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回復 #1 option318 的帖子
回復 #1 option318 的帖子* U+ j2 N# t! t0 t. F0 h
(1) 首先 open loop gain(迴路頻寬K )must <= pfd之比較頻率之十分之一
; e/ q( ~, V0 w2 Y% N/ ?否則(指>pfd之比較頻率之十分之一)要用Z domain 去分析charge pump6 P; C! B/ t/ C( [5 T- C2 n8 s
pll ,且亦有unstability issue. o7 _* D6 a' T; C
(see Charge-pump phase lock loops paper by Gardner
G0 x% c9 e0 u: dIEEE Trans.Comm,vol Com-28,pp1849-1858,November 1980)
9 U' J" G4 v' c4 v9 r. _(2) loop BW is related to jitter (or phase noise) ,and locking time; @; j& `" _' k* [$ e2 M+ R% w2 X
so you have to consider loop BW from jitter & locking time spec
# d0 X1 u/ a/ k& D' J/ L, s(3)phase margin is decided by relation ship among zero freq ,loop unity gain freq , pole freq6 G+ M# K& e, L1 E3 q4 U
(4) In my opinion ,gain margin is not considered in pll design |
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