Analysis of Current Starved Voltage Controlled Oscillator using 45nm CMOS Technology

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Ernest Sparks
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1 SSN (Pri) : SSN (Olie): eraioal Joural of Advaced Research i Elecrical, Elecroics ad srumeaio Egieerig (A SO 397: 007 erified Orgaizaio) ol. 3, ssue 3, March 014 Aalysis of urre Sarved olage orolled Oscillaor usig 45m MOS Techology Aike Prajaai 1, P.P.Prajaai PG Sude (ME-SE), e. of EE,.. ollege of Egieerig, Ahmedabad, Gujara, dia 1 Assisa rofessor, e. of EE,.. ollege of Egieerig, Ahmedabad, Gujara, dia ABSTRAT: A oscillaor is a elecroic device ha used for he aim of geeraig a sigal or waveform. Alicaios vary from clock geeraio i microrocessors o carrier syhesis i cellular elehoes, requirig vasly differe oscillaors, oscillaors oologies ad erformace arameers. O ca be buil usig may circui echiques. This aer deals wih he desig ad imlemeaio of urre Sarved volage corolled oscillaors (SO) usig 45m MOS echology. MOS circuiry i S dissiaes less ower whe saic, ad is deser ha oher imlemeaios havig same fucioaliy. A O is a oscillaor, where he corol volage corols he oscillaor ouu frequecy. The simulaio of SO is doe i T-Sice. KEYWORS: MOS O, urre-sarved O,T SPE.NTROUTON A volage corolled oscillaor (O) is oe of he mos imora basic buildig blocks i aalog ad digial circuis. a wireless sysem he qualiy of he commuicaio lik is deermied i large ar by he characerisics of he O ad i oday s wireless commuicaio sysems greaer frequecy rage is required by he Os. Tradiioally, Os usig MOS echology have bee used for low frequecy alicaios, bu submicro rocesses have allowed MOS oscillaors o achieve frequecies i he gigaherz rage []. This rage is made ossible wih he use of auomaic swig corol. O ca be buil usig may circui echiques [5]. his aer desigig of MOS O usig T sice here curre sarved O is desig. Though here are so may desig requiremes of a O, which are hase sabiliy, large elecrical uig rage, lieariy of frequecy verses corol volage, large gai facor, caabiliy of acceig widebad modulaio ad low cos bu he mos imora facor i desigig he O is he lieariy, o he basis of which he comariso bewee MOS Os is described [6]. Wih resec o digial hoes ha use hese circuis, low ower cosumio, small size ad low fabricaio coss are imora desig facors.. URRENT STARE O A rig oscillaor is comrised of a umber of delay sages, wih he ouu of he las sage fed back o he iu of he firs. To achieve oscillaio, he rig mus rovide a hase shif of π ad have uiy volage gai a he oscillaio frequecy. This curre sarved O is desiged usig rig oscillaor ad is oeraio is also similar o ha. From he schemaic circui show i he Figure 1, i is observed ha MOSFETs M ad M3 oerae as a iverer, while MOSFETs M1 ad M4 oerae as curre sources. The curre sources, M1 ad M4, limi he curre available o he iverer, M ad M3; i oher words, he iverer is sarved for he curre. The MOSFETs M5 ad M6 drai curres are he same ad are se by iu corol volage. The curres i M5 ad M6 are mirrored i each iverer/curre source sage. The uer PMOS rasisors are coeced o he gae of M6 ad source volage is alied o he gaes of all lower NMOS rasisors [4]. oyrigh o JAREEE

2 SSN (Pri) : SSN (Olie): eraioal Joural of Advaced Research i Elecrical, Elecroics ad srumeaio Egieerig (A SO 397: 007 erified Orgaizaio) ol. 3, ssue 3, March 014 Fig 1. urre-sarved O. AUATNG ASPET RATO The drai curre of a shor chael MOSFET oeraig i sauraio regio is give by: = W v (, ) From his equaio we ca wrie he equaio for he widh of NMOS, which is give by: W = Now, BSM4 MOSFET model Parameers are: [ (,)] Shor-hael MOSFET arameers =1 ad a scale facor of 45m Parameer NMOS PMOS Bias urre, 10µA 10µA S,sa ad 50 m 50 m S,sa GS ad SG 350 m 350 m THN ad 80 m 80 m THP vsa ad vsa m/s m/s Tox 14Å 14Å ox 5 f F/µm 5 f F/µm Table 1. Shor-hael MOSFET arameers By uig he values of hese arameers i he equaio of W, we ge he value W i 45m echology, which is give by: W = 180m For he Raio of W/, (W/) =.5(W/) Now, we kow ha he values of for NMOS ad PMOS are same i 45 m echology, so we ge = = 45m oyrigh o JAREEE

3 SSN (Pri) : SSN (Olie): eraioal Joural of Advaced Research i Elecrical, Elecroics ad srumeaio Egieerig (A SO 397: 007 erified Orgaizaio) ol. 3, ssue 3, March 014 So, he raio will be W =.5W By uig he values of W i above equaio, we ge W = 450m Fially we ge he raio of W/ for NMOS & PMOS i 45m echology: For NMOS: W = 180m, = 45m. For PMOS: W = 450m, = 45m. ESGN OF O To deermie he desig equaios for use wih he curre-sarved O, he oal caaciace o he drais of M ad M3 is give by o o u i ' 3 ' o ox ( W W ) ox ( W W ) (1) This is simly he ouu ad iu caaciaces of he iverer. The equaio ca be wrie i more useful form as 5 ' o x ( W W ) () The ime i akes o charge from zero o S P wih he cosa curre 4 is give by S P (3) While he ime i akes o discharge o from o SP is give by 1 (4) f 4 = 1 = (which is labelled as ce er whe i O = /), he he sum of 1 ad is simly 1.. (5) The oscillaio frequecy of he curre sarved O for N (a odd umber >= 5) of sages is The cere frequecy (f cere) of he O whe curres, whe i O < T H N. Therefore, m i The maximum O oscillaio frequecy, frequecy, m a x =. f o s c S P 1 1 N ( ) N f 1.. (6) m ax = T H N = c e e r ad f m i. The O sos oscillaig, eglecig sub-hreshold = 0., is deermied by fidig whe i O =. A he maximum The ouu of he curre sarved O ormally has is ouu buffered hrough oe or wo iverers. Aachig a large load caaciace o he ouu of he O ca sigificaly affec he oscillaio frequecy or lower he gai of he oscillaor eough o kill oscillaios alogeher. The average curre draw by he O is N N f T a v g o s c. (7) Or a v g.. (8) The average ower dissiaed by he O is Pa v g a v g (9) oyrigh o JAREEE

4 SSN (Pri) : SSN (Olie): eraioal Joural of Advaced Research i Elecrical, Elecroics ad srumeaio Egieerig (A SO 397: 007 erified Orgaizaio) ol. 3, ssue 3, March 014 f he ower dissiaed by he mirror MOSFETs, M5 ad M6, is also icluded he he ower is doubled from ha give by he equaio (9), assumig ha 5 6. For low ower dissiaio should be ke low, or i oher words oscillaio frequecy should be low [4]. We begi by calculaig he oal caaciace o. Usig equaio ad assumig he iverers, M ad M3, are sized for equal drive, ha is, = = 1, W = 10 ad W =0, he caaciace is = 5 ff 5 µm ( ) (0.045 µm ) = 1.77fF e s use a cere drai curre of 10µA based o - GS characerisics of he MOSFETs. The selecio of he curre is imora because whe io is /, he oscillaio frequecy o be 1GHz. The oscillaio frequecy of he curre-sarved O for N of sages is give by [] fosc = N Where, = 3= 4 N is he umber of sages o is he oal caaciace dd is he suly volage The umber of sages, usig equaio, is give by N = fosc = 10 µa fF 1GH So he umber of he desig sage is 5.. SMUATON RESUT OF URRENT STARE O Fucioal simulaio Of urre Sarved O is doe T-Sice sofware usig 45 m MOS echology. The five sage SO imlemeaio is show i figure.there are wo umber of buffers.the uig rage of O is from 8Mhz o 7346Mhz.The simulaio resul of curre sarved O of 5 sage is show 3. Fig. mlimeaio of SO. oyrigh o JAREEE

SSN (Pri) : 30 3765 SSN (Olie): 78 8875 eraioal Joural of Advaced Research i Elecrical, Elecroics ad srumeaio Egieerig (A SO 397: 007 erified Orgaizaio) ol. 3, ssue 3, March 014 Fig 3.

5 SSN (Pri) : SSN (Olie): eraioal Joural of Advaced Research i Elecrical, Elecroics ad srumeaio Egieerig (A SO 397: 007 erified Orgaizaio) ol. 3, ssue 3, March 014 Fig 3. Ouu Waveform of urre Sarved O Whe we aly corol volage of 0.4v he we ge ouu waveform of ceral frequecy 1Ghz sow i fig 3.Similarly for differe corol volage we ge differe oscillaio frequecy rage from 8 MHz o 7346 MHz is show i able. orol volage i ols Oscillaio frequecy i MHz orol volage i ols.onuson Oscillaio frequecy i MHz Table. Tuig rage of SO his aer we observed ha i curre sarved volage corolled oscillaor (O) geeraes 1GHz frequecy a iu corol volage (io) of 40m. Sice Phase locked loo (P) is widely used i wireless commuicaio sysems, hece we ca geerae ay desire frequecy based o alicaio requiremes.the comaraive aalysis of csvco wih he referece aer is show. Parameer Secificaio Referece[8] (This work) Techology 45 m 100 m (MOS) eer 1 GHz 1 GHz Frequecy Gai (K O ) 3.93 GHz/ GHz/ Tuig rage 8 MHz o 7.34 No meioed GHz Power issiaio μw Μw oyrigh o JAREEE

6 SSN (Pri) : SSN (Olie): eraioal Joural of Advaced Research i Elecrical, Elecroics ad srumeaio Egieerig (A SO 397: 007 erified Orgaizaio) ol. 3, ssue 3, March 014 REFERENES [1] B. Razavi, Moolihic hase-locked loos ad clock recovery circuis- heory ad desig, EEE Press, ad , [] M. Bau, MOS oscillaors wih muli-decade uig rage ad gigaherz maximum seed, EEE Joural of Solid-Sae ircuis, vol. 3, , ecember [3]. A. Hodges ad H.G. Jackso, Aalysis ad desig of igial egraed ircuis,d ediio, McGraw-Hill, [4] R. Jacob Baker, Harry W. i ad avid E. Boyce, MOS ircui esig, ayou ad Simulaio, EEE Press Series o Microelecroics Sysems, ad , 000. [5] M. Jamal ee, Ulra ow-olage ow-power olage orolled Oscillaor, Elecrical ad omuer Egieerig earme, R 6 McMaser Uiversiy, Hamilo, ON, aada 8S 4K1. [6] M. J. Uderhill, Fudameals of oscillaor erformace, Elecroics ad ommuicaio Egieerig Joural, vol. 4, o. 4, , 199. [7] Paul R. Gray ad Rober G. Meyer, Aalysis ad esig of Aalog egraed ircuis, 3rd ediio, Joh Wiley, Jauary [8] B. P. Pada,. K. Rou, d. P. Acharya ad g. Pada esig of a ovel curre sarved O via cosraied geomeric rogrammig aril ieraioal symosium o devices mems iellige sysems commuicaios 011. oyrigh o JAREEE

Field-Effect Transistors (FETs) 3.4 The p-channel MOSFET & COMS

Field-Effect Transistors (FETs) 3.4 The p-channel MOSFET & COMS Field-Effec Trasisors (FETs 3.4 The p-chael MOSFET & COMS A p-chael ehaceme-ype MOSFET is fabricaed o a -ype subsrae wih p+ regios for he drai ad source, ad has holes as charge carriers. The deice operaes