Power Bus Decoupling Algorithm

Transcription

1 Rev Power Bus Decoulig Algorihm Purose o Algorihm o esimae he magiude o he oise volage o he ower bus es. Descriio o Algorihm his algorihm is alied oly o digial ower bus es. or each digial ower bus e, decoulig caaciors are ideiied he he oise volage is calculaed based o he eecive imedace o he decoulig caaciors ad he rasie curre o he e. his algorihm cosiss o several ucios. he ucio LocaeDecouligCaaciore ideiies all he decoulig caaciors o he ower bus. CalculaeSeriesducacecaacior calculaes he coecio iducace, L, o each decoulig caacior. he oal eecive caaciace, C e, o a e is calculaed usig he caaciace o he decoulig caaciors ogeher wih coecio iducaces ad he ierlae caaciace, C o. he rasie curre,, draw rom he ower bus by each e is deermied usig he ucio EsimaerasieCurree. ially, he rasie eak oise volage iduced o he ower bus by each e is calculaed usig C e ad. he ucios meioed above are described i ollowig secios. deiicaio o decoulig caaciors Subrouie: LocaeDecouligCaaciore. Reurs a lag idicaig wheher or o decoulig caaciors are rovided o he e ad sores he ames o available decoulig caaciors. or each digial ower e, he subrouie ideiies he caaciors coeced bewee he e ad groud. Decoulig caaciors wih a value larger ha 00 are igored, sice he arasiic iducace o hese caaciors eds o reve hem rom beig eecive a high requecies. here is a leas oe caacior wih a value less ha 00 available, he ames o he available caaciors are sored ad a lag is se o. Oherwise, he lag is se o 0. Calculaio o Series ducace Subrouie: CalculaeSeriesducacee. Calculaes ad sores he series iducace associaed he races ha coec decoulig caaciors. he coecio iducace associaed wih decoulig caaciors lays a imora role a high requecies. his subrouie calculaes he iducace due o races ha coec he caacior bewee a ower e ad groud. igure illusraes yical layous or coecig a decoulig caacior. igure. yical geomery o races or coecig ower bus decoulig caaciors he series iducace corresodig o he races is calculaed usig he ollowig equaio. d d [ l h/ w ] [ ] L 00 H

2 Rev where, h is he heigh o he races above he reerece lae. he arial iducace associaed wih he vias, solder ads ad ESL o he caacior is aroximaed as H, which is he secod erm i Equaio. he subrouie sores he calculaed series iducace or each caacior o he e. Calculaio o oal Eecive Bus Caaciace Subrouie: CalculaeoalEeciveBusCaaciore. Reur he value o he eecive decoulig caaciace a each requecy. geeral, ower bus coulig is accomlished by mulile caaciors or a e. igure shows a equivale circui model o a yical ower bus. igure. Equivale circui model o a ower bus he oal caaciace o he circui show i igure is oud by he sum o he ierlae caaciace, C o, ad all he decoulig caaciaces, C i, i arallel. he eecive caaciace o each decoulig caacior chages wih requecy due o he series iducace ad is calculaed as [] Ci LiCi, Ci C e, i mi he eecive caaciace o a decoulig caacior is much smaller ha he ierlae caaciace ie, C e, i < C o /0, he caacior is igored ad sored i a lis o ieecive caaciors. or a give e, his subrouie reurs he sum o all he eecive caaciaces lus he ierlae caaciace or all he requecy blocks ad arrowbad requecies. Esimaio o rasie Curre Subrouie: EsimaerasieCurree. Esimaes he rasie curre draw rom he ower bus by each C ad he rasiio imes a risig ad allig edges. igure illusraes a yical coiguraio o a C ad he corresodig rasie ower-bus curre ad ouu sigal volage waveorms. he rasie curre is deermied by he logic amily o he device. igure 3. yical rasie ower-bus curre ad ouu volage waveorms he device is L, he ollowig se o equaios is used.

3 Rev Vcc V N R / 5 RC L R0 6 where, N is he umber o ouus ad is he rasiio ime. C L is se o is yical value, 0, or coveiece. Oher arameers are deermied by he ye o he device ad show i able. able. Deaul criical arameers or rasie curre calculaio L amily CMOS amily LS R 0 Ω, V 0.6 V, 6 s MG gore oo slow ALS R 40 Ω, V.0 V, 3 s HC AB R 40 Ω, V.0 V, 3 s AC AS R 35 Ω, V 0.6 V, s LVC ad LCX C PD 50 Swichig ime 4 s CCD 0.3 ma/mhz Swichig ime s C PD 50 Swichig ime 3 s he device is CMOS, he rasie curre draw by he ower bus is he sum o he quiesce curre, he curre associaed wih ius, hrough curre he curre draw whe boh rasisors i he ouu sages are swichig ad he ouu curre. he magiude o he curre associaed wih quiesce ad iu ors are much smaller ha hose o hrough curre ad ouu curres. hereore oly hrough curre ad ouu curre are cosidered i his algorihm. he magiude o hrough curre ca be calculaed usig a equivale ower dissiaio caaciace C PD [] or dyamic ower suly curre CCD [µa/mhz]. Cosiderig he eecs o boh curres, he oal rasie curre draw rom he ower bus ad oher arameers are calculaed usig ollowig equaios. CPD N CL whe CPD 7 N CL CCD whe CCD CPD whe CPD 8 CCD whe CCD / 9

4 Rev N CL whe CPD C PD 0 N CL whe CCD CCD he arameers are deermied by deaul values give i able uless oherwise seciied i he ersoaliy ile. Calculaio o Peak Volage Chage i Power Bus Subrouie: CalculaerasiePeakVolagee. Calculaes he magiude o volage chage i ower bus due o rasie curre draw by Cs rom decoulig caaciors. he curre draw by a C creaes a volage chage i he ower bus e o which he C is coeced. he maximum volage chage is deermied by he C ha has he larges value o. he rae o chage o volage across a caacior is deermied o oly by caaciace value bu also by he value o he coecio iducace. his eec ca be ake io accou by deiig a eecive caaciace ha is ime deede. V C C where, C C o m i Ci LiC i / C C o m i Ci LiC i / where, m is he umber o decoulig caaciors o he ower bus e, C o is ierlae caaciace, ad C i ad L i are he decoulig caaciace ad he series iducace o i-h decoulig caacior, resecively. Reer o Aedix or more deails abou he ime-deede ower bus caaciace. Secrum o Narrowbad Power Bus Volage Noise Subrouie: NarrowbadVolageComoee. Calculaes he amliude o harmoics o he ower bus volage oise due o rasie curre draw rom Cs. he secrum o he ower bus oise volage ca be obaied rom he ourier series exasio o he curre waveorm show i igure 3b ogeher wih oal eecive bus caaciace, C e, which is deermied by he subrouie CalculaeoalEeciveBusCaaciacee. V C e where, o ad is -h harmoic o rasie curre draw rom he ower bus. Reer Aedix or deailed exressios or.

5 Assumios Oly digial comoes are cosidered. Board resoaces are o accoued or. Caaciors wih values larger ha 00 are egleced. A ower ad groud es are assumed o be laes. Oly surace moued caaciors are cosidered. Rev Reereces [] S. Radu, R. E. DuBro,. Hubig ad. Va Dore,, Desigig Power Bus Decoulig or CMOS Devices, Proceedigs o he 998 EEE eraioal Symosium o Elecromageic Comaibiliy, Dever, CO, Augus, 998,

6 Aedix. ime-deede Power Bus Caaciace Rev Cosider a L-C series circui as show i igure a., where he curre draw rom he caacior icreases liearly wih ime. he caacior is charged o V o a ime 0. igure a.. Volage variaio o L-C series circui he diereial equaio ha govers he circui is di V L i d Vo d C 0 a. Le s cosider he volage variaio or a shor ime eriod << LC. he, equaio a. ca be aroximaed as ollow. i V L i V o a. C By rearragig he equaio a. ad iroducig he eecive caaciace C e, he volage variaio durig is wrie as ollow. L Q i V V V 0 i C a.3 C e C e urher rearragig yields ime deede eecive caaciace. C C e a.4 LC he equaio a.3 ad a.4 rovides he easy way o esimae volage variaio due o riagular rasie curre. Cosider he riagular curre ulse show i igure a. he volage chage due o he curre ca be easily calculaed as i i V V V a.5 C C e e igure a.. riagular curre ulse ad corresodig volage variaio

7 Rev Aedix. ime Harmoics o he rasie Curre he secrum o he rasie curre ca be obaied rom he ourier series exasio o he curre waveorm show i igure 3b. he amliudes are give as b a a.6 where, si si si si si si a si si cos si cos si cos si b e e arca arca si si cos cos