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 -- time-nuts@febo.com >>>>> To unsubscribe, go to >>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>> and follow the instructions there. >>>>> >>>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@febo.com >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>>> >>>> >>>> >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >>> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.