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Re: analog failures

From Joerg <news@analogconsultants.com>
Newsgroups sci.electronics.design
Subject Re: analog failures
Date 2017-02-18 07:41 -0800
Message-ID <egr88sFp34oU1@mid.individual.net> (permalink)
References (5 earlier) <egjbr9F7dhiU1@mid.individual.net> <s609acdk8jegfeslhbhnl9dmpf11u6se21@4ax.com> <o87mdm$qru$2@dont-email.me> <egpackFdjfvU2@mid.individual.net> <rd8facd0n8c66itk6jr8df65s2c71d2stq@4ax.com>

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On 2017-02-17 17:27, John Larkin wrote:
> On Fri, 17 Feb 2017 14:05:20 -0800, Joerg <news@analogconsultants.com>
> wrote:
>
>> On 2017-02-17 12:30, rickman wrote:
>>> On 2/15/2017 11:30 AM, John Larkin wrote:
>>>> On Wed, 15 Feb 2017 07:53:18 -0800, Joerg <news@analogconsultants.com>
>>>> wrote:
>>>>
>>>>> On 2017-02-14 19:55, Reinhardt Behm wrote:
>>>>>> AT Wednesday 15 February 2017 11:00, bill.sloman@ieee.org wrote:
>>>>>>
>>>>>>> On Wednesday, February 15, 2017 at 1:52:23 PM UTC+11, Reinhardt Behm
>>>>>>> wrote:
>>>>>>>> AT Wednesday 15 February 2017 07:05, Lasse Langwadt Christensen
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> Den tirsdag den 14. februar 2017 kl. 23.47.11 UTC+1 skrev John
>>>>>>>>> Larkin:
>>>>>>>>>> http://semiengineering.com/devices-threatened-by-analog-content/
>>>>>>>>>>
>>>>>
>>>>> IME most analog failures are caused by ESD and that is often squarely in
>>>>> the court of the board level designer.
>>>>>
>>>>> Upsets without subsequent chip damage are also considered a fault where
>>>>> the function is mission-critical. That is very often due to EMI.
>>>>>
>>>>>
>>>>>>>>>> My experience is that we find a lot of bugs and documentation
>>>>>>>>>> problems
>>>>>>>>>> with the digital parts of mixed-signal chips.
>>>>>>>>>
>>>>>>>>> It does seem like when analog designers get to design the digital
>>>>>>>>> parts
>>>>>>>>> of a chip it often ends up with a hairball of hazards and weird
>>>>>>>>> quirks
>>>>>>>>
>>>>>>>> That was always my experience with part from NatSemi. Pure analog was
>>>>>>>> good, pure digital was good, mixed mostly was a mess.
>>>>>>>
>>>>>>> Mixed signal design is difficult, and doing it on a chip, where it is
>>>>>>> harder to keep the noisy digital bits away from the sensitive
>>>>>>> analog bits,
>>>>>>> wouldn't have made it any easier.
>>>>>>>
>>>>>>> Sadly, mixed signal design can do a lot more than pure analog or pure
>>>>>>> digital, so if you have got something complicated to do, that tends
>>>>>>> to be
>>>>>>> what you end up doing.
>>>>>>
>>>>>> It was never the problem of digital noise coupling into the analog
>>>>>> portions
>>>>>> but the digital totally mixed up, like the LM75 going into a state
>>>>>> where
>>>>>> only a power cycle helps to get it working again. This can be caused by
>>>>>> noise on the I2C signals.
>>>>>
>>>>>
>>>>> I2C is a bus I try not to use if it can be avoided because of various
>>>>> hang-ups. SPI is much more robust IME and, therefore, that is what I
>>>>> prefer.
>>>>
>>>> I prefer SPI too, and it's faster, but lots of people design terrible
>>>> SPI interfaces, bad logic design and bad clock/data circuits. Every
>>>> SPI should have schmitt inputs and safe timing margins. Maybe cooking
>>>> a digital design into an analog process causes compromises, but I
>>>> suspect it's just sloppy engineering.
>>>
>>> Not trying to be snarky, but most digital engineers work to eliminate
>>> noise and to have proper clocks without noise on the transition edge.
>>> Schmitt is only needed on the clock inputs, but even there proper design
>>> at the board level eliminates the need.
>>>
>>
>> Schmitt is needed everywhere a signal connect to the outside world. A
>> lot of uC design engineers do not understand this.
>>
>> [...]
>
> Multi-drop SPI can have clock and chip-select traces all over a board.
> A glitch or bounce on either can be bad news. It's nice if everything
> works without building matched-impedance terminated-driver tree
> structures. Geez, it's just SPI.
>
> MOSI and MISO don't need schmitts, but why not?
>

Many reasons. In micro-power systems it's a given because any fraction 
of a microsecond spent in transition or multiple transitions will result 
in increased power consumption. The other effect is that multiple 
triggering of the input threshold on a line that digital guys consider 
"unimportant" can blow EMC.

Sometimes it's fun to design micro-power. Now how can we shave off two 
more microamps?

-- 
Regards, Joerg

http://www.analogconsultants.com/

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Thread

analog failures John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-14 14:47 -0800
  Re: analog failures Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-02-14 15:05 -0800
    Re: analog failures Reinhardt Behm <rbehm@hushmail.com> - 2017-02-15 10:52 +0800
      Re: analog failures bill.sloman@ieee.org - 2017-02-14 19:00 -0800
        Re: analog failures Reinhardt Behm <rbehm@hushmail.com> - 2017-02-15 11:55 +0800
          Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-15 07:53 -0800
            Re: analog failures John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-15 08:30 -0800
              Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-15 10:19 -0800
                Re: analog failures John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-15 10:53 -0800
                Re: analog failures Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-02-15 10:58 -0800
                Re: analog failures "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-15 21:25 -0600
                Re: analog failures John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-15 20:18 -0800
                Re: analog failures rickman <gnuarm@gmail.com> - 2017-02-17 15:44 -0500
              Re: analog failures rickman <gnuarm@gmail.com> - 2017-02-17 15:30 -0500
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-17 14:05 -0800
                Re: analog failures rickman <gnuarm@gmail.com> - 2017-02-17 17:16 -0500
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-17 14:38 -0800
                Re: analog failures rickman <gnuarm@gmail.com> - 2017-02-17 17:58 -0500
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-17 15:37 -0800
                Re: analog failures rickman <gnuarm@gmail.com> - 2017-02-17 18:51 -0500
                Re: analog failures krw@notreal.com - 2017-02-17 20:27 -0500
                Re: analog failures John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-17 17:56 -0800
                Re: analog failures "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-17 21:03 -0600
                Re: analog failures krw@notreal.com - 2017-02-17 22:36 -0500
                Re: analog failures rickman <gnuarm@gmail.com> - 2017-02-19 00:45 -0500
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-19 08:32 -0800
                Re: analog failures John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-21 12:31 -0800
                Re: analog failures rickman <gnuarm@gmail.com> - 2017-02-23 14:57 -0500
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-23 12:02 -0800
                Re: analog failures John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-17 17:27 -0800
                Re: analog failures rickman <gnuarm@gmail.com> - 2017-02-17 20:39 -0500
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-18 07:41 -0800
                Re: analog failures John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-18 08:04 -0800
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-18 08:16 -0800
            Re: analog failures Reinhardt Behm <rbehm@hushmail.com> - 2017-02-16 06:49 +0800
              Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-16 07:14 -0800
                Re: analog failures John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-16 07:24 -0800
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-16 07:41 -0800
                Re: analog failures Reinhardt Behm <rbehm@hushmail.com> - 2017-02-17 13:22 +0800
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-17 06:58 -0800
                Re: analog failures John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-17 12:26 -0800
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-17 14:03 -0800
                Re: analog failures "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-17 21:05 -0600
                Re: analog failures John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-18 08:07 -0800
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-18 08:20 -0800
                Re: analog failures John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-18 09:20 -0800
                Re: analog failures rickman <gnuarm@gmail.com> - 2017-02-19 00:48 -0500
                Re: analog failures John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-21 12:39 -0800
                Re: analog failures "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-21 22:54 -0600
                Re: analog failures krw@notreal.com - 2017-02-17 20:33 -0500
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-18 07:37 -0800
                Re: analog failures dagmargoodboat@yahoo.com - 2017-02-22 15:45 -0800
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-23 10:43 -0800
                Re: analog failures krw@notreal.com - 2017-02-23 20:42 -0500
                Re: analog failures "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-24 03:31 -0600
                Re: analog failures grahamholloway@graham65.plus.com - 2017-02-24 06:39 -0800
                Re: analog failures Don Kuenz <g@crcomp.net> - 2017-02-24 14:58 +0000
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-25 12:48 -0800
                Re: analog failures pcdhobbs@gmail.com - 2017-02-26 04:39 -0800
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-26 07:52 -0800
                Re: analog failures dagmargoodboat@yahoo.com - 2017-02-24 09:02 -0800
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-25 12:44 -0800
                Re: analog failures dagmargoodboat@yahoo.com - 2017-02-26 08:29 -0800
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-26 09:46 -0800
                Re: analog failures John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-26 10:11 -0800
                Re: analog failures krw@notreal.com - 2017-02-26 17:55 -0500
                Re: analog failures John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-26 15:09 -0800
                Re: analog failures krw@notreal.com - 2017-02-26 19:30 -0500
                Re: analog failures John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-27 10:37 -0800
                Re: analog failures Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-02-24 09:14 -0800
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-25 12:46 -0800
                Re: analog failures Klaus Kragelund <klauskvik@hotmail.com> - 2017-02-26 17:44 -0800
                Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-27 07:51 -0800
                Re: analog failures Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2017-02-23 21:36 +0200
                Re: analog failures dagmargoodboat@yahoo.com - 2017-02-24 08:38 -0800
                Re: analog failures krw@notreal.com - 2017-02-24 20:20 -0500
                Re: analog failures kevin93 <kevin@whitedigs.com> - 2017-02-24 17:36 -0800
      Re: analog failures Ralph Barone <ralph@invalid.com> - 2017-02-15 03:25 +0000
    Re: analog failures John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-14 19:20 -0800
  Re: analog failures Tim Wescott <seemywebsite@myfooter.really> - 2017-02-14 17:46 -0600
    Re: analog failures Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-14 17:50 -0700
      Re: analog failures Tim Wescott <tim@seemywebsite.com> - 2017-02-14 23:49 -0600
        Re: analog failures Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-15 07:03 -0700
        Re: analog failures John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-15 10:18 -0800
          Re: analog failures Tim Wescott <seemywebsite@myfooter.really> - 2017-02-15 15:06 -0600
  Re: analog failures legg <legg@nospam.magma.ca> - 2017-02-16 23:06 -0500
    Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-17 07:00 -0800
      Re: analog failures legg <legg@nospam.magma.ca> - 2017-02-17 13:22 -0500
        Re: analog failures Joerg <news@analogconsultants.com> - 2017-02-17 11:06 -0800

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