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technical note system power supply for tv series built-in 1ch fet synchronous rectification type dc/dc converters BD8621EFV description BD8621EFV has realized the high performance and reliabilit y required as a power supply for thin-screen tv. with built-in fet 1ch current mode contro l, the dc/dc converter series has the adv antage of high-speed load response and wide phase margin. due to the high-speed load response, it is most suitable for tv -purpose processors with increasingly high performance, and due to the wide phase margin it leaves a good margin for board pattern & constant setting and so facilitates its application design. as a high-reliability design, it has various built-in protection circuits (overcurre nt protection, output voltage abnormal prot ection, thermal protection, and off-latch function at the time of abnormality etc.), therefore as an advantage it does not easily damage in eve ry possible abnormal condition such as all-pin short circ uit test etc. and hence most suitable for thin-screen tv which requires the high r eliability. features 1) 3a output current 2) low rds(on) internal switches (pchmos:75m ? nchmos:55m ? ) 3) 1% reference voltage accuracy 4) programmable frequency : 250khz-1mhz 5) (frequency in programmable by adjusting rt re sistance or synchronizing with synclk terminal.) 6) terminal rt open/short detecting function 7) over current protection function 8) output over voltage/low voltage pr otection function (over : fb > vref +60mv , low : fb < vref -60mv) 9) timer off latch function in abnormal circumstances 10) thermal shutdown function 11) under voltage protection 12) soft start/start delay circuit 13) soft start time out function 14) protecting bus function with terminal pdet 15) htssop-b20 package jul. 2008
2 / 14 electrical characteristics (unless otherwise noted ta=25 , vin=3.3v, gnd=0v) parameter symbol specification value unit condition min typ max vin supply current (operating) i q _ active - 220 350 a v fb = 0.83v, v fc = 1v vin supply current (standby) i q _ stb y - 0 1 a v en = 0v reference voltage (vref) v re f 0.792 0.8 0.808 v output rise detection voltage v ov p 30 60 90 mv monitoring fb terminal output decrease detection voltage v lv p -90 -60 -30 mv monitoring fb terminal terminal pdet output current i pdet 0.4 - - ma v pdet < 0.3v oscillation frequency f os c 500 550 600 khz r rt = 220k ? pch fet on resistance r pfet - 75 110 m ? i sw = 1a nch fet on resistance r nfet - 55 90 m i sw = 1a uvlo voltage v uvl o 2.35 2.50 2.65 v sw leak current i lsw - 0 1 a v en = 0v, v in = 5.5v en terminal h threshold voltage v enh 1.1 - - v en terminal l threshold voltage v enl - - 0.4 v fc sink current i fcsi 10 20 - a fc source current i fcs o - -20 -10 a ss/delay terminal source current i sss o 2 4 6 a terminal pdet pull-up resistor r pdet 100 170 250 k ? v fb :fb terminal voltage, v en :en terminal voltage, v fc :fc terminal voltage, v pdet : pdet terminal voltage current capability should not exceed pd.
3 / 14 block diagram fig1 block diagram pin description no. symbol description explanation 1 sgnd signal gnd terminal small signal system gnd 2 fb feed back terminal output voltage detection 3 pdet off latch signal output protecting bus communication terminal 4 sw output terminal switching output 5 sw 6 pgnd power gnd terminal gnd for power mosfet 7 pgnd 8 pgnd 9 sw output terminal power mos output 10 sw 11 vin power supply input terminal power supply input. the decoupling is done to pgnd 12 vin 13 vin 14 vin 15 reg internal regulator synchronizable switching output termi nal frequency with external clock 16 en enable input on/off control for device operation 17 test terminal for test sgnd short in the set. 18 ss/delay soft start adjustment capacity connection terminal the soft start time is adjusted with the connected capacitor 19 fc error amplifier output error amplifier phase compensation point 20 rt frequency adjustment resistance connection terminal the switching frequency is set by the connected resistance
4 / 14 pin equivalence circuit diagram no. symbol explanation terminal equivalent circuit diagram 1 sgnd gnd (connected 0v) 2 fb output voltage detection terminal vin sgnd 2 3 pdet protecting bus i/o terminal 4,5,9,10 sw output terminal 6,7,8 pgnd power gnd (same voltage as sgnd) 11,12,13,14 vin power supply input terminal 5 6 7 vin pgnd 4 5 9 vin pgnd 10
5 / 14 no. symbol explanation terminal equivalent circuit diagram 15 reg internal regulator output voltage 16 en enable terminal 17 test using at test mode
6 / 14 no. symbol explanation terminal equivalent circuit diagram 18 ss /delay soft start time adjustment terminal 19 fc error amplifier compensation terminal 20 rt oscillator frequency adjustment terminal
7 / 14 operation description enable control the device can be controlled on/off by en terminal (16 pin) voltage. an internal circuit starts when ven reaches 1.1v. fig.2 on/off transition wave form in en controlling en terminal voltage ss terminal voltage output setting voltage
8 / 14 soft start time set function as for bd8623efv, output can do soft start without overshoot by charging soft start capacity (css) connected between ss and sgnd terminal. also, soft start time (tss) can be set by se tting soft start capacity (css) arbitrarily. osc oscillation frequency setting function the output oscillation frequency can be set by connecting resistance between terminal rt (20 pins) and sgnd (range = 250khz - 1mhz) the relation between rt terminal resistance a nd the oscillation frequency follows fig.3. 10 1000 10 100 1000 10000 rt terminal resistance[k] frequency[khz] fig.3 rt resistance-oscillation frequency switching frequency synchronization an internal transmitter of bd8623efv can be synchronized with the external clock signal connected with the terminal synclk (15 pins). the frequency of external clock can be set within the range of 250khz-1mhz. in this case, please set the rt resistance that may become about -20% value of the external clock frequency. be short-circuited synclk terminal to sgnd wh en a frequency synchronous function is not used.
9 / 14 protection function protection circuit is effective for destruction prevention due to accident so that avoid using under continuous protection operation. low voltage protection function (lvp) the voltage of the terminal fb (2 pins) is compared with internal reference voltage vref. if fb terminal voltage falls below v lvp (= vref -60mv) and the state continues for 500us, output changes to low voltage and the state is fixed. in that case , pdet (3pin) output changes to l. table 4-1 output low voltage protection function en terminal ss terminal fb terminal low voltage protection function low voltage protection operation >v enh >1.4v(typ) v lvp effective on v lvp off <1.4v(typ) - invalidity off v enh >1.4v(typ) v ovp effective on v ovp off <1.4v(typ) - invalidity off 10 / 14 under voltage lock ou t protection (uvlo) as for bd8623efv, the power-supply voltage decrease detection protection circuit is built in. it the input voltage decrease below the uvlo voltage (2.5v typ), the device state changes to the standby mode (moreover, to prevent the chattering of the output) hysteresis width of 100mv(typ) has been installed in the uvlo cancel voltage. rt terminal open/short protection function (rto/rts) rt terminal opening/short protection function prevent the clock from abnormal oscillation. if rt terminal open/short protection function is detect ed, output voltage changes to low level and is fixed. terminal rt opening/short protection function is av ailable if the state cont inue for 500usec, abnormal detection operates when the state continues about 500 sec(typ). soft start time-out function if vss doesn't exceed vssth within 64msec (typ) since a so ft start began, bd8629fs controls an off latch. vo is fixed in a low level. fig.5 soft start time-out thermal shut down function thermal shut down circuit (tsd circuit) is built into bd8623efv. when the temperature of the chip exceeds tjmax=175, the dc/dc converter is fixed in a low voltage. tsd function is aimed to shut down ic from thermal reckless driving under an abnormal state to exceed tjmax=175. it aims at neither protection nor the guarantee of the set. therefore, please do not use this function to protect the set. over current protection function the over current protection function has been achieved by limiting th e current that flows on high side mosfet. the current is controlled in every one cycle of the swit ching frequency. when an abnormal state continues for about 500 sec(typ), the output is fixed in a low level.
11 / 14 protecting bus function with terminal pdet the terminal pdet (3 pins) monitors whether ic is normal or not. when ic becomes abnormal, the pdet output is reduced at "l" level with the output voltage fixed ?l? level at the same time. moreover, it is possible to make the output fix in a low level by compulsorily reducing the terminal pdet at "l" level from the outside. when two or more bd8623efv is used in the application, this function prevents the ic from destroying, because one ic error transmits all other ics by pdet line in the condition that pdet terminals are connected each other. fig.6 protecting bus communication please give the terminal pdet as open when you do not use protecting bus function. error detection (off latch) release method bd8623efv enters the state of an off latch when the protection function operates. to release the off latch state, en terminal voltage should be changed to low level once time.
12 / 14 each characteristic reference data fig.7 output load response fig.8 output ripple 0 10 20 30 40 50 60 70 80 90 100 10 100 1000 10000 [%] ? [ma] fig.9 efficiency fig.10 soft start 1.00 ? 1.10 ? 1.20 ? 1.30 ? 1.40 ? 1.50 ? 0.0000 0.5000 1.0000 1.5000 2.0000 2.5000 3.0000 output ? voltage ? : ? vo[v] load ? current ? [a] fig.11 regulation 0.790 0.792 0.794 0.796 0.798 0.800 0.802 0.804 0.806 0.808 0.810 -25 0 25 50 75 100 ambie nt ? temperature ? : ? ta ? [ ] error ? amp ? reference ? vol tage ? : ?? vre f ? [v ] 3.0 3.3 3.5 3.8 4.0 4.3 4.5 4.8 5.0 -25 0 25 50 75 100 amb ie nt ? temperature ? : ? ta ? [ ] ss ? charge ? current ?? : ? is s ? [ a] fig.12 reference voltage - temperature charac teristic fig.13 ss charging current - temperature characteristic vin = 5v io = 3a vout : 20mv/div vin = 2v/div vout = 0.5v/div ss = 2v/div 1usec/div 10msec/div vout = 1.2v vin = 5.0v vin = 3.3v vin = 5v vout : 100mv/div io = 1a/div vin = 3.3v vin = 3.3v vin = 5.0v vout = 1.2v load current [ma] efficiency [%]
13 / 14 500.0 ? 510.0 ? 520.0 ? 530.0 ? 540.0 ? 550.0 ? 560.0 ? 570.0 ? 580.0 ? 590.0 ? 600.0 ? 2.533.544.555.5 frequency ? : ? fosc ? [khz] input ? voltage ? : ? vin ? [v] 500.0 510.0 520.0 530.0 540.0 550.0 560.0 570.0 580.0 590.0 600.0 -25 0 25 50 75 100 ambie nt ? temperature ? : ? ta ? [ ] frequency ? : ? fosc ? [k h z ] fi g .14 switchin g fre q uenc y - p ower-su pp l y volta g e characteristic fi g .15 switchin g fre q uenc y -tem p erature characteristic 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 2.533.544.555.5 inp ut ? vol tage ? : ? vin ? [v ] on \ resistance: ? ron ? [m ] 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 110.00 -25 0 25 50 75 100 ambie nt ? temperature ? : ? ta ? [ ] on \ resistance: ? ron ? [m ] fi g .16 pmos on resistance- p ower-su pp l y volta g e fi g .17 pmos on resistance-tem p erature characteristic 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 2.5 3 3.5 4 4.5 5 5.5 inp ut ? vol tage ? : ? vin ? [v ] on \ resistance: ? ron ? [m ] 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 -25 0 25 50 75 100 ambie nt ? temperature ? : ? ta ? [ ] on \ resistance: ? ron ? [m ] fi g .18 nmos on resistance- p ower-su pp l y volta g e fi g .19 nmos on resistance-tem p erature characteristic 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 -25 0 25 50 75 100 ambie nt ? temperature ? : ? ta ? [ ] en ? vol tage ? high: ? v enh ? [v ] 0.0 ? 50.0 ? 100.0 ? 150.0 ? 200.0 ? 250.0 ? 300.0 ? 350.0 ? 400.0 ? 2.533.544.555.5 circuit ? current: ? icc ? [ua] input ? voltage ? : ? vin ? [v] fi g .20 terminal en h volta g e-tem p erature characteristic fi g .21 circuit current- p ower-su pp l y volta g e characteristic ta = 25 vin = 3.3v vin = 3.3v ta = 25 v fb = 0.83v v fc = 1.0v sw = high ta = 25 vin = 3.3v ta = 25 vin = 3.3v
catalog no.08t276a '08.7 rohm ? ta p e quantit y direction of feed embossed carrier ta p e 2500 p cs e2 (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) htssop-b20 1.0max. 10 1 20 11 0.17 1.0 0.2 0.5 0.15 0.65 s 0.08 + 0.05 ? 0.04 + 0.05 ? 0.03 0.2 6.4 0.2 0.85 0.05 0.08 0.05 4.4 0.1 0.325 6.5 0.1 s reel 1pin 1234 1234 1234 1234 1234 1234 1234 1234 when you order , please order in times the amount of package quantity. direction of feed
notes no technical content pages of this document may be reproduced in any form or transmitted by any means without prior permission of rohm co.,ltd. the contents described herein are subject to change without notice. the specifications for the product described in this document are for reference only. upon actual use, therefore, please request that specifications to be separately delivered. application circuit diagrams and circuit constants contained herein are shown as examples of standard use and operation. please pay careful attention to the peripheral conditions when designing circuits and deciding upon circuit constants in the set. any data, including, but not limited to application circuit diagrams information, described herein are intended only as illustrations of such devices and not as the specifications for such devices. rohm co.,ltd. disclaims any warranty that any use of such devices shall be free from infringement of any third party's intellectual property rights or other proprietary rights, and further, assumes no liability of whatsoever nature in the event of any such infringement, or arising from or connected with or related to the use of such devices. upon the sale of any such devices, other than for buyer's right to use such devices itself, resell or otherwise dispose of the same, no express or implied right or license to practice or commercially exploit any intellectual property rights or other proprietary rights owned or controlled by rohm co., ltd. is granted to any such buyer. products listed in this document are no antiradiation design. appendix1-rev2.0 thank you for your accessing to rohm product informations. more detail product informations and catalogs are available, please contact your nearest sales office. rohm customer support system the americas / europe / asia / japan contact us : webmaster@ rohm.co. jp www.rohm.com copyright ? 2008 rohm co.,ltd. the products listed in this document are designed to be used with ordinary electronic equipment or de vices (such as audio visual equipment, office-automation equipment, communications devices, electrical appliances and electronic toys). should you intend to use these products with equipment or devices which require an extremely high level of reliability and the malfunction of which would directly endanger human life (such as medical instruments, transportation equipment, aerospace machinery, nuclear-reactor controllers, fuel controllers and other safety devices), please be sure to consult with our sales representative in advance. it is our top priority to supply products with the utmost quality and reliability. however, there is always a chance of failure due to unexpected factors. therefore, please take into account the derating characteristics and allow for sufficient safety features, such as extra margin, anti-flammability, and fail-safe measures when designing in order to prevent possible accidents that may result in bodily harm or fire caused by component failure. rohm cannot be held responsible for any damages arising from the use of the products under conditions out of the range of the specifications or due to non-compliance with the notes specified in this catalog. 21 saiin mizosaki- cho, ukyo-ku, kyoto 615-8585, japan tel : +81-75-311-2121 fax : +81-75-315-0172 appendix

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