp1 + ocp1 - ocp2+ ocp2- gnd out2 out1 c5v 1v10mv 50mv10mv reg (vcc-5v) dt1off ss1off ss2off dt2off tsd tsd 2v 1.5v + - 2.8v qs r uvlo master /slave muster mode latch + - - 200a 200a 1.5v 2.0v master /slave osc ocp1 dt1low ss1off dt1off uvlo tsd dt2off dt2low ocp2 protection logic uvlo uvlo vcc vref c5v 3.2v 2.2v 3v + - dt1low 1.25v dt + - dt2low 1.25v dt ss2off stb hold time (1.6msec) hold time (0.2msec) hold time (1.6msec)
BD9842FV technical note 6/15 www.rohm.com 2009.05 - rev.a ? 2009 rohm co., ltd. all rights reserved. terminal layout fig.29 terminal layout terminal number terminal name function 1 ct timing capacity external terminal 2 dt2 output 2 dead time setting terminal 3 ss2 output 2 soft start time setting terminal 4 inv2 output 2 error amplifier - input terminal 5 fb2 output 2 error amplifier output terminal 6 gnd ground 7 ocp2- output 2 overcurrent detector - input terminal 8 ocp2+ output 2 overcurrent detector + input terminal 9 c5v output l side voltage (vcc-5v) 10 out2 output 2 11 out1 output 1 12 vcc power terminal 13 ocp1+ output 1 overcurr ent detector + input terminal 14 ocp1- output 2 overcurr ent detector - input terminal 15 stb standby mode setting terminal 16 fb1 output 1 error amplifier output terminal 17 inv1 output 1 error amplifier - input terminal 18 ss1 output 1 soft start time setting terminal 19 dt1 output 1 dead time setting terminal 20 vref reference voltage (2.5v) output terminal vref dt1 ss1 inv1 fb1 stb ct dt2 ss2 inv2 fb2 gnd ocp1- ocp1+ vcc out1 ocp2- ocp2+ c5v out2 ssop-b20
BD9842FV technical note 7/15 www.rohm.com 2009.05 - rev.a ? 2009 rohm co., ltd. all rights reserved. 10 100 1000 10000 10 100 1000 10000 ct timing capacity (pf) oscillation frequency (khz) ta=25 operation description of each block and function 1) reg (reference voltage unit) as for reg (2.5v), reference voltage (2.5v) stabilized better than supply voltage input to vcc terminal (pin 12) is supplied as an operation voltage of ic internal circuit, as well as outpu t outside through vref terminal (pin 20). insert a capacitor of 0.1 micro f to vref terminal. as for reg (vcc-5v), voltage of vcc-5v is supplied as power supply (ldo) of driver circui t (drv) of out terminal (pin 10 and 11), as well as output outside through c5v terminal (pin 9). insert a capacitor of 1 micro f to vcc terminal of c5v terminal. 2) err amp 1/2 (error amplifier) in step-down application, inverting input inv (pin 4 and 17) of error amplifier detects output voltage by sending back feedback current from final output stage (on load side) of switching regulator. r1 and r2 connected to this input terminal are resistor for setting output voltage. non-inverting input of amplifier is a reference input of error amplifier itself by adding reference voltage (1.0v) inside ic. rf and cf connected between fb (pin 5 and 16), which is output from error amplifier, and inv (pin 4 and 17) are for feedback of error amplifier, and allows setting of loop gain. fb is connected to pwm comp 1/2 and supplied as non-inverting input. setting of output voltage (vo) is as follows: vo = ? 1.0v 3) osc (triangular wave oscillating unit) generates triangular wave for inputting to pwm comp 1/2. first, timing capacitor c ct connected between ct terminal (pin 1) and gnd is charged by constant current (200 micro a) generated inside ic. when ct voltage reaches 2.0 v typ, the comparator is switched, and then c ct is discharged by constant current (200 micro a). then, when ct voltage re aches 1.5v, the comparator is switched again, and c ct is charged again. this repetiti on generates triangular wave. oscillation frequency is determined by externally mounted c ct through theoretical formula below: fosc P ict/(2 ?c ct ? vosc) ict : ct sink/source current 200 micro a typ vosc : triangular wave amplifying voltage (vt0-vt100) 0.50 v typ. here, error from theoretical formula is caused by delay of internal circuit at a high frequency. see the graph in fig 31 for setting. this triangular wave can be taken out through ct terminal. it is also possible to input the oscillator externally by switching to slave mode described later. waveform input here in principle must be triangular wave of vpeak = (1.5v ? 2.0v) equivalent to internal oscillation circuit. external input voltage range v ct : 1.4 v < v ct < 2.3 v standard external c ct range c ct : min.47 pf ? max.3000 pf r1+r2 r2 vo r 1 r 2 4/17 5/16 inv fb erramp1/2 rf cf 1v fig.30 fig.31
BD9842FV technical note 8/15 www.rohm.com 2009.05 - rev.a ? 2009 rohm co., ltd. all rights reserved. 4) soft start 1/2 (soft start function) it is possible to provide ss terminal (pin 3 and 18) with soft start function by connecting c ss as shown on the right. soft start time tss is shown by the formula below: tss = css ? (ex) when css = 0.1 micro f tss = = 5 [msec] in order to function soft start, time must be set longer enough than start time of power supply and stb. it is also possible to provide function of soft start by connecting the resistor (r1/r2) and capacitor (c dt ) to dt terminal (pin 2 and 19) as shown on the right. 5) pwm comp 1/2 - dead time (pause period adjusting circuit - dead time) dead time can be set by applying voltage dividing resistance between vref and gnd to dt terminal (pin 2 and 19). pwm comp compares the input dead time voltage (dt terminal voltage) and error voltage from err amp (fb terminal voltage) with triangular wave, and turns off and on the output. when dead time voltage < error voltage, duty of output is determined by dead time voltage. (when dead time setting is not used, pull up dt terminal to vref terminal with resistor approx 10 k ohms.) dead time voltage vdt in fig 32 is shown by the formula below: vdt vref ? relation between vdt and duty [see the graph on the right.] duty 100% duty 0% min typ max min typ max when f = 100khz 1.9 2. 0 2.1 1.4 1.5 1.6 when f = 1.5mhz 1.95 2. 1 2.25 1.35 1.5 1.65 when oscillation frequency is high, upper/lower limit of triangular wave (vt100/vt0) is shifted by delay time of comparator to directions expanding amplitude. be careful. 6) ocp comp 1/2 (overcurrent detection circuit) this function provides protection by fo rcibly turning off the output when abnormal overcurrent flows due to sh orting of output, etc. when voltage between terminal ocp+(pin 8 and 13)/ocp-(pin 7 and 14) monitoring the current with sense resistor exceeds overcurrent detection voltage (50 mv typ), it is determined as overcurrent condition, and switching operation is stopped immediately by setting out to "h" and dt,ss (and fb) to "l". it is automatically recovered when voltage between terminal ocp+/ocp- is below overcurrent detection voltage. in addition, although hysteresis, etc. are not set here, minimum detection retention time (1.6mstyp) is set for suppressing the heati ng of fet, etc. (see the timing chart.) when the overcurrent detection circuit is not used, short-circuit both terminal ocp+/ocp- to vcc pin. vinv issso css : ss terminal connection capacity vinv : error amplifier reference voltage (1v typ) issso : ss source current (2 micro a typ) vref dt r 1 r 2 c dt 20 2/19 vref inv ss erramp 2ua css 1vtyp. 3/18 4/17 fig.32 fig.33 [unit : v] 1 1.2 1.4 1.6 1.8 2 2.2 2.4 100 1000 10000 fosc[khz] vdt[v] vt100 vt0 fig.34 vin ocp+ ocp- ocp comp ??? 8/13 7/14 50mvtyp. fig.35 direction of current sense resi r to r 0.0110 -6 1 2 10 -6 r2 r1 r2
BD9842FV technical note 9/15 www.rohm.com 2009.05 - rev.a ? 2009 rohm co., ltd. all rights reserved. 7)stb (standby/master/slave function) standby mode, slave mode, and normal (master) mode can be switched by stb terminal (pin 15). 1. when stb<0.5v, standby mode is set. output stops (out=h) and reg also stops. circu it current is also isc = 0 microa here. 2. when 2.4v3.0v, normal operation mode is set. all circuits operate and triangular wave is outpu t. use the controller normally in this range. precaution here is as follows: when switching between standby mode and normal (master ) mode, the current passes the area of slave mode. when starting, if the time when 0.5v BD9842FV technical note 10/15 www.rohm.com 2009.05 - rev.a ? 2009 rohm co., ltd. all rights reserved. timing chart starting characteristics (uvlo cancel) and standby operation overcurrent detection (when output is shor ted: overcurrent detection and cancel are repeated at a specified time interval.) item min typ. max. threshold voltage (vcc) 3.0 3.2 3.4 hysteresis - 0.15 0.25 threshold voltage (vref) 2.0 2.2 2.4 threshold voltage (c5v) - 3.0 3.4 ss ocp+ ocp- vcc vocpth ocp+ ocp- dt fb ct fb dt c5v vcc vcc-5v out out c5v dt"l ss"l (fb"l) dt(fb)ss_ ^? ^? ^? ??B???rg tdocpre 1.6ms ?rW?rg tdocpth delay time in detection overcurrent detection overcurrent detection overcurrent detection minimum time retaining detection condition open dt (fb) and ss. stb vref 1v ss dt fb ct vcc vcc-5v out c5v c5v dtuvlog?? fbuvlog?? :uvlogvref???? out vref2.2vuvlo(vref) uvlo(tsd)?rg(0.2msec) uvlo(vcc,vref)??? (vcc-5v)reg c5vvcc-3vuvlo(c5v) 1.8vtyp. 0.9vtyp. ct uvloo?B vcc vcc3.2vuvlo(vcc) vref?R vref???R uvlo? vccvrefc5v????B?????rg? vccvrefc5v?uvlo??????? ss???O? ??`???rgS???? gH??????LrgO? uvlo voltage [unit: v] (1) uvlo (vcc) is canceled when vcc>3.2v. (2) uvlo (vref) is canceled when vref>2.2v. ? uvlo (tsd) minimum retention time (0.2 ms) set ss by external capacity. although ss is notated by the same time axis in the figure for showing the image, actually set sufficiently longer time in comparison with the cycle of triangular wave. ? uvlo when 1. vcc, 2. vref, and 3. c5v are all in normal condition, uvlo is canceled after the minimum retention time.when uvlo is detected at any of 1. vcc, 2. vref, and 3. c5v, output is stopped immediately. uvlo protection condition ct: pull-up to vref during uvlo period dt: pull-down during uvlo fb: pull-down during uvlo uvlo(vcc,vref) is cancelled, (vcc-5v)reg is started. (3) uvlo (c5v) is canceled when c5v BD9842FV technical note 11/15 www.rohm.com 2009.05 - rev.a ? 2009 rohm co., ltd. all rights reserved. example of application circuit fig.37 1) setting of output unit coil (l) and capacitor (co) set the coil and capacitor as follows in step-down application: when load current gets heavy, the current flowing through the co il gets continuous, and the relation below is established: l = ? normally set delta il below 30% of the maximum output current (iomax). when l-value is made greater, ripple current (delta il) becomes smaller. in general, the greater the l-value is, the smaller the permissible current of coil gets, and when the current exceeds permissible current, the coil is saturated and l-value changes. contact the coil manufacturer and check permissible current. select an output capacitor co by esr (equivalent serial resistance) property of capacitor. output ripple voltage (delta vo) is almo st esr of output capacitor, therefore, ? vo P ? il esr esr: equivalent serial resi stance of output capacitor co the relation above is established.ripple component by outpu t capacitor is small enough to be neglected in comparison with ripple component by esr in many cases. as for co value, it is recommended to use a sufficiently large capacitor with a capacity that satisfies esr condition. determine a switching element by peak current. peak current isw flowing through the switching element is equal to peak current flowing through the coil, t herefore the equation below is established. isw (peak) = io + ? il/2 select a switching element of permissible current having a suffic ient margin over peak current calculated by the equation. inv1 fb1 vref ss1 dt1 stb ocp1- ocp1+ vcc out1 ct ss2 inv2 fb2 dt2 gnd ocp2- ocp2+ c5v out2 vo1 (step-down) vo2 (step-down) vin 2.5v 1112 13 14151617 18 1920 10 987654321 stb = vref use in slave ic mode, slave ic master ic use in slave ic mode, ct = ct slave ic master ic to master ic ct pin co lo co lo BD9842FV ? il ts w vin (vin-vo)vo vin: input voltage tsw: 1/(switching frequency) delta il: ripple current of coil
BD9842FV technical note 12/15 www.rohm.com 2009.05 - rev.a ? 2009 rohm co., ltd. all rights reserved. 2) example of overcurrent protection circuit insert a sense resistor between the source and vin of output pch-fet for detecting overcurrent as shown in the figure. refer to the formula below for determining a sense resistor and select permissible loss ensuring a margin. rsense iocp is a peak current isw (p eak) here, and the amperage for output load is an overcurrent setting amperage minus ripple current component (delta i l /2), etc. (see the formula on p10.) there is a time delay approx 200ns from detection until stop of output is made (pulse of approx 100 ns c auses delay time but detection is made), and an error may be caused from the value above. in addition, input to overcurrent detection unit is such a sens itive circuit, and wrong detection by noise may be possible. when wrong detection occurs, try to eliminate noise by the resist or r1 and r2 or capacitance c1, c2, c3, and c4 shown above. 3) example of output on/off control circuit when stopping the whole circuit, set stb terminal to "low (stb<0.5v) to stop switching and reduce power consumption of ic to 0 microa (typ). also when switching on and off for each channel, control is fixed to off by setting dt terminal of desired channel to "low (dt<1.25v)". this control is independent for each channel, and when dt="l", ss terminal and fb terminal are also discharged, and soft start is enabled in restarting. 4) example of master/slave (syn c multi-ch output) operation circuit this ic is set to slave mode by setti ng the input of stb terminal at 2.5v ? 0.1v, and multi-channel output is enabled with frequency synchronized. (fig.40) however, ct terminal has high impedance in slave mode status, and triangular wave is generated by ct waveform of master mode ic. therefore t he example of master slave circuit below is recommended when starting and stopping in order to avoid malfunction by star t/stop timing of master ic and slave ic. as for output, it is recommended to control on/off reliably with dt terminal. also, oscillation frequency is determined by capacitor (c ct ) connected to ct. when the slave ic is large in number as well as oscillation frequency is high, parasitic capacity by board wiring in contact with ct cannot be ignored, and preset frequency may be drifted. be careful. example of master/slave circuit configuration is shown below. if any other configuration is to be applied, inform our personnel in charge. dt ss dtcomp ch out ch ? ??? 2/19 3/18 1.25vtyp. vref fig.39 each ch to out di g ital fig.40 ??? high?R2.5v?? stb ?ic ic n ct ct ? stb ? stb? master stb signal master ic common slave input a signal of high voltage 2.5v synchronized with master. vref stb stb vref ?ic ic ?tr[emd9] 0.1uf 0.1uf 0.1uf ct ct cct dt dt ?tr[dtc114y] ? chon/ off chon/ off 10k 10k ?tr[dtc114y] 1k fig 41. example of master/slave 1 stand master ic slave ic eac h eac digital tr [emd9] digital tr [dtc114y] digital tr [dtc114y] vref stb stb vref ?ic ic 0.1uf 0.1uf ct ct cct dt dt ?tr[dtc114y?] ? on/off 10k pnp??? [2sa1774?] h3.3v lgnd fig 42. example of master/slave 2 pnp transistor [such as 2sa1774] master ic slave ic standby signal on/off control current restriction digital tr [such as dtc114y] vocpth ioc p vocpth :overcurrent detection voltage (50 mv typ) iocp : overcurrent detection setting current fig.38 vin r1 ocp+ ocp- out c1 r2 c2 c3 ??? ocp comp vocpth=50mv 8/13 7/14 10/11 c4 sense
BD9842FV technical note 13/15 www.rohm.com 2009.05 - rev.a ? 2009 rohm co., ltd. all rights reserved. 5) about board layout in order to make full use of ic performance, fully invest igate the items below in addition to general precautions. ? each output of ocp+/ocp- is such a sensitive circuit. when wiring is routed around, it is easily subjected to noise. try to make the wiring as short as possible. ? switching of large current is likely to generate noise. try to make the large current route (vin, rsense, fet, l, di, and cout) as thick and short as possible, and try to apply one-point grounding for gnd. out terminal is also a switching line, and it must be wired along a distance as short as possible. (when multi-layer board is used, shielding by intermediate layer also seems to be effective.) ?c ct and c vref are reference of all, and must be wired along the shortest distance to gnd of ic stabilized to be protected against external influence. ? also be careful not to allow common impedance to sense family gnd. (6) pin processing of channel unused when only one channel is used, process unused channels as shown above. i/o equivalent circuit diagram pin 1 (ct) pin 2, and 19 (dt1 and dt2) pin 3, and 18 (ss1 and ss2) pin 4, and 17 (inv1 and inv2) pin 5, and 16 (fb1 and fb2) pin 7, and 14 (ocp1- and ocp2-) pin 9 (c5v) pin 10, and 11 (out1 and out2) pin 8, and 13 (ocp1+ and ocp2+) pin 15 (stb) pin 20 (vref) pin 6 (gnd) pin 12 (vcc) dt vref vref ss vref vref vref vcc ct vref vref vref vref vref inv vref vref fb vref vref ocp- vcc c5v c5v vcc ocp+ vcc c5v vcc c5v c5v vcc vcc vcc vcc out vcc vcc c5v c5v gnd vcc stb vcc vre f vref vcc vcc vref vcc vcc vref vref dt ss inv fb ocp- ocp+vcc out 20 19 18 17 16 14 13 12 11 10 7 8 5 4 3 2 fig.43
BD9842FV technical note 14/15 www.rohm.com 2009.05 - rev.a ? 2009 rohm co., ltd. all rights reserved. notes for use 1) about maximum absolute rating when the maximum absolute rating of application voltage or operation voltage range is exceeded, it may lead to deterioration or rupture. it is impossible to forecast rupt ure in short mode or open mode. when a special mode is expected exceeding the maximum absolute rating, try to take a physical safety measure such as a fuse. 2) gnd potential ensure that the potential of gnd terminal is the minimum in any operation condition. also ensure that no terminal except gnd terminal has a voltage below gnd voltage including actual transient phenomenon. 3) thermal design allow a sufficient margin in thermal design in consideration of permissible loss (pd) in actual use condition. 4) shorting between terminals and wrong attachment when attaching an ic to a set board, pay full attention to the direction of ic and dislocation. wrong attachment may cause rupture of ic. in addition, when shorting is caused by foreign substance placed between outputs or between output and power supply-gnd, rupture is also possible. 5) operation in intense magnetic field use in intense magnetic field may result in malfunction. be careful. 6) inspection on set board in inspection on set board, when a capacitor is connected to a terminal with low impedance, stress may be applied to ic, therefore be sure to discharge electricity in each process. apply grounding to assembling process for a measure against static electricity, and take enough care in transport and stor age. when connecting a jig in inspection process, be sure to turn off power before detaching ic. 7) about ic terminal input this ic is a monolithic ic, and contains p + isolation and p board for separating elements between each element. this p-layer and n-layer of each element form p-n junction, and many kinds of parasitic elements are constituted. (see fig 43.) for example, when resistor and transistor are connected with a terminal as shown below. p-n junction operates as a parasitic diode when gnd>(terminal a) for resistor, and when gnd>(terminal b) for transistor (npn). in addition, when gnd>(terminal b) for transistor (npn), parasitic npn transistor is operated by n-layer of some other elements in the vicinity of parasitic diode mentioned above. parasitic element is inevitably generated by potential because of ic structure. operation of parasitic element causes interference with circuit operation, and may lead to malfunc tion, and also may cause rupture. therefore when applying a voltage lower than gnd (p board) to i/o terminal, pay full attention to usage so that parasitic elements do not operate. fig.44 ??? npn) ?? ? b b a) ?? ? e c gnd gnd p p p gnd gnd gnd resistor (terminal a) (terminal b) (terminal b) (terminal a) p board p board parasitic element parasitic element parasitic element transistor (npn) parasitic element a nother element in the vicinity
BD9842FV technical note 15/15 www.rohm.com 2009.05 - rev.a ? 2009 rohm co., ltd. all rights reserved. ordering part number b d 9 8 4 2 f v - e 2 part no. part no. 9842 package fv : ssop-b20 packaging and forming specification e2: embossed tape and reel (ssop-b20) (unit : mm) ssop-b20 0.1 11 10 20 1 0.1 0.1 6.4 0.3 4.4 0.2 6.5 0.2 0.15 0.1 0.22 0.1 0.65 1.15 0.1 0.3min. ? 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
r0039 a www.rohm.com ? 2009 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 specified herein is subject to change for improvement without notice. the content specified 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 specifications, 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 specified 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 specified 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 specified in this document are intended to be used with general-use electronic equipment or devices (such as audio visual equipment, office-automation equipment, commu- nication devices, electronic appliances and amusement devices). the products specified 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, fire or any other damage caused in the event of the failure of any product, such as derating, redundancy, fire 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, aerospace 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 specified 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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