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| technical note system power supply for tv series built-in 1ch fet synchronous rectification type dc/dc converters BD8627EFV description BD8627EFV 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) high efficiency in all load area 2) 3.0a output current 3) low rds(on) internal switches (pchmos:85m ? , nchmos:65m ? ) 4) 1% reference voltage accuracy 5) programmable frequency : 250khz-1mhz 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) htssop-b20 package aug. 2008
2 / 12 absolute maximum rating ta = 2 5 parameter symbol limits unit input supply voltage v in 7 v input terminal voltage v inp *1 v in v output terminal voltage v out *2 v in v output current i out 4 a power dissipation pd 3.2 3 operating temperature to p r -10 85 storage temperature tstg -55 150 1 v inp application terminal en, ss/delay, test, fb 2 v out application terminal sw, pdet, fc, rt, reg 3 (70mm70mm, thickness 1.6mm, and four layer glass epoxy substrates) when mounting substrate and the package back exposure part are connected with solder. operating at higher than ta=25 , 25.6mw shall be reduced per 1 operation condition parameter symbol min typ max unit input supply voltage v in 4.5 - 6.0 output current i out - - 3.0 a 3 / 12 electrical characteristic (unless otherwise noted ta=25 , v in =5.6v) parameter symbol specification value unit condition min typ max vin supply current (operating) i q _ active - 1.3 2.0 ma v fb = 0.83v, v fc = 1v vin supply current (standby) i q _ stb y - 350 700 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 1 - - ma v pdet < 0.5v oscillation frequency f os c 500 550 600 khz r osc = 220k pch fet on resistance r pfet - 85 120 m i sw = 1a nch fet on resistance r nfet - 65 100 m i sw = -1a uvlo voltage v uvl o 3.8 4.0 4.2 v sw leak current i lsw - 0 1 a v en = 0v, v in = 6v en terminal h threshold voltage v enh 2.0 - - v en terminal l threshold voltage v enl - - 0.5 v ss/delay terminal source current i sss o 2 4 6 a 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. permissible loss 0 25 50 75 100 125 150 1 2 3 4 0 (70mm70mm, thickness 1.6mm, and four layer glass epoxy substra tes) when mounting substrate and the package back exposure part are connected with solder. surrounding temperature ta [] permissible loss pd [w] fig. 1 heat decrease curve 4 / 12 block diagram fig.2 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 reset output 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 internal regulator 16 en enable input on/off control for device operation 17 test test terminal gnd short in application 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 5 / 12 pin equivalence circuit diagram no. symbol explanation terminal equivalent circuit diagram 1 sgnd gnd (connected 0v) 2 fb output voltage detection terminal 3 pdet off latch signal output 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 6 / 12 no. symbol explanation terminal equivalent circuit diagram 15 reg internal regulator output terminal 16 en enable terminal 7 / 12 no. symbol explanation terminal equivalent circuit diagram 18 ss soft start time adjustment terminal 19 fc error amplifier compensation terminal 20 rt oscillator frequency adjustment terminal 18 vin sgnd 20 vin sgnd 8 / 12 o o p p e e r r a a t t i i o o n n d d e e s s c c r r i i p p t t i i o o n n enable control the device can be controlled on/off by en terminal (16 pin) voltage. an internal circuit starts when ven reaches 0.65v. fig. 3 on/off transition wave form in en controlling soft start time set function as for BD8627EFV, 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. 9 / 12 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 and the oscillation frequency follows fig.4. 10 100 1000 10000 10 100 1000 10000 rt??[k] ??[khz] fig. 4 rt resistance-oscillation frequency rt terminal resistance [k ? ] frequency [khz] 10 / 12 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 ihen >1.4v(typ) 12 / 12 catalog no.08t275a '08.8 rohm ? 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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