Cold spray, where do you buy?
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From: John Larkin on 11 Apr 2010 13:41 On Sun, 11 Apr 2010 09:22:49 -0700, Joerg <invalid(a)invalid.invalid> wrote: >whygee wrote: >> 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 ? >> > >Sure, but then you have to measure frequency and, for some applications, >you've just created another EMI nightmare. The system already has a clock, and the ring oscillator/counter are buried somewhere deep inside the FPGA fabric. The incremental EMI will be trivial. A simple diode path is all >that's needed. Plus an external ADC, which may or may not be available In just about any chip design review I suggest this >because the feature is essentially free. What follows is usually a >moment of silence followed by someone saying "Oh yeah, let's do that". The best solution would be to include an SPI temperature sensor, available internally and externally. Core voltage *can* be tweaked to offset prop delay TC. That's actually done in some ASICS. But most users don't need to flatten prop delay over temperature; they only need to be assured that their logic will work worst-case. John
From: John Larkin on 11 Apr 2010 13:54 On Sun, 11 Apr 2010 09:26:58 -0700, Joerg <invalid(a)invalid.invalid> wrote: >John Larkin wrote: >> On Sun, 11 Apr 2010 08:46:02 -0700 (PDT), MooseFET >> <kensmith(a)rahul.net> wrote: >> >>> On Apr 8, 2:19 pm, Joerg <inva...(a)invalid.invalid> wrote: >>>> Gents, >>>> >>>> Running low on cold spray. Digikey doesn't sell it anymore, maybe >>>> because of shipment safety rules and regs. RadioShack is also dry. >>>> >>>> Where can one get that stuff locally? >>> Slightly off topic but interesting if you are doing a lot of local >>> cooling: >>> http://www.exair.com/en-US/Primary%20Navigation/Products/Vortex%20Tubes%20and%20Spot%20Cooling/Pages/Vortex%20Tubes%20and%20Spot%20Cooling%20Home.aspx >>> >>> >> >> We tried a vortex tube and were disappointed. Not much cooling and >> *very* noisy. >> > >Would it be enough to disgnose thermal effects in a chip? Then we'd just >have to wait until Harborfreight has it :-) It made cool air, but nothing as cold as freeze spray. We ran a hose from our compressor upstairs to the lab, so maybe we didn't have enough air. But it was already unbearably noisy. Running a bigger hose, and putting the vortex tube in a padded box, was too much work compared to ordering a case of freeze spray. John
From: Frank Buss on 11 Apr 2010 13:57 John Larkin wrote: > On Sun, 11 Apr 2010 09:22:49 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> A simple diode path is all >>that's needed. > > Plus an external ADC, which may or may not be available You can use digital inputs to convert analog values. More interesting ideas are using LVDS inputs. This is an example from Lattice Semiconductor: http://www.latticesemi.com/documents/WP-Creating_An_ADC_Using_FPGA_Resources.pdf but I think this would be possible with Xilinx and Altera parts as well. -- Frank Buss, fb(a)frank-buss.de http://www.frank-buss.de, http://www.it4-systems.de
From: John Larkin on 11 Apr 2010 14:47 On Sun, 11 Apr 2010 19:57:15 +0200, Frank Buss <fb(a)frank-buss.de> wrote: >John Larkin wrote: > >> On Sun, 11 Apr 2010 09:22:49 -0700, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> A simple diode path is all >>>that's needed. >> >> Plus an external ADC, which may or may not be available > >You can use digital inputs to convert analog values. More interesting ideas >are using LVDS inputs. This is an example from Lattice Semiconductor: > >http://www.latticesemi.com/documents/WP-Creating_An_ADC_Using_FPGA_Resources.pdf > >but I think this would be possible with Xilinx and Altera parts as well. Cool. Fig 4 is a sort of delta-sigma ADC. It's not widely advertised, but most LVDS receivers are pretty good, and very fast, rail-to-rail comparators. One could also do a single-slope multichannel ADC with one linear ramp and a bunch of LVDS inputs, each with a counter or a latch driven by a counter. John
From: langwadt on 11 Apr 2010 14:51
On 11 Apr., 20:47, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Sun, 11 Apr 2010 19:57:15 +0200, Frank Buss <f...(a)frank-buss.de> > wrote: > > > > >John Larkin wrote: > > >> On Sun, 11 Apr 2010 09:22:49 -0700, Joerg <inva...(a)invalid.invalid> > >> wrote: > > >>> A simple diode path is all > >>>that's needed. > > >> Plus an external ADC, which may or may not be available > > >You can use digital inputs to convert analog values. More interesting ideas > >are using LVDS inputs. This is an example from Lattice Semiconductor: > > >http://www.latticesemi.com/documents/WP-Creating_An_ADC_Using_FPGA_Re... > > >but I think this would be possible with Xilinx and Altera parts as well. > > Cool. Fig 4 is a sort of delta-sigma ADC. It's not widely advertised, > but most LVDS receivers are pretty good, and very fast, rail-to-rail > comparators. > > One could also do a single-slope multichannel ADC with one linear ramp > and a bunch of LVDS inputs, each with a counter or a latch driven by a > counter. > > John I seem to remember that some (xilinx?) guy has a patent on using the ldvs input as a comparator for an ADC -Lasse |