IEI CE T RA NS. CO M M UN ., V OL E84- B , N0 .6 JUNE 2001

l 6 8 0

|LETT ERA N ew Char ge Pump PLL wit h Reduced J it t er

~

T he am ount of F ST , SLW node vol t age d r i f t i ncr easesa t he d i Her-- ®ce b et ween t he node and b ias vol t ages

incr eases. C onsequent ly , P L L j i t t er ch ar act er ist ics getw or se a i t s oper at ion fr equency m ov es aw ay fr om t he

cent er f requency .A n ew ch ar ge pu m p st r uct ur e (T y p e H ) t hat m in i-

m izes t he ab ove p r obl em is show n i n F ig . 3 . T h is char gepu m p uses a sel f-b iased m et hod and fun ct ion s a a d iL

fer ent i a,l ch ar ge pum p . I t has cur rent m ir r or s w h ich

est ab l ish cu r r ent pat h 9 f rom p at h @ w h en bot h U Pand D N signals are logic ®1.¯ W hen U P and D N signals

ar e b ot h logic ®O,¯ P M O S and N M O S t r ansist or s are d l

t u r ned OH. T he F ST an d SLH 7 node vol t ages shou ld re-

m ain 6x ed , Ä t her e i s no leakage pat h . A s a r esu l t , t heP L L ou t p ut j i t t er is red uced . W hen U P an d D N sig-n als are bot h logic ®1,¯ w h ich happ ens d u r ing t he P F D

r eset t i m e, a F ST , SLW node volt ages i n b ot h charge

pu m p st r uct u res can d r i f t . H owever , t h is is not a m aj or

S U M M A R Y A n e w c h a r g e p u m p i s p r o p o se d w h i c h p r o v i d e s

ihmm×nm§1m1£W¦ pw¦ rmmow¦ vwÞ ed j i t t e r c h a r a c t e r i s t i c s f o r a p h a e - l o c k e d l o o p ( P L L ) . T h e

P L L w i t h t h e p r o p o s e d c h a r g e p u m p i s i m p l e m e n t e d w i t h 0 .6 P m

C M O S t e c h n o l o g y . T h e m e as u r e d R M S o u t p u t j i t t e r i s a m u c h

Ä 2 8 % s m a l l e r t h a n t h a t o f a P L L w i t h a p re v i o u s l y r e p o r t e d

c h a r g e p u m p s t r u c t u r e .

k e y w o m - : c h a r g e p u m p , p h a s e - l o c k e d l o o p ¥ L í , × e r c h a r -

o c t e r t s t zc s

1 I n t r o d u c t i o n

A char ge pu m p is w idely used in t he ph ase- l ocked loop

(P L L ) for m any ap p l icat ions Ì , Ò . F igu re 1 show s t heb lock d iagr am of t he ch ar ge-p u m p P L L . I d eal ly , t w o

ou t put s of P h Ä e/ D equem y D et ect or (P F D ) shou ld

haq t he sam e logic val ues and t he char ge p um p ou t p u tshou ld b e Hx ed w hen t he P L L is locked . H owever , t h is

does not happ en in real ci rcu i t s as t he char ge pum pcir cu it usual ly hÄ asy m m et r ic feat u res t hat cause t h e

Hud nat ion i n t he Vol t age C on t r ol led O sci l l at or (V C O )cont rol vol t age and P L L ou t pu t p h ase noise. I n or der

t o m ini m ize t h is pr ob lem , a new ch arge p um p st r uct u re1188 beeu pr oposed Ò . T he P L L ci r cu i t t h at ha t hepr oposed ch arge pu m p is real ized and it s j it t er char -ad er ist ics are com par ed w i t h t hose of a p r ev iously r e-poI-- d char ge pum p P L L ¹ .

| N

Design of Phase-Locked Loop2 .

B lock d iag ram for phase- locked loop .F i g . 1

F ig ¤ p 2 show s t he convent ional ch ar ge p um p st r uct ur e(T y pe I ) Þ . W hen ei t her- U P or D N sign al is log ic ®1¯

and £ p ot her is logic ¤0 .® F ST or SLH 7 no de is char ged

and 1l ie ot her node is d ischarged , resp ect ively - T h isIn n-h ips 1lu¤V C 0 cont r o l vo l t age r equ i r ed for P L L opPIn t ion - R Then t he P L L is locked , b ot h U P and D Nsignals-s Hrp logic ¤0 ¯ as t here is no p lm e/ f requency d iL

fu ¤cl lr p bd w een P L L inp u t and ou t pu t - I n t h is cm e±

CHITo n pat hs r ep r esent ed by dot t ed l i nes i n F ig . 2 areest ab l ished and F ST ® SLW nod e vol t ages shou ld r e-m ain ONto - H owever - i f F ST . SLM 7 no de vol t ages d iHer

fr om d w in i t ia l b ias vol t ages, t hey d r i f t b ecause t heO Il-- nt d 1h ¤ing capab i l i t ies of P M 0 S and N M O S t ran-

sid ol-s b ¤i ng in t i le sam e cu 1Tent p at h ar e n ot t he sam e-

M anuscr ipt received A ugust 2, 2000.èT he aut hors are wit h t he D epar t ment of E lect r ical and

Elect ronic Engineer ing, Yonsei Universit y, Seoul , 12* 749,K orea.

11T he aut hor is wi t h Samsung E lect ronics, K orea.

L E T T E R1 6 8 1

2 2( µÍ5¹ m

2 0

1 8 T y p eI nga----2 5

( µÍ5u m

Schemat ic diagram for newly proposed charge puttoF ig . 3(T y pe H ) .

- - - -Type l- - - - Type I I2 08 |

µ | 1£ 2 O4 L - J - - - - - |-¹ ¸ --- - -¦ ¯ lì | |

2 0O ̄ .6 9½ 6 93 6 95

T lM E(u s )

(c )

F ig . 5 T he t r ansient var iat ions of t he cont ro l volt age. (a) T y peI , (b ) T y pe I I , (c ) T he m agn ined wavefor ms.

pr obl em because t he d u r at ion of t he P F D reset t im e is

r elat ively sm al l .T o com p ar e t he p er for m an ce b et ween t he conven-

t ion al ch ar ge pum p (T y p e I ) and t he new ly pr op osed

char ge pum p (T y p e H ) , t w o P L L ci r cu i t s ar e desi gnedeach of w h ich includes T y p e I or T y p e I I ch ar ge p um p .E ach P L L h Ä a convent ional P F D Ò , a fo u r -st age

fr equency d iv i der ( 1/ 16 ) m ade up of fou r dy nam ic D -tH e m p - ps ¹ , and a secon de r-der on -ch ip loop Hl t ¤ -

T he lo op Gl t ¤ par am et er s (R 1 = 5000 O , G = 200 p Fa d Q = 20 p F ) are chosen so t hat t he d am p in g fa -

t or of t h e closed- loop t r an sfer fun ct ion is 0 .707. T h is

cor resp onds t o t he loop b and w id t h of 3 .3 M H z. Fqt he V C 0 , a six -st age d iHer a d i al r ing osci l l at or is used -

E ach r ing osci l lat or st age is com p osed o f a d iga - -Li al N M 0 S p air w it h var iab le r esist ance loads m ade of

P M O S dev i ces op er at ing in t he t r io de r egion . F igur e 4

show s t he SP I C E simu l at ion r esu l t s for V C O ou t p u t at

t he osci l lat ion f requency of 1.03 G H z. F igu r e 5 show st he si m u lat ed t r ansient r esp onses of V C 0 cont r ol vo l t -

ages for t w o P L L ci r cu i t s hav i ng d ig ¤ - m char ge pu m ps(T y p e I , T y pe H ) . For t he simu l at ion , t he in pu t fr e-

quency is 35 7 M H z m d t he locked V C O fr equency is

571 M H z. I t is show n t hat t he P L L w i t h T y p e I I char ge

F i g . 6

pump has smaller volt age var iat ion once it is locked.

Exper iment al Result s3 .

F i g u r e 6 s h o w s m e a s u r e d o u t p u t o f t w o P L L s l o c k e d

w i t h 5 0 M H z i n p u t s i g n a l s . F o r b o t h P L L s , t h e m e a -

s u r e d l o c k i n g r a n g e o f V C O * e q u e m y i s f r o m 5÷ 3â 2 t o

8· 0m 0 bM 1 IH 1 zZ . T h e t o t a l p o w e r c o n s u m p t i o n i n c l u d i n g IU / O

bh¢ tud1dì {H&fìh eaw Irm .s i s a b o u t 1B 3· 0 1nm¼n ½W f o r b o t h Pm ILH ¹J¾ILh ¹Ü¤s¥ . T a b l e 1 sm um nm* ½ç -

rnm1n1 aa rn i®z¼ eÄ S t h e P L L c h a r a c t e r i s t i c s . A s s h o w n i n T a b l e 1 .

T ype H PL L with t he new charge pump st ruct ure showsimproved j i t ter charact er ist ics in t he ent i re * equem y

IEI CE T RA NS. COM M UN -- V O L E84- B , N0 .6 JUNE 20O1

1 6 8 2

Tab le 1 PLL charact erist ics.

ype | TyÚ | |

T e c h n o l o g y O 6-um CM0 S

Supply Vd ¢ e 3 3 V

| Power Consumption | 130 mW

532 - 800 (MHz)LOCKIng Range

| 532MHz

657MHz

800MHz

1 9 03ps

1 1 4 4ps

! 6 9 2ps

1 4 5 9 p s

1 O . 7 1 p s

| 2 1 0 p s

4U t t e r ( r m s )

SOOp¤ / div 4O 53n¤

range and t he improvement is much pronounced at fre-quencies away from t he PLL center frequency Ä ex-

pected . T he j it t er measurement is carr ied out usingTek 11801C digit al sampling osci l loscope by apply ing3.3 V p- p per iodic pulse signals supplied by HP 81101Apulse generator . F igure 7 shows t he measured j it tercharact er ist ics of T ype I (a) and T ype I I (b) PL L at800 M Hz. I t should be not ed t hat t he measured PL Lout put j it t er has a considerable cont r ibut ion from t hesignal source used . T he measured RM S j it t er for t hesignal source alone is 13.8 ps at 41M Hz.

!a) Type I PLL

C o n c l u s i o n4

A new low -j i t t er char ge pum p P L L is r ealized . I n t he

ex per i m ent al resu l t s, t he n ew char ge pu m p P L L has r ed uced j i t t er ch ar act er ist i cs t han t he convent ional st r uc-

t ur e. T his is b ecause t he leakage cu r rent pat hs for t hechar ge pu m p out p ut ar e blocked w hen t he P L L w Älocked . C onseq uent ly , t he char ge p um p ou t p u t vo l t -

ages rem ain st ab le. T he m easur ed P L L R M S j i t t er isÄ m uch a 28% leg t h an t hat of t he P L L w i t h a p rev i -

ously repor t ed ch arge pu m p st r uct ur e. T he new ch argepum p P L L can be usefu l fo r im p lem ent ing h igh-sp eed

and low£ t t er cl ock d at a recover y (C D R ) ci rcui t s-

Fig. 7 PLL output j it ter characterist ics (f w vf vc o = 800MHz).

= 50 MHz,

A c k n o w l e d u n e -m s

T h is wor k w as sup por t ed by t he K or ea R esear ch Fou n-

dat ion . P L L ci rcu i t s were fabr icat ed t hr ough t h e M P W

pr ogr am at I C D esign E ducat ion Cent er ( I D E C ) , K o

r ea .

R e f e r e n c e s

Ì B . Razavi , Monolit hic PhÄ e-Locked Loops and Clock Recovery Circui ts- T heory and Design, IEEE Prs s, 1996.

[2| K hw ani , F . Ssaleh, D. Lee, P R ang, P. Ta, and G. M iller ,°Clock and dat a recovery for 12 5Gb/ s et hernet t ransceiver

i n O3 5 P m C M 0 S ,± P r o c . I E E E 1999 C u st o m I n t eg r a t ed C i r -

c u i t s C o n fer en c e , p p .26 1- 2 6 4 , M ay 199 9 .

Ò M .- S . L ee , T .- S . C h ew . , W .-Y . C h o i , a n d E .e . C h o i , K o

r ea rt P a t en t A p p l i ed , 9S 6 2 13 6 , 19 9 9 .[4 ] S . SM i t-o p a t h s a n d M .A . H o r ow i t z , ° A sem i- d i g i t a l d u a l

d e lay - l o ck ed l o o p ,± I E E E J . So l id - S t a t e C i r c u i t s , v o l .32 ,

n o . 11 , p p . 16 8 3- 169 2 , 19 9 7 .

Ò S .d . K i m , K .- H . L ee , Y .S . M o o n , D .S . h o n g , Y .- H . C h o i -a n d H .- K . L i -n , °u ®W A m * M bw/¥s° /Î pMim n i n t e r fa c e fo r sk ew - t o le r an t

b u s u s i n g low j i t t er P LH ½LLDÂ,c,± I E E E J . So l id - S t a t e C i r cu i t s ,

v o l .3 2 , n o 5 , p p .6 9 16 % , 19 9 7 .¹ M . C o m b s , K . D i m ¤ y , a n d A . G M in er , ° A p o r t a b le c lo ck

m u l t i p l i e r ge n er a t o r usi n g d ig i t a l C M O S st a n d a r d ce l ls,±

I E E E J . So l id - S t a t e C i r c u i t s , v o l .3 1, n o .7 , p p .9 58 - 9 6 5 , 199 6 .