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technical note system power supply for tv series built-in 1ch fet synchronous rectification type dc/dc converters bd8628efv, BD8624EFV description bd8628efv / BD8624EFV have realized the high performance and reliability required as a power supply for thin-screen tv. with built-in fet 1ch current mode control, the dc/dc converte r series has the advantage 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 increas ingly 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 (overcurrent 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 circuit test etc. and henc e most suitable for thin-screen tv which requires the high r eliability. features 1) 1ch synchronous rectification step-down system dc/dc converter 2) soft start, soft off function 3) built-in low voltage / ov ervoltage protection function 4) built-in overcurrent protection function 5) frequency setting by external resistance is available. (rt terminal) 6) protection time setting by external resistance is available. (rset terminal) 7) built-in rt / rset terminal open/short protection function 8) protection control with built-in sequencer 9) built-in adjustment function time of off latch 10) built-in error state detection signal output function 11) built-in tracking function 12) corresponded to protecting bus 13) load current maximum 3a 14) htssop b24 package aug. 2008
2 / 14 electric characteristic (ta=25 , vcc=6.5v, gnd=0v,ctl=6.5v unless otherwise specified.) parameter symbol specification value unit condition min typ max circuit current 1 i q1 - 0 10 a ctl=0v circuit current 2 i q 2 - 3.4 - ma ctl=vcc < error amplifier part > standard voltage vref v re f 0.792 0.8 0.808 v terminal fb and fc terminal short terminal fb input bias current i fbb -1 0 1 a v fb =0.9v terminal fc clamping voltage h v fch 1.8 - - v v fb =0.7v terminal fc clamping voltage l v fcl - - 0.2 v v fb =0.9v terminal fc sink current i fcsink 0.5 - - ma v fb =0.9v, v f c =0.4v terminal fc source current i fcsource - - -70 a v fb =0.7v, v f c =1.6v open loop gain a ver r - 100 - db oscillation frequency f osc 400 500 600 khz when terminal rt 27k ? is connected charging current i ss -3 -2.5 -2 a v ss =1.0v terminal ss threshold voltage v ssth 0.98 1.08 1.18 v v ss volta g e terminal ss clamping voltage v ssclm 2.2 2.4 - v terminal ss standby voltage v ssstb 0.1 0.15 - v v ss volta g e (l h) terminal ss discharge resistance r ss 49 70 91 k ? ctl=0v terminal ss protection circuit start voltage v sspon 1.0 1.1 1.2 v v ss volta g e (l h) terminal ss protection circuit start voltage maximum hysteresis error v sspon_hys 10 100 200 mv v ss voltage < low voltage, over voltage detection part terminal fb low voltage detection voltage v lv p 0.51 0.56 0.61 v v fb volta g e terminal fb overvoltage detection voltage v ov p 0.86 0.96 1.06 v v fb volta g e < over current detection part output current limitation threshold i lm t vcc-0.9 vcc-0.7 vcc-0.5 v v sw volta g e upper side mos on resistance r onu - 110 - m v boot v sw =5v lower side mos on resistance r o nl - 110 - m v vreg 5 =5v 3 / 14 permissible loss this package is a product of whi ch the feature is the high heat radiation, and connect the back to gnd based on recommended land pattern when you mount. permissible loss pd [w] rohm standard substrate specification material 4 layer glass epoxy substrat e(back copper foil70mm70mm) size 70mm70mm1.6mmt (sarmalbiaing is i n the substrate.) figure 1 heat decrease curve these values are the actual measurement values, and no guarant ee values. jc [ /w] j a [ /w] t stgmin [ ] t stgma x [ ] t a min [ ] t a ma x [ ] t cma x [ =? ] t j ma x 19.0 31.3 -50.0 150.0 -45.0 85.0 150.0 150.0 destruction temperature [ =? ] destruction temperature
4 / 14 block diagram seq control vref ovp lvp osc driver control 17 protect bus i/f rt open/short ctl 10 time vcc rt rset pdet pio ctl sw sw pgnd pgnd test1 test2 pvcc pvcc boot vreg5 fc fb ss gnd 18 19 osc osc vreg5 n.c. n.c. n.c. n.c. figure-2 block diagram ? application diagram terminal explanation no. symbol description no. symbol description 1 pgnd power gnd terminal 13 rt frequency adjustment resistance connection terminal 2 pgnd power gnd terminal 14 rset off latch effective time adjustment resistance terminal 3 n.c. no wire connection. (connect to gnd. ) 15 error state notification terminal 4 n.c no wire connection. (connect to gnd. ) 16 p error state notification and external ic error detection terminal 5 sw sw terminal 17 ctl enable input 6 sw sw terminal 18 vcc vcc power supply terminal 7 boot high side power mos gate drive power source terminal 19 pvcc power vcc terminal 8 vreg5 internal power supply (5.0v) output terminal 20 pvcc power vcc terminal 9 gnd gnd 21 test2 test terminal (connect to gnd. ) 10 fc phase amends terminal 22 test1 test terminal (connect to gnd. ) 11 fb feedback terminal 23 n.c. no wire connection. (connect to gnd. ) 12 ss soft start adjustment capacity connection terminal 24 n.c. no wire connection. (connect to gnd. ) please give to vcc+0.3v as an o peration condition in all input terminals except the terminal boot. however, please do not exceed the absolute maximum rating as vc c=pvcc. table 1 terminal explanation
5 / 14 terminal equivalent circuit chart terminal no. terminal name explanation terminal equivalent circuit chart 1 pgnd power gnd (the same potential as the gnd terminal) 2 pgnd power gnd (the same potential as the gnd terminal) 5 sw sw terminal 6 sw sw terminal 7 boot high side power mos gate drive power source terminal 8 vreg5 internal power supply (5.0v) output terminal 9 gnd gnd 10 fc phase amends terminal pvcc pvcc pgnd vreg5 pgnd
6 / 14 terminal no. terminal name explanation terminal equivalent circuit chart 11 fb voltage detection terminal 12 ss soft start adjustment capacity connection terminal 13 rt frequency adjustment resistance connection terminal 14 rset off latch effective time adjustment resistance terminal 15 pdet error state notification terminal vcc gnd ? vcc
7 / 14 terminal no. terminal name explanation terminal equivalent circuit chart 16 pio error state notification and external ic error detection terminal 17 ctl enable input 21 test2 test terminal (connect to gnd. ) 22 test1 test terminal (connect to gnd. ) 19 pvcc power vcc terminal 20 pvcc power vcc terminal
8 / 14 operation description on/off control dc/dc converter on/off function dc/dc converter controller can be controlled on/off by ctl terminal. analog circuit starts operation at on control (on mode), and goes down to setting output voltage. analog circuit should be standby at off control (off mode), and output voltage becomes 0v. table1 dc/dc converter on/off function c tl terminal voltage >vihctl on control 9 / 14 osc oscillation frequency setting function sw output oscillation frequency of dc/dc converter can be set by installing resistance between rt terminal and gnd externally. figure 3 terminal rt resistance-oscillation frequency range of terminal rt connection resistance setting 23k ? Q rrt Q 135k ? 100khz Q fosc Q 600khz 1 0 10 0 100 0 1000 0 11 0 10 0 100 0 rt terminal resistance[k] switching frequency [khz] *reference date
10 / 14 protect bus input/output function the terminal pio is protect bus input/output terminal. the term inal pio is hi-z when dc/dc usually operates. when the terminal pio becomes low by connecting protect bus, dc/dc is tu rned off. afterwar ds, when the terminal pio becomes high, it reactivates. dc/dc is off latch when dc/dc e rror detects it and the terminal pdet becomes low. table2 pio terminal, pdet terminal output function dc/dc error detection pio terminal pdet terminal dc/dc undetection hi-z hi-z on undetection low hi-z off detection low low off latch protect bus timing chart if two or more bd 8628efv/bd8633efv/bd8624fv/bd8630fv is connect ed in protect bus, and it uses at the same time, when one ic error detects, all re maining ic becomes pio = low a t the same time, and the output is turned off. protecting bus part timing chart ic_a pdet ic_a pio high off latch when two or more bd8628efv/bd8633efv/bd8624fv/bd8630fv is used at the same time, if one ic error detects, all ic becomes dc/dc off at the same time. ic_b pio dc/dc off ic_b pdet ic_a detects error. ic_b vo high high high low low low 0v pio ic_a pio ic_b
11 / 14 protection function protection circuit is effective for destruction prevention due to accident so that avoid using by continuous protection operation. low voltage protection function(lvp) low voltage protection function detects set output voltage v o from fb terminal and off-latched dc/dc converter compared to internal reference level. low voltage protection function operates when fb terminal voltage falls below v lvp (=0.7 vref) and continues more than set time in external resistance. table 4 low voltage protection function ctl terminal ss terminal fb terminal low voltage protection function low voltage protection operation >v ihctl >1.1v(typ) v lvp +v lvp_hys off <1.0v(typ) - disable off v ihctl >1.1v(typ) >v ovp enable on 12 / 14 overcurrent protection function (ocp) overcurrent protection function compared drain voltage (lx te rminal voltage) with internal ocp terminal voltage when internal nch power mos is on. when lx terminal voltage becomes lower than ocp terminal voltage, external mos would be off. off latch by overcurrent protection function operates when lx terminal voltage falls below ocp terminal voltage and continues more than set time in external resistance. table 6 overcurrent protection function ctl terminal ss terminal output current overcurrent protection function overcurrent protection operation >v ihctl >1.1v(typ) >i lmt enable on 13 / 14 soft start time-out function dc/dc converter off-latch-controls when v ss does not exceed v sspon from v ss > v ssstb +v ssstb_hys after 50msec (typ) passed from soft start. figure 5-3. at soft start time-out error detection (off latch) release method dc/dc converter becomes off latch condition when protecti on function operates. off latch can be released by the following method. dc/dc converter controller of each ch becomes able to do on control transition by releasing off latch. 1. set all ch ctl terminal voltage as < v ilctl and continue that condition about more than 200usec (typ). 2. drop down power supply vcc to below 2.7v(typ). error detection time set function time from the error detection to the off latch can be set by putting resistance outside between gnd and rset terminal. sec] u [ rrset . ? ? ? ? 3 10 8 1 offlatch t rset setting range 10k ? Q rset Q 75k ? 18usec Q tofflach Q 135usec
14 / 14 catalog no.08t277a '08.8 rohm ? ta p e quantit y direction of feed embossed carrier ta p e 2000 p cs e2 (the direction is the 1pin of product is at the upper left when you hold reel on the left hand and y ou p ull out the ta p e on the ri g ht hand ) htssop-b2 4 unit:mm ) 12 13 24 1 0.08 m 0.08 s + 0.05 + 6 ? 4 ? 0.03 + 0.05 ? 0.04 7.6 0.2 1.0max. 7.8 0.1 4 0.17 0.65 0.2 0.325 0.53 0.15 0.85 0.05 0.08 0.05 1 0.2 5.6 0.1 when you order , please order in times the amount of package quantity. reel 1pin 1234 1234 1234 1234 1234 1234 1234 1234 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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