On Fri, 05 Dec 2014 01:58:52 -0800, josephkk wrote:> On Wed, 03 Dec 2014 18:01:04 -0800, John Larkin > <jlarkin@highlandtechnology.com> wrote: > > >>We have two 8-channel waveform generators that were shipped 4 months >>ago, and came back because the customer ordered too many or something. >>We routinely test anything that comes back, before returning them or >>returning to stock. >> >>What's interesting is that all 16 channels have a negative DC offset. >>Each channel is a diff-current-output cmos DAC, an opamp diffamp, a >>passive LC filter, and an output amp; the opamps are fast bipolars. We >>apply a software cal factor to the DAC data (saved in a cal table) to >>get the offsets way below 1 mV when we ship. After 4 months, we're >>seeing offsets from -5 to -10 mV. These are not actual failures, but I >>don't like or understand the trend. >> >>We'll be doing some tests to try to isolate the drift to dac, diffamp, >>or output amp. I figure we could measure things on one board, bake to >>accelerate aging, and re-measure. >> >>My general question, to people who understand semi physics: what are the >>physical mechanisms that could make the DAC, or the opamps, have this >>ensemble negative drift vs time? >> >>Parts are DAC2904, LMH6642, and THS3062. >> >>THS3062 is known to be buggy, latching up if slewed hard at high >>frequency, but this board doesn't stress them up there. > > Please remember that drift tends to have a curve like 1-e^kt curves with > k being like 1/month to 1/year values.Analog Devices claims that intrinsic aging effects in the absence of stress (and presumably contamination) obeys a "drunkard's walk" behavior: <http://www.analog.com/en/digital-to-analog-converters/da-converters/ products/raq_jbryant_long_term_stability_of_precision_iss15/resources/ faq.html?display=popup> also a discussion of mechanical stress and cal: <http://www.analog.com/en/precision-op-amps/products/ RAQ_JB_Stress_Is_Bad_for_you_and_AnalogICs_Issue35/resources/faq.html? display=popup>
semiconductor drift
Started by ●December 3, 2014
Reply by ●December 5, 20142014-12-05
Reply by ●December 5, 20142014-12-05
On Fri, 5 Dec 2014 05:00:06 -0800 (PST), Klaus Kragelund <klauskvik@hotmail.com> wrote:>On Friday, December 5, 2014 1:34:21 AM UTC+1, John Larkin wrote: >> On Thu, 4 Dec 2014 15:09:23 -0600, "Tim Williams" >> <tiwill@seventransistorlabs.com> wrote: >> >> >You're trying to ask, >> > >> >"My car pulls slightly to the right on the highway. To people who >> >understand automobiles: what are the physical mechanisms that could do >> >that?" >> > >> >You already very well know, there are a hundred things in either case >> >which could individually explain it, all of which depend utterly on the >> >internal construction of the system. The design notes of which are >> >unspecified and unavailable, so it's useless to even ask. >> > >> >And more than likely, it's not even the fault of the system at all, but >> >"did you notice your left arm is shorter than your right?", or, "no >> >wonder, your right tires are balled". Like the resistors others have >> >mentioned. >> > >> >Come on John, you should know better than to ask such silly questions to a >> >public group. If you just want to give fodder to JT, why don't you e-mail >> >him and save us the trouble. >> > >> >Tim >> >> As I stated, I am interested in the mechanisms that can make analog >> ICs drift. The only silly thing about my question was asking it here, >> where nobody seems to know much about semiconductor physics. >> > >Some information on the subject: > >http://www.ti.com/lit/an/sloa059/sloa059.pdf > >Have you tried to do thermal cycling on a part, with a lot of cycles per day, that should accelerate the drift, since on of the stated reasons for drift in VOS is the thermal expansion of the die > >Cheers > >KlausThat's cool. Table 1 shows typical bipolar opamp drift of 5 nV per month for bipolar opamps. Even if our drift is in our first opamp, it's a lot more than that... more like 100 uV/month. Later on, they say "The offset drift over time is low for bipolar input stages, and typically ranges from a few �V/month down to a few nV/month. This parameter is dependent upon the heat and mechanical stress induced on the op amp by the fabrication of the circuit board and the application circuit." Yeah, die stress could be another mechanism. -- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●December 5, 20142014-12-05
On Fri, 05 Dec 2014 08:36:56 -0800, John Larkin <jlarkin@highlandtechnology.com> wrote:>On Fri, 5 Dec 2014 05:00:06 -0800 (PST), Klaus Kragelund ><klauskvik@hotmail.com> wrote: > >>On Friday, December 5, 2014 1:34:21 AM UTC+1, John Larkin wrote: >>> On Thu, 4 Dec 2014 15:09:23 -0600, "Tim Williams" >>> <tiwill@seventransistorlabs.com> wrote: >>> >>> >You're trying to ask, >>> > >>> >"My car pulls slightly to the right on the highway. To people who >>> >understand automobiles: what are the physical mechanisms that could do >>> >that?" >>> > >>> >You already very well know, there are a hundred things in either case >>> >which could individually explain it, all of which depend utterly on the >>> >internal construction of the system. The design notes of which are >>> >unspecified and unavailable, so it's useless to even ask. >>> > >>> >And more than likely, it's not even the fault of the system at all, but >>> >"did you notice your left arm is shorter than your right?", or, "no >>> >wonder, your right tires are balled". Like the resistors others have >>> >mentioned. >>> > >>> >Come on John, you should know better than to ask such silly questions to a >>> >public group. If you just want to give fodder to JT, why don't you e-mail >>> >him and save us the trouble. >>> > >>> >Tim >>> >>> As I stated, I am interested in the mechanisms that can make analog >>> ICs drift. The only silly thing about my question was asking it here, >>> where nobody seems to know much about semiconductor physics. >>> >> >>Some information on the subject: >> >>http://www.ti.com/lit/an/sloa059/sloa059.pdf >> >>Have you tried to do thermal cycling on a part, with a lot of cycles per day, that should accelerate the drift, since on of the stated reasons for drift in VOS is the thermal expansion of the die >> >>Cheers >> >>Klaus > >That's cool. Table 1 shows typical bipolar opamp drift of 5 nV per >month for bipolar opamps. Even if our drift is in our first opamp, >it's a lot more than that... more like 100 uV/month. > >Later on, they say > >"The offset drift over time is low for bipolar input stages, and >typically ranges from a few �V/month down to a few nV/month. This >parameter is dependent upon the heat and mechanical stress induced on >the op amp by the fabrication of the circuit board and the application >circuit." > > >Yeah, die stress could be another mechanism.How about offset CURRENT drift? ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●December 5, 20142014-12-05
On Fri, 05 Dec 2014 08:36:56 -0800, the renowned John Larkin <jlarkin@highlandtechnology.com> wrote:> > >That's cool. Table 1 shows typical bipolar opamp drift of 5 nV per >month for bipolar opamps. Even if our drift is in our first opamp, >it's a lot more than that... more like 100 uV/month. > >Later on, they say > >"The offset drift over time is low for bipolar input stages, and >typically ranges from a few �V/month down to a few nV/month. This >parameter is dependent upon the heat and mechanical stress induced on >the op amp by the fabrication of the circuit board and the application >circuit." > > >Yeah, die stress could be another mechanism.I've not seen undamaged bipolar parts (even really, really crappy ones made with crummy processes) drift anything like that much. And I would have seen it, since we went through many iterations of making really inexpensive thermocouple instrumentation over many, many years. CMOS, yes, it can go wacky, because of ionic contamination, I'm told. Heck our first products were using an LM709 with custom individual hand-wire-wound resistors for calibration (including offset voltage). The customer couldn't tweak those back into calibration even if they wanted to. Interestingly we recently bought an ADC box from Data Translation for an experiment and they'd routed out around the voltage reference chips, presumably because of some kind of die stress issue- earlier revisions didn't have it. See page 3/8 here: http://tinyurl.com/mzcu8wc Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Reply by ●December 5, 20142014-12-05
On Fri, 05 Dec 2014 15:35:41 -0500, Spehro Pefhany wrote:> On Fri, 05 Dec 2014 08:36:56 -0800, the renowned John Larkin > <jlarkin@highlandtechnology.com> wrote: > > >> >>That's cool. Table 1 shows typical bipolar opamp drift of 5 nV per month >>for bipolar opamps. Even if our drift is in our first opamp, it's a lot >>more than that... more like 100 uV/month. >> >>Later on, they say >> >>"The offset drift over time is low for bipolar input stages, and >>typically ranges from a few µV/month down to a few nV/month. This >>parameter is dependent upon the heat and mechanical stress induced on >>the op amp by the fabrication of the circuit board and the application >>circuit." >> >> >>Yeah, die stress could be another mechanism. > > I've not seen undamaged bipolar parts (even really, really crappy ones > made with crummy processes) drift anything like that much. And I would > have seen it, since we went through many iterations of making really > inexpensive thermocouple instrumentation over many, many years. CMOS, > yes, it can go wacky, because of ionic contamination, I'm told. > > Heck our first products were using an LM709 with custom individual > hand-wire-wound resistors for calibration (including offset voltage). > The customer couldn't tweak those back into calibration even if they > wanted to. > > Interestingly we recently bought an ADC box from Data Translation for an > experiment and they'd routed out around the voltage reference chips, > presumably because of some kind of die stress issue- earlier revisions > didn't have it. See page 3/8 here: http://tinyurl.com/mzcu8wc"The link you're trying to access can't be used to share files. Please ask the file owner to provide you with a shared link instead. Contact Box Support if you need help." -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
Reply by ●December 5, 20142014-12-05
John Larkin wrote:> On Fri, 5 Dec 2014 05:00:06 -0800 (PST), Klaus Kragelund > <klauskvik@hotmail.com> wrote: > >>On Friday, December 5, 2014 1:34:21 AM UTC+1, John Larkin wrote: >>> On Thu, 4 Dec 2014 15:09:23 -0600, "Tim Williams" >>> <tiwill@seventransistorlabs.com> wrote: >>> >>> >You're trying to ask, >>> > >>> >"My car pulls slightly to the right on the highway. To people who >>> >understand automobiles: what are the physical mechanisms that could do >>> >that?" >>> > >>> >You already very well know, there are a hundred things in either case >>> >which could individually explain it, all of which depend utterly on the >>> >internal construction of the system. The design notes of which are >>> >unspecified and unavailable, so it's useless to even ask. >>> > >>> >And more than likely, it's not even the fault of the system at all, but >>> >"did you notice your left arm is shorter than your right?", or, "no >>> >wonder, your right tires are balled". Like the resistors others have >>> >mentioned. >>> > >>> >Come on John, you should know better than to ask such silly questions >>> >to a >>> >public group. If you just want to give fodder to JT, why don't you >>> >e-mail him and save us the trouble. >>> > >>> >Tim >>> >>> As I stated, I am interested in the mechanisms that can make analog >>> ICs drift. The only silly thing about my question was asking it here, >>> where nobody seems to know much about semiconductor physics. >>> >> >>Some information on the subject: >> >>http://www.ti.com/lit/an/sloa059/sloa059.pdf >> >>Have you tried to do thermal cycling on a part, with a lot of cycles per >>day, that should accelerate the drift, since on of the stated reasons for >>drift in VOS is the thermal expansion of the die >> >>Cheers >> >>Klaus > > That's cool. Table 1 shows typical bipolar opamp drift of 5 nV per > month for bipolar opamps. Even if our drift is in our first opamp, > it's a lot more than that... more like 100 uV/month. > > Later on, they say > > "The offset drift over time is low for bipolar input stages, and > typically ranges from a few µV/month down to a few nV/month. This > parameter is dependent upon the heat and mechanical stress induced on > the op amp by the fabrication of the circuit board and the application > circuit." > > > Yeah, die stress could be another mechanism. > >I forgot about die stress. You mentioned low impedance, so I don't think this is a cause, but I should point out that you can stress the ESD protection device and cause a current leak, but otherwise have an operational part. The problem I see with your question is you are calling the problem drift, but you haven't been able to observe the offset over continuous time. What you call drift could be a shift, i.e. something that happened suddenly. This is a customer return. You have to trust the customer didn't use the unit.
Reply by ●December 5, 20142014-12-05
Reply by ●December 6, 20142014-12-06
Den l=F8rdag den 6. december 2014 03.11.10 UTC+1 skrev miso:> http://www.analog.com/static/imported-files/rarely_asked_questions/RAQ_an=alogICs.pdf http://youtu.be/UCXCLR3xq8U?t=3D2m12s -Lasse
Reply by ●December 6, 20142014-12-06
In article <o7v18adrt0bu9en5a772dtbb9798s9ooqv@4ax.com>, John Larkin <jlarkin@highlandtechnology.com> wrote:> On Thu, 4 Dec 2014 15:09:23 -0600, "Tim Williams" > <tiwill@seventransistorlabs.com> wrote: > > >You're trying to ask, > > > >"My car pulls slightly to the right on the highway. To people who > >understand automobiles: what are the physical mechanisms that could do > >that?" > > > >You already very well know, there are a hundred things in either case > >which could individually explain it, all of which depend utterly on the > >internal construction of the system. The design notes of which are > >unspecified and unavailable, so it's useless to even ask. > > > >And more than likely, it's not even the fault of the system at all, but > >"did you notice your left arm is shorter than your right?", or, "no > >wonder, your right tires are balled". Like the resistors others have > >mentioned. > > > >Come on John, you should know better than to ask such silly questions to a > >public group. If you just want to give fodder to JT, why don't you e-mail > >him and save us the trouble. > > > >Tim > > As I stated, I am interested in the mechanisms that can make analog > ICs drift. The only silly thing about my question was asking it here, > where nobody seems to know much about semiconductor physics.Look into ARGT (Accelerated Reliability Growth Testing), which is heat-soak plus thermal cycling to wear things out faster than will be experienced in the field. The artifice is to set test conditions so they accelerate aging as much as possible, and yet are not so sever as to directly damage the item under test. The ARGT literature goes deep into the various aging (and thus drift) mechanisms. Google will yield many hits. Joe Gwinn
Reply by ●December 6, 20142014-12-06
On a sunny day (Sat, 6 Dec 2014 07:41:34 -0800 (PST)) it happened Lasse Langwadt Christensen <langwadt@fonz.dk> wrote in <08f0d3fc-7d38-4e91-91af-b7340d272faf@googlegroups.com>:>Den l�rdag den 6. december 2014 03.11.10 UTC+1 skrev miso: >> http://www.analog.com/static/imported-files/rarely_asked_questions/RAQ_an= >alogICs.pdf > >http://youtu.be/UCXCLR3xq8U?t=2m12s > >-LasseI think that is only value of SMDs changing. The width of the serial pulses does not change at all, and that comes from the micro's clock. The guy sounds like talking rubbish. Could not listen to it all.
