Magnus wrote:
A bit of hysteresis can help to avoid flipping back, but considering the type of signal, it passes the mid-point (0 V) at highest slew-rate, so there is very little risk of flipping back and fourth in the first place, so hysteresis may not even be needed.
A 1 Vrms, 10MHz sine wave has a zero-cross slew rate of 88v/uS (88mV/nS). One would think that would be enough to avoid indecision in a comparator with 5-10nS of propagation delay. However, the LT1016 (10nS) is prone to jitter problems when operating as a ZCD with such a signal, and external hysteresis does not help much because it is delayed by 10nS. (The problem appears to be that the front end has some indecision at this input slew rate that happens faster than the propagation delay to the output -- but this is just an inference because the internal nodes are not accessible for measurement.) For this application, the small amount of internal hysteresis of the LT1719 and LT1720 is very beneficial.
Best regards, Charles _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
