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Re: OpAmp design - from theory to practice

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Am 30.03.2017 um 10:02 schrieb Francesco Zappon:
> On Wednesday, 29 March 2017 18:53:21 UTC+2, Tim Wescott  wrote:

>> Just to _really_ throw a wrench into the works: <whatever>-to-frequency
>> is an old idea that's mostly gone out of favor because of advances in
>> digital processing and in ADC converters.  If I were on your team I would
>> be questioning the system-level decision to continue using it -- but I'd
>> be ready to back off from that if there's good reasons to stick with it.
>
> As I said, not an expert; I am not really sure what is the message you are
 > trying to convey here, so I can give you some more details:
>
> - we are designing a custom ASIC because discrete components cannot
 > withstand the expected level of radiation (target is 10kgy in 20 years
 > and probably more)
> - given that, we cannot use FPGAs either! the ASIC must operate "standalone"
 > and using basic components only (all validated for radiation 
hardness, of course)
> - starting from this, I don't really see other solutions. I mean, maybe a
 > self-switching, multi-range CFC might not be the best option
> (Sigma-Delta? pipeline?)  but we have an input current and we need to digitize it,
> there is no escape from that :)

I do not see the direct connection between cf converters and FPGAs,
but FPGAs can be used in a radiation infested environment. I just have
designed a few. You'll need to make registers, counters, RAMs triple
module redundant, but you need that in your custom chip also. The
contents of a RAM cell or flipflop that is hit is lost, even hard
wired gates can malfunction for some time.

Even voltage regulators that are hit can go berserk for a few
milliseconds. Be sure to have enough output capacitance so the
regulator cannot kill everything while it is delirious.

I have made a nice library that looks like std_logic / std_logic_vector
and that hides most of the nasty triple module redundancy details.
No, it is not available.

In RAM-based FPGAs like our prehistoric Virtexes is the additional
complication that the configuration is stored in RAM and that is
vulnerable. So, the config ram must be reloaded on a regular base
from the external ROM while the chip is running. That can be done
but it is a nasty thing to do, especially if the scrubber logic
is on the chip to be scrubbed.

You also cannot use distributed RAMs in the Xilinx case since that
are really small parts of the configuration ram made accessible to the
user. Our software lady found out that her Picoblaze registers would
auto-clear all few minutes. Turned out that it uses a distributed RAM
for its registers and that was overwritten by the scrubber. But it
proved at least that the scrubber works.

I could heal that by patching the Picoblaze to use solid flip flops
instead of the 16 bit RAMs. :-)

regards, Gerhard

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OpAmp design - from theory to practice Francesco Zappon <cescozep@gmail.com> - 2017-03-29 07:55 -0700
  Re: OpAmp design - from theory to practice Tim Wescott <tim@seemywebsite.com> - 2017-03-29 11:51 -0500
  Re: OpAmp design - from theory to practice Tim Wescott <tim@seemywebsite.com> - 2017-03-29 11:53 -0500
    Re: OpAmp design - from theory to practice Francesco Zappon <cescozep@gmail.com> - 2017-03-30 01:02 -0700
      Re: OpAmp design - from theory to practice Martin Brown <'''newspam'''@nezumi.demon.co.uk> - 2017-03-30 10:54 +0100
        Re: OpAmp design - from theory to practice sroberts6328@gmail.com - 2017-03-30 05:25 -0700
      Re: OpAmp design - from theory to practice Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2017-03-30 14:37 +0200
        Re: OpAmp design - from theory to practice Francesco Zappon <cescozep@gmail.com> - 2017-03-30 07:16 -0700
          Re: OpAmp design - from theory to practice Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2017-03-30 20:25 +0200
            Re: OpAmp design - from theory to practice bitrex <bitrex@de.lete.earthlink.net> - 2017-03-30 14:51 -0400
            Re: OpAmp design - from theory to practice Joerg <news@analogconsultants.com> - 2017-03-30 12:58 -0700
              Re: OpAmp design - from theory to practice pcdhobbs@gmail.com - 2017-03-30 13:25 -0700
              Re: OpAmp design - from theory to practice Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2017-03-30 23:55 +0200
                Re: OpAmp design - from theory to practice Joerg <news@analogconsultants.com> - 2017-03-30 16:43 -0700
          Re: OpAmp design - from theory to practice George Herold <gherold@teachspin.com> - 2017-03-30 11:43 -0700
            Re: OpAmp design - from theory to practice Francesco Zappon <cescozep@gmail.com> - 2017-03-30 15:02 -0700
            Re: OpAmp design - from theory to practice Jeroen Belleman <jeroen@nospam.please> - 2017-03-31 10:20 +0200
      Re: OpAmp design - from theory to practice Tim Wescott <tim@seemywebsite.com> - 2017-03-30 12:14 -0500
        Re: OpAmp design - from theory to practice Francesco Zappon <cescozep@gmail.com> - 2017-03-30 15:05 -0700
  Re: OpAmp design - from theory to practice Joerg <news@analogconsultants.com> - 2017-03-30 10:45 -0700
    Re: OpAmp design - from theory to practice JM <dontreplytothis173@gmail.com> - 2017-03-30 19:32 +0100
      Re: OpAmp design - from theory to practice Joerg <news@analogconsultants.com> - 2017-03-30 12:47 -0700
        Re: OpAmp design - from theory to practice Francesco Zappon <cescozep@gmail.com> - 2017-03-30 15:16 -0700
          Re: OpAmp design - from theory to practice George Herold <gherold@teachspin.com> - 2017-03-30 16:11 -0700
          Re: OpAmp design - from theory to practice Joerg <news@analogconsultants.com> - 2017-03-30 16:57 -0700

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