Re: [psas-avionics] Capstone Generic node update
Thanks for the feedback Tim, I've fixed the issue with the ground return paths on the TPS63000 (I think). As for the other problems, they'll take me a bit more time to figure out what I want to rearrange. As for the 0kaz library, I have added it to git so you can review any of the packages I have made so far if you like. The SJ280 width errors I have been meaning to ask about. I think they are cuttable jumpers, can I set that width to anything I want, or is there a reasonable maximum for a cuttable trace width? Thanks, Ken - Original Message From: rq1...@q7.com rq1...@q7.com To: psas-avionics@lists.psas.pdx.edu Sent: Sunday, May 24, 2009 5:18:44 PM Subject: Re: [psas-avionics] Capstone Generic node update (2009.05.23) kenz...@yahoo.com: Ok, so I have made some progress today on the layout for the front end. I still haven't added any polygons for ground or power planes yet, everything is still coming together somewhat.? At least I finally have all the components on the board.If any of you have time, could you please review what I have so far so I can have changes ready by Tuesday? The files are node5-frontend.sch and node5-frontend.brd for the schematic and board. I think pretty good so far :) There are a couple width errors in the DRC you should probably fix, e.g. SJ280 WINDOW 5 (2745 1481); It's good practice to equalize the gaps between signals, cf. to the right of C13 SHOW @ C13 I personally think the battery should be on the bottom of the board. Andrew, i believe, agrees. In fact he had mentioned putting the battery on a sub-carrier board that would screw onto the main node board. The actual battery connection made with some convenient board to board connector, JST, 2 mm, etc. I haven't analyzed the switching power supplies, but at frequencies above 1 MHz ground return path becomes a significant consideration. It is possible to handle all your ground returns with vias into the ground plane, and that may be acceptable, but for certain critical paths it is better to route entirely on the component plane. For example, U2203 C2221, the capacitor is the input bypass for the switcher running at 1.5 MHz. The signal to be bypassed is PROTECTED_DC_POWER, which is actually adjacent to the grounded pad of the chip, but the grounded end of the capacitor is too far away to effectively reach the pad. I think TI intended that C2211 sit directly over the chip so as to make the direct connection to the pad. The principle of providing very short paths for signals that are both high frequency and high current applies to all the switching supplies. You should keep this in mind during layout. I think what is driving the placement of C2221 is the fact that you have laid out without much regard to ground connection distance. This is generally the right thing to do if you have a ground plane. The exception would be the critical paths associated with the switching supplies. There is a funny thing going on with U2203 where some of the traces running into the pad are generating overlap errors. I can't really evaluate this because your private library 0kaz does not seem to be in git. It should be. Mostly things seem pretty reasonable. Have you coordinated with Scott on APS real estate allocation? It looks roughly right to me but i suspect you'll need to push leftward a bit. I'm pretty busy 'til Tuesday, but if you have more questions, fire away, i'll try :) ___ psas-avionics mailing list psas-avionics@lists.psas.pdx.edu http://lists.psas.pdx.edu/mailman/listinfo/psas-avionics ___ psas-avionics mailing list psas-avionics@lists.psas.pdx.edu http://lists.psas.pdx.edu/mailman/listinfo/psas-avionics
Re: [psas-avionics] Capstone Generic node update
(2009.05.25) kenz...@yahoo.com: [..] I've fixed the issue with the ground return paths on the TPS63000 (I think).? Yep, that's what i had in mind. As for the 0kaz?library, I have added it to git so you can review any of the packages I have made so far if you like. Great, thanks. The SJ280 width errors I have been meaning to ask about. I?think they are cuttable jumpers, can I set that width to anything I want, or is there a reasonable maximum for a cuttable trace width? 10 - 12 mil is reasonable, and i think compatible with your package. ___ psas-avionics mailing list psas-avionics@lists.psas.pdx.edu http://lists.psas.pdx.edu/mailman/listinfo/psas-avionics
Re: [psas-avionics] Capstone Generic node update
(2009.05.23) kenz...@yahoo.com: Ok, so I have made some progress today on the layout for the front end. I still haven't added any polygons for ground or power planes yet, everything is still coming together somewhat.? At least I finally have all the components on the board.If any of you have time, could you please review what I have so far so I can have changes ready by Tuesday? The files are node5-frontend.sch and node5-frontend.brd for the schematic and board. I think pretty good so far :) There are a couple width errors in the DRC you should probably fix, e.g. SJ280 WINDOW 5 (2745 1481); It's good practice to equalize the gaps between signals, cf. to the right of C13 SHOW @ C13 I personally think the battery should be on the bottom of the board. Andrew, i believe, agrees. In fact he had mentioned putting the battery on a sub-carrier board that would screw onto the main node board. The actual battery connection made with some convenient board to board connector, JST, 2 mm, etc. I haven't analyzed the switching power supplies, but at frequencies above 1 MHz ground return path becomes a significant consideration. It is possible to handle all your ground returns with vias into the ground plane, and that may be acceptable, but for certain critical paths it is better to route entirely on the component plane. For example, U2203 C2221, the capacitor is the input bypass for the switcher running at 1.5 MHz. The signal to be bypassed is PROTECTED_DC_POWER, which is actually adjacent to the grounded pad of the chip, but the grounded end of the capacitor is too far away to effectively reach the pad. I think TI intended that C2211 sit directly over the chip so as to make the direct connection to the pad. The principle of providing very short paths for signals that are both high frequency and high current applies to all the switching supplies. You should keep this in mind during layout. I think what is driving the placement of C2221 is the fact that you have laid out without much regard to ground connection distance. This is generally the right thing to do if you have a ground plane. The exception would be the critical paths associated with the switching supplies. There is a funny thing going on with U2203 where some of the traces running into the pad are generating overlap errors. I can't really evaluate this because your private library 0kaz does not seem to be in git. It should be. Mostly things seem pretty reasonable. Have you coordinated with Scott on APS real estate allocation? It looks roughly right to me but i suspect you'll need to push leftward a bit. I'm pretty busy 'til Tuesday, but if you have more questions, fire away, i'll try :) ___ psas-avionics mailing list psas-avionics@lists.psas.pdx.edu http://lists.psas.pdx.edu/mailman/listinfo/psas-avionics
[psas-avionics] Capstone Generic node update
Ok, so I have made some progress today on the layout for the front end. I still haven't added any polygons for ground or power planes yet, everything is still coming together somewhat. At least I finally have all the components on the board.If any of you have time, could you please review what I have so far so I can have changes ready by Tuesday? The files are node5-frontend.sch and node5-frontend.brd for the schematic and board. Thanks, Ken ___ psas-avionics mailing list psas-avionics@lists.psas.pdx.edu http://lists.psas.pdx.edu/mailman/listinfo/psas-avionics
