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From: John Larkin on 10 Apr 2010 15:47 On Sat, 10 Apr 2010 12:36:08 -0700, Joerg <invalid(a)invalid.invalid> wrote: >John Larkin wrote: >> On Sat, 10 Apr 2010 11:23:48 -0700, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> John Larkin wrote: >>>> On Sat, 10 Apr 2010 10:53:32 -0700, RST Engineering >>>> <jweir43(a)gmail.com> wrote: >>>> >>>>> On Sat, 10 Apr 2010 10:08:13 -0700, John Larkin >>>>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>>> >>>>> >>>>>> I use freeze spray and heat guns for FPGA timing verification. Prop >>>>>> delays are a radical function of temperature. >>> >>> I prefer the heat gun. Less of a stench :-) >> >> >> You must be buying cheap French freeze spray. "Winter in Paris" maybe. >> > >Now if they'd put a "Harley Davidson" aftershave scent in it, that would >be ok. > >> >>>>> I believe you, John, but being an analog kind of guy I can't reason >>>>> why propagation delays are a radical function of temperature. Can you >>>>> explain? >>>>> >>>>> Jim >>>> Well, that's CMOS. >>>> >>>> I don't know the physics, but mosfet channel resistance and >>>> interconnect resistance have pretty strong positive TCs, so things get >>>> slow when they get hot. A reasonable path in and out of a Xilinx FPGA >>>> might take 5 ns, and its TC might be in the ballpark of 5 or 10 ps/K. >>> >>> That's roughly what I had on CMOS switches as well. So I servoed them >>> (somewhat), using another one on the same die in a DC loop. Worked quite >>> well but it didn't have to be perfect in my cases. >>> >>> [...] >> >> >> We generally use an LM45 or an LM71 temp sensor and do the tc comps in >> software, occasionally analog in hardware. Reducing prop delay tc by >> maybe 5:1 is reasonable without temperature cycling production units. >> > >I always wondered why FPGA don't have a feature to program an on-chip >temperature sensor onto one pin, or at least a diode path. uC often have >that, for example the MSP430 series. Yeah, that would be great. It could also be SPI or just a register you could read. John
From: langwadt on 10 Apr 2010 15:54 On 10 Apr., 21:47, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Sat, 10 Apr 2010 12:36:08 -0700, Joerg <inva...(a)invalid.invalid> > wrote: > > > > >John Larkin wrote: > >> On Sat, 10 Apr 2010 11:23:48 -0700, Joerg <inva...(a)invalid.invalid> > >> wrote: > > >>> John Larkin wrote: > >>>> On Sat, 10 Apr 2010 10:53:32 -0700, RST Engineering > >>>> <jwei...(a)gmail.com> wrote: > > >>>>> On Sat, 10 Apr 2010 10:08:13 -0700, John Larkin > >>>>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > > >>>>>> I use freeze spray and heat guns for FPGA timing verification. Prop > >>>>>> delays are a radical function of temperature. > > >>> I prefer the heat gun. Less of a stench :-) > > >> You must be buying cheap French freeze spray. "Winter in Paris" maybe. > > >Now if they'd put a "Harley Davidson" aftershave scent in it, that would > >be ok. > > >>>>> I believe you, John, but being an analog kind of guy I can't reason > >>>>> why propagation delays are a radical function of temperature. Can you > >>>>> explain? > > >>>>> Jim > >>>> Well, that's CMOS. > > >>>> I don't know the physics, but mosfet channel resistance and > >>>> interconnect resistance have pretty strong positive TCs, so things get > >>>> slow when they get hot. A reasonable path in and out of a Xilinx FPGA > >>>> might take 5 ns, and its TC might be in the ballpark of 5 or 10 ps/K.. > > >>> That's roughly what I had on CMOS switches as well. So I servoed them > >>> (somewhat), using another one on the same die in a DC loop. Worked quite > >>> well but it didn't have to be perfect in my cases. > > >>> [...] > > >> We generally use an LM45 or an LM71 temp sensor and do the tc comps in > >> software, occasionally analog in hardware. Reducing prop delay tc by > >> maybe 5:1 is reasonable without temperature cycling production units. > > >I always wondered why FPGA don't have a feature to program an on-chip > >temperature sensor onto one pin, or at least a diode path. uC often have > >that, for example the MSP430 series. > > Yeah, that would be great. It could also be SPI or just a register you > could read. > > John looks like virtex5 has that and more: http://www.xilinx.com/support/documentation/user_guides/ug192.pdf
From: krw on 10 Apr 2010 19:09 On Sat, 10 Apr 2010 11:16:53 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Sat, 10 Apr 2010 10:53:32 -0700, RST Engineering ><jweir43(a)gmail.com> wrote: > >>On Sat, 10 Apr 2010 10:08:13 -0700, John Larkin >><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> >>>I use freeze spray and heat guns for FPGA timing verification. Prop >>>delays are a radical function of temperature. >> >>I believe you, John, but being an analog kind of guy I can't reason >>why propagation delays are a radical function of temperature. Can you >>explain? >> >>Jim > >Well, that's CMOS. > >I don't know the physics, but mosfet channel resistance and >interconnect resistance have pretty strong positive TCs, so things get >slow when they get hot. A reasonable path in and out of a Xilinx FPGA >might take 5 ns, and its TC might be in the ballpark of 5 or 10 ps/K. >In our delay generators, we generally have to compensate. Gluing a >heat sink to the FPGA helps, and adds an air of mystery too. > >One of my guys is going to engineering school part-time, and as a >project he measured the prop delay TCs of some Xilinx chips in various >situations. I'll post it if I can find it. > >As I recall, TTL also slows down with temperature. It should speed up. >ECL hardly changes at all, under 1 ps/K for a typical EclipsLite gate. ECL also has a positive speed/temperature coefficient. We used insulators under the Thermal Conduction Modue pistons of low power chips to equalize the junction temperature of all chips at 85C.
From: whygee on 11 Apr 2010 05:42 Joerg wrote: > I always wondered why FPGA don't have a feature to program an on-chip > temperature sensor onto one pin, or at least a diode path. uC often have > that, for example the MSP430 series. The Actel Fusion family can do pretty temperature measurements, but they are ... a bit expensive. Maybe a ring oscillator in the FPGA fabric, with the output frequency compared to a stable external oscillator, can help ? yg -- http://ygdes.com / http://yasep.org
From: Spehro Pefhany on 11 Apr 2010 11:28
On Fri, 09 Apr 2010 09:58:41 -0700, the renowned John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >We use Chemtronics Freez-It and some sort of duster spray. Neither >tastes or smells bad. Maybe some people are putting nasties in theirs >to discourage kids from snorting the stuff. > >John Exactly right. The Perfect Data duster I have uses the same propellant, but doesn't have the nasty. It does leave a quite noticable residue, so it might affect analog circuits. http://www.3m.com/us/office/advisory/3Mdustremoverfaqs.html Bittering Agent What is Bittering Agent? Bittering agent is an additive that leaves a bitter taste upon contact with one�s mouth. 3M added a bittering agent to 3M Dust Remover to help discourage inhalation abuse. The bittering agent itself is generally not harmful and is used in household cleaners and shampoos to deter intentional or accidental ingestion of these products. However� people with asthma or sensitivity to odors or taste may react to the bittering agent� and therefore� may want to avoid using 3M Dust Remover. Abuse by inhaling 3M Dust Remover may cause instant death or injury. How do I get the bittering agent bad taste out of my mouth? Dried liquid spray may leave a bitter residue� resulting in a bad taste if transferred to the mouth. If you eat a piece of chocolate� or drink or eat some dairy products� it may help the taste to go away. How do I get the bittering agent off my fingers? Wash affected area with soap and water. If irritation occurs� get medical attention. ALWAYS hold container upright to avoid spraying liquid. Dried liquid spray may leave a bitter residue. How do I get the bittering agent off my keyboard? To remove dried spray� wipe with a cloth dampened with a 50/50 mix of isopropyl alcohol and water. ALWAYS hold container upright to avoid spraying liquid. Dried liquid spray may leave a bitter residue. Can I buy 3M Dust Remover that does not contain the bittering agent? No. All 3M Dust Remover currently sold contains a bittering agent. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff(a)interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com |