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Groups > sci.electronics.design > #448309
| From | rickman <gnuarm@gmail.com> |
|---|---|
| Newsgroups | sci.electronics.design |
| Subject | Re: analog failures |
| Date | 2017-02-19 00:45 -0500 |
| Organization | A noiseless patient Spider |
| Message-ID | <o8bb9t$nu2$1@dont-email.me> (permalink) |
| References | (9 earlier) <o87v36$pph$1@dont-email.me> <egpfp7Fel2lU1@mid.individual.net> <o8826j$6fq$1@dont-email.me> <fi8faclfpk5tpnvt44abh2n351dn99nq44@4ax.com> <tj9fac5pkfmi8cr3tousj1rdmo1er6dtd5@4ax.com> |
On 2/17/2017 8:56 PM, John Larkin wrote: > On Fri, 17 Feb 2017 20:27:45 -0500, krw@notreal.com wrote: > >> On Fri, 17 Feb 2017 18:51:29 -0500, rickman <gnuarm@gmail.com> wrote: >> >>> On 2/17/2017 6:37 PM, Joerg wrote: >>>> On 2017-02-17 14:58, rickman wrote: >>>>> On 2/17/2017 5:38 PM, Joerg wrote: >>>>>> On 2017-02-17 14:16, rickman wrote: >>>>>>> On 2/17/2017 5:05 PM, Joerg 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. >>>>>>> >>>>>>> Define "outside world". Do you mean off board? >>>>>>> >>>>>> >>>>>> Yes, or via a noisy area on the board. Also if slow on-board sensors are >>>>>> involved. >>>>> >>>>> That's why I said... >>>>> >>>>> "most digital engineers work to eliminate >>>>> noise and to have proper clocks without noise on the transition edge. " >>>>> >>>> >>>> .... and then overlook that there can be external influences into boards >>>> and system. Such as EMI, magnetic fields or even weird stuff like that >>>> inexplicable double-pulse whenever somebody uses the freight elevator. >>>> But who am I to complain, this stuff brought me plenty of assignments. >>> >>> I'm not overlooking anything. All that is part of the engineer's job. >>> A Schmitt trigger would be a panacea for none of the above. A Schmitt >>> trigger is useful when appropriate, but the original post was about >>> "every SPI" having Schmitt inputs. First, its only useful on edges and >>> so only the clock. Secondly it is not something you can't add >>> externally. I don't know why a chip designer wouldn't include a Schmitt >>> trigger on clock inputs, but I'm not going to second guess them on >>> something as unimportant as this. I'd much prefer they got the circuit >>> design right. >> >> I can't imagine why a Schmitt trigger should be on every clock, SPI in >> particular. The designer should be able to design the board so there >> isn't crap on the clock edges. I don't see the big deal with SPI. >> I've had a lot more trouble with I2C than I have with SPI but I've >> abused it more, too. > > If you come out of a wimpy ARM pin, and run the SPI clock all over a > multilayer board, to multiple targets, the edges will get slow. Slow > edges splayed all around a board are very noise sensitive. Schmitts > fix that, and let you run the SPI clock at a frequency that's > compatible with all that capacitive loading, traces and chips > combined. Schmitt trigger inputs don't "fix" noise. They may mask the problem if it is not so severe. I don't recall ever seeing an edge so degraded by loading that it started having noise problems. Your problem isn't the lack of Schmitt trigger inputs, your problem is excessive loading on a clock line. Add some clock buffers. > Noise on \CS is well avoided, too. Only if CS is an edge triggered signal. Fix your noise problem and you don't need to worry about the lack of built in Schmitt trigger inputs. -- Rick C
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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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