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  • jmg wrote: »
    cgracey wrote: »
    ...

    Meanwhile, I rented an ESD zapper gun, since my old one went kaput, and I've been zapping the prior test chip. It has the same ESD circuits as the new one, so it can reveal any ESD weakness in our design. Surprisingly, the chip failed ESD testing miserably! The problem is that the core ground (GND) and I/O ground (GIO), while normally at the same potential, can get a huge differential during a zap.

    The core ground and I/O grounds are not shorted together on the die, but are both bonded down to the exposed pad, which becomes BOTH grounds. This was done to keep core ground currents, which are quite high on the die and cause ~25mV differences on what should be the same "ground", isolated from the I/O grounds which may be doing ADC and DAC operations that would be really compromised by ground noise. Anyway, during an ESD zap, those core and I/O grounds could be 50V apart for a few nanoseconds. This was causing my level shifters to blow out, as delicate NMOS gates were exposed to this havoc.

    In order to fix this, I need to add a resistor and a small ESD clamp on each of the cross-domain connections where the NMOS transistors are being driven.

    I had plenty of ESD protection where I thought it was needed, but totally missed the other vulnerabilities. Today I'm working on the schematic for the PAD ring elements to fix all this.

    That sounds like it will slow signals down ? (and may not give best protection)

    Can you not add some 'fat' back to back diodes (one may be there already) between the two grounds ?
    In normal operation, they are mV separate, but in ESD event, the diodes ensure the GNDs cannot wander too far apart ?


    Yes, I'd like to get away with just big back-to-back diodes. I'm looking through the PDK now to see how to call this out.

    If we could keep the grounds close together, there shouldn't be a need for the resistor-clamp ESD circuits between ground domains. Those circuits do add about 500ps of delay.
  • Assuming this shuttle run goes better than the P2 Hot one did, even if it's not perfect what are the chances some of us might snag one of the beta chips for a little testing of our own? I would be willing to lay out a bit of coin just for the coolness factor of having one of the functional prototypes.
  • This shuttle doesn't have any cogs as such. It basically the ring frame without smarts, word to io pins for testing.
    My Prop boards: P8XBlade2, RamBlade, CpuBlade, TriBlade
    Prop OS (also see Sphinx, PropDos, PropCmd, Spinix)
    Website: www.clusos.com
    Prop Tools (Index) , Emulators (Index) , ZiCog (Z80)
  • cgraceycgracey Posts: 8,597
    edited February 8 Vote Up0Vote Down
    I've been in Colorado Springs all week at Treehouse Design. We are wrapping up the layout changes for the Prop2 pad ring. Things are really coming together.

    Here is a picture of the lady who's been doing most of the work. Her name is Judy and she is really on top of things.

    Judy's husband Mike works here, too. He's laying out the new ESD clamping diodes and now-simplified output transistors. Today we had a few calls with a really good engineer at OnSemi who helped us straighten out some errors we were having. Tomorrow morning, the ESD clamps should come together nicely.

    Meanwhile, Judy is here at 9pm going through the pads and bringing the signals out to the core, and generally tidying everything up. We also increased the top metal layer to 3.0 micrometer thickness from 0.8. This entails some other edits. Everything is shaping up really well.
    2048 x 1152 - 1M
  • idbruceidbruce Posts: 5,558
    edited February 8 Vote Up0Vote Down
    Chip

    It almost sounds like the new CNC just might be running on a P2. However I will still need a development board.

    I wonder who will finish first... I will be welding up the frame very shortly... and my stepper power supplies should arrive Friday.

    Either way, it appears we are both making nice progress.


    Novel Solutions - http://www.novelsolutionsonline.com/ - Machinery Design • - • Product Development
    "Necessity is the mother of invention." - Author unknown.

  • cgraceycgracey Posts: 8,597
    edited February 8 Vote Up0Vote Down
    idbruce wrote: »
    Chip

    It almost sounds like the new CNC just might be running on a P2. However I will still need a development board.

    I wonder who will finish first... I will be welding up the frame very shortly... and my stepper power supplies should arrive Friday.

    Either way, it appears we are both making nice progress.

    That's excellent!

    Maybe you will be done first, though.

    Things on Prop 2 really are moving forward.
  • I'm "just" a forum member, but hats off to Judy and Mike for putting in the long hours to help with Chip's chip. Hope that Judy can sleep late tomorrow and come in around lunch time. It's great that you folks were able to arrange a phone meeting with OnSemi (the right help at the right time, it sounds like). Now, that nearly quadruple increase in the thickness of the top metal layer sounds interesting. Wonder what the story is behind that (and whether Chip will still be able to "peer" through it with his special second-hand machine). Anyway, sounds like great progress is being made. Thanks for the "Colorado update" with the picture of Judy happily slaving away, Chip.
  • Chip

    As much as I enjoy your endeavors, I am sure you would enjoy mine, but I do not provide information to the public about my projects like you do. My current project is a serious one and I will be filing a patent. I know that you are not a big fan of patents, but I am. Either way, I would love to hear your input on my current endeavor and how the P2 could benefit this machine. I am hoping to meet you someday, where Electronical meets Mechanical.


    Novel Solutions - http://www.novelsolutionsonline.com/ - Machinery Design • - • Product Development
    "Necessity is the mother of invention." - Author unknown.

  • Way to go Chip (and Treehouse friends)! :cool:
    Melbourne, Australia
  • cgracey wrote: »
    I've been in Colorado Springs all week at Treehouse Design. We are wrapping up the layout changes for the Prop2 pad ring. Things are really coming together.

    It's interesting, and satisfying, to see a project you've been working on for a long time suddenly start coming together like that. Enjoy.

    Sandy

    Infantryman's Axiom; Always cheat, always win.
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