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how loop delay in charge pump pll will affect its loop stability (Read 3579 times)

rfic New Member Offline Posts: 9 San Diego, CA	how loop delay in charge pump pll will affect its loop stability Jul 13^th, 2015, 9:52pm if i insert a fix loop delay inside CPPLL, how the loop stability suppose to change? for example, my vco has 8 phases, if i choose phase <7> instead of phase <0>, is loop stability same? thanks
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loose-electron Senior Fellow Offline Best Design Tool = Capable Designers Posts: 1638 San Diego California	Re: how loop delay in charge pump pll will affect its loop stability Reply #1 - Jul 16^th, 2015, 4:03pm please clarify your question - a fixed delay on a PLL removes phase margin from the control system, but you mention tapping off of a different connection on a ring oscillator which is something different -
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Re: how loop delay in charge pump pll will affect its loop stability
Reply #2 - Jul 18^th, 2015, 11:41am

loose-electron wrote on Jul 16^th, 2015, 4:03pm:

please clarify your question - a fixed delay on a PLL removes phase margin from the control system, but you mention tapping off of a different connection on a ring oscillator which is something different -

i did mean fix delay, and i think fix delay will degrades PM as well; if this is true, then i expect using phase 7 of ring osc suppose to have less PM compared to using phase 0 of that ring osc as feedback clock -- is this derivation correct?

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loose-electron Senior Fellow Offline Best Design Tool = Capable Designers Posts: 1638 San Diego California	Re: how loop delay in charge pump pll will affect its loop stability Reply #3 - Jul 19^th, 2015, 1:41pm fixed delays can be introduced at several places in a PLL, in some locations it introduces a phase relationship shift and in other places it changes the phase margin define what you are doing
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baohulu Community Member Offline Posts: 43 china	Re: how loop delay in charge pump pll will affect its loop stability Reply #4 - Jul 23^rd, 2015, 11:44pm it seems phase7 and phase8 leave the same phase margin
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