Re: ball-hours

From	Joerg <news@analogconsultants.com>
Newsgroups	sci.electronics.design, comp.lang.forth
Subject	Re: ball-hours
Date	2014-10-17 07:14 -0700
Message-ID	<cacmifFj1vgU1@mid.individual.net> (permalink)
References	(8 earlier) <m1nbn1$pu7$1@dont-email.me> <caagkuF1v4jU1@mid.individual.net> <m1p626$nu5$1@dont-email.me> <caaokmF457jU1@mid.individual.net> <m1pe4h$lcl$1@dont-email.me>

Cross-posted to 2 groups.

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rickman wrote:
> On 10/16/2014 4:37 PM, Joerg wrote:
>> rickman wrote:
>>>
>>> Each processor is very low power when running flat out, just 5 mW.  But
>>> they almost never run flat out.  Because they are asynchronous they
>>> spend most of their time stopped when they draw 0.0875 uW, yes, that's
>>> less than a tenth of a uW for each processor or just 12 uW for the whole
>>> chip.  The processors respond to stimuli in just nanoseconds, not 100's
>>> or even 10' but single digit nanoseconds.
>>>
>>> Trust me, power will not be a problem with this part.  It is a very
>>> different beast to program however.
>>>
>>
>> I wonder how that company is doing. I read about their products years
>> ago but never seen any in schematics and I get to see a lot of new stuff
>> because some of my daily bread is EMC remedy.
> 
> I think they are doing ok, but mainly because they have nearly zero
> overhead.  They don't pay any salaries so no need for layoffs.
> 

Wow. So they all work for free? How do they make a living?

> 
>>> Every problem in your design is asking for an FPGA.
>>>
>>
>> Possible, but not sure yet. Maybe there is a bigger processor out there
>> with real I2S/TDM and enough support by the manufacturer.
> 
> Yeah, maybe.  You can go with one of the Cortex A processors like they
> use in the Beagle board or Raspberry Pi.  Without the Linux OS they
> should so a decent job.  They have floating point for your FFTs as well.
>  That will help prevent too much rounding noise in the FFTs.
> 

Except the Sitaras in QFP have been obsoleted. But I'll find something.

> 
>>>>> What are the specs you need from the ADC?  Do you have numbers and
>>>>> such?
>>>>>    I think you mentioned a low drift with temperature.  The GA144
>>>>> would
>>>>> need to be compensated for temperature, but has lots of processing
>>>>> to do
>>>>> that.  :)
>>>>>
>>>>
>>>> Five needed in total, 18bits or more, 48ksps, differential inputs, BW
>>>> from DC to 15kHz, without phase jitter issues. DC-Offset can be handled
>>>> via mux and SW-clamping as long as it won't jitter or drift around
>>>> much.
>>>
>>> "phase jitter issues" and "won't jitter or drift around much" aren't
>>> specs.
>>
>>
>> What I mean is that ADCs on processors generally cannot hold jitter low
>> enough to truly deliver a 96dB SNR. I found that even 12 bits on-chip is
>> already a serious challenge.
>>
>>
>>   18 bits of what exactly?  I have seen lots of devices with 24
>>> bits but only 96 dB SNR.  Do you need 108 dB SNR?  You won't get that
>>> from the GA144 ADCs at 48 kHz.
>>>
>>
>> True 96dB across DC-15kHz would be enough.
> 
> So a 16 bit part with DC coupling would be good enough?  


No, because ENOB counts and there you need around 18 bits.


>                                               ... The market is
> *littered* with those.  I've seen a bazillion 18 bit SAR parts out
> there.  Even LT has them, your favorite company.  Why not use one of
> those?  They often have fantastic SNR and THD specs.
> 
> How about an 8 channel, 16 bit ADC in one package?
> 
> http://www.linear.com/product/LTC1867L
> 
> Well, maybe not.  The SINAD is not so good.  What is the frequency of
> the signal you are looking at?  The ADC specs also depend on your input
> frequency.
> 

DC to 20kHz but that requirement can be dropped to 10kHz. Also, if I
really, really had to, I could replace one of the two DACs with a DDS
chip because that just generates a sine wave. But it complicates the SW
because such chips need their own SPI sermons in Swahili.


> The point is that if you can drop the I2S interface you have a lot more
> potential MCUs to choose from.
> 

Sure, if the CPU can manage to keep seven balls in the air and serve all
those SPI device at 48ksps.

-- 
Regards, Joerg

http://www.analogconsultants.com/

Thread

Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-15 00:25 -0400
  Re: ball-hours bruce.person@gmail.com - 2014-10-14 23:51 -0700
    Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-15 03:15 -0400
  Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-15 05:36 -0700
    Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-15 16:22 -0400
      Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-15 16:12 -0700
        Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-15 22:48 -0400
          Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-16 11:21 -0700
            Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-16 15:24 -0400
              Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-16 13:37 -0700
                Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-16 17:42 -0400
                Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-17 07:14 -0700
                Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-17 14:03 -0400
                Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-17 12:03 -0700
                Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-17 15:23 -0400
                Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-17 12:44 -0700
                Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-17 18:37 -0400
                Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-16 20:59 -0400
                Re: ball-hours albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-10-17 08:43 +0000
                Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-17 13:53 -0400
                Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-17 07:50 -0700
        Re: ball-hours Raimond Dragomir <raimond.dragomir@gmail.com> - 2014-10-15 20:42 -0700
          Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-16 01:50 -0400
            Re: ball-hours Raimond Dragomir <raimond.dragomir@gmail.com> - 2014-10-16 00:49 -0700
              Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-16 05:14 -0400
            Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-16 11:58 -0700
        Re: ball-hours "Elizabeth D. Rather" <erather@forth.com> - 2014-10-16 08:32 -1000
          Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-16 15:32 -0400
          Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-16 13:45 -0700

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