Hi Gee, LVDS what an unusual approach :)....
It would be nice if these instruments had a balanced input. Common mode noise is indeed an issue in a lot of cases. Of course wrapping the coax headed to the counter 10X around a fairly large core can help things a bit. Bob On Feb 27, 2010, at 9:32 PM, Bruce Griffiths wrote: > If one is feeling paranoid about ground loop noise (and wishes to avoid > transformers, optoisolators , or fibre optics), etc one could always use an > LVDS driver with a batter powered(?) LVDS to CMOS receiver/translator right > at the 5370A/B input BNC connector. > This may be useful for a DMTD system that uses a 5370A/B. > > Bruce > > Bob Camp wrote: >> Hi >> >> AC cmos will easily drive an L pad to match a 50 ohm cable at these levels. >> That's true at either 3.3 or at 5.0 volts. There are a lot of cmos families >> out there that beat AC for speed and match the output drive capability. >> >> Bob >> >> >> On Feb 27, 2010, at 9:12 PM, Bruce Griffiths wrote: >> >> >>> 1) One method with 5V CMOS is to add a resistive voltage divider at the >>> CMOS driver output with a 50 ohm output impedance at the tap that drives >>> the 5370A/B input. >>> >>> 2) If one has a 5V 50 ohm driver (eg Thunderbolt PPS output) use a 50 ohm >>> attenuator at the 5370A/B input. >>> For a 5370A an attenuation of at least 11dB is required. >>> For a 5370B an attenuation of at least 3dB is required. >>> >>> 3) One can always use the 10x input attenuation setting built in to the >>> 5370A/B however this reduces the signal swing to 0.5V at the trigger >>> amplifier input (5V CMOS input). >>> >>> 4) Attenuate the output of the logic signal by a factor of 2 and use an npn >>> emitter follower to drive the 50 ohm load. >>> >>> 5) Use 3.3V CMOS signal levels for the 5370B. >>> >>> 6) Use a current mode emitter or source coupled switch to drive the 5370A/B >>> input. >>> >>> The switching jitter of the above drivers will be much lower than the >>> internal noise of the 5370A/B as long as HCMOS or faster logic is employed. >>> >>> Bruce >>> >>> >>> Bob Camp wrote: >>> >>>> Hi >>>> >>>> Which *still* carefully avoids the issue of how ..... >>>> >>>> Bob >>>> >>>> >>>> On Feb 27, 2010, at 8:52 PM, Bruce Griffiths wrote: >>>> >>>> >>>> >>>>> Oops! a small correction (2nd paragraph): >>>>> >>>>> For the 5370A attenuating the 5V CMOS signal to a 1V swing with the >>>>> threshold set to 0.5V is close to optimum. >>>>> An input signal with limits of 0V and +1.4V with a trigger threshold of >>>>> 0.7V is the maximum usable (for high performance). >>>>> An input signal with limits of 0V and +0.3V with a trigger threshold of >>>>> 0.15V is the minimum usable (for high performance). >>>>> >>>>> For the 5370B attenuating the 5V CMOS signal to a 2V swing with the >>>>> threshold set to 1V is close to optimum. >>>>> An input signal with limits of 0V and +3.5V with a trigger threshold of >>>>> 0.7V is the maximum usable (for high performance). >>>>> An input signal with limits of 0V and +0.3V with a trigger threshold of >>>>> 0.15V is the minimum usable (for high performance). >>>>> >>>>> Thus using the PPS output (~270 ohm is series with a 5V 74AC04 output) >>>>> from a Synergy evaluation board that uses an M12M or M12+ GPS timing >>>>> receiver to drive the inputs (with a 0-750mV signal) of a 5370A or 5370B >>>>> is well within the recommended input signal range for high performance. >>>>> This avoids having to adding an external 5V 50 ohm driver that some would >>>>> use. >>>>> >>>>> Bruce >>>>> >>>>> Bob Camp wrote: >>>>> >>>>> >>>>>> Hi >>>>>> >>>>>> So exactly how did you know that I bought a (cheap) 5370B a few hours >>>>>> ago on the e-place and was just about to ask about how best to use it. >>>>>> >>>>>> Hmmmm....... >>>>>> >>>>>> Bob >>>>>> >>>>>> >>>>>> On Feb 27, 2010, at 7:01 PM, Bruce Griffiths wrote: >>>>>> >>>>>> >>>>>> >>>>>> >>>>>>> The attached excerpts from the 5370A and 5370B manuals indicate that >>>>>>> for best performance, that the common practice of driving the 5370A/B >>>>>>> 1x inputs directly from a 5V CMOS logic signal is a bad idea. >>>>>>> >>>>>>> For the 5370A attenuating the 5V CMOS signal to a 1V swing with the >>>>>>> threshold set to 0.5V is close to optimum. >>>>>>> An input signal with limits of 0V and +1.4V with a trigger threshold of >>>>>>> 0.7V is the maximum usable (for high performance). >>>>>>> An input signal with limits of 0V and +0.3V with a trigger threshold of >>>>>>> 0.15V is the minimum usable (for high performance). >>>>>>> >>>>>>> For the 5370A attenuating the 5V CMOS signal to a 2V swing with the >>>>>>> threshold set to 1V is close to optimum. >>>>>>> An input signal with limits of 0V and +3.5V with a trigger threshold of >>>>>>> 0.7V is the maximum usable (for high performance). >>>>>>> An input signal with limits of 0V and +0.3V with a trigger threshold of >>>>>>> 0.15V is the minimum usable (for high performance). >>>>>>> >>>>>>> Bruce >>>>>>> >>>>>>> <5370ATriggering.png><5370BTriggering.png>_______________________________________________ >>>>>>> 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. >>>>>>> >>>>>>> >>>>>>> >>>>>> _______________________________________________ >>>>>> 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. >>>>>> >>>>>> >>>>>> >>>>>> >>>>> >>>>> _______________________________________________ >>>>> 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. >>>>> >>>>> >>>>> >>>> _______________________________________________ >>>> 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. >>>> >>>> >>>> >>> >>> >>> _______________________________________________ >>> 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. >>> >>> >> >> _______________________________________________ >> 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. >> >> > > > > _______________________________________________ > 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. > _______________________________________________ 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.
