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| MS05000 Budget Logic Analyzer Probe Set Design |
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| Gandalf_Sr:
--- Quote from: texaspyro on March 04, 2020, 04:25:06 pm --- --- Quote from: Gandalf_Sr on March 04, 2020, 10:27:47 am ---I should have added that I'm trying as much as possible to maintain signal integrity and IMHO 0603 is better than 0805 in this respect (0402 would have been better still but they are more difficult to work with). --- End quote --- At the frequencies involved in the probe (200 MHz) the 0805 package size is totally acceptable. --- End quote --- I know it's overkill but I was trying to observe the LVDS routing rules with 0.3 mm trace width/gap and then not have a massive flare when it arrives at the terminating resistor just before going to the scope connector. Quit your nit-picking or I'll make them 01005s >:D |
| Gandalf_Sr:
I got the Digikey order and checked some footprints, I'm glad I did as I didn't allow enough width on the headers that are side by side on the connector PCB, this is now fixed along with a few minor changes. MY MSO5074 arrived today too and I checked the front entry space for the connector PCB, it's OK. The PCBs were ordered today from JLCPCB, I ordered 5 connector PCBs and 10 probe PCBs; remember that a set is 1 connector and 2 probe PCBs. Now I have to wait. I'll update the PCB views in a day or so. [EDIT] The PCBs shipped yesterday and their system predicts they will arrive Friday 13th (my lucky day). Sorry, still not updated any of the files. |
| Gandalf_Sr:
By way of a bump and an update, DHL says that my JLC PCBs departed from Cincinnati (250 miles South of me) at 6:30 am today and they are supposed to get to me by the end of today although that sounds a bit optimistic although possible; the main freight truck will probably get to Michigan around 11 am (unless they are flying them up) and then they'd have to make it onto the actual delivery truck and to my house. If they don't make it today, they could be delivered tomorrow. [EDIT] seems the package got to Romulus Michigan in 2.5 hours so, unless they drove it up in a Ferrari at 100 mph, it must've flown up :D. Yup, it got here around noon and the PCBs look great. I revisited the documentation on LVDS vs LVPECL and I think that LVDS running at 3.3V and driving into a 100 \$\Omega\$ resistor close to the MSO5000 connector is going to drive the MSO5000 internal circuits OK, I will run a test before I fully populate the PCBs as it may need a 120 \$\Omega\$ resistor - I really hope this is going to work as it could be a show-stopper; I should have tested first but I didn't. Sigh! [EDIT] I asked over at the other real LA teardown thread and dug into the driver datasheets; the real LA probe set uses LMH7322s which are hooked up, with 2.5V for Vcco, which makes them run with LVDS-compatible outputs with H = Vcco - 1.0V and L = Vcco - 1.4V (centered on 1.2V) which is LVDS-compatible. My design uses DS90LV047As which have LVDS outputs which should be fully compatible with the MSO5000 inputs - we'll see. I was planning a fun trip to Chicago with my Brother next week but we cancelled due to the COVID-19, weld-yourselves-into-your-houses, panic. So now I'll be able to work on this unless I get some paid work to do. |
| Gandalf_Sr:
IT's ALIVE!!!!! BWAHAHAHAHAHAHAAAA Go back and see the second post for updated pictures of it running (at 10 MHz). I only built the 0.65-3.3V probe board so far and the input protection Zeners were missing from my Digikey order so it's running without them for now. I'm VERY happy with the results so far. First 8 channels are all the correct polarity and the LVDS signals are clearly working at least at 10 MHz, I tested channels 0-7 so far. |
| Sighound36:
Would just like to say this thread is what really good about this forum sharing knowledge and experiences top stuff Gandolf_Sr. I just do not have the time to do these sorts of projects at the moment and its great to see :-+ Promise I will do an update on the 8000 thread soon. |
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