jfyan
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hi fei:
i met the similar thing as you stated, but the outputs (v(up) and v(dn) ) are sensive the some gates's sizes. please check the signal reset and v(ref) and v(vco), whether a missing clock eage is happened. for more information about nonideal linear PFD characteristic, please refer to Mozhgan Mansuri's phd thesis. (she is a phd of UCLA), you also can find her jssc paper in ieee. ps:
who can tell me how can i simulate the dead zone of PFD, and how much dead zone can i ignore, and has no serious effect in jitter characterictic .
thanks advance.
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