[time-nuts] Re: MT3339 chipset 10ns jitter?

Fabio Eboli fabioeb at quipo.it
Mon Nov 26 21:29:39 UTC 2012


Hello Jacques, and the List.

Thank you for sharing these docs.
Indeed the PPS specs of the MT3339 are confusing.
Maybe measurement on a living specimen can help?

I have a R-D 1992 counter, and a GPIB interface.
When I will have the GPS I will be able to log
some data on the PC, although I never tried to use
the Racal Counter remotely I will try.
Also I hope somebody can suggest the best way to test
the PPS from the gps using the Racal 1992, I'm not a
time nut, so I could make gross errors.
I was thinking simply to measure and log the PPS
connected to input A with the counter set to
"Period A", and 10s integration time to gain
more resolution, all this for some (many?) hours.

Fabio.

Jacques Tiete <jacques at tiete.org> ha scritto:

> Hello TNutters,
>
> maybe new thread?
>
> you can have a look at two specsheets of the MT3339 chipset on my FTP-site
> 1) http://nixie.ramdac.be/TNutstuff/MT_IT530_Data_Sheet_rev_1_0.pdf
> 		on page 8 "PPS output 100 ms high pulse, rising edge +/-1 μs @  
> full second GPS epoch..." so it states +/-1 μs
> 2) http://nixie.ramdac.be/TNutstuff/gtop module application note  
> -a00 _mt3339 series_.pdf
> 		on page 32 "The accuracy level of 1PPS for GlobalTop GPS module is  
> within 100ns (same for majority of MTK GPS modules).
> 					The reference design below can help improving this accuracy to  
> within 80ns."
> 		but on page 14 "1PPS signal is an output pulse signal used for  
> timing application, its electronic characteristic are listed below:
> 						1PPS signal and its pulse width with 100ms duration
> 						Low Voltage level: 0~0.4V
> 						High Voltage level: 2.8~3.1V
> 						Duration: 100ms (Firmware customization for duration is available)
> 						Period: 1s Accuracy (jitter):10ns"
>
> So what shall we believe?
> The rest of the PDF's make a good read.
>
> 73's
>
> Jacques
>
>
>
>
> Message: 4
> Date: Fri, 23 Nov 2012 16:44:27 +0100
> From: Jacques Tiete <jacques at tiete.org>
> To: "time-nuts at febo.com" <time-nuts at febo.com>
> Subject: Re: [time-nuts] time-nuts Digest, Vol 100, Issue 95
> Message-ID: <7C466C42-C05A-46E2-B3C4-793672874AC8 at tiete.org>
> Content-Type: text/plain;	charset=us-ascii
>
> About:
> {
> Date: Thu, 22 Nov 2012 22:26:24 +0100
> From: Fabio Eboli <FabioEb at quipo.it>
> To: time-nuts at febo.com
> Subject: [time-nuts] MT3339 chipset in Globaltop's FGPMMOPA6H
> Message-ID: <20121122222624.71854hb9oslingcg at webmail.micso.net>
> Content-Type: text/plain; charset=ISO-8859-1; DelSp="Yes";
>   format="flowed"
>
> Hello, while asking info about the FE5682,
> I realized that for another project
> (model plane data logging) I will buy
> some cheap gps modules built around an
> MT3339 chipset.
> In my mind somewhere I stored the fact
> that in the datasheet of these module
> is mentioned the pps output, so I checked
> and the manufacturer is claiming that it
> has "High accuracy 1-PPS timing support
> for Timing Applications (10ns jitter)"
>
> This is the module I'm talking about:
> http://www.mirifica.it/store/gps/342-globaltop-fgpmmopa6h-pa6h.html
> http://www.alcom.be/binarydata.aspx?type=doc/GTop-FGPMMOPA6H-Datasheet-V0A.pdf
>
> Has anybody used this chipset or similar for GPSDO?
> I have no experience with discipled oscillators
> but if there is any hope that the pps out
> of these modules is good for the task maybe
> it's time for me to start reading more about
> the subject.
> The final goal will be to check the timing
> of the Rb I have around.
>
> Thanks,
> Fabio.
> }
>
> Hello TNutters,
>
> I did some test with this module from Adafruit  
> (http://www.adafruit.com/products/746) and it seems not a bad unit.  
> Tested it together
> with my TBolt and the PPS seems quite stable most of the time, I did  
> not do any logging and math on the result,
> just letting the TBolt trigger the scope and apart from the cable  
> offset I guess 80% of the time the module was
> within 10 to 15 ns.
> However the specs are not very clear and it is a typical chip for  
> mobile use in eg. carnav stuff. I also saw some
> other specs where the jitter was specified as 100ns. and even one  
> with a 1 microsec. so I'm a little confused.
> As soon as I have some time I plan to connect this module to a  
> BeagleBone and do some testing for an NTP server
> I think the Beagle is better for this than the RaspBerry because of  
> the "real" ethernet port.
>
> Greetz,
>
> Jacques Tiete
> 0499 99 83 78
> jacques at tiete.org
>
> Op 23-nov.-2012 om 00:19 heeft time-nuts-request at febo.com het  
> volgende geschreven
>
>



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